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[John Watson]

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.

[Silas Pradetto]

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

[John Watson]

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?

[Chris Hindle]

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.

[John Watson]

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?

[jeff harrell]

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.

[Dick Rees]

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.

[Mac Kerr]

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

[John Watson]

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.

[Mac Kerr]

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