Altec 902s on the Way!!

[cjgeraci]

As some of you know, I recently reached a happy place with my 7.1 Heritage system, especially after I added Al Klappenberger's Extreme Slope networks to my Klipschorns (along with Al's Trachorns and Eminence tweeters), hooked up the VRDs to those and plopped some nice 511s on top of my rear Belles, along with ALK Universals (premium caps) and Beyma tweeters.

But...........as good as the Khorns were, I still heard the limitations of the K55s. So, as Maron and Dave know, I can just never leave well enough alone.

First, I bought a pair of used JBL 2470s with original phenolic dias off of Ebay. Bad idea, and I knew better. They arrived DOA, and I went through the hassle and delay of returning them - and money back.

Next, I seriously toyed with the idea of again moving up to a two inch driver, especially in light of the recent experiences by those in the Jub club. But, while I had the drivers picked out and almost purchased, I did not want to take the added financial plunge of going with a quality horn such as a K402 or K510 (at least not just yet in light of the latest kitchen (and potential basement) remodelings and my existing debt). So.........I would have been flying blind to start with probably P-Audio horns and a potential headache on my hands.

In the meantime, Uncle Maron loaned me a nice active crossover and convinced me to play around with it. I started by playing around with the K55 in two way mode and then plopped the 511s up front on the Khorns. For the last week, my ears tell me that crossing over the Khorn bass bin at 500 hz (vs. 400) is fine (with a 18db slope). Maybe it won't end up measuring out that way once I run a RTA on it, but to my ears flipping back and forth on tons of songs, I do not hear a difference. Well, maybe ignorance is bliss.........

So...........today I called up Bill again at Great Plains. After doing some additional internet research on tons of every thread I could find on Altec, JBL and every other forums, I almost told Bill to send me a set of new 909s (pascalites) even though at least a percentage of people say that the 902s are sweeter (by a bit).

Bill's always been a great guy every time that I talked to him and today was no different. Truly, an asset to fine audio by keeping the Altec legend alive. Bill's opinion is that the 902 and 909 sound alike to his ears. He convinced me to start out with new 902s and says that I won't blow them in my system, even though he knows about my volume propensities........[*-)]. Plus, he reminds me that they come with a warranty and if I blow 'em, he'll just put a set of pascalites in. [H]

So, hoo, hoo, hee, hee - - - here we go. The 902s arrive Tuesday or Wednesday. I will start out by staying with active two-ways for the front Klipschorns, (with VRDs on the top and QSC PLX on the bass bins) crossed over at 500 hz. I'm starting with 902s on Al's Trachorns.

The 511s move back to the rear Belles. Al's Extreme Slope networks are sounding great back there, and I'm running them by the Sonic Impact Super-T amp or my Dynaco Stereo 70 (depending on the mood).

After playing with the Trachorn/902 two-way thing for a while, I will probably then try the 902s with the 511s.

Should be fun................The nice Heritage 7.1 is about to get just a little bit better....

Carl.

P.S. Uncle Yoda!! You know that my Eminence tweets are now lonely. Them beautiful supertweets would sure look purty on top of my Belles..............................maybe after you're done playing with four ways, Link could let me play with 'em...........................[:#]

[Marvel]

Carl,

All I can say is VERY COOL! I really toyed with the idea of purchasing a pair of the 902s new (I want to try some on some Smith horns). I just have too many other debts right now to swing it. I can hardly wait to hear your opinion of them.

Bruce

[cjgeraci]

Thanks, Bruce. I will have some frame of reference. I've also run aluminum 806As (811s and 511s) and less than stellar symbiotik dias in both Altec and Klipsch speakers.

Of course, there is no free lunch. Oh, well, so I had to sell another piece of my gear.................have too much "stuff" anyway.

Carl.

[bluesboy]

Carl,

Are you getting the 16 ohm or 8 ohm version 902?

[Erik Mandaville]

I bet they are going to look incredible and sound even better, but whatever you do, don't touch the autoformer!

Erik

[cjgeraci]

Carl,

Are you getting the 16 ohm or 8 ohm version 902?

You know, I actually did not tell Bill which version to ship so I assume that he will be shipping me the 16 ohm versions. That being said, even if he ships me the 8 ohm versions, it does not matter. Both of my passives (Al's designs) have adjustments for squawker level and the amp sees a constant 8 ohm read, regardless of the ohm of the driver. Running either version with the active also will not present an issue. And, the VRDs have taps for either 16 ohm or 8 ohm.

Carl.

[cjgeraci]

I bet they are going to look incredible and sound even better, but whatever you do, don't touch the autoformer!

Erik

Thanks, I think so.

Huh? Please explain..................................

Carl.

[PrestonTom]

This 2-way system will turn out to be a model system that others may want to emulate.

A few questions. First, my understanding was that the 511 / 902 would probably need an aluminum diaphragm when run as a 2-way in order to get the high frequency response. I might be wrong on this point.

Second, I suspect that, as a 2-way, the 511 / 902 would need some boost for the highest octaves. Are you planning to do this with an equalizer or is the ALK crossover being modified to provide the boost (I lost track of which crossover is being used where). Certainly the high pass section on the 511/902 should be set steep enough to prevent too much low frequency energy through the 902.

Third, the similarity in sound when the bass bin was high-passed at either 400 or 500 may result, in part, from the fact that the speaker/bass bin have quite a bit of natural acoustic roll off. Some folks actually don't even bother with the low pass filter - inductor in series with the K-33 - (it is said that PWK did it this way also).

Good Luck,

-Tom

[cjgeraci]

This 2-way system will turn out to be a model system that others may want to emulate.

A few questions. First, my understanding was that the 511 / 902 would probably need an aluminum diaphragm when run as a 2-way in order to get the high frequency response. I might be wrong on this point.

Second, I suspect that, as a 2-way, the 511 / 902 would need some boost for the highest octaves. Are you planning to do this with an equalizer or is the ALK crossover being modified to provide the boost (I lost track of which crossover is being used where). Certainly the high pass section on the 511/902 should be set steep enough to prevent too much low frequency energy through the 902.

Third, the similarity in sound when the bass bin was high-passed at either 400 or 500 may result, in part, from the fact that the speaker/bass bin have quite a bit of natural acoustic roll off. Some folks actually don't even bother with the low pass filter - inductor in series with the K-33 - (it is said that PWK did it this way also).

Good Luck,

-Tom

Thanks, Tom. I figured that I took the three-way Klipschorn about as far as I could take it so it was time to play around with two-ways. I don't know about it being a model, but I've thought about it for awhile.

1) Yes, the brand new 902s that Bill makes at Great Plains Audio (from all of the old Altec plans/stamps) have aluminum diaphrams in them, and these should hit 20k. The 909s that I mentioned were the pro version of the high frequency Altec drivers and used pascalite dias, which are made from a very similar metal to aluminum. Call them pseudo-aluminium, if you will. The true-aluminum 902s were always supposed to be a little sweeter sounding than the 909s (developed to replace the symbiotik - for theatre applications) so I'll take Bill's word that the 902s will take the pounding in a home environment.

2) Yes, I plan on boosting them with the high frequencies at some point after I get a baseline (since the eq compensation network in the Altec 19s worked so well). First, I am going to run them two-ways using the Trachorn 400, and with an active crossover set to 500 hz (18 db slopes). I may then run them with passives. I also have two Al K networks I can also use (ALK Universals and ALK gentle slope bottoms, ES tops). I have used the ALK Universals crossed over at 500 hz (12 db) and could use the ES tops if I get a different bottom end (500 hz). After I run the 902s without eq or boost for awhile, I will then insert my Behringer UltraCurve Pro into the system, probably after the prepro and run the RTA - and get some boost (or take the middle down).

3) A little bird told me about tests on Khorns in certain chambers where they were making it up to 510 hz. Based on that, I felt confident that I could play around with the active at both 400 and 500hz. There has been so many rumors/legends out there about the bass bin not doing squat above 300 hz or so - I think people over the years have bought into the hype - and as a result, been looking for the magical 350 or 400 horn. I do not think that it is really needed.

Carl.

[PrestonTom]

"......

3) A little bird told me about tests on Khorns in certain chambers where they were making it up to 510 hz. Based on that, I felt confident that I could play around with the active at both 400 and 500hz. There has been so many rumors/legends out there about the bass bin not doing squat above 300 hz or so - I think people over the years have bought into the hype - and as a result, been looking for the magical 350 or 400 horn. I do not think that it is really needed.

Carl.

......"

In the JAES article where they outline the Jubilee bass bin, the K-Horn is used as referent. Consequently there are a number of data shown including the anechoic and the corner loaded frequency response of the K-Horn, IIRC. They certainly will hit 300Hz but after that it is difficult to easily describe - best to have a look at the plot. The article has been peviously uploaded.

But you are right, getting a single horn to go from 300Hz and then all the up is asking for quite a bit. One advantage you have is that the high pass section of the crossover on the 511/902 can be steep so you can really push the cutoff frequency. Actually, if you are willing to go to an electronic crossover further possibilities exist. But I am getting ahead of things there ...

Good Luck,

-Tom

[cjgeraci]

Actually, I will be starting out with an electronic crossover, abeit an older unit. It does not have some of the features of the latest ones, such as delay, but it has very high quality op amps - and a nice sound.

As far as the horns go, I've had the Trachorn 400 and the 511s both for awhile now, and using them as mid-horns, the Trachorn sounds smoother than the 511. That being said, I am also aware about horn/driver synergy, and the 902s were designed specifically for the 511s/811s. So, first, the 902s go onto the Trachorns and then later, I will also put them on the 511s.

Carl.

P.S. Since I've been running the electronic crossover up front for a couple of weeks now, I moved the Extreme Slope networks to the rear Belles. They have never sounded better!!

[cjgeraci]

Carl,

Are you getting the 16 ohm or 8 ohm version 902?

I told you previously that it did not matter which ohn version that I ended up with, but your question got me to thinking about it - and I may not always have the luxury of running this active or the nice ALK Engineering crossovers. Therefore, I called up Bill to check into which set he had shipped me. He said that they did not make it out the door yet, but were sitting there with a shipping label ready to go out, a pair of 8 ohm versions. Since I've had all 16 ohm drivers (K55V, 806As, etc), I told him to ship me a pair of 16 ohm.

Nice guy, he said that he would make it happen today - and without a fuss.

Carl.

[bluesboy]

Carl,

Are you getting the 16 ohm or 8 ohm version 902?

I told you previously that it did not matter which ohn version that I ended up with, but your question got me to thinking about it - and I may not always have the luxury of running this active or the nice ALK Engineering crossovers. Therefore, I called up Bill to check into which set he had shipped me. He said that they did not make it out the door yet, but were sitting there with a shipping label ready to go out, a pair of 8 ohm versions. Since I've had all 16 ohm drivers (K55V, 806As, etc), I told him to ship me a pair of 16 ohm.

Nice guy, he said that he would make it happen today - and without a fuss.Yes , that's what I was thinking. If I had a choice I'd get the 16 ohm version. You'll be pleased with the 902's. They are a big improvment over K-55's. What's Bill getting for a pair these days?

Carl.

[cjgeraci]

Carl,

Are you getting the 16 ohm or 8 ohm version 902?

I told you previously that it did not matter which ohn version that I ended up with, but your question got me to thinking about it - and I may not always have the luxury of running this active or the nice ALK Engineering crossovers. Therefore, I called up Bill to check into which set he had shipped me. He said that they did not make it out the door yet, but were sitting there with a shipping label ready to go out, a pair of 8 ohm versions. Since I've had all 16 ohm drivers (K55V, 806As, etc), I told him to ship me a pair of 16 ohm.

Nice guy, he said that he would make it happen today - and without a fuss.Yes , that's what I was thinking. If I had a choice I'd get the 16 ohm version. You'll be pleased with the 902's. They are a big improvment over K-55's. What's Bill getting for a pair these days?

Carl.

Right at about $404/pair, which is still a great price for a new pair - considering I've been burnt more than once by used "vintage" drivers.

[ZAKO]

Carl.....I,m sending you some special frequency plots of bass bin... by slow mail to your office.

[gaspr]

Carl...looking forward to hearing your impressions of the 902's on the

trachorn as a two way set up... I don't think that I have ever

seen any polar response plots for Al's trachorn. I assume that

like most other normal tractrix horns, it will narrow its dispersion

pattern as the frequency goes on up. Just wondering if this is a

concern...

[cjgeraci]

Carl...looking forward to hearing your impressions of the 902's on the trachorn as a two way set up... I don't think that I have ever seen any polar response plots for Al's trachorn. I assume that like most other normal tractrix horns, it will narrow its dispersion pattern as the frequency goes on up. Just wondering if this is a concern...

Yes, I've thought about that. My recollection is that any plots I have ever viewed for Al's horn only went up to 6000 or so because of the drivers being used and a crossover being implemented up top.

So, what the heck I may as well be the first to try it...........If the dispersion pattern is screwed up on top, I can always use them on the 511s as two-ways.

But, since the Trachorns are smoother overall, I decided to try them first.

Carl.

[cjgeraci]

It might be a long night.......................................but only because that is a good thing.

The 902s arrived today. It turned out that Bill became sidetracked with other customers after I spoke with him on Monday, and did not switch out to the 16 ohm versions. But, since I ended up trying them with a solid state amp, the fact that these are 8 ohm versions ended up being a good thing.

I'll post pictures of these beauties tomorrow. And beauties they are. Nothing like two brand new drivers - taking you back in time. Of course, solid as a rock and actually somewhat heavier than other vintage Altec drivers that I have owned.

I attached the 902s to Al's Trachorns and fired them up with the VRDs on top and the QSCs on the bottom end, in two-way mode using the active crossover. I listened to some Yes, Crosby, Stills & Nash, Mozart, and Scorpions. The 902s sounded smoother than the K55s (no surprise) and overall, more natural sounding. I closed my ears and then began to focus on the very top end. My system has overgone some changes in the past few years, and I've had a variety of big two and three-way horns in the man cave. Prior Altec drivers have always been a bit insufficient on the very top end. Closing my eyes, I could cymbals and the extension on the top end, but with the VRDs it seemed to be too much in the background. I thought at least the top end is there, and I can eq the sound later with my Behringer UltracurvePro.

Then...... on a whim, I remembered what Tom Brennan has said - - something to the effect of good speakers sounding good no matter solid state or tubes. So, I turned off the tubes and hooked up my Sonic Impact Super T to the 902s. Even since Sonic Impact decided to adopt some of the mods to the original "T" amp, I've been fascinated with this little amp because a $150 amp just should not sound as good as it does.

Well, wow, wow, and wow.......................................................................................................................

Granted, I've only been listening to the setup now for about a hour or so with the Super T on top at moderate levels (in the man cave downstairs - I can go louder than you think without waking the rest of the house). Put on Yes, Scorpions, Steeley Dan, Satriani, David Friedman, Clifford Brown, live Supertramp, and Kansas. I forgot how great an excellent two-way sounded. Seamless with great imaging. With the Super T, the utmost highs are clear and there all the way to the highest cymbals. It is kind of strange, switching amps is like I eq'd the sound to bring the very top up - but I haven't.

After listening to the Super T amp for about a half an hour, I then put the VRDs on the rear Belles and took their tweeter level down (which now have Al's Extreme Slope networks) - and dialed in the volume mix front and back off of the tube pre. Seamless front to back.

Of course, I should provide the caveat that I have not really laid into 902s at extreme levels yet, and I'm always reminded of giving your changes some time to sink in - with multiple listening sessions.

But....................I can tell you preliminarily that the 902s sound great in two-way mode, my Klipschorns have never sounded better (and just make me drool at this point), and anyone seriously thinking about a set should just buy them new from Great Plains. In fact, with the 902/Trachorn combo, I do not think that I will find it necessary to go to a larger driver (2 inch throat) any time soon.

Later, I will of course try the 902s on the 511s to compare - and yes, break out the measuring equipment. But, on the first night, my ears are very, very happy.

Carl.

[ZAKO]

Carl glad everything worked out....Sit back and enjoy for awhile...Let your ears get acclimated to the change as a reference.... Dial in and touch up levels..with different types of music.

[IB Slammin]

.............. It turned out that Bill became sidetracked with other customers after I spoke with him on Monday, and did not switch out to the 16 ohm versions. ...............

Funny how that happens with Bill. Mine also. However he DID fedx the 16's to me overnight.

.......I have not really laid into 902s at extreme levels yet,...........

(Said with a NYC Italian Accent) Don't worry about it. I have.

Hammered the 902-16a first order crossed at 400hz. Noooooo prob! Go for it.

Enjoy

tc