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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 I'm fairly certain these system settings were measured at Peavey using a newer version of the SP118 so that probably needs to be raised to 45Hz on my DSP I believe.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...

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