Beyond the Ariel

[graaf]

Originally posted by gedlee


Since I have never heard those speakers I didn't think that you were asking for my subjective response, so I gave you a technical one. As to "we have always done it that way" - what can I say. If you are perfectly content with the sound of those old style horns then go for it. I always found them to have particularly poor sound quality.

The Summa waveguide does not go down to 800 Hz and it would be way too small at that frequency.

If you buy into "international acclaim and many prizes worldwide" as a testiment to good sound quality then you are pretty nieve about how those accolades come about.

It sounds a little like Lynn and I were being baited into an arguement here. If you already liked those speakers so much then why did you ask my opinion of them? If I thought that was the way to go then I would have done my speakers that way.

no argument oh no
who am I to argue?
just asking because It seemed to me that "the way" is somewhat similar to Yours

now I know
thank You for response

best,
graaf

[gedlee]

Originally posted by chrismercurio
Are their AES papers or other peer reviewed sources to look at that show:

"And, by the way, you do know that line arrays always have "tails" in their impulse responses - they have to - which means that they can never have compact impulse responses. Only point sources can have a compact impulse response."

Regards,

C

I'm not sure, that comment comes from my basic understanding of line sources etc. In odd dimensions (1, 3 5) the impulse response from a source is compact, while in even dimensions (2, 4) it has a tail. This comes from the basic math. A line source is basically a two dimensional source. (Interesting, this is why gravity waves - 4 dimensions - have to have a tail!) Its easy to see why in the case of a line source (not so easy for gravity!!). At any point in space, the contribution from parts of the source further and further away have to arrive at later and later times. The longer the line, the longer the tail. So even a flat piston has a small tail. However, put this flat piston on a waveguide and it will not have a tail anymore, because it will appear to have been created from a point source.

You can shade the line array and elliminate the tail (probably on along a line however), but that takes complex shading (time delays), amplitude shading alone will not do it.

There is a lot you can get from the basic physics of a situation.

[gedlee]

Originally posted by chrismercurio
Is there anywhere in the San Francisco bay area where a pair of your Summa speakers can be auditioned?

Marketing of the designs has been a disaster - probably comes from my vast experince in this subject . There simply is no way that I could make a viable product out of these designs myself. Thats why I have given up. The only Summa's are in homes and I can't give out those names for fairness.

The "big guys" have created a situation where a speaker that is not heavily marketed has no chance in the marketplace. This keeps the small intruder out of the picture. Its a very smart move on their part. Devastating for the consumer who wants a real option in the marketplace however.

[AR2]

Originally posted by gedlee
The "big guys" have created a situation where a speaker that is not heavily marketed has no chance in the marketplace. This keeps the small intruder out of the picture. Its a very smart move on their part. Devastating for the consumer who wants a real option in the marketplace however.

That's why we have the Burning Amp. October 18th 2008. Hope to hear you there!

[kstrain]

Originally posted by gedlee


In odd dimensions (1, 3 5) the impulse response from a source is compact, while in even dimensions (2, 4) it has a tail. This comes from the basic math. A line source is basically a two dimensional source. (Interesting, this is why gravity waves - 4 dimensions - have to have a tail!) Its easy to see why in the case of a line source (not so easy for gravity!!).

<snip>

There is a lot you can get from the basic physics of a situation.

That is very perceptive, it is actually the same reason: gravitational waves travel at the speed of light.

... possibly this is off topic.

But there is no chance of buying decent waveguides in EU, is there?

Ken

(ps. not "gravity waves", those are 3D)

[danny_66]

Here's another candidate for the midbass: the JA8008 HES

Troels Gravesen who you probably know from his excellent website:
http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm
has developed a high efficiency driver: the JA8008 HES
Specs can be found here:
http://jantzen-audio.com/download/PD...Oct07_v1-f.pdf

It seems to be an excellent driver according to this enthusiast review from someone who has used the JA8008 HES: http://www.troelsgravesen.dk/JA8008_response.htm

Some more info: http://www.troelsgravesen.dk/JA8008.htm

[Salas]

Originally posted by gedlee


To add to the above, line arrays do help with directivity - thats a plus, but as they do so they degrade the impulse response - thats a negative. A directive point source solves both problems - thats the bottom line to me.

That is why I never recommended a medium format Line Array in a normal venue, where a Nexo Alpha or PS 15 System could do just fine. Nobody ever listened to me against the notion that the all hot Line Array thing was the new Swiss knife. But hey, it looks cooler hanging than stacked, doesn't it?

[gedlee]

Originally posted by kstrain


That is very perceptive, it is actually the same reason: gravitational waves travel at the speed of light.

... possibly this is off topic.

But there is no chance of buying decent waveguides in EU, is there?

Ken

(ps. not "gravity waves", those are 3D)

Actually I didn't discover this. It falls out of the "Green's Function" approach in physics. The Green's Function is basically an impulse response, but unlike an impulse, which is only one dimensional - time - a Green's Function can be defined in any number of dimensions. So my comments came straight out of my "Methods in Theoretical Physics" class at school.

I just sent a pair of waveguides to Germany.

[Lynn Olson]

Originally posted by gedlee

And, by the way, you do know that line arrays always have "tails" in their impulse responses - they have to - which means that they can never have compact impulse responses. Only point sources can have a compact impulse response.

I completely agree. I don't know why this is controversial - it is obvious from inspection that the multiple arrival times of a vertical line array must be non-coincident, even with theoretically perfect radiators. The larger the vertical array, the more the response at the listening position is spread out as a series of impulses - and must also suffer from comb-filtering for the same reason.

A drawing of the arrival times on a piece of paper reveals that - nothing more than simple geometry. Multipath is troublesome enough to eliminate from diffraction (and internal cabinet reflections) in conventional speakers (horns or direct-radiators), why multiply the problem with a driver array?

At low frequencies (say, below 200 Hz), not much of a problem, since the wavelengths are so much larger than the differential in arrival times. But for frequencies higher than 1 kHz, problems with line arrays in the time, frequency, and spatial domains become much more difficult to resolve.

The only two complete solutions have serious drawbacks:

1) A concave curved array will only be accurate at one distance and one lateral bearing angle (one point in space), and badly in error everywhere else. It also bothers me on an esthetic level - concave sound emitters are extremely rare in the natural world, and I would expect a concave emitter to have a weird, hard-to-describe coloration, or perhaps an odd spatial distortion.

2) The Quad ESL63 solution of a phased-array, similar to military radars, has the drawback of simulating the virtual-image point source via multiple delay lines - this requires many amplifiers or a very complex crossover/delay line. Doing so accurately is a process of successive approximation that trades complexity of implementation against accuracy of pulse response - you could get into a million-dollar loudspeaker if you pursued this to the logical conclusion.

3) A partial solution is an amplitude-shaded line array with the outermost radiators sequentially low-passed - which begs the question of the inherent efficiency of the center radiator, which (by definition) sets the efficiency (and headroom) of the whole array. At this point, we are only one step away from a MTM-array multiway loudspeaker system, and two steps away from a traditional MT-array loudspeaker.

I think where people go astray is thinking the waves from the individual point-source radiators somehow combine into a cylindrical wavefront - but they don't. They pass right through each other. True, at the very lowest frequencies (comparable to the size of the array), there is mutual coupling and a resulting increase in efficiency, but this falls apart as the wavelengths become shorter. What starts out as an efficient loudspeaker at the lowest frequencies become dominated by comb-filtering and time-dispersal at higher frequencies - and these are errors that are degraded by equalization, since EQ spreads out the time-dispersal even more.

Combining high efficiency, ample headroom, and a compact pulse response with rapid time-decay characteristics is a hard nut to crack - the failure of the prosound world to address this over the last sixty years speaks to the scope of the problem.

The last serious attempt in the professional world is probably the Shearer theatre horn of 1935 - a long long time ago. The popularity of tap-dancing in movie soundtracks demanded a solution - and I have to admit getting 1 millisecond precision is pretty impressive for 1935. The ingenuity of the Tannoy Dual Concentric deserves an honorable mention as well - impressive technology considering the WWII date of the design. Since then ... well, the soundtracks are (much) louder, and the mass-market-mandated explosions, car crashes, phaser whizzes, and dinosaur thumps come at you from more directions.

[SunRa]

The last serious attempt in the professional world is probably the Shearer theatre horn of 1935 - a long long time ago. The popularity of tap-dancing in movie soundtracks demanded a solution - and I have to admit getting 1 millisecond precision is pretty impressive for 1935. The ingenuity of the Tannoy Dual Concentric deserves an honorable mention as well - impressive technology considering the WWII date of the design. Since then ... well, the soundtracks are (much) louder, and the mass-market-mandated explosions, car crashes, phaser whizzes, and dinosaur thumps come at you from more directions.

Hello Lynn,

how about the Unity horn? I wouldn't call them point source, but even so it seems they are pretty well regarded for their coherence.

And you've mentioned having some 6nd410 midranges. Did you have the chance to listen them? I am asking because I'd like to mate one with a waveguide but I don't know nothing about the subjective performance of these and I am not affording to experiment right now...

Good luck with your project!