Altec 9844-8B

[Zilch]

I have only woofers 4x414-16B and 2x806A+811horns,also the N800-F crossovers.
I read your experiments on 9844 speakers.First I was thinking to make the same enclosures.
Also I'm thinking to use them into another setup configuration/enclosures.... ....more like K2 9500/5500 series design to give more impact on the bottom.I know ...probabily I loose some spl.Do you think your M-19-Z could fit to 806A drivers?
What do you think?
The 806A's could'nt touch more than 14-15khz max.;so I'm thinking to attach a supertweter like Fostex T90A.

Altec made several products stacking the 414s vertically. This thread tells you how to get augmented bass out of them by using one of the pair as a "helper." Skywave's possibly the first to try the approach with these woofers, and I believe he's telling us it works, and that he likes the result.

The M19 crossover, in whatever form, is configured for 8-Ohm HF drivers. You may find some clues as to how to adapt it for 16 Ohms on the Markwart site. Another option is to install 8-Ohm diaphragms in your 806As.

As you know, however, 806As aren't going to get much past 14 kHz no matter what, and integrating a tweeter with them on 811B horns is problematic. Frankly, I'd abandon the Altec HF drivers AND 811B horns and just do this with dual 414s in 2.5 mode and BMS 4555 on JBL PT-F95HF waveguides:

[felixx]

An waveguide have less problems.
How about the material from what is maded?I think wood or concrete cement will be the best compromises.

Check this one:
http://www.partsexpress.com/pe/showd...number=270-312

Or an oblate from 18Sound:
http://www.eighteensound.com/index.a...roduct&pid=177

Or:
http://www.flickr.com/photos/12312992@N07/page2/

[Skywave-Rider]

I was thinking of trying the 1" version of the 18 Sound horn you linked to
http://www.eighteensound.com/index.a...roduct&pid=179
in a different project.
But I went with the JBL waveguide Zilch showed.
Economy and proven performance made my decision.
And it's great.
I wouldn't change the horns in the 9844s.
They're vintage, and I like the sound.

[felixx]

I think will be nice to make a wood rouded or horizontal horn.
The mark of the horn counts for me.
Do you have good reports about using metal or cheap "plastic" horns?Some ringing problems or artificial-plastic "sound"?

Another question....
Do you think will be differences between an horizontal horn and a rounded one?

http://www.flickr.com/photos/12312992@N07/page1/
http://www.geocities.jp/arai401204/H...FL/A480FL.html

http://www.geocities.jp/arai401204/

[Zilch]

1) N800F w/902

A) Clearly, 902s have full extension with the stock crossover, but +/- 2.5 dB undulating response throughout the high-frequency range is unacceptable. Your 902s will arrive here in a few days, and if that appears in my measuring them, I'll try to figure out where it's coming from.

B) The notch at 1K25 disappears in 2.5 mode, indicating it is the two woofers interfering with each other at that frequency for the measurement mic location.

C) The bass response is flatter in 2.5 mode, and there does not seem to be elevated response in the very low frequency range where the helper is operating, i.e., it's not making them "boomy."


2) N800F Nearfield

A) The influence of the load impedance upon the acoustic response produced by the filter is quite apparent. At 16 Ohms, it follows the Green curve. With two woofers playing and summing, the midrange would swamp the bass if they weren't playing on the Cyan contour.

B) With the 20 mH in series with the 16-Ohm dummy load, the single woofer plays the Green curve, as the inductor's high impedance at higher frequencies decouples the parallel load from the filter. Thus, in 2.5 mode, the main woofer plays the Green curve, what we want, presumably, since there is no summing of two woofers playing in the midrange, only the low frequencies below 200 Hz.

C) Individually, helper and main show similar performance; they are well matched.

D) The 20 mH rolls off the helper above 200 Hz nicely. It's effectively "Off" above 500 Hz.

E) Both woofers/2.5 shows more elevation of the VLF than theory would predict, even with mutual coupling. That does not appear in the full-range curves, though, so my guess is the port output is exaggerating nearfield response measurements. In any case, it's beautifully flat down there. I'm calling 2.5 a successful and worthwhile upgrade from the measurements.


3) 4552Nd on N800F

A) Well, that's the name of THAT tune, I would say -- so much for 902s, at least your pair in their present condition. 2.5 and BMS substantially improve the performance, even using the N800F crossover.

B) Some minor tweeks of both filters could likely smooth out the response in the crossover region between 800 Hz and 2 kHz. I'm betting that's the best 9844s ever sounded.


4) 4552 on M19Z

A) Same with M19Z. Looks like even though you don't have the mid attenuation quite low enough for maximally flat response, the contour is better than that generated by N800F.

B) The lowpass filter is not optimum, and needs tweeking. Run the M19Z highpass with the N800F lowpass as I suggested might be a better combination above.

C) M19Z offers the benefit of adjustable HF contour, but it's almost necessary to have measurement capability to adjust it optimally. Those without that should stick with N800F, probably, built new, once you verify the HP filter capacitor value.

D) Open one of your stock N800Fs, please, and determine the highpass capacitor value, so we'll know which design to recommend.


5) M19Z Nearfield

A) A repeat performance. Flatter than N800F, and without the peak at 1K25.

B) Compare the lowpass filter components of M19Z vs. N800F. Tweak M19Z for best response through the crossover region.


You're nearly done with this project, and should be very pleased with, and proud of, what you have achieved with this.

I know I certainly am....

[djgaloot]

I am following this thread with great interest though I do not have the electronic and acoustic technical expertise of you guys. I hope that in the end someone (Zilch, Skywave) would write a short summary with conclusions. I have a pair of Malibus which have two 414s arranged vertically and a 806/811 horn with the N800 crossover. I believe they are very early 1960's vintage and nearly perfect condition. They sound pretty nice but I was planning on rebuilding the crossover or perhaps, down the road, going the electronic xover/biamp route to maximize performance. I also have the parts to build a 9844 clone as a center channel. From the work done so far it seems that a BMS 4552ND driver will offer more extension with the 811 even with a stock N800 and that the 2.5 mode will smooth out the bottom. I am still a bit unclear on exactly what the 2.5 mode is. Is it running the 2nd 414 as a passive radiator or crossing it over a bit different with an inductor?
Thanks for all the work!
Dave

[Skywave-Rider]

Hi Dave,
It's nice to hear from you. I think two vertical Malibus flanking a 9844 center would make an amazing installation. In 2.5 mode you will have less phase cancellation problems in the midrange from having the 414s arrayed horizontally. That's a good application for a 9844 type box. (Don't take my word for it, though. LOL)

Zilch should have my 902s today for testing. You may want to hear what he has to say after he scopes them. I'm sure whatever he finds will be posted here.

I will do a "final" summary eventually. But you've probably read my most recent listening report.

2.5 or "helper" mode means one of the 2 paralleled woofers has a single pole filter inserted in series with it. In this case the filter is a big 20 mH inductor, which moves the low pass point down significantly compared to the "main" woofer. It's operating at approx. 200 Hz. At frequencies above 200 Hz, essentially one woofer, a 16 Ohm load is operating, accounting for the reduction in mid/lower mid frequencies.

At frequencies below 200 Hz, both woofers operate at a lower impedance (8 Ohms) and therefore deliver more output, work together, and couple acoustically. BTW, I learned all of this from Zilch, who suggested this concept. (JBL apparently uses 2.5 in the Everest monitor.) You can also read about it in Dickason.

The other factor which nudged me into buying the coil was the aforementioned horizontal layout problem. I have not yet done much stereo listening, so it's hard to comment on whether or not imaging tightens in helper mode.

Stay in touch.

[djgaloot]

Skywave,
Thank you for the explanation of the 2.5 concept; I am still trying to wrap my mechanically-minded brain around it. Do you get some bass interaction (boost?) from the now somewhat passive 2nd woofer above 200hz or are you separating the two woofers with a baffle arrangement. Seems like things could get "confused" acoustically. I will continue to lurk and learn and go back and re-read all the work you have done. FWIW, I have a pair of Boleros that use a passive radiator in a horizontal arrangement that will be my rear surround speakers for now.
Dave

[Skywave-Rider]

Dave,
Zilch has a pretty good explanation of the passive conundrum here in this post:
http://audioheritage.org/vbulletin/s...&postcount=185

My two cents: Most recorded program material includes frequencies below 200Hz. So the helper is mostly active and energized. Does it radiate passively at higher frequencies? I don't know, but in a multi way speaker where drivers share the same volume, would that also be the case? For example a mid driver exciting a woofer in the same box. I don't know but Zilch's explanation seems reasonable to me.

It's a good question and I bet a lot of people have thought about it like we are.


Dave, do you know where I can find pics or Altec lit. referring to Malibus?

[djgaloot]

I have pictures of mine and some info. I sent a PM
dave

[Zilch]

Skywave's 902-8Bs:

[Skywave-Rider]

Cool.
Zilch, is #1 the driver I have marked (with tape) as #1? That's the one in my RTAs.

Thanks, I need some time to look.

[Skywave-Rider]

I just started reading the Clio Clinic thread. I may have questions later.
In referencing my RTAs, so far looks about the same. The top curves are raw driver/bottom M-19, correct?

Is that a BMS-like spike at 19k? (Breakup?)

In the last RTA 1/6th octave, the cyan, "-3M" means 3 meters back from the violet measurement? Is that 4meters? Or does it mean something else entirely?


Is it possible to do a "transient response" test of these?

Most importantly, are you regretting ever getting involved with this old junk?

PS: I now believe I am somewhat colorblind. LOL

[Zilch]

Yes, #1 is the one you marked as such.

Yes, top curves are the driver raw response with only a 47 uF protection capacitor in series. Bottom is each running on M19 XO.

"3M" is three meters. First thought was, as we have often seen others assert, that some distance is required for the horn to "integrate," so I pulled back about 10 feet and did RTA. That's not it, apparently.

Yes, I can do step response, but I'll have to read up on it.

I've attached two pics of the diaphragm in #2 below. The numbers stamped on there are:

35480
31060
979 8328

Perhaps someone can identify this.

http://audioheritage.org/vbulletin/s...5480#post14606

There are indications on other forums that these are factory "Light" diaphragms for 902s. PM Dgwojo for confirmation.

I compared the response of both drivers on 811 vs 511 horns, bottom. 511 plays lower, and is a little smoother; it also rings considerably more than 811.

Using driver #1, I can render it listenable with M19 crossover, bottom curve. As I observed in the Valencia studies, it has a pleasant, "throaty," sonic character. The driver is altering the timbre across the high-frequency spectrum according to the response curves. Yes, I can hear that. It's wrong, and unnatural, but again, not unpleasant sounding.

Similar undulations appear in the CBS Labs M19 measurements from 30 years ago, and in the measurements I did on Gary's 802-8Bs last year:



I'm suspecting the "TANGERINE Radial Phasing System" is the culprit here. Has no one else ever measured these Altec drivers and horns? Where are the curves? :dont-know

[Zilch]

Most importantly, are you regretting ever getting involved with this old junk?

There's certainly no dearth of wank and blather about it.

Earl suggested in an earlier thread that the pattern may be sufficiently consistent that a series of passive notch filters would be a reasonable approach. I applied AutoEQ to test that, below.

The difference is clearly audible. Flat is a bit strident, room corrected is better, but now I hear the horn ringing.

Can it be fixed? I'd say, "probably."

[Not my job, tho.... ]