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Old 23rd December 2004, 02:24 PM   #21
Previously: Kuei Yang Wang
 
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Konnichiwa,

I have these as well and they are rather good, if also a little compromised (anything limited to sensible size/cost will be).

Thread about Prometheus and Supravox Open Baffles

My "normal" open baffles with the Bicone Signature Supravoxes tend to be a little more coherent and with a slightly more accurate tonality, but Prometheus counter with superior dynamic range and bandwidth. It in only once you move up to C37 laquered and modified Supravox fieldcoil drivers that the Prometheus is definitly outclassed, but even than not by THAT MUCH.

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Old 23rd December 2004, 02:30 PM   #22
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Konnichiwa,

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Originally posted by EFHeath
<http://scrounge.org/speak/ultimate.html>
Here is one view, not that I am advocating such lunacy!
You call that lunacy? I'd say it is only mildly disturbing. Now proper, pukka pie lunacy looks like this:

Click the image to open in full size.

Dick Burwens 20KW Home Audio system, all hornloaded....

Oh, in case someone does not know, Dick was the Mentor of Mark Levinson (the man Mark Levinson, currently under the Red Rose banner, previously Cello and Mark Levinson Audio Systems)....

20,000 Watt Home Hi-Fi System - <http://scrounge.org/speak/burwen/>

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Old 5th January 2005, 07:20 PM   #23
simon5 is offline simon5  Canada
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The Fostex FW800N is not the best woofer to achieve my 8 Hz goal, even if it's probably the biggest woofer in production.

The Fs is good at 18 Hz, but Xmax at 2,3 mm is not good.

For the price of one FW800N, I can get several Ascendant Audio Avalanche 18" subwoofer drivers with 27mm Xmax, 16 Hz Fs, better displacement than a Tumult, lower Fs than a Tumult and a Fostex FW800N, lower price than a Tumult.

http://www.ascendantaudio.com/Products.htm

But then, to really achieve my goal, I guess that only the Parthenon is a valid option.
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Old 5th January 2005, 08:00 PM   #24
Bill F. is offline Bill F.  United States
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Quote:
So can someone who understands a heck of a lot more about speaker design (& KYW's ramblings) tell me what DIY (or commercial) speaker design comes closest to what KYW suggests as being optimum?
I think perhaps my baffles are somewhat aligned with the evil KYW's philosophy. Total cost for the fully built pair including bass amps: <$600.
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Old 5th January 2005, 08:12 PM   #25
simon5 is offline simon5  Canada
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I forgot to say that the Avalanche 18" has also better sensivity than a Tumult, I'm almost wondering why Tumult exist now!
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Old 5th January 2005, 11:07 PM   #26
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Good reading KYW.

Although, believe it or not, I am not sure I am satisfied with your conclusions. As I struggle to slowly learn how to design my own speaker at my snail's pace of intermittent dabbling, I personally get more frustrated with dynamics than anything else. Not knowing enough theory or practice to distinguish time coherence from phase shift or know if there is, I wonder if your mention of coaxial solutions is too superficial? Does the application of active crossover and coaxial placement actually cure the issue of dynamic response or is it still muddy in the crossover region?

And to really play devil's advocate and to address this to a larger group, does the unwaivering recommendation of yourself and the other gurus to go wide range drivers/big sensitivity come purely from your classical/jazz-music-tastes/tube-gear and are you guys just making us build speakers that shove that nasty crossover region right where that Motley Crue bass/drumline sits to pi$$ us off? (Yes that was a joke )
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Old 5th January 2005, 11:14 PM   #27
Previously: Kuei Yang Wang
 
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Konnichiwa,

Quote:
Originally posted by leadbelly
I wonder if your mention of coaxial solutions is too superficial?
Maybe, maybe not. There are few possible coaxial solutions that did work right (chiefly the Eckmiller) and if you use a modern Digital X-Over with the option to "time align" the non-coincident sources things may get better sill.

Quote:
Originally posted by leadbelly
And to really play devil's advocate and to address this to a larger group, does the unwaivering recommendation of yourself and the other gurus to go wide range drivers/big sensitivity come purely from your classical/jazz-music-tastes/tube-gear
Not really. I do listen to a lot of stuff besides classical/jazz. And with all due respect, when I pull some of my classical warhorses out (try the Ravel version of the "Pictures" or Saint Saens Organ Symphony) and turn it up to what I consider "sensible" levels many systems that do fine with Hard Rock and rap start hitting then endstops.

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Old 6th January 2005, 04:59 AM   #28
ScottG is offline ScottG  United States
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While I agree with much of the "essay" I'll voice my disagreements. (correct spelling and grammer will be absent from this reply - obviously..)

Disagreements:

1. Dispersion above the modal region..

Controlled dispersion (horizontally) leading towards decreasing (usually significant) spl levels off-axis does NOT preserve "imaging", rather it destroys it. This "destruction" however is not the same as the "destruction" caused by room-reflections. Most of the "imaging" in this region is TIME related (phase linearity becomes more important as freq. decreases). In the nanosecond to low millisecond range off-axis reproduction in time (and intensity) controls the degree and quality of specificity of the "image".

Getting this aspect WRONG (while doing most everything else "right") generates a subjective response similar to increasing dampening factor (for a given moving-mass): Image specificty remains nominally the same, but quality greatly diminishes.

Subjective responses (wrong vs. right in this instance) can be summed-up as:
"I can easily point to the location of the flute playing, but it isn't holographic - its more like a point in space where it is playing."

(Note 2 things however: 1. this is dependent on the recording (though it doesn't have to be natural) 2. Phase can play a roll here in "aural holography" if the freq. response of the reproduced dominate sound extends lower in freq. - and it doesn't have to be that far.. typically starting below 800Hz).

Of course this is "at-odds" with reducing room-reflections which IS a desirable quality (to an extent). Room Reflections in this freq. range ADD to the sound and tend to obfuscate imaging while adding ambiance.

Subjective responses (wrong vs. right again) can be summed-up as:
"I can point to the location of flute playing but the specificty isn't as distinct - rather fuzzy sounding, plus there is more air in the sound with a slight increase in soundstage bloom".

The nice thing here about this is that the more attenuated in time (i.e. less correlation) these reflections become, the less "fuzzy" the "imaging" gets. You can fairly easily do this with diffusion techniques AND/OR by simply moving yourself closer to the speakers. Additionally you can also use ABSORPTIVE techniques but don't over-do it! (please notice that I prefaced reducing room reflections via: "(to an extent)".) Its fairly commonly known that a reduced yet audible level of added "room-noise" generated by in-room reflections is DESIRABLE to maintaining the illusion that reproduced sound can offer.

Absorption can also help with spectral balance by reducing the level of high freq. s vs. that of lower freq.s.

Neither method will be perfect of course, but usually with a bit of trial and error it can be more than good enough to off-set any advantage limited dispersion might have over something approaching an omni.

So with the following in mind - don't think that limiting dispersion is a good thing. It CAN be better than the alternative IF you can't accomplish a modicum of proper listening room treatment. (and note that last time I checked Thorsten likes to listen "far-field" which could indicate his preference for limited dispersion..)

2. Dispersion below the modal region (limited disagreement though)..

There are two ways to achieve dispersion lower in freq.. The first and only current relevant method is based on creating a null-phase node via an out-of-phase summation with your in-phase signal. This is typically your "dipole" behaviour but the concept (and result) can be extended further via a second-order gradient (which increases the amount of null-phase). (the second method is real science boardering on voodoo that could ultimatly turn into a meathod for generating power in excess of input.. currently though its viewed for its military applications.. I'll leave you to ponder this one.)

Now the problem then is our physical response to the contribution of a null-phase node. Reducing pressurization in this manner reduces the "impact" of the waves pressure to our bodies (i.e. we are essentially bags of water and enjoy the "ripples" sound can make).

Subjective responses (wrong vs. right again) can be summed-up as:
"The kick drum is missing its kick.. It seems to lack punch or slam that I should be feeling in my gutt".

So then, what to do about it..

Unlike the problem and the solution on room effects above the modal region, here we have a problem that detrimentally influnces are hearing F A R more. Additionally, the "cure" is a bit more difficult to achieve.

Digital eq. is PRIMARILY the solution here BUT the upper end of the modal region is "square" in the midrange and many people find this off-putting (either because of a belief that digital per se is "bad" or that they have actually found it to be detrimental to the midrange in such a situation). Analog could be used, but to achieve a proper effect would require a GREAT degree of sophistication and flexibility in the design. Additionally, despite having the ability to "tailor" the freq. response, the net result may have TO MUCH pressurization in comparison to the event.
(Note however that in some system designs, digital eq. offers one more signifiant advantage - the ability to achieve reasonably linear phase in the region where virtually all drivers suffer phase rotation (in some cases nearing 180 degrees) - the lower midrange. Of course this phase rotation stops its rotation in sealed and dipole designs, but the continuation of phase lower in freq. is usually at the point the phase rotation stoped. As mentioned before, this DOES effect imaging - particularly image position.)

There may however be a more-than suitable compromise - (that could still benifit from the freq. and possibly phase linearity that a digital eq. could provide).

If the design were to use two similar drivers covering the same bandwith where one was used in a dipole configuration and the other in a properly constructed sealed chamber then you might achieve a level of room pressurization that was more natural to the event that still reduced room node effects (particularly if you had a level control for the driver in the sealed chamber). Additionally, (though its a guess), the dipole would likely be better served by being the closer driver to any adjacent boundries (like the floor).

An alternative approach that could STILL use digital compensation for eq. and room pressurization effects, (but not phase compensation), that was NOT IN THE SIGNAL PATH (i.e. purists rejoice!) could be derived by spliting the signal at some point (usually the pre-amp) and then sending the new secondary signal to a digital eq. that eventually "terminated" in a driver with the exact same non null-phase loading as the "main" loudspeaker has. This secondary driver system could be "tailored" for phase and freq. response via the eq. to create null phases precisely where in the freq. response the rooms modal effects create a "bump" in freq..

(also note that lower freq. linearity sometimes be achieve with multiple "subs" used throught the listening space or simply using 2 subs in the correct "spots" in the listening room.)
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Old 6th January 2005, 09:07 AM   #29
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Konnichiwa,

Quote:
Originally posted by ScottG
Disagreements:

1. Dispersion above the modal region..

Controlled dispersion (horizontally) leading towards decreasing (usually significant) spl levels off-axis does NOT preserve "imaging", rather it destroys it.
I'll keep this really simple.

The above is simply untrue, as far as it applies to reproducing the recording as it was made. If you have an excessive wide dispersion you add too much room generated diffuse sound, which leads to the image becoming diffuse, specific insturment sizes are by far overblown and unrealistic, basically the exact type of imaging you get from most "High End" speakers and which an accurate monitor does not produce.

If you like to alter the spatial aspects of the recording, fine, but it then should be done conciously and in an controlled, adjustable way, IMHO at least.

Quote:
Originally posted by ScottG
This "destruction" however is not the same as the "destruction" caused by room-reflections. Most of the "imaging" in this region is TIME related (phase linearity becomes more important as freq. decreases).
Controlled dispresion and time coherence are not exactly mutually exclusive, are they now?

Quote:
Originally posted by ScottG
Of course this is "at-odds" with reducing room-reflections which IS a desirable quality (to an extent). Room Reflections in this freq. range ADD to the sound and tend to obfuscate imaging while adding ambiance.
Exactly my point. Hence controlled dispersion, rather than an overly wide angle dispersion (or worse, uneven dispersion with frequency).

Quote:
Originally posted by ScottG
So with the following in mind - don't think that limiting dispersion is a good thing.
It is neither a good or a bad thing. It is an essential requirement if you desire to reprouce the recording ambiance and imaging as recorded. If you dislike the recorded ambiance and imaging, well then it's time to correct.

Quote:
Originally posted by ScottG
It CAN be better than the alternative IF you can't accomplish a modicum of proper listening room treatment.
Well, given the significant problems in making absorbers that behave controlled and linear over a wide frequency range and the many other issues observable with room treatment (and I am talking strictly acoustically here) you may forgive me for suggesting to avoid the problem occouring to attempting to fix it afterwards.

Quote:
Originally posted by ScottG
(and note that last time I checked Thorsten likes to listen "far-field" which could indicate his preference for limited dispersion..)
I always listen far-field, of course I do. Nearfield setups I find physically uncomfortable (I like to listen to music, not be assaulted by it) and totally unnatural in the spatial aspects. Images tend to be severely undersized and depth is overly emphasised comapred to "width" and "panoarama", very unlike the real thing. If I listen near filed I might as well use 'can's and these I can stand not at all...

Quote:
Originally posted by ScottG
2. Dispersion below the modal region (limited disagreement though)..

Now the problem then is our physical response to the contribution of a null-phase node. Reducing pressurization in this manner reduces the "impact" of the waves pressure to our bodies (i.e. we are essentially bags of water and enjoy the "ripples" sound can make).

Subjective responses (wrong vs. right again) can be summed-up as: "The kick drum is missing its kick.. It seems to lack punch or slam that I should be feeling in my gutt".
Actually, if you design a dipole with a suitably low LF cutoff you will be surprised about how much the Kick-Drum kicks and how much it does so in the way a real one does. Do you realise that a REAL Kick-Drum is basically a 24" Diameter dipole?

Let me put it simply. Based on my experience, which includes a quite wide and diverse range of speakers, equalisation for room effects, room treatment and so on, I find what I originally wrote about to hold true. It is not the "final word", but it is the result of considerable empirical research, theoretical resarch and much observation.

Now given that recordings are NOT perfect and that personal tastes in reproduction of music diverge it clearly is not "THE GOSPEL", it is a set of collected views that concern themselves mainly with a reproduction that is as realistic and natural as can be achieved within the limits of the recording. To some the results may be indeed "the best sound they ever heard", to others it may not provide anything like "good sound", such is the human condition.

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Old 6th January 2005, 02:10 PM   #30
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Lastly, it should also be clear now that using multi-miking and multitracking during recording will severely compromise all aspects of the musical performance recorded even WITHOUT massive additional "doctoring".
As a musician, i find this to hold very true, although not only in the "soundstage" sense but also in the quality of the music that is recorded. A lot of the "feeling" you can get recording a group of talented musicians is totally lost when multitracking. An individual in a group that "know" eachother well musically often interact spontaneously to the playing of the others. This cannot be recreated (to any extent) with multitracking.

It's like the soul or groove of the music is lost. Sometimes (on good recordings with skilled musicians) it takes a trained ear to know the difference, sometimes it is obvius from the first note played.

Also, going back to the Hifi-end, isn't controlled directivity a little lonesome? Or can the sweet spot be sufficiently large to incorporate several people (without having very large listening rooms)?

/Andreas
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