Altec 902-8B/511B Reunited!!!

[chops]

Here's a little bit of interesting info. After work today, I pulled out the mic and did a few measurements. The two I'm going to show here are only of the right channel at 1 meter distance. Both plots were done with the Quick Sweep function and at full freq range. (20Hz - 20kHz) The 902 is crossed over at 375Hz. The K33 is rolled off at 437Hz.

This first plot is the raw output of the K33 and 902 as is...

This is the same thing, EXCEPT that the treble has been boosted +3dB at 10kHz...

One thing I noticed right away was the dip between 250 - 500Hz. At first, I thought that maybe the 902 might be internally wired out of phase from the K33. So I reversed the polarity on both 902s. There was a change, but the dip grew a little deeper, so back they went.

The second thing I noticed is that the driver starts to roll off from about 1kHz and is down about -12dB by 20kHz. Now the weird thing is that if I raise the "Hi Freq Limit" of the plot to 50kHz, the driver actually plays out to around 25kHz then slams the door. The strange thing is that Bob's CT125s in this same exact setup seemed to hit a brick wall right at 20kHz and nothing after.

And the last thing to mention is that the K33/902 combo is nowhere near as flat across the board as the K33/K-55/CT125 combo was.

Hmm... What to do?...

[sfogg]

"And the last thing to mention is that the K33/902 combo is nowhere near

as flat across the board as the K33/K-55/CT125 combo was."

Change your high and low levels in TrueAudio to be the same as the other measurements. Your vertical scale is different which makes the differences look larger.

Shawn

[Guest " "]

"Run the same plot with out the autoformer. Am I to believe there is no loss at all by uisng and autoformer."

No kidding the plot will be 'louder' without the autoformer.

Again... the autoformer IS THERE FOR ITS ATTENUATION. 

The point is the squawker IS LOUDER (more efficient) THEN THE WOOFER

AND THE TWEETER. It needs to be attenuated so that its output level

matches the other drivers in the system. That is what the autoformer

does... attenuates the squawker to match the other drivers in the system

Learn what the part is for before you complain about it.....

Shawn

Just to broaden our horizons, none of the systems that uses the 902 driver uses an autoformer in it's crossover. I have a CD of altec material, and I could not find any.

And oh by the way, neither does the current AL-4 klipsch network. Lets not assume the autoformer it is the only method of adjusting output.

In terms of knowing the behavior of klipsch crossover's, autoformers, and attenuators, I think I have at leat 20 pairs of klipsch xovers in my posession, and at least that many sets of drivers. A, AA, Al, AL-2, AL-3, AL-4, AB, E, B-2. I have schematics for each also. Of all these xovers, ilike the AL-4 the best, it does not have an autoformer in it.

I have used Altec and JBL drivers in the past, upto 2 inch throats, no autoformers in the xovers on these either.

My initial advice remains, create a custom xover for the 902, and don't try to modify the b series crossover to accomidate the 902 in a 2 way implementation.

In earlier posts on other threads, I indicated the discussed xover point was too low and the combination would not balance out. I was clearly not in favor of using b series parts to make a 2 way xover for the 902.

I may not be an expert, but I know enought to recommend alternatives .

[chops]

"And the last thing to mention is that the K33/902 combo is nowhere near

as flat across the board as the K33/K-55/CT125 combo was."

Change your high and low levels in TrueAudio to be the same as the other measurements. Your vertical scale is different which makes the differences look larger.

Shawn

Hi Shawn,

Thanks for pointing that out to me. I should have caught that earlier. Anyway, here are two more plots, this time of the left channel, full range at 1 meter, no treble boost.

1) K33/K-55/CT125 - taken 2 days ago:

2) K33/902 - taken 10 minutes ago:

3) Close-up of extension to 25kHz: For some strange reason, the CT125s never made it past 20kHz... [:^)]

[Guest " "]

"And the last thing to mention is that the K33/902 combo is nowhere near

as flat across the board as the K33/K-55/CT125 combo was."

Change your high and low levels in TrueAudio to be the same as the other measurements. Your vertical scale is different which makes the differences look larger.

Shawn

chops,

others have ventured where you are trying to go....check this thread out. intresting discussion about xover points and xover orders with the 902 on the 511

http://www.audioheritage.org/vbulletin/showthread.php?t=2304

[chops]

Just to broaden our horizons, none of the systems that uses the 902 driver uses an autoformer in it's crossover. I have a CD of altec material, and I could not find any.

And oh by the way, neither does the current AL-4 klipsch network. Lets not assume the autoformer it is the only method of adjusting output.

In terms of knowing the behavior of klipsch crossover's, autoformers, and attenuators, I think I have at leat 20 pairs of klipsch xovers in my posession, and at least that many sets of drivers. A, AA, Al, AL-2, AL-3, AL-4, AB, E, B-2. I have schematics for each also. Of all these xovers, ilike the AL-4 the best, it does not have an autoformer in it.

I have used Altec and JBL drivers in the past, upto 2 inch throats, no autoformers in the xovers on these either.

My initial advice remains, create a custom xover for the 902, and don't try to modify the b series crossover to accomidate the 902 in a 2 way implementation.

In earlier posts on other threads, I indicated the discussed xover point was too low and the combination would not balance out. I was clearly not in favor of using b series parts to make a 2 way xover for the 902.

I may not be an expert, but I know enought to recommend alternatives .

Fritz...

I'm not trying to be a d**k or anything, but I'm kind of tired of constantly hearing this stuff. Can you please take this autoformer arguement elsewhere?

I don't need this thread turning into a pissing contest and being shut down when I'm trying to figure things out here.

Thanks.

[Guest " "]

Just to broaden our horizons, none of the systems that uses the 902 driver uses an autoformer in it's crossover. I have a CD of altec material, and I could not find any.

And oh by the way, neither does the current AL-4 klipsch network. Lets not assume the autoformer it is the only method of adjusting output.

In terms of knowing the behavior of klipsch crossover's, autoformers, and attenuators, I think I have at leat 20 pairs of klipsch xovers in my posession, and at least that many sets of drivers. A, AA, Al, AL-2, AL-3, AL-4, AB, E, B-2. I have schematics for each also. Of all these xovers, ilike the AL-4 the best, it does not have an autoformer in it.

I have used Altec and JBL drivers in the past, upto 2 inch throats, no autoformers in the xovers on these either.

My initial advice remains, create a custom xover for the 902, and don't try to modify the b series crossover to accomidate the 902 in a 2 way implementation.

In earlier posts on other threads, I indicated the discussed xover point was too low and the combination would not balance out. I was clearly not in favor of using b series parts to make a 2 way xover for the 902.

I may not be an expert, but I know enought to recommend alternatives .

Fritz...

I'm not trying to be a d**k or anything, but I'm kind of tired of constantly hearing this stuff. Can you please take this autoformer arguement elsewhere?

I don't need this thread turning into a pissing contest and being shut down when I'm trying to figure things out here.

Thanks.

ok,

check out this thread about the 902 AND 511. it's about xover points and xover orders for the 902/511 combination.

http://www.audioheritage.org/vbulletin/showthread.php?t=2304

[Deang]

You're worried about "loss", yet prefer the sound of a 20 element filter loaded with resistors over one that only uses 5 parts? Autoformers weren't/aren't typically used because they cost 50 times more than using L-pads. No, Altec didn't use them, but I did recently build a pair of autoformer based networks for some Valencias -- maybe Carl will chime in with his opinion regarding the difference between what I built and what he had. At any rate, it is the expensive way to attenuate -- and plain sounds better. I started with AK-4's, have built just about every Klipsch network for the Klipschorn with almost every part imaginable -- and it remains my least favorite network.

You need to read, "The Problem with Attenuators", by Paul W. Klipsch. Also, The Dope from Hope with analysis comparing distortion levels between autoformers and L-pads. I have copies at work on my hard drive -- I'll post on Monday if no one else does between now and then.

Charles -- I told you how to build it in the other thread, now build it. It will sound better if you use Auricaps or Kimbers.

[Guest " "]

Chops requested discussions about Autoformers be taken else where. I'll read the article and if any follow up items are warranted I start another thread.

I posted a link about the 902 on the 511 xover points and xover orders to help get the thread back on track.

the link is leaning toward 24db per octave xovers and a cutoff between 600 and 800 htz, for high power use.

there is some discussion about the trade off in power handling as to go down to 500 htz (15 watts?) on lower order networks.

I was looking for info about the rolloff, and being a person who thinks outside he box, was wondering if the rolloff was a function of the 511 horn itself. the graphs Chops posted for his 511/902 combination looks familuar.

I couldn't find any response curves to evaluate.

[sfogg]

Chops,

Can you run a curve of just the 902 (no crossover at all) run full range on pink noise at low volume?

I'm curious about its low end response. I'm wondering if your problem at the crossover is a crossover problem or if maybe your diaphragms are work hardened and rolling off the response of the driver early.

Shawn

[chops]

Charles -- I told you how to build it in the other thread, now build it. It will sound better if you use Auricaps or Kimbers.

Yes Dad..... LOL! j/k []

Maybe I'll work up a parts list this weekend and come up with a total on what it will cost me. I'll have to get the newer style T2A's from Bob. Which one do you recommend, the 3619 or 3636?

I am definately going 2-way for now. What I want to do is get the crossover point for both the K33 and 902 to 500Hz I think.

Thanks for speakerfritz and the link he provided, the guys on that other board say it's a huge no-no to run the 902s down to 500Hz, at least with a -6 or -12dB filter. I am running them at 375Hz at -6dB!!!

NOTE: Between the above paragraph and the one below, I just made changes to the networks!

However, as a precaution, I just removed the 3uF cap from the 902 and the 68uF cap from the K33, moving the crossover points of both back up around 600Hz. To my amazement, this actually sounds very good! The lower midrange obviously has a little more "meat" to it now since the K33 is reaching a little higher up in the range. As for the midrange from the 902, it sounds just about the same as before. The added "oomph" from the K33 is actually a major improvement over just a few minutes ago with those two caps still installed.

I'm now a little confused on what I'm going to do for the new networks. The way these two small changes sound, I think I might just make a simple 2-way based on what I have right now, with crossover points at 600Hz for both drivers. However, should I have both 1st order, or should I bump the 902 up to 2nd or 3rd order and leave the K33 at 1st order?

Also, which autoformer offers the ability for finer tuning of attenuation? I think I might have to knock the 902 back just an extra dB or so more, but not necessarily a full -3dB. Then again, maybe I don't need to at all. I just figured I'd put that question out there anyway, jsut to be on the safe side.

Charles

[chops]

Chops,

Can you run a curve of just the 902 (no crossover at all) run full range on pink noise at low volume?

I'm curious about its low end response. I'm wondering if your problem at the crossover is a crossover problem or if maybe your diaphragms are work hardened and rolling off the response of the driver early.

Shawn

Shawn,

I don't think I'd feel comfortable attempting that. I don't want to possibly damage these drivers. I hope you understand. []

Charles

[sfogg]

"I don't think I'd feel comfortable attempting that."

Keep the volume low and you will be putting in less power then you would running them loud through the crossover.

http://forums.klipsch.com/forums/thread/276842.aspx

Shawn

[chops]

BTW, here's a few updated pics of my Alcorns!

[Guest " "]

 

Charles -- I told you how to build it in the other thread, now build it. It will sound better if you use Auricaps or Kimbers.

 

Yes Dad..... LOL! j/k []

Maybe I'll work up a parts list this weekend and come up with a total on what it will cost me. I'll have to get the newer style T2A's from Bob. Which one do you recommend, the 3619 or 3636?

I am definately going 2-way for now. What I want to do is get the crossover point for both the K33 and 902 to 500Hz I think.

Thanks for speakerfritz and the link he provided, the guys on that other board say it's a huge no-no to run the 902s down to 500Hz, at least with a -6 or -12dB filter. I am running them at 375Hz at -6dB!!!

NOTE: Between the above paragraph and the one below, I just made changes to the networks!

However, as a precaution, I just removed the 3uF cap from the 902 and the 68uF cap from the K33, moving the crossover points of both back up around 600Hz. To my amazement, this actually sounds very good! The lower midrange obviously has a little more "meat" to it now since the K33 is reaching a little higher up in the range. As for the midrange from the 902, it sounds just about the same as before. The added "oomph" from the K33 is actually a major improvement over just a few minutes ago with those two caps still installed.

I'm now a little confused on what I'm going to do for the new networks. The way these two small changes sound, I think I might just make a simple 2-way based on what I have right now, with crossover points at 600Hz for both drivers. However, should I have both 1st order, or should I bump the 902 up to 2nd or 3rd order and leave the K33 at 1st order?

Also, which autoformer offers the ability for finer tuning of attenuation? I think I might have to knock the 902 back just an extra dB or so more, but not necessarily a full -3dB. Then again, maybe I don't need to at all. I just figured I'd put that question out there anyway, jsut to be on the safe side.

Charles

"""I think I might just make a simple 2-way based on what I have right now, with crossover points at 600Hz for both drivers. However, should I have both 1st order, or should I bump the 902 up to 2nd or 3rd order and leave the K33 at 1st order?""""

YES, seperate new xover.

possible options

a. 18db per octave on both LF and HF

b. Folks that like the AA sound, might prefer 18db on the HF and 6db on the lf

c. 12db per octave if you corssover 800hz or higher....a can't do for you with the k-33.

d. 6db per octave....only if you are using good equipment and promise never to crank it up.

remember 18 db per octave means

1. lf = in-line indcutor, capcitor to ground, in-line indictor (woofer inductance should be subtracted from the value of the second inductor)

2. hf = in-line capacitor, inductor to ground, in-line capacitor

use one of the crossover calculators...yes I know they do not work....but you need to start somewhere.

the issues about the device to use for level adjustment have been introduced earlier in the thread...so i will not say the "a" word (s).

Also, there is a document on Al's web site. I think it's called a case for extreme slope networks. in that document, I think he mentions trying to use the 511b in a two way, and how/why he evolved into a 3-way.

about the 375 hz xover point. tweeter imagining will suffer greatly. the driver motor assembly can not let go of the voice coil fast enough to prevent interfering with upper frequencies. the higher you crossover a tweeter, the clearer and more detailed the imaging becomes. in a 2 way limitation is the upper range of the k-33. now we are getting into 3way dynamics. If you had an electro-voice 15l , 15b, or evm series, the crossover could be rasied higher than that of a k-33 in a 2-way application. of course at the expense of the low end reproduction.

[Deang]

I agree. Also, if he stays first order -- he should probably get some loading caps for those drivers.

Good find on that thread on the Lansing forum.

Dennis -- you out there? I'd love to hear your take on this.

[Guest " "]

I remember in 1986, I had a simular experiment going using a set of altec horns I got out of a theater.....the drivers were huge. Anyway I rigged them up to sound awesome using an unprotected 6 db per octave network. corssover was around 600 hz or 800 hz. i promised my self not to crank them until I finalized everything. While at work, I got a call from my wife, who said, honey, I was vacuming and cranked up the stereo so I could hear music while I clean....now the speakers sound funny.

Yes, she blew both drivers.

[chops]

"about the 375 hz xover point. tweeter imagining will suffer greatly.

the driver motor assembly can not let go of the voice coil fast enough

to prevent interfering with upper frequencies. the higher you crossover

a tweeter, the clearer and more detailed the imaging becomes."

Fritz,

Am I understanding this correctly? You're saying that because the 902 driver was crossed over at 375Hz, I was robbing the 902 of reaching the higher frequencies?

Is that why every CD I play now since I changed the crossover points back up to 600Hz has decent treble, even beyond the limits of the alnico K77s?

I really am noticing that these drivers are reaching higher that before, which is a very good thing.

---------------------

Dean,

You agree to what?

Also, as far as I know, these drivers DO have loading caps. The "B" series were supposed to come with them, as well as with the tangerine phase plugs, which these drivers DO have.

A little history of these drivers and horns....

The Altec 511B horns were made in the early 1980's and were pulled out of an old movie theater in Atlanta, GA.

The Altec 902-8B drivers were built in the 1st week of May, 1983. They were used in the rear surround speakers of another old movie theater. They were decommissioned only a few months ago.

Charles

[DrWho]

Am I understanding this correctly? You're saying that because the 902 driver was crossed over at 375Hz, I was robbing the 902 of reaching the higher frequencies?

Is that why every CD I play now since I changed the crossover points back up to 600Hz has decent treble, even beyond the limits of the alnico K77s?

Wouldn't another measurement show this if it were the case?

[chops]

Am I understanding this correctly? You're saying that because the 902 driver was crossed over at 375Hz, I was robbing the 902 of reaching the higher frequencies?

Is that why every CD I play now since I changed the crossover points back up to 600Hz has decent treble, even beyond the limits of the alnico K77s?

Wouldn't another measurement show this if it were the case?

Yes, most likely it would. However, it's almost 2AM, and I'm pretty sure my brother in the next room sleeping wouldn't like hearing pink noise blasting through the house at +90dB! LOL

I'll probably do some more tests tomorrow after work. []