BG Drivers

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
 
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
 
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.
 
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
 
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
 
--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.
 
--If beaming is such a desirable thing, I'm sure we'll see a tidal wave of new commercial designs next year based on this newly discovered 'benefit.' If it's all the same to you, I don't think I'll hold my breath.
--Yep, narrow drivers have better dispersion. The RD-75s do quite well in this aspect. But you can't build a practical ESL an inch wide. So then you end up making them wider, which increases the capacitance, which makes them a harder load to drive, which leads to sundry distortions on the part of the amplifier, which leads to...
Not to mention, the wider they get, the worse the dispersion gets. Since you seem to feel that this is a benefit, I guess that's all to the positive in your book. Me? Yuk.
--I go along with transformers when I have to, meaning that I usedthem for the tube amps I built, but that doesn't mean I'm blind to various non-linearities. I've been working off-and-on on an OTL amp for years. To have tubes, but dispense with that pesky transformer...now that's an idea that I can get excited about. In the meantime, don't delude yourself, transformers impose yet more tradeoffs.
--Regarding resonances, I suggest that you study up a bit on such things. But just to stimulate your thinking, consider a drumhead, i.e. a thin, tensioned membrane that vibrates like mad given the slightest impetus.
--Not all ESLs have these problems? Hmmm. Show me an ESL that:
a) Isn't a capacitive load
b) Isn't transformer coupled (yes, there have been a very few examples of tube-driven panels, but they're rare and often unreliable)
c) Has no resonances
d) Doesn't beam
and we'll have something to talk about.
--I don't exactly claim the descriptive term "golden ears" for myself, but I imagine that others might apply it to me--sometimes in the prejorative sense, I suppose. Nonetheless, whether my ears are made of gold or lead, I demand a lot from my system, and I expect it to produce. If it does, I'm happy. If it doesn't, I start trying to fix it. I'm honest about my system's faults, because I've heard better systems and I listen to a lot of live, unamplified music. Right now, my biggest bugaboo is getting enough channels of various sorts of amplification going that I can try some experiments on imaging. I'm satisfied with the quantity of bass I'm getting, and with the quality, but it doesn't go as deep as I'd like. I once had subs down to the mid 'teens, right now, I'm cruising along in the mid-to-upper twenties. I want that last octave back, and I want it <i>yesterday</i>. And a few other things that I've noted here and there--no need to repeat them all now.
There are very few people who will tell you their system's faults in detail. Until they do, don't trust them when they say something's good. They're probably not very careful listeners...

Grey
 
Electrostatic drivers

Yep.... ESL and panel speakers have resonances, so do box speakers including some really nasty box resonances a lot of times. Room resonances are usually even worse.

Transformers are imperfect, so are passive crossovers containing non linear powdered iron or any magnetic material with high permability. (that is, non air core) And yet there are plenty of tube amps with tranformers that sound excellent.

Panel speakers beam. So do most dynamic box speakers to a degree. Also the wider the dispersion the more room modes you
excite.

There are a ton of trade offs in any speaker design. Go read Vance Dickason's Speaker Design Cookbook, Speaker Builder,
and Audio Electronics. And yet I can hear the difference between amplifier tweaks on my modified Radio Shack Lineam tweeter small speakers in my video system. Yes speakers are important but maybe not the top of the list of importance in a really good system. Garbage in, garbage out.

H.H.
 

ds21

Member
2002-02-11 6:51 am
WI
"...and I listen to a lot of live, unamplified music"

This line alway cracks me up!

Don't get me wrong I'm not picking on you GRollins. I respect your knowledge, it's just this line with out any clarification. Now if a person was there recording it direct to 2-track from the listening position...
 
Have you ever seen a horse?
Would you recognize one if you saw it?
How?
Well, there's a certain..."horse-ness" about the critter, right? If you've only ever seen one horse--or, more to the point, only seen a picture (i.e. a reproduction) of one--you might get flustered and say,"But what if it's a different color? What if it's a Tennessee Walker instead of an Arabian? What if it's a colt instead of a full grown stallion?"
Get over it.
Once you see enough horses, you get to where you can recognize one, even if it's a breed you might not have seen before. You can distinguish one from the rear, from the front, from the sides. Up close or at a distance. At dusk or at high noon. That's a horse. Period. How do you know? Because you've learned what horses look like.
That's why it's important to hear live music. Only people who don't go to hear live, unamplified music have trouble distinguishing 'horses' from, say, 'deer.' Both have four slim legs, have relatively short coats of about the same colors, have elongated faces, etc. There's a lot of superficial similarity between a deer and a horse. And yet, if you actually take the trouble to get familiar with horses (and with deer) then you have no trouble distinguishing one from another.
The easiest way I know of to tell an audio-fool from an audiophile is to play something like a recording of an acoustic guitar. If there's a lot of <i>sreeek</i> as the musician's fingers slide over the wound lower strings, the audio-fool foams at the mouth and starts nattering about "detail" and "resolution" and "clarity." Inevitably, the audio-fool decides that the system is "transparent" and...wait for it..."accurate."
The audiophile frowns and starts trying to decide if the flaw is in the recording or the system, because he's heard a guitar and knows that it's not natural for a guitar to have that much finger noise.
To mock live music as a reference does not reflect well on your listening acuity. In the long run, it is the <i>only</i> reference.

Grey
 

ds21

Member
2002-02-11 6:51 am
WI
"TRYING to decide if the flaw is in the recording or the system, because he's heard a guitar and knows that it's not natural for a guitar to have that much finger noise."

I guess what I'm trying to say is, which guitar with which strings,natural room reverb? what mic or mics, mastering... who's ears. Just want to take the above line out of the process.
 
The old Grey mare ain't what ......

A horse is horse, of course of course..... Grey noboby disputes that live music is the reference. My wife plays in the Dallas Wind Symphony. She listens to live music a lot. She has a good ear. She does't proclaim to be a loudspeaker designer though! I think what evoked the response was that after endless techno-speak you pulled out that old favorite "live music" fallback. Anyone worth his salt uses live music as a reference when designing. Even the reviewers (the last one's to know what's going on) talk about equipment in terms of musicality and realism now a days. It is interesting to read interviews with the best designers and hear them talk about the fact that we still are not there for reproducing the sound of real instruments playing in a real acoustic space. I wrote to Paul Klipsch when I was a student in 1976. He ended a letter once telling me that he was "going to the symphony that weekend to get his ears recalibrated." I never forgot it.

H.H.

P.S. I found this great picture a Wilbur and Mr. Ed studying a Dynaco Stereo 70 manual.
 

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ds21,
You can't tell the difference between room and artificial reverb?
Back to the concert hall.
For a truly horrible example of digital reverb to the max, check out the scene in <i>The Empire Strikes Back</i> where Darth Vader has chopped off poor Luke's arm, and he's hanging on with one hand. Vader tells Luke to join him. Luke screams "Never!" It's a nasty, ripping noise, completely unnatural. Start with that, then work backwards to more subtle examples.
The less reverb is used, the more difficult it becomes to tell what sort they used, but natural reverb (i.e. the sound of the room) is generally pretty easy to distinguish from any of the artificial kinds.
Live room echo, meaning the sound of the concert hall, isn't too hard to find. 'Artificial' room reverb, the sort created by placing a speaker in one end of a concrete room and a microphone in the other, then adding in a bit to the dry sound, is extinct. Spring reverb is still around, but is on the endangered list. Good examples of spring reverb can be found on '60s era studio recordings--or play with the reverb knob on an old Fender Twin.
You're on the fringes of an old philosophical argument, to wit: How do you know when you know something? You can branch from there into solipsism or perhaps decide to become a gnostic. I considered being a philosophy major for a bit back in school until I came to the rather unsettling realization that not once in the history of philosophy have they ever settled one of the core issues. Not once. Ever. Me? I employed the Gordian Solution...I whipped out my sword and slashed the knot in two. Reality is the final arbiter. When trying to distinguish a horse from another animal, don't sit around arguing about it, go out and look at a horse. All else is window dressing. Endless pulpit pounding and theoretical arguments don't impress me. I go out in the field and look at a horse. Then another. Then another. Until I understand the 'essence' of horse. People who want to argue about how many angels can dance on the head of a pin are welcome to waste their time doing so. I'm on my way into the woods so as to understand the essence of 'deer.' Once I get squared away on what a deer is, I go in search of an elk, then a moose...
To throw up all the various elements involved in recording an album as putative evidence that you can't know what you're hearing is silly. Honestly, I can't identify a Stradivarius by ear from other types of violin, but there are people who can. I haven't had the opportunity to hear more than three or four live in my life. I haven't seen enough examples of that sort of horse to be able to tell that species from the others. Perhaps with time, I'll get there, but SC is a poor state and Strads are in short supply around here. I've heard that there are people (professional violinists, for the most part) who not only can tell a Stradivarius from other violins, but can tell you <i>which</i> Stradivarius it is. There are only a few hundred left in the world, and they've all been given names over the years, and the true expert can tell you...ah, that's La Cathedral!
Harry,
Yeah, but which one's Mr. Ed?
I mean, really, we don't know what camera they used, or what gels were in the lights, or what kind of film stock was in the camera, and what if the film was left in the developing tank too long, or maybe...

Grey
 

ds21

Member
2002-02-11 6:51 am
WI
GRollins,

I don't even know what started this, I didn't go back and look, but you won't convince me that doing an a-b comparison of a live vocal or piano with-in seconds of being recorded is the same as knowing the "essence" of them, and I won't convince you, no argument about hearing someones voice on the telephone and knowing who they are, but does it sound as close to the real thing as posible? We are both looking for the same thing (I think) but in different ways, you use your memory and I use my studio, by the way have you heard the current sony reverbs? It's an unattainable goal but one that's fun to chase, so let's have fun;)

P.S. I think the picture, at least on my monitor, is a little too small too fool me...it's not a real horse.