2.1 Monitoring for Mastering? Possible?

[Dave Rose]

Would a pair of nearfield monitors and matched sub that can be switched on and off to check bass, be practical to master on as opposed to full range speakers? Basically, I am setting up a small Mastering studio, and have allocated £4000 (max) to spend on monitors and amp. I know there are a few active 2.1 systems available for around £1000-£4000, but not sure whether this is going to be accurate enough to master with. If not, what active monitors or monitor/amp combo would you suggest for £5000 or under...

Dave

[Ethan Winer]

I can't help with specific speaker suggestions, but I can tell you that for stereo it's better to use a pair of full-range speakers rather than "lesser" speakers that require a subwoofer.

--Ethan

[Bob Olhsson]

Single sub mixes make more work for mastering engineers...

[macc]

I know someone using the Blue Sky 2.1 system, he seems to be doing alright (not that I have heard his work but he's been in business for a while...)

Be interested to see what people think of it

[Virtalahde]

I'm often amused in how lightly people decide to install a subwoofer in their system but for some reason they never come to think of adding a supertweeter in it, or another midrange.

Bad subwoofer installation can do more harm than good. A pair of good subs coupling to good speakers.. Why not? But in these cases the main speakers are often capable of some good bass.

I think you either install a pair of subs for good or buy a set of speakers that have sufficient bass reproduction and learn to use them. Switching the sub in and out can be pretty confusing.

[bob katz]

Originally Posted by Dave Rose

It's me again, the guy who asks annoying questions that usually begin 'On a budget...' So...On a budget, would a pair of nearfield monitors and matched sub that can be switched on and off to check bass, be possible to master on? Basically, I am setting up a small Mastering studio, and have allocated £2000 (max) to spend on monitors and amp. I know there are a few active 2.1 systems available for around £1000, but not sure whether this is going to be accurate enough to master with. If not, what active monitors or monitor/amp combo would you suggest for £2000 or under...

Dave

Dave, I wish there were a cheaper answer. But truly, a single subwoofer for serious mastering is a compromise. There are four good reasons why you need two subwoofers. Here's the prime reason: It is IMPOSSIBLE to get an accurate frequency response with a single subwoofer. This is because electrical combination of signals produces a different response than the acoustical combination in the room. For example, if you take a pink noise signal in the left channel and adjust the subwoofer for a perfect crossover to that. Then do the same for the right. What happens when you play a mono, centered bass instrument through that system? It will probably be too loud!

The level of the bass in the room should be flat relative to the 1 kHz with all of these test signals:

left channel only pink noise
right channel only pink noise
correlated dual channel pink noise equal in level and phase between the two channel
uncorrelated dual channel pink noise equali in level and with random phase between the two channels.

If you must use a single subwoofer, probably you should adjust it to be about 1 dB down because most bass tracks are mono in the center. But mono subwoofer will always be a compromise.

Then there's the question of how it translates to home systems which do have a single subwoofer. You should always check in mono regardless to see if the bass is cancelling or summing poorly.

Hope this helps,


Bob

[Pascal Sijen]

Originally Posted by bob katz

It is IMPOSSIBLE to get an accurate frequency response with a single subwoofer. This is because electrical combination of signals produces a different response than the acoustical combination in the room.

I am going to have to disagree. In a bass-managed system, where you are using a single mono subwoofer signal, derived and summed from a stereo signal, and feeding a single or multiple mono subwoofers, there should be no inherent difference in bass level when compared to using stereo subs, other than the variables that using stereo subs introduces.

In fact, because low frequencies from multiple channels (stereo, surround, whatever) are summed electrically, instead of acoustically in the studio, low frequency phase issues between channels are resolved in the most absolute and accurate way possible - electrically. This is with the least variables, certainly much better than the acoustic variations between studios, and is what has been found to be most accurate in studies done by Harman and others.

If a subwoofer is calibrated correctly, with its pass-band level, matching the pass band level of the monitors, there should be no issues with regard to level in a stereo, 5.1, 7.1, etc. setup.

This is why bass-management is recommend by THX, Dolby and others. This is also why we incorporate this design in our monitoring systems.
Blue Sky

Feel free to e-mail me directly, if you have any questions: pascal@abluesky.com

Cheers!

[bob katz]

Dear Pascal: It's ok for you to disagree but then you have to argue with both Tom Holman and me and others. It's an acoustic impossibility for single subwoofer to match the power levels of two channels of sub with either correlated or uncorrelated signals-----Because of the acoustic coupling in a room between two subwoofers it is impossible for a single subwoofer with an electrical combination to produce the same power-measured results with the same signal.

I could find the quote from Tom Holman's book, but it's something like "Electrical and acoustical combination of signals produce different results."

Remember, bass information is not always centered and correlated.

Bass management is ok! But it is wrong to assume that the alignment of a single subwoofer in a bass managed system produces the same results as a fully discrete and separate two channel system. All you have to do is measure and perform a test to see that you're wrong. Be sure to test with both correlated and uncorrelated bass information and with subwoofers that are separated as far apart as the satellites.

BK

[Pascal Sijen]

Originally Posted by bob katz

Dear Pascal: It's ok for you to disagree but then you have to argue with both Tom Holman and me and others. It's an acoustic impossibility for single subwoofer to match the power levels of two channels of sub with either correlated or uncorrelated signals-----Because of the acoustic coupling in a room between two subwoofers it is impossible for a single subwoofer with an electrical combination to produce the same power-measured results with the same signal.

I could find the quote from Tom Holman's book, but it's something like "Electrical and acoustical combination of signals produce different results."

Remember, bass information is not always centered and correlated.

Bass management is ok! But it is wrong to assume that the alignment of a single subwoofer in a bass managed system produces the same results as a fully discrete and separate two channel system. All you have to do is measure and perform a test to see that you're wrong. Be sure to test with both correlated and uncorrelated bass information and with subwoofers that are separated as far apart as the satellites.

BK

I never said it was the same. I just said there are less variables and therefore it is more consistent, and more absolute. Using stereo subwoofers, or stereo full-range speakers, will generate different results in different rooms and therefore only adds to the chaos and variables.

Cheers!

[Pascal Sijen]

Originally Posted by bob katz

Dear Pascal: It's ok for you to disagree but then you have to argue with both Tom Holman and me and others. It's an acoustic impossibility for single subwoofer to match the power levels of two channels of sub with either correlated or uncorrelated signals-----Because of the acoustic coupling in a room between two subwoofers it is impossible for a single subwoofer with an electrical combination to produce the same power-measured results with the same signal.

I could find the quote from Tom Holman's book, but it's something like "Electrical and acoustical combination of signals produce different results."

Remember, bass information is not always centered and correlated.

Bass management is ok! But it is wrong to assume that the alignment of a single subwoofer in a bass managed system produces the same results as a fully discrete and separate two channel system. All you have to do is measure and perform a test to see that you're wrong. Be sure to test with both correlated and uncorrelated bass information and with subwoofers that are separated as far apart as the satellites.

BK

One additional note regarding Tom Holman: In all my conversations with Tom, when I worked with him at THX, he was always a strong proponent of bass-management (mono sub). The argument about "electrical summation and acoustic summation produce different results" is his argument for bass-management, not against. This is why TMH sells a bass-management box, why he included bass-management in the home THX spec and why we incorporated it into the THX pm3 spec (a professional monitoring spec).

You can find a white paper, that goes along with his bass-management box, on his website, which also includes the reference you site: Bass Manager Information

I hope this helps explain my views more clearly.

Cheers!

[kjg]

Originally Posted by Pascal Sijen

I never said it was the same. I just said there are less variables and therefore it is more consistent, and more absolute. Using stereo subwoofers, or stereo full-range speakers, will generate different results in different rooms and therefore only adds to the chaos and variables.

Cheers!

A mono sub is an approximation since it cannot reproduce uncorrelated LF content. Could be that that oversimplified approximation will be more "consistent", but it is certainly not more "absolute".
I'd rather take the time to deal with the extra variables than accepting a simplification of the 2ch signal (in the context of mastering that is - since we are on the mastering forum).

kjg

[bslobodian]

Originally Posted by Pascal Sijen

This is with the least variables, certainly much better than the acoustic variations between studios, and is what has been found to be most accurate in studies done by Harman and others.

Pascal, I don't know what Harman studies you're refering to, but the conclusion of Subwoofers: Optimum Number and Locations by Todd Welti will go for two subs as LFE. Stereo subs are not considered in that studie though. "One subwoofer at each wall midpoint is the best in terms of Std, Max-ave and Max-min but does not support low frequencies particularly well. Two subwoofers, at opposing wall midpoints, performs very nearly as well as four at the midpoints and gives a much better LF factor. One subwoofer in each corner also has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint, in terms of Std, Max-ave and Max-min. If cost and aesthetics are considered, subwoofers at 2 wall midpoints is preferred. Bernard Slobodian

[Pascal Sijen]

Originally Posted by kjg

A mono sub is an approximation since it cannot reproduce uncorrelated LF content. Could be that that oversimplified approximation will be more "consistent", but it is certainly not more "absolute".
I'd rather take the time to deal with the extra variables than accepting a simplification of the 2ch signal (in the context of mastering that is - since we are on the mastering forum).

kjg

Again, this is wrong. A mono subwoofer will reproduce uncorrelated LF content. However, if there are phase issues which cancel electrically in a bass-managed / mono SUB setup (which you can then not hear), they should, in a perfect room, also cancel acoustically. The problem is, all rooms are different, not perfect, and you can put out of phase LF content in a stereo mix, which may be audible in one room, and cancel in another.

Hear is a quote from Holman's white paper for his bass-management box:
"Bass management electrically combines the bass from all of the channels together. Even if you had full range monitors, with say a subwoofer spliced to each of the five or more main channels, you would then be hearing an acoustical summation of the multichannel bass in your room. The two levels, acoustically summed or electrically summed, could be very different. Let's say front and surround channels are out-of-phase with each other. Then electrically they will cancel, but acoustically, depending on where you are standing, you may hear them sum (the room standing wave adds its own phase shifts!). Thus you might hear bass in your studio that would be completely canceled out at home (happened to a famous DVD-V production
that had to be recalled)."

Cheers!

[Pascal Sijen]

Originally Posted by bslobodian

Pascal, I don't know what Harman studies you're refering to, but the conclusion of Subwoofers: Optimum Number and Locations by Todd Welti will go for two subs as LFE. Stereo subs are not considered in that studie though. "One subwoofer at each wall midpoint is the best in terms of Std, Max-ave and Max-min but does not support low frequencies particularly well. Two subwoofers, at opposing wall midpoints, performs very nearly as well as four at the midpoints and gives a much better LF factor. One subwoofer in each corner also has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint, in terms of Std, Max-ave and Max-min. If cost and aesthetics are considered, subwoofers at 2 wall midpoints is preferred. Bernard Slobodian

Harman has a bunch of papers that were done by Todd Welti and also Floyd Toole about room EQ, subwoofer location, number of subwoofers, etc., and all of them start with the correct assumption that a mono bass-managed subwoofer signal is best.

[kjg]

Originally Posted by Pascal Sijen

Again, this is wrong. A mono subwoofer will reproduce uncorrelated LF content.

Of course not. It will only reproduce the M component of the uncorrelated signal since the S component will cancel out and therefore remain undetected/unevaluated. A 100% uncorrelated signal will not be reproduced at all.

I'm sure the Blue sky/desk/whatever range is perfectly useful for mixing and other applications, but in mastering uncorrelated LF content needs to be reproduced instead of discarded, so it can be evaluated and dealt with in the most appropriate way.

[Pascal Sijen]

Originally Posted by kjg

Of course not. It will only reproduce the M component of the uncorrelated signal since the S component will cancel out and therefore remain undetected/unevaluated. a 100% uncorrelated signal will not be reproduced at all.

I'm sure the Blue sky/desk/whatever range is perfectly useful for mixing and other applications, but in mastering uncorrelated LF content needs to be reproduced instead of disregarded, so it can be evaluated and dealt with in the most appropriate way.

OK, let me try this one more: If you have two LF signals that are out of phase to each other, and they cancel electrically 100%, they should also cancel acoustically. If they don't, it is because the room's acoustics (etc.) are not 100% perfect (and they never are). So in the basic sense, you are hearing distortion in the acoustic summation.

1 + -1 = 0 (the electrical version).

if, 1 + -1 = .2 (an example of some acoustical variation), then this is not accurate, but it is different from the electrical version. Different is not better, just different. And, every room is going to be different.

Also, an uncorrelated signal, doesn't necessarily mean out of phase and therefore a mono derived subwoofer can reproduce uncorrelated bass information (which is the purpose of bass-management - summing LF signals from 2 or more channels).

Ok, I hope that helps explain it better.

Cheers!

[kjg]

Originally Posted by Pascal Sijen

Harman has a bunch of papers that were done by Todd Welti and also Floyd Toole about room EQ, subwoofer location, number of subwoofers, etc., and all of them start with the correct assumption that a mono bass-managed subwoofer signal is best.

They start with the assumption that a mono sub is best? These papers can hardly be serious evaluation of the advantages and disadvantages of stereo subs/stereo full range system then, now can they?

[Pascal Sijen]

Originally Posted by kjg

They start with the assumption that a mono sub is best? These papers can hardly be serious evaluation of the advantages and disadvantages of stereo subs/stereo full range system then, now can they?

I am getting the feeling that you think you are right and we are certainly allowed to disagree.

[kjg]

Originally Posted by Pascal Sijen

OK, let me try this one more

<snip>

Ok, I hope that helps explain it better.

Thank you for trying once more... I'll do the same.

If a mix contains significant uncorrelated LF content before mastering and the ME uses a mono sub with his non full range system, he will not detect this LF content and will therefore not be able to deal with it in the most appropriate way. Resulting in a master with uncorrelated LF content that was not evaluated and might cause trouble.

[Pascal Sijen]

Originally Posted by kjg

Thank you for trying once more... I'll do the same.

If a mix contains significant uncorrelated LF content before mastering and the ME uses a mono sub with his non full range system, he will not detect this LF content and will therefore not be able to deal with it in the most appropriate way. This will resulting in a master with uncorrelated LF content that was not evaluated and might cause trouble.

It is only when two or more signals, that are out of phase to each other and are then summed electrically, which are not audible - and they shouldn't be audible in your mastering studio either. Uncorrelated signals are certainly audible on a mono subwoofer.

[bob katz]

Originally Posted by Pascal Sijen

One additional note regarding Tom Holman: In all my conversations with Tom, when I worked with him at THX, he was always a strong proponent of bass-management (mono sub). The argument about "electrical summation and acoustic summation produce different results" is his argument for bass-management, not against.

Let's not say "bass management" because we're not arguing the viability of bass management. We're arguing whether a 2.1 system is viable for a mastering studio. I say no. Apparently some people say yes.

Specifically we're arguing whether a 2.1 (versus, I guess the term would be 2.2) system is viable. Both are bass managed so that's not the argument.

Is Tom's argument an attempt to support a mono subwoofer or two independent subwoofer channels? What does he say about his 10.2 system? Doesn't he say it sounds better?

The measurements and the theory support the obvious differences between two independent subwoofer channels versus combining them electrically. In other words, there is a meaningful difference between a full range stereo system and a 2.1 system. The 2.1 system will respond very differently to mono bass versus uncorrelated bass in the program material. The bass level will typically be a dB or more higher in the 2.1 system when playing mono centered bass material versus uncorrelated while the spaced full range system's performance will depend on the coupling and spacing of the two subwoofers.

For me this is a simple justification for a 2.2 system when the standard at the moment is the full-range discrete stereo. Furthermore, it's easier for a mastering engineer to have a discrete system and test how the program will translate by combining channels than the reverse. The mastering engineer with the 2.1 system is at a disadvantage because he cannot see how the program will translate to a discrete, separate system.

Bass is the final frontier, and bass accuracy is what separates the mastering men from the mastering boys (or the mastering women, the same applies). We have enough trouble dealing with room modes than to add the complication of not being able to properly judge stereo bass information.

At least you acknowledge that there is a measurable and audible difference, while the gentleman from Blue Sky (which makes excellent loudspeakers, by the way) was claiming that there is no audible or performance difference, if I read his post correctly.

By the way, I cite THREE additional reasons why stereo subwoofers sound and perform better than a mono sum in my book.

That's my position.

BK

[bob katz]

[quote from Tom Holman]

Thus you might hear bass in your studio that would be completely canceled out at home (happened to a famous DVD-V production
that had to be recalled)."[/I]

Cheers![/QUOTE]

Which is why professional mastering engineers using discrete stereo systems (or discrete subwoofers in a surround context) test their masters with folddown (or mono), as we have done for many years.

[bob katz]

Originally Posted by kjg

Thank you for trying once more... I'll do the same.

If a mix contains significant uncorrelated LF content before mastering and the ME uses a mono sub with his non full range system, he will not detect this LF content and will therefore not be able to deal with it in the most appropriate way. Resulting in a master with uncorrelated LF content that was not evaluated and might cause trouble.

This is 100% correct and is the reason and the need for having a discrete pair of subwoofers. There are many classical recordings with full range stereo content made with spaced microphones that are designed to be reproduced over a full range system and which sound worse when the bass is combined. The very richness of the uncorrelated material is part of its intended virtue.

All the other arguments (about unpredictabilty, variance from room to room, etc.) aside. Translation is the key, and a mono test can be performed with split woofers, but the reverse cannot be done with a single combined woofer. Furthermore, as I said, the bass levels will typically be different and the bass alignment in a mono subwoofer room will be fundamentally incorrect depending on the amount of uncorrelated bass material in the source and the amount that cancels in mono.

BK

[Pascal Sijen]

I think we are going around in circles. But, let me just finish by saying:

* In a perfect studio - with no room modes and perfectly linear frequency response, there should be no difference in level or frequency response (except for some theoretical interference, relating to the distance between stereo subs), when using a mono subwoofer or stereo subwoofers. Phase relationships between audio signals should cancel or sum both acoustically or electrically.

* Tom's point and my point as well, is that because no rooms are perfect and the acoustics vary, electrical summation of LF is more reliable, more repeatable and it is more absolute.

I enjoyed the back and forth...

Cheers!

[Ethan Winer]

Good thread guys, and this is addressed at nobody in particular:

I have a single killer SVS sub in my living room home theater system, and I have an amazingly flat response all around the room. Graph below. But - and this is a big one - I have 49 acoustic panels, most of which are bass traps. This is in a 25 by 16 room with a peaked ceiling that reaches 11 feet in the center. Most people are unwilling or unable to incorporate as many bass traps as are really needed, especially in a home studio setup. But it's definitely possible to get great results from one sub, two subs, or even 16 subs as Floyd Tools half-jokingly recommends.

--Ethan

[Pascal Sijen]

Originally Posted by Ethan Winer

But it's definitely possible to get great results from one sub, two subs, or even 16 subs as Floyd Tools half-jokingly recommends.

As a manufacturer of subwoofers, I am a strong proponent of the use of 16 (or even more) subwoofers!

[Ethan Winer]

LOL, and as a manufacturer of bass traps I am a strong proponent of 40 or more bass traps.

[bob katz]

Originally Posted by Ethan Winer

LOL, and as a manufacturer of bass traps I am a strong proponent of 40 or more bass traps.

Definitely the two of you should get together. Maybe you can put a sub inside a bass trap and kill two birds with one stone.

Ironically, the issue being discussed here is being confused with a separate issue that two or more subs optimally located in a room can produce a more linear response. In other words, a good case can be made that two optimally placed subs are better than one in terms of evening out room nodes. This may be true regardless of whether you subscribe to the notion that the signal should be stereo or mono.

BK

[Bob Olhsson]

Additionally there is still belief in this insane bit of consumer hi-fi marketing fluff from the early 1960s that suggests low frequencies are non-directional and hence need not be reproduced in stereo when science tells us this is simply not true.

[Pascal Sijen]

Originally Posted by Bob Olhsson

Additionally there is still belief in this insane bit of consumer hi-fi marketing fluff from the early 1960s that suggests low frequencies are non-directional and hence need not be reproduced in stereo when science tells us this is simply not true.

They are not non-directional, but to be technically accurate, they are omnidirectional. More information here: A common misconception about subwoofers

Cheers!