Print Page - Modify Peavey SP4's?

I've got a pair of Peavey SP4's (circa 2004). According to Peavey they are a "quasi" 3-way box, where the bottom 15" runs from 50 hz to 900 hz and the top 15" runs from 50-1800 hz. using an inductor in the x-over circuit to achieve this.

Even if you bi-amp this inductor is still in play. I'm running the tops full range and am running subs using a DRPA crossed @ 90hz. Peavey recommends running the box full range and using aux fed subs.

I'd rather defeat the inductor and run the 15's together like every other manufacturers double 15 + horn box.

Any reason I should not do this other than resale reasons?

I understand peavey's reason for doing this if the box is used alone, but I feel they should have made it at least defeatable.

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

Silas Pradetto wrote on Wed, 09 February 2011 13:25

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

To use them with subs and get full use of the dual 15's.

If I only used them as stand-alone speakers (w\ no subs), I wouldn't consider it.

They also do this on the dual-15 QW boxes IIRC.

I don't have the extra aux send to run aux subs at this time.

I just don't understand why they are the ONLY company to do this with their 2-15+horn box. Are they right and everyone else wrong?

John Watson wrote on Wed, 09 February 2011 14:50

Silas Pradetto wrote on Wed, 09 February 2011 13:25

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

To use them with subs and get full use of the dual 15's.

If I only used them as stand-alone speakers (w\ no subs), I wouldn't consider it.

They also do this on the dual-15 QW boxes IIRC.

I don't have the extra aux send to run aux subs at this time.

I just don't understand why they are the ONLY company to do this with their 2-15+horn box. Are they right and everyone else wrong?

Yes.

It reduces the nasty beaming at the upper end of the 15's range.
You get both 15's down low - where it's needed.
Running with subs, I'd actually recommend dumping the bottom 15 altogether.

Chris Hindle wrote on Wed, 09 February 2011 13:55

John Watson wrote on Wed, 09 February 2011 14:50

Silas Pradetto wrote on Wed, 09 February 2011 13:25

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

To use them with subs and get full use of the dual 15's.

If I only used them as stand-alone speakers (w\ no subs), I wouldn't consider it.

They also do this on the dual-15 QW boxes IIRC.

I don't have the extra aux send to run aux subs at this time.

I just don't understand why they are the ONLY company to do this with their 2-15+horn box. Are they right and everyone else wrong?

Yes.

It reduces the nasty beaming at the upper end of the 15's range.
You get both 15's down low - where it's needed.
Running with subs, I'd actually recommend dumping the bottom 15 altogether.

So, for example, JBL's SRX 725 box is designed wrong and should be set up like a SP4?

iirc one of the 15's has a coil(inductor)in series connected to the + side of the driver. "if" this is the situation then this coil is a 6db passive crossover that rolls the upper frequencies off. lets say it starts rolling them off at 90hz and you disconnect the coil you will then hear all the frequencies that 15 can produce. if you have a wiring diagram post it. if its an iron core coil it will have less dc resistance then an air core coil but an iron core coil can become saturated and cause some distortion. i looked at the sp4 online and wonder why they didnt just use a 15,12,horn combo. if you really want low end the 18 is the way to go. this is just my opinion and not the opinion of any musicaians,technicians,engineers(amtrack or not) that i know or have known.

John Watson wrote on Wed, 09 February 2011 14:11

Chris Hindle wrote on Wed, 09 February 2011 13:55

John Watson wrote on Wed, 09 February 2011 14:50

Silas Pradetto wrote on Wed, 09 February 2011 13:25

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

To use them with subs and get full use of the dual 15's.

If I only used them as stand-alone speakers (w\ no subs), I wouldn't consider it.

They also do this on the dual-15 QW boxes IIRC.

I don't have the extra aux send to run aux subs at this time.

I just don't understand why they are the ONLY company to do this with their 2-15+horn box. Are they right and everyone else wrong?

Yes.

It reduces the nasty beaming at the upper end of the 15's range.
You get both 15's down low - where it's needed.
Running with subs, I'd actually recommend dumping the bottom 15 altogether.

So, for example, JBL's SRX 725 box is designed wrong and should be set up like a SP4?

You're sort of projecting your conceptions onto the entire field of loudspeaker design here. I long ago decided to defer to major manufacturers regarding speaker design, choosing whichever of their products I found usable without starting to judge them and condemn their design and development process.....

And there are other cabinets with this design. The first one I can think of is the EV T-252 which shelves off the bottom 15 @ 400 while letting the top one go all the way up to the HF crossover point.

Use them as designed. That's my recommendation. If they work as well as the EV's they'll be full, smooth and not lacking in low mids. Set your subs crossover where you normally would.

John Watson wrote on Wed, 09 February 2011 15:11

So, for example, JBL's SRX 725 box is designed wrong and should be set up like a SP4?

Not wrong, just different. Peavey is not the only company to do this, Meyer does it in some of their line array speakers. As stated earlier it reduces the comb filtering due to the interaction between the low freq drivers.

Mac

Dick Rees wrote on Wed, 09 February 2011 15:04

John Watson wrote on Wed, 09 February 2011 14:11

Chris Hindle wrote on Wed, 09 February 2011 13:55

John Watson wrote on Wed, 09 February 2011 14:50

Silas Pradetto wrote on Wed, 09 February 2011 13:25

If you really do understand Peavey's reasoning for doing this, then why would you ever want to bypass it???

To use them with subs and get full use of the dual 15's.

If I only used them as stand-alone speakers (w\ no subs), I wouldn't consider it.

They also do this on the dual-15 QW boxes IIRC.

I don't have the extra aux send to run aux subs at this time.

I just don't understand why they are the ONLY company to do this with their 2-15+horn box. Are they right and everyone else wrong?

Yes.

It reduces the nasty beaming at the upper end of the 15's range.
You get both 15's down low - where it's needed.
Running with subs, I'd actually recommend dumping the bottom 15 altogether.

So, for example, JBL's SRX 725 box is designed wrong and should be set up like a SP4?

You're sort of projecting your conceptions onto the entire field of loudspeaker design here. I long ago decided to defer to major manufacturers regarding speaker design, choosing whichever of their products I found usable without starting to judge them and condemn their design and development process.....

And there are other cabinets with this design. The first one I can think of is the EV T-252 which shelves off the bottom 15 @ 400 while letting the top one go all the way up to the HF crossover point.

Use them as designed. That's my recommendation. If they work as well as the EV's they'll be full, smooth and not lacking in low mids. Set your subs crossover where you normally would.

Well, Peavey does not recommend using subs with them at all, unless you give the tops full range and use an aux & x-over to do subs.

Thanks for the info on the EV's, I wasn't aware of anyone else doing this. They don't do it on any of their more "pro like MI" boxes like the QRX 212 or tour x 215 do they?

And would it really sound that much worse to run both 15's
with the full 50-1800 (actually 90- 1800 since I'm using subs)?

I'd prefer to get as much mids as possible. If I could afford it, I'd get a pair of srx 722's or qrx 212's, but for now that is out of the question.

John Watson wrote on Wed, 09 February 2011 16:16

And would it really sound that much worse to run both 15's
with the full 50-1800?

I'd prefer to get as much mids as possible. If I could afford it, I'd get a pair of srx 722's or qrx 212's, but for now that is out of the question.

Yes. You will get less of some mid frequencies by running both 15s up to 1800. There will be cancellation due to the interaction between the two drivers that will change with frequency, and position relative to the speaker.

For the best response let the bottom 15 roll off above 800.

Mac

Mac Kerr wrote on Wed, 09 February 2011 15:30

John Watson wrote on Wed, 09 February 2011 16:16

And would it really sound that much worse to run both 15's
with the full 50-1800?

I'd prefer to get as much mids as possible. If I could afford it, I'd get a pair of srx 722's or qrx 212's, but for now that is out of the question.

Yes. You will get less of some mid frequencies by running both 15s up to 1800. There will be cancellation due to the interaction between the two drivers that will change with frequency, and position relative to the speaker.

For the best response let the bottom 15 roll off above 800.

Mac

Then how does JBL and others get away with it (SRX 725 for example)? Is it because of the lower x-over freq to the horn or is it the cab design?

John Watson wrote on Wed, 09 February 2011 16:35

Then how does JBL and others get away with it (SRX 725 for example)? Is it because of the lower x-over freq to the horn or is it the cab design?

Some of it is due to the 800Hz vs 1800Hz crossover, some of it is due to different design compromises. All designs involve compromise, it is up to the design team to chose where they will compromise.

Mac

Thanks for all the answers & info.

I guess I'll leave them as they are and work on getting new boxes ASAP. Time to start scouring for used boxes!

I see absolutely nothing in Peavey's specs that suggest you shouldn't use subs with these, and with any halfway decent crossover you should be able to push up the crossover frequency of the subs up to about 80, and use your choice of subs to fill in below that.

I would suspect if you have tried that and didn't like the results it was because of your crossover settings, not the design of the box.

Mac Kerr wrote on Wed, 09 February 2011 16:01

John Watson wrote on Wed, 09 February 2011 16:35

Then how does JBL and others get away with it (SRX 725 for example)? Is it because of the lower x-over freq to the horn or is it the cab design?

Some of it is due to the 800Hz vs 1800Hz crossover, some of it is due to different design compromises. All designs involve compromise, it is up to the design team to chose where they will compromise.

Mac

I guess I should have compared it to a JBL MRX525 since they're identical in x-over frequency and both are lower end boxes.

John,

I had four JBL SF125's ???? I think that is what they were.

I actually tore out the cross- over and jumped the 15's together in each cabinet so it was 4 ohm. I also bought some MR series horns too. This is when I bought a DR260 and also had four 2-18 subs.

There was a number of reasons I should not have done this and they are all stated above. It took a hell of a lot of tweaking to get em to sound "OK" -

I finally got a deal on EV QRX 153/75's and the four of them - and they SMOKE what I had before -

Back then I did what I had to do to get by, but it was a lot of work and head aches to get it to sound.......well, barely "OK"

As stated on this site before, these companies engineer these boxes for specific purpose. The 2-15 horn boxes with quasi-crossovers are really meant for DJ and smaller bands that want to plug and play.

I admit I tried to polish a turd.........haha - I know that now every time I fire up my EV rig now.

Good luck with everything

Patrick

If you run both 15's all the way down, then add subs, it wont work. Unless the subs are designed to mate with the tops, which would be luck if it happened. I tried that for a few years, and had a huge bill at the reconer repairing my 18's in my subs(overdriving them trying to overcome the cancellation). If the tops and bottoms aren't tuned the same, the bass coming from each does nasty things, such as cancellation at certain frequencies. If you are gonna run subs, take the sub frequencies out of the tops, send only the sub frequencies to the subs. Used properly with subs, you don't want the bottom 15 in the SP4's doing anything. SP4's are a poor choice to run with subs for that reason. Basically what you would be doing is stacking dissimilar subs side by side, which rarely works.

David A. Parker wrote on Fri, 11 February 2011 09:01

If you run both 15's all the way down, then add subs, it wont work. Unless the subs are designed to mate with the tops, which would be luck if it happened. I tried that for a few years, and had a huge bill at the reconer repairing my 18's in my subs(overdriving them trying to overcome the cancellation). If the tops and bottoms aren't tuned the same, the bass coming from each does nasty things, such as cancellation at certain frequencies. If you are gonna run subs, take the sub frequencies out of the tops, send only the sub frequencies to the subs. Used properly with subs, you don't want the bottom 15 in the SP4's doing anything. SP4's are a poor choice to run with subs for that reason. Basically what you would be doing is stacking dissimilar subs side by side, which rarely works.

Really? The subs interfere with the bottom 15 all the way up to 900Hz? I don't think so.

Run them the way they were designed, use a HPF on the mains, just like you would do with any full range speaker used with subs, and use an appropriate LPF on the subs. Let the bottom 15" go away at 900Hz so it doesn't cause comb filtering above that frequency.

Mac

Mac Kerr wrote on Fri, 11 February 2011 08:27

David A. Parker wrote on Fri, 11 February 2011 09:01

If you run both 15's all the way down, then add subs, it wont work. Unless the subs are designed to mate with the tops, which would be luck if it happened. I tried that for a few years, and had a huge bill at the reconer repairing my 18's in my subs(overdriving them trying to overcome the cancellation). If the tops and bottoms aren't tuned the same, the bass coming from each does nasty things, such as cancellation at certain frequencies. If you are gonna run subs, take the sub frequencies out of the tops, send only the sub frequencies to the subs. Used properly with subs, you don't want the bottom 15 in the SP4's doing anything. SP4's are a poor choice to run with subs for that reason. Basically what you would be doing is stacking dissimilar subs side by side, which rarely works.

Really? The subs interfere with the bottom 15 all the way up to 900Hz? I don't think so.

Run them the way they were designed, use a HPF on the mains, just like you would do with any full range speaker used with subs, and use an appropriate LPF on the subs. Let the bottom 15" go away at 900Hz so it doesn't cause comb filtering above that frequency.

Mac

You misunderstood what I was trying to say. Obviously I was unclear. I was only referring to sub frequencies. I did exactly what the op was suggesting with disastrous results. After I did what you say, everything worked wonderfully.

David A. Parker wrote on Fri, 11 February 2011 09:01

If you run both 15's all the way down, then add subs, it wont work. Unless the subs are designed to mate with the tops, which would be luck if it happened. I tried that for a few years, and had a huge bill at the reconer repairing my 18's in my subs(overdriving them trying to overcome the cancellation). If the tops and bottoms aren't tuned the same, the bass coming from each does nasty things, such as cancellation at certain frequencies. If you are gonna run subs, take the sub frequencies out of the tops, send only the sub frequencies to the subs. Used properly with subs, you don't want the bottom 15 in the SP4's doing anything. SP4's are a poor choice to run with subs for that reason. Basically what you would be doing is stacking dissimilar subs side by side, which rarely works.

It is very possible to get the subs to play well with the tops-even overlaping freq.

If done properly, you will get good summation.

Yes if you just "throw they up" and pour on the juice you can likely tear them up because they are not working together well.

But with careful alignment you can get some good results.

Ivan Beaver wrote on Fri, 11 February 2011 18:40

David A. Parker wrote on Fri, 11 February 2011 09:01

It is very possible to get the subs to play well with the tops-even overlaping freq.

If done properly, you will get good summation.

Yes if you just "throw they up" and pour on the juice you can likely tear them up because they are not working together well.

But with careful alignment you can get some good results.

The careful alignment part would put that setup out of the reach of many. As others have said, the OP would probably be better off leaving the internal crossovers in his cabs alone. Big name cabs have that sort of thing programmed into the magic box that comes with them. A friend had a KV system. It had some serious "black box" alignment and such going on. It had front loaded and folded horn and bandpass subs working together, extremely well. I'm sure they didn't get that one right the first time!

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

Jay Barracato wrote on Sun, 13 February 2011 07:26

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

because a lot of 2-15 cabs have the bottom 15 lo-passed passively internally such that when you hi-pass the cab with your active crossover, it pretty much cuts the bottom 15 out, negating it's value.

David A. Parker wrote on Sun, 13 February 2011 08:53

Jay Barracato wrote on Sun, 13 February 2011 07:26

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

because a lot of 2-15 cabs have the bottom 15 lo-passed passively internally such that when you hi-pass the cab with your active crossover, it pretty much cuts the bottom 15 out, negating it's value.

Maybe you could provide a link to those "lots" of speakers that roll off the bottom 15 below the 100Hz or so where you would put your HPF on the full range speakers you are using with subs. Even if the bottom 15 starts to roll off at 200Hz you still get a full octave of low frequency reinforcement from it. In the OP's case where the bottom 15rolls off above 900Hz he would still get all the lows and low mids out of both 15s.

Mac

Mac Kerr wrote on Sun, 13 February 2011 10:39

David A. Parker wrote on Sun, 13 February 2011 08:53

Jay Barracato wrote on Sun, 13 February 2011 07:26

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

because a lot of 2-15 cabs have the bottom 15 lo-passed passively internally such that when you hi-pass the cab with your active crossover, it pretty much cuts the bottom 15 out, negating it's value.

Maybe you could provide a link to those "lots" of speakers that roll off the bottom 15 below the 100Hz or so where you would put your HPF on the full range speakers you are using with subs. Even if the bottom 15 starts to roll off at 200Hz you still get a full octave of low frequency reinforcement from it. In the OP's case where the bottom 15rolls off above 900Hz he would still get all the lows and low mids out of both 15s.

Mac

I never said they rolled them off below 100hz, but some roll them off at 400hz, and when you hi pass at 100hz, I stand by what I said, the bottom 15 isn't doing much. Obviously, the 2-15 cabs we are referring to were not designed to be used with subs, although they work well with subs anyway. One benefit is that if you stack a 2-15 cab on a sub, it gets the horn up closer to where it needs to be. My main rig for many years was 2-15 cabs on top of 2-18 cabs. A lot of work to stack, but it worked very well. Not saying that was the best design, but it did work well.

David A. Parker wrote on Sun, 13 February 2011 16:25

Mac Kerr wrote on Sun, 13 February 2011 10:39

David A. Parker wrote on Sun, 13 February 2011 08:53

Jay Barracato wrote on Sun, 13 February 2011 07:26

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

because a lot of 2-15 cabs have the bottom 15 lo-passed passively internally such that when you hi-pass the cab with your active crossover, it pretty much cuts the bottom 15 out, negating it's value.

Maybe you could provide a link to those "lots" of speakers that roll off the bottom 15 below the 100Hz or so where you would put your HPF on the full range speakers you are using with subs. Even if the bottom 15 starts to roll off at 200Hz you still get a full octave of low frequency reinforcement from it. In the OP's case where the bottom 15rolls off above 900Hz he would still get all the lows and low mids out of both 15s.

Mac

I never said they rolled them off below 100hz, but some roll them off at 400hz, and when you hi pass at 100hz, I stand by what I said, the bottom 15 isn't doing much. Obviously, the 2-15 cabs we are referring to were not designed to be used with subs, although they work well with subs anyway. One benefit is that if you stack a 2-15 cab on a sub, it gets the horn up closer to where it needs to be. My main rig for many years was 2-15 cabs on top of 2-18 cabs. A lot of work to stack, but it worked very well. Not saying that was the best design, but it did work well.

If they roll off at 400Hz the bottom 15 is covering 2 full octaves of the low end if they are high passed at 100Hz. That is probably more than most subs will be covering. A common sub with a low frequency limit of around 30, which is pretty good for most subs, would have to be low passed at 120 Hz to cover 2 full octaves. The extra 15 will be providing additional output in the low mid range that so many people seem to think they don't have enough of. If you move the crossover frequency to 80Hz the bottom 15 will cover more than 2 octaves, and the sub would have to have response to 20Hz (not that common) to cover 2 octaves.

I fail to see how you come to the conclusion that the speakers being discussed were not intended to be used with subs. Subs are not the low frequency section of a full range speaker, they are the extended response below (sub) the range of a full range speaker. I can not think of a single full range speaker that has been designed to not be used with a sub to extend the low frequency response. If you know of one, and have some data from the manufacturer to support your view, please share it.

Mac

Mac Kerr wrote on Sun, 13 February 2011 16:00

David A. Parker wrote on Sun, 13 February 2011 16:25

Mac Kerr wrote on Sun, 13 February 2011 10:39

David A. Parker wrote on Sun, 13 February 2011 08:53

Jay Barracato wrote on Sun, 13 February 2011 07:26

I am not sure why anyone would think putting a sub with a box with 2 15's is any different than putting a sub with a box with 115.

because a lot of 2-15 cabs have the bottom 15 lo-passed passively internally such that when you hi-pass the cab with your active crossover, it pretty much cuts the bottom 15 out, negating it's value.

Maybe you could provide a link to those "lots" of speakers that roll off the bottom 15 below the 100Hz or so where you would put your HPF on the full range speakers you are using with subs. Even if the bottom 15 starts to roll off at 200Hz you still get a full octave of low frequency reinforcement from it. In the OP's case where the bottom 15rolls off above 900Hz he would still get all the lows and low mids out of both 15s.

Mac

I never said they rolled them off below 100hz, but some roll them off at 400hz, and when you hi pass at 100hz, I stand by what I said, the bottom 15 isn't doing much. Obviously, the 2-15 cabs we are referring to were not designed to be used with subs, although they work well with subs anyway. One benefit is that if you stack a 2-15 cab on a sub, it gets the horn up closer to where it needs to be. My main rig for many years was 2-15 cabs on top of 2-18 cabs. A lot of work to stack, but it worked very well. Not saying that was the best design, but it did work well.

If they roll off at 400Hz the bottom 15 is covering 2 full octaves of the low end if they are high passed at 100Hz. That is probably more than most subs will be covering. A common sub with a low frequency limit of around 30, which is pretty good for most subs, would have to be low passed at 120 Hz to cover 2 full octaves. The extra 15 will be providing additional output in the low mid range that so many people seem to think they don't have enough of. If you move the crossover frequency to 80Hz the bottom 15 will cover more than 2 octaves, and the sub would have to have response to 20Hz (not that common) to cover 2 octaves.

I fail to see how you come to the conclusion that the speakers being discussed were not intended to be used with subs. Subs are not the low frequency section of a full range speaker, they are the extended response below (sub) the range of a full range speaker. I can not think of a single full range speaker that has been designed to not be used with a sub to extend the low frequency response. If you know of one, and have some data from the manufacturer to support your view, please share it.

Mac

Mac,

I am with you in this game. For the record, the Meyer MTS4 has the sub built into the box which lists a frequency range of 32 hz-18 khz. But it could also be combined with other sub boxes such as the PSW-4. Actually I think it is a shame that system has been discontinued.

But that in no way negates the argument. Take the double 15 and cross it over somewhere between 80 and 100, let the subs carry everything below that. Both 15's will still have plenty to do.

Thanks for all the info. I'm going to cross the subs @ 90hz to start and then try 80hz and see which sounds best.

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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Lounge FUD Forum Archive => Topic started by: John Watson on February 09, 2011, 01:55:35 PM