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[billy merritt]

Hi! Please help! I am just now replacing a 1" compression driver in a B52 (SL15) speaker with a 2" RCF compression driver. The idea is to majorly upgrade this speaker without buying something new and much more expensive. Only problem is the length of the new horn that the compression driver is attaching to is about 2" longer (deeper in the speaker cabinet) than the old one. I didnt think this was an issue until a friend explained that it may need to be delayed (or opposite?) to match it up with the 15" woofer.
Anybody who can help...it would be very appreciated!!

[Mac Kerr]

Anybody who can help...it would be very appreciated!!

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Mac

[Luke Geis]

Well the only way would be to Bi-amp the speaker and use a program like Smaart to align the drivers with a capable crossover / drive unit. The problem is that you have to be rather good with the program and knowledgeable about crossover networks and the drivers themselves to be sure you are not going to hurt anything, or actually get things right. 

This is not a task that is simple or even guaranteed. Just because the CD driver is better than the original does not mean it will make the speaker sound better. It may improve the odds, but that is dependent upon the users ability to properly set the crossover network and tune the drivers. In this case it may mean adding expense in amplifiers, crossovers / drive units and if you want to get the last 10% of performance and properly align things, you will need a measurement system that you can properly run.

[Stephen Kirby]

You can introduce phase shift into regions of the HF with the passive crossover design.  This is what top manufacturers do.  But that is an art.

DIY is a real hit and miss sort of thing.  Especially without in-depth knowledge of the subject.  You will probably have more headroom in the HF than you did with the stock driver.  I also doubt the original crossover did much in the way of phase alignment so it will be luck of the draw whether the crossover region is better or worse.

You could mess around with bi-amping, delays and allpass filters using something like StudioSix Transfer Function which is a bit cheaper albeit less sophisticated than Smaart.  Depending on how much you put into the exercise you will develop some level of understanding of the subject.  But it would be a labor of love for personal education.  Certainly not cost effective compared to simply buying good speakers.

[Paul G. OBrien]

Hi! Please help! I am just now replacing a 1" compression driver in a B52 (SL15) speaker with a 2" RCF compression driver. The idea is to majorly upgrade this speaker without buying something new and much more expensive.

Well better drivers is 1/3 of a better speaker system, the other two components are better processing and amplification. To take advantage of that 2" CD you really should bi-amp the box and add active processing(crossover, delay, EQ), and you could accomplish this by adding an amp with DSP processing built-in or by adding a separate processor if you already have enough amp channels. If the CD horn is big enough you should be dropping the crossover between the 15 and CD down to around 800-1khz from what was probably 2khz with the passive crossover, adding the appropriate amount of delay and EQ would require some study or the assistance of a more skilled individual that also has some hardware that could be used to measure the speaker system and develop some presets.

[billy merritt]

Wow, thank you!
this is some expert advice but is nevertheless way over my head. Question is, are the 2" RCF drivers a waste of money if they are not tuned using these methodologies? Again the current compression drivers are the cheaper 1" generic brand. The passive crossover is at 1.6khz.

One other note is, in order to fit the horn on the front of the cabinet we are having to cover the hole for the old horn with 1/2" plywood and cutting a new whole in that one.  While the new horn is deeper the flare or port or whatever you call it is actually smaller. The philosophy being it is a long-throw horn. So because of this, the entrance of the horn is 1/2" raised from the original speaker panel.

There are 8 of these speakers. 4 sit on stacks of subs on each side of the stage.

I will be doing a test comparative tomorrow between the regular speaker and the one with the new 2" driver.

[Don T. Williams]

Wow, thank you!
this is some expert advice but is nevertheless way over my head. Question is, are the 2" RCF drivers a waste of money if they are not tuned using these methodologies? Again the current compression drivers are the cheaper 1" generic brand. The passive crossover is at 1.6khz.

One other note is, in order to fit the horn on the front of the cabinet we are having to cover the hole for the old horn with 1/2" plywood and cutting a new whole in that one.  While the new horn is deeper the flare or port or whatever you call it is actually smaller. The philosophy being it is a long-throw horn. So because of this, the entrance of the horn is 1/2" raised from the original speaker panel.

There are 8 of these speakers. 4 sit on stacks of subs on each side of the stage.

I will be doing a test comparative tomorrow between the regular speaker and the one with the new 2" driver.

Billy, you might get lucky and it might sound better, but the red flags are all over the place. 

All the advice given is excellent.
 
Red Flag 1 - With your last reply you say you have 4 of the boxes a side.  Bad news.  The more boxes (sound sources) you have the worse it sounds.  You hadn't mentioned that before.

Red Flag 2 - These are 15" speakers you are using as mid-range.  In my opinion, most 15's sound pretty bad above 700-800 Hz, so using the old 1.6K crossover (even with a larger format HF driver) improves very little.

Red Flag 3 - The new horns are smaller!  That usually indicates less pattern control and usually dictates an even higher crossover point, but speaker design is a complex process, so these are not absolutes.

Rather that revamp boxes, look for a pair of good used pro 3 way boxes.  A pair will probably play louder and will absolutely sound better that the 8 MI level boxes you are attempting to "improve".

[Scott Holtzman]

Billy, you might get lucky and it might sound better, but the red flags are all over the place. 

All the advice given is excellent.
 
Red Flag 1 - With your last reply you say you have 4 of the boxes a side.  Bad news.  The more boxes (sound sources) you have the worse it sounds.  You hadn't mentioned that before.

Red Flag 2 - These are 15" speakers you are using as mid-range.  In my opinion, most 15's sound pretty bad above 700-800 Hz, so using the old 1.6K crossover (even with a larger format HF driver) improves very little.

Red Flag 3 - The new horns are smaller!  That usually indicates less pattern control and usually dictates an even higher crossover point, but speaker design is a complex process, so these are not absolutes.

Rather that revamp boxes, look for a pair of good used pro 3 way boxes.  A pair will probably play louder and will absolutely sound better that the 8 MI level boxes you are attempting to "improve".

Let me tell you a story.  I have been dabbling in audio for over 40 years.  Have a few finished and unfinished technical degrees and have spent my life repairing, installing, designing, supporting, selling, managing blah blah blah businesses based around electronics.

With all that being said I fell into the trap and bought a trailer load of horn loaded cabinets from an A list sound company and brought them home to care and feed them. 

A year and half later I am doing my second gig with them tomorrow.  I have a rack full of amps and expensive processing, the aforementioned Studio Six tools, two measurement microphones and at least 100 hours in driver selection, studying, wood working, wiring, programming, testing, programming, testing, programming testing et al.

In the end to finish four boxes I could have bought the used Turbosound Aspect's that are probably 10db louder across the usable response, 100lb lighter and recognizable.

I received a priceless education and a four speakers that when I push a pair up the ramp on the truck by myself it's questionable if I am going to make it or get killed by my creation.  I doubt I would sell these to anyone (unless I didn't like them or they knew what they were buying).

If you want to learn quite a bit you have need to invest in the measurement software and a calibrated microphone, a bunch of time and you still may wind up with less than what you started with.

[billy merritt]

Well I got em put together and tested, and the good news is they don't sound any worse. Hard to say they sound better though. I think I can tell a slight difference but not really the $400 value of investment just yet. Will do some tuning and see what I can get out of it. My hope is that it will at least have a further throw.
The next question I feel I need to address is the crossover. The factory installed crossover is set to 1.6khz. Does anyone know where I can find a different crossover? I've totally searched the web for passive crossovers and the options are surprisingly slim! My best guess is I should find something around 1.2, but again, it's a guess. Then the other question is, would it really sound any different.

[Len Zenith Jr]

Off the shelf x-overs are designed for nominal impedance's (8 ohms), whereas custom x-overs are designed for the impedance of the drivers at the x-over frequency. At 1.2 kHz the impedance of the woofer is probably closer to 12 ohms than 8 ohms and as such an off the self crossover would have too much mids, you could add a Zobel network to compensate but a scratch built crossover would be better than an off the shelf one. The more you tinker with this design without reading up on the basics of speaker design, the more Frankenstein this box will become. What you would gain going to a lower x-over is wider dispersion in the 1.2-1.6 khz range. Remember that a x-over is a slope and not a cliff, there will be an octave or 2 where the woofer and the horn both share output. Whether they play well together or not on this overlap (time, output, phase, ringing, etc) is the whole art of speaker design.

[ProSoundWeb Community]