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Apogees and ethics - comments

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Posted on February 4, 2012 at 12:26:21
mbhintz@fastmail.us
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Location: Minnesota
Joined: February 3, 2012



I have a pair of Apogee Divas that I was/am considering selling because I anticipate moving to a house with a smaller living room. Additionally, I am kind of tired of them dominating the space I currently have. They are the best speakers I've ever had, and not by a little. I bought them used, and they have the infamous buzz on test tones, but I have never heard it on program material and am pretty fussy. Anyway, after talking to Rich Murray at true sound works and describing the situation and the small "wrinkles" in the bass panels, he cautioned me about selling them and transporting them in their current condition would likely make the buzzing/wrinkles worse. That leaves me the following options:

Keep them, enjoy them, deal with the move when and if it has them

Sell them with full disclosure and (presumably) take a big bath on them financially

Refurbish them with new ribbons (~ $5K).

The plus side of the last option is that they will presumably be a lot better, and I should be able to sell them with clear conscience for a much higher price. Still, 5K is a lot to put into a 20+ year old speaker. I am told that the new panels/ribbons should last basically forever. The other option is to take the bath and buy some 3.7 Maggies which I recently heard. They are very nice, but they are not the Diva's, and they are still big panels, albeit quite a bit smaller. I know it is my choice in the end, but would appreciate comments/thoughts on the matter. FWIW, at the same time I heard the 3.7's, I also heard Wilson Sophia 3's driven by top shelf ARC electronics. Also very nice, but nowhere near as involving, particularly at low levels as the Maggies, let alone the Diva's.
Happy Listening!

 

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Keep em, posted on February 4, 2012 at 13:06:00
Satie
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You are talking about finding an alternative to one of the best speakers ever built. The basic design is solid and the revised versions are tweaked better, not miles ahead, at least so goes the buzz online.

I would suggest that you go on with them, and when the time comes, have them refurbished. Save up a refurbishment fund so you are prepared, and if you are wanting a different sound get a tube preamp and roll your tubes. Alternately, if you area all digital, get a digital EQ and play around with alternater FRs.

As to the visual domination, hang a screen of acoustic cloth in front of the setup so you don't see it - if you must.

 

RE: Apogees and ethics - comments, posted on February 4, 2012 at 13:51:40
josh358
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Seems to me all the options are ethically equivalent, as long as you sell them with full disclosure if you do decide to sell.

I've noticed with Maggies that the refurbished ones don't seem to go for as much as they should by comparison to the unrefurbished ones. I'm not sure why this is but it may have to do with sticker shock on the refurbished ones. Or maybe some people want to save money by doing the job themselves. Not sure if this is true of the Apogees as well but it may make more sense to let the next guy fix them if/as he wants.

Of course I can't decide for you whether to keep them or not but I think I agree with Satie that they're worth a $5000 investment. It looks like they fetch about $4000 used (I'm looking at the Blue Book, at what I'm guessing are the unrefurbished ones) so the total cost of fixing and keeping them would be about $9000 -- and the question then is whether you could be happier with something else for that sum.

 

Definitely NOT fix AND sell. big mistake. Let a buyer decide to fix or not.., posted on February 4, 2012 at 14:00:41
That is if you sell them.I have Magnepan 3.6 in my apr and have no problems thinking about getting 20.7s someday.
I would cetainly keep them until you actually move, then decide if they fit in or not.
If they have asound you love, just get them refurbished. And maybe the frame painted? when being refurbished?

 

wow what a beautiful system, posted on February 4, 2012 at 20:11:18
Green Lantern
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So sorry to hear you may have to part with the panels.






 

RE: Apogees and ethics - comments, posted on February 4, 2012 at 20:37:42
mbhintz@fastmail.us
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Posts: 2
Location: Minnesota
Joined: February 3, 2012
Thanks to all for your responses. I am leaning toward keeping, restoring and enjoying them. I'm hoping to do it sooner rather than later so I can enjoy them as long as possible - if they eventually have to go, so be it. I have yet to hear anything near 10K that sounds better to my ears. Really, I haven't heard anything I like better, but I haven't gotten to any shows. What I can hear at the local dealers are Wilsons and Maggies - both very good, better at some things I imagine, but they don't connect me to the music like the Divas, at least not as I have heard them. The solid state amp in the picture has been sold (yesterday unless the deal falls through) If I can sell a few other items and save for a bit, it should be possible. Thanks again for your thoughts.


Happy Listening!

 

RE: Apogees and ethics - comments, posted on February 5, 2012 at 12:04:23
DrChaos
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The Apogee Diva is the best sound I've ever heard.

 

RE: Apogees and ethics - comments, posted on February 5, 2012 at 15:28:13
josh358
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Have you ever heard the Grand?

 

RE: Apogees and ethics - comments, posted on February 5, 2012 at 15:36:32
jazzbeat
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You will hear a difference. I made the change from Apogee Cals to Eminent
Technologies LFt8 thinking I would not miss much but in reality I do. The
Eminents while quite nice at moderate to higher listening levels do not match the lower level detail and range that the Apogee speaker has. I tend
to believe this is also true with the Magnepan as well. ( I have owned
MMG, 1.6.3.6 maggie and Eminent Tech lft8 , and Eminent Tech lft6 over the
years). The apogee has been commented on many times of having little
dynamic compression at low to fairly high levels IMO. This has been noted
by many and tend to agree. I am sure the 3.7 Maggie you talk of as well
as other models can sound just fine but my experience was one of sudden
lack of dynamics. The apogee due to a much loser diaphragm give the
sound field a more realistic dynamic range. The construction using a
tigher diaphram in the Magnepan and Eminent Technology limits the
displacement and range of dynamics compared to this.
If I had the choice I would stick with the Apps..

Just my 2 cents..

 

If you are determined to sell, I'd look for a local buyer first..., posted on February 6, 2012 at 08:56:16
David S.
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Why not test the local market & find out if someone nearby (who can demo the speakers in person & transport them home) might give you a good price for them?

No matter what condition they are in and no matter HOW well packed, shipping something like this will always be a gamble...

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 09:57:23
acroy
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I think the first paragraph is your for-sale ad! Full disclosure, the fact you're a discerning listener, etc. Don't fix them then buy them. You may actually get a premium for original stock configuration.

But my first choise would be, KEEEEP THEM. If you sell, you'll have seller's remorse within a few weeks I suspect. Nice as the 3.7's are, they are not Divas. Many of us aspire to own Diva's ....

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 10:59:58
josh358
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There's a pair up on Audiogon now, though at $6000 it seems a bit pricey for one that hasn't been rebuilt (but has no buzzes, according to the ad).

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 11:10:32
JLindborg
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Posts: 976
Location: Uppsala
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I have just one thing to say...
DON'T sell them!
You will regret it dearly.

The were and still are one of the finest speakers ever made.
I have the small brother Duetta II that is up for membrane and ribbon replacement and I will not sell them. All because I will not find a better speaker in a wide price range.

If I had the opportunity to grab a faulty pair of Diva's, I would. But that's me. hehe


The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 16:34:32
DrChaos
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Joined: July 13, 2009

No, i'm not worthy.

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 16:50:44
josh358
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I gather not many have, since only 25 were made. I'm curious how the compare to the Diva . . .

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 17:13:31
TitaniumTroy
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I always thought the Apogee's were they best looking of all full range planer's. Besides dynamics
, what did the Apogee's do better than say Maggie's? What do Maggies do better than Appogee
besides being easier to drive?

 

RE: Apogees and ethics - comments, posted on February 6, 2012 at 18:11:05
josh358
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Depends on the Apogee, and the Maggie. Apogees tend to have more bass extension for a given size, with a big resonance peak low down. The big ones can as you said have better dynamics, achieving in some cases very high SPL's. Efficiency of the earlier ones can be lower and one model was almost impossible to drive because of its 1 ohm midrange impedance. The midrange ribbon can ring less and be more linear/transparent and better at low levels than a Maggie midrange, but in some cases anyway can have a metallic twang like a true ribbon tweeter. The midrange ribbon can start twisting at very high SPL's. The true ribbon Maggies have better highs, particularly than the smaller Apogees with the combined midrange/HF ribbon (but then that's not really a fair comparison, since the smaller Maggies have quasi ribbon tweeters).

There were many models in both lines so the generalizations can only go so far, you can't really compare an MMG with a Grand (well, you can, but to little avail). Some Apogees and Maggies have a downtilted response, for example, and some don't, some use first order crossovers, the Grand is a four way with two 15" dynamic woofers, etc.

 

PS, posted on February 6, 2012 at 18:51:07
josh358
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Here's a comparison someone made:

"I owned the Studio Grands powered by a pair of Krell 300S, I sold them in fear of never being able to get support in the event something broke.

"I now use a pair of Magnapan 3.6 powered by Audio research Ref 300 MkII.

"The Apogees were POWERFUL, delicate and involving. They were a complete nightmare to setup - just when you thought you had them placed in their optimum place, you would move them a 1/4 of an inch and they would sound completely different. I got tired of wondering if I had the best placement.

"The Magnapans sound better in some ways - maybe more relaxed and musical - but they lack the authority of the Apogee's."

Of course, that's just two specific models.

 

RE: Apogees and ethics - comments, posted on February 7, 2012 at 13:50:55
Satie
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While all the drawbacks of driving and positioning the Apogees (any model) - Once set up and driven by an appropriate setup - e.g. Classe DR3VHC and a big Krell KSA/KMA on the bass, the Apogees are majestic, dynamic, scarry real, and once you are done wincing at the nails on blackboard low treble torsioning distortion on high powered peaks, you realize how much the rest of it is just so amazing.

Perhaps the Graz altered drivers finally have it all sorted out, but whether they do or don't, the Apogees do more "right" than anything else I have heard. And I never got to hear a pair at their best.

I did hear a mini grand, and it was very impressive. Davy had a Stage but was not happy with it because of the bad torsioning problem at high volume as the ca. 2khz distortion was very much a problem.

 

RE: Apogees and ethics - comments, posted on February 7, 2012 at 20:14:55
josh358
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I read somewhere that the torsioning is caused by air leakage at the sides of the diaphragm, I assume that creates eddy currents which lead to chaotic behavior. I know from the Apogee patent that they varied the pitch of the corrugations to maintain more stiffness. I'm wondering if there isn't a way to maintain laminar flow at high velocities, or, barring that, to better damp the oscillations electrically. Or what about using two 1" ribbons in a single magnet assembly, separated by a thin divider, rather than one 2" one? I gather narrower ribbons are less subject to torsioning. Each ribbon would be in a laterally asymmetric B field, but you can apparently get pretty good field uniformity with finite element analysis.

Or maybe Graz fixed the problem after all. :-)

 

RE: Apogees and ethics - comments, posted on February 8, 2012 at 03:36:49
Satie
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I think the solution is a stronger magnet in a deeper well or damping with connections to the frame. The thin tweeters have less of the torsioning problem but I don't think you can get the equivalent midrange from a pair of 1" ribbons in the same gap as you would from a 2" single piece ribbon. You are introducing more dipole cancellation and differential movement of the ribbons

The main point is keeping the thinner gauge ribbons out of the lower freq.

 

RE: Apogees and ethics - comments, posted on February 8, 2012 at 05:39:59
josh358
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I noticed that the original Apogee patent specifies foam at the ribbon edges. But that doesn't seem to be standard practice.

I can see that a deeper well could help, but presumably at the cost of worse cavity resonance and diffraction problems.

Stronger magnets make sense. I gather that neo magnets are incredibly expensive right now, though I imagine they'll be coming down some as that new rare earth mine comes on line.

These people are using multiple ribbons in their woofers:

http://www.traudio.com/tr-mobian

 

RE: Apogees and ethics - comments, posted on February 10, 2012 at 09:53:28
The Apogee situation is very interesting. Unfortunately, there's no semi-affordable (and convenient) way to repair buzzing Apogee speakers. I suspect all of them are buzzing in one form or another at this point in time.

You could cut your losses and sell them.....but I think I would hang onto them.....unless you need the money. The future is unclear and a viable repair procedure may emerge sometime in the future to revive these. Barring that, Apogee's are dinosaurs.....they're just not extinct yet.

Back when I purchased mine in 1986, they were semi-affordable, even for a person who had limited disposable income. Not now. Currently, they're very high-dollar, either to repair or purchase new. I believe the repair facilities (very limited geographically) are providing a service that's not overpriced, considering the labor required, but it's still expensive relative to the initial cost and other alternatives.

There is no GOOD solution for the many Apogee owners.....at this point in time. :(

Cheers,

Dave.

 

RE: Apogees and ethics - comments, posted on February 10, 2012 at 11:05:28
Satie
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I am not saying that a multiple ribbon bass is not possible just that it is far less efficient and can be subject to more torsioning. The positive is that you dont have transverse bending wave imd and can 1/2 way XO wire them to do mids coaxially, again note that they kept the tweeter separate rather than mount it centrally in the multiribbon bass/mid.

Magnepan uses soft silicone polymer beads to dampen it tweeters so they don't torsion at high volume but just compress. The Apogee idea of using a foam turned out to be a problem since their foams, that are used on the larger drivers, fall apart over time and introduce a buzz that is an inherent resonance of the driver. BG use foam to dampen their PDR models of the neo8 and neo3. I don't know whether they use foam anywhere else, but suspect they would.

In my setup there is a redone tweeter and an older one that was redone in the 90s and has lost all its beading. The point is that the tweeter sounds great so long as it does not carry much output below 2khz. If you cross steeply at 2khz, you will not have much torsioning with or without the beading, but I cross 1st order at 10khz so it is -16db at 2khz and -22 db at 1khz - good enough so that I never have a problem at my listening volumes. I know I get some torsional distortion on very high peaks, but you only know it after the peak when you notice that the ringing in your ears feels like it is at the wrong frequencies - the ringing sounds metallic.

I would not hold my breath on much cheaper neo prices, the demand just keeps rising for automotive electric motors.

 

RE: Apogees and ethics - comments, posted on February 10, 2012 at 12:09:43
josh358
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Some other advantages of top/bottom ribbon configurations I think of include the fact that the fundamental resonance is so low, that the field is more linear as a function of excursion, that the front wave can be unimpeded (though it seems that a magnetic circuit across the back is needed to avoid an efficiency loss of c. 40%), that it has more effective displacement since it dishes only vertically and not laterally, and that aluminum can be used without a plastic diaphgram -- though this presents its own set of problems such as impedance and I've heard varying opinions, some say they're comparable overall, the Transmission Audio web site says it causes stored energy and other problems (but then, they make metal ribbons). I gather they segmented their bass because it's impossible to make a full-width ribbon driver that goes below maybe 250 Hz, because of the impracticality of producing a field across a gap greater than 3". I don't know how this speaker or the all-ribbon designs from Transmission Audio sound since I haven't heard any descriptions, but I suspect the main drawback is cost -- both the cost of multiple large neodynium magnets, and of direct-drive amplifiers necessary because of the limitations of transformers at low frequencies. This has to be a very expensive speaker.

Magnepan uses edge damping as well, not sure what material they use but I've wondered if it deteriorates with time.

I don't think you could get away with putting a ribbon tweeter in the middle of bass panels. I'm not sure about midrange, though. Apogee put ribbons in front of and near the sides of its 2" midrange ribbon in the Scintilla and it seems to work -- I've seen one person say he thinks he hears intermodulation, but no other complaints. And there are the side-by-side single-magnet 2"+1" Transmission audio ribbon assemblies that I mentioned in my email. Would the center be any worse? I'm not sure why Apogee put the Scintilla's tweeter ribbons on the sides, or ran the rear ribbons out of phase. Presumably they used a laterally symetrical arrangement for the same reasons one uses any symmetrical arrangement, to reduce crossover lobing and improve imaging specificity. But wide separation will give you lateral lobing, and running the rear ribbon out of phase will give you a rear wave suckout at the crossover point, as well as giving you a different, omnidirectional polar pattern (though separation > lambda sources tend to be directional, with lots of lobes, so maybe that isn't an issue). One though I had is that they put them out of phase to keep the backwave from stimulating resonances in the midrange ribbon -- since one tweeter moves forward as the other moves backwards, the net force on the midrange will be zero. Another is that with the primitive magnets of the time, they weren't able to achieve a high enough field strength in the center of the magnet assembly.

So I still don't know how well a center coaxial tweeter ribbon would work. In light of what Apogee did, I do think you'd probably want to run it in a separate section, rather than in front of/behind the midrange ribbon as I'd speculated the other day -- at least, I don't like the idea of that phase flip on the rear tweeter.

Getting back to the TR audio, I don't think anyone knows how to make a coaxial true ribbon that covers all three frequency bands, bass, mid, and treble. Even the coaxial quasi ribbon designs don't try to do that, the Wisdom only goes down to 80 Hz, ditto the central tweeter OEM version of the RD-75. I assume this is because the IM would be too high. But since localization below 300 Hz is less critical, I'd think you'd want to coax the mid and tweeter and not coax the bass and mid, since whatever you do you want the mid as close to the tweeter as possible, both for imaging and to reduce crossover lobes.

Regarding neodynium, you know far more about commodities than I do. I gather though that the runup in prices has to do with the Chinese monopoly and their restriction of exports to force electronics manufacturers to make their products in China, and that the first competing rare earth mine is about to come on line in IIRC the Phllippines, capable of supplying 15% of world production, with other mines, including the mothballed one in the United States, slated to join it in the years ahead. I'm hoping supply will move ahead of demand and push the price down, as happened with oil when conservation measures and new exploration broke the back of the OPEC cartel at the end of the energy crisis. But I don't have the impression it will happen overnight, and as I said, I don't know much about commodities and haven't looked into the issue, so have no sense of the supply/demand curve.

 

RE: Apogees and ethics - comments, posted on February 10, 2012 at 13:36:55
Satie
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As I pointed out, the BG eperience made me agnostic about pure corrugated Al and kapton or what have you backing. Given stronger magnets, the current capacity of the ribbon becomes a non-issue, leaving you with tensile strength and mass minimization. Al foil is not what you want for tensile strength, so minimum mass is actually achieved with polymer diaphragms once you have a threshold magnetic strength.

I think the Scintilla tweeter(s) are where they are for coaxial symmetry as an inversion of the MTM coax we keep discussing. Achieves the same goal, and with their high XO are going to produce the multiple lobing you speak of - which is a nearly as good way of getting a broad sweet spot and an approximation of good lobing.

I think the reversed backwave - making the tweeter a bipole - is a deliberate choice similar to what Nudell did in his IRS by sealing the backs of his EMITs and putting an extra set on the back of his speakers. Swans also do the same with their flagship, and a few DIYers have done so with their neo3 PDRs. Note also that Revel (a harman co.) do their back tweeters in bipole phasing. I don't really know how to weigh these against each other. I would assume that the results achievable in side by side and coax end up being similar. Later mids and tweeters were not made that way at Apogee. The TMT though, allows you to tap the magnetic flux near the sides where it can be stronger at the edge closer to the front (and back) of the magnet structure, by doubling up and placing at the edges, the tweeter ribbons can be made narrower and run at lower output per each - thus reducing the torsioning problems - which I think is the weakest point in the side by side Apogees.

I agree that you would prefer to have the tweeter away from the bass in order to get less IMD, but then, if you have a two way, you can still have physical isolation of the center tweeter from the flanking bass ribbons, That way you get your MTM. The tweeters would be in a dipole null so you should not have much of a problem with airborne imd.

Quite frankly, the bass freq need to carry so much energy that I would prefer to have even 150hz away from the mids, not to speak of real bass below 100hz. You so don't want them together in the same structure - definitely not on the same diaphragm.

 

RE: Apogees and ethics - comments, posted on February 10, 2012 at 16:01:09
josh358
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Agree that a polymer-backed ribbon can have lower mass than an all-aluminum one. But I thought you liked the sound of the Apogees better than the BG's? Or is that the top-bottom ribbon configuration rather than the material of the ribbon? (Wendell calls everything not foil a quasi-ribbon, and I guess since he invented the term he gets to -- but I still haven't come up with an unambiguous, unclumsy way to distinguish between the various varieties).

The problem with wide spacing of drivers is that not only do they become directional, but the lobes multiply until you have cauliflower pattern -- and the nulls go all the way down to zero, and in the listening area, too (though not necessarily the sweet spot). Perhaps the nulls at the frequencies covered by the tweeter are so narrow that they aren't perceptually significant? Certainly the broad quasi-ribbon tweeters exhibit similar lobing problems, but to a lesser degree, since they aren't 2" wide.

I know of some other speakers that use rear radiators as well. The idea is to maintain a polar response that's fairly constant with respect to frequency; in a conventional box, the bass is omnidirectional, the highs are cardioid, and that reduces the sense of spaciousness. So I understand why Apogee used the rear ribbons, just not why they drove them out-of-phase with the midrange backwave, creating a suckout at the crossover point. Or rather, I suspect as I said that it had to do with their desire to avoid triggering sympathetic resonances in the midrange ribbon, had the front and rear tweeters been driven in phase it would have done that, but with the two out of phase, the forces on the midrange ribbon would cancel. I'm not sure whether Arnie Nudell ran the rear EMIT's in or out of phase with the front ones, but there were fewer of them and as I recall, he aimed for a cardioid pattern because he found it imaged better. Which would mean they were phased as bipoles, but at a lower SPL (which they likely were because there are fewer of them than there are on the front).

Hadn't thought about the fact that the tweeters could be narrower, though really, the Magnepan ribbons are 1/4" and go down to 3000 Hz, and the Apogees are four times as thick, so would the Apogee tweeters have a torsion problem? I was speculating on the flux strength, Apogee had to work with magnets of limited strength, which according to I think Graz is the reason for the low impedance of some early Apogees -- they needed the current to get reasonable efficiency. Not a problem anymore.

I don't think in an MTM arrangement you'd get a dipole null at the tweeter without some kind of relief port on either side of the tweeter, not until the out-of-phase wave had traveled around the barrier, anyway, and that doesn't really happen at the speaker itself because I assume the waves haven't diffracted fully, it seems they don't until you're a couple of meters out. If you left enough space to make dipole nulls, you'd destroy the efficiency of your midrange drivers and I think couldn't use a single magnet assembly. Plus you'd start to get lobing on the mids, you really want to keep the midrange drivers very close together so they operate as one.

With woofers I suppose you could do a W-M-T-M-W arrangement, but below 80 Hz there isn't much reason to and if you left enough room for dipole cancellation at the center you'd halve your effective baffle size.

I think you're right about wanting to keep the bass freqs away from the mids. Lobing isn't a problem at those frequencies, so you only have to deal with lateral image spread -- not ideal, but not too terrible, as those things go.

 

RE: Apogees and ethics - comments, posted on February 11, 2012 at 14:07:04
Satie
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I am not sure that I like the Apogees in the mids and highs more than I like the combination of Neo8s and Maggie ribbon any more. I don't feel that I am losing much by crossing at 250hz, and I very much like not having the torsion screech distraction, even if it is only occasional.

I recently changed the midrange XO to allow a narrower range of HP adjustment, and a more appropriate level adjustment range, and bypassed the HP's Sonicap 1 cap with a foil cap, which changed the perceived FR and smoothed out a bit of grain that makes things that much better. So I am now reworking the tweeter/mid XO to make use of the neo8s further up with less lobing. In the process, I am listening to the mids alone, the bass + mids, Bass + tweeter. Taking your comment in mind about shelving down the treble output rather than tilting up I am experimenting with lower tweeter levels, which effectively raise the XO. There is an interesting level match I reached last night which gives a really interesting improvement in image saturation and air on Billie Holiday's last Columbia recordings, which were two mike stereo from 1958. I need to try this with more recordings and see over what range of adjustments this effect can be maintained.
side note - In order to make the adjustments easier, I am going directly off the DAC so that I don't have to adjust for the tube preamps sensitivity to load impedance - which changes with XO adjustment.

There is one point on BGs + mag ribbon vs. apogees, in that I did most of my Apogee listening at a dealer's where driving electronics were routinely an order of magnitude more costly. Levinson amps and Symphonic line Pre are hard to beat not to speak of the heavy turntables and CD players that each cost more than my entire investment in audio. My home setup has never been that strong on source components, no matter how tweaked, and my amplification, though good or very good, is not "as goo as it gets" as was that at the dealer's. The only thing where I may have the upper hand in my systemm is that the DAC is newer - though the output stage is not discrete but Michaelson's best trickery with 4 dual opamps of the cheap veriety 2 duals per channel - gain and buffer - same as in his better DACs and preamps, but not his top of the line discrete products. Though he does use the same buffer design and op amps for even his terrific sounding trivista DAC (his mini tube nuvistors and trivistors were buffered with op amps).
So bottom line, I don't know anymore whether the Apogees would win out on a level playing field vs bgs+mag ribbon.

Re WTW ot MTM idea, where I was thinking the T would be in a physically separate frame, are you sure there would not be a null? do you really need that much of a gap? I get noticeable dipole cancelation with the space between the bass panels and mid/tweeter frame opened to as little as 1/4", and much more at 1/2" - perceived as a drop in the low end extension of the array. I use a strip of tape to keep the gap closed (touching only the mid/tweet panel).

Re bipole tweeters - I know Nudell did it bipole - I guess for the same reason you quoted.

The Apogee tweeters did have a torsion problem. In my listening it was the only flaw in them that was not addressable by a change in ancilliaries or a trivial mod of the XO or drivers. The way to address it was to raise the XO by an octave or more - leaving the mids to cover another octave - which they did not do that well due to their weight and width, or to sharpen the XO to 3rd or 4th order - which you can do today digitally without phase issues, but not back then.

I see your point on the design considerations forcing the gap to be small enough so there is no null.

 

RE: Apogees and ethics - comments, posted on February 12, 2012 at 16:19:36
josh358
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Good about the Neo's, since the chance I'll have time to build a midrange ribbon is somewhere between nil and zip. :-)

I'd think that 250 Hz is a pretty ideal crossover point for the Tympanis. AFAIK, there still isn't anything that can beat Tympani midbass. Sure, you're going to get a bit of lateral smearing from the offset, but to my ears smearing is pretty minor at those frequencies. Of course, I haven't heard the Neo 10, but (besides their cost) I remain a bit suspicious of their beaming above 2 kHz. I think I'd rather compromise at 250 Hz than in the midrange.

(BTW, did you know that the Neo 10's use the force of the magnets to bow the perforated metal to accomodate the diaphragm? Just read the patent. They also have pleats on either side of the diaphragm to reduce stresses and improve damping. Also learned something about the failure mechanism of overdriven planars -- apparently, heat leads to differential expansion between the film and the foil, and when combined with large mechanical stresses, the diaphragm can wrinkle, delamination can occur, and conductors can break.)

One of the changes they made in the Tympani IVa was to give it a down-tilted response. I don't think there's a right or wrong here -- it seems that works recorded in a large hall need the downtilt, works recorded in a smaller space don't. But with so many recordings hyped in the highs, a downtilt can't hurt. I didn't know that Billie Holliday made any stereo recordings.

I have the same problem you do with my memories of speakers, though these days, it's more likely to be that amps back then were underpowered and colored. Forex, how much of the magical imagining I remember from the IRS V had to do with the speakers themselves, and how much to do with the big Conrad-Johnsons? And how much with the acoustics? I'll never know.

Not sure about how much of a gap you'd need. I looked up the formula for acoustic impedance of a slit, but realized I didn't know what SPL the ribbon could tolerate so didn't bother running the numbers. It depends not just on the width of the slit, but on the depth of the baffle, and by the time you'd plugged in all the numbers and figured out ribbon resonances and coupling you could have just tried it 20 times over.

BTW, I found a guy (Valvetude) who's running his homebrew 0.75" neo ribbons down to 200 Hz. He gets +/-0.125" excursion from them and says he can play them at deafening levels without distortion. Assuming you can get a sufficiently uniform field, I wonder what the practical limit on this is -- ribbon fatigue? The reason I wonder is that I assume narrower ribbons are less susceptible to torsion, and of course they also have lower mass, better dispersion, and more uniform field strength.

 

RE: Apogees and ethics - comments, posted on February 15, 2012 at 00:09:44
Satie
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I remember following Vavetude's project as he was posting it. You need to take into consideration his heroic effort with giant magnet structure and fine tuning of every component, surface, location. It is something that you would expect to cost a few thousand a piece and something like most of a Genesis system once you add the appropriate woofers to complement it.

I did not know that the Neo 10 uses the magnets to form the shape of the magnet boards. Very cool idea. Yes, I was aware of the heat failure mechanism. That differs from mylar, which just melts.

I think 250 hz is an ok spot rather than perfect. The ideal would be more like 150-200 depending on how solid the structure holding the mids is.

I have a rather good memory of what I heard, since I got to hear the Centaurs and Slants many times, and got exposure to the Stage and its derivatives sufficient to get a permanent feel for it.

I can say that the Apogees are still somewhat more dynamic sounding than the Neo8 - probably because the ribbons are loose and not stretched as much as the Neo's. I think that limits their output some when you go beyond a certain rather high volume, they compress a little. But otherwise, I think they are just more refined and texturally right. I have heard my Neo8s with a variety of amps, so I have some idea of the sound of the array itself.

I am a little surprised that you can get a more correct imaging with the down tilted top end - as pointed out in the Sonus Faber Amati Futura review from Atkinson. Very interesting.

I guess we just leave the minimum gap size for dipole cancelation aside. From my experience it seems like 1/2" is already over the threshold in the 300 hz area.


 

RE: Apogees and ethics - comments, posted on February 15, 2012 at 07:34:25
josh358
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I gather that large Neodynium magnet assemblies are insanely expensive right now, I've seen some figures on DIY audio in the $1-$3 thousand range. (Though some have done quite well with factory seconds, etc.)

I'm not sure the Neo's are necessary for sound quality, for anything except the ultra-wide ribbons (and then you wouldn't necessarily need huge ones). The Neos give you great efficiency but as Wendell points out it's cheaper to buy a big amp. I read somewhere that stronger magnets give you lower distortion, but I'm not sure why that would be the case, I'd expect ribbons to be predominantly air damped and distortion to depend on the uniformity of the field rather than its strength, the precision of the air gaps, and the resonances in the ribbon. Am I missing something? Better electrical damping at low frequencies, perhaps?

Ditto Valetude's 250 pounds of steel, I gather he kept adding it until he eliminated most traces of saturation in FEMM but if you don't need the efficiency, I assume you wouldn't have to go that far.

I read last night that Linesource's 2" ribbons are crossed over at 80 Hz? With an 8-pole crossover.

I've heard it said that ribbons have an advantage in dynamics. I'm not sure why. I'd expect the planar-magnetic field to increase distortion at high excursions. I'm not sure about the compliance of the film, does it become nonlinear? Otherwise I'd expect it to store energy, as of course it does, but AFAIK that wouldn't cause compression. Maybe the ear, while it integrates over time to judge frequency response, interprets time smearing as a loss of dynamics or a change in timbre? I'm thinking back to analog synth days, and the effects of the ADSR envelope generators -- stored energy would have the effect of reducing attack and reducing decay, and both of those make substantial changes to timbre.

Do you remember approximately where John Atkinson said that about the Amati's FR and imaging? I just read the review, must have skipped over it (feeling guilty about doing this stuff right now when I should be getting to work).

 

RE: Apogees and ethics - comments, posted on February 15, 2012 at 08:20:46
JLindborg
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Well, one fact is and would be that a ribbon in its loose suspension does mostly have air as restriction and load.
Compare that to a membrane that is suspended and stretched!
The stretching in itself is a very strong force that directly affect dynamics as it is actually forced not to move but still does due to flexing in material.
As a perfect example of this is electrostats that really needs a pretty strong suspension that actually forces the membrane to its stationary place between the stators.
This because it would otherwise automatically get attracted to one of the stators and get stuck.
The solution to this is make the membrane area larger to compensate for the lack of motion.
This of course is mainly true in the bass region where large excursion is needed.


The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 15, 2012 at 13:07:39
Satie
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You are absolutely right, the mitigating factor is that the membrane becomes more flexible over short time periods as stretching increases temperature in the membrane and reduces resistance to elongation. It is noticeable on the Neo8s as the detail retrieval and dynamic swings after a very loud passage improve and then deteriorate slightly if no further loud passages follow. I should point out that when I use the modified Nuforce class D amps, the dynamics are better and the effect is even more pronounced but dynamics are better overall. I think this better dynamic presentation has something to do with the driver being within the feedback loop since the little amps get way hotter than the energy they are supposed to deliver would imply. Which indicates some sort of electric damping, probably of the return tension on the membranes.

The membrane material in the Neo8 is rather stiff and has little elongation and is responsible for the sheer drop of the bass response as stretch limits on the membrane are approached. It is alot more like kevlar than it is like rubber.

There is definitely energy storage and compression going on with the BGs. But it is not that great so long as you keep bass freq out of it.

The big deal is that the bigger the magnets the smaller the effect of air damping on dynamics. Remember that you have the ribbon sittin in a narrow slot and pushing air into and out of the slot with turbulent air flow and at the kinds of displacements that Valvetude reports that is going to play into damping - and the more magnet you have the better you are able to overcome the air resistance. While you can get "cheap power" to do it instead of expensive magnets, the quality of the "cheap power" in something as revealing as a ribbon is far more significant a cost than it would be on a bass driver.
Torsion is also magnetically/electrically damped, though weakly, which is why that is a limiting factor in ribbons. The torsioning is caused by greater air resistance to motion by the edges of the slot. Once an asymetry initiates the torsion it will not go away till the ribbon's vibration is much reduced in amplitude.

Re Atkinson - it is what he is implying in comparing to the Quads.
http://www.stereophile.com/content/quad-esl-63-loudspeaker-measurements
http://www.stereophile.com/content/quad-esl-989-electrostatic-loudspeaker-john-atkinson-may-2003

Also Iverson's review of the SF Guarneri stand mount speaker actually compares to the Quad ESLs.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 06:55:17
josh358
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On the other hand, the forces on an electrostatic are essentially limited by the breakdown voltage of air. So there's an upper limit on the force that can be applied to the diaphragm at a given stator spacing, which I think is about 1/10 that of a planar magnetic. Whereas in practice, the low frequency excursion of large planar magnetics seems to be limited by the position of the magnet assembly, which is determined by efficiency and magnet strength. They'll play until they slap the pole piece. So as far as I know, for a large planar, the limitation on LF output is imposed essentially by the cost of the magnets, and of a mechanical assembly of sufficient strength to accommodate them. For a smaller planar like the Neo's thermal damage could also be an issue, and also maybe distortion at large Xmax's caused by the non-uniform field. As far as I know, the compliance of these plastic films is a constant, so I'm not sure where dynamic compression would occur, unless it's a subjective consequence of rising non-linear distortion? And I wouldn't expect most of these concerns to apply at higher frequencies, where excursion is low.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 09:23:02
JLindborg
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What I was talking about was dynamics.
All You say is right when talking about output.
But dynamics are all about having a non restriction or as little as possible. And here a ribbon is unbeatable... except for maybe plasma. hehe

The restriction for a membrane will be exponential and therefore the dynamics will decrease exponentially.

Single ended or double pole piece are another discussion as it is mainly a linearity and efficiency one as such. But both will suffer from restriction from the suspension.


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RE: Apogees and ethics - comments, posted on February 16, 2012 at 10:41:28
josh358
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Why would it be nonlinear, though? I'd expect the deflection to be pretty linear until you get near the elastic limit. Which you don't want to do because you'll stretch or break the diaphragm.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 13:23:02
JLindborg
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What I mean to emphasize is that suspension equals compression and thus less dynamics.



The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 17:14:20
josh358
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Is it? I always assumed it was pretty close to Hooke's Law, that is, linear. In two dimensions, of course, with more compliance laterally than vertically.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 17:24:02
josh358
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While it's true that larger magnets increase electrical damping, air damping so predominates at the higher frequencies at which ribbons operate that I'm not sure how much of an effect electrical damping has, even with strong magnets. More on torsion and edge-gap distortion perhaps, since when that occurs the air is turbulent. But as I think about it, I'm not even sure if it has much of an effect there. Amplifier damping can be compromised by the crossover network, which would leave only self-damping from eddy currents. Since ribbon resonances are below the crossover point, the diaphragm could literally be left to twist in the wind. Another consideration is that the amplifier can only damp the ribbon as a whole. Since torsion is symmetrical, it may not be much affected by amplifier damping at all. Again, you're back to eddy currents. Which would however be stronger in a stronger B field.

 

RE: Apogees and ethics - comments, posted on February 16, 2012 at 21:33:33
JLindborg
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"Is it? I always assumed it was pretty close to Hooke's Law, that is, linear. In two dimensions, of course, with more compliance laterally than vertically. "

Not really if You look at the function of a suspended membrane witch is not a spring.
You could though try to integrate Hooke's law into the calculation of air volume that is very non linear for a suspended membrane.

You probably understand me now? :)


The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 17, 2012 at 03:45:05
Satie
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The idea is that larger magnets and thicker tweeters end up with larger relative magnetic forces vs. air resistance and damping. Thus less compression.

In the torsioning case, I know from listening and from the basic physics of it that it can't be damped effectively, only prevented - as magnepan do with their little beads - which allows them to have no torsioning and no significant lengthwise resonance.

One of my tweeters is loose, while the other is nice and tight and beaded. The loose one torsions when playing signficant output below 5 khz, but performs just fine with the 10khz XO. The higher frequencies don't seem to be affected by the torsioning when playing at lower XO, but the 2-3 khz range becomes rough and screechy like the Apogees can sound.

 

RE: Apogees and ethics - comments, posted on February 17, 2012 at 09:23:07
JLindborg
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Not any measurements done by myself but from the book "Ribbon Loudspeakers Theory and Construction" ISBN: 1-882580-24-X.
Corrugated ribbon have larger/more THD then an uncorrugated ribbon in 3kHz and 10kHz except for 1kHz where the uncorrugated ribbon has slightly higher THD.
IMD is higher for corrugated in 2&5kHz and slightly higher for an uncorrugated ribbon in 5&7kHz.

Interesting I would think.



The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 17, 2012 at 19:39:10
josh358
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I was looking for that book a few days ago, the only copy I could find was going for more than $300. But I saw the web page that had that info. I wonder whether an uncorrugated ribbon would be more susceptible to torsion. Also, whether it would allow sufficient displacement to play at high amplitudes at the lower end of its frequency range.

 

RE: Apogees and ethics - comments, posted on February 17, 2012 at 19:49:55
josh358
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Once it starts oscillating the damping would already have proved insufficient, so it makes sense that it wouldn't stop while still driven. But I assume that if you could achieve critical damping, you wouldn't get the torsional oscillation in the first place.

I gather the Apogee ribbons had foam supports to achieve the same thing as Magenpan's adhesive. But of course they still had the torsion problem, I assume due to the width of the ribbon.

 

RE: Apogees and ethics - comments, posted on February 17, 2012 at 22:11:51
JLindborg
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There are sadly no comparisons in those areas in the book.
But it mentions and shows a research of how a corrugated ribbon does behave as a uniformly moving piston, but has many modes imposed and torsional movement in, what they call 8th resonance mode, that would be 244Hz.





The one who succeeded was the one who didn't know it was impossible.

 

RE: Apogees and ethics - comments, posted on February 19, 2012 at 06:13:04
josh358
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Now that's really ineresting. Wish I could get hold of that book. I'm going to see if I can get it on interlibrary loan.

Meanwhile, I found the paper mentioned in the caption:

 

RE: Apogees and ethics - comments, posted on February 19, 2012 at 16:57:45
josh358
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Sure. The next question, then, is which distortion mechanism predominates at high excursions -- the nonlinear displacement, or the nonlinear magnetic field?

 

RE: Apogees and ethics - comments, posted on March 20, 2013 at 02:45:06
sots


 
how much are you selling the apogees for?

 

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