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The Goals for an "Ideal Loudspeaker"


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#141 genek

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Posted 05 May 2010 - 02:04 PM

Hmmm... still haven't heard a good argument for constant directivity in spite of asking twice. Now that we have pushed the cloning of vintage hardware off to another thread, maybe we can get back to the topic. Can anyone put down a spec for the ideal speaker, or justify the basic tenants?

"Necessary and sufficient criteria."

How about goals that aren't necessarily sonic, like being movable by one person without the use of a lift truck, impedance that is compatible with a wider range of electronics, etc.?

#142 Zilch

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Posted 05 May 2010 - 07:42 PM

Can anyone put down a spec for the ideal speaker, or justify the basic tenants?

"Necessary and sufficient" criteria.

Conceptually, in keeping with Ken's original framing of the topic, I'm trying to formulate and posit goals as separate from how they might be accomplished.

Thus far, I have suggested two goals:

1) Room independent - adaptable to a variety of typical listening spaces.

2) Musical genre independent - competently renders any and all of them.


How about goals that aren't necessarily sonic, like being movable by one person without the use of a lift truck, impedance that is compatible with a wider range of electronics, etc.?

I believe equipment independence should be added to the list of goals, yes.

Do others agree?

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#143 Zilch

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Posted 05 May 2010 - 09:59 PM

Atkinson speaks @ #17 here:

http://www.ultimateavmag.com/podcasts/

Uhmm, and Toole @ #14 and Voecks @ #10.... :)

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#144 speaker dave

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Posted 05 May 2010 - 11:48 PM

The hard part of defining the ideal speaker is seperating the features that seem like a good idea from those that are requirements. Here is my list.

An Ideal speaker has:
Very flat on-axis response
Very smooth on axis response
Very flat and smooth response through any likely listening window
Smooth and resonance free power response, but of no particular curve
Holes in the power response are acceptable but peaks are not
Generally rising directivity (non flat d.i.)
Generally wide dispersion
Wide bandwidth with a -10dB cutoff below 35 Hz
Interfaces well with the room, gives a smooth in-room curve below 200Hz
Adequately low distortion. Low AM distortion with high woofer excursion

“Ideals” that haven’t been proven to be beneficial:
Flat phase response
Response extended beyond the audible range
Extremely low distortion
Low order or particularly high order crossovers
Any particular in-room curve, above 200 Hz
Any particular spectral response of reflections
High tech. materials
Exotic transducer types
Exotic cabinet types
Overly high or overly low directivty

Things that have been proven to be detrimental:
Flat power response

#145 genek

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Posted 06 May 2010 - 01:17 AM

How wide would "generally wide" be as dispersion goes, and how would that compare with some things we're familiar with (for example, the speaker we're not talking about cloning, the speakers you used to produce at Snell and Zilch's favorite waveguide)?

#146 Pete B

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Posted 06 May 2010 - 03:24 AM

Have people seen this:
http://www.burwenaud...und_System.html

#147 genek

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Posted 06 May 2010 - 04:16 AM

Have people seen this:
http://www.burwenaud...und_System.html

I remember that issue of Audio on the right. I really miss Audio magazine...

#148 speaker dave

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Posted 06 May 2010 - 11:07 AM

How wide would "generally wide" be as dispersion goes, and how would that compare with some things we're familiar with (for example, the speaker we're not talking about cloning, the speakers you used to produce at Snell and Zilch's favorite waveguide)?


The highest ranked systems in Toole's studies average a directivity index of about 6dB from 500 to 7,000 Hz. The typical CD waveguide is probably a d.i. of 9 or 10dB (say a 100 by 100 degree horn). Snell systems were totally conventional in directivity except the XA series that used symetrical arrays (di'Appolito) with about 3dB higher directivity than the usual driver on a flat baffle. (Adding some midrange vertical directivity is a good thing regarding floor bounce effects.)

I would aim for a 120 to 150 degree wide dispersion lateral and 60 to 90 vertical. (These are the -6 falloff points) Aim for response perfection in a +-30 degree window. You should hear the same direct response "anywhere on the couch".

Constant directivity waveguides have a benefit in that they may have very even response in the listening window, although the Geddes model seems to have some problems on axis. For home use I would make them wider dispersing than they typically are. A flat baffle with well radiused corners may be the best type of CD waveguide!

David

#149 speaker dave

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Posted 06 May 2010 - 11:34 AM

This was a typical Snell product. The array was used for theater products and home products (XA90 and XA75). the tweeter has a waveguide 150 degrees wide (if I recall correctly).

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#150 Zilch

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Posted 06 May 2010 - 04:12 PM

Constant directivity waveguides have a benefit in that they may have very even response in the listening window ...

Yah, we've kinda got a 60° x 30° listening window covered:

http://www.jblpro.co...f...3&docid=665

And can approach your 120° and DI = 6 spec, as well:

http://www.jblpro.co...f...&docid=1079

Though I'd argue against that.


...although the Geddes model seems to have some problems on axis.

Geddes maintains it's indicative of perfection. A perfect axisymmetric waveguide of necessity has interference on-axis.

His answer? Don't listen to Geddes speakers on axis, rather, use extreme toe-in, 45°, and listen at 22.5°.

We have suggested to him that asymmetric may be provide a better solution, although his early elliptical exhibited the same issue. He gives everybody a protracted "Why mess with perfection" argument, but says he'll try that.

[Problem is, he can't make the mold himself in his garage.... :) ]

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#151 genek

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Posted 06 May 2010 - 04:24 PM

Can we add "home workshop capability independent" to the list of goals? :)

#152 speaker dave

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Posted 06 May 2010 - 05:59 PM

And can approach your 120° and DI = 6 spec, as well:

http://www.jblpro.co...f...&docid=1079

Though I'd argue against that.


The 120 degree wide looks pretty reasonable to me. d.i. is more like 8, but put DSP EQ on it and add a sub and you may be done.

We were trying to define listening windows for brochures at Snell and it seemed like, on a cursory listen, that when you fell about 2dB into a crossover hole it was pretty evident. So, if you define best response as no more than 2dB variation from on axis, you don't get a lot of listening window width. Even with a 120 degree wide waveguide you only have about +- 20 or so for -2dB, and even less for vertical shift.

David

#153 Zilch

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Posted 06 May 2010 - 06:26 PM

The 120 degree wide looks pretty reasonable to me. d.i. is more like 8, but put DSP EQ on it and add a sub and you may be done.

Nah, building 'em is half the fun:

http://www.classicsp...r...ost&id=5313

Here's what I get for horizontals when I actually measure the larger 90° eWave "Deluxe":

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#154 Zilch

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Posted 08 May 2010 - 02:44 AM

I've seen it stated many times that the ideal loudspeaker would be suitable for use across a wide range of reproduction applications -- two-channel music, multichannel, home theater, studio monitor, sound reinforcement, even.

Do we buy that as a goal?

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#155 genek

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Posted 08 May 2010 - 03:57 AM

I've seen it stated many times that the ideal loudspeaker would be suitable for use across a wide range of reproduction applications -- two-channel music, multichannel, home theater, studio monitor, sound reinforcement, even.

Do we buy that as a goal?

Certainly WRT to two-channel, multichannel and home theater. I do that with mine and would expect it from any speaker that is supposedly better than what I have now. I don't know what special requirements a studio monitor or sound reinforcement speaker might have compared to a home speaker, and if meeting them would make the speaker more expensive, harder to move around, or visually unattractive, I'd prefer the speaker come in home and professional versions rather than a one-size-fits-all.

#156 Zilch

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Posted 08 May 2010 - 05:22 AM

Over the years, many designs have been made in both standard and "utility" models, among these, even the JBL Paragon.

In original large Advents, I have read that the vinyl-clad utility outsold the furniture-finish variant.... :)

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#157 genek

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Posted 08 May 2010 - 03:13 PM

Over the years, many designs have been made in both standard and "utility" models, among these, even the JBL Paragon.

In original large Advents, I have read that the vinyl-clad utility outsold the furniture-finish variant.... :)

AR's were the unfinished pines; fine with me as long as they aren't the only choice, but what I was thinking about was more along the lines of 10000 watt power handling or the ability to survive being thrown off a truck. If the ideal speaker does everything I want it to do it won't bother me one bit if it has other capabilities, as long as they don't make it unnecessarily (to me) expensive or harder to use in a home.

Advents were marketed heavily at starving students; I think the ones who picked the vinyl boxes to save $30 a pair are the ones responsible for all that black stuff that I hate today.

#158 Steve F

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Posted 08 May 2010 - 07:17 PM

AR's were the unfinished pines; fine with me as long as they aren't the only choice, but what I was thinking about was more along the lines of 10000 watt power handling or the ability to survive being thrown off a truck. If the ideal speaker does everything I want it to do it won't bother me one bit if it has other capabilities, as long as they don't make it unnecessarily (to me) expensive or harder to use in a home.

Advents were marketed heavily at starving students; I think the ones who picked the vinyl boxes to save $30 a pair are the ones responsible for all that black stuff that I hate today.


In retrospect, it's absolutely astonishing that the difference in Advent's cabinet choices were only $14 (102-116), or that the 2ax difference was a mere $19.00 (109-128).

Couldn't be done today for anywhere near that little a difference.

Steve F.

#159 genek

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Posted 08 May 2010 - 09:01 PM

In retrospect, it's absolutely astonishing that the difference in Advent's cabinet choices were only $14 (102-116), or that the 2ax difference was a mere $19.00 (109-128).

Couldn't be done today for anywhere near that little a difference.

AR cabinets during the classic period were sourced from relatively small domestic suppliers and involved a fairly large amount of handwork, so the difference in cost between the finish options were primarily based on the materials. With today's automated/offshored high-volume
manufacturing methods, if "ideal speaker" is produced in any sizable quantity you'll probably have to pay more for an unfinished "utility" version.

#160 speaker dave

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Posted 08 May 2010 - 10:09 PM

I've seen it stated many times that the ideal loudspeaker would be suitable for use across a wide range of reproduction applications -- two-channel music, multichannel, home theater, studio monitor, sound reinforcement, even.

Do we buy that as a goal?

I think the goals of accuracy would be similar for speakers of any intended use, but obviously sound reinforcement or studio use places extra demands and some compromises may be called for. Needs for higher SPL will always force some compromise. I put a lot of effort into getting KEF KM1's to play loud enough for studio use without degrading fidelity.

There have been some interesting papers that point out that studio people want higher directivity for studio use and wider directivity at home.

Coverage requirements are a specific PA need. I'm typically doing calculations of best height behind the screen and right CD horn to use, to balance out the level across a cinema audience. That isn't an issue for domestic systems.

David




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