Calibrating four subs, co-located - AVS Forum
Audio Theory, Setup, and Chat > Calibrating four subs, co-located
michaelscott73's Avatar michaelscott73 06:33 PM 11-14-2012
I'm introducing a pair of PC Ultra's into my system, currently I have a pair of VTF-15's. I'm thinking the best way is to co-locate each pair. I'm not sure though how I would calibrate using xt32. Would I set the sub level for sub 1 and sub 2 as normal and just make sure the sub volume control is in the same position on each co-located sub?

arnyk's Avatar arnyk 04:51 AM 11-15-2012
Quote:
Originally Posted by michaelscott73 View Post

I'm introducing a pair of PC Ultra's into my system, currently I have a pair of VTF-15's. I'm thinking the best way is to co-locate each pair. I'm not sure though how I would calibrate using xt32. Would I set the sub level for sub 1 and sub 2 as normal and just make sure the sub volume control is in the same position on each co-located sub?

According to the best available science, co-locating multiple subs is not the best way to go.

http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White%20Papers/multsubs.pdf


umr's Avatar umr 11:37 AM 11-15-2012
The best thing to do would be to measure and set the sound output from each subwoofer independently.

Co locating them is not the best solution, but sometimes you are limited in location. A combination of equalization, level, location and phase can be used to achieve a smoother room response.
michaelscott73's Avatar michaelscott73 12:01 PM 11-15-2012
Quote:
Originally Posted by umr View Post

The best thing to do would be to measure and set the sound output from each subwoofer independently.
Co locating them is not the best solution, but sometimes you are limited in location. A combination of equalization, level, location and phase can be used to achieve a smoother room response.
How would I do this with Audyssey? It's unclear in the white paper if there was any room correction used. Obviously if no room correction is used the ideal set up would utlize four different locations for the smoothest response. Given I am using XT32 my thought process was anything more than two locations would basically give me substantial diminishing returns and I would be better off getting the increased output bumb from co-locting.
umr's Avatar umr 12:30 PM 11-15-2012
This cannot be done well with Audyssey. My experience with Audyssey is poor in general and very poor with multiple subwoofers. These must be done manually to get the best performance. I offer an audio service for this purpose or you can purchase equipment and attempt it yourself.
arnyk's Avatar arnyk 12:42 PM 11-15-2012
Quote:
Originally Posted by michaelscott73 View Post

Quote:
Originally Posted by umr View Post

The best thing to do would be to measure and set the sound output from each subwoofer independently.
Co locating them is not the best solution, but sometimes you are limited in location. A combination of equalization, level, location and phase can be used to achieve a smoother room response.
How would I do this with Audyssey? It's unclear in the white paper if there was any room correction used.

I share your confusion about the idea that the subwoofers be set up independently. The point of the whole system of 4 subs is to obtain the most uniform bass over the entire listening room. Extend that idea logically and it suggests that the SPL at each of the subwoofers would be essentially the same.

My understanding is that you have 2 (1 pair) Hsu VTF-15s and 2 (1 pair) SVS PC13 Ultras. Left to their own means, they are very likely to have different sensitivities.

For a given input voltage at some common point, the SPL from each subwoofer at any given frequency is probably different unless you match them some how. That has to be dealt with first. If you are going to run them all together. They need to have similar SPL output at a useful range of frequencies with the same input. They all have input level controls so the real question is how to set up those controls before we start trying to optimize the entire system.

Perhaps this is what was meant by "The best thing to do would be to measure and set the sound output from each subwoofer independently." How to do this?

This is a situation where having an independent acoustic measuring facilty (e.g. mic, software, PC) can be a great benefit. If you had a measruement facility you would then set up the subwoofers and measure the response of each subwoofer connected up by itself, and adjust its gain control until its measured response in your seating area is as similar as posssible to all the rest. Then enable all 4 of the subwoofers at the same time and run Audyssey.
Quote:
Obviously if no room correction is used the ideal set up would utlize four different locations for the smoothest response. Given I am using XT32 my thought process was anything more than two locations would basically give me substantial diminishing returns and I would be better off getting the increased output bumb from co-locting.

I don't see that. The first concern is not that the response be as smooth as possible but that it be as uniform as possible. Once bass uniformity is optimized over your desired seating area, obtaining smooth response in one location will make it more likely that bass response is smooth at the other locations.
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