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post #1 of 8 Old 05-23-2020, 08:53 AM - Thread Starter
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Mixing different size sub

I purchased 2 15 Dayton ultimax 15s and wanted to purchase 2 more for a configuration of subs at all four corners of the room, my question is can I use 2 Ultimax 18 subs at the front corners and 2 Ultimax 15s at the rear corner or would it be better to stick to the same diameter at all 4 corners. My plan was to place them all in sealed 3-4 cu ft boxes.

Thanks for the help.
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post #2 of 8 Old 05-23-2020, 10:11 AM
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Yes, you definitely can use UM18-22 and UM15-22 in the same setup. However, the UM15-22 will run out of steam before the UM18-22
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post #3 of 8 Old 05-23-2020, 11:38 AM - Thread Starter
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Thanks, so even though the two drivers have different performance in their sealed boxes, would there be any issues in terms of phase and frequency performance which would cause cancellations or odd response. I have audyssey xt32 in my av receiver and plan to calibrate the fronts as a group relative to the rears as a group.
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post #4 of 8 Old 05-23-2020, 12:05 PM
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Quote:
Originally Posted by aaks38 View Post
I have audyssey xt32 in my av receiver and plan to calibrate the fronts as a group relative to the rears as a group.
XT32 doesn't do that. It measures distance of LFE outputs 1 and 2 individually, but EQs them as a single entity.

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post #5 of 8 Old 05-23-2020, 12:35 PM - Thread Starter
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Sorry I meant that my front two subs would be connected to sub 1 output and the rear two connected to sub 2. I know when calibrated, the fronts would be measured as a pair separately than the rears by having different distance calculations and hopefully the distance calculation compensates for the phase variation.
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post #6 of 8 Old 05-23-2020, 02:58 PM
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The UM-15's will give up before the UM-18's will, and so it will start to distort earlier too, and ultimately place a limit on how loud the system will go before they become damaged or start sounding ugly.

...Unless you de-tune them to compensate for that difference, which is what I do with my fronts; this of course causes them to play quieter / less excursion so you don't over stress them.

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Originally Posted by aaks38 View Post
compensates for the phase variation.
It won't, as the two drivers will have a slightly different response for any given input signal.
It is unavoidable in a mixed system.

I have 5 different subwoofer drivers in my system: the SAB-24, MalX-21's, LMS-18's, UM-15's and PA-460's.
It's not "ideal" but it still sounds really good, and is still loud as hell.
Too bad TC and Exodus went bankrupt before I could finalize. Is what it is...

Luckily though humans don't hear phase, they hear SPL.

I mean, everything causes a phase shift, moving your head 1 inch is all it takes to shift the phase of all drivers based on the changed distance "ray" paths, and changing seats or walking around the room? Forget about it!!!

It happens in every system, even if you had all the same subwoofers. Only one seat can be golden, the rest will just be average.
I mean I suppose you "could" put a nearfield subwoofer behind every seat in the room, that would help (up to a point). It's been done before! Or you could implement a double bass array with quarter-wave placement.

but in summary: Adding more subwoofers, is always a good thing...
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post #7 of 8 Old 05-24-2020, 10:11 AM - Thread Starter
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Thanks for the feedback, so im curious for those of you whom are doing this, do you have different crossover points based on the diameter and response of the sub or do you guys keep the low pass point the same across all drivers?
Thanks.
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post #8 of 8 Old 05-24-2020, 10:48 AM
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Are either set of subs significantly closer to the listening position?

If so, place the 15's at the closer position to lessen their SPL requirement.

Otherwise, why not just get two more 15's?

Noah
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