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View Poll Results: Is there any value comparing the sound quality of subs without the 'right conditions'
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post #31 of 70 Old 04-03-2011, 09:39 PM
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Quote:
Originally Posted by Sobhano View Post

If I may, let's say the two subs have a flat FR..... and all else as equal as possible, would they sound the same?

I think if all else is equal, then there are no reasons left for them to sound different. Peter Aczel from the Audio Critic used this same argument to explain why both cheap and expensive amplifiers can sound indistinguishable if operated under the same conditions.

However, just like the more powerful amplifier, the bigger sub will indeed sound better than the smaller one when asked to provide more output than what the little one was designed to supply. Tom Nousaine came to the same conclusion when he tested the entire size lineup of one Velodyne subwoofer model. The smallest sub sounded just like the largest until levels were increased.
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post #32 of 70 Old 04-03-2011, 11:16 PM
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Originally Posted by dominguez1 View Post

...or should you look to other characteristics of the sub that help indicate that it has the capability (flat response, headroom, output, extension, etc.) to have good sound quality?

FR graph in the open or standard room answers a lot of other variables too but this still doesn't tell how "fast" or the group delay of a sub neither its’ tune.
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post #33 of 70 Old 04-04-2011, 10:56 AM - Thread Starter
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Originally Posted by stereo2.0 View Post

I think if all else is equal, then there are no reasons left for them to sound different. Peter Aczel from the Audio Critic used this same argument to explain why both cheap and expensive amplifiers can sound indistinguishable if operated under the same conditions.

However, just like the more powerful amplifier, the bigger sub will indeed sound better than the smaller one when asked to provide more output than what the little one was designed to supply. Tom Nousaine came to the same conclusion when he tested the entire size lineup of one Velodyne subwoofer model. The smallest sub sounded just like the largest until levels were increased.

This is good information and helps answer my question...thanks.

So, to summarize so far:

The main characteristics that make up Sub Sound Quality are:

1. Flat Frequency Response (Reference FR)
2. Extension (obviously, this is related to FR, but wanted to break it out separately)
3. Output (also related to FR)
4. Distortion or 'Audible Noise'
5. Group Delay (Transient Response) - the subs ability to stop and start a given frequency (tight vs loose sound)
6. Power Compression - As dynamic content changes in the source, the subs ability to maintain a consistent (flat) FR, maintain phase, etc.

So back to my theoretical question:

If two different subs with different designs, drivers, and amplification have the exact same FR, Extension, Output, Distortion, Group Delay, and Power Compression characteristics, will they sound exactly the same?

I believe the answer is Yes.

So, what does this all mean?

Any differences we hear when we compare the sound quality of subs fall into one of these 6 major categories. The characteristic that we 'hear' the most is the frequency response of the sub. Assuming that we can setup the 'right conditions' in a room so that frequency response is as flat as possible for all subs, we can then compare them based on the other 5 characteristics. Output and Extension are really a function of FR, and so these can be easily represented in graphs, etc.

It’s at this point where it will be easy to determine where the subs rank against each other; the flattest response and deepest extension for your desired output will have the best sound quality (assuming the other characteristics are within reason).

But perhaps the subs all have negligible differences for FR, extension and output, which one has the best SQ? You can then look at Distortion, Group Delay, and Power Compression.

Unlike FR, these cannot be adjusted with an EQ and are fixed characteristics based on the flat FR. Because these are fixed, you will have the most variability among these characteristics across the sub's frequency response. Each sub will have its own recipe for these characteristics and all with their own advantages and disadvantages based on their 'recipe'.

Assuming that Distortion, Group Delay, and Power Compression are all within ‘reason’ AND they all have negligible differences for FR, extension and output, I believe it is at this point that subjectivity and preference come into play. Since each of the subs will have its own recipe for distortion, group delay, and power compression across their frequency response, it now becomes a matter of taste.

And it is at this point where subjective comments have some meaning.

Comments? Again, I’m no expert and could completely be way off base…but it sounds intuitive.
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post #34 of 70 Old 04-04-2011, 11:57 AM
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I think you're spot-on Dominguez except for one thing.

I think transient response does play a role...and we have great difficulty even quantifying it with numbers right now...much less accurately measuring it.

But I think this again comes down to accuracy.....how accurately can the driver trace increases and decreases in the input-signal waveforms (especially rapid ones). I think this is where big payoffs are to be had for large drivers (15-18") in well-damped, sealed alignments....as they maintain a level of control over the driver that simply cannot be accomplished via a tuned port.

I have heard subwoofers that played loudly, and had a flat frequency response, but that (even when in phase) sounded less impactful than others who were calibrated to the same response and referenced at the same level. It's almost like its lack of ability to trace the waveform caused the peak of the waveform...or some other dynamic quality about it, to be removed or reduced.

Again....the equipment does not exist to measure this right now... the resolution a which we are accurately measuring would have to go WAAAY up. But I think this component does play a part.

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post #35 of 70 Old 04-04-2011, 12:03 PM
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"If two different subs with different designs, drivers, and amplification have the exact same FR, Extension, Output, Distortion, Group Delay, and Power Compression characteristics, will they sound exactly the same?

I believe the answer is Yes." -Dominguez1

I'm not entirely sure.

Having played with drum kits quite a bit (though I've never been accused of being a 'drummer' ), I see how much diaphragm weight and other characteristics of the drum heads can alter or effect the sound the kit produces. Just looking at the kick...you can have two identical shells (let's say a 28-incher for S&G's), but with two different skins on (at the same tension)...they sound notably different. They measure the same on the house RTA, and on the Freq-analyzer in the digital board....but they sound different.

I guess I'm splitting hairs about the 'distortion' component of your list....I guess I'm trying to say that the distortion will never quite be exactly the same between two different subs.

I can answer, a categorical 'Yes', as it stands for most people...I think most listeners would perceive the two subs as sounding the same if those factors are equal.

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post #36 of 70 Old 04-04-2011, 04:16 PM - Thread Starter
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Quote:
Originally Posted by BufordTJustice View Post

I think you're spot-on Dominguez except for one thing.

I think transient response does play a role...and we have great difficulty even quantifying it with numbers right now...much less accurately measuring it.

But I think this again comes down to accuracy.....how accurately can the driver trace increases and decreases in the input-signal waveforms (especially rapid ones). I think this is where big payoffs are to be had for large drivers (15-18") in well-damped, sealed alignments....as they maintain a level of control over the driver that simply cannot be accomplished via a tuned port.

I have heard subwoofers that played loudly, and had a flat frequency response, but that (even when in phase) sounded less impactful than others who were calibrated to the same response and referenced at the same level. It's almost like its lack of ability to trace the waveform caused the peak of the waveform...or some other dynamic quality about it, to be removed or reduced.

Again....the equipment does not exist to measure this right now... the resolution a which we are accurately measuring would have to go WAAAY up. But I think this component does play a part.

What's the difference between transient response and group delay? Are they both audibly perceived as the 'tightness' or 'looseness' of the sub?
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post #37 of 70 Old 04-04-2011, 09:36 PM
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I believe group delay is a measure of transient response (although affected by phase and also FR). Also - It's probably not important or correct to separate extension from FR (they are the same thing).

I agree that if all measurements you listed (1-6) are the same for two subs then they will sound the same. However, for those measurements to be the same you would need to have the exactly the same subwoofer. Two different subs will not measure precisely the same for all of these parameters. That is why these were the measurments taken by Ilkka in the old Home Theatre Shack subwoofer tests.
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post #38 of 70 Old 04-05-2011, 07:40 AM - Thread Starter
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Originally Posted by Avgass View Post
I believe group delay is a measure of transient response (although affected by phase and also FR). Also - It's probably not important or correct to separate extension from FR (they are the same thing).

I agree that if all measurements you listed (1-6) are the same for two subs then they will sound the same. However, for those measurements to be the same you would need to have the exactly the same subwoofer. Two different subs will not measure precisely the same for all of these parameters. That is why these were the measurments taken by Ilkka in the old Home Theatre Shack subwoofer tests.
Okay, for now I'll lump Group Delay/Transient response together (edit my post), until someone tells me differently.

I agree that FR and extension are really the same. However, I thought it was important to make that distinction because many people can have a relatively flat frequency response, but how far does it extend to, and also what is the max output for that extension? Just things for the average joe to make sure and consider...
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post #39 of 70 Old 04-05-2011, 01:24 PM
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Quote:
Originally Posted by dominguez1 View Post

What's the difference between transient response and group delay? Are they both audibly perceived as the 'tightness' or 'looseness' of the sub?

They are similar. I'd posit that the metric of 'group delay' is an attempt at measuring transient response. For the purposes of this discussion, I think it's fair to call them the same.

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post #40 of 70 Old 04-05-2011, 04:10 PM
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I think loose or tight is more about the other end of the transient response: How long after the signal stops does the driver stop moving and making noise. I've doen a little light googling on group delay and I think that there is a point where the delay is enough that things sound out of sync with each other. I suspect it sounds wrong without being readily describable for the untrained like me.
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post #41 of 70 Old 04-06-2011, 01:23 PM - Thread Starter
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So, I believe we've come up with a good basis of what makes up sub sound quality.

My next question is, what are the 'right conditions' to compare sound quality; specifically by ear?

Here are my thoughts:

1. Room conditions must be exactly the same; same location, same furniture, etc.
2. All subs should be level matched
3. Two identical subs should be used per type of sub (if possible) to help acheive a flat response
4. The subs should be EQ'd to as flat as response as possible (via Audyssey, SMS-1, etc.)
5. The subs being compared are all compared at the same time

What did I miss?

A second question comes to mind as well, in terms of the characteristics we defined as sound quality; who is best to make comparisons between subs for sub sound quality?

1. The people who have tested these subs in the 'right conditions' (obviously)
2. The manufacturer of the sub when comparing between different subs that they manufacture ; the manufacturer should know how the sub is designed and its capability (the 6 characteristics) for good sound quality.
3. Anyone with accurate, non-room specific data to support their claims

Anyone else?

Who should we take with a grain of salt when they talk about/compare sub sound quality?

1. Anyone comparing subs based on their sub sound quality preference, not sound quality reference.
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post #42 of 70 Old 04-06-2011, 02:29 PM
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I find it interesting that 38% actually believe they can determine the true Sound Quality difference between two subs using uncontrolled tests.

It is not "open-minded" to reject knowledge - Bob Lee
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post #43 of 70 Old 04-06-2011, 03:22 PM
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Originally Posted by penngray View Post

I find it interesting that 38% actually believe they can determine the true Sound Quality difference between two subs using uncontrolled tests.

Can you read? That's not what the poll asked. It asked if there was any value to it, not being the sole determining approach.
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post #44 of 70 Old 04-08-2011, 01:22 AM
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Quote:
Originally Posted by dominguez1 View Post
so, i believe we've come up with a good basis of what makes up sub sound quality.

My next question is, what are the 'right conditions' to compare sound quality; specifically by ear?

Here are my thoughts:

1. Room conditions must be exactly the same; same location, same furniture, etc.
2. All subs should be level matched
3. Two identical subs should be used per type of sub (if possible) to help acheive a flat response
4. The subs should be eq'd to as flat as response as possible (via audyssey, sms-1, etc.)
5. The subs being compared are all compared at the same time

what did i miss?

A second question comes to mind as well, in terms of the characteristics we defined as sound quality; who is best to make comparisons between subs for sub sound quality?

1. The people who have tested these subs in the 'right conditions' (obviously)
2. The manufacturer of the sub when comparing between different subs that they manufacture ; the manufacturer should know how the sub is designed and its capability (the 6 characteristics) for good sound quality.
3. Anyone with accurate, non-room specific data to support their claims

anyone else?

Who should we take with a grain of salt when they talk about/compare sub sound quality?

1. Anyone comparing subs based on their sub sound quality preference, not sound quality reference.
+1

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post #45 of 70 Old 04-08-2011, 05:54 AM
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Originally Posted by netudki View Post
Can you read? That's not what the poll asked. It asked if there was any value to it, not being the sole determining approach.
Yep, I can read......

"Is there any value comparing the sound quality of subs without the 'right conditions' "


"any value" would imply that people can get accurate results without "right conditions" ....which is false.

There is no grey area, you either do it right or its inaccurate.

The Poll simply tells me people really know squat about how important controlled conditions are in terms of audio testing. I guess I should have posted I was not surprised.

Its now past 40%.... so the one conclusion from this is that there is a lot of education that is needed out there.

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post #46 of 70 Old 04-08-2011, 07:56 AM
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Hmmm... Maybe I voted wrong. In the first post, the OP described "right conditions" as being room-related. I voted "yes" because you should be able to take the sub outside and do close-mic measurements to take the room out of it. Or, swap subs in the room to see how they compare in your environment, whatever that may be, and so there is "some value" in doing that. So technically, I feel most of us should be able to create "right enough" conditions. I agree with penngray that accurate assessment requires reliable, matched and repeatable test conditions. At least. Have to ponder more...

Regarding transient response and group delay, a thorough discussion may be beyond this thread, but for starters they are related but not the same. Linear phase across the bandwidth provides constant group delay, and that leads to good pulse response. If the group delay is not constant, then different frequencies will arrrive at different times, corrupting something like a square wave. Constant group delay is critical in radar/lidar systems; I am not so sure it is as critical in a subwoofer or with music in general. I will say I have speakers with good pulse response, but honestly I bought them because I liked their sound, which is the culmination of many factors (or parameters, if you prefer).

Transient response usually encompasses other things, like rising and falling edges, attack and decay, flat-top response, system Q, etc. What "fast" means to a subwoofer seems to be a matter of debate; what I have found by measuring and listening is that a "fast" attack" rarely seems needed though it is helpful to have the crossover pahse-matched to the mains for step (pulse) integrity, but controlling the ringing on the decay seems to do more to make the sound (and measurements) better. I have no hope of defining "better" for anybody but me so will just leave it there...

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post #47 of 70 Old 04-08-2011, 08:07 AM
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Originally Posted by DonH50 View Post

Hmmm... Maybe I voted wrong. In the first post, the OP described "right conditions" as being room-related. I voted "yes" because you should be able to take the sub outside and do close-mic measurements to take the room out of it. Or, swap subs in the room to see how they compare in your environment, whatever that may be, and so there is "some value" in doing that. So technically, I feel most of us should be able to create "right enough" conditions. I agree with penngray that accurate assessment requires reliable, matched and repeatable test conditions. At least. Have to ponder more...

To be honest....

You probably voted right for yourself because "Any value" is highly subjective.

The science side in me just says not controlling the test leaves too many holes and a high probability of failure so I have too just deem it as no value.

The subjective side of me says "Are you kdding, Who has time or the tools to setup proper testing"......I get that and I get how people believe something is better then nothing but in audio this leads to incorrect conclusions all the time.

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post #48 of 70 Old 04-08-2011, 08:14 AM
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Agreed on all counts. The problem with "something is better is nothing" is that, if you don't really understand what's going on and how the test conditions/environment are influencing the results, the test is worse than useless: it's misleading and can steer you wrong.

And yes, I have done that, and not with a subwoofer, but with something much more costly... The wrong test can be much worse than no test.

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post #49 of 70 Old 04-08-2011, 08:25 AM
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Originally Posted by DonH50 View Post

Agreed on all counts. The problem with "something is better is nothing" is that, if you don't really understand what's going on and how the test conditions/environment are influencing the results, the test is worse than useless: it's misleading and can steer you wrong.

And yes, I have done that, and not with a subwoofer, but with something much more costly... The wrong test can be much worse than no test.

lmao, you and me both.

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post #50 of 70 Old 04-08-2011, 08:59 AM
 
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A flat frequency response is the Reference for sound quality. There are an infinite number of sound preferences, but only one reference.

It's funny because a flat response is still a preference. Just as a house curve is a preference. My preference is to have a perceptually flat response (ie a response that sounds flat to the human ear), rather than a measurably flat response. Those are preferences.

Just because a subwoofer measures flat does not necessarily mean it will sound good. Not at all. That is some urban legend that needs to be put to rest. You can have a flat response +- 2 dB's and the response could still have excessive ringing that only bass traps can reliably address. If bass notes linger and decay and swamp subsequent notes then it doesn't matter how flat your response is, the issue will remain unless treated. You can have several systems, all with flat responses at the seats and they could sound different based on the modal resonances in the room and how they interact with the subwoofer.

A response with little ringing, THAT, is a reference, for me. You could have a house curve with little ringing in the low bass that still sounds infinitely better than a measured flat response. Of course, this is all subjective. What sounds good is inherently subjective, that goes for a flat response, house curve, a boost in the low bass, etc. I've heard subwoofers that have been EQ'ed flat that sounded absolutely horrible. I've also heard systems with considerable bass trapping that produced extremely articulate bass but the measured response wasn't nearly as flat as you would think.

The room governs the sound quality of the sub. You place *any* subwoofer in a room with modal ringing that lasts 1 second then the entire exercise is superfluous. It will sound boomy, even if you EQ'ed the sub flat.
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post #51 of 70 Old 04-08-2011, 12:33 PM
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Quote:
Originally Posted by goneten View Post

You place *any* subwoofer in a room with modal ringing that lasts 1 second then the entire exercise is superfluous. It will sound boomy, even if you EQ'ed the sub flat.

If you EQ'ed it flat when using a fast sweep speed, won't you get a totally different frequency response if you instead used a slow sweep speed? (i.e. slow enough to excite the 1 second ringing frequency longer)

I'm thinking part of the boom sound is not just due to the long decay, but also because the amplitude will actually be higher when the ringing frequency is hit with a steady state signal. If so, then EQ'ing it flat with a very slow sweep can could help tame the boom sound, but then the sub will tend to sound anemic when short duration signals at the ringing frequency are presented.

Long standing question: Do effective passive bass traps even exist?
I thought you needed an active noise canceling sub (i.e. one with a built-in microphone) to dampen low frequency modes in a typical living room.
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post #52 of 70 Old 04-08-2011, 12:54 PM
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Quote:
Originally Posted by goneten View Post

It's funny because a flat response is still a preference. Just as a house curve is a preference. My preference is to have a perceptually flat response (ie a response that sounds flat to the human ear), rather than a measurably flat response. Those are preferences.

Just because a subwoofer measures flat does not necessarily mean it will sound good. Not at all. That is some urban legend that needs to be put to rest. You can have a flat response +- 2 dB's and the response could still have excessive ringing that only bass traps can reliably address. If bass notes linger and decay and swamp subsequent notes then it doesn't matter how flat your response is, the issue will remain unless treated. You can have several systems, all with flat responses at the seats and they could sound different based on the modal resonances in the room and how they interact with the subwoofer.

A response with little ringing, THAT, is a reference, for me. You could have a house curve with little ringing in the low bass that still sounds infinitely better than a measured flat response. Of course, this is all subjective. What sounds good is inherently subjective, that goes for a flat response, house curve, a boost in the low bass, etc. I've heard subwoofers that have been EQ'ed flat that sounded absolutely horrible. I've also heard systems with considerable bass trapping that produced extremely articulate bass but the measured response wasn't nearly as flat as you would think.

The room governs the sound quality of the sub. You place *any* subwoofer in a room with modal ringing that lasts 1 second then the entire exercise is superfluous. It will sound boomy, even if you EQ'ed the sub flat.

Wouldn't an AntiMode 8033 mostly eliminate the ringing problem?
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post #53 of 70 Old 04-08-2011, 01:15 PM
 
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Quote:
Originally Posted by spyboy View Post

Wouldn't an AntiMode 8033 mostly eliminate the ringing problem?

The AntiMode has been shown to reduce ringing artifacts however it can't eliminate it completely (nothing can eliminate ringing unless you eliminate the room -- fat chance of that happening).

I've got bass traps from floor to ceiling in my living room space and the improvements made to tightness, articulation and attack is amazing. But it had NOTHING to do with cutting major peaks. At this point, I don't have any EQ whatsoever in my HT. But there is very little boom, notes stop and start almost on a dime.

If I had to measure my subwoofer in my room, I will bet that the response will be all over the place. No doubt bass absorption will help to flatten the response, but adding bass traps won't create a magically flat response. What it did for me was transform the quality of the bass.
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post #54 of 70 Old 04-08-2011, 01:24 PM
 
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then EQ'ing it flat with a very slow sweep can could help tame the boom sound, but then the sub will tend to sound anemic when short duration signals at the ringing frequency are presented.

You either address the source of the problem or you don't bother at all. That is my motto. What causes 'boom' ? The room. Moreover, standing waves at low frequencies. Only way you can effectively tackle this issue is to address the issue and that would be absorbing the reflections that cause the issue.

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Long standing question: Do effective passive bass traps even exist?

Yes.

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I thought you needed an active noise canceling sub (i.e. one with a built-in microphone) to dampen low frequency modes in a typical living room.

Huh ?
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post #55 of 70 Old 04-08-2011, 01:30 PM
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The AntiMode has been shown to reduce ringing artifacts however it can't eliminate it completely (nothing can eliminate ringing unless you eliminate the room -- fat chance of that happening).

I've got bass traps from floor to ceiling in my living room space and the improvements made to tightness, articulation and attack is amazing. But it had NOTHING to do with cutting major peaks. At this point, I don't have any EQ whatsoever in my HT. But there is very little boom, notes stop and start almost on a dime.

If I had to measure my subwoofer in my room, I will bet that the response will be all over the place. No doubt bass absorption will help to flatten the response, but adding bass traps won't create a magically flat response. What it did for me was transform the quality of the bass.

Like I said, the AntiMode can signficantly reduce ringing.

Room treatments are great but can't do what the AntiMode can do besides reducing ringing, specifically, flatten FR.
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Like I said, the AntiMode can signficantly reduce ringing.

That's great. But it can't reduce ringing in other locations. Nor can it reduce frequency response issues in other locations. Can it ?
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post #57 of 70 Old 04-08-2011, 02:39 PM
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That's great. But it can't reduce ringing in other locations. Nor can it reduce frequency response issues in other locations. Can it ?

Ok, since you want to be picky, their are other devices (on the market) that takes measurements from multiple locations.

Nothing against adding room treatments, but sophisticated EQ is on its way to becomming the norm.

Just ask Kal Rubinson.
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Yes, and these other devices.....do they actually work ? Do they actually reduce ringing in other locations ? If so, please show me evidence of this.

Sophisticated EQ or not, it will never replace acoustic treatment.
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post #59 of 70 Old 04-08-2011, 10:11 PM
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I thought you needed an active noise canceling sub (i.e. one with a built-in microphone) to dampen low frequency modes in a typical living room.


Huh ?

This is what I mean. http://www.bagend.com/bagend/downloads/ETrap.pdf

I've always heard (sic) that anechoic rooms are only anechoic down to a certain frequency. The larger the room, the lower in frequency it is truly anechoic. I don't know how some small (living room sized) bass traps can do what larger anechoic chambers can't do. What kind of improvements do you notice? Is it measurable?
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post #60 of 70 Old 04-09-2011, 01:24 AM
 
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I've always heard (sic) that anechoic rooms are only anechoic down to a certain frequency. The larger the room, the lower in frequency it is truly anechoic. I don't know how some small (living room sized) bass traps can do what larger anechoic chambers can't do. What kind of improvements do you notice? Is it measurable?

Of course it's measurable. We aren't talking about cable differences here. The kind of improvements I'm talking about do NOT extend to very low bass frequencies (50 Hz and below). The bass range is anywhere from 20 Hz-300 Hz. Most people neglect the upper bass (50-60 Hz and above) and this is where the majority of bass is recorded in most music.

I use broadband absorption to cover a wide range. The reason why my traps are effective are not just because of size but because of where they are placed. Covering corners in a room makes a big difference to absorption. For the bass, notes become less congested, less one-note, they become more articulate, precise and each note kicks in without overlapping the next, which is typically what happens in a conventional small room without any bass trapping. The room modes just swamp everything so its a giant mess.

Obviously, there is more to acoustic treatment than just adding bass traps, but I'm focusing on that because of the topic. I have floor to ceiling bass traps in both front corners. I plan to add the same for the rear but yes, it's measurable. Just look at anyone who has bought bass traps, have a look at their waterfall graph. You'll see a reduction in ringing over the bass range. The effectiveness of that trap will depend on thickness and placement.

I'm surprised you are asking these questions because acoustic treatment has been around for decades and it's effectiveness has never been questioned. But by far, the room is the determining factor. If a room has modal resonances that affect a wide range then it doesn't matter what sub you own, it will be affected.
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