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JBLRULES
07-12-2018, 11:46 AM
I'm looking to attain true stereo B460's with my 250tibq's and 2 BX63A's. Is this possible with what I have here. I'm not interested in running my 2 B460's with summed signals to each. Advice appreciated guys.

rdgrimes
07-12-2018, 01:23 PM
My $0.02
Most rooms benefit greatly from having 2 subs running. (mono x2) Running stereo subs eliminates that room gain, or perhaps effectively divides it in half. Although its also true that much of the VLF content in a stereo signal is spread across both channels. So in practice it might not make any difference for most content which way you run them. Point being that you shouldn't make assumptions and try an assortment of content both ways. Its also true that with VLF (<80Hz) content you can't discern which side its coming from.

But to answer your question: I don't see any reason your can't run the BX63 with just a single input, or with a y-cable connecting a single line to both inputs.

rusty jefferson
07-13-2018, 05:31 AM
Agreed that if you run the B-460s low (mine were 63hz) it's not necessary to have stereo. We did some a/b/x testing here with audio knowledgeable folks and no one could differentiate mono from stereo. The higher the frequency at crossover the more likely it could be noticable.

You would still need a left and right input to allow for information on both channels to be summed to the mono output.

Also, battery test both subs to verify they are both moving the same direction (doesn't matter which way) on a positive charge before hooking them up and determining proper polarity in the system. I have seen instances where the drivers were moving opposite directions. Sometimes things get hooked up backwards after a refoam/recone.

sguttag
07-13-2018, 07:21 AM
If you do use two BX63/63A, I would definitely use a Y-cable to tie both inputs together and not leave a high-impedance (100K) input open.

I'm also in the camp that they need not be stereo subs but definitely give it a shot and do what sounds best to you.

JBLRULES
07-13-2018, 07:50 AM
Thanks guys for the expertise and opinions on this. I really appreciate it and am going to move forward with one BX63A and a Y cable on the output to feed both B460's.

grumpy
07-13-2018, 08:37 AM
Lol, I would totally go the other direction and eq each independently (could still do with mono input to dual equalizers).
An added complexity that not everyone would want to bother with, and may not be able to appreciably tell the difference
with most material. Apparently, I have control issues ;)

RMC
07-13-2018, 09:14 AM
Out of town now checking forum on wife, s tablet.
i, d go with stereo subwoofers.
R.A. Greiner prof of Elec. Eng., director of acoustics Lab at University of wisconsin and renowned AES Fellow wrote on this issue in the 90s. The Lowdown on Subwoofers.. in Audio magazine. When l, m back home this weekend i, ll report with more details on this.
So i agree with Grumpy, s other direction and ...with most material and or people...
Richard

Robh3606
07-13-2018, 09:23 AM
Lol, I would totally go the other direction and eq each independently (could still do with mono input to dual equalizers).
An added complexity that not everyone would want to bother with, and may not be able to appreciably tell the difference
with most material. Apparently, I have control issues ;)

Well I have a single BX-63A driving 2 B380's with a Y into a stereo EQ to do separate EQ for each, It's well worth it as the EQ for each Sub is different due to location and room geometry. A single EQ for the pair simply will not work in my room anyway.

Rob:)

Ed Kreamer
07-13-2018, 12:42 PM
I have done it both ways, ( using Altec 411's ) and found better results doing mono. I'm sure that it will vary with the room ,placement, listener, type of music and crossover among the the other variables. For organ pedals there was no contest. Mono worked better. In my smallish room any way.

RMC
07-18-2018, 01:47 PM
Hi JBLRULES,

First, sorry for the delay in coming back to you on this issue.

As mentioned in post # 7 here is some info from R.A. Greiner about the use of single (mono) VS double (stereo) subwoofers. The point made is relevant since a few members have indicated in this thread using mono subwoofer(s) for LF reproduction, as if it was the best way to fly...

There are other aspects covered in the article such as some physics of LF reproduction and low frequency drivers capabilities per diameter VS frequency and acoustic watts produced. Since the LF capabilities of the B460/2245H are not at stake here, I'll concentrate on the single (mono) VS double (stereo) subwoofer aspect.

Talking about three-piece sound systems (one mono subwoofer and two stereo satellite speakers), he writes: "... i have some concerns and reservations about the technical justifications for the three-piece system." (p. 39) (...)

"A question of concern is whether one or two subwoofers should be added. If one subwoofer is added, the result is a three-piece system with monaural bass below about 80 to 100 hz. If two subwoofers are added, the result is two full-range loudspeakers [RMC: including the satellite speakers] with stereo bass. Does it matter if we have stereo or monaural bass? I would claim that it does, for at least two reasons. The first is that we have much better program material today from the Compact Disc than we did with the vinyl record. We have greatly extended bass frequency response and have two entirely independent channels. That is, there is more realistic bass- and it is often completely stereo." ( p. 40) (...)

"The second reason is not quite so obvious: There is considerable interaction between the room and the bass loudspeakers. We all know that placing the bass loudspeaker near a wall or in a corner of the room changes the amount and distribution of the bass frequencies in the room. At low frequencies, strong and widely spaced room modes are occuring. These modes are evidenced by the fact that as we move about the listening room, some locations have a lot of bass while others lack bass. The locations where more or less bass is heard move around within the room when the loudspeaker is moved from place to place. The problem with the three-piece system is that we have only one bass loudspeaker. Thus, the room is only excited from one point, and we have a set of modes that are quite audible.

When two bass loudspeakers are placed in the room and are excited by a stereo signal, each will have its own set of modes. It is not likely that the lack or excess of bass from one loudspeaker will fall at exactly the same point as for the other loudspeaker. Thus, a considerably better uniformity of bass response is obtained when the room is excited from two sources." (P. 40) [Harman fellows below make a similar finding]

If one listens to vinyl records only a single mono sub may make sense. However, if listening to CDs or other digital media is also part of the picture, then it probably makes more sense using stereo subs.

Finally, In the first few pages of their more recent study, Harman Engineers Todd Welti and Allan Devantier more or less seal the case of the single subwoofer. Just from a small excerpt of their paper's summary one can easily see their point: "... through the use of multiple subwoofers the seat-to-seat variation in the frequency response can be reduced significantly, allowing subsequent equalization to be more effective." Low-Frequency Optimization Using Multiple Subwoofers, JAES, Vol. 54, No. 5, 2006 May, P. 346-364.

Richard

R.A. Greiner, The Lowdown on Subwoofers, Audio Magazine, August, 1993, P. 38-40, plus table typo correction in Audio, october 1993, p. 8.

rusty jefferson
07-19-2018, 04:45 AM
I don't think anyone is arguing that 1 mono sub is better than 2 stereo subs. The question is 2 mono subs vs 2 stereo subs and whether he/she will hear a difference, ie locational information. My feeling is that as long as the subs are crossed low enough, it's not likely anyone can distinguish the directional differences, even with content that was recorded in stereo. Imaging specificity is maintained because the transient of the notes played are much higher frequencies and locate the instrument on the soundstage.

Ian Mackenzie
07-19-2018, 02:26 PM
Assuming for a moment that (low) bass signals are recorded in stereo (independently L+R) when they are summed into dual mono signal subs you have twice the cone area operating for any given L or R bass signal.

From the perspective of distribution of bass no arguments there but for that to work optimally both subs should be dual mono so the same bass fundamentals come from different locations. The crossover point must be low enough not to cause localisation. If you have small L+R mains it might be more beneficial to operate at a higher crossover point.

Earl Geddes recommendations 3 subs btw.

Subjectively l would think for HT dual mono is beneficial.

However, with an acoustic string bass and for example drums recorded in stereo or bass guitar one might speculate the separation of the bass sources is beneficial in terms of creating a sense of space. I recall this type of discussion came up in Stereophile many years ago.

The point being if the two different bass sources being recorded are separated by some distance then ideally they should be reproduced some distance apart. Can of worms maybe?

Perhaps some recording engineers might care to comment?

Like all this stuff some experimentation might be required to see what works best with your own setups and environment.

Robh3606
07-19-2018, 06:55 PM
Hello Ian

FYIW I have an EMOTIVA XMC-1 and it has stereo L+R LFE outs and I have no idea how it is mixed duriing an HT mixdown.

Rob:)