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[AllenDeneau]

I'm needing some help or explaining in regard to setting limiters particularly on my subs. I'm not new to audio but not as experienced as I'd like to be when dialing in a system for maximum performance.

Here's the rig:
4 x Peavey SP2G mains -  Power handling (300/600/1200)
6 x Peavey SP118's subs - Power handling (350/700/1400)
4 x QSC PLX 3402's - Power 700 @ 8/ 1100 @ 4
2 x QSC CX502's
1 x Peavey VSX26 DSP

Here is the manual to my subs http://assets.peavey.com/literature/manuals/80304323.pdf   however I have 2 that are the 4 ohm version and 4 that are 8 ohms. Identical basket model with exception of the resistance.

I've not setup my system for 3 way operation yet until I get a good grasp on setting these limiters as my 502's will be for the horns and have more power than my horns need.

Setup is: (until I get another 3402 for the subs)
3402 - SP2 / SP2
3402 - SP2 / SP2
3402 - SP118(8ohm) SP118(8ohm) / SP118(8ohm) SP118(8ohm)
3402 - SP118(4ohm) / SP118(4ohm)

I started with the SP2/118 preset for the VSX26 from Peavey's website.

The Peavey preset says my sub settings should be:

X-Over
Low corner freq - 45Hz Slope = Bessel 24
Upper corner - 110Hz   Slope = LR 24
Gain +2dB

Eq
80Hz +4.5dB .700 bandwidth
120Hz +3.5dB .600 bandwidth

The mains I'm not very concerned with as I have them at -6dB on the x-over to keep a good balance and overall they sound pretty good after some very creative eq'ing. However, once I'm sure I'm doing everything correct I will absolutely re-set the limiters there as well.

I don't have a SMAART rig so all settings have been by ear and or using factory numbers and math. Overall I think the system sounds pretty good however the issue I'm having is the lows quickly run out of steam and start to bottom out before they're thumping. I do understands this is not a top tier system and it's nearly 20 years old and those subs don't go super low or loud  but I do believe they should hit a little harder.

My first question is: my spec sheet says the -3dB point is 48Hz and the -10dB point is 38Hz but the peavey preset is saying it should be 45Hz. I'm fairly certain these system settings were measured at Peavey using a newer version of the SP118 so that probably needs to be raised to 45Hz on my DSP I believe.

My next question/issue is the limiter settings for my subs...

Doing the math for setting the RMS limiter of the VSX. (only has RMS limiting) (the 3402's are 40x gain)
20log (((SQRT(Watts x Resistance))/Gain)/.775)
20log (((SQRT(350 x )/40/).775)
20log((SQRT(2800)/40/).775)
20log((52.915)/40)/.775)
20log((1.323)/.775)
20log(1.71)
4.65

So according to the math, assuming it's correct my limiter should be set to start engaging at 4.65dB input. Ok that's fine except by the time they engage I'm bottoming out the driver and the clip light on the 3402 is lighting. That's putting music thru a board and the main outs just tickling the 0dB light.

I've found that to keep the subs from distorting and bottoming out my limiter needs to be set at -4dB.

So here are the questions I have regarding the setting of the limiters.

1. Is the low corner frequency difference of 3Hz causing all or part of the issue?
2. When RMS limiters are set (properly) should you see the clip light on the amps if you're staying under 0dB on the board and the channel isn't above 0dB as well?
3. Am I misinterpreting the math and the 4.65 number means a reduction in gain rather than the actual dB setting? My VSX says it has +24dBu outputs so I'm taking the math I've done to represent the actual output level rather than a reduction of 4.65dB, is that correct thinking?
4. Is my math correct?

I have a small version of my rig setup in the garage sp2 over sp118 per side and even standing within 10 feet of the system it gets loud but still not a lot of punch. I know they used to hit a lot harder, at least I believe I remember them hitting harder. The baskets are pretty new and have not been run hard so I don't think they're the issue, maybe but I don't think so.

The time I am remembering them hitting herder they used to be run off of Peavey GPS3500's, can switching to the PLX3402's actually make a difference? I know the switching amps are sometimes said to be inferior on subs because they don't "store" power for those big hits but is that true?

Anyway, any and all help will be appreciated. I really want to get better at the math and science of a sound system rather than just being able to mix well.

Thanks. If there's anything I missed just ask and I'll answer as best I can.

[Paul G. OBrien]

Ok I got a few comments. The drivers in these subs aren't much of a subwoofer by todays standards so you're not going to be able to put a lot of power into them without bottoming. I also have trouble with the PV recommended EQ... +4.5dB at 80hz? This box already has a response peak at around 80hz so why would they want to make that even more pronounced? I say ditch those boosts and if anything boost just above the tuning frequency where cone excursion is at a minimum, this will flatten response overall and should sound better.

[AllenDeneau]

Ok I got a few comments. The drivers in these subs aren't much of a subwoofer by todays standards so you're not going to be able to put a lot of power into them without bottoming. I also have trouble with the PV recommended EQ... +4.5dB at 80hz? This box already has a response peak at around 80hz so why would they want to make that even more pronounced? I say ditch those boosts and if anything boost just above the tuning frequency where cone excursion is at a minimum, this will flatten response overall and should sound better.

Thanks Paul, I agree with you're assessment regarding not being a sub driver. You actually helped me with some modeling and such a while back. This rig doesn't get used much as I'm on other people's gear typically but I really want to get it dialed in to use.

I believe you actually modeled the enclosure with a Peavey low rider, with the pot tube removed, would work well in the existing box, correct?

I also agree that the tuning on the preset seemed a bit odd for the Sp118 and have tweaked a bit but the problem is, neighbors are always home and I can run the system hard at all before it gets annoying...

Can you explain more about boosting just above the running frequency and minimum cone excursion?

The 120Hz boost gives the sub a bloated sound for sure. I found a slight bump at about 60Hz or so gives a good thump but I'm afraid that too much boost will result in being able to send more power and reduce the overall output even more..

I really want to understand more about enclosure design and tuning.

[Paul G. OBrien]

Can you explain more about boosting just above the running frequency and minimum cone excursion?

The 120Hz boost gives the sub a bloated sound for sure. I found a slight bump at about 60Hz or so gives a good thump but I'm afraid that too much boost will result in being able to send more power and reduce the overall output even more..

I really want to understand more about enclosure design and tuning.

Here is a cone excursion plot of a driver in an enclosure tuned to 45hz with 500w applied, notice that excursion is at a minimum at tuning frequency and a maximum at about 70hz. All drivers behave this way in a ported enclosure so that is why the PV tunings are so puzzling, the driver will take more power at or just above tuning frequency but not in the middle of it's pass band.. assuming a typical 30-90hz pro sound sub operating range. Now I don't suggest boosting at the tuning frequency by default I just suggest it if your subs are lacking output a bit at the very low end, if they have a relatively flat response then there is no need and I generally try to target a flat response as it will sound more musical.

[AllenDeneau]

Here is a cone excursion plot of a driver in an enclosure tuned to 45hz with 500w applied, notice that excursion is at a minimum at tuning frequency and a maximum at about 70hz. All drivers behave this way in a ported enclosure so that is why the PV tunings are so puzzling, the driver will take more power at or just above tuning frequency but not in the middle of it's pass band.. assuming a typical 30-90hz pro sound sub operating range. Now I don't suggest boosting at the tuning frequency by default I just suggest it if your subs are lacking output a bit at the very low end, if they have a relatively flat response then there is no need and I generally try to target a flat response as it will sound more musical.

Thanks for the explanation Paul. All subs display the same behavior or similar?

So for my SP118, it's box tuning is 36Hz and the -3dB point is 48Hz, wouldn't boosting anything below 48Hz be asking for trouble?

I downloaded winISD, .44, and entered my driver info and then designed a box to match mine but it won't let me put vent length in, it just asks for diameter and then in vent length it says too short and it's grayed out???

I entered the box dimensions and subtracted 1.5" for each dimension to account for the wood thickness and came up with 17,847.27 squared inches but it's saying the "needed volume" is 117847.3?

Not to mention, I really have no clue as to what I'm looking at...

Is this program accurate, can it give me some good starting points for system tuning without using SMAART?


Any insight into the limiter issue?

Thanks

[John Roberts {JR}]

Thanks for the explanation Paul. All subs display the same behavior or similar?

So for my SP118, it's box tuning is 36Hz and the -3dB point is 48Hz, wouldn't boosting anything below 48Hz be asking for trouble?

I downloaded winISD, .44, and entered my driver info and then designed a box to match mine but it won't let me put vent length in, it just asks for diameter and then in vent length it says too short and it's grayed out???

I entered the box dimensions and subtracted 1.5" for each dimension to account for the wood thickness and came up with 17,847.27 squared inches but it's saying the "needed volume" is 117847.3?

Not to mention, I really have no clue as to what I'm looking at...

Is this program accurate, can it give me some good starting points for system tuning without using SMAART?


Any insight into the limiter issue?

Thanks

Have you tried asking Peavey service? The engineers who designed the cabinets may have some useful advice if the service guys can't help you.

JR

[Paul G. OBrien]

All subs display the same behavior or similar?

What drivers do you have again? Peavey made so many of these 18's over the years..

[AllenDeneau]

What drivers do you have again? Peavey made so many of these 18's over the years..

John, honestly I hadn't even thought about that, great suggestion, thanks.

Paul, they're the 1801-8 LT BW

Here's the manual to my sub except mine are 8 ohms. http://assets.peavey.com/literature/manuals/80304323.pdf

The port is 8" in diameter and 4.5" long

[Paul G. OBrien]

OK I managed to model this cabinet again with that driver and it looks like the model agrees with the response published in the pdf. I had to manually enter the box volume and port dimensions as the software wanted something totally different. The green trace is the driver without any processing and the yellow trace is with a low cut filter and a boost just below tuning where excursion is at a minimum. Notice what that does to the response, it pushes the -3dB point lower and flattens the low freq response without impacting the drivers overall power handling.

[AllenDeneau]

OK I managed to model this cabinet again with that driver and it looks like the model agrees with the response published in the pdf. I had to manually enter the box volume and port dimensions as the software wanted something totally different. The green trace is the driver without any processing and the yellow trace is with a low cut filter and a boost just below tuning where excursion is at a minimum. Notice what that does to the response, it pushes the -3dB point lower and flattens the low freq response without impacting the drivers overall power handling.

Cool, thanks for doing that Paul. I'm looking at it and it looks good however I have a couple questions.

1. I see it's showing on the bottom right that the box tuning is 41.68 but my sub is tuned to 36 per the manual?
2. I looked at your filters and se you have a high pass set at 37Hz with a BW 24? These subs were bottoming out before hitting the limiters with a low corner of 45Hz, will flattening the 80Hz and 120Hz bumps, which aren't necessary it seems, keep them from bottoming out while I boost the 40Hz you did?

I really wish I had a SMAART system to measure this system as I'm positive that the peavey preset is for a newer version of the SP series.

I moved the X-Over point to 95Hz for the sub, they've always sounded better there, to me, than higher. That also takes the 120Hz bump out of the equation, well mostly. What I found interesting is even with the 95Hz X-Over point and the tops muted, when I put a 250Hz sine wave thru the system, it's still fairly audible in the subs? The upper X-Over slope is a LR24, shouldn't that be all but killing the 250Hz tone? Isn't 250Hz an octave and a half higher than 95Hz? If that's correct then the signal reduction should be near 36dB an octave and a half higher, correct?

The more I learn, the more I have questions...

[Paul G. OBrien]

1. I see it's showing on the bottom right that the box tuning is 41.68 but my sub is tuned to 36 per the manual?

Well... I thought I read in your earlier thread about upgrading these boxes that the port was 8" diameter and 4.5" long.. was that right? And I think we figured the box was about 7.5cu ft internal after factoring in the volume displaced by the port, driver, and the foam cube?

2. I looked at your filters and see you have a high pass set at 37Hz with a BW 24? These subs were bottoming out before hitting the limiters with a low corner of 45Hz, will flattening the 80Hz and 120Hz bumps, which aren't necessary it seems, keep them from bottoming out while I boost the 40Hz you did?

Yes get rid of those boosts and definitely put in a low cut filter, again I have to point you back to the earlier graph showing cone excursion, it is at a maximum right around 60-70hz so it is those frequencies not the lower tones near box tuning that will cause the most cone deflection. You can see this yourself with a tone generator, drive the subs with a relatively low signal level and watch the cone move.

I really wish I had a SMAART system to measure this system as I'm positive that the peavey preset is for a newer version of the SP series.

  Do you have a measurement mic? If so download a copy of REW(free) and do some measurements.. http://www.roomeqwizard.com/

I moved the X-Over point to 95Hz for the sub, they've always sounded better there, to me, than higher. That also takes the 120Hz bump out of the equation, well mostly. What I found interesting is even with the 95Hz X-Over point and the tops muted, when I put a 250Hz sine wave thru the system, it's still fairly audible in the subs? The upper X-Over slope is a LR24, shouldn't that be all but killing the 250Hz tone? Isn't 250Hz an octave and a half higher than 95Hz? If that's correct then the signal reduction should be near 36dB an octave and a half higher, correct? The more I learn, the more I have questions...

Yeah I have a set of powered subs with a non adjustable 120hz crossover and they sound a bit muddy, I definitely like them better when externally processed with a 80-90hz crossover. And yeah with the tops muted you will hear lots of content well outside the passband, these filters aren't brick walls but that is OK.. don't let that bother you too much.. steeper filters have their pitfalls too.

[chuck clark]

Hi Allen!  Your in good company- Einstein once said "the larger the island of knowledge -the longer the shoreline of wonder."

If I recall from lots of experimenting in the eighties with a huge "Pile O Peavey" PA  we settled on a ratio of at least 2 subs for each top. 3 is even better if you like big low end, so you need to get another pair of subs.
   The 250 hz thing I've noticed also. Think "loudness curves". The fact is, as much as engineers like to talk about "flat" response, the human ear is not flat at all.  We are much more sensitive to 250 hz than 90 hz so even though it is many db down in response it will still appear to be there if other program material is not present to "mask" it.  uh-oh, there's ANOTHER fact about human hearing that lots of "soundguys" are oblivious to. 
  So:  1. your intuitive setting of the limiter just below the clip point of the amps is correct no matter what the charts say.  2. I always found the lower xover point to sound better also. In fact I've gone even lower to 80 hz. The SP-2 tops will handle down to 60 hz pretty well so no issues there.  3. Yes, flatten those bumps in eq @ 80 and 120.  In fact I've had a 6db dip at 120 really help in cleaning up a "bonky" sounding kick drum before.  4. Theory is the best place to start but good sounding results trumps theory no matter how many questions it raises or how many times it sends the engineers back to the drawing board. Lol  5. lastly, as an almost exact copy of a Crest amp the GPS is indeed a wonderful amp, but the PLX 3402 is no slouch either. I would expect any differences between the two (other than weight) to be nit picking.
Have a super day!
Chuck

[AllenDeneau]

Well... I thought I read in your earlier thread about upgrading these boxes that the port was 8" diameter and 4.5" long.. was that right? And I think we figured the box was about 7.5cu ft internal after factoring in the volume displaced by the port, driver, and the foam cube?

It was discussed but I didn't do it. I don't get to use this system much so I couldn't see spending the money to upgrade them yet. I'd love to explore it again though, the biggest issue I have is truly understanding what's happening within them and knowing what to do and what not to do. The subs are completely stock currently.

Yes get rid of those boosts and definitely put in a low cut filter, again I have to point you back to the earlier graph showing cone excursion, it is at a maximum right around 60-70hz so it is those frequencies not the lower tones near box tuning that will cause the most cone deflection. You can see this yourself with a tone generator, drive the subs with a relatively low signal level and watch the cone move.

I did kill those boosts. Will your boost and high pass filter suggestion stay the same with a different box tuning frequency? With the Peavey VSX I have a HPF 6 and a HPF 12 with Q adjustment. I have the VSX GUI interface but I've been warned that what the software shows is not always completely accurate, a reason for them abandoning it. Anyway, I set the HPF12 at 40Hz with a Q of .75 and it shows my -6dB is right at 30Hz, I'm thinking I need to move it up a bit? It seems that all the boosting is happening below my -10dB point of 38Hz, is that correct?

 

Do you have a measurement mic? If so download a copy of REW(free) and do some measurements.. http://www.roomeqwizard.com/

Sadly no, I sold it with my DRPA and never replaced it. Need to soon.

Yeah I have a set of powered subs with a non adjustable 120hz crossover and they sound a bit muddy, I definitely like them better when externally processed with a 80-90hz crossover. And yeah with the tops muted you will hear lots of content well outside the passband, these filters aren't brick walls but that is OK.. don't let that bother you too much.. steeper filters have their pitfalls too.

I guess I never really paid any attention to it before, weird. Would there be any benefit or protection offered if I added a LPF to the subs passband?

[AllenDeneau]

Hi Allen!  Your in good company- Einstein once said "the larger the island of knowledge -the longer the shoreline of wonder."

If I recall from lots of experimenting in the eighties with a huge "Pile O Peavey" PA  we settled on a ratio of at least 2 subs for each top. 3 is even better if you like big low end, so you need to get another pair of subs.
   The 250 hz thing I've noticed also. Think "loudness curves". The fact is, as much as engineers like to talk about "flat" response, the human ear is not flat at all.  We are much more sensitive to 250 hz than 90 hz so even though it is many db down in response it will still appear to be there if other program material is not present to "mask" it.  uh-oh, there's ANOTHER fact about human hearing that lots of "soundguys" are oblivious to. 
  So:  1. your intuitive setting of the limiter just below the clip point of the amps is correct no matter what the charts say.  2. I always found the lower xover point to sound better also. In fact I've gone even lower to 80 hz. The SP-2 tops will handle down to 60 hz pretty well so no issues there.  3. Yes, flatten those bumps in eq @ 80 and 120.  In fact I've had a 6db dip at 120 really help in cleaning up a "bonky" sounding kick drum before.  4. Theory is the best place to start but good sounding results trumps theory no matter how many questions it raises or how many times it sends the engineers back to the drawing board. Lol  5. lastly, as an almost exact copy of a Crest amp the GPS is indeed a wonderful amp, but the PLX 3402 is no slouch either. I would expect any differences between the two (other than weight) to be nit picking.
Have a super day!
Chuck

Hi Chuck, thanks for the response. Wish I could speak as eloquently as Einstein.

Yeah I agree that it takes a big low to high ratio with these for sure. I do own 6 of these subs fortunately.

Yeah the 250 thing was weird but none the less, a learning opportunity.

Can you talk more about the limiters? It sure seems my subs are coming apart far before reaching the limiter threshold. Is my math correct? I believe it is but mistakes can easily happen.

I too have run these with a much lower x-over point and liked it, I was really just trying to give the preset a chance to see if it sounded better or worse than what I dialed in before. The biggest problem with dropping my x-over point any lower right now is, I run out of eq filters to smooth out the SP2. I'm currently running the system bi-amped and with each passband I only have 5 filters. To get the horns smooth and the boxiness out of the SP2 I've used all 5, very creatively I must add, lol.

Yeah, the 100-160 area can so quickly just get overwhelming IMO.

I don't mind the practice and going back to the drawing board as long as I'm actually learning along the way and not just taking stabs in the dark.

I really did love those GPS amps, everything but the weight. I didn't think it's the PLX causing the issue, unless I run it into clipping. Maybe this is all just due to my ear being refined over the years with bigger and more capable systems I'm hearing and working with.

Any more insight you can offer would be much appreciated.

Thanks.

[Paul G. OBrien]

Will your boost and high pass filter suggestion stay the same with a different box tuning frequency?

The net internal box volume and port dimensions determine the box tuning so yeah the processing will be different if we aren't using the correct figures for the calculations.

I set the HPF12 at 40Hz with a Q of .75 and it shows my -6dB is right at 30Hz, I'm thinking I need to move it up a bit? It seems that all the boosting is happening below my -10dB point of 38Hz, is that correct?

No it's centered at 40hz.
 

Would there be any benefit or protection offered if I added a LPF to the subs passband?

That is what the crossover does, it puts a lowpass on the subs and a highpass on the tops.

[AllenDeneau]

The net internal box volume and port dimensions determine the box tuning so yeah the processing will be different if we aren't using the correct figures for the calculations.

How close do you think I can get estimating by taking the physical dimensions of the box, subtracting .75" per side for material thickness? There's not a ton of bracing within the box if I recall correctly. It has a small upside down U shaped structure in the bottom to hold the speaker pole. Maybe these pics help?

No it's centered at 40hz.

Ok, still learning how all the math and science works, gets a bit confusing.

 

That is what the crossover does, it puts a lowpass on the subs and a highpass on the tops.

Right, I was just wondering if my subs could operate more efficiently if I added another LPF thru the EQ settings to help filter stray signal, kind of just thinking out loud really.

[Paul G. OBrien]

How close do you think I can get estimating by taking the physical dimensions of the box, subtracting .75" per side for material thickness?

That will do it but 30 seconds with a tape measure once the driver is out and you have the numbers you need.

Right, I was just wondering if my subs could operate more efficiently if I added another LPF thru the EQ settings to help filter stray signal, kind of just thinking out loud really.

No.. it'll just mess up phase at the crossover, the fewer number of filters you can use to do a job the better in that regard.

[chuck clark]

Hi Chuck, thanks for the response. Wish I could speak as eloquently as Einstein.

Yeah I agree that it takes a big low to high ratio with these for sure. I do own 6 of these subs fortunately.

Yeah the 250 thing was weird but none the less, a learning opportunity.

Can you talk more about the limiters? It sure seems my subs are coming apart far before reaching the limiter threshold. Is my math correct? I believe it is but mistakes can easily happen.

I too have run these with a much lower x-over point and liked it, I was really just trying to give the preset a chance to see if it sounded better or worse than what I dialed in before. The biggest problem with dropping my x-over point any lower right now is, I run out of eq filters to smooth out the SP2. I'm currently running the system bi-amped and with each passband I only have 5 filters. To get the horns smooth and the boxiness out of the SP2 I've used all 5, very creatively I must add, lol.

Yeah, the 100-160 area can so quickly just get overwhelming IMO.

I don't mind the practice and going back to the drawing board as long as I'm actually learning along the way and not just taking stabs in the dark.

I really did love those GPS amps, everything but the weight. I didn't think it's the PLX causing the issue, unless I run it into clipping. Maybe this is all just due to my ear being refined over the years with bigger and more capable systems I'm hearing and working with.

Any more insight you can offer would be much appreciated.

Thanks.

If your subs are "coming apart" before hitting the limiter threshold they are most likely hitting the limits of their linear excursion.  Are you familiar w/ the theile small parameter -X-max?  Here's an interesting bit of info for you:  Since the area of the moving piston of the cone remains constant, the only way to reproduce lower (longer wavelength) tones at equal volume to higher (shorter wavelength) tones is through increased excursion. To reproduce equal volume an octave lower requires 4X the excursion for a given cone size. One reason bass reflex designs are so popular is they help limit this excursion by loading the pressure energy off the backside of the cone in with the pressure from the front side. This reaches it's peak effect at the tuned frequency of the box/port/driver unit. This additional cone excursion controlling output is welcome and sounds pretty great, but.....Warning!  Exactly 1 octave BELOW the tuned frequency that helpful back pressure wave is now 180 degrees out of phase and UNloads the cone allowing for crazy flopping back and forth and even bottoming of the voice coil against the backplate of the poor driver. Can you say major failure mode? Sure, I knew you could. Lol, thus the popularity and real necessity for a carefully set high pass filter about 1/2 octave below the tuned frequency of hard driven
bass reflex boxes.  Especially older relatively short x-maxx drivers like old Peavey speakers.  While Black Widows had a robust magnet/ voice coil assembly they were a bit late to the deep x-maxx thing.  So you might want to try a new set of lo-rider's which have about double the x-maxx of the old style Black Widows.
Hope this helps you out!
Chuck

[AllenDeneau]

That will do it but 30 seconds with a tape measure once the driver is out and you have the numbers you need.

True. I'll see if I can get into one sometime soon and get some numbers.

No.. it'll just mess up phase at the crossover, the fewer number of filters you can use to do a job the better in that regard.

Yeah, makes sense.

[AllenDeneau]

If your subs are "coming apart" before hitting the limiter threshold they are most likely hitting the limits of their linear excursion.  Are you familiar w/ the theile small parameter -X-max?  Here's an interesting bit of info for you:  Since the area of the moving piston of the cone remains constant, the only way to reproduce lower (longer wavelength) tones at equal volume to higher (shorter wavelength) tones is through increased excursion. To reproduce equal volume an octave lower requires 4X the excursion for a given cone size. One reason bass reflex designs are so popular is they help limit this excursion by loading the pressure energy off the backside of the cone in with the pressure from the front side. This reaches it's peak effect at the tuned frequency of the box/port/driver unit. This additional cone excursion controlling output is welcome and sounds pretty great, but.....Warning!  Exactly 1 octave BELOW the tuned frequency that helpful back pressure wave is now 180 degrees out of phase and UNloads the cone allowing for crazy flopping back and forth and even bottoming of the voice coil against the backplate of the poor driver. Can you say major failure mode? Sure, I knew you could. Lol, thus the popularity and real necessity for a carefully set high pass filter about 1/2 octave below the tuned frequency of hard driven
bass reflex boxes.  Especially older relatively short x-maxx drivers like old Peavey speakers.  While Black Widows had a robust magnet/ voice coil assembly they were a bit late to the deep x-maxx thing.  So you might want to try a new set of lo-rider's which have about double the x-maxx of the old style Black Widows.
Hope this helps you out!
Chuck

Thanks Chuck, I didn't know it took 4x the excursion to go an octave lower, interesting.

I definitely understand that the bottoming out is happening when they're moving further than their capable of and at a higher amplitude. What's got me perplexed is, as I see it anyway, I've got one or more of 3 things happening.

1. My DSP settings aren't correct
2. I've got the DSp settings correct however the action of the VSX26 DSP unit isn't as precise as needed
3. My VSX26 is malfunctioning.

Those may not be correct assumptions or there may be others and more but from what I understand, which seems like nothings some days, those are the 3 most plausible issues.

The VSX26 has RMS limiting so I understand that with a very quick spike in output the limiter won't protect the driver such as a brick wall limiter. However, with the high pass filter set, as well as a steep roll off on the low corner point of the X-Over for the subs, at the correct frequency, shouldn't that limit the mechanical excursion of the driver keeping it from bottoming out? Going back to my above three theories that if I'm set with the correct numbers nothing lower than what my sub should be able to handle should come thru correct?

Here's something I'm unsure of: If my RMS limiter is set correctly and judiciously, should I ever see the clip lights on my amps IF the increase in amplitude is gradual?

I know I'm missing some information and understanding so please bear with me. I have a Peavey VSX26 running into PLX 3402's. I have the clip limiter engaged on all amps. So if my RMS limiters are set correctly, I should never see the clip light on the amp should I? Here's the info about the PLX clip limiter switch

"When the audio signal drives the
amp's output circuit beyond its power
capability, it clips, flattening the peaks
of the waveform. The clip limiter
detects this and quickly reduces the
gain to minimize the amount of
overdrive. To preserve as much of the
program dynamics as possible, limiting
occurs only during actual clipping."

I think I may be starting to understand why I'm seeing the clip lights EVEN with proper DSP settings. My VSX does RMS limiting and the limiter is set for 350w RMS to match my subs power handling capability. While RMS limiting will keep the music program from constantly driving the amps to clip, thus RMS, since I don't have brick wall limiting and if I'm near the or even in the RMS limiters, a peak may quickly come thru sending more voltage than the amp input can handle therefore causing the clip light to engage on the amp. Is that close to what's happening?

[David Morison]

The VSX26 has RMS limiting so I understand that with a very quick spike in output the limiter won't protect the driver such as a brick wall limiter. However, with the high pass filter set, as well as a steep roll off on the low corner point of the X-Over for the subs, at the correct frequency, shouldn't that limit the mechanical excursion of the driver keeping it from bottoming out? Going back to my above three theories that if I'm set with the correct numbers nothing lower than what my sub should be able to handle should come thru correct?

Here's something I'm unsure of: If my RMS limiter is set correctly and judiciously, should I ever see the clip lights on my amps IF the increase in amplitude is gradual?

I know I'm missing some information and understanding so please bear with me. I have a Peavey VSX26 running into PLX 3402's. I have the clip limiter engaged on all amps. So if my RMS limiters are set correctly, I should never see the clip light on the amp should I?

I think I may be starting to understand why I'm seeing the clip lights EVEN with proper DSP settings. My VSX does RMS limiting and the limiter is set for 350w RMS to match my subs power handling capability. While RMS limiting will keep the music program from constantly driving the amps to clip, thus RMS, since I don't have brick wall limiting and if I'm near the or even in the RMS limiters, a peak may quickly come thru sending more voltage than the amp input can handle therefore causing the clip light to engage on the amp. Is that close to what's happening?

I don't know about the VSX in particular so you'll need to check the manaul but many limiters have an attack time which determines how quickly they kick in. It may be adjustable by the user in some models or set by the unit itsself depending on your other parameters. "RMS" limiting is often (albeit not necessarily always) used to refer to slightly longer term limiting than Peak, so absent a manual telling me otherwise I would assume that short term peaks of higher level absolutely can get through, and only slightly longer term trends would activate the RMS limiter.

So, short answer, yes you probably still can get your amps' clip lights on with your current RMS limiter settings.

HTH,
David.

[AllenDeneau]

I don't know about the VSX in particular so you'll need to check the manaul but many limiters have an attack time which determines how quickly they kick in. It may be adjustable by the user in some models or set by the unit itsself depending on your other parameters. "RMS" limiting is often (albeit not necessarily always) used to refer to slightly longer term limiting than Peak, so absent a manual telling me otherwise I would assume that short term peaks of higher level absolutely can get through, and only slightly longer term trends would activate the RMS limiter.

So, short answer, yes you probably still can get your amps' clip lights on with your current RMS limiter settings.

HTH,
David.

Hey David, yes the VSX does have an attack and release time for it's limiting. I've got it set to a pretty quick attack and release so I think I just may be at the threshold of the limit of my system and while the RMS limiters are doing their thing, some quick peaks are getting thru and engaging the clip limiter in the amp.

Thanks.

[AllenDeneau]

Ok, I've been a bit busy to get here but I finally have some time to share what the system did last time it was out.

Paul, Chuck and David... Thank you for taking the time to help me gain a "better" understanding of sub limitations, tuning and powering. Your advice has been a HUGE help, though I'm sure I'm not done asking questions, LOL.

So a couple of weekends ago I was hired to do some freelance work for a national cheer event. I was then asked if my system was available also, they needed another rig. It was and I brought a pair of SP2's and SP118's per side. The room was a HUGE hall of nearly 45,000 sq ft of open space made of concrete and pillars. Only after I had set up did we discover that another pair of tops to cover the sides and back of the stacks was needed as there were cheer teams all over the place. See the pics for the space.

So here is what I did and what I had as results.

As per the suggestions I flattened the 80Hz and 120Hz bumps. I tried a boost at 40Hz but that seemed a bit low as any real power would cause it to bottom out. I moved up the boost and it landed near 55Hz. I also had a small boost at 65Hz but I don't remember setting that in there....

I moved the X-Over point to 95Hz and it was a really good balance. Because the VSX is a bit noisy with my amp's at wide open, I dialed my amps back a bit and boosted the outputs on the VSX and the hiss was greatly reduced. The passbands were set like this: Low was +4 boost and the highs (bi-amp system only) were -2 cut, the balance again was pretty good.

I think I'm pretty close to where I need to be with the limiters. I had them set for another person running the  system and they can put their foot thru the floor and the system will be alright. Still wish I also had a Peak limiter within the DSP.

The room had a ton of 50Hz, 250Hz and 1kHz energy. Overall I'm pretty happy with the mains and my eq'ing however I wish I had dynamic eq's available as most know, when Peavey SP2's get ramped up they can get harsh. Low to medium volume the horns sound great however, I'd need more high cuts for them to be that smooth when running medium to high output. Maybe that'll be a reason to buy a waves soundgrid and run a dynamic eq on the LR buss, lol.

In that room, in retrospect, I think I would have been better served to not boost the 55Hz and drop the passband down a couple dB's for an even better sound. The added low end didn't hurt as these teams want thump anyway but to me, I like a very even sound and the lows were quite prominent.

I didn't have much option in deployment and as a result I had a HUGE power alley as the subs were paired 2 per side and split over 50' apart from Left to Right. Again, not the worst thing in the world but more even coverage would've been nice. It would've looked weird, but maybe I could've put all 4 subs together on one side for a more single source point, not sure...

I measured the output while playing some bumper music between sessions. I was dead center about 60' into the audience and the rig measured 97dBc but the 50Hz output was HUGE. 101dB at that location, again, right smack dab in the middle of the power alley. Move to the sides and the response was much better. The room was certainly a contributing factor as well. I believe there was another 3 or 4 dB left before limiters. I'll take that with this old system.

Here's what I noticed that was a bit puzzling. The subs actually hit harder behind them than in front of them. The backs of the subs were over 60' away from a solid back wall and at least 25' away from the pipe and drape upstage so I wouldn't think I was getting any boundary effect correct? Any ideas or suggestions?

I really need to find a spot outside in a wide open area to set the system up and run it to get the eq's set for the boxes. Trying to do it in a room has been a difficult task for me.

I've had renewed faith in this older system, that for many bands/events it is just fine though there is much more capable gear out now. I'm seriously considering doing the Low Rider upgrade as Paul had suggested and see where this system can go.

I'm frustrated but having fun while trying to improve at system tuning. With all your help, maybe someday I'll be less frustrated and be pretty good at it.

Thanks all.

[ProSoundWeb Community]