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Old 23rd May 2013, 05:31 PM   #8781
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thank you for the answer.

it's a 1" polyimide driver on martin audio horn. not my measurements, so can not provide impedance. (it's not my driver, just consider buying.)

is the frequency response bad because of the driver or the horn?
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Last edited by perempe20; 23rd May 2013 at 05:35 PM.
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Old 23rd May 2013, 05:35 PM   #8782
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perempe20, start your own thread please.
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Old 23rd May 2013, 07:16 PM   #8783
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Quote:
Originally Posted by perempe20 View Post
hi,

can this be fixed? can I use this compression driver with passive crossover? what crossover topology shall I use?
Just a guess, but it looks like the horn is mismatched or too small. It could be digitally equalized, but I'd suspect directivity would be all over the place in the peak/dip region.

For example, one of the problems of classical exponential horns that are wider than they are tall is the notorious "pattern flip", which occurs one or two octaves above the published cutoff frequency. The crazy change in directivity, as well as the shift in overall diaphragm loading, is audible as a harshness, and some cases, grittiness that has given horns the "PA sound" reputation.

Although it might sound like I dismiss directivity, that isn't quite true. What I avoid are sharp changes in directivity with frequency (in less than an octave), or patterns that have sharp edges with ripples on the boundary. These correspond to changes in loading on the diaphragm, impedance variations, and reflections in the time domain.

Although the moderate T-ratio LeCleac'h horns are not constant directivity devices, they mimic the directionality and time response of direct-radiators, which is fine by me. I like direct-radiators and the way they sound and measure.

I just want more dynamics than you can get from soft-domes, which subjectively seem to compress the treble, at least compared to a good horn or AMT radiator. Soft domes are also grossly overtaxed if you try and take them down to 700 Hz, and mid domes have their own set of problems (diaphragm rocking due to lack of spider+surround suspension).

That's why I demurred earlier when asked about conventional soft-dome tweeters used in short waveguides. Just my feeling here, but that seems like the worst of both worlds: the potentially compromised time response of short horns, along with the modest dynamics of soft-dome tweeters.

The great virtue of the best soft-domes is outstanding time response; why goof it up by putting it in a short waveguide or horn? Getting good time response out of a horn or waveguide is non-trivial: it was reading Dr. Geddes' and Newell & Holland's books that underlined the point. You don't just slap it on, apply digital equalization, and hope for the best.

Last edited by Lynn Olson; 23rd May 2013 at 07:41 PM.
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Old 23rd May 2013, 07:49 PM   #8784
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I'm not saying it can't be done: I just haven't seen any commercial examples where the waveguided soft-dome has better time-domain performance than a high-quality soft-dome on a flat baffle.

It's certainly possible to make a waveguide with good time response for a soft-dome driver, but I wouldn't expect it to be small, or for the waveguide to be operated through cutoff, which I what I've seen from commercial examples.

Commercial speakers, particularly those aimed at the home-theater market, typically use small (3~4" mouth) waveguides, which you'd expect to cut off around 2 kHz or so. That's pretty close to the crossover, and it has to be kept in mind that directivity control (and resistive diaphragm loading) disappears quite abruptly at cutoff.

Last edited by Lynn Olson; 23rd May 2013 at 08:02 PM.
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Old 23rd May 2013, 08:31 PM   #8785
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lots of thank for the answer, Lynn. I would like to use passive xo, if it's possible.

i'm trying to build a sort of econowave speaker. i have limited experience with speakers in general. my friend is a music lover, and have a Scan-Speak Event TL (18W/8535, D2905/9300), and after that he bought a pair of Final Sound 150i electrostatic panels. (he uses them with 8" Scan-Speak subs.) he (and I) prefers the sound of the panels compared to the TL.
but after that, I listened to 4Pi speakers with 2226h/de250 drivers, and I really liked it. (it took me a day to travel to listen them.) I really loved the effortless sound, dynamics and sound of conga, timpani. i can not go back to ordinary low-efficiency speakers anymore.

Last edited by perempe20; 23rd May 2013 at 08:52 PM.
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Old 23rd May 2013, 09:32 PM   #8786
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Quote:
Originally Posted by Lynn Olson View Post
I just want more dynamics than you can get from soft-domes, which subjectively seem to compress the treble, at least compared to a good horn or AMT radiator. Soft domes are also grossly overtaxed if you try and take them down to 700 Hz, and mid domes have their own set of problems (diaphragm rocking due to lack of spider+surround suspension).

That's why I demurred earlier when asked about conventional soft-dome tweeters used in short waveguides. Just my feeling here, but that seems like the worst of both worlds: the potentially compromised time response of short horns, along with the modest dynamics of soft-dome tweeters.

The great virtue of the best soft-domes is outstanding time response; why goof it up by putting it in a short waveguide or horn?
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Lynn,

I did a study few months ago about the distortion of a 2" CD on a 300 Hz tractrix horn versus a bog standard cone/dome system, a B&W 602. The horn/CD combo sounds smooth, large and dynamic compared to the B&W, which sounds small, distant and distorted. The B&W actually has quite a smooth and flat response, but it just doesn't have the dynamics.

What I wanted to find out was whether distortion was causing the difference in dynamics. I was expecting to find the horn/CD combo would be clearly superior. But it wasn't. Here are the original results:
Linkwitz Orions beaten by Behringer.... what!!?

I subsequently measured the two speakers outdoors, and even the higher order distortion difference went away. So, why was I perceiving the difference in dynamics?

Tom Danley came up with a hypothesis that it is the direcitivity of the horn that makes it sound dynamic. He recommended taking the MTF and STIPA measurements in ARTA. He thinks they show the advantages of directivity.
Linkwitz Orions beaten by Behringer.... what!!?

Here are my measurements of MTF and STIPA of the B&W and 2445+tractrix combo:
Linkwitz Orions beaten by Behringer.... what!!?

Some differences begin to appear. If you follow the discussion in that thread and what Tom and Keyser point out, it is actually the direcitivity, and the increased clarity afforded by the higher direct to reflected ratio that causes us to perceive that immeasurable quality of dynamics.

A good example is to think of drums being struck in a highly reverberant room. It sounds loud. But if the drums are in a dead studio room, it doesn't sound as loud. It's the reflections and their level that make it seem loud.

And hence the next question, that if directivity is all we need, and if there isn't a real difference in performance in terms of distortion, then why not use the much smoother domes in a waveguide-like device?

Last edited by ra7; 23rd May 2013 at 09:34 PM.
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Old 24th May 2013, 01:40 AM   #8787
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Although I have great respect for Tom Danley, I cannot agree with the directivity hypothesis (tighter directivity results in impression of greater dynamics).

I've heard the LeCleac'h horns in several different contexts, and they sound even more dynamic than most horns, despite having a directivity pattern very much like a direct-radiator. What's unusual is the combination of horn dynamics with spatial qualities similar to an electrostat, or an MBL. Instead of tight and closed-in, the sound is wide-open and spacious, somewhat akin to the bigger Altec multicells (and nothing at all like the Altec sectoral horns).

My hypothesis is simply: greater headroom = greater impression of dynamics. A large-format compression driver has 10 to 20 dB more headroom than a 1" soft-dome, and this is directly audible, thanks to very brief transients not being compressed. Small-format compression drivers give up about 6 dB of headroom (compared to their big brothers), which is why I'm not as interested in them.

It has to be kept in mind that soft-domes are technically distorting all the time, due to deformation of the soft fabric of the dome, and greater accelerations result in more deformation of the dome. Direct-radiators are constant-acceleration devices, so more SPLs result in more G's on the diaphragm, which bends it more. Soft-domes have excellent self-damping, so there are no high-Q peaks (unlike metal diaphragms), but the deformation and lack of rigidity is there at all signal levels.

A similar thing goes on with midbass drivers. Polypropylene has excellent self-damping, but poly drivers much larger than 7 inches have a very dull, veiled sound. The only reason the Ariel gets away with poly is the drivers are very small. If you want to hear gruesome sound, try 12 and 15-inch polypropylene woofers. Paper is a good all-around compromise between self-damping and adequate rigidity, so it's been the large-format woofer cone of choice for the last eighty years.

Horns do not magically change the sound of the diaphragm. At best, they subjectively magnify the sound, providing more headroom, but they won't make a soft-dome sound like a metal dome, a metal dome sound like a soft-dome, or any other presto-chango magic. Phenolic diaphragms occupy in interesting middle ground, but their high mass makes them unsuitable for response extending to 10 kHz or beyond.

Beryllium, although costly at present, has a very interesting combination of rigidity and excellent self-damping. This diaphragm material works really well in direct-radiator dome tweeters (far superior to much more resonant titanium) as well as compression drivers. Now this is a dome tweeter that might indeed work very well in a medium-sized waveguide optimized for impulse response.

Last edited by Lynn Olson; 24th May 2013 at 01:57 AM.
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Old 24th May 2013, 02:04 AM   #8788
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The issue on "impression" of greater dynamics is a far more complicated issue than what meets the ears. Most variation is due to use of language.
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Old 24th May 2013, 03:31 AM   #8789
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So, how would one measure headroom? I'm really asking. I want to find a measurement that correlates with the perception of dynamics. Distortion isn't it.

Are you talking about an impulse that a dome tweeter doesn't fully reproduce? Wouldn't that show up in a distortion test? Barleywater had done some burst cycle testing on tweeters. And basically, it showed that their distortion was almost an order lower than comparable compression drivers. See this post, and the explanation a few posts down:
Active vrs passive

I am in complete agreement that large format CDs on the right horns sound magical. But just saying its headroom is not enough for me.

It's not just the directivity, it's the fact that you don't get early reflections. The direct sound is strong compared to the reflected level. That is what makes it clearer and us more tolerant of higher levels.

Last edited by ra7; 24th May 2013 at 03:57 AM.
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Old 24th May 2013, 04:10 AM   #8790
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Lest not forget some of the newer composite diaphrams for CDs such as the Radians with an Al surface and Mylar surround. As a 1" goes, the 465 is one heck of a driver for the $$$.

As to waveguide mounted domes, I've experimented with quite a few and guides from MCM, Dayton and QSC. Of course a 1" exit horn is going to need modification to work with a dome but IME when the transition is correct, they sound wonderful.

.......and for dynamics, time domain accuracy and smooth response, true ribbons in their passband are hard to beat with the the larger AMT type units such as the TPL-150 really gaining ground as one of the best received HF drivers in a long time.
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