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

[Zilch]

Gary's 802-8Gs were remagged and new diaphragms (#34647) installed on 12/10/06 by GPA, and not used since.

Compare to Scott's 806As (middle) and my funky ol' LE85s (bottom).

Highpass @ 450 Hz.

Do Scott's drivers and LE85s measure the same as before?

http://audioheritage.org/vbulletin/s...&postcount=440

[DaveV]

Zilch,

The 802 plot isn't too inspiring and I'm thinking no wonder I still like the added tweeters but that plot was without any xover EQ right?

Whould you happen to have the resistors and cap to dupicate the Model 19 EQ circuit for the 802? Two 3.9 or 4 ohm in series then a 6UF in parallel with them. I'd love to see if that really flattens at least the upper mids out.
That info would be of great help to me and probably others in trying to figure out where to best cross tweeters in or to make a decision to ditch the 802's and try the BMS drivers with no tweeters.

Thanks
Dave

[Zilch]

Would you happen to have the resistors and cap to dupicate the Model 19 EQ circuit for the 802?

Gary sent me a M19 crossover to try, but I haven't unpacked it yet. I'll try what you suggest after dinner....

[Zilch]

Courtesy Altec Forum member DNV47:

http://www.hostboard.com/cgi-bin/ult...&f=3729&t=2597

[Zilch]

Would you happen to have the resistors and cap to dupicate the Model 19 EQ circuit for the 802? Two 3.9 or 4 ohm in series then a 6UF in parallel with them. I'd love to see if that really flattens at least the upper mids out.

That info would be of great help to me and probably others in trying to figure out where to best cross tweeters in or to make a decision to ditch the 802's and try the BMS drivers with no tweeters.

It flattens all of the mids, in fact.

That's similar to the parallel trap filter I'm using with BMS 4550. Clearly, if that were the extent of the compensation in M19 (there's more, as I recall,) you'd still need a tweeter with these Altec drivers. There's no action from that filter in the VHF above 8 kHz, but it certainly renders the driver "listenable" like LE85 on these horns, +/- 3 dB to 14 kHz.

Compare to what I'm presently getting with the 8-Ohm BMS 4550s on compensated Valencia 846B network, bottom. Those are the various L-Pad settings shown.

[I'm calling the 19 kHz spike "air" until I figure out if it needs to be "handled...." ]

[Gary L]

I am a little disappointed as it appears my 802-8Gs are only marginally smoother then the 806s with the 19 XO attached.

I have to plead some ignorance hear in following the graphs but as I understand it, the L Pads on the 19s don't really act as L Pads and have optimum settings as depicted on the face of the XOs. Have you tried various dial settings and do they make much difference at all?

I know here at home, the closer to optimum they are the better the speakers sound to me.
I also don't know if the caps in the XO I sent are in or out of spec or if this will affect the results here.

I also sent just one Altec "light" # 23744 Diaphragm, the other was too hard to get to on short notice. Hopefully you will get a chance to test this and possibly debunk the notion these are much better then new 34647s.

Great info so far and with a little luck I will be starting on a pair of 19 cabinets soon. If a tweeter is necessary to make them sound much better then I can surely incoorporate this in my building plans once the info is deciphered and an attack plan is set. With your permission Zilch, I will dubb these the Z-19s.

Thank you

Gary

[DaveV]

Thanks so much Zilch,

Well I'm not impressed with the "compensated" 802-8G response but then again I knew that before I saw the response curve. I had hoped that they would have been more flat up to at least 7-8KHZ with the EQ.

I just looked at the response curves done for my EV T350's with a Liberty Audio Suite system and they look like a mountain/valley range in the 5 to 8K range and they rise back to 10KHZ so they aren't great either, yet they add so much.

At this point I can only conclude that their addition to my 19's is more of a filling in affect and because I have them crossed over so high and neither driver is severly "peaked" at annoying frequencies, an overlap situation isn't a big sonic issue in my situation. Forget the 19KHZ peak. How many of us can hear that anyway?

I tried listening to the 19's again with no tweeters and if I had never heard the source material before with other efficient speakers with tweeters I may think the 19's were OK but somewhat lacking in upper VHF's and UHF's. But I don't think that would be entirely correct because the added T-350's drop like a rock at 14KHZ so it's not really the UHF's I miss.

Having heard things on the majority of source material that is subdued or just about missing without the added tweeters, I can't go back because it's just that detail that makes or breaks a recording for me. I'm not talking about detail in frequencies over 10KHZ either.

In all fairness I have to say that with the added tweeters my 19's are a source of enjoyment and I find myself listening to the music more than I ever have with any other speaker I've owned so far but the quest to enjoy them even more is present.

The BMS driver looks good on paper but how it "sounds" compared to an 8028-G is another issue but for the price I think they are worth trying.
Will you be making the comp network that resulted in the almost flat response public?

It seems to me that if they do sound good on the 811 one could "uncomplicate" the 19 xover to make a more direct path to benefit not only the bass but the higher range too.

Dave

[Zilch]

I am a little disappointed as it appears my 802-8Gs are only marginally smoother then the 806s with the 19 XO attached.

That's not the full M19 crossover running yet, Gary, merely one of the elements that operates on the midrange that Dave requested I try for him. Give me a couple of days to get the whole deal working before coming to any conclusions.

Yes, the M19 controls are doing much more than adjusting levels. They're "shaping" the frequency response as well....

[Zilch]

The BMS driver looks good on paper but how it "sounds" compared to an 8028-G is another issue but for the price I think they are worth trying.

There's no way I can redesign the entire Altec product line here, and there's certainly more to doing that for any one of them than just a driver substitution. However, for those who were contemplating biamping M19 when I did the crossover sim analysis last year, or who are considering that now, parsing out how M19 does what it does like this certainly provides guidance as to what would be required to accomplish that successfully. Without compensation, they're just going to sound, well, "nasty."

http://audioheritage.org/vbulletin/s...26&#post128826

Will you be making the comp network that resulted in the almost flat response public?

It seems to me that if they do sound good on the 811 one could "uncomplicate" the 19 xover to make a more direct path to benefit not only the bass but the higher range too.

Yes, of course, and what we've just done here may simplify that somewhat. There's still issues regarding transition to the LF even in Valencia which I have not addressed but in the abstract to date. I'm depending upon Jack to give an indication of whether what I've done thus far warrants further pursuit.

As you say, there's not a huge investment in trying the approach, and having measurement capabilities certainly facilitates the process, but the bottom line is how it sounds in the complete system....

[Zilch]

Well I'm not impressed with the "compensated" 802-8G response but then again I knew that before I saw the response curve. I had hoped that they would have been more flat up to at least 7-8KHZ with the EQ.

O.K., I put YOUR filter on BMS 4550 (Green), then tweaked it a bit to the values I'm (in part) using (Black). Put that in your M19s and cross at 1.2 kHz.

You've got Liberty Suite; that's a very competent package. I have a speaker designer pal here who uses it to great effect and benefit. Let's see your before/after plots here!

[DaveV]

Thanks Zilch,

The comp'ed BMS looks pretty good and the flatter, not dipped response like the 802G might be the ticket to the missing detail I complain about with the 802G's? I think minus 2-3db can mean a lot if your not using HF EQ or treble controls.
The horn in 1950's 604B I have seems to have the detail I'm talking about so I doubt it's the VHF I'm missing. How well can that old original diaphram be doing up there?

The reference to "your" filter has me confused about what you actually used. Was it just 8 ohms with a parallel 6uf cap in series with the BMS?

I don't have Liberty Suite. The T-350 response curves were done for me by someone that had access to it back in 2000.

If your going to run a response plot on the 802G with a "full" Model 19 xover I should wait to see that but I wouldn't think the addition of a .3mh inductor and pot in series with the 802G would help flatten or extend the response but who knows?

Dave

OPPS never mind about the values Zilch. I now see them on the bottom of the graphs. DUH

[Zilch]

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[Zilch]

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[Zilch]

Maybe you'll hate Mylar.

I'll ask Earl K to come over here and tell us how to knock the 19 kHz spike down....

[Earl K]

I'll ask Earl K to come over here and tell us how to knock the 19 kHz spike down....

- I'd leave it if this was for me . My 288-8K horn setup has a +4 db spike at around 13.5 K and I like it in place. 14K is my threshold for UHF adibilty / after that frequency, I just sense frequecies as a constant pressure ( oddly enough in my upper jaw area ) .

- You could try a series LCR ( across the drivers' terminals ) / though I never use them above 10K . The 3 ohm series resistor will ensure the amp doesn't see a short-circuit at 19K through C4, the 6 uF bypass cap . It may see 3.5 ohms / but that's not a short circuit ..

- For lack of a better formula / the working loop impedance within that part of the circuit will approximate 2 to 2.2 ohms ( 3 ohms & 8 ohms / or / "load & source" in parallel to each other ) .

- Getting 6 db of notch within such a low impedance loop will require a very low value R plus pretty high "Q" components for the cap & coil ( start with a 16 gauge aircore & a Solen MPP ) .
- So you know, the ad hoc formula I published in late fall within dmtps' thread was lacking a "correction factor" ( or weighting multiplier ) to account for the overall lousy real-world performance of passives ( vs those nice theoretical simulations ). ( The thread petered out before I got a chance to reveal this info within the framework for my "rules of disclosure" / in fact / "the hangup or roadblock" was that a workable "loop impedance" was never mutually "discovered" & agreed upon . )
- Anyways, I've usually used 1.5 to 2 as a multiplier within that formula ( to increase the necessary reactive inductance ). This results in a coil size that is significantly larger than what book theory would suggest,though the resulting coil sizes are a good deal closer to those used by JBL for their series LCR notch filters .

Maybe you'll hate Mylar.

Yeh, one never knows until one listens . I prefer Altecs' aluminum diaphragms over all the Mylar stuff I own ( from B&C ) . "Overdamped" up in the HF area is the descriptive word I'd use . My ears crave a bit more "excitement" up in that range .