Using 15'' & 18'' subs together

[McR]

Hi,Has anybody used a combo of 15's & 18's subs? I have a pair of EAW sb150's & sb180's. I have read that you are not suppose to use different size subs together? I was thinking of Xover the 15's at 90hz to 150hz & the 18's at 90hz to 30 hz. Anyway i tried them with all Xover at 80hz and they sound great 15's add punch & 18 add great bottom. Should i bother with the separate Xovers? I have 2 Crown XTi4000 for sub duty & they have all the DSP i need,but things sound fine running with the same settings on all subs.Is there something I'm missing?
Thanks

 

[fuzz092888]

I would think the problem would have less to do with where you are crossing them, than with what kind of high pass filters you're putting on them. The 15" sub will need a higher high pass filter than the 18" since it won't go as low, but you might also have to worry about output differences as well. The louder you go, the quicker the 15" will run out of gas. These types of differences are why most recommend not using different subs together if possible.

 

[McR]

Thanks fuzz, The specs on both cabs are the same,they will both do 20hz & both have 1000 rms RCF woofers.I put a hi pass of 30 hz on both & so far things sound pretty good. I have not really pushed them to the limit,but when the weather gets nice i'll set up out doors & see what happens. Cheers!

 

[fuzz092888]

What slope did you use for the high pass?

 

[McR]

I used Butterworth 24 db/oct. I have a choice of 6,12,18,24,48. 24 is what EAW uses. The processor settings for both cabs are the same,even the PEQ at 30 Hz with 5 db gain. These are the settings form the EAW site & are the same for both So far sounds great ,but as you said ,i haven't pushed them to the limit ,i can only get to half the output before the house starts to shake,windows rattling ,let alone the wife,lol.She must luv me.

 

[McR]

Ahhh,i see what your getting at,perhaps raising the high pass on the 15's to 40 or 50 once things get cooking would clean things up at high levels.

 

[fuzz092888]

That's the thing, they shouldn't be the same. They are different subs and therefore need different settings. Per the PDF sheets on each respective sub: SB180 highpass at 25hz 12db/octave butter worth. SB150: highpass at 25hz with the 24db/oct.

As for the PEQ, I wouldn't set that until I had measurements of their in room response to see if that is where it is really needed, although I don't know if you've done that.

 

[McR]

Thanks i'll try that out & no i haven't set the PEQ. I will be using the sys for a classic rock trio,200 to 300 seat rooms. The tops are EAW FR 159's a two way 15+horn 500 rms.

 

[fuzz092888]

Sounds good. You'll definitely want to abide by the manufacturer specs for the high pass if your intended use is going to be for the kind of SPL's needed for classic rock in a large room. Just play around with it, but I would assume those slopes are your best bet. Don't forget that you'll need to adjust the gains with the 15 being a little higher than the 18 to match output. Cheers.

 

[Grador]

Don't forget that you'll need to adjust the gains with the 15 being a little higher than the 18 to match output. Cheers.

Wouldn't it be better, though a little more difficult, to set the gains of the subs so that they both reach peak output at the same time? I'm just not seeing why they need to have the same output level.

 

[McR]

I'll try them out next weekend ,we're playing a 200 seater with good acoustics so it should give me a good idea of where i need to be! Thanks for the sound advice.Cheers!

 

[fuzz092888]

Wouldn't it be better, though a little more difficult, to set the gains of the subs so that they both reach peak output at the same time? I'm just not seeing why they need to have the same output level.

In my mind, you're level matching the gains so that the bass response stays even across the widest range of seats. While you lose the ability to have them peak at the same time, it's the tradeoff of having two different subs.

You could set it so that they peak together, but wouldn't you be ramping up the distortion levels of the smaller sub as it strains to keep up with the larger one?

 

[Grador]

You could set it so that they peak together, but wouldn't you be ramping up the distortion levels of the smaller sub as it strains to keep up with the larger one?

I think it'd be the opposite. If you have them set to put the same level out, the small one will run out of gas distorting first. What I'm saying is to set the gain so that they run out of gas together, having them both run into distortion at the same input level.

You would be sacrificing more even room response [which, if the subs were stacked wouldn't be a benefit of having two anyway] for higher peak output and more linear output increase.

Edit: Just realized what you meant. I chose words poorly, by "peak" I didn't mean peak. I meant more highest continuous power.

 

[fuzz092888]

Wouldn't setting the 15 to match the 18 provide more continuous power than matching the 18 to 15 (<is that what you were suggesting?)?

 

[Grador]

Wouldn't setting the 15 to match the 18 provide more continuous power than matching the 18 to 15

<is that="" what="" you="" were="" suggesting?)?[="" quote]

No, because the 18 would then be limited to where the 15 ran out of gas, lest you want the 15 to run into terrible distortion and/or die.
If you set them to reach their peak continuous together then you get the get the most out of both.


For the sake of discussion lets use totally made up "power units". If the 18 is capable of continuous output of 18 PU and the 15 is capable of 15...
If you set them to have equal output relative to input you get 1+1, 2+2.....15+15. Past 15 you'd go up to 18+terrible distortion.

If you set them to go all out at the same input level you'd go 1+0...4+1...18+15

Edit: Keep in mind that I'm using these completely useless numbers just to demonstrate what I'm thinking.</is>

 

[fuzz092888]

I get what you're saying now. Agreed.

 

[jlanzy]

I'm not an audio tweaker, so my experience may be of limited use, but I have had a VeloDD15, and added a 18 " JTR sealed Capitvator, 2400w internal amp. I added the JTR into my 2 seat 19x14x8 theater room when I got the Denon 4520 with its dual sub EQ ability. I use the room only for tv/movies and on the big action movies the added sub really adds that visceral impact to the low frequency effects.

 

[McR]

Thanks guys, lots of good info.Im thinking 15's & tops per side & 18's coupled front of stage.I run the subs on aux ,so all that gets in will be bass guitar ,bass drum & low toms. Not sure on placement yet as it will depend on the room. Thanks again for the input,greatly appreciated.

 

[lsiberian]

The best way to figure this out is to experiment. Theory is just theory. Finding out what practically works in your setup is a product of experience.

 

[McR]

Very true,every room is different. Live sound can make ya crazy. Placement ,delay,monitors, every time people enter, or leave things change in the room. Ears are the final mix.