Some speakers slant, some don't. Why?

[audiventory]

1 hour ago, Jud said:

 

Yes, no way I'd try this by ear.  You should ask Keith, I think, because I have no experience using digital crossovers.  I'm sure you can *tune* digital crossovers using mics, but I don't know if there are crossovers that auto tune by microphone (I understand this to mean the crossover would tune itself using a connected mic).

 

I also wonder (Keith?) whether the tuning that one can do oneself extends not only to frequency but to measurements of group delay and phase.

 

I think digital digital crossover may be tuned in system with room correction.

[audiventory]

36 minutes ago, firedog said:

I just  remembered that the KEFLS50  actives have, in addition to UniQ alignment of drivers, has an option for additional  DSP time alignment, in order to improve the time alignment.

 

Theoretically, active speakers are better way, because amp tuned by drivers, crossover too.

 

It is traditional scheme for studio monitors. That should provide (theoretically again) flat response.

[Jud]

14 minutes ago, audiventory said:

 

I think digital digital crossover may be tuned in system with room correction.

 

9 minutes ago, audiventory said:

 

Theoretically, active speakers are better way, because amp tuned by drivers, crossover too.

 

It is traditional scheme for studio monitors. That should provide (theoretically again) flat response.

 

Although studio monitors are not necessarily famous for great sound.

 

As you said, implementation is critical.  A lot of what I have read about room correction software packages involves frequency response, and it is my impression the filters used are very often minimum phase.  (I do see time correction mentioned in the Legacy and KEF materials, so perhaps digital crossovers pay more attention to this than most room correction software that doesn't come from speaker manufacturers.)

[Keith_W]

5 hours ago, Jud said:

 

Yes, no way I'd try this by ear.  You should ask Keith, I think, because I have no experience using digital crossovers.  I'm sure you can *tune* digital crossovers using mics, but I don't know if there are crossovers that auto tune by microphone (I understand this to mean the crossover would tune itself using a connected mic).

 

I also wonder (Keith?) whether the tuning that one can do oneself extends not only to frequency but to measurements of group delay and phase.

 

Hi Jud, as I understand it the first question pertains to whether there is such a thing as an "auto-tuning" DSP? As far as I know, there is no such thing as a crossover that can tune itself with DSP. With all products I have tried, you MUST start by inputting the desired crossover configuration - crossover point, crossover order, and configuration (Butterworth, Linkwitz-Riley, etc), symmetric vs. asymmetric, etc. To even know these things, you need to have an understanding of the Thiele-Small parameters of your drivers, your enclosure, etc. 

 

There are DSP products which are able to do room correction of the entire corrected speaker at the push of a button. Lyngdorf/Tact, and a few companies. Including one company with a fancy looking microphone that looked like an alien villain's anal probe whose name I forget. 

 

The DSP that you do yourself can do nearly everything if you have software which is powerful enough, sufficient processing power, and enough brains to interpret your results. I have plenty of the above with the exception of the latter. Correcting group delay and phase is considered bread and butter for crossover DSP software. At the very minimum, they should be able to do it. However, how much correction can be applied depends on how much processing power you have. 

 

Just an example of what DSP can do. You may have heard of a double bass array. The idea is that your front wall has four subwoofers panel mounted (i.e. infinite baffle) at locations precisely defined by some equations. The bass frequency will emerge almost as a flat plane (rather than a point source) and sweep across the room until it encounters the back wall. The back wall has another array of similar subwoofers, only that the back wall has been controlled by DSP to cancel reflections from the incoming front bass wave. 

 

You can even do a "virtual" double bass array with DSP. Rather than have an array of subwoofers in the back wall, you can set your front subwoofers to produce the cancelling frequency at the same time it is producing the audible frequency. CA member akcheng has described exactly this method in his blog. 

 

There are still quite a lot of things that DSP can not do. It can not control speaker directivity or off-axis response. It can not force drivers to do what they don't want to do. 

BTW I hope that you don't think I am some kind of DSP guru, because I am not. It just seems as if CA's real DSP gurus don't seem to be around very much these days, which is a bit sad considering the whole reason I joined CA in the first place was to learn from them. 

[Jud]

25 minutes ago, Keith_W said:

BTW I hope that you don't think I am some kind of DSP guru, because I am not. It just seems as if CA's real DSP gurus don't seem to be around very much these days, which is a bit sad considering the whole reason I joined CA in the first place was to learn from them. 

 

@The Computer Audiophile, maybe not a bad idea for an article, or a series of them?  Use of room equalization software to guide physical layout of listening room and system placement, and use as the basis for DSP; then how to do the DSP steps....

[The Computer Audiophile]

5 minutes ago, Jud said:

 

@The Computer Audiophile, maybe not a bad idea for an article, or a series of them?  Use of room equalization software to guide physical layout of listening room and system placement, and use as the basis for DSP; then how to do the DSP steps....

 

Yes, @mitchco literally wrote the book! If he had more time to write DSP articles I'd happily publish every one. 

 

I reached out to @Miska about an article on upsampling and I really hope he has the time. 

[esldude]

 

The squarewave from the Vandy isn't too bad.  Not as good as some Quads. Still quite good for a multi-way speaker.

 

 

 

Impulse response of the Vandy 2ce.

 

 

 

And for comparison the Quad Esl 63.

 

 

Of course in regards to super precise alignment, I do believe a 20% change in humidity will change points of focus due to change in the speed of sound more than 1/8th of an inch.   And a 2 degree change in temperature will make more difference than the humidity. 

 

[Jud]

37 minutes ago, esldude said:

 

The squarewave from the Vandy isn't too bad.  Not as good as some Quads. Still quite good for a multi-way speaker.

 

 

 

Impulse response of the Vandy 2ce.

 

 

 

And for comparison the Quad Esl 63.

 

 

Of course in regards to super precise alignment, I do believe a 20% change in humidity will change points of focus due to change in the speed of sound more than 1/8th of an inch.   And a 2 degree change in temperature will make more difference than the humidity. 

 

 

Strange to me the Vandy would stop ringing quicker than the Quad.

 

I think an 1/8 inch movement by the listener may happen more often than 20% humidity changes or even 2 degree temperature changes.

 

Have any graphs for the Sound Labs or upline Vandys with built in amps?

[esldude]

4 minutes ago, Jud said:

 

Strange to me the Vandy would stop ringing quicker than the Quad.

 

I think an 1/8 inch movement by the listener may happen more often than 20% humidity changes or even 2 degree temperature changes.

 

Have any graphs for the Sound Labs or upline Vandys with built in amps?

Those were all from stereophile measurements, which I should have credited.  The old software would do that for links from Stereophile automatically.  They don't do impulse or squarewave more recently.  The Treo does show a nice step response which is near textbook.

 

Of course how important is that?  Here is the step response of some Revel Ultima Salon 2 speakers which sound quite fantastic by most accounts.  This step response is similar to that of all the Revel speakers.  Most of which get near universal acclaim for sounding good.

 

I believe the ESL63 had a resonance between the panel and metal cover around 13 khz which is why it rings on.  The later near identical design of the 989 did reduce that problem. 

[semente]

This is from Siegfried Linkwitz's website:

 

Design of Loudspeakers

Some general observations

 

The typical loudspeaker product is designed to make money and not necessarily to provide accurate sound reproduction.

Since customers prefer small, unobtrusive speakers and judge sound quality by the amount of bass that they hear and by high frequencies they had not noticed before, there is a staggering number of essentially identical designs on the market that meet these requirements at different price points.

No wonder then that there is a generic loudspeaker sound and that you can always tell whether something that you hear originates from a speaker and not from a live source.

The marketing departments of the different speaker manufacturers are busy to point out differentiating features and breakthrough inventions when it comes to the highest price points, but in reality box loudspeaker design has come to a the end of a road and all you will hear are slight variations on the same theme.

The fundamental problems of box re-radiation and non-uniform power response in a room are at best only partially solved by these conventional designs

 

Sound reproduction is about creating an auditory illusion.

When the recorded sound is of real instruments or voices there is a familiar, live reference in our auditory memory. The illusion of hearing a realistic reproduction is destroyed by distortion that is added anywhere in the signal chain from microphone to loudspeaker, but the speaker is by far the biggest culprit.

Every designer focuses on the on-axis frequency response as if it were the all determining distortion parameter.

Sometimes great attention is paid to the phase response in an attempt to preserve waveform fidelity, which at best can only be achieved for a single listening point in space.

Ignored usually, though of much greater importance, is resonance in drivers and cabinets and the slow release of stored energy that goes with it. 

Furthermore, the uniformity and flatness of the off-axis frequency response which we hear via room reverberation and reflections is rarely a design goal.

You can check the naturalness of the timbre by listening from another room.

Does it sound like a loudspeaker is playing?

The imbalance in the speaker's power response between low and high frequencies destroys the illusion.

 

And then there are the non-linear distortions, the ones that add sounds that were not present in the original.

They are easily measurable in the form of harmonic and intermodulation distortion products.

Rarely do non-linear distortion considerations enter into the design of speakers.

Otherwise, consumer stores and recording studios would not abound with 2-way designs - usually a 6.5" woofer/midrange and 1" dome tweeter in a ported box - that are physically incapable of the sound levels claimed for them and which by distortion often create a unique box loudspeaker bass experience, variously described with slam and speed.

Some design attempts for reducing non-linear distortion lead to line source speakers.

While successful at this they introduce phantom image distortions and, coupled with a conventional vented woofer of sorts, they suffer the same uneven power response and rich excitation of room resonances as the typical box speaker design.

 

(...)

 

http://www.linkwitzlab.com/design_of_loudspeakers.htm

 

 

 

[Nikhil]

On 3/24/2017 at 3:49 AM, coot said:

Floor-standing speaker designs are all over the place. I know the slanty ones are designed so for the purpose of time alignment. One question is, if time alignment is super important, why are there so many designed with flat fronts, apparently ignoring TA?

 

Also, can TA be corrected in the digital domain as part of DSP?

 

18 hours ago, coot said:

Wow. You guys are way over my head with your tech-talk - (maybe I should listen from above my head?).

So I guess if I'm looking to buy I should look for speakers that are either slanty or have digital crossovers and some mention of digital time-delay correction?

 

Coot,

 

This is a very complex subject.  A Google search for "Sloped Baffles" will bring up an Audiogon discussion in which Roy Johnson of Green Mountain Audio contributed some great material on Time Alignment.  I know because that discussion was one of the reasons I picked up the speakers I use right now. 

 

https://forum.audiogon.com/discussions/sloped-baffle

 

Look up CA articles by Mitch to find a detailed explanation on how you can use DSP to time align your drivers using Acourate
It needs a fair amount of effort and understanding of the Acourate software,  IMO it's something that needs to be left to the pros..

.

https://www.computeraudiophile.com/index.php?app=cms&module=pages&controller=page&path=ca/ca-academy/Advanced-Acourate-Digital-XO-Time-Alignment-Driver-Linearization-Walkthrough

 

The way I know best for regular folks like us to have access to this is with speakers which allow for the Tweeter to be moved in line with the woofer.  The tuning is done with vocals and the drivers lined up in the front at first.   Then with you in the listening seat have someone move the tweeter back a few inches until the vocals appear to come from the center of the woofer(s).  At this tweeter position the drivers are aligned and the sound locks in.  You do this with one channel first and then the other.

 

Apart from GMA EOS speakers the Ascendo System Series speakers also offer this feature,

This is a fantastic subject on which I have spent a fair amount of time.  Explore it and there is no turning back once you experience it.

 

 

[semente]

8 hours ago, esldude said:

Those were all from stereophile measurements, which I should have credited.  The old software would do that for links from Stereophile automatically.  They don't do impulse or squarewave more recently.  The Treo does show a nice step response which is near textbook.

 

Of course how important is that?  Here is the step response of some Revel Ultima Salon 2 speakers which sound quite fantastic by most accounts.  This step response is similar to that of all the Revel speakers.  Most of which get near universal acclaim for sounding good.

 

I believe the ESL63 had a resonance between the panel and metal cover around 13 khz which is why it rings on.  The later near identical design of the 989 did reduce that problem. 

 

Two (negative) aspects one should mention are the significant driver overlap and the ineffective control of the mid/mid-woofer resonance (plots from Sphile's measurements of the 2CeSigII):

 

 

The 2CeSigII also has a very bright in-room tonal balance, compared here to the PSB Synchrony One (which measures very flat in anechoic conditions) at JA's - bottom graph, though tis may or may not be related with the crossover design...

 

 

 

 

 

The Revel Ultima Salon2s also measure very flat in anechoic and in-room at JA's (blue):

 

 

[Jud]

9 hours ago, esldude said:

Those were all from stereophile measurements, which I should have credited.  The old software would do that for links from Stereophile automatically.  They don't do impulse or squarewave more recently.  The Treo does show a nice step response which is near textbook.

 

Of course how important is that?  Here is the step response of some Revel Ultima Salon 2 speakers which sound quite fantastic by most accounts.  This step response is similar to that of all the Revel speakers.  Most of which get near universal acclaim for sounding good.

 

I believe the ESL63 had a resonance between the panel and metal cover around 13 khz which is why it rings on.  The later near identical design of the 989 did reduce that problem. 

 

Thanks, esldude, informative as always.

 

Wish I knew how to read the "waterfall plots" that are so popular these days.

[esldude]

8 hours ago, semente said:

 

Two (negative) aspects one should mention are the significant driver overlap and the ineffective control of the mid/mid-woofer resonance (plots from Sphile's measurements of the 2CeSigII):

 

 

The 2CeSigII also has a very bright in-room tonal balance, compared here to the PSB Synchrony One (which measures very flat in anechoic conditions) at JA's - bottom graph, though tis may or may not be related with the crossover design...

 

 

 

 

 

The Revel Ultima Salon2s also measure very flat in anechoic and in-room at JA's (blue):

 

 

Yes, the issues you point out are a result mainly of the choice to use 1st order crossovers in the Vandersteen.   The PSB uses steeper crossovers.  The step response is much like the Revel.  They use similar design philosophies.  Steep crossovers for optimum frequency response combined with even controlled off axis dispersion.  JA described the step response for the PSB and Revel with the same phrases:

Turning to the time domain, the PSB's step response is shown in fig.9. All the drive-units are connected with positive acoustic polarity, each one's step smoothly handing over to that of the next lower in frequency. This correlates with the excellent frequency-domain integration of their outputs noted earlier.
Read more at http://www.stereophile.com/content/psb-synchrony-one-loudspeaker-measurements#5hYgekL4FT23wPPe.99

 

 

JA's description of the Vandy 2CE:

In the time domain, despite the Vandersteen's multiway design, its impulse response (fig.7) is as time-coherent as that of the single-driver, crossoverless Fujitsu Ten Eclipse TD712z, reviewed elsewhere in this issue.
Read more at http://www.stereophile.com/content/vandersteen-2ce-signature-ii-loudspeaker-measurements#0eG5hLm0CRCwkWxG.99

 

The step response (fig.8) also features a time-coherent, right-triangle shape, though there is a rather faster decay than I expected.
Read more at http://www.stereophile.com/content/vandersteen-2ce-signature-ii-loudspeaker-measurements#0eG5hLm0CRCwkWxG.99

 

So one philosophy is to have very even responses, controlled off axis dispersion, and steep crossovers to control the drivers well with a step response that isn't time coherent.  The other is to allow wide driver overlap, and have time coherent response at least at some points in front of the speaker. This usually results in an uneven off axis response particularly above and below the listening axis. 

 

Both have their fans and adherents.  I've heard both sound good.

 

I would say I think the PSB/Revel/JBL approach seems to produce speakers which sound good easier with less fuss in more rooms.  Which one ultimately sounds best comes down to details of execution.  What information there is indicates our hearing in the upper frequencies at least is not fussy at all about phase or time coherence.  That leads me to think letting that go makes it much easier to produce a satisfying speaker.

[Ralf11]

7 hours ago, Jud said:

...

how to read the "waterfall plots"...

 

Jud, look at the foothills are the foot of the mountains - some stick out a lot more than others, indicating a room mode resonance that should be treated

 

may also be from the speaker itself, but I don't think you will find much of that mechanism on a Vandersteen

[esldude]

7 hours ago, Jud said:

 

Thanks, esldude, informative as always.

 

Wish I knew how to read the "waterfall plots" that are so popular these days.

Here is a real simple explanation.

 

http://redspade-audio.blogspot.com/2011/05/rew-understanding-decay-and-waterfall.html

 

This one goes into more detail.

 

https://www.roomeqwizard.com/help/help_en-GB/html/graph_waterfall.html

[audiventory]

Waterfal allow estimate signal spectrum in dynamics.

I prefer waterfall plot in 2-D projection (time-frequency-amplitude(brightness)). It allow exactly measure point what you need. 3-D picture look nice for presentations and analyzis of first stage. But it is too complex for detailed analyzis, in my opinion.

[semente]

13 hours ago, Ralf11 said:

 

Jud, look at the foothills are the foot of the mountains - some stick out a lot more than others, indicating a room mode resonance that should be treated

 

may also be from the speaker itself, but I don't think you will find much of that mechanism on a Vandersteen

 

The waterfall can be used for different purposes such as determining room resonances or if the speaker is measured in free space (or nearfield with a narrow time-window) speaker resonances.

 

Speaker resonances, or better yet driver resonances are what we should be looking for in Sphile's measurements.

 

Here is a good example where you can perfectly identify the breakup resonances produced by the aluminium cone (blue, -5dB @ 5.8kHz) and dome (red, 20dB @ 25kHz) of a 2-way Monitor Audio loudspeaker with a :

 

Here you can see how it affects the frequency response.

The woofer appears to be low-passed using a first-order, 6dB/octave filter.

 

Monitor Audio Studio 15, cumulative spectral-decay plot of woofer at 44" (0.15ms risetime).

 

Monitor Audio Studio 15, cumulative spectral-decay plot at 44" (0.15ms risetime).

 

Monitor Audio Studio 15, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the center of the cabinet's sidewall (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

 

Read more at http://www.stereophile.com/content/monitor-audio-studio-15-loudspeaker-measurements

[semente]

Here's another example, BnW's 683 S2, this time a kevlar midrange cone breaking up at 3.6kHz:

 

B&W 683 S2, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

 

B&W 683 S2, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield responses plotted below 300Hz

Read more at http://www.stereophile.com/content/bowers-wilkins-683-s2-loudspeaker-measurements

[semente]

Here's another way to measure decay (lower colour temperature equals lower sound level, signal output at top horizontal side of the plot, time extends from top to bottom, frequency increases from left to right):

 

 

Graham Audio LS5/9

http://www.hi-fiworld.co.uk/index.php/loudspeakers/65-reviews/726-graham-audio-bbc-ls59.html

[semente]

4 hours ago, semente said:

Here's another way to measure decay (lower colour temperature equals lower sound level, signal output at top horizontal side of the plot, time extends from top to bottom, frequency increases from left to right):

 

It's actually not another way to measure but to display.

[Ralf11]

True - somebody post up a plot for a bad speaker...

[Jud]

23 hours ago, esldude said:

Yes, the issues you point out are a result mainly of the choice to use 1st order crossovers in the Vandersteen.  

* * *

JA's description of the Vandy 2CE:

In the time domain, despite the Vandersteen's multiway design, its impulse response (fig.7) is as time-coherent as that of the single-driver, crossoverless Fujitsu Ten Eclipse TD712z, reviewed elsewhere in this issue.
Read more at http://www.stereophile.com/content/vandersteen-2ce-signature-ii-loudspeaker-measurements#0eG5hLm0CRCwkWxG.99

 

The step response (fig.8) also features a time-coherent, right-triangle shape, though there is a rather faster decay than I expected.
Read more at http://www.stereophile.com/content/vandersteen-2ce-signature-ii-loudspeaker-measurements#0eG5hLm0CRCwkWxG.99

 

So one philosophy is to have very even responses, controlled off axis dispersion, and steep crossovers to control the drivers well with a step response that isn't time coherent.  The other is to allow wide driver overlap, and have time coherent response at least at some points in front of the speaker. This usually results in an uneven off axis response particularly above and below the listening axis. 

 

Both have their fans and adherents.  I've heard both sound good.

 

I would say I think the PSB/Revel/JBL approach seems to produce speakers which sound good easier with less fuss in more rooms.  Which one ultimately sounds best comes down to details of execution.  What information there is indicates our hearing in the upper frequencies at least is not fussy at all about phase or time coherence.  That leads me to think letting that go makes it much easier to produce a satisfying speaker.

 

Richard Vandersteen's interview indicates a deliberate decision to achieve time/phase coherence at the cost of flatter frequency response across the band.

 

Ricardo has mentioned before this bothers him.  It didn't bother me with the 2Ci and 2Ce, and assuming the 3A Sig is similar, there either.  One way to look at it is that I learned to hear this sound signature as "correct," or at least what I was looking for in audio reproduction.  Another viewpoint is that since people do hear differently, perhaps I was among a sub-population predisposed to pay greater attention to time/phase coherence in evaluating the realism of reproduced sound.

[semente]

14 minutes ago, Jud said:

 

Richard Vandersteen's interview indicates a deliberate decision to achieve time/phase coherence at the cost of flatter frequency response across the band.

 

Ricardo has mentioned before this bothers him.  It didn't bother me with the 2Ci and 2Ce, and assuming the 3A Sig is similar, there either.  One way to look at it is that I learned to hear this sound signature as "correct," or at least what I was looking for in audio reproduction.  Another viewpoint is that since people do hear differently, perhaps I was among a sub-population predisposed to pay greater attention to time/phase coherence in evaluating the realism of reproduced sound.

 

I also find this a plausible explanation and one's favourite musical genres also play a part here.

 

Sphile's 3A measurements show a more even tonal-balance although the upper mids and treble are shelved up by a few dB, maybe the 3A Sig is even better in this respect.

There seems to be quite a bit of resonance coming from the midrange driver (kevlar?):

 

 

Vandersteen 3A, cumulative spectral-decay plot at 50" (0.15ms risetime)

 

Read more at http://www.stereophile.com/content/vandersteen-audio-3a-loudspeaker-sidebar-3-measurements-page-4

[Jud]

3 minutes ago, semente said:

 

I also find this a plausible explanation and one's favourite musical genres also play a part here.

 

Sphile's 3A measurements show a more even tonal-balance although the upper mids and treble are shelved up by a few dB, maybe the 3A Sig is even better in this respect.

There seems to be quite a bit of resonance coming from the midrange driver (kevlar?):

 

 

Vandersteen 3A, cumulative spectral-decay plot at 50" (0.15ms risetime)

 

Read more at http://www.stereophile.com/content/vandersteen-audio-3a-loudspeaker-sidebar-3-measurements-page-4

 

I'm pretty sure Vandersteen has never gone in for Kevlar.  Carbon fiber or fiber/balsa sandwich, maybe.