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Horns - Necessary to complete the Audiophile Journey?

jhaider

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Duke

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Don't some of the bigger ones use transmission line bass?
Frank Dernie answered your question better than I could.

If I was a laboratory rat and the Tannoy Westminster was the maze, I would starve!
 

RayDunzl

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Thread Starter #246
One problem of classic Klipschs is driver mis-alignment, they're not time-coherent (Volti's own Rival is not either by the way):


Turning to the time domain, the Forte III's step response is complicated.
All three drive-units appear to be connected in inverted acoustic polarity, with the tweeter's output—the sharp down/up spike at 3.8ms—arriving first at the microphone.
The output of the midrange unit is the lazier downward spike just before 4.5ms followed by the slow rise of the woofer's output.
The decay of the midrange unit's step smoothly blends with that of the woofer, suggesting optimal crossover design.

https://www.stereophile.com/content/klipsch-forte-iii-loudspeaker-measurements

This could be easily addressed with a digital crossover or not so easily by moving the horns forward in the cabinet as this would require a redesign of the speaker enclosure and at this point you be better off buying beeter drivers and having someone build a new cabinet for you. I could be wrong but I don't think that analogue crossovers are very good at delaying...
How audible is time alignment?

How important is it, really?

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
 

q3cpma

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How audible is time alignment?

How important is it, really?

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
Maybe I'm wrong, but I'd say that significant misalignement could cause some cancellation at the crossover points due to frequency overlapping with too much phase difference.
 

tuga

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How audible is time alignment?

How important is it, really?

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
You are right that most speakers are not time-aligned.
But in many speakers the decay of one driver blends smoothly into the start of the next lower in frequency (as JA often points out in his measurements for Stereophile) and this as far as I know will potentially produce a flatter response.
 

Duke

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How audible is time alignment?

How important is it, really?
David Griesinger makes this argument: When the overtones arrive at the same time, instead of spread out over time, the sound has a quality which he calls "proximity", which might be called "presence" or "engagement". (This is not the ONLY requirement for "proximity".) We might think of this as an improvement in the perceived "signal to noise ratio". The sound naturally grabs our attention more, and (in the case of speech) this makes it easier for the ear/brain system to comprehend and retain complex ideas. And I speculate that maybe this is one of the (many) reasons why live unamplified music is so much more engaging and memorable.

So I think there are theoretical benefits which have nothing to do with imaging.

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
Obviously there are bigger issues which matter much more.

At the risk of committing the mortal sin of claiming something I cannot document, when I made a crossover change which improved the time-domain performance of one of my designs, it allegedly made a small-but-audible improvement to listeners familiar with the original version.
 
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Sal1950

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Thank you Sal!

I assume you are talking about the one with the wooden horn... which is technically an Oblate Spheroid waveguide. So it's actually among the more geeky types of horns.
Yes that one's a stunner but I also noticed a couple others, one called Bienville that had very attractive woodwork.
I love that stuff, maybe because I've always been so lame at doing anything with wood.
 

Duke

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Yes that one's a stunner but I also noticed a couple others, one called Bienville that had very attractive woodwork.
I love that stuff, maybe because I've always been so lame at doing anything with wood.
Thank you! The Bienvilles are the only ones that I actually assembled myself. I was more nervous than a nudist crawling through a barbed-wire fence. From now on, I'll pay someone who actually knows what they're doing.
 

tuga

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This is the step response of a Klipschorn AK6 (source)

The first spike is the tweeter, then there's a delay before the midrange's and the woofer's is not even showing in the plot.



For comparison here's the step response of the B&W 801 S3 (source)

Since all drivers are in the same polarity the first positive peak is the tweeter's, the second is the mid's and the third is the woofer's.
More importantly they all blend together seamlessly (there's no gap between the step of each driver).



The step response of a time-coincident speaker such as the Thiel CS3.7 (source) looks like this:

All drivers peak simultaneously but only in a specific sweet spot.



Here are a couple of Linkwitz's comments on phase linearity:

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


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


Now, a first-order crossover can be made phase-perfect at one point in space, but I feel quite strongly that you cannot just look at a speaker's performance at one single point in space.
The off-axis response is also very important to a speaker's overall performance in a real room, because the radiation in these other directions will add, through reflected and reverberant interactions, to what you hear.
Typically, we don't listen to speakers outdoors or in anechoic chambers.


https://www.stereophile.com/content/siegfried-linkwitz-page-4
 

tuga

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The delay of the Klipschorn's midrange driver is very obvious in the cumulative spectral decay plot, with the level of the midrange still rising to crest "long" (1.5msec) after the tweeter's has already subsided (36dB below peak level):


https://www.stereophile.com/content/klipsch-klipschorn-ak6-loudspeaker-measurements



The good integration is visible in the 801 S3's CSD:


https://www.stereophile.com/content/bw-matrix-801-series-2-loudspeaker-measurements-0



The CS3.7's plot shows all drivers peaking and decaying simultaneously:


https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements
 
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Frank Dernie

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How audible is time alignment?

How important is it, really?

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
Linn engineers did a demo of their DSP corrections at an enthusiast's show 5 or 6 years ago.
They started out with emulation of the passive crossover then loaded the corrections one by one and demonstrated the effect of each correction playing 2 tracks, one a multitracked rock music piece abnd the other a simply miked old "classical" recording (a Gilbert and Sullivan comic opera).
The corrections included frequency response and phase fluctuations due to resonances but also time alignment.
The time alignment made a small audible difference on the rock music track but the stereo image was much more solid on the simply miked classical track.
It was a memorable demo, probably the most interesting I have attended.

My feeling is that if you listen mainly to more recent multi microphone recordings mixed down to stereo there isn't much, if any, phase coherent information on the recording to reproduce. If you have lots of old stereo recordings which were captured on 2 carefully positioned microphones it is probably worthwhile.
Multi-channel is a differnt kettle of fish entirely, I have no idea how "real" the acoustics of the hall are on such a mix or to what extent it is entirely synthesised.
 

Lbstyling

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In my opinion they do, though I can see arguments both ways.

The woofer cone acts as a shallow horn for the tweeter's output, constraining its coverage to approximately the angle of the cone itself. Assuming the crossover frequency is about where woofer's dispersion matches the "horn's" coverage angle, the radiation pattern is probably exceptionally uniform from the crossover region on up. Which in my opinion is very good.

As with just about everything in speaker design there are tradeoffs, in my opinion at least. Personally I'd prefer to keep bass excursions out of the tweeter's "horn", like some of the more modern Tannoys do with their dedicated woofers.
Check this out for a mesurement....

This is a new coax 15 inch driver.

Screenshot_2020-07-13-09-36-47-842_com.android.chrome.jpg


Beat that!:oops:
 

Absolute

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How audible is time alignment?

How important is it, really?

I know it's supposed to drastically improve imaging, but those models that seemed to place it first in the design criteria (Dahlquist, Spica, Thiel) didn't end up dominating the speaker world and taking over everything because they were so self-evidently superior.
There's two ways I know to test this;

1. Try a Kii Three where you can switch on and off time-alignment at the click of a button with the Kii Control. Do this blind, take notes and check if you can hear it. I thought I could at times, but not reliable enough in my hostile acoustic environment to be certain.

2. Try with a room-corrected software like Audiolense/Accourate and make the same frequency response with and without absolute time-alignment.
I tried this too and think it's easier to hear the difference, but then again it probably should be as you change the timing/phase at the listening position in a pretty severe manner. Didn't try it with near-field speaker correction, though I can and probably should.
Usually I just end up listening to music.
 

Lbstyling

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Can you produce other measurements (f.e. THD, IMD, CSD)?
I thought that would get some attention:p

I asked EricH for distortion data via email, but he doesn't have further data for me.

This is the bass driver that is modified (by eminence)into the Denovo.

https://www.parts-express.com/eminence-beta-15cx-15-coaxial-driver--290-506

Inductance is high, and there is no mention of copper on the pole in the spec, so it will depend on what the modifications

The tweeter is a plastic diaphragm unit:

Celestion CDX1-1731

https://www.parts-express.com/pedocs/specs/294-2138--cdx1-1731-spec-sheet.pdf

I have not found any independent distortion data on either of these driver yet, ( currently praying to the HiFi gods for 'HiFicompass' to get a test sample!!):)

BUT current celestion designs are VERY good for the money (the flagship 1.5inch is possibly the best performing compression driver available)

Eminence are no slouch either, so I'm hopeful its circa -50db or more down at 95db. (Bear in mind this is a VERY efficient driver pair when looking at data. 98db/1w/1m)
 

tuga

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There's two ways I know to test this;

1. Try a Kii Three where you can switch on and off time-alignment at the click of a button with the Kii Control. Do this blind, take notes and check if you can hear it. I thought I could at times, but not reliable enough in my hostile acoustic environment to be certain.

2. Try with a room-corrected software like Audiolense/Accourate and make the same frequency response with and without absolute time-alignment.
I tried this too and think it's easier to hear the difference, but then again it probably should be as you change the timing/phase at the listening position in a pretty severe manner. Didn't try it with near-field speaker correction, though I can and probably should.
Usually I just end up listening to music.
I would rather do prolonged listening, say a week off then back on.
Switching back and forth would require the listener to know which aspects of the sound to focus on, otherwise clutching at straws...
 

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