Why does my system sound so much better with a low xover?

[yepimonfire]

Do you have the ability to measure impulse response?

I would bet this is time smear.

As you all know I regard subs as an evil you have to live with because of the falling low end response of most speakers.

The more you space speakers and subs the greater the smear. Sure you can time them for one location. However the time path will vary as you move listening location.

I can tell you that in a sub system there is easily seen separation of the impulse responses. Not good. Whilst moving subs may help with room resonances, it creates time smear. In my view in good low Q systems this time smear is easily audible, as I think you have found out.

As you know I have pointed at that there is a chasm in the view of the use of subs between the UK and USA.

The UK view is to set speakers to full range wherever possible and NOT cross them over. Just use the subs to gently supplement the roll off of the speakers.

My ears and measurements tell me the UK position is correct. And you know what, you don't then need gobs of power for your subs. In a well balances system they take little power.

I'm firmly and unashamedly in the UK camp on this and not the US.

And finally people who say time smear is not audible are just flat out wrong.

Yep, I think you have just found that it is.

Humans have much better perception of temporal differences than frequency difference, it’s been shown that we can perceive as little as a 6ms difference, personally I find a temporally inaccurate system more objectionable than a linearly inaccurate system. I have always found that full range speakers sound better than sub sat systems, Ideally I’d have RP-280ms for all 5 floor speakers, considering they have an f3 of 34hz, a sub would only be necessary for LFE, since the main channels in movies are mixed with full range cinema systems (f3 of ~40hz) in mind, there would be very little content below this point. I just don’t have the funds for that unfortunately.

What I don’t understand is why it disappears at lower crossover points. It sounds fine crossed over at 60hz or below, and this has actually been a near universal experience with different speakers and subs in different rooms.

Also, why would not using a crossover at all make a difference? I haven’t tried it this way, because I don’t see any point in wasting power and increasing IM distortion by sending content below the tuning frequency to my speakers.


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[TLS Guy]

Humans have much better perception of temporal differences than frequency difference, it’s been shown that we can perceive as little as a 6ms difference, personally I find a temporally inaccurate system more objectionable than a linearly inaccurate system. I have always found that full range speakers sound better than sub sat systems, Ideally I’d have RP-280ms for all 5 floor speakers, considering they have an f3 of 34hz, a sub would only be necessary for LFE, since the main channels in movies are mixed with full range cinema systems (f3 of ~40hz) in mind, there would be very little content below this point. I just don’t have the funds for that unfortunately.

What I don’t understand is why it disappears at lower crossover points. It sounds fine crossed over at 60hz or below, and this has actually been a near universal experience with different speakers and subs in different rooms.

Also, why would not using a crossover at all make a difference? I haven’t tried it this way, because I don’t see any point in wasting power and increasing IM distortion by sending content below the tuning frequency to my speakers.


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Well we are in controversial territory here. I believe timing matters and can not be shrugged off.

Now as I have often pointed out time and phase difference are the same thing. However it is much better to think in terms of time rather than phase.

Lets take two sounds that are 360 degrees in phase apart. Loose talkers say that the sounds are in phase, and look like it on a response graph. However they are actually 360 degrees out of phase. If you use time instead of phase in your thinking, the error is immediately apparent, as the sounds a one whole wavelength in time apart. This way of looking at it points out the error and the trespass created right away.

So if you run your mains full range there should not be a timing error on that end. Now the sub filter will be fourth order and so there will be a 180 degree phase lag, which in time is half wave length late.

Now if we use the crossover on both mains and sub the mains have a second order crossover, and so lead by 90 degrees, which is one quarter of a wavelength in time. So the mains lead the sub by 3/4 of a wavelength in time. Now the sub phasing knob does not correct time. If it were labelled in time and not phase, the faulty thinking would be revealed.

Take a look at the impulse of my lower level system and you can see the time difference of the subs and mains. This is a two channel system. The main speakers are run full range.

Here is a frequency plot and impulse response at one of the listening position and you can see the time smear. The time smear is mainly due to the time path. The electrical phase lag of the woofers is only 1/3 of a wavelength in time.

Here is the impulse response of the studio system which is an integrated full range speaker system designed with an eye to minimal time smear.

On your last point I suspect the reason is that your mains are probably starting to roll off and below 50 Hz you are getting into the low sensitivity area of human perception.

Some would say this does not matter, but I'm certain it does. From recent comments of experienced engineers here, I'm certain does.

 

[yepimonfire]

Couldn’t this be corrected via modification to the distance setting in the avr? Is there a way to measure the timing lag and compensate for it or can it be done by ear? Currently the sub is set to the literal distance from the mlp.


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[TLS Guy]

Couldn’t this be corrected via modification to the distance setting in the avr? Is there a way to measure the timing lag and compensate for it or can it be done by ear? Currently the sub is set to the literal distance from the mlp.


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This will only work if the speakers and sub are in proximity. Once you part them, you can only set for one listening position. The time paths will be different for other locations. One of my aims is not to have sweet spots and a uniform sound throughout the room.

That is why I favor integrated solutions.

It is bad enough the crossovers and multi way speakers separate fundamentals from harmonics. Separating them by spacial location just adds insult to injury. Minimizing this mayhem is just one of the toughest problems of design.

I know I go against prevailing wisdom. To read current practice you would think the sub was the most important part of the system. In fact it is probably the least important and most dispensable item. When I hear most systems the subs are doing more harm than good. If subs are to be used, then they need to be used with great subtlety. They tend to do more damage to accurate reproduction than almost any other item.

 

[shadyJ]

There are a lot of comments made here that I don't see having a real scientific footing. TLSguy is right about controversial.

There isn't much meaning in the statement that humans have better perception of temporal differences than frequency differences. Frequency is a function of time anyway. There have been a lot of studies on temporal discrimination, but they don't at all support assertions made for audibility of phase distortion. The studies done of the audibility of phase distortion demonstrate that it is very difficult to hear. You basically have to be wearing headphones and be fed very particular signals in order to sense phase distortion.

Also, impulse response is a reflection of frequency response and has a direct relationship, but you don't hear an impulse response, you hear frequency response. There is not much point in gauging the accuracy of a system by pointing to an impulse response measurement, especially when a frequency response measurement is available. You don't need to have the subwoofer be in the same place as the speakers to get a quick decay in an impulse response measurement, all you need is a flat frequency response, or better yet, a response with lots of treble proportionate to bass output. That will really get you a 'quick' impulse response, and it will sound terrible. And what does 'time smearing' mean in a typical end user's room with respect to loudspeaker systems? If you don't want to hear 'time smearing', you will have to listen to your music in an anechoic chamber.

I am sorry guys, but dismissing the importance of frequency response in favor of some vague, unsupported ideas about phase and timing flies in the face of both audiology and acoustics.

 

[yepimonfire]

This will only work if the speakers and sub are in proximity. Once you part them, you can only set for one listening position. The time paths will be different for other locations. One of my aims is not to have sweet spots and a uniform sound throughout the room.

That is why I favor integrated solutions.

It is bad enough the crossovers and multi way speakers separate fundamentals from harmonics. Separating them by spacial location just adds insult to injury. Minimizing this mayhem is just one of the toughest problems of design.

I know I go against prevailing wisdom. To read current practice you would think the sub was the most important part of the system. In fact it is probably the least important and most dispensable item. When I hear most systems the subs are doing more harm than good. If subs are to be used, then they need to be used with great subtlety. They tend to do more damage to accurate reproduction than almost any other item.

That’s exactly my goal as well, it’s one of the reasons I chose the speakers I have, because the sweet spot is very wide, it’s also why I’m a big fan of matrix up mixing on two channel music, which maintains the integrity of the stereo image regardless of seating.

How would using separate subs for each channel, place directly beneath each speaker affect the timing smear?


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[yepimonfire]

There are a lot of comments made here that I don't see having a real scientific footing. TLSguy is right about controversial.

There isn't much meaning in the statement that humans have better perception of temporal differences than frequency differences. Frequency is a function of time anyway. There have been a lot of studies on temporal discrimination, but they don't at all support assertions made for audibility of phase distortion. The studies done of the audibility of phase distortion demonstrate that it is very difficult to hear. You basically have to be wearing headphones and be fed very particular signals in order to sense phase distortion.

Also, impulse response is a reflection of frequency response and has a direct relationship, but you don't hear an impulse response, you hear frequency response. There is not much point in gauging the accuracy of a system by pointing to an impulse response measurement, especially when a frequency response measurement is available. You don't need to have the subwoofer be in the same place as the speakers to get a quick decay in an impulse response measurement, all you need is a flat frequency response, or better yet, a response with lots of treble proportionate to bass output. That will really get you a 'quick' impulse response, and it will sound terrible. And what does 'time smearing' mean in a typical end user's room with respect to loudspeaker systems? If you don't want to hear 'time smearing', you will have to listen to your music in an anechoic chamber.

I am sorry guys, but dismissing the importance of frequency response in favor of some vague, unsupported ideas about phase and timing flies in the face of both audiology and acoustics.

Humans can’t detect absolute phase, for example, many crossover designs have the tweeters wired out of phase to correct the phase problems in relation to the woofer, and the inversion of 5khz in relation to say, 500hz isn’t audible, but relative phase is certainly audible. If we couldn’t reliably hear small differences in phase, multichannel audio would be pointless.

Here’s an experiment you can do, go into the distance setting of your avr and increase the distance of your right speaker by 6 feet, this will give a delay of approximately 6ms, now play some music in stereo, I guarantee the entire image will be shifted to the left of the soundstage. Now do the same with your sub set the xover to 50hz, play some music with good drum lines, again, I guarantee the kick drum relative to the cymbals, snare, and toms will sound out of time with the rest of the music.

If the frequencies which are delayed are in a different band, it’s not going to distort the frequency response.

As for reflections, the brain can separate reflected sounds spaced far apart as reflections and not the original source, toole is of the opinion that early reflections, which aren’t perceived as separate reflections, are good for the sound stage and enhance the imaging, this has never been my experience, usually I find the only thing it does is smear the soundstage and ruin imaging. I’ve had both untreated rooms and rooms with treatment at first reflection points, and I much prefer the treated room to the untreated.


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[shadyJ]

A phase mismatch between channels is not what is under discussion, nor is head related transfer functions. We are talking about the audibility of phase distortion in loudspeaker systems. And there is no chance that you can hear a delay of 6 ms on stuff at 50 Hz and under. A single cycle of 50 Hz alone lasts for 20 ms.

 

[TLS Guy]

A phase mismatch between channels is not what is under discussion, nor is head related transfer functions. We are talking about the audibility of phase distortion in loudspeaker systems. And there is no chance that you can hear a delay of 6 ms on stuff at 50 Hz and under. A single cycle of 50 Hz alone lasts for 20 ms.

Nor is the importance of a flat frequency response denied. However a frequency response alone can not possibly tell the whole story. As I say, you can make two sine waves look great and phase them up for the recording device. However you have no idea of the actual timing between the two. The two origins could be minutes apart but you would never know.

The point Ted Jordan was always making is that these time shifts between the fundamental and harmonics created by loudspeakers is audible. The fact that we are always concerned about the square wave of an amp, but give speakers a pass is telling. As you know very few speakers can produce even a passable square wave. The greater the phase/time shift the worse it looks. If the time shift is a whole cycle, which it is with a fourth order electrical crossover, the square wave becomes pretty much a perfect sine wave when recorded from the speaker.

Now this is so hard to evaluate, as changing the crossover order, does more than just change timing. So the best you can do is have two different speakers with different crossover orders.

I do think though that designs with high electrical crossover orders, make the speaker "slugged" with loss of impact compared to a good one with less time shift between drivers.

 

[everettT]

I love threads that are titled with a question and when answers are provided, OPs proceed to explain why responding posters are wrong.

 

[TheWarrior]

Loudspeakers are minimum phase devices. For our purposes, that means if your ears are out of phase with a certain frequency, you will not hear it. The offending frequency will measure as a dip. Obviously this applies to frequencies below transition as higher frequencies have increasingly smaller wavelengths.

As for reflections, the brain can separate reflected sounds spaced far apart as reflections and not the original source, toole is of the opinion that early reflections, which aren’t perceived as separate reflections, are good for the sound stage and enhance the imaging, this has never been my experience, usually I find the only thing it does is smear the soundstage and ruin imaging. I’ve had both untreated rooms and rooms with treatment at first reflection points, and I much prefer the treated room to the untreated.

Toole does not have opinions on the audibility of reflected sounds. He's a research scientist. It either is, and is repeatable, or it is not.

Hundreds of double blind tests are why he states 'Listener's prefer first reflections from side walls.' They increase Listener Envelopment and Apparent Source Width.

I know in the other threads you've mentioned a 11x12 room. Is this the room you're referring to, and that houses your Klipsch speakers? I would assume the LP is not located at the end of one of those walls, so listening to Horn loaded speakers (that limit propagation loss over distance) would not be the recommended speaker to use if you're only listening from 6'-8' away. I could very easily see why you feel first reflections should be absorbed, the treble must be excruciating.

 

[yepimonfire]

Loudspeakers are minimum phase devices. For our purposes, that means if your ears are out of phase with a certain frequency, you will not hear it. The offending frequency will measure as a dip. Obviously this applies to frequencies below transition as higher frequencies have increasingly smaller wavelengths.



Toole does not have opinions on the audibility of reflected sounds. He's a research scientist. It either is, and is repeatable, or it is not.

Hundreds of double blind tests are why he states 'Listener's prefer first reflections from side walls.' They increase Listener Envelopment and Apparent Source Width.

I know in the other threads you've mentioned a 11x12 room. Is this the room you're referring to, and that houses your Klipsch speakers? I would assume the LP is not located at the end of one of those walls, so listening to Horn loaded speakers (that limit propagation loss over distance) would not be the recommended speaker to use if you're only listening from 6'-8' away. I could very easily see why you feel first reflections should be absorbed, the treble must be excruciating.

No, my main system is in a 20x12 room at 3m seating distance.

I can only tell you that I have always had trouble getting well defined imaging without reducing first reflections, in three different rooms of different sizes over the years. I’m not saying they should be completely deadened, just attenuated.


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[TheWarrior]

No, my main system is in a 20x12 room at 3m seating distance.

I can only tell you that I have always had trouble getting well defined imaging without reducing first reflections, in three different rooms of different sizes over the years. I’m not saying they should be completely deadened, just attenuated.


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Cool! To explore that further you'd have to get specific on set up and placement, but your preferences are your preferences.

In that other thread tho, with the 11x12 room, I think there are real solutions that can be found there if you are willing and able to get very comprehensive in your details and provide all the necessary info I mentioned.

Pretty sure you're in GA too. I'm slowly working on KEW's setup right now to help his rather complex situation. We both have living room setups that are open to other rooms, but his goes a step further by have the second floor partially over hung in to the living room and is completely open.

Perhaps some time I can come check your system(s) out and offer any assistance, if you like.

 

[TLS Guy]

No, my main system is in a 20x12 room at 3m seating distance.

I can only tell you that I have always had trouble getting well defined imaging without reducing first reflections, in three different rooms of different sizes over the years. I’m not saying they should be completely deadened, just attenuated.


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May be you want unrealistic imaging. In a concert hall the imaging is not precise. It is mainly visual cues.

Over precise imaging is actually a detriment to realistic reproduction. The real deal is how the speaker imparts a sense of space and really seems to open up the room, so you are hearing the original acoustic space to a high degree.

Good systems will impart the original space to quite a high degree with a good recording.

Anyhow, I'm off to WMSTR now. This year it features Emerson-Brantingham.

 

[KEW]

Hundreds of double blind tests are why he states 'Listener's prefer first reflections from side walls.' They increase Listener Envelopment and Apparent Source Width.

Are there any good guidelines for how close those sidewalls should be.
Intuitively (which is a step below assumptions), it seems like if the wall is very close, we might perceive it as smearing of the primary signal. Adding distance would cause a greater delay in the reflection which, it seems, we would be more likely to process as a reflection (or ambiance?) for the direct sound.

 

[TheWarrior]

Are there any good guidelines for how close those sidewalls should be.
Intuitively (which is a step below assumptions), it seems like if the wall is very close, we might perceive it as smearing of the primary signal. Adding distance would cause a greater delay in the reflection which, it seems, we would be more likely to process as a reflection (or ambiance?) for the direct sound.

There's too many variables to prescribe any set procedures. A speaker will sound lousy if it's too close to a wall, there could be port noise, boomy bass, or the walls, or furniture close by could resonate. Conversely, the mid range is affected when a speaker is too far from the rear wall thanks to cancellations of the wavelengths that match the distance between the wall and speaker. The sound bounces off and recombines out of phase, canceling the sound out.