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Chris A

Subconscious Auditory Effects of Quasi-Linear Phase Loudspeakers

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Hi Chris A - without getting into the summation aspect, lets say one wants to build a straight midbass horn.  Typically, a little midbass horn may have a 400 sq.in. mouth say 20" x 20".  With that size, is some of this "magic" lost due to loss of directivity?  For a dedicated midbass horn which sits on the floor and likely some distance from a back wall (primarily due to its length), what might be a minimum mouth area? 

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5 hours ago, Deang said:

Understand some, but not all. Still pretty interesting. A slower pass tonight when I have more time.

 

It's some chewy food for thought, for sure.  Anyone offering a shallow slope, "phase focused" passive two way networks for Jubs yet?  Could it be done without the complexity that Danley came up with?  I've been toying with the idea of doing some Chris style 402 based MEH, but would probably be more inclined if it could be done passively.

 

Until the budget allows, I'll just have to get my phase correct listening via TB full rangers, or suffer through that horrid phase distortion with my fortes (to their credit, Klipsch heritage three ways push the troublesome crossover frequencies outside our hearing's most sensitive band, which has gotta help somewhat).

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7 hours ago, Deang said:

Electrical first order isn't the same as acoustical first order.

 

http://www.audio-focus.com/THIEL2/PDF_Thiel/techpaper_general.pdf

 

3 hours ago, Don Richard said:

I hear (no pun intended) the pro sound guys refer to "coherence". This refers to how the output of a loudspeaker compares with the input signal. When the phase and the amplitude are flat, and impulse response is clean, the speaker sounds more lifelike and measures better. This seems to describe what you report hearing and observing. A coherent speaker is better able to deal with noise and acoustic interferences, and will not suffer from polar pattern degradation as badly when the wind is blowing.

 

https://www.prosoundweb.com/channels/live-sound/tech-topic-coherence-reverberation/

 

Your links have good info.

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17 hours ago, Deang said:

Electrical first order isn't the same as acoustical first order.

 

http://www.audio-focus.com/THIEL2/PDF_Thiel/techpaper_general.pdf

Yes.

 

Most people I think want to ignore the response of the drivers themselves with the electric filters--that the target frequency and phase response is acoustic, not electrical.

 

From that link:

 

Quote

Network correction

The last method for achieving accurate frequency response is to include electrical correction of response irregularities. THIEL speakers make extensive use of network compensation. Typically, about 40% of the network elements are used to achieve correction of what would otherwise be minor response irregularities in the complete speaker system.  As an example, figure 3 illustrates, for the CS6 tweeter, the target response, driver (in cabinet) response, the network response  and the final acoustic response (which is the sum of the driver and network responses). As can be seen, the actual response matches the target response very closely. Without the inclusion of 7 additional network elements the response would be much less ideal. Notice in the network response the non-simple shape of the curve; for example, the depression around 4 kHz and the strong response near 7 kHz. The picture below of the CS6 crossover illustrates the complexity required to achieve very accurate frequency response.

Thiel indicates that they're using extensive EQ compensation within the passive networks to flatten the overall response.  I suppose that's why the Thiel's have been pretty highly regarded in terms of their listening qualities.

 

11 hours ago, Ski Bum said:

Anyone offering a shallow slope, "phase focused" passive two way networks for Jubs yet?  Could it be done without the complexity that Danley came up with?  I've been toying with the idea of doing some Chris style 402 based MEH, but would probably be more inclined if it could be done passively.

The answer to your first question is yes, especially if you're willing to tri-amp and EQ each driver channel using upstream EQ capability (equivalent to what Thiel is doing passively).  Or you could do a simple set of first order filters and mono-amp, then EQ the resulting overall response upstream of the amplifier.  You could also do a two-way (like the K-402-MEH) the same way.

 

I might point out that the complexity of trial-and-error passive network design on a full-range MEH (two-way or three-way) is the real time eater, as evidenced by the Danley SH-50 design, which is also doing passive EQ compensation using notch filters, etc.  Doing the EQ upstream seems like a much better way of cutting down on the time spent and the number of parts in the passive networks.

 

Here a plot of the individual driver channel phase response vs. frequency of the SH-50 plus an overall phase response:

15999358_DanleySH-50PhaseResponseofConstituateDriversandOverall.thumb.jpg.d0d8a9511daba488276014d56bea3796.jpg

 

 

Chris

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14 hours ago, karlson3 said:

Hi Chris A - without getting into the summation aspect, lets say one wants to build a straight midbass horn.  Typically, a little midbass horn may have a 400 sq.in. mouth say 20" x 20".  With that size, is some of this "magic" lost due to loss of directivity? 

You will lose directivity at 170-340 Hz, which is a bit too high to be called a "midbass horn" (in my experience), and start to lose directivity about an octave higher than that--depending on the mouth rollout geometry. 

 

In order to go down to 100 Hz, you will need to go up to ~34-41 inches mouth size in at least the horizontal dimension.  However, if you have a separate bass horn that's good up to 200 Hz or so (like a La Scala, Belle, Khorn or Jubilee bass bin), then your 20" square mouth horn might provide you a way to get down to that frequency without horn bends.  I find that getting directivity to below 100 Hz seems to be the more of the "magic" frequency of loss of directivity gain for the type of effect that I've been talking about here.

 

YMMV.

 

Chris

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14 hours ago, Don Richard said:

I hear (no pun intended) the pro sound guys refer to "coherence". This refers to how the output of a loudspeaker compares with the input signal. When the phase and the amplitude are flat, and impulse response is clean, the speaker sounds more lifelike and measures better. This seems to describe what you report hearing and observing. A coherent speaker is better able to deal with noise and acoustic interferences, and will not suffer from polar pattern degradation as badly when the wind is blowing.

 

https://www.prosoundweb.com/channels/live-sound/tech-topic-coherence-reverberation/

A simple square wave input and monitoring the output on an Oscilloscope would tell the story about phase coherence!!

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24 minutes ago, Chris A said:

You will lose directivity at 170-340 Hz, which is a bit too high to be called a "midbass horn" (in my experience), and start to lose directivity about an octave higher than that--depending on the mouth rollout geometry. 

 

In order to go down to 100 Hz, you will need to go up to ~34-41 inches mouth size in at least the horizontal dimension.  However, if you have a separate bass horn that's good up to 200 Hz or so (like a La Scala, Belle, Khorn or Jubilee bass bin), then your 20" square mouth horn might provide you a way to get down to that frequency without horn bends.  I find that getting directivity to below 100 Hz seems to be the more of the "magic" frequency of loss of directivity gain for the type of effect that I've been talking about here.

 

YMMV.

 

Chris

Yes, and at that point your in subwoofer territory.

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For those of you reading this, the magic formula is that the lowest frequency of directivity is the mouth dimension (usually horizontal direction) that equals ~1/2 wavelength of sound.  That's the point where you're going to lose directivity control in that direction. And the horizontal direction is the one that really determines sound quality in rooms.  Vertical directivity loss is usually controllable using thick carpet and having high ceilings to control floor and ceiling bounce, but if the frequency of vertical directivity loss is a bit too high (like it is for the K-400 series midrange horns) then you've usually got issues with timbre shift and stridency of that excess acoustic energy bouncing off the ceiling and floor. 

 

The mouth dimension of horns is the controlling factor--not their throat dimensions, etc.  There is a magic size of horn mouth that works well, and below those dimensions, you trade to heavy losses in terms of directivity loss.  There are no "magic horn mouth-shrinkers" that can change that fact.  But if you place the horns in a room corner, depending on the ability of the horn shape to take advantage of that boundary gain and directivity, you can mitigate some of these effects--but you still must place absorption down on the floor, have high ceilings (or have absorption/low frequency diffusion on the ceiling), and do something about the extreme nearfield reflections within a yard/metre of the horn's mouth if you want to experience the effects described in this thread, IME.

 

Chris

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Posted (edited)

in the driver blend dept., is there hope for those who use passive crossovers, Heritage style horn setups and no DSP other than Danley's approach?

 

 

 

Edited by karlson3
simulation not pertinent to discussion

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Unless you're talking about using a DSP crossover to correct the time/phase alignment issue of the Dean--this loudspeaker configuration has considerable issues in that regard using a passive crossover and leaving the HF horn in the bass bin mouth as it was designed.  You will have other issues besides just adding delay to the HF channel, it seems.  I recommend opening up a thread on that subject (if you don't already have one). 

 

I've updated the settings of the K-402-MEH today to reflect the approach taken by the Danley SH-50, that is, not using a HF low pass filter in the BMS 4592ND to eliminate 90 degrees of phase lag centered at 6.2 kHz (I left the woofer channel LP filter in because I need the delay anyway). It took the better part of a day to get used to doing it that way using the Xilica. I'll update the K-402-MEH thread to reflect that process.  I'm listening to those differences having three-across nearly minimum-phase.  It sounds more "solid" than it did, for lack of a better term. 

 

I'd like to keep this thread centered on the subject of minimum phase or linear phase loudspeaker audibility, i.e., this isn't a design thread on something that doesn't have nearly minimum phase (or even linear phase using FIR filtering in a DSP crossover) across its entire pass band.

 

TIA.

 

Chris

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21 hours ago, ClaudeJ1 said:

A simple square wave input and monitoring the output on an Oscilloscope would tell the story about phase coherence!!

The Danley loudspeakers can output square waves over a wide frequency range, or so I've heard. Have you tried that on your SH 50s yet?

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Danley himself has said that the SH-50s will output a square wave up to ~2kHz.  I assume that the K-402-MEH will do the same, although I haven't yet turned on the square wave generator within REW to find out.  The fact that the loudspeakers can produce square waves up to a fairly high frequency is interesting, but probably itself is not audible.  The transient (time domain--impulsive) effects of being able to reproduce a square wave in steady state are definitely audible.

 

That's what caused me to start this thread.

 

Chris

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1 hour ago, Don Richard said:

The Danley loudspeakers can output square waves over a wide frequency range, or so I've heard. Have you tried that on your SH 50s yet?

No, but I have met and spoken to Tom Danley in person, as well as exchange Emails. I trust his technical integrity implicitly. He's not a BSer for sure, and he's a DIY guy at heart.

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On 3/12/2019 at 8:51 AM, Chris A said:

Or you could do a simple set of first order filters and mono-amp, then EQ the resulting overall response upstream of the amplifier.  You could also do a two-way (like the K-402-MEH) the same way.

That's what I did with my Quarter pies with K-402's.

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one of the best new topics on this forum in some time.

In the 1970s, B&O addressed this with their Uni Phase system, that used a "filler' driver between the woofer and tweeter. I never heard these, but I venture to guess that the audible improvement was only perceptible on certain music.

 

http://www.tonmeister.ca/wordpress/2015/10/29/bo-tech-uni-phase-loudspeakers/

 

Some of you know that I owned DQ-10s for many years until Hurricane Michael got them. The time aligned advantages of the design were most perceptible to me on material that had a lot of reverb, whether natural or added. The front to back "imaging" was pretty amazing. The lateral imaging was good, but not markedly better than my Corns. The DQ-10s had other design compromises that are not germane here, but they were the first consumer design to address "time alignment", if only for a narrow sweet spot.

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Is the indescribable effect something like "you can hear through the speaker directly to the music"?  I've experienced that with an inexpensive portable speaker, the Yamaha PDX-11.  It's a small 2-way bass reflex mono speaker, driven by its built-in 8 watt amplifier.  It definitely captures my attention.

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1 hour ago, Islander said:

Is the indescribable effect something like "you can hear through the speaker directly to the music"? ...

 

… o O (the unknown is categorized as a reason which cannot explain an absolute unlikeliness …)

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15 hours ago, windashine said:

 

… o O (the unknown is categorized as a reason which cannot explain an absolute unlikeliness …)

 

Okay, if you say so.

 

 

Chris, this idea of something indescribable is not helping me, and I suspect that other members may be equally mystified.  I get the impression that it's good, and the effect and sensation is worth pursuing, but is it at all possible to explain it a little bit more?  It would be appreciated.

 

Just because something is not measurable does not necessarily mean that it is not describable.  Intermodulation distortion started out as something difficult to describe and impossible to measure, until that Finnish scientist (Dr. Otala?) found a way to measure it. Some members seem to think that I'm a hopeless subjectivist, what with my "bigger cables sound better" beliefs, but your lack of description, the "when you hear it, you'll know what I'm talking about" way of not describing what you're talking about starts to sound mystical, and not something produced by hardware and software and how they interact with our brains and minds (yes, the two are not the same, although there may be some overlap) .  I'm objectivist enough to think that nearly any sensation or feeling in our rational perception of the world we live in can be described, in varying degrees of clarity.

 

Even esoteric drug experiences can be at least partly described.  Is it not possible to at least partly describe an esoteric audio experience?

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Pat,

  1. Did you read post #1?  A description was offered there in red typeface.  Please read it again (i.e., if that explanation isn't good enough, nothing will be).
  2. I'm pretty sure that a full range driver isn't going to sound like what I'm describing...because full-range drivers have far too many limitations for almost all music compositions to faithfully reproduce the effect.
  3. You're most likely going to hear the effect while playing recordings that didn't made use of multi-track recording machines, i.e., the kind of music where the musicians are all in the same venue playing at the same time and can hear each other in real time as they play their non-amplified instruments, and the microphones all experience crosstalk of the various musical voices.  "Direct-to-disc" recordings are good choices.

If you know that you're going through DFW International any time, give me a shout in advance.  It's much easier to hear rather than to try to describe it.

 

Chris

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Chris, I did re-read your earlier posts and did get a clearer picture of what you mean.  I haven't had the time to sit and go through your posts with full concentration, plus some of the stuff is definitely over my head.  With just scanning a bit here and there, I was getting an incoherent picture of what you were saying.  Your initial description was not too murky, but later posts made it seem that way.  This is what confused me.

 

As for full-range drivers, I have very little experience with those, other than terrible PA speakers at stadiums and the like.

 

The 402 horns are real marvels, and with mine being fairly high off the floor, due to sitting on top of the La Scala II full cabinets, plus DIY bases that are 4" thick, in order to clear one neighbouring audio cabinet, I felt it was a good idea to tip them forward, to aim them directly at the listening position.  Their lower edges are 106cm/41-3/4" above the floor, so they're tipped forward 7 degrees.  This should reduce any ceiling bounce.

 

As you may recall, I recently obtained a pair of K-691 drivers, so I'm looking forward to getting those installed, complete with their new Dx-38 settings.  Thank you.

 

Also, I do have at least one direct-to-disc LP, so that will be interesting to listen to, once the new upgrades and tweaks are all in place and doing their best. 

 

I will try to read your posts with full concentration.  However, as I mentioned in the previous post, while the effect you describe may be difficult to describe and impossible to measure at this time, it may not always be that way.  Just like it was with IM distortion a few decades ago, inquiring and experimenting minds may become able to clarify and maybe quantify this effect.

 

Thanks for the offer to hear your system.  If I'm ever in your area, I'll definitely take you up on it.

 

Pat

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