Will adding more subs really improve bass response in a properly calibrated setup? (1 Viewer)

[JohnSmith]

What you would do is calibrate sub A to 75dB, with sub B switched off. Then calibrate sub B to 75dB with sub A switched off.

Then with both subs switched on, calibrate both subs to your preferred calibration level, say 73-78dB.

If you pay attention to your overall output with dual subs to a single sub, each sub will be lower in volume than before- but combined it'll be the same volume as a single sub. It just means each sub will be under less strain than before (if you were reaching the limits of a single sub)

 

[steve nn]

I'm getting closer. Maybe I'll do a separate thread on it soon.

Hope so

I understand your thought process Mitch but John just answered it to the T.

Jeff if your still here? What do you think about going the dual rout now? Do you feel like your missing anything with your 20-39PC+ in your size HT?

 

[Nick Laho]

I have a question: By using a cable splitter to split a sub out signal into two signals, does that lower the volume of the signal to each sub? Would I have to compensate for a signal volume decrease? Or would it be the same as with one sub? Im curious because I don't calibrate my subwoofer with the Radio Shack meter, I just set it and go. (So I really wouldn't know how much to compensate for any signal decrease that might occur without guess work.)

 

[Kevin C Brown]

Richard- Good stuff!

Here's some more readin' for those interested:

http://www.harmaninternational.com/w...articleId=1003

Here's my seat o' the pants view of more than 1 sub:

1) Stack them in the same corner. The "best"/easiest compromise between output, flat freq response, and (lack of) interaction between them.

2) *If* you had infinite flexibility in terms of placement, you *can* get flatter response with 2 (or more) vs 1. But a lot of poeple already have "stuff" in the best locations.

If you read the article above, the best place for 2 subs is opposite walls, 1/2 down each wall. (Not opposite corners like a lot of people are told by dealers.) But me? I have a TV stand on 1 wall, and a desk/hutch thing in the back with my rears on it. I couldn't do it this way without a major re-arrangement of my setup. (One side wall is a sliding glass door with an acoustically helpful heavy curtain in front of it, and the other side wall opens into my kitchen.)

 

[Richard Greene]

The article you referenced is misleading because its goal is not the smoothest possible bass frequency response for a single listener, which most of us want.

The goal of the experiment was the most consistent (not smooth) bass frequency response from seat-to-seat within a fairly large area of a very large homer theater room.

A more consistent overall bass level (SPL) in a large home theater is important if there are perhaps a dozen people watching a movie.

But for a single listener, the smoothest bass frequency response at his (one) listening position is most important.

The article presents a prediction made using finite element analysis that has not been validated by any experiments in any real listening rooms.

I have read a USENET post by Tom Nousaine claiming that he tested the recommendations in the article and found one sub in a corner had a better frequency response.

My personal opinion based on over 20 years of in-room measurements and experiments is that in most listening rooms you need lots of bass traps and/or a parametric EQ for your subwoofer if you want to hear a smooth bass frequency response.

For audiophiles with two-channel stereos, the subwoofer should be close to one of the main speakers (or half way between them if there is significant output over 80Hz.)
if one wants good satellite speaker-subwoofer integration.

I prefer the sub driver and satellite speaker mid-bass drivers the same distance from my ears (and even better with the sub driver a foot or two closer to my ears, although that's not feasible in many rooms).

 

[Kevin C Brown]

Richard- Well, usually when I watch a movie, I'm watching with other people, so flat freq response at different points in the room *is* important.

But your point is well taken.


Good to know. Since you're scoping this thread, single vs multiple subs, and placement, etc, ... Right now, I use the typical recommendation, one sub in the corner, and I use a BFD parametric eq to smooth the worst of the peaks. OK. I have been toying with the idea of moving my sub to essentially be right next to my listening position, kind of as an end table. I have heard that this spot is pretty good too? You know, goes back to the one method of best-placement: place the sub *at* your listening position, then crawl around the room listening for the "best" quality bass (presumably flattest freq response). Then put your sub *there*. But at/near the listening position itself? Maybe not the highest output, but pretty good freq response?

 

[BruceD]

Kevin,

I think it depends on whether or not you want to use the sub for music as well as HT. For me it's about 90/10 music/HT.

I find it best to keep the sub within 3-6 feet of a main speaker for best integration when playing music.

If HT is the only objective, then a sub next to the listening position is probably OK.

 

[dave alan]

Richard said...
"I prefer the sub driver and satellite speaker mid-bass drivers the same distance from my ears (and even better with the sub driver a foot or two closer to my ears, although that's not feasible in many rooms)."
____________________________________

I agree with this as the logical placement first step.

All the myriad of FR graphs posted over the years don't show time arrival differences. The resulting lobing/cancellations are always mistaken as 'room modes'.

There's also the combination of disparate in room slopes between the sats and sub which cause dips and peaks around the XO point (2 octaves of your FR graph), which is also always mistaken as 'room modes'.

The Harmon papers don't address either of these situations, so following them as a placement guideline will almost always end up in less than ideal results.

Nearfield placement causes dips and peaks to be much more noticeable to the listener.

Multiple subs both (or all) play the same single, summed digital bass signal, that is, redirected bass combined with LFE. This is where the basic problems began, IMO.

It causes the 'headroom, SPL, lowest octave loudest output' posts to dominate subwoofer discussions.

Corner placement offers the most room gain, not the most accurate reproduction, and I've never seen a graph that proves otherwise.

Corner placement, more subs, colocated subs, bigger subs and PEQ to manipulate the grossly distorted FR, ported vs sealed, etc., comprises the vast majority of subwoofer posts...all for the sake of being able to 'handle' the redirected bass+LFE+10, summed, single digital bass signal.

If you use a separate sub for RB and can optimize the XO point and slope and you place it properly and adjust the relative phase and level properly...all for the best integration of RB with your sats, in your room...then, you can get as big and deep digging a sub as you wish and place it wherever and EQ it and run it as 'hot' as you like, etc., for LFE only.

An LFE only sub has immediately, 6 dB of headroom (115 dB vs 121 dB), can be LP filtered to retain the entire LFE signal, can be raised or lowered at any point to suit the program and is not nearly as sensitive to time smear or accuracy inequities...all without affecting the redirected bass sub.

You won't find any papers, anywhere, that discuss this routing scheme...why that is baffles me.

 

[frank manrique]

quote:

"Nearfield placement causes dips and peaks to be much more noticeable to the listener.

Multiple subs both (or all) play the same single, summed digital bass signal, that is, redirected bass combined with LFE. This is where the basic problems began, IMO.

It causes the 'headroom, SPL, lowest octave loudest output' posts to dominate subwoofer discussions.

Corner placement offers the most room gain, not the most accurate reproduction, and I've never seen a graph that proves otherwise.

Corner placement, more subs, colocated subs, bigger subs and PEQ to manipulate the grossly distorted FR, ported vs sealed, etc., comprises the vast majority of subwoofer posts...all for the sake of being able to 'handle' the redirected bass+LFE+10, summed, single digital bass signal.

An LFE only sub has immediately, 6 dB of headroom (115 dB vs 121 dB), can be LP filtered to retain the entire LFE signal, can be raised or lowered at any point to suit the program and is not nearly as sensitive to time smear or accuracy inequities...all without affecting the redirected bass sub.

You won't find any papers, anywhere, that discuss this routing scheme...why that is baffles me."

Wow...what gloomy prospective awaits fellows like yours truly......an individual who wants his multiple-subwoofer set up cake and eat it too!... :frowning:

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[BruceD]

To help identify and correct some of the time-based problems Dave mentions, I find the ETF software with it's 3D waterfall frequency chart, impulse response, and Energy Time curves to be quite useful.

Even if I'm only using a single sub for both re-directed and LFE bass, at least I'm controlling my Xover more accuratley with an active symmetrical 4th order L-R between my mains and sub, with a parametric EQ on the sub for modal peak reduction.

 

[dave alan]

Frank,

I think I can safely say that you are the exception to...well...ANY rule.

BruceD,

I certainly would appreciate knowing more about the software you mention, if you get a chance to post any specific info about your experiences with it. It sounds very interesting.

I've read everything you've posted about your outboard XO config, and it sounds like it works well for you. I'm setting up a similar deal now, with a separate LFE sub. The X over has separate selectable slopes for LP and HP. I'll post results when they're in.

 

[steve nn]

>>>Frank,

I think I can safely say that you are the exception to...well...ANY rule.

 

[SteveCallas]

Dave, I think you and I had a conversation about this very same topic on this forum a while ago. How exactly are you going about seperating the LFE from the RB? If I remember correctly, you built your own device that takes the preouts of each channel set to large and applies a crossover, then output that to your amp(s), and then sub out jack only outputs the LFE, yes?

 

[dave alan]

Steve,

There are 3 ways to do this:

1. Buy a Lex MC-12. It has 3 outs for subs...one for dedicated LFE and one each for left side and right side redirected bass.

2. The way I do it...set all speakers to 'large' and sub to 'yes' in the player. Run the SW out of the player to sub #1. Take the other 5 analog outs from the player to the preamp. Use an Outlaw ICBM between the preamp's outs and the amp's ins. The SW out of the ICBM goes to sub #2.

Sub #2 will get only redirected bass because no LFE is input to the ICBM, and sub #1 will get only LFE directly from the player.

3. Same settings in the player and the player's SW out to sub #1. Set the front left and right speakers to 'large' and center and surrounds to 'small' in the preamp. Use an outboard 2-way crossover to send the redirected bass to sub #2 from the LP outs of the crossover and the HP of the crossover goes to the front left and right speakers respectively. This can also be done using an ICBM.

I designed a 2 channel preamp with crossovers, slope selections, polarity switches and relative phase adjustment. One channel is optimized for LFE and the other for RB. Works very well.

I'm currently finishing subwoofers with those electronics built-in to the front panel, and will implement a stereo RB and discrete LFE config (3 subs) soon. I'll post results when available.

 

[frank manrique]

quote:

"There are 3 ways to do this:

1. Buy a Lex MC-12. It has 3 outs for subs...one for dedicated LFE and one each for left side and right side redirected bass."

Right on! Glad to see that Lexicon finally got it right. Too bad the damned things are so costly (and can't even do speaker set up automatically like some Denon and Pioneer top of the line receivers do now days)...and too bad my Lexi DC-1 :frowning: only puts out a summed subwoofer output...

"2. The way I do it...set all speakers to 'large' and sub to 'yes' in the player. Run the SW out of the player to sub #1. Take the other 5 analog outs from the player to the preamp. Use an Outlaw ICBM between the preamp's outs and the amp's ins. The SW out of the ICBM goes to sub #2.

Sub #2 will get only redirected bass because no LFE is input to the ICBM, and sub #1 will get only LFE directly from the player."

Umm...what player are you referring to?

"3. Same settings in the player and the player's SW out to sub #1. Set the front left and right speakers to 'large' and center and surrounds to 'small' in the preamp. Use an outboard 2-way crossover to send the redirected bass to sub #2 from the LP outs of the crossover and the HP of the crossover goes to the front left and right speakers respectively. This can also be done using an ICBM."

Well, I got that one covered...though my ICBM-1 is sort of dead... :frowning:

"I designed a 2 channel preamp with crossovers, slope selections, polarity switches and relative phase adjustment. One channel is optimized for LFE and the other for RB. Works very well."

What would be the cost for a multi-channel unit featuring all of those goodies? I want one!...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[JohnSmith]

AFAIK Lexicon MC-12 V4 does auto levels, distance, and full parametric EQ (AV Recievers only use a equalizer) not to sure about crossover size setting though.

 

[BruceD]

That sounds quite interesting!!
Have you talked about this before in any detail? I'd be interested in learning a bit more about it's design.

My current interest is learning about doing all of this while the signal is still in the digital domain, as well as parametric EQ for room modal bass peaks.

 

[frank manrique]

quote:

"AFAIK Lexicon MC-12 V4 does auto levels, distance, and full parametric EQ (AV Recievers only use a equalizer) not to sure about crossover size setting though."

Really? Wow! Man, that is really cool!
Still too bad the MC-12s are too rich for my blood, though given the opportunity there is no other pre/pro brand or model that I would rather have...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[JohnSmith]

Read Lexicon's pdf's for more info..the PEQ is done in the digital domain, wheras using the BFD will be a D-A-D(EQ)-A, Lexicon would be D(EQ)-A

"With the release of the MC-12 V4 EQ upgrade, Lexicon has raised the bar for automatic room equalization, providing a solution that demonstrably improves the listening experience. It is easy to operate and requires only a small amount of user interaction to achieve superior results. The V4 EQ upgrade is a simple and effective way of making rooms sound better. The new V4 EQ upgrade for the MC-12 is a powerful tool that allows the user to find and correct for problematic low frequencies in the listening space. V4 EQ uses thorough and advanced room analysis techniques and is completely integrated with existing processing so that no additional A/D/A conversion is required. The V4 EQ upgrade doubles the amount of processing available to the MC-12, and provides up to seven filters per channel for up to ten output channels. Four microphones, designed to meet Lexicon’s stringent requirements for room analysis, enable optimization for the entire listening area. The Lexicon V4 EQ upgrade provides exceptional results without the need for extra equipment or additional analyses."

http://www.lexicon.com/products/details.asp?ID=15

Way too expensive for me as well, I've only just bought a MC-1!

 

[frank manrique]

quote:

"Read Lexicon's pdf's for more info..the PEQ is done in the digital domain, whereas using the BFD will be a D-A-D(EQ)-A, Lexicon would be D(EQ)-A"

My good friend, after initially seeing the MC-12's "MSRP" I decided not to check out its specs and features because I just didn't want to cry! Thus my obvious display of ignorance about the admittedly superb product.

"Way too expensive for me as well, I've only just bought a MC-1!"

Lucky you!...I merely own a DC-1 (but it is a Version 4.0 )... :frowning:

-THTS

"...hi, my name is Frank...and am an SVS bassaholic...