# Dedicate Spare Sub to Mains or CC?



## Swifty358 (May 4, 2011)

I now have two subs, a 12" Velo and an 18" Velo. The 18" Velo is much better for LFE so I know I'll us it as such. Since the 12" is so much different I don't want to use is as another LFE sub so I want to add it to another stage, either the main fronts or the center. 

Which stage generally has more bass or where will the extra bass be best utilized? Mains or center channel?

Thanks


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## Infrasonic (Sep 28, 2010)

I think the most overall content would be through the center channel but as to which has more bass I'm not sure; I think your best bet would be to try both and see which you enjoy more.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Generally it’s not a good idea to use mismatched subs. Overall response will always be “dumbed down” to that of the lesser sub. See this post for supporting frequency response graphs.

Using the 12-incher for the mains or center won’t change that, as the full-range (i.e. sub-included) signal will combine with the LFE channel in most cases. The only exception would be the rare situation where bass was sent only to the center or main channels and not the LFE.

Regards,
Wayne


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## Swifty358 (May 4, 2011)

I thought that is how movies are generally mixed, an LFE channel mixed separately? 

My thought was the bass signal in the LFE would be different than the bass signals of the center or mains anyway so the mixed freq. response of the two different subs would be nullified. So long as I had the subs set to opposing phases, my mains or center set to LARGE, and the receiver only sending the 18" sub the LFE channel not the LFE+MAIN, I figured I would be good to go.

I currently have the 12" attached to my mains w/ LFE to the 18" and I can tell a definite difference between only using the 18" w/o 12" hooked-up. The 12" will be utilized one way or the other until I replace it w/ another. I'm now an avid proponent of multiple subs for movies--music, probably not.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I thought that is how movies are generally mixed, an LFE channel mixed separately?


Sure, they’re mixed separately. But that doesn’t mean they send fully discrete bass to every channel at all times. After all, movie theaters utilize a subwoofer channel just like home theaters. Most viewers can't determine the origin of a bass signal from 50 ft. back, (i.e. which channel it's coming from) so there's no real incentive for film mixers to utilize discrete low bass in the main channels.

Not to say it never happens, but perhaps you can try it and see if you find instances of bass coming from say, the center channel that wasn't generated anywhere else.




> My thought was the bass signal in the LFE would be different than the bass signals of the center or mains anyway so the mixed freq. response of the two different subs would be nullified.


Different how? What would be different about say, a “boom” originating in the LFE channel from one from the center channel? When two subs “nullify,” that means their combined output is eliminated or drastically reduced over all or part of the bass frequency spectrum. It’s typically not a goal one aspires to when adding additional subwoofers. 




> So long as I had the subs set to opposing phases...


”Opposing phases” typically refers to residential electrical service – e.g. the two opposite-phase 120 volt lines that comprise 240-volt service. Can you explain how and/or what “opposing phases” has to do with assigning subwoofers to any of the various main channels of a home theater system, and how “opposing phases “ is “set?” :scratch:




> I currently have the 12" attached to my mains w/ LFE to the 18" and I can tell a definite difference between only using the 18" w/o 12" hooked-up.


Have you taken any measurements to verify your impressions? Without the benefit of measurements, it can be easy to mistake “louder” for “better.”

Regards,
Wayne


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## Swifty358 (May 4, 2011)

I may have misspoke about the phases. Maybe I meant polarity? One set to 0-Deg and the other at 180-Deg.

I haven't taken measurements other than sound level equalizations. using HT optimizer on one of my BD's I equaled out sound levels from my viewing position on all my speakers, then the 18" sub. After that I sent the mains a high frequency test signal (either 500 or 1000 hz), measured that. Then sent them a low frequency (which was filtered out from the mains and processed bvy the sub) which played through the sub and equaled it out. I don't think everythign is just louder, I painstakingly set it up. But, I haven't watched a movie and recorded peak measurements w/ and w/o the 12". may be worth trying. It all still sounds quite balanced to me.


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## Swifty358 (May 4, 2011)

I see what you're saying about a boom being a boom. Makes sense, never really looked at it that way.


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## Swifty358 (May 4, 2011)

Wouldn't you have the same issue though w/ full range tower speakers? Take a Paradigm S8 or Studio 100. Those have 3-4 7" subs per speaker so 6-8 between the two. They won't have the same freq. response as any sub, so then in theory would you never have a full range speaker set as LARGE whenever utilizing a subwoofer?


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## Wayne A. Pflughaupt (Apr 13, 2006)

I wouldn’t necessarily say “never,” but indeed large full-range speakers certainly have the potential to mess up low freq response, especially if the crossover for the sub is set high enough for it and the mains to overlap (duplicate) part of the bass range. These things really should be double-checked with measurements to make sure the speakers and sub(s) combined are all delivering smooth response and aren’t interfering with each other.

Regards,
Wayne


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## Swifty358 (May 4, 2011)

You're talking frequency response measurements? I've attempted that in the past w/ very little success. I'm not sure if I just wasn't using enough or proper equipment though. Whats the best method you can reccommend for doing so?


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## Wayne A. Pflughaupt (Apr 13, 2006)

REW is best, but if you don’t want to spend the money on the necessary gear, you can plot 1/6-octave sine waves from ~20-100 Hz on graph paper to get an idea of your bass response. Naturally, you’d have to take multiple readings – each sub separately, each with the main speakers, then all combined. Doing it with sine waves is time consuming (all you need is an SPL meter), but it’s cheap.

Regards,
Wayne


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## Swifty358 (May 4, 2011)

OK. I've tried full range measurements in the past w/ sweeps and microphones and such and was never successful. Did a few like you said w/ sine waves, an spl meter, and Excel and yea it was time consuming but helpful. Found waves in 1 hz increments from 20-100/120 I think so when I have some free time I'll have to try it again.

Found a pair of 15" SPL velo's for decent price too, so if things aren't meshing as well as I thought I can always go that direction too. Hopefully I can still get the sub-sonics from the two 15" I *think* I'm getting from the 18".


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## Wayne A. Pflughaupt (Apr 13, 2006)

There’s no need for single-frequency readings. 1/6-or perhaps 1/12-octave intervals is all you need. This graph shows the frequencies for 1/12-octave, if that helps. If you want to do 1/6, just go with every-other figure shown, starting with 20 Hz.







​

Regards,
Wayne


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## Swifty358 (May 4, 2011)

What's the best way to test everything together? 5 channel stereo so every speaker is playing the same signal?


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## Wayne A. Pflughaupt (Apr 13, 2006)

You’re mainly interested in calibrating the sub(s) to the L/R mains, not necessarily the rest of the speakers. So take a sub(s) reading, and then sub with L main, and sub with R main, then sub(s) with both L & R combined.

Regards,
Wayne


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## Swifty358 (May 4, 2011)

Alright thanks.


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