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Drivers for 811b's ?

westend

westend

Audiopile
I just picked up a pair of Altec 811-b's. This is a horn that I've been trying to use for a few years now. I had an orphan with an 806-8a but was never able to come up with another matching orphan. I finally got over that and scored a nice pair of 811's, locally, from an AK'er.
My interest in these goes back some 30+ years when I first heard them in an excellent system, augmented with various other drivers and, of course the bass from a pair of Altec woofers.
Since then, there has been a lot of discussion here and on other froums of the use of B&C, Selenium, and other compression drivers that perform better than the 806's and have some other desirable characteristics.
I would be interested to hear impressions of those using non-Altec drivers and those still using Altec for comparison.
I have a pair of AMT-1 tweeters to augment any high frequency rolloff and plenty of amps to bi-amp these soon-to-be-built speakers.
I will need to get some woofers for this set and am currently leaning toward JBL for that but that isn't cast in stone and would better be addressed in another thead. I thought I'd offer that in for recommendations just for the capability of the low end of this project.
 
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westend said:
I have a pair of AMT-1 tweeters to augment any high frequency rolloff and plenty of amps to bi-amp these soon-to-be-built speakers.
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You'll have difficulty integrating any external tweeter with 811B horns. In working with Valencias, we were only able to do it by mounting a small tweeter within the horn mouth itself, and even that was not entriely successful. It's all documented in the "Babies" thread over on LHF:

http://audioheritage.org/vbulletin/showthread.php?t=14690

And also a condensed version with a different focus here on AK:

http://audiokarma.org/forums/showthread.php?t=106759

Since 811B will support VHF (albeit with some vertical beaming,) using a compression driver which provides the requisite extension sidesteps those issues. We used BMS 4550 or 4552nd to accomplish that.

Altec 806A will get to 14 kHz using active CD compensation, but the larger-magnet Altecs with tangerine phase plugs do a better job of it, and can be compensated passively, as with the Model 19 crossover. Thus far, however, I have not been impressed with their uniformity, which is essential for good imaging.

http://audiokarma.org/forums/showthread.php?t=141129

I have successfully run 811Bs with BMS drivers using either JBL 2235H or LE14H-3 woofers.

There is presently an AK group buy for the premium BMS 4552nd drivers underway over in Dollars and Sense:

http://audiokarma.org/forums/showthread.php?t=143723
 
Zilch said:
Altec 806A will get to 14 kHz using active CD compensation, but the larger-magnet Altecs with tangeringe phase plugs do a better job of it, and can be compensated passively, as with the Model 19 crossover. Thus far, however, I have not been impressed with their uniformity, which is essential for good imaging.
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Speaking of these larger mag drivers with the tangering plug... .I can't speak higly enough, or get enough of listening to my 902-8b drivers... Well worth the cost in my eyes.. .er ears...
 
Zilch, I think we're up to 6 of the 4552ND's at this point plus the pair of other drivers you want. I'm contacting Assistance next week to check if they'll give us the dozen price for less, I'd like to show these off at the AK Fest. Dave.
 
Westend---I'm very keen on Altec and GPA 902s. They're very smooth with excellent upper mids and nice highs, VERY nice sound.

gpa-as.jpg
 
Thanks for the responses, gentlemen. If I narrow my choices to the 902's and the BMS 4552's are there any inherent weaknesses in these drivers or do either need special crossover complexities. I would like to stay as close to crossover simplicity as possible.
 
Here's the 811b crossed over at 1600 hz with 3rd order crossover and some high end compensation. This is hard to beat.

The driver is the Eminence PSD2002. This is from Wayne Parham's www.pispeakers.com site. The crossover is the one used in his 4 pi Theatre design.

PSD2002_on_Altec811_with_pi_1K6a008db_crossover_take1.gif
 
The Altecs work best with compensation; EQ that pushes down the mids and thereby extends the highs, it's simple and several circuits can be found online. I seem to recall the BMS has a high frequency resonance that needs notching but I'm not sure.
 
BMS whips it good:

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That's two different BMS drivers on Altec Model 19 crossovers plus UHF notch there.

Best I could get with a sample GPA refurbished 802-8G:

attachment.php
 
Yeah, if you like extending the highs with what appears a resonance, does that show as such on a waterfall? Some people like that kind of thing and others prefer a smooth rolloff.

I don't know how the BMS sounds and I do know how the 902 sounds, I like it. Is it your opinion the BMS sounds better than the 902? How about the upper mids of the BMS, as lifelike as the 902 or JBL 2420 in your opinion?
 
As you know, Tom, I mostly stay out of the "How's it sound" thing, and I've never seen or heard an Altec 902 driver, much less a GPA one.

Do you have measurements on yours to post yet?

Steve O recently observed that the BMS sounded very much like the Altec midrange in reporting on his BMS Carmel development project.

Tom Danley has also reported favorably with respect to how BMS sounds.

Regarding resonance, here's four BMS drivers on a different waveguide:

attachment.php


Jackgiff built two of those particular drivers into his Santanas, and his similar measurement results for those systems are posted elsewhere on this forum.

I'm gonna guess they image pretty well, also. :yes:

For comparison, here's GPA-refurb 802-8G uniformity on 811B:

attachment.php


Jump aboard the group buy, Tom, and we can have a lively thread comparing all of our respective findings here.... :thmbsp:

Edit: Here's CBS Labs measurement of Model 19 from 30 years ago, 802-8G, presumbably. Does it look like what I measured them as immediately above?

attachment.php


Do we have reason to believe 902s perform differently?
 
I've taken no measurements of the 902s, either Altec or GPA and will not for some time, perhaps this summer I'll have time to properly delve into the measurement thing. Measurements I took years ago with a Pansonic RTA and calibrated mic of a 902 on a 511 showed flat response out to 16khz, as high as the RTAs readout went. The RTA had fat "slices", not much detail.

The BMS's very extended response seems to be in contradiction of the roll-off said to be inherant with compression drivers, that and the spike would seem to indicate the presence of a resonance. However there are so many horns and so many possible frequency responses with them that frequency response curves alone may not be adequate to show if such a resonance exists, thus my question as to whether you're run waterfalls.

Group buy? Nah, next time I get compression drivers I'm getting JBL 2435s, in fact a pal wants to give me a pair but I don't have 1.5" horns handy yet. Here's the guy's system; 2435s on LaCleach horns for upper mids on up, Supravox field-coil drivers on Oris horns for mids, Eminence 15 direct radiators for bass and a tapped horn sub. Sounds pretty damned good.

stuff043.jpg
 
dgwojo said:
Zilch, I think we're up to 6 of the 4552ND's at this point plus the pair of other drivers you want. I'm contacting Assistance next week to check if they'll give us the dozen price for less, I'd like to show these off at the AK Fest. Dave.
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Possibly 8 as of this morning with another member from Michigan, Dave. :yes:
 
Somebody send me some GPA 902s to measure, and we'll settle it. Frankly, I'm dismayed the curves aren't published. It's just silly.

I know, I know, there's more to it than just the measurements.

[I'll listen, too, I PROMISE.... :p: ]
 
I have used the Eminence PSD2002's that Paul C posted about. While the BMS drivers measure better you can't even begin to get them for the cost of the Eminence. I like the sound of them just fine. An audible improvement in response from the 808-8a w/Radian 1228 phragms. The Seleniums that have been getting some publicity lately look attractive for the money as well. At their price I can afford to just get em and try em.
 
Send me something decent I can mount up to my 511's to use in the mean time, and I'll send you my 902-8b's... I'd like to know what they do, but I would want to see the numbers mounted to 511's so i know what I'm hearing...
 
I wouldn't be shipping my stuff across the country just for a test. Money maybe but then it wouldn't be mine anymore. Stick with what you have until you can afford to try something else.

There are a number of usable options available from not so expensive to expensive.
 
I have tested Altec drivers from California, Alaska, Arizona, and New York, Mac.

Properly packaged, it's just not a problem sending them back and forth.... :thmbsp:
 
Zilch said:
I have tested Altec drivers from Alaska, Phoenix, and New York, Mac.

Properly packaged, it's just not a problem.... :thmbsp:
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I'm sure it isn't a problem. All I'm saying is that "I wouldn't ship anything, anywhere, unless it was necessary". Sometimes ya just gotta protect against the downside.
 
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