Look at my new babies...Altec 846Bs w/EV Tweeters!

[VTUBE6]

Hey guys, was just telling Zilch I just returned from a 3 week trip. I asked a friend to build the comp. networks for me while I was gone, but he let me down. That's okay, I still like him. Anyway, he did let me borrow a pair of super tweeters (modified Raven ribbons) to play with. They are 95db efficient and are crossed at 14K. They play from 14-40K. I know, that may seem ridiculous, but I heard them on some other speakers that had really good tweeters on them and these things took the whole "air" thing to another level.

I just hooked them up to my uncomp'ed BMS drivers and upon initial listening....no magic. Could be the difference in efficiency or could be the BMS driver overwhelming everything else. :dont-know Who knows, but I'll keep playing and will provide an update when I get the comp networks and upgraded caps in the speakers. Cheers!

[Zilch]

Along with his drivers for measurement, Gary sent a vintage Altec "light" 23744 diaphragm. I loaded it into an Altec 802D motor today, and ran that in comparision to one of each of the other driver types on hand using Model 19's N1201-8A crossover, adjusting each for maximally flat:

1) Compared to Scott's 806A (yes, wrong impedance, but not all that apparent,) and Gary's GPA-refurbished 802-8G

2) Compared to BMS 4550 and 4552nd

3) All of them at once

4) Add Radian in 804A, black.

[If I had M19s, I believe I know what I'd be spending $300 to try.... ]

[Tom Brennan]

Zilch---I've seen several curves from other experimenters that show better response than you're getting.

Here's an uneqalized curve I got several years ago on an RTA. The mic was a calibrated Panasonic and the curve was taken at my listening position and on-axis of the speakers which were toed in. The slices are coarse but show the trend of extension pretty well.

This was an A5 bassbin, 902 on 511 horn and twin JBL 4648s bassbins augmenting below 100hz. Crossover at 500hz with a DOD. That's +-5db 25 hz to 16khz. At the listening position, not bad.

[Zilch]

Thanks, Tom.

I'm actually showing BETTER response than you from the Altecs, +/- 2.5 dB, using Gary's drivers on M19 crossover, out to 14 kHz.

Just to confirm, I'm looking back at the initial measurements from nearly two months ago, and it looks like I'm getting reasonably repeatable results:

http://audioheritage.org/vbulletin/s...762#post160762

http://audioheritage.org/vbulletin/s...635#post160635

There's no denying the M19 crossover levels the major response anomaly with compensation, and I'm not going to quibble about whether or not the HF extension is adequate at 14 vs. 16 kHz. The problem is that the response is not smooth by comparison, and that's clearly shown in your results as well. Look again at how the HF is now performing in Jack's Valencias:

http://audioheritage.org/vbulletin/s...133#post167133

The Radians would probably do better than Altec diaphragms overall, particularly with the tangerine phase plug, but they clearly suffer the same difficulty in response smoothness. While it's risky to conclude anything from just these single samples, the "light" diaphragm appears to do better in the high end, but gives it up lower down.

Jack's running both the BMS alone and the Altec driver with tweeter, so I expect that if anything significant about the sonic character of the system is lost in the upgrade, he'll be telling us so. I certainly don't hear anything like that; if anybody hates the sound of mylar, it's not because the response isn't smooth....

[louped garouv]

http://www.audioheritage.org/vbullet...4&postcount=41


has anyone ever gotten a chance to measure the prototype Altec Be 'phragms?

[moldyoldy]

... the "light" diaphragm appears to do better in the high end, but gives it up lower down....

Apparrently by design, as they were only used in >1K apps, a limited run of 802s (many of which went to M19s), and studio-bound Duplexes.

[Earl K]

Interesting turn of events ( & interpretations of FR plots )



I look at the above curve & "see" great possibilities to design something über pleasing to listen to . The end result ( after tweaking ) would likely require a biamped setup / to make up for the lost gain due to response "notching" . Pairing the 802/902 with a less efficient woofer (than the 416-8b ) is a possibiblity. Either the JBL ME150H or 2234H come to mind .

Notching Filtering
- I'd strap across the driver, a series LCR ( centered around 4100 hz ), dialing in a mild bit of notch ( @ 1.5 or 2.0 db ).
- The 7500 hz bump might get treated / OTOH, it may not / its' a 50/50 toss-up determined by listening impressions .
- The 12K to 13K bump would remain untouched .
- The 800 hz bloom might need to remain in place / all dependant on crossover filters meshing together , etc. .

- I know what Altecs' transducers are capable of ( esp. their engineered recipe for compression drivers ) , which is why I listen to them .




- The above plot of the BMS driver is remarkably flat .
- Unfortunately, without listening to this driver I can't tell from the plot much about its' resolving capabilities ( or distortion characteristics ) .
- Its' Mylar diaphragm may well be too dead/damped for my taste .
- It's unlikely that its' "sound" is too "live" based on my experience with the Mylar diaphragms found in B&C drivers ).


- Here's the official FR plot ( unsmoothed ) for the crowd pleasing 4345 / maybe someone should work out a way to "fix" this ( likely not going to happen given its' acceptance ). This plot would "look" a lot better with 1/6 octave "smoothing and "great" with 1/3 octave smoothing . A plot like this ( as well as Altecs' older stuff ) somewhat rely on the old adage that the typical listener is only capable of resolving a range as narrow as @ 1/3 octave , for plus or minus a couple of db .

[Zilch]

Notching Filtering
- I'd strap across the driver, a series LCR ( centered around 4100 hz ), dialing in a mild bit of notch ( @ 1.5 or 2.0 db ).
- The 7500 hz bump might get treated / OTOH, it may not / its' a 50/50 toss-up determined by listening impressions .
- The 12K to 13K bump would remain untouched .
- The 800 hz bloom might need to remain in place / all dependant on crossover filters meshing together , etc. .

- I know what Altecs' transducers are capable of ( esp. their engineered recipe for compression drivers ) , which is why I listen to them .

Yup, here's the pair of them, indicating there's enough commonality to work with:




However, I don't have that level of commitment or dedication to Altec drivers. If vintage aluminum were what I liked and wanted, I'd drill the mounting flanges and install LE85s, which are virtually "Plug 'n' play." Here's a pair of those, running uncompensated, as I recall, which would be much easier to "fix," and further afford the potential of enhanced response above 12 kHz, as in 4430. The notch at 16 kHz in the Altecs would be a deterrent, whereas the vintage JBLs have a reasonable slope to work with up there.



No way am I messing with 4345s other than to get past them....

- The above plot of the BMS driver is remarkably flat .
- Unfortunately, without listening to this driver I can't tell from the plot much about its' resolving capabilities ( or distortion characteristics ) .
- Its' Mylar diaphragm may well be too dead/damped for my taste .
- It's unlikely that its' "sound" is too "live" based on my experience with the Mylar diaphragms found in B&C drivers ).

I had them to work with because others here regarded them highly. It's all of $150 to try the premium 4552nd version....

[jackgiff]

Interesting turn of events ( & interpretations of FR plots )
- The above plot of the BMS driver is remarkably flat .
- Unfortunately, without listening to this driver I can't tell from the plot much about its' resolving capabilities ( or distortion characteristics ) .
- Its' Mylar diaphragm may well be too dead/damped for my taste .
- It's unlikely that its' "sound" is too "live" based on my experience with the Mylar diaphragms found in B&C drivers ).

Earl, I am sure my listening tastes are different than yours, and I am not a audio expert by any means, but I have listened to Valencias for 40 years. I have one pair with 4550's and one pair with 4552's. They both sound pretty darn good, and I have sold one pair of 806A's, and the other pair will be for sale soon. The BMS drivers with mylar diaphragms have very good definition and sound much cleaner than the 806A's they replaced. Of course, I have also replaced the crossovers with new homemade stuff, and with the RTA was able to get them working same as the N800F's they replaced.

I wish you were close enough to come and listen to them. I would like to have someone elses opinion of how they sound. My wife and I are both thrilled with them. They certainly don't sound dead to us.

Jack Gifford

[Zilch]

How are you going to know if you have actually accomplished that without a pair or 4345's on hand to compare them too??

EASY -- just beat any of the several systems that already beat THEM!!

[Life's too short to be messin' with 4-ways.... ]

[moldyoldy]

....[Life's too short to be messin' with 4-ways.... ]

Or is it that the BW's too wide to do it with 2....

[Zilch]

Or is it that the BW's too wide to do it with 2....

It's a conspiracy.

Just when I get close, they go and add another octave....

[moldyoldy]

It's a conspiracy...

Possibly, in the grand scheme...

But how much fun would it be if it were easy?

[Zilch]

So you already have a pair built and have used them to compare to the winners in your evaluations??

Well, I can never really be SURE 'til Bo and Speakerdave hear 'em....

[Storm]

Okay guys...

The speakers that started this thread are up for auction.

No, the tweeters are not included. I removed the tweeters and added an extra set of fresh foam in each speaker. I removed the wires as well.

http://cgi.ebay.com/ws/eBayISAPI.dll...2696&rd=1&rd=1

Take a look, if you want.

I am still amazed that one post about speakers could result in more than 50 pages of discussion. Incredible.

I will miss these speakers, but I know that I will thouroughly enjoy the 250TI's, just as much -- if not more.



-Storm