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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Phillip McVea on April 14, 2014, 01:55:46 pm

Title: 15in vs 12in
Post by: Phillip McVea on April 14, 2014, 01:55:46 pm
summarized/bolded for the impatient people.
I was recently browsing selections for pole-mount/"point-source" loudspeakers, coaxial loudspeakers, "fixed curvature line array" loudspeakers, variable curvature line array loudspeakers, and also home audio loudspeakers.

Long story short i noticed that alot of manufacturers usually include the following variants in their speaker lines: 2-way 1/1.75in high & 12in low, 2-way w/ 1/1.75in high & 15in low, and 3-way w/ 1/1.75in high, 6.5in mid & 15in low.
These are all speakers that are made (primarily) for live sound reinforcement. By that i mean they're made to be loud as opposed to accurate. Most have peak amplifier power ratings of 1000-2000 watts (w/ mains input @ 120v). about 4/5 of the speakers i looked at had the amplifier built in to the actual cabinet housing.

While i understand many of the company's decisions to produce a 3-way model for better dispersion control (and the other benefits of a 3-way design), but i'm very weary of the 2-way models that use 15" drivers, often the same ones they put in the 3-way models. It concerns me because within a 2-way speaker, the woofer must account for some of the mid range frequencies, the same frequencies that would otherwise be created by a smaller 6.5in driver that could better reproduce the wavelengths of mid-range frequencies. I like the idea of using a 12in driver (at the largest) in a 2-way speaker because, while it is smaller, it could better create the entire sound range that doesn't end up sounding worse.

For example, i've noticed that in a 2-way system with a 15in LF driver, whenever someone with deeper voice speaks at the higher point of their voice, it sounds like there's something that's "holding" the sound back, almost like a muddy sound. As if someone taped a few layers of thin fabric over my ears when they speak like that. But as they progress into the deeper octaves of their voice, it sounds deeper and more direct i guess you could say.
it's kind of difficult to describe the difference without something happening right in front of me, but the point is if they were to repeat the same thing in a 3-way system with a 6.5in MF & 15in LF driver, their voice sounds CONSISTENTLY more "direct", clearer, even throughout the lower sounds. I find that even the mid range has more "punch" to it, like on kick-drums, you can feel the beginning of the note have more impact & spread from the speaker. And in bass music, those long notes that dip into the sub-bass region then fade up into a higher and higher sound. You can really feel the notes "carry through" and have a fuller sound, even as they carry over from sub-bass speakers to the full-range speakers.

While i'm far from an expert in sound reinforcement (and writing obviously), my personal theory is that this is because of the amount of air the driver is moving, and in relation to how fast/how often & loud it's trying to make it. Meaning 15in drivers are best for creating bass frequencies and ONLY bass frequencies, because the size of the wavelength is appropriate to the thing that's trying to create it. Just like 21in drivers are best for creating sub-bass frequencies and ONLY sub-bass frequencies. And just like 6.5in drivers are best for creating mid-range frequencies. Obviously the EXACT definitions of high/mid/bass range are all subjective to the actual speaker and various other factors (too many to list out).

BUT the point remains, what is the best balance of both loud AND clear, a 2-way system with 12in driver or a 2-way system with a 15in driver?
Title: Re: 15in vs 12in
Post by: TJ (Tom) Cornish on April 14, 2014, 02:01:18 pm

BUT the point remains, what is the best balance of both loud AND clear, a 2-way system with 12in driver or a 2-way system with a 15in driver?
That's a big, fat "it depends".  "Loud", "Clear", and the speaker's ability to be clear at any particular loudness are more cost and design dependent, rather than specific driver configuration.

A 3-way system is not necessarily better than a 2-way system - with a simple speaker with drivers lined up (not all firing in a horn), there are time alignment issues and crossover issues that are worse with more crossover points.
Title: Re: 15in vs 12in
Post by: Taylor Hall on April 14, 2014, 02:03:58 pm
TJ said it more eloquently that I could. Lots of variables to take into account, and not just driver/enclosure design, but also the venue.
Title: Re: 15in vs 12in
Post by: g'bye, Dick Rees on April 14, 2014, 02:07:56 pm
summarized/bolded for the impatient people.
I was recently browsing selections for pole-mount/"point-source" loudspeakers, coaxial loudspeakers, "fixed curvature line array" loudspeakers, variable curvature line array loudspeakers, and also home audio loudspeakers.

Long story short i noticed that alot of manufacturers usually include the following variants in their speaker lines: 2-way 1/1.75in high & 12in low, 2-way w/ 1/1.75in high & 15in low, and 3-way w/ 1/1.75in high, 6.5in mid & 15in low.
These are all speakers that are made (primarily) for live sound reinforcement. By that i mean they're made to be loud as opposed to accurate. Most have peak amplifier power ratings of 1000-2000 watts (w/ mains input @ 120v). about 4/5 of the speakers i looked at had the amplifier built in to the actual cabinet housing.

While i understand many of the company's decisions to produce a 3-way model for better dispersion control (and the other benefits of a 3-way design), but i'm very weary of the 2-way models that use 15" drivers, often the same ones they put in the 3-way models. It concerns me because within a 2-way speaker, the woofer must account for some of the mid range frequencies, the same frequencies that would otherwise be created by a smaller 6.5in driver that could better reproduce the wavelengths of mid-range frequencies. I like the idea of using a 12in driver (at the largest) in a 2-way speaker because, while it is smaller, it could better create the entire sound range that doesn't end up sounding worse.

For example, i've noticed that in a 2-way system with a 15in LF driver, whenever someone with deeper voice speaks at the higher point of their voice, it sounds like there's something that's "holding" the sound back, almost like a muddy sound. As if someone taped a few layers of thin fabric over my ears when they speak like that. But as they progress into the deeper octaves of their voice, it sounds deeper and more direct i guess you could say.
it's kind of difficult to describe the difference without something happening right in front of me, but the point is if they were to repeat the same thing in a 3-way system with a 6.5in MF & 15in LF driver, their voice sounds CONSISTENTLY more "direct", clearer, even throughout the lower sounds. I find that even the mid range has more "punch" to it, like on kick-drums, you can feel the beginning of the note have more impact & spread from the speaker. And in bass music, those long notes that dip into the sub-bass region then fade up into a higher and higher sound. You can really feel the notes "carry through" and have a fuller sound, even as they carry over from sub-bass speakers to the full-range speakers.

While i'm far from an expert in sound reinforcement (and writing obviously), my personal theory is that this is because of the amount of air the driver is moving, and in relation to how fast/how often & loud it's trying to make it. Meaning 15in drivers are best for creating bass frequencies and ONLY bass frequencies, because the size of the wavelength is appropriate to the thing that's trying to create it. Just like 21in drivers are best for creating sub-bass frequencies and ONLY sub-bass frequencies. And just like 6.5in drivers are best for creating mid-range frequencies. Obviously the EXACT definitions of high/mid/bass range are all subjective to the actual speaker and various other factors (too many to list out).

BUT the point remains, what is the best balance of both loud AND clear, a 2-way system with 12in driver or a 2-way system with a 15in driver?

Interesting theories.  Why don't you test them out and publish the results.  I'm sure there would be some interest...
Title: Re: 15in vs 12in
Post by: Phillip McVea on April 14, 2014, 04:24:38 pm
Interesting theories.  Why don't you test them out and publish the results.  I'm sure there would be some interest...

I'm sure i don't have all the skills/resources to make all the fancy graphs and charts i see on this website all the time. I just noticed an observation, and wanted to see how a wider audience would react to it. I was trying to make the post as subjective and about the speakers as possible, as it seems like all the other factors (processing gear, environment & scenario, content, wear & tear/fatigue, etc etc etc etc) are constantly changing.

When i actually heard what was described in the first post, the situation was just me & a few friends testing out speakers in his driveway. All the subwoofers were sitting on top of a metal frame table about 3.5-4ft high with a wood surface(just like a generic warehouse shelf idk how to describe it) The full-range speakers were all resting directly on top of their respective sub cabinet, if not then directly on the table.

For the most part we were just taking turns mixing on some "Traktor" things, it had 2 audio players on the sides and a 4 channel mixer in the middle. We were mostly playing trance, house, electro. Most of the songs were displaying 80-120bpm. We started playing more bass tracks after a while, dubstep, drum & bass and a few hip-hop sounds. Before we wrapped everything up we plugged in a laptop & played a few youtube videos to hear/test speech and content that isn't as "complex" as music. Strangely enough, it was at this point was when i noticed the differences.

From the mixer (had to use an RCA to XLR converter plug thing) the signal line went to a "active speaker management" box, I was told it's a dbx driverack model. From there was a ART CX310 crossover, outputting directly to 2(left & right) full range speakers & depending on the speaker we were using at that moment in time 1 or 2 subwoofers.
We played about 2-3 songs on each speaker (I remember a few of them if it matters), just moving the XLR & IEC cables from each different speaker we wanted to try. I believe all the speakers were on the -10db volume trim.

We used 4 sets of speakers (all kindly volunteered by different people):
Set 1: 2xYamaha DSR 215, 2xYamaha DSR 112, 2xYamaha DSR 118.
Set 2: 2xJBL EON 615 (no sub)
Set 3: 1xQSC KW153 & 1xQSC KW152
Set 4: 2xElectro Voice ELX112P, 1xElectro Voice ELX115P, 2xElectro Voice ELX118P

We also had 2 other speaker pairs without the built-in amplifier from Electro Voice and a company called Gemini. We couldn't use them because the external amplifier would turn on, generate this high pitched static noise for no longer than 5 seconds, make this weird chirping tune then immediately shut off. We never even got the the chance to input a signal to it before it gave out. It was the strangest thing.

I tried to describe the scenario as best as i can, however not a single piece of equipment belonged to me. Next time i'll just take a picture. That seems alot easier.
Title: Re: 15in vs 12in
Post by: TJ (Tom) Cornish on April 14, 2014, 05:25:17 pm
We used 4 sets of speakers (all kindly volunteered by different people):
Set 1: 2xYamaha DSR 215, 2xYamaha DSR 112, 2xYamaha DSR 118.
Set 2: 2xJBL EON 615 (no sub)
Set 3: 1xQSC KW153 & 1xQSC KW152
Set 4: 2xElectro Voice ELX112P, 1xElectro Voice ELX115P, 2xElectro Voice ELX118P
You have a variety of mid-level gear here.  Kudos to you for setting it up, listening, and trying to learn stuff. 

Electronic music is not particularly revealing of fidelity for anything other than sub frequencies.  Acoustic music, vocals, and drums generally have a lot more detail where you can differentiate.

Active speakers generally have some amount of tuning built-in, so generally they sound fairly good with no additional processing.  That being said, speakers at this level can usually be improved and/or customized to the current situation by some external EQ done by a competent person. 

Your workflow doesn't go into great detail, but you say you used an ART CX310 crossover and a drive rack of some kind.  These tools are like sharp knives - in the hands of someone who knows what they are doing, they can help.  In the hands of someone inexperienced, they can cause damage.  For the average user, buying subs and tops from the same series is generally a good idea, and most systems like this are designed so that you plug the line into the sub, and then use a post-crossover output on the sub to feed the mid/high.  Doing this per the manufacturer's design will give good results.  Using an external crossover may be actually worse than using the internal crossover of the powered speaker, as there may be phase and EQ alignment issues that need to be compensated for.

Another potentially relevant thing is speakers that are designed for live sound may be tuned differently than "DJ" speakers.  Live sound speakers are generally flatter, which to someone who is used to smiley-face EQ, may sound dark.

All this is to say that your observations are very instructive and to keep at it, but make sure you understand all the variables before going too far out on a limb making a conclusion.
Title: Re: 15in vs 12in
Post by: Len Zenith Jr on April 14, 2014, 06:12:14 pm
15" drivers start to beam around 1050hz, while 12" drivers a bit higher, around 1350hz, and your 6" driver around 2750hz. Depending on where the speakers cross over to the high frequency horn, this may have been the effect you are describing. Beaming is where the drivers start to become directional, so if you are standing for example 45 degrees off axis from the speaker, everything that the 15" driver reproduces above 1050hz would drop off in level, the more off axis, the greater the effect. I have a set of 2-way speakers at work where the crossover is at 2200hz and uses a 12" woofer; off axis, the hole between 1350hz-2200hz is very prominent. Even on axis, although the frequency response of the direct sound is flat, the reflections off the walls/ceiling, etc from the off axis of the speaker with the hole in the mids gets bounced back with that hole in the mids confusing our ears.

For DJ type sound reinforcement where you will always use subs, the 12" boxes typically have better off axis sound (where most of the audience is anyways). Not because a 15" with appropriate hf horn couldn't be designed, but because usually the 15" version was designed for more low frequency extension (not needed with subs) and the off axis hole in the mids is just a trade off as a larger 2" hf driver with a lower crossover point would drive costs up too much.
Title: Re: 15in vs 12in
Post by: Luke Geis on April 14, 2014, 06:21:21 pm
In theory you are correct in your assumptions of how a particular speaker should be. However this isn't necessarily the truth in all cases. 15" speakers are more of an intermediate all around speaker usually placed in a cabinet that is tuned to get usable sonic range between 40hz ( and lower ) and up to the 20khz area. Your typical 12" is usually sitting around 50-60hz for it's lows. The 15" speaker will work ok without a sub and fill the room with an acceptable level of bass frequencies. The 12", perhaps not as much? So why do many 3 way systems employ a 15" speaker? To get the sonic range. It gets low enough to have sub and is detailed enough to have a higher level of clarity and precision.

This is not to say that a 15" speaker cannot be made to sound as good as a 12" in a similar application though. The 12" speaker should be able to acquire a higher level of detail, but isn't the holdfast rule, or truth. A 3 way system that utilizes a 12" speaker may be found to be wasting resources with no distinct increase in performance? In other words the sonic range and added cost may not justify the slightly better performance? Tough to say really. I don't design speakers, I simply test, work with and employ a lot of different brands and models and study the market for the best tools for the jobs I perform. I have found that just about any speaker can be made to sound ok and that the more work it takes to get a good sound, the less volume you typically will acquire. A good speaker sounds good with little effort and has usable level that exceeds the need. That is really the difference between a $300 dollar speaker and a $1000 dollar speaker in the same catagory. The higher dollar speaker will likely sound better and achieve higher volume levels with little effort.
Title: Re: 15in vs 12in
Post by: Phillip McVea on April 14, 2014, 07:00:27 pm
You have a variety of mid-level gear here.  Kudos to you for setting it up, listening, and trying to learn stuff. 

Electronic music is not particularly revealing of fidelity for anything other than sub frequencies.  Acoustic music, vocals, and drums generally have a lot more detail where you can differentiate.

Active speakers generally have some amount of tuning built-in, so generally they sound fairly good with no additional processing.  That being said, speakers at this level can usually be improved and/or customized to the current situation by some external EQ done by a competent person. 

Your workflow doesn't go into great detail, but you say you used an ART CX310 crossover and a drive rack of some kind.  These tools are like sharp knives - in the hands of someone who knows what they are doing, they can help.  In the hands of someone inexperienced, they can cause damage.  For the average user, buying subs and tops from the same series is generally a good idea, and most systems like this are designed so that you plug the line into the sub, and then use a post-crossover output on the sub to feed the mid/high.  Doing this per the manufacturer's design will give good results.  Using an external crossover may be actually worse than using the internal crossover of the powered speaker, as there may be phase and EQ alignment issues that need to be compensated for.

Another potentially relevant thing is speakers that are designed for live sound may be tuned differently than "DJ" speakers.  Live sound speakers are generally flatter, which to someone who is used to smiley-face EQ, may sound dark.

All this is to say that your observations are very instructive and to keep at it, but make sure you understand all the variables before going too far out on a limb making a conclusion.

The idea we had behind using a crossover is so that the signal would reach every speaker when it's supposed to. We figured phasing issues would actually arise if we didn't use the crossover, due to the first speaker processing the sound, dividing it and then sending to another speaker entirely. So, what exactly are the indicators of phase misalignment? Obviously if there's a blatant delay between the two speakers, but if it's more subtle than that yet still enough to effect the performance, how do you know?

We tired to keep the signal as untouched as possible until it got to the speakers. That's why is was elected to use only 2 pieces of equipment from the source to the speaker. Although, i'm not sure exactly how the "speaker management" thing was supposed to help. Or what exactly it's even supposed to manage.
We saved all of the bass music for later in the evening when we could use the Electro Voice & Yamaha systems so we could use the subwoofers. I was playing Rusko - Lion's Paw (http://www.youtube.com/watch?v=301LGWph_rw (http://www.youtube.com/watch?v=301LGWph_rw)), I played it once with the processor in. Took the mixer's output & put it straight into the crossover. Sounded EXACTLY the same. The bass wobbles were still just as low, heavy & bouncy. The horns & high hats were just as high, loud and sharp as they were without the box. I didn't know it was going to be in the set-up and i had no clue why it was there either.

Also, one of the more... intense, discussions we had was sampling content. I tested the exact same, 2116kbps 85Mb .Wav file on all the QSC, Yamaha & Electro Voice speakers. Most of the people there agreed with me that if you use the same song across each speaker you should be able to hear the differences. And it's not like it's a lousy song, i'd consider it a high-quality recording, and i know i'm not the only one. I've heard the song countless times & am very familiar with it. Many people agreed that it reproduced sounds all over the entire audible frequency range, although the bass in the song is what stands out the most, if you focus on other details, you will notice them.
But strangely enough, some people argued that no matter what you play, the speaker will perform as good or as bad as it will regardless. Saying that picking a certain sampling source to compare everything to is pointless. It didn't really make any sense to me. Like if all speakers sound the same then i didn't understand why they were there in the first place???

Anyways, what's the golden standard on sampling content? Is there a certain criteria for finding the perfect universal piece that all systems can compare to? What about the equipment it's played from?

Title: Re: 15in vs 12in
Post by: Phillip McVea on April 14, 2014, 09:22:27 pm

15" drivers start to beam around 1050hz, while 12" drivers a bit higher, around 1350hz, and your 6" driver around 2750hz. Depending on where the speakers cross over to the high frequency horn, this may have been the effect you are describing. Beaming is where the drivers start to become directional, so if you are standing for example 45 degrees off axis from the speaker, everything that the 15" driver reproduces above 1050hz would drop off in level, the more off axis, the greater the effect. I have a set of 2-way speakers at work where the crossover is at 2200hz and uses a 12" woofer; off axis, the hole between 1350hz-2200hz is very prominent. Even on axis, although the frequency response of the direct sound is flat, the reflections off the walls/ceiling, etc from the off axis of the speaker with the hole in the mids gets bounced back with that hole in the mids confusing our ears.

For DJ type sound reinforcement where you will always use subs, the 12" boxes typically have better off axis sound (where most of the audience is anyways). Not because a 15" with appropriate hf horn couldn't be designed, but because usually the 15" version was designed for more low frequency extension (not needed with subs) and the off axis hole in the mids is just a trade off as a larger 2" hf driver with a lower crossover point would drive costs up too much.

So what i take from this is that the problem isn't how the sound is made by the driver, but rather how it travels away from the driver? But is that problem solved by going from 15in to 12in (with a system that includes subwoofers), or just lessened?
 
You mentioned directivity, in most cases i was standing in the middle of 2 speakers making a mirror image from each other. We had "listening spots" - pieces of tape on the ground that represent 8ft, and 20ft from the speaker, with a center, left & right(each 6ft away from center) point for each distance mark. On the 15in 2-way speakers, it sounded pretty uniform at both distances & sides. it was only when you went to extremes (15-20ft to the left/right, 25+ft back from the center). However, I did notice that, from the 15in 2-way boxes that had no sub, what bass they did create traveled further, but only if you stayed in the center. Like when i was at 8ft, there was plenty of bass of course. If you go to the sides, it decreases a bit. I stood at 20ft center, and there was a reasonable amount given the circumstance. But it was only when i moved to the left or right that the bass lessened dramatically, at a much faster rate than at 8ft. The "muddy" sound only became more pronounced the further off center i got, like you said. At higher sounds, i moved the same distances to the left & right, and the sound didn't diminish such a substantial amount. At both 8ft and 20ft the loudness was still appropriate for the distance, regardless of how far off center you were.

From what i know, the volume was what most people would consider barley/moderately loud. Alot of people got around 80db, but this was also outdoors with the wind blowing, cars occasionally passing by, construction, etc. Plus, no one really went into this trying to get numbers out of it, just matching some speakers up to see which is best.


 
Title: Re: 15in vs 12in
Post by: g'bye, Dick Rees on April 14, 2014, 09:33:01 pm
Bazinga.
Title: Re: 15in vs 12in
Post by: Peter Morris on April 15, 2014, 06:03:02 am
Hi Philip,

As a rough guide - 15 inch speakers work in their piston range up to about 500 Hz, 12 inch speakers about 800 Hz, after which you are operating in the cone breakup frequency range.  Similarly a 1.75 diaphragm compression driver will only go down to about 1K2 Hz safely for PA applications.
 
Therefore the 12 and 1 combination has less of the spectrum where the speaker is operating outside of its optimum frequency range. Accordingly the 12 and 1 combination will be more articulate but will lack the bass capability of the 15 which can displace more air (assuming the same Xmax etc. for both).

If you want the 15 and horn to sound better you will need to use a bigger compression driver and cross at lower frequency, or use a mid-range driver to fill the gap between 500 & 1K2 Hz, but that's a whole new set of problems to solve.
 
Here’s RCF latest 15 + horn. It crosses at 650Hz http://www.rcf.it/en_US/products/touring-and-theatre/tt5-a. To achieve the low crossover frequency they have used a 4 inch diaphragm HF driver and large horn. The only problem is the break up modes in the VHF region of the compression driver.  I suspect it won’t sound as sweet in the VHF region but the compromise as a whole will be excellent.

So to answer your question - the 12 will sound better, the 15 will make more bass. If bass output is the limiting factor the 15 will be louder.
Title: Re: 15in vs 12in
Post by: Bob Leonard on April 15, 2014, 09:25:25 am
So to answer your question - the 12 will sound better, the 15 will make more bass. If bass output is the limiting factor the 15 will be louder.

Now that's a pretty broad stroke of the brush. That answer will depend on the quality of the cabinet/drivers, manufactures design, and installation type.
 
At the MI level, all bets are off, but at a professional level and with good cabinets a 15" driver in a two way cabinet can and usually will produce more otuput and usable sound at all frequencies, and the benefit being a smoother transition to the lower cabinets/subs.
 
My concern has always been this transition and the upper cabinets ability to cover the full audio spectrum down to the crossover center point. Few 12" speakers do this well in the common one over one point source configuration, where most quality 15" drivers are able to replicate all of the same frequencies the 12" driver will replicate with the added benefit of being able to replicate low/mid frequencies with more accuracy and detail.
 
There was a reason for my replacing ALL of my SRX722's with SRX725's, and it wasn't because the weighed less. ;D
Title: Re: 15in vs 12in
Post by: Peter Morris on April 15, 2014, 10:14:59 am

Now that's a pretty broad stroke of the brush. That answer will depend on the quality of the cabinet/drivers, manufactures design, and installation type.
 

Sorry  Bob - I thought in terms of responding to the original question it would have been assumed that we were talking about equivalent speakers in terms of design, build quality … even the same brand and series, just the 12 vs 15  but with both using the same HF components.
Title: Re: 15in vs 12in
Post by: Bob Leonard on April 15, 2014, 12:29:51 pm
Please don't appologize. Your statement could be assumed correct, but for the sake of clarity it's always best to be specific regardless of assumtion. Just my opinion based on the levels of knowledge of those who may be reading these replies and number of variables involved.

The OP ran a test based on his needs, came to a conclusion and asked for further guidence. His test, although basic and somewhat flawed, led to his conclusions based on his experience with a limited number of drivers and configurations. The answer for his question based on his test will be all the above and maybe.
Title: Re: 15in vs 12in
Post by: John Roberts {JR} on April 15, 2014, 12:43:25 pm
I kind of liked Peter's answer... While you "could" make a 2 way 15" sound Ok, (I've heard some), all things equal it will be more challenged in the midrange than the 12".

Honestly both are challenged in the midrange for hifi fidelity, the higher SPL benchmark used for live sound may trade some midrange performance for the extra bass.

It is instructive to look at what combinations the manufacturers sell the most of. The marketplace over time, ultimately makes the final call on "cost effective, but doesn't suck too much" speakers. 

The ones that suck too much, eventually go away, and this speaker category is mature.

JR
Title: Re: 15in vs 12in
Post by: Jim McKeveny on April 15, 2014, 06:09:38 pm
When asked about wedge preferences, a young Cyndi Lauper said "15's are for boys. 12's are for girls"...
Title: Re: 15in vs 12in
Post by: Bob Leonard on April 15, 2014, 06:31:49 pm
Ever notice that the first thing out of peoples mouths when a new manufacturers line is announced is usually either, "I hope they offer a 15" wedge.", or, "Why don't they have a 15" wedge." I'm biased, I like good 15" drivers.
Title: Re: 15in vs 12in
Post by: Curtis H List (Too Tall) on April 17, 2014, 10:25:00 am
Hi Philip,

As a rough guide - 15 inch speakers work in their piston range up to about 500 Hz, 12 inch speakers about 800 Hz, after which you are operating in the cone breakup frequency range.  Similarly a 1.75 diaphragm compression driver will only go down to about 1K2 Hz safely for PA applications.
 
Therefore the 12 and 1 combination has less of the spectrum where the speaker is operating outside of its optimum frequency range. Accordingly the 12 and 1 combination will be more articulate but will lack the bass capability of the 15 which can displace more air (assuming the same Xmax etc. for both).


My friend Al Limberg used to bring in all his used boxes and current inventory when they they quit working.
He had a set of Yamaha Waveforce that used Eminence 15" and Eminence 1" throat compression driver mounted on a large conical hor. Diameter 15" or greater

My friend Al Limberg used to bring me all his used boxes and current inventory when they quit working.
He had a set of Yamaha Waveforce that used Eminence 15" and Eminence 1" throat compression driver mounted on a large conical horn. Diameter 15" or greater.
Except for a design flaw in the xover that blew up a couple of parts it was an impressive sounding box.
After I did measurements and some modeling I found a work-around that could stand the juice he put into the xover parts.

When finished Al rented these out more then any system he owned. Over time they made more money than any other system he used.

NOTE: For these to work you MUST use a large high frequency horn (Conical Preferred)
Also the xover is critical. It needs to be steep and sum well in the xover region.
At best you will still have some narrow band problems at or very close to the xover point.

Lastly there are some problems with directivity as mentioned above.
Not much you can do about this. I opted to go for “Flat” on axis and live with the off axis roll-off.

One last thing. I have measured more than a couple horns and my hand down winner is Conical.
Not very practical since they will not array together, but used one at a time I like them best.






If you want the 15 and horn to sound better you will need to use a bigger compression driver and cross at lower frequency, or use a mid-range driver to fill the gap between 500 & 1K2 Hz, but that's a whole new set of problems to solve.
 
Here’s RCF latest 15 + horn. It crosses at 650Hz http://www.rcf.it/en_US/products/touring-and-theatre/tt5-a. To achieve the low crossover frequency they have used a 4 inch diaphragm HF driver and large horn. The only problem is the break up modes in the VHF region of the compression driver.  I suspect it won’t sound as sweet in the VHF region but the compromise as a whole will be excellent.

So to answer your question - the 12 will sound better, the 15 will make more bass. If bass output is the limiting factor the 15 will be louder.
Title: Re: 15in vs 12in
Post by: Richard Turner on April 17, 2014, 11:44:04 am
I've been using a pair of e210 yorkville as utility speakers for about 2 years now and could not be happier. they are 2 10" drivers and  1" exit horn idn D'Apallito (sp?) configuration.

the 2 of them fit in the same space as a single 115 box for packing just about 2" taller have almost the same lower cutoff frequency yet have a but more to offer in the low mids department

I've read other good comments about the JTR triple 8 which uses 3 8" driver with one having cocentric HF driver.

Myself I just dont think I would ever buy another 2 way 15 and horn box (still have a bunch that get used regularily) but I find better overall coverage with 2 12" boxes side by side. I'm guessing the test session you were doing was for a 1 box solution for small area coverage.
Title: Re: 15in vs 12in
Post by: Sean Thomas on April 17, 2014, 04:12:59 pm
Richard Turner - Myself I just dont think I would ever buy another 2 way 15 and horn box

Phillip - So to answer your question - the 12 will sound better, the 15 will make more bass. If bass output is the limiting factor the 15 will be louder.


Great topic.  I tend to agree with the "general thought" that a 15" being crossed over as high as 2k is not a good idea.  I much prefer a compact 3 way box (dB Tech T12) than a 2 way.  If I had to buy or use a 2 way trap cab, I would go with a 12".  Size, cost, and weight are also a plus for 12".
Title: Re: 15in vs 12in
Post by: Greg_Cameron on April 18, 2014, 02:02:38 pm
I kind of liked Peter's answer... While you "could" make a 2 way 15" sound Ok, (I've heard some), all things equal it will be more challenged in the midrange than the 12".

Honestly both are challenged in the midrange for hifi fidelity, the higher SPL benchmark used for live sound may trade some midrange performance for the extra bass.

It is instructive to look at what combinations the manufacturers sell the most of. The marketplace over time, ultimately makes the final call on "cost effective, but doesn't suck too much" speakers. 

The ones that suck too much, eventually go away, and this speaker category is mature.

This discussion reminds me of why the Dave Rat designed the Rat Trap 5 they way he did. It's a 4-way design which in and of itself introduces problems associated with multiple drivers/bandpasses in a single box. But for it's day it solved some problems. The trick was to get the drivers as close together as possible which wan't easy until EV came out with horns that could worked in tight spaces. The 4 way design is  15" x2, 10" x2, 4" compression driver with 2" exit, 2" compression driver with 1" exit. The 15 cross over to the 10s at 250Hz, the 10s crossover to the 2" horns at 800Hz, and the 1" horns kick in at 8KHz. The biggest problem with the design is that the 10s aren't that close together. So you have some problems in that area. But they're jammed in tight with the 2" horn and the drivers are all pretty close together so they behave pretty well considering. Interestingly, even the 10s start to get pretty beamy in the upper end of their range. This can be both an advantage and a disadvantage. When hanging large clusters of those boxes, the beaming counteracts the combing in the vocal range to some degree and you've still got good coverage from all the boxes pointing everywhere. But if you're using a smaller number of boxes, it can be an issue.

Title: Re: 15in vs 12in
Post by: Othmane Alaoui on April 22, 2014, 05:30:17 pm
I kind of like both configuration depending on the use. I have QSC HPR122i, NX25P from yorkville, both are 12'' drivers in the preamp and I also have EF508 yorkville speakers, these are 15 inch bi-amp.

They all serves me depending on the type of program and or application. To be transparent, I love the sound of the Yorkville NX25P, they are very smooth, transparent and pretty flat. when coupled with some Low's (SBA760), they get all the low end needed to be full spectrum system.

The passive single 15' (EF508) is my first choice for anything live band, soft rock, vocalist and string type of program, always matched with a single or double 18. The sound of these is very pleasant, almost warm.

All of these cabs have their pro's and con's depending of the application. I also have the EV QRX212 and feel the same as Bob in regards to the LOW transition from the tops to the subs. My srx728's overdrive the QRX by a lot (4 over 4), and the SRX725 sounds just fine when I use them with the 728. But again, it always depends on what I do, with who and for how many.

For vocal use, conferences, speach duty, I often provide single 12's.
For the processing, I agree that using a DriveRack can ''scrap'' your sound if not commissioned properly. In amplified speaker world of this class, I do not think any external processing is required.
For biamped or triamped system, there is a lot more to consider, therefore, responses will always be subjective. 
Title: Re: 15in vs 12in
Post by: Rich Barrett on April 22, 2014, 06:29:01 pm
summarized/bolded for the impatient people.
I was recently browsing selections for pole-mount/"point-source" loudspeakers, coaxial loudspeakers, "fixed curvature line array" loudspeakers, variable curvature line array loudspeakers, and also home audio loudspeakers.

Long story short i noticed that alot of manufacturers usually include the following variants in their speaker lines: 2-way 1/1.75in high & 12in low, 2-way w/ 1/1.75in high & 15in low, and 3-way w/ 1/1.75in high, 6.5in mid & 15in low.
These are all speakers that are made (primarily) for live sound reinforcement. By that i mean they're made to be loud as opposed to accurate. Most have peak amplifier power ratings of 1000-2000 watts (w/ mains input @ 120v). about 4/5 of the speakers i looked at had the amplifier built in to the actual cabinet housing.

While i understand many of the company's decisions to produce a 3-way model for better dispersion control (and the other benefits of a 3-way design), but i'm very weary of the 2-way models that use 15" drivers, often the same ones they put in the 3-way models. It concerns me because within a 2-way speaker, the woofer must account for some of the mid range frequencies, the same frequencies that would otherwise be created by a smaller 6.5in driver that could better reproduce the wavelengths of mid-range frequencies. I like the idea of using a 12in driver (at the largest) in a 2-way speaker because, while it is smaller, it could better create the entire sound range that doesn't end up sounding worse.

For example, i've noticed that in a 2-way system with a 15in LF driver, whenever someone with deeper voice speaks at the higher point of their voice, it sounds like there's something that's "holding" the sound back, almost like a muddy sound. As if someone taped a few layers of thin fabric over my ears when they speak like that. But as they progress into the deeper octaves of their voice, it sounds deeper and more direct i guess you could say.
it's kind of difficult to describe the difference without something happening right in front of me, but the point is if they were to repeat the same thing in a 3-way system with a 6.5in MF & 15in LF driver, their voice sounds CONSISTENTLY more "direct", clearer, even throughout the lower sounds. I find that even the mid range has more "punch" to it, like on kick-drums, you can feel the beginning of the note have more impact & spread from the speaker. And in bass music, those long notes that dip into the sub-bass region then fade up into a higher and higher sound. You can really feel the notes "carry through" and have a fuller sound, even as they carry over from sub-bass speakers to the full-range speakers.

While i'm far from an expert in sound reinforcement (and writing obviously), my personal theory is that this is because of the amount of air the driver is moving, and in relation to how fast/how often & loud it's trying to make it. Meaning 15in drivers are best for creating bass frequencies and ONLY bass frequencies, because the size of the wavelength is appropriate to the thing that's trying to create it. Just like 21in drivers are best for creating sub-bass frequencies and ONLY sub-bass frequencies. And just like 6.5in drivers are best for creating mid-range frequencies. Obviously the EXACT definitions of high/mid/bass range are all subjective to the actual speaker and various other factors (too many to list out).

BUT the point remains, what is the best balance of both loud AND clear, a 2-way system with 12in driver or a 2-way system with a 15in driver?

I worked at Boston Acoustics waaaay back in the day and the engineers always said a great amp and crappy speakers will always outshine good speakers and a crappy amp.

that said, since the mid 90's, speakers have come a long way in cone/surround/spider material and design, voicecoil heat dissipation and the baskets and magnets are stronger. while a big 15" driver USED to be only good for boomy bass, say for a bass guitar or hip hop low end, modern drivers can push more air faster with less deflection of the driver surface (among other mechanical limitations)

so if a reputable loudspeaker mfg sells a 2-way 15" box, it's safe to say it's because they designed it to accurately recreate the signal sent to it (as spec'd), at the DB's it's designed for, with the power it requires. in other words, don't sweat it.

get amps rated rms 20% OVER your cabinet's max wattage to make your loudspeakers happy (but never overdrive them or you'll cook em!!)
Title: Re: 15in vs 12in
Post by: Luke Geis on April 23, 2014, 05:37:57 pm
I worked at Boston Acoustics waaaay back in the day and the engineers always said a great amp and crappy speakers will always outshine good speakers and a crappy amp.

that said, since the mid 90's, speakers have come a long way in cone/surround/spider material and design, voicecoil heat dissipation and the baskets and magnets are stronger. while a big 15" driver USED to be only good for boomy bass, say for a bass guitar or hip hop low end, modern drivers can push more air faster with less deflection of the driver surface (among other mechanical limitations)

so if a reputable loudspeaker mfg sells a 2-way 15" box, it's safe to say it's because they designed it to accurately recreate the signal sent to it (as spec'd), at the DB's it's designed for, with the power it requires. in other words, don't sweat it.

get amps rated rms 20% OVER your cabinet's max wattage to make your loudspeakers happy (but never overdrive them or you'll cook em!!)

The technology has come a long way, yes. The downside is that the technology has followed into the smaller elements as well. Meaning that the ratio is probably still the same today as it was 20 years ago in terms of difference between a larger element and a smaller one? In other words a smaller element is still going to sound better in a 2 way design. The only limiting factor is frequency range and potential level. The larger elements will produce more volume and go deeper into the lower octave. This would be the same 20 years ago. A modern box should sound better today than even a higher end box did 20 years ago, but that is not always the case. I simply believe that modern technology has allowed us more volume, linearity and lighter construction, more so than better sounding boxes.

As for the size of the amp you suggest, I think your a little over zealous?!?!?!? I am large proponent of larger is better, but feel that rms +20% larger than peak is WAY overkill. Even a modest speaker rated for 500 watts peak would then require an amp capable of about 2,400 watts peak based on your guideline!!!!! Most amps these days are rated for peak power. Many don't even list rms anymore. Rms is usually 1/4 of peak power ( at least for speaker ratings anyway ). Could you imagine buying an amp for a sub rated for 4,000 watts peak, or even a main rated for 1,000!!!!! You would need a 20,000 and 5,000 watt peak amp respectively!!!! Even if rms was half of peak power you would still need way too much amp......

The way it works is pretty simple. A speaker has a sensitivity rating and a theoretical SPL at peak wattage rating. If you power a speaker with it's peak rated wattage, you should in theory acquire the rated peak SPL. Highly doubtful though as power compression will eat several DB's and you can only run at peak power for a short period of time. An amplifiers peak power is actually doubled when you start going into solid clip!!!! You should be roughly 3db down just before the lights start to flicker. You should never desire to power a speaker at it's peak power ( for long anyway ) and you should never desire to clip the amp. Which means that you should spec the system that goes out to acquire the needed level without having to go to that distance with the speakers and amps. The program rating of a speaker is usually about as far as you should ever wish to run it for any length of time. The rms rating ( AKA continuous rating ) is the more ideal range to run at if at all possible. Which means you really only need an amp that is rated for about 75-100% of the speakers peak rating. This should give you enough power to run up to the program power rating of the speaker with a little bit of headroom left.

Buying an amp that is rated for between the 75-100% mark may be the limiting factor? The cost difference for an amp rated for 4,000 watts and 6,000 watts may be too much? The 4,000 watt amp which may sit right at the 75% mark of your speakers peak power should be more than enough in theory. The extra cost to acquire the other 2,000 watts may be several hundred dollars and only net you a theoretical 1-2 db's of potential gain. That gain is negligible for the added cost and doesn't add any protection for the speakers at all. Running the speakers at their peak rated power can only be done for a short period of time ( possibly only minutes )!

M.I level gear isn't always the most robust and probably not the most honestly marketed stuff either. Other higher end stuff usually comes with it's own required amplification or at least a recommended list of amps. I can guarantee that a D&B rig ( which is required to run with Lab Gruppen amps ) is not running at RMS+20% of peak speaker wattage! The last D&B rig I worked with used the larger D80 Lab amps and powered 2 V8 boxes per channel at 4,000 watts. Each V8 is rated for 2,000 watts peak and 500 watts rms. In other words one of the top companies out there is running their system so that each speaker see's roughly 100% of it's peak rated power. Guess what? There is a lower power version of the same thing! You can run the same rig with the Lab Gruppen D12 amp which is rated for 1,200 watts per channel. The only difference is less potential output. The 1,200 watt output is right about the 60% mark. Which puts it just above the program rating of those speakers no doubt.
Title: Re: 15in vs 12in
Post by: Rich Barrett on April 23, 2014, 06:27:11 pm
The technology has come a long way, yes. The downside is that the technology has followed into the smaller elements as well. Meaning that the ratio is probably still the same today as it was 20 years ago in terms of difference between a larger element and a smaller one? In other words a smaller element is still going to sound better in a 2 way design. The only limiting factor is frequency range and potential level. The larger elements will produce more volume and go deeper into the lower octave. This would be the same 20 years ago. A modern box should sound better today than even a higher end box did 20 years ago, but that is not always the case. I simply believe that modern technology has allowed us more volume, linearity and lighter construction, more so than better sounding boxes.

As for the size of the amp you suggest, I think your a little over zealous?!?!?!? I am large proponent of larger is better, but feel that rms +20% larger than peak is WAY overkill. Even a modest speaker rated for 500 watts peak would then require an amp capable of about 2,400 watts peak based on your guideline!!!!! Most amps these days are rated for peak power. Many don't even list rms anymore. Rms is usually 1/4 of peak power ( at least for speaker ratings anyway ). Could you imagine buying an amp for a sub rated for 4,000 watts peak, or even a main rated for 1,000!!!!! You would need a 20,000 and 5,000 watt peak amp respectively!!!! Even if rms was half of peak power you would still need way too much amp......

The way it works is pretty simple. A speaker has a sensitivity rating and a theoretical SPL at peak wattage rating. If you power a speaker with it's peak rated wattage, you should in theory acquire the rated peak SPL. Highly doubtful though as power compression will eat several DB's and you can only run at peak power for a short period of time. An amplifiers peak power is actually doubled when you start going into solid clip!!!! You should be roughly 3db down just before the lights start to flicker. You should never desire to power a speaker at it's peak power ( for long anyway ) and you should never desire to clip the amp. Which means that you should spec the system that goes out to acquire the needed level without having to go to that distance with the speakers and amps. The program rating of a speaker is usually about as far as you should ever wish to run it for any length of time. The rms rating ( AKA continuous rating ) is the more ideal range to run at if at all possible. Which means you really only need an amp that is rated for about 75-100% of the speakers peak rating. This should give you enough power to run up to the program power rating of the speaker with a little bit of headroom left.

Buying an amp that is rated for between the 75-100% mark may be the limiting factor? The cost difference for an amp rated for 4,000 watts and 6,000 watts may be too much? The 4,000 watt amp which may sit right at the 75% mark of your speakers peak power should be more than enough in theory. The extra cost to acquire the other 2,000 watts may be several hundred dollars and only net you a theoretical 1-2 db's of potential gain. That gain is negligible for the added cost and doesn't add any protection for the speakers at all. Running the speakers at their peak rated power can only be done for a short period of time ( possibly only minutes )!

M.I level gear isn't always the most robust and probably not the most honestly marketed stuff either. Other higher end stuff usually comes with it's own required amplification or at least a recommended list of amps. I can guarantee that a D&B rig ( which is required to run with Lab Gruppen amps ) is not running at RMS+20% of peak speaker wattage! The last D&B rig I worked with used the larger D80 Lab amps and powered 2 V8 boxes per channel at 4,000 watts. Each V8 is rated for 2,000 watts peak and 500 watts rms. In other words one of the top companies out there is running their system so that each speaker see's roughly 100% of it's peak rated power. Guess what? There is a lower power version of the same thing! You can run the same rig with the Lab Gruppen D12 amp which is rated for 1,200 watts per channel. The only difference is less potential output. The 1,200 watt output is right about the 60% mark. Which puts it just above the program rating of those speakers no doubt.

20% over peak of 500watt driver is a 625 watt amp ... I musta typed what I was thinking really wrong for you to think I was recommending a 2,400 watt amp!!!

found it .. I accidently said rms amp wattage - sorry
Title: Re: 15in vs 12in
Post by: Curtis H List (Too Tall) on April 24, 2014, 10:50:49 am
This discussion reminds me of why the Dave Rat designed the Rat Trap 5 they way he did. It's a 4-way design which in and of itself introduces problems associated with multiple drivers/bandpasses in a single box. But for it's day it solved some problems. The trick was to get the drivers as close together as possible which wan't easy until EV came out with horns that could worked in tight spaces. The 4 way design is  15" x2, 10" x2, 4" compression driver with 2" exit, 2" compression driver with 1" exit. The 15 cross over to the 10s at 250Hz, the 10s crossover to the 2" horns at 800Hz, and the 1" horns kick in at 8KHz. The biggest problem with the design is that the 10s aren't that close together. So you have some problems in that area. But they're jammed in tight with the 2" horn and the drivers are all pretty close together so they behave pretty well considering. Interestingly, even the 10s start to get pretty beamy in the upper end of their range. This can be both an advantage and a disadvantage. When hanging large clusters of those boxes, the beaming counteracts the combing in the vocal range to some degree and you've still got good coverage from all the boxes pointing everywhere. But if you're using a smaller number of boxes, it can be an issue.

Hi,
On the placement issue how far apart 10" cone driver is from the mid horn in the crossover region is a big problem if you are using them for Near Field.
Once  past near field it become much less of a problem. Of course beaming and other problem remain.
Note on this box he has both 10"  in a low mid/mid/low mid vertical configuration if you move up or down you will hear a sift because the arrival times for the 10" to you has changed. But if you move side to side you get much less of a time shift. This is why you see drivers on top of each other and not as much horizontal.
I have glossed over and ignored other factors or explained "Why". Did not want to write of book.
Title: Re: 15in vs 12in
Post by: Greg_Cameron on April 24, 2014, 01:13:55 pm
On the placement issue how far apart 10" cone driver is from the mid horn in the crossover region is a big problem if you are using them for Near Field.

The 10s are about an inch from the horn on those boxes, maybe less. So they couple pretty well. Since the 10s operate at 250 to 800, they tend to interfere with each other within the box noticeably in the near field since their distances are over a 1/4 wavelength for much of their range. When arraying the boxes together side by side, if you put the 10s together they couple ok from box to box since they're only a few inches apart. When hanging 24 of them in a cluster, there's quite a bit going on ;)