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Old 14th February 2002, 02:52 AM   #1
Super is offline Super  United States
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Default BG Drivers

Just a heads up to those ribbon driver folks. Something I wasn't aware of, Parts Express is now distributing BG drivers, and lots of them, ranging from tweets to full length transducers. Take a look here: http://www.partsexpress.com/webpage....WebPage_ID=135

Now, if only I could save up some money...
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Old 14th February 2002, 03:19 AM   #2
ucla88 is offline ucla88  Tahiti
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yea, i saw that too. trying to figure out what to do with the neo8's if i get some. (not exactly an easy driver to design for)
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Old 14th February 2002, 10:44 AM   #3
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I give the RD-75 two thumbs ups. Practically speaking, it's good from about 150-250Hz on the bottom up to about 5kHz on the top. Excellent dispersion and imaging. Dynamics and detail retrieval are perhaps a smidgen less than the best electrostatic drivers, but still excellent. Very easy load to drive. The driver itself is purely resistive; about 5 or 6 ohms. For those who are into such things, they'll get quite loud, but you'll need a fair hunk 'o power to get them there. I don't think I've ever seen figures, but I'd estimate them to be in the upper 80s as far as sensitivity.
It's not the ultimate driver, but it'll do quite nicely until something better comes along.

Grey
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Old 14th February 2002, 12:58 PM   #4
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I think that with a $685.00 price tag for ONE tweeter (thats the 75" tall one), it would be much more COST EFFECTIVE to build a real electrostatic loudspeaker. See Below:

Matthew Anker's Electrostatic Loudspeaker Page
http://home1.gte.net/res0f2t3/index.htm

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Old 14th February 2002, 07:04 PM   #5
Won is offline Won
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Only up to 5k? That's pretty low for something that's supposed to be a tweeter. Do you use a separate (super/)tweeter with these lines?

-Won
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Old 14th February 2002, 08:09 PM   #6
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The RD-75 isn't a tweeter, it's a midrange. You'll be hard pressed to find very many other drivers than can cover five octaves as well as it does.
They have yet to build a purely resistive electrostatic driver; they're a difficult load for some amps to drive. Add that to the fact that they have poor dispersion, poor efficiency, and generally won't play very loud before they arc, and you're far from a perfect driver. Yes, you can build your own, and do it fairly cheaply. Like horns, they do a limited number of things extremely well but the tradeoffs have never seemed attractive to me.
I've also seen a fair number of homebrew electrostatics that were not tensioned evenly, which leads me to question how flat the frequency response was. Even the professionally built models have problems with resonances.

Grey
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Old 14th February 2002, 08:32 PM   #7
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Default Electrostatic drivers

not purely resistive.....? Not quite...... An electrostatic looks pretty much like capacitor is is not resistive at all. This is complicated by the usual step up transformer used to interface to it the amp. I have heard several loud electrostats. Acoustat or Sound Labs anyone? I sold my Acoustat 2+2s way back and bought Magnaplaner IIIAs and never looked back. Pass the Grey Poupon please.

H.H.
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Old 15th February 2002, 02:54 AM   #8
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Actually, the electrostats seem to have a very respectable efficiency. The amp barely sees a load from the 'stat. Running with the electrostat only, the power amp does not even get warm. Add a magnetic woofer and the amp behaves normally.

poor dispersion, poor efficiency, and generally won't play very loud before they arc

Poor dispersion is an advantage. The planar ESL has perfect imaging. Have you ever seen a curved magneplaner, wonder why? A planer ESL is louder since it concentrates the sound directly to the ear. Martin Logan curves their speakers to a appeal more to the consumer with a fat wallet.

I already answered efficiency. I've heard of people running 'stats with Stereo 70's.

An ESL will play plenty loud, and then WILL NOT ARC! I had this problem with my first pair, but I used glyptol insulation and lacquer to form an extremely effective insulation coating. This solved the arcing and allowed me to increase the bias voltage, thus increasing efficiency.

Like horns, they do a limited number of things extremely well but the tradeoffs have never seemed attractive to me.

The ESL acts like a midrange from 500Hz, and tweeter to 40kHz. The ESL uses no crossover in that entire span, how many 3-way systems can you do that in?

I've also seen a fair number of homebrew electrostatics that were not tensioned evenly, which leads me to question how flat the frequency response was.

Most builders heat-shrink the diaphragm, which leads to very even tensioning. I use the same mylar that Innersound uses. Barry Waldron's ESL Info Exchange sells it. It holds its tension very well.

Even the professionally built models have problems with resonances

What resonance? 99.95% of people are more likely to hear resonance out of their room or bass speakers before they will ever hear a resonance from the ESL. Remember, the diaphragm is held within a push-pull electrostatic field. There is no where for it to move in order to resonate.

These were all problems with the early 'stats. You should listen to a modern pair before you condemn them. A well designed pair will blow away maggies, most ribbons, and any dome tweeter with pure detail and imaging. Like the ribbons, the 'stats are designed to be a "fast" speaker. Every little detail is crystal clear.

Grey, if your ever in S.E. Ohio please stop by, and I will play my electrostats for you. I'm sure you'd be impressed
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Old 15th February 2002, 11:19 AM   #9
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M_Anker,
You seem to be under the impression that I haven't heard electrostats. Actually, I've heard one or two over the years. Perhaps I should have added that ESL fans, like horn fans (and Bose defenders), tend to be evangelists for their cause.
I've always said that ESLs do some things well. I like being able to get rid of crossover points, but unfortunately you've got to throw a transformer in there, which partially offsets the removal of the crossover. Now, a direct drive ESL coming straight off the plates of tubes...but that presents its own problems.
--Judging what kind of load a speaker presents by whether the amp gets warm is...questionable. "Add a magnetic woofer and the amp behaves normally." Hmmm.
--Beaming touted as a benefit? Shades of software mavens telling bewildered, angry customers,"That's not a bug...that's a <i>feature!</i>"
--You don't seem to grasp the idea that the reason Magneplanar speakers aren't curved is that the panels are limited to frequency ranges where they have decent dispersion. There's no reason why you couldn't build a curved Magneplanar; you just don't need to. Wait a minute...a curved planar...if you fiddled it just right, you could...never mind, I've got enough projects on the spike already. That one will have to wait its turn.
--Efficiency for electrostatic speakers varies widely, but on the whole they're less efficient than other speakers. Acoustats were fairly efficient, but didn't sound all that good due to horrendous resonances. The only Sound Labs model I've heard in recent years was the M-1(?). It promptly climbed into the same rarified strata occupied by the old Stax F-81--very, very good. Curved panel (okay, sectile), by the way, so I guess that means it's only for those with fat wallets. How efficient they are, I don't know. Upper 80s to low 90s? To me that's just average efficiency. Martin Logans and Quads have never quite been my cup of tea, sonically, although I could probably live with the Quads if push came to shove.
--Saying that you can't hear resonances from an ESL because they're submerged by room resonances is somewhat akin to the old chestnut: since speakers are the weakest link in the chain, you might as well not put much time, money, or effort into the electronics...the speakers are only going to mess up the signal anyway. Saying that the diaphragm in an ESL can't resonate because it's held in an electrostatic field is as silly as saying that a dynamic driver can't resonate because it's held within a magnetic field. Muddy thinking, at best.
I'm not saying that ESLs don't have their place in the world--I've heard some very, very good ones--but the tradeoffs make me cringe. I've even experimented with homemade panels a couple of times. Just never been able to listen around the problems. I'll say this, though, as a crass generalization: I'd rather live with electrostats than horns. (Bose products don't even enter into the equation. I'd have to be truly desperate in the desert island sense...and even then might simply choose to do without.)

Grey
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Old 15th February 2002, 01:16 PM   #10
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--Beaming touted as a benefit? Shades of software mavens telling bewildered, angry customers,"That's not a bug...that's a feature!"

The narrow dispersion of an ESL is a benefit, not a bug. Reason being is that instead of bouncing a sound wave around a room before it ever reaches your ear, the sound is sent directly to the ear. This produces nearly perfect imaging and seeming higher output. If a 2-foot wide sweet-spot is too narrow, then build a wider panel. The narrow sweet-spot and the incredible imaging appeal to me and quite a few ESL builders. When you listen to your speakers, do you not sit in the sweet-spot anyway?


--You don't seem to grasp the idea that the reason Magneplanar speakers aren't curved is that the panels are limited to frequency ranges where they have decent dispersion. There's no reason why you couldn't build a curved Magneplanar; you just don't need to. Wait a minute...a curved planar...if you fiddled it just right, you could...never mind, I've got enough projects on the spike already. That one will have to wait its turn.

Magnepan has been building their speakers taller and narrower over the years. The reason for this is that a tall, narrow source has better imaging.

but unfortunately you've got to throw a transformer in there, which partially offsets the removal of the crossover

What's really wrong with a transformer? I would rather have that than another crossover point. I'd like to ask you, what will do more damage to the sound: A transformer or 3rd order crossovers.

Saying that the diaphragm in an ESL can't resonate because it's held in an electrostatic field is as silly as saying that a dynamic driver can't resonate because it's held within a magnetic field. Muddy thinking, at best.

Where's a tensioned, ultra-low mass diaphragm gonna' go? Unlike a magnetic woofer, it has a very small excursion and extremely low mass. Magnetic woofers often "overshoot" or ring when in an improperly built enclosure. An ESL essentially has no where to go where its not held by an electrostatic field. I've never heard any resonance from my ESLs. You would have to have "golden ears" at least to hear such a thing. Also, what type of driver does not have the potential to resonate?

--Efficiency for electrostatic speakers varies widely, but on the whole they're less efficient than other speakers. Acoustats were fairly efficient, but didn't sound all that good due to horrendous resonances.

Why does efficiency really matter unless you're a horn fan. We're talking hi-fi here, not public address, etc. When building speakers, efficiency is the least of my worries.

You're right on a lot of points, and I am an ESL zealot. But not all ESLs have these problems.
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