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Title: aux fed subs
Post by: Bob Kidd on January 31, 2014, 12:37:29 PM
Based on previous post on this subject I decided to try and set up at aux fed subs using available crossovers and my sound craft so compact. I'm using dbx drive rack pa on tops and dbx 223 on subs. Routing through aux 14 on sound craft. Set crossover on 223 at 87hz and driverack at 90hz. Other than plating programmed music I have not used live yet. Given the different crossovers am I creating more issuses than solving?
Title: Re: aux fed subs
Post by: Patrick Tracy on January 31, 2014, 12:48:51 PM
Based on previous post on this subject I decided to try and set up at aux fed subs using available crossovers and my sound craft so compact. I'm using dbx drive rack pa on tops and dbx 223 on subs. Routing through aux 14 on sound craft. Set crossover on 223 at 87hz and driverack at 90hz. Other than plating programmed music I have not used live yet. Given the different crossovers am I creating more issuses than solving?

No way to know for sure without measuring the response. What matters is the actual acoustic crossover. The filters are just a means to that end.
Title: Re: aux fed subs
Post by: Scott Carneval on January 31, 2014, 01:17:35 PM
Based on previous post on this subject I decided to try and set up at aux fed subs using available crossovers and my sound craft so compact. I'm using dbx drive rack pa on tops and dbx 223 on subs. Routing through aux 14 on sound craft. Set crossover on 223 at 87hz and driverack at 90hz. Other than plating programmed music I have not used live yet. Given the different crossovers am I creating more issuses than solving?

There's a 10+ page post on this topic from a week or so ago. 
Title: Re: aux fed subs
Post by: Jason Lucas on January 31, 2014, 02:06:53 PM
If you're ok with running your tops mono, you could run both tops and subs off one unit and then you'd have the same crossover frequency.

Just an idea.
Title: Re: aux fed subs
Post by: Bob Kidd on January 31, 2014, 03:09:18 PM
If you're ok with running your tops mono, you could run both tops and subs off one unit and then you'd have the same crossover frequency.

Just an idea.

Thanks Jason, right now I have it setup as subs in mono and tops in stereo. This could be an option. I will more than likely go back to the traditional setup for now until I get this fine tuned. I did read through previous post which is why I started setting it up but was concerned based on crossovers I have available and that I do not run Smaart that I maybe creating more of an issue than helping clean up low end. Will look to upgrade crossover. Thanks
Title: Re: aux fed subs
Post by: Greg_Cameron on January 31, 2014, 03:23:15 PM
Thanks Jason, right now I have it setup as subs in mono and tops in stereo. This could be an option. I will more than likely go back to the traditional setup for now until I get this fine tuned. I did read through previous post which is why I started setting it up but was concerned based on crossovers I have available and that I do not run Smaart that I maybe creating more of an issue than helping clean up low end. Will look to upgrade crossover. Thanks

I've been running a DSP (XTA DP448) for my tops and an analog crossover for my subs for years (currently the dbx 223XL because my old BSS crapped out). There's nothing wrong with doing it that way and it works great. The potential issue with alignment is that the DSP introduces some latency relative to the analog sub processor. Since my tops are flow and the subs on the floor, it doesn't matter. If I were to stack the tops on the subs, I'd add the delay to match the tops at the aux output on my digital desk if was required.
Title: Re: aux fed subs
Post by: Bob Kidd on January 31, 2014, 03:52:32 PM
I've been running a DSP (XTA DP448) for my tops and an analog crossover for my subs for years (currently the dbx 223XL because my old BSS crapped out). There's nothing wrong with doing it that way and it works great. The potential issue with alignment is that the DSP introduces some latency relative to the analog sub processor. Since my tops are flow and the subs on the floor, it doesn't matter. If I were to stack the tops on the subs, I'd add the delay to match the tops at the aux output on my digital desk if was required.

Thanks, this helps greatly. I do stack mine and would need to determine how much delay is needed.
Title: Re: aux fed subs
Post by: Patrick Tracy on January 31, 2014, 04:01:28 PM
The potential issue with alignment is that the DSP introduces some latency relative to the analog sub processor.

Since the tops normally need to be delayed to the subs anyway the inherent latency of the DSP is a change in the right direction.
Title: Re: aux fed subs
Post by: Bob Kidd on January 31, 2014, 04:33:19 PM
Since the tops normally need to be delayed to the subs anyway the inherent latency of the DSP is a change in the right direction.

OK, well then I have been running all wrong then. In my traditional setup I never delayed the tops to the subs.
Title: Re: aux fed subs
Post by: Patrick Tracy on January 31, 2014, 05:14:39 PM
OK, well then I have been running all wrong then. In my traditional setup I never delayed the tops to the subs.

I seldom delay my tops for my little setup. But I do tend to place my subs forward of the mains a little.
Title: Re: aux fed subs
Post by: Jerome Malsack on February 01, 2014, 12:55:06 PM
Back in the day of Stereo Review they had some opinions on listening to various crossover slopes from sub to mains. 

The basic result was to give the sub a brick wall on the top to prevent it from going up, 12 or 24 db slope. 
The mains were aloud to have from no crossover and 3 to 12 db high pass.  Resulting in little audible or inaudible problems.

So for the Sub we should be trying to get the Sub low pass to 24 db.  Beyond that the question will be if the time or phase issues will be audible and where?   Add in the time to setup, test, adjust, test to satisfaction.  This will work well when outside at my place and setting up.  Not good usually at the show, along with each venues acoustics will be adding to the problems.

Having the flexibility to control the Subs output with out affecting the mains is the plus.  I still feel that a plosive coming from a 15 inch main is still going to be very audible and the correct filtering a processing on the channel strip helps and reduces the problem.  When this channel stip is removed from the sub it removes another part of the problem.

When the subs output is exaggerated to have a stronger punch and kick then the bass, organ, and keys will be exaggerated and the transition to the mains and tops will hear the audible difference at the transition if the channel strip to mains and the aux to the subs is not set accordingly.  When you adjust the sub out with the aux level you have changed the subs response to the keys or organ to the mains changing the balance and transition levels between the subs and mains.     
Title: Re: aux fed subs
Post by: Luke Geis on February 01, 2014, 10:29:56 PM
I have tooled around with different PA's and have had some results that tend to make sense and improve perceived performance. It was mentioned above, simply letting the tops run full range ( Or at least with a gentle crossover slope ) while cutting the subs with a steep filter. The big fear from most in the FULL RANGE ( no aux fed subs ) camp, is that there is an acoustic gap between tops and subs for material that does not exist in the subs. For example: The vocals may not sound as full, or the guitar may sound weak? This can be an issue for the basic user who doesn't realize that you can still add those types of channels into the subs to fill it out......... BUT.......... The idea is to not have to do that since it defeats the purpose of running aux fed subs.

It's all in the acoustical crossover point. A well measured and tuned system will have proper acoustical crossover points anyway, so there should be no fear of a hole in the audio spectrum if that's the case. Now in the instance where you are running steep filters and a not so well tuned system, there is the possibility for a large hole to appear in an aux fed sub system. Since not all instruments could be getting full extension to below their fundamental notes. Vocals have fundamental notes down to 80hz, as well as guitar and several brass and stringed instruments. In a system where the tops are crossed over at 100hz or higher with a steep filter, you could be neutering the fundamental notes for several instruments! On the converse the subs could be over extending low end content into the fundamental not range too. Subs crossed over as high as 100HZ are really pouring out the fundamental notes of many instruments and vocals and if your like most people running subs 3-6db hotter than the tops, you can really have some heat in that area.

I feel that subs should be crossed over as low as practical in an attempt to keep the fundamental notes out of that part of the system. 80-100hz is a good starting point. You want to be careful not to go too low as you start to end up with too much low end build up in the tops and psychoacoustic effects start to take place where localization of the subs makes them be unable to be localized. The idea is to have a system that is concentric and melds together into one. If people can tell that there is sub bass in the system but have no idea where it's coming from, it can be confusing and it takes away from the impact of the system. The crossover slope should be determined by the desired system tuning. It may be better on paper to have steep slopes on the subs, but it may not add up in the systems entirety?

I have found that running 12" tops that don't have extended low range can work really well not crossed over at all with an aux fed sub that is tuned to work with the tops. Smaller speakers tend to have less low end extension and the natural drop off in them can work well. Larger 15" and other 12" speakers with extended low end do not fair as well with that approach. Most 15" speakers can extend to 50hz and lower ( pretty far into sub territory ) and some 12" speakers can get down to the 50-60hz area also. These types of speakers may not work well un-filtered, where as other more controlled tops that have smaller elements will. The acoustical crossover point is where it's at. there should be a smooth transition from the tops into the subs when instruments are either in, or out of each part of the system. If a hole emerges in the frequency spectrum of key instruments and vocals, you either have to fill it in by adding that instrument into the subs, or re-tune the system. 
Title: Re: aux fed subs
Post by: Bob Kidd on February 01, 2014, 11:00:57 PM
Great advice Luke. To get a system correctly tuned in would you say a program such as Smaart is needed? Do not have program and not experienced at using it.
Title: Re: aux fed subs
Post by: Mark McFarlane on February 02, 2014, 08:48:13 AM
Great advice Luke. To get a system correctly tuned in would you say a program such as Smaart is needed? Do not have program and not experienced at using it.

If you are using vendor crossover presets for a good quality DSP, then you can probably get close with the presets.

If you are rolling your own crossovers, whether for subs or for 3 way or 4 way systems, a program that shows phase response is essential to 'do it right..  Smaart is one choice.  They are all expensive and take a bit of skill to use effectively.

An alternative is to hire someone to tune your system. Depending on where you live you may get a free volunteer.  This route is likely going to be cheaper than buying your own software. Buying your own software is a worthwhile investment if you plan to get into lots of measurements: e.g. making adjustments for venues, measuring latencies in your gear chain, testing mics,...
Title: Re: aux fed subs
Post by: Bob Kidd on February 02, 2014, 06:28:34 PM
If you are using vendor crossover presets for a good quality DSP, then you can probably get close with the presets.

If you are rolling your own crossovers, whether for subs or for 3 way or 4 way systems, a program that shows phase response is essential to 'do it right..  Smaart is one choice.  They are all expensive and take a bit of skill to use effectively.

An alternative is to hire someone to tune your system. Depending on where you live you may get a free volunteer.  This route is likely going to be cheaper than buying your own software. Buying your own software is a worthwhile investment if you plan to get into lots of measurements: e.g. making adjustments for venues, measuring latencies in your gear chain, testing mics,...


Thanks Mark,

I currently use a dbx drive rack pa, and was going to dbx 260 but did not see a preset for qsc pl380 and 340 amps. Looking for one that would have presets for the srx's and qsc pl amps.
Title: Re: aux fed subs
Post by: Greg_Cameron on February 03, 2014, 02:26:20 AM
I feel that subs should be crossed over as low as practical in an attempt to keep the fundamental notes out of that part of the system. 80-100hz is a good starting point. You want to be careful not to go too low as you start to end up with too much low end build up in the tops and psychoacoustic effects start to take place where localization of the subs makes them be unable to be localized. The idea is to have a system that is concentric and melds together into one. If people can tell that there is sub bass in the system but have no idea where it's coming from, it can be confusing and it takes away from the impact of the system.

I'm not sure what you mean here. I find the running the subs with a higher crossover point to where they can be "localized" isn't really a good thing. They can start sounding "boxy" at higher frequencies, so running them crossed lower tends to stave off that issue so long as your tops can handle reaching lower. My particular setup has the tops high passed at 60Hz (LR24) and the subs low passed ~50-55Hz. This prevents the subs from sounding boxy and makes localizing them more difficult which is a good thing since they're on the floor and the tops are flown. Since they're not really heard and more "felt," people don't bum when they're standing right in front of them when they're going full tilt boogie. Also having them crossed that low reduces the amount of combing with the tops since the wavelengths that are overlapping are relatively long. The higher you cross with separate tops and subs, the more frequencies are going comb due to the shorter wavelengths involved.

I don't like to run my tops down as low as they can go for 2 reasons: one is that you create even more unwanted overlap between the tops and subs which will result in more comb filtering of sources sent to both tops and subs; the other is that you're using up more woofer headroom in the tops which results in less overall output and more distortion. If you high pass the tops with a steeper filter, the woofer won't have to work as hard. I can get a lot more output out of my 15s high passing them at 60Hz than I can running them down to 45Hz. The subs are handling those frequencies anyway, so I want to save that headroom in the tops. A slow filter will also allow more headroom to be eaten up than I want to as well as allow for more negative interaction between the tops and subs from the larger overlap.

Anyhow, that's what works for me.
Title: Re: aux fed subs
Post by: Don Boomer on February 03, 2014, 02:41:51 PM
Picking crossover points between tops and subs will depend on what you expect from your system.  There is no single answer that works in every system. It depends on your system of course and somewhat on the music you intend to run through them.  There's a lot of room for compromise here.

I typically choose higher crossover points that other folks as what I'd like to achieve is keeping as much vocal out of the sub as possible.  Here's where going with aux fed subs really is a benefit.

But you could also choose a crossover that gives your system the flattest (or some other of your choosing) response.  That could involve asymmetrical filters.

You might also be looking from a distortion standpoint.  Usually a high pass filter to the tops will cut back on distortion (especially inter mod distortion).

I suppose if you center cluster your subs and split your tops you could end up with a crossover that plays to this.
Title: Re: aux fed subs
Post by: Greg_Cameron on February 03, 2014, 02:55:13 PM
Picking crossover points between tops and subs will depend on what you expect from your system.  There is no single answer that works in every system. It depends on your system of course and somewhat on the music you intend to run through them.  There's a lot of room for compromise here.

Agreed. On systems with less capable tops, I'll vary the high pass based on the demand of the gig. When it's less demanding, I'll lower the low pass on the tops and subs. When I need the most possible clean output, I'll bump both up a bit.
Title: Re: aux fed subs
Post by: Luke Geis on February 03, 2014, 04:00:04 PM
I'm not sure what you mean here. I find the running the subs with a higher crossover point to where they can be "localized" isn't really a good thing. They can start sounding "boxy" at higher frequencies, so running them crossed lower tends to stave off that issue so long as your tops can handle reaching lower. My particular setup has the tops high passed at 60Hz (LR24) and the subs low passed ~50-55Hz. This prevents the subs from sounding boxy and makes localizing them more difficult which is a good thing since they're on the floor and the tops are flown. Since they're not really heard and more "felt," people don't bum when they're standing right in front of them when they're going full tilt boogie. Also having them crossed that low reduces the amount of combing with the tops since the wavelengths that are overlapping are relatively long. The higher you cross with separate tops and subs, the more frequencies are going comb due to the shorter wavelengths involved.

I don't like to run my tops down as low as they can go for 2 reasons: one is that you create even more unwanted overlap between the tops and subs which will result in more comb filtering of sources sent to both tops and subs; the other is that you're using up more woofer headroom in the tops which results in less overall output and more distortion. If you high pass the tops with a steeper filter, the woofer won't have to work as hard. I can get a lot more output out of my 15s high passing them at 60Hz than I can running them down to 45Hz. The subs are handling those frequencies anyway, so I want to save that headroom in the tops. A slow filter will also allow more headroom to be eaten up than I want to as well as allow for more negative interaction between the tops and subs from the larger overlap.

Anyhow, that's what works for me.

I think you and I are saying the same thing. However with slightly different approaches? I like the subs crossed over closer to the 80hz area or lower, however in some cases they need to run up to near 100hz, or as low as 60-50hz. I do not like going any higher than that though. I don't mind running the tops out to low, but prefer to keep them right around 80-100hz. This is where most of the fundamental frequencies are for most of the important instruments and vocals. Any lower than that and you are  starting to waste energy in the tops. 80hz is where the beef of the bass guitar and the punch of the kick is. So too high of a crossover on the tops and you start to loose the impact, where as too low you start to simply waste the energy that the subs can utilize. Localization of subs is lost at around 55-50hz and 60hz is the power note for dance music ( edm at least anyway ). I alter my points based on what I hear and what smaart is telling me. I basically shot to have it sound like one big system. I have in some cases used a rather low crossover point on the subs with a more gentle slope to make that happen. I prefer center clustered subs too, so there is usually a small disconnect from the tops and subs. The subs get the most attention when working on the crossovers. I set the tops up to make them sound good throughout the venue and the subs are added in and altered based on the info and what I hear. If I can walk through any part of the venue and have no apparent separation from tops to subs, all is well.

Any system that has two sound sources producing the same thing will have comb filtering. Running tops out too low can really have some impact in areas of the venue. I like centered clustered subs for that reason. I can keep them near the 80hz area, fill the area with solid bass and reduce some of the combing in the frequency range that people tend to look for ( the kick in the chest and gut ). I prefer the higher crossovers on the tops if possible. Just depends on the venue. Sometimes it needs to be low to make it meld and sometimes it needs to be high to keep the low end junk out of them. It's all about playing with it until it's right.

Title: Re: aux fed subs
Post by: Jonathan Betts on February 03, 2014, 04:22:23 PM
I have recently started running a system where the subs are Low passed at 100Hz and the tops HP  around 130Hz. Subs are boosted +6db or so. These were recommended settings given to me by  one of their engineers. With my SRX system I would low pass my subs at 80Hz and high pass my tops around 90Hz. The subs were normally run-on a group. The new system outperforms  my SRX in every way possible running just HPF's on most channels. I'm debating whether or not to try aux or group fed subs with the SM80/TH 118 setup. If anyone has tried this can you please chime in with some info?

Thanks!
Title: Re: aux fed subs
Post by: Art Welter on February 03, 2014, 06:32:10 PM
I'm debating whether or not to try aux or group fed subs with the SM80/TH 118 setup. If anyone has tried this can you please chime in with some info?
Jonathan,

The SM80 response (without any processing) drops at around 12 dB per octave below 200 Hz.

Generally, aux fed subs are used with tops that are "full range", that is full range for most instruments other than bass, kick and low keyboards.

I'd consider the SM80 /TH 118 more of a 3 way system rather than a full range/sub combo, which could be done more effectively with a top like the SH-50 that has good response down to below 100 Hz, an octave lower.
Title: Re: aux fed subs
Post by: Jonathan Betts on February 03, 2014, 07:49:59 PM
Thanks for the response Art. Appropriate use of HPF's, depending on the music style is probably the best approach for this system?

I had a BE come through last week to use the system in a small room for a hip hop act. One SM80/TH 118. He was concerned with the way the system DSP was configured, complaining that the tops and subs would not play well together. I told him to trust me. Put some audio through the system and a smile came to his face. Drum check he was even happier. He couldn't believe the sound coming from two cabinets and one amp with minimal processing.
Title: Re: aux fed subs
Post by: Art Welter on February 04, 2014, 01:32:15 PM
Thanks for the response Art. Appropriate use of HPF's, depending on the music style is probably the best approach for this system?
Yes, for a 3 way system (as opposed to a full range system with subs) appropriate use of HPFs is the way to go.

The use of aux fed subs has grown more popular than it was in the 1970s because more people now set their systems up with a huge LF "haystack" of 6 dB or more, the equivalent of turning up every LF channel EQ 6 dB or more.

If you equalize the system flat in the LF, and add LF to the channels that you want extra LF on, a 3 way system will perform just fine.

I use a three way system with acoustical crossovers around 100 and 1000 Hz, and have no problems with "vocals in the subs", or any other "mud" problems, yet 40 Hz is often the strongest frequency level in the mix.
Title: Re: aux fed subs
Post by: Jonathan Betts on February 04, 2014, 02:04:45 PM
What is the benefit of "haystacking"subs? Isn't this why we have channel eq's? I can see maybe,   for playback music but for a live situation is this really desirable?
Title: Re: aux fed subs
Post by: Tim McCulloch on February 04, 2014, 03:06:42 PM
What is the benefit of "haystacking"subs? Isn't this why we have channel eq's? I can see maybe,   for playback music but for a live situation is this really desirable?

Not in my opinion.  I'd much rather create the sounds at the input strips than use the subwoofer level control to create the sound at the loudspeaker system.

If Robert Scovill ever repeats his Complete FOH Engineer seminar....  (ping Scovi) a participant will get a fair bit of discussion of this... but starting with a "linear response" PA (what goes in electrically is what comes out acoustically) is the way I like to present a system.  Most BEs think we need more sub until I point out the drive level is -9dB (typically) relative to the mains.  They can decide if they want to use the channel strip EQ or the sub drive, and if they don't present a problem to the system, I sit back and let them work as they see fit.
Title: Re: aux fed subs
Post by: Jay Barracato on February 04, 2014, 04:17:21 PM
Not in my opinion.  I'd much rather create the sounds at the input strips than use the subwoofer level control to create the sound at the loudspeaker system.

If Robert Scovill ever repeats his Complete FOH Engineer seminar....  (ping Scovi) a participant will get a fair bit of discussion of this... but starting with a "linear response" PA (what goes in electrically is what comes out acoustically) is the way I like to present a system.  Most BEs think we need more sub until I point out the drive level is -9dB (typically) relative to the mains.  They can decide if they want to use the channel strip EQ or the sub drive, and if they don't present a problem to the system, I sit back and let them work as they see fit.

If there ever was a topic that demonstrated the importance of compromise in system deployment, this is it.

I come in as being in agreement with Tim. Tuning the system flat and then boosting at the channel (assuming you brought enough sub) eliminates many of the reasons people give for liking aux fed subs. Vocal mics rumbling in the subs isn't a problem when the entire mix is not artificially boosted 9-12 db in the sub range at the dsp.

Basically it comes down to: there are instruments (kick and floor tom) that I want boosted in the subs, and instruments (Bass and keyboards) that I don't want boosted in the subs. I like the bass and keyboards to be mostly flat across the crossover. I think people are so into cutting eq's that they are afraid to boost, but if the system is well tuned you should be able to do both as much as you like. Therefore, many people seem to boost the subs across the board and then cut from the channels where it is too much. On the other hand, I would prefer the rig to be flatter and I can boost a couple channels as needed.

With a well designed system, this is probably a wash as to which is better. However, my experience is all too often aux fed subs are offered as an excuse for NO DESIGN. In other words,  the system tech didn't really put any thought into how the subs and mains combined. In all the rooms I have been through this seemed to be more of a problem in the medium sized rooms (say 300-700 capacity).

If the room was small, with a SOS system plus subs or a 1 over 1 stack, the distances were short enough that any crossover problems were probably minor, especially compared to room mode effects. Therefore, it was not as noticeable. In larger rooms, either the system tech got the design right or the coverage was so uneven, I basically had to pick one reference point and mix for that point. It was in the medium sized rooms (probably a small show tech/company expanding into bigger places), that I saw the greatest variance and misapplication of aux feed subs, including having no crossover at all. (That is more common than one might think.) I also think that many of those techs did not realize that the poor crossover design could affect the sound well above where that crossover was. It was not uncommon to find timing based buildups or pits anywhere from 125-250 hz depending on the slope of the crossover.

So at this point, as someone who mixes quite a bit on other peoples systems, I don't really care whether the subs are on an aux or not; I care about how the subs interact with each other and the mains.

For the record, I find myself cutting the lows in a lot of modern dance music when played through a full range system. The combination of the boost in the recording and then the boost in the system is just too much for me.

And if I didn't convince anyone away from aux fed subs, let me say, outdoors on a windy day, it is really nice to have the subs on an aux. So it is a compromise, use it when it gives yo a benefit.
Title: Re: aux fed subs
Post by: Jim McKeveny on February 04, 2014, 04:24:11 PM
The haystack tuning isn't that prevalent anymore. (Thank the stars). However, the definition of "sub" isn't particularly locked down.

Bottom octave: 20hz-40hz? This was my first exposure to the concept. Fulton J-Modular, Infinity Servo-Static, Dahlquist. (This neatly coincides with the introduction of "super" tweeters, which handled the top octave of 10khz - 20khz).

The sub-mission creeped (crept?) across a broader range, despite obvious IMD issues at all power levels.

Define  & agree on what are "sub" frequencies (as determined by acousticians, not marketers), and then we can move forward on "best practices" for mixing...





Title: Re: aux fed subs
Post by: Luke Geis on February 04, 2014, 08:01:32 PM
I completely agree with the flat system, what goes in comes out idealism. I prefer to tune the system as flat as possible too. However I am not a fan of boosting frequencies more than 3db or so. I tend to believe that if the frequency gain wasn't there to begin with, then artificially adding it ( via an active EQ filter ) will only introduce phase and distortion artifacts, albeit minimal or marginally existent? I equivocate it to photochopping....... Yes you can make the picture look better and perhaps more natural, but it's still not the original and it must not have been right to begin with. Reducing gain from the EQ filters has reduced artifacts in contrast to adding gain. Another thing to point out is that it is generally not a good idea to increase gain at an instruments fundamental frequency. Increasing 80hz to add more punch to a kick drum just tends to make it more muddy and thuddier. It also detracts from the bass guitar who's fundamental falls right there as well ( 82hz to be precise ). Decreasing gain at 80hz on the kick can make the bass stand out, or visa versa ( reducing bass guitar at 80hz can help the kick punch through ). Increasing gain at the higher harmonic frequencies can add something that can be beneficial to the mix. It can add clarity and presence that otherwise didn't exist before. But it's a slippery slope. I think many people are used to PA's that have diminished top end extension as a result of the environment and or sub par equipment and tuning. So adding a lot of high end is the means to that end. I find when the system is well tuned and flat out to about 16K and higher, I use little to no EQ and find reducing it helps bring that sweet top end into play. In most program material nothing exists beyond 16K anyway, so I tend to not worry about anything after that. But I still want to be as flat as I can be from about 40hz-20hz.

I am finding more and more these days that kick is getting heavier in the 50hz area with lots of attack ( on recordings ), but typically has a fundamental frequency of about 40hz.. A 5 string bass has a fundamental frequency of about 30hz and now with extended range guitars being more prevalent, a guitar with a low f# is reaching down to the 46hz area. I own an 8 string guitar and let me tell you that you don't need a bass guitarist with the thing........ That being said, sub systems playing music with a full 88 key piano may want to be flat down to 30hz. The low A on such a piano is 27hz! I would define a sub system to be one in which can extend down to 30hz within 3db of the rest of it's range. Is this common? No.... Is it possible? Yes..... Is it practical? Probably not most of the time. A typical rock band with no keys probably only needs a system that can get from 40hz up to 16khz. A progressive rock band with keys, and all other forms of instrumentation will want 30hz-20khz resolution. I don't think extension down to 20hz is needed. I honestly believe that extension down to 30hz, is a little over the top, but I like to have it if I can. I have a pair of SRX subs that can almost get me there.
Title: Re: aux fed subs
Post by: Jason Lucas on February 04, 2014, 09:36:13 PM
Don't forget there's more to the bass guitar than just the fundamental of the lowest note it can produce. A good bassist is going to playing a lot more notes than just the low E.

I don't concern myself with fundamental frequencies, I simply try to make the bass sound as balanced as I can.
Title: Re: aux fed subs
Post by: Tim McCulloch on February 04, 2014, 09:44:22 PM
I completely agree with the flat system, what goes in comes out idealism. I prefer to tune the system as flat as possible too. However I am not a fan of boosting frequencies more than 3db or so. I tend to believe that if the frequency gain wasn't there to begin with, then artificially adding it ( via an active EQ filter ) will only introduce phase and distortion artifacts, albeit minimal or marginally existent?

{big ol' snip}


"Flat" is not the same as "linear."  Scovi also spends some time driving home that concept.  That the terms have been incorrectly used as synonyms makes that a task of re-education.
Title: Re: aux fed subs
Post by: Jay Barracato on February 05, 2014, 07:55:25 AM
"Flat" is not the same as "linear."  Scovi also spends some time driving home that concept.  That the terms have been incorrectly used as synonyms makes that a task of re-education.

I guess I first stuck in "flat" when I meant "linear" but my mental picture includes a line that is higher at lower frequencies but with no hump as "flat", but honestly, just like with the post trying to define "Sub" as the lowest octave which may have worked when it was 50-100, but is different now that 30-60 is more common, I am more concerned with what a system does rather than what someone calls it.
Title: Re: aux fed subs
Post by: Per Sovik on February 06, 2014, 06:14:28 AM
When I'm able to, I run "aux fed subs" for one reason only; to keep some microphones totally disconnected from the subs. What I run is more what one would call group fed subs, I send the channels that needs subs to a group, and feed the subs from that group.
Anything that goes to the subs will be as aligned (or not) as the system is, so there are no issues there.
The vocals and other non-sub instruments will go straight to the full range tops, so there is no lack of fullness if that's required.
I do crossover between subs and tops quite high when using "single hang" (no I don't have two line arrays, so most of the time it is single or double tops) mode, this to avoid working the tops hard in the lower register when they are to reproduce vocals.
It seems to work, only problem really is that most mixers I've seen doesn't let the Master fader control the 5-6 channels of separated output streams that my setup produces.
Title: Re: aux fed subs
Post by: Jean-Pierre Coetzee on February 06, 2014, 09:02:45 AM
When I'm able to, I run "aux fed subs" for one reason only; to keep some microphones totally disconnected from the subs. What I run is more what one would call group fed subs, I send the channels that needs subs to a group, and feed the subs from that group.
Anything that goes to the subs will be as aligned (or not) as the system is, so there are no issues there.
The vocals and other non-sub instruments will go straight to the full range tops, so there is no lack of fullness if that's required.
I do crossover between subs and tops quite high when using "single hang" (no I don't have two line arrays, so most of the time it is single or double tops) mode, this to avoid working the tops hard in the lower register when they are to reproduce vocals.
It seems to work, only problem really is that most mixers I've seen doesn't let the Master fader control the 5-6 channels of separated output streams that my setup produces.
Do something similar to this on the SC48 and I suppose most digital consoles. Mains on L+R and then Subs on mono... Assign what you need on the subs to mono and then everything else as well as that to L+R...

We crossover subs pretty low as well so that it just gives us punch and nothing more.