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Author Topic: Modify Peavey SP4's?  (Read 14706 times)

John Watson

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Re: Modify Peavey SP4's?
« Reply #10 on: February 09, 2011, 04:35:56 pm »

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?
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Mac Kerr

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Re: Modify Peavey SP4's?
« Reply #11 on: February 09, 2011, 05:01:32 pm »

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
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John Watson

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Re: Modify Peavey SP4's?
« Reply #12 on: February 09, 2011, 05:38:16 pm »

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!
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Jay Barracato

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Re: Modify Peavey SP4's?
« Reply #13 on: February 09, 2011, 06:09:02 pm »

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.
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Jay Barracato
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John Watson

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Re: Modify Peavey SP4's?
« Reply #14 on: February 10, 2011, 12:35:39 am »

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.
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Patrick Campbell

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Re: Modify Peavey SP4's?
« Reply #15 on: February 10, 2011, 08:39:51 am »

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


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David A. Parker

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Re: Modify Peavey SP4's?
« Reply #16 on: February 11, 2011, 09:01:01 am »

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.
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David Parker
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Mac Kerr

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Re: Modify Peavey SP4's?
« Reply #17 on: February 11, 2011, 09:27:45 am »

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
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David A. Parker

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Re: Modify Peavey SP4's?
« Reply #18 on: February 11, 2011, 10:06:48 am »

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.
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David Parker
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Ivan Beaver

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Re: Modify Peavey SP4's?
« Reply #19 on: February 11, 2011, 07:40:55 pm »

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.
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