chops

Bob, I didn't mean anything about different caps "adding" to the sound, but rather better audio grade caps possibly passing a little more of the treble information from the original signal. I'm not doubting anyone here (you can be certain of that), and I'm not bashing components or designs, but motor run caps weren't design for audio use, and I'm pretty sure my Altec 902-8B drivers are not 3-phase motors. Is it possible to measure the frequency response of a capacitor to see if it might have a slight rolloff on the extreme top end? Dean, I do not want to go with a seperate tweeter again. I really like the results I'm getting with this 2-way setup, and want to see if I can improve on it, if only a couple of extra dB on the extreme top end. The top end is there, I can hear it right now, it just needs to be pulled out front a tad bit to blend nicely with the great midrange. In fact, giving the +3dB boost via the tone controls at 10kHz almost gets me there, but I'm sure it would sound much better if I were able to get that boost at say 15kHz instead of at 10kHz. And I have to say, since moving over to a 2-way with these Altec drivers and horns, I have NEVER heard speakers this large (Cornwall/Altec combo) image and soundstage so good like these are doing right now. I was not getting anything close to this with the 3-way setup. And if I can get the treble to come out and play nicely with the rest of the music, the imaging and soundstage can only open up that much more.

Hello Erik, Well since I've had a couple days now to listen to the 902s at the new 600Hz crossover point, with a bunch of different music, I don't think I have to attenuate the 902s any more than they already are. They actually blend in quite well with the K33s. However, I still have the need to boost the treble +3dB, but I can live with that for now. Thanks for the offer on the L-pads, but I seriously don't think I'll be needing them. ---------------------------------------------- I have been told by several members on the Altec User Board that removing the loading caps not only improves the midrange, but also the top end, giving them a little more "air", even moreso than removing the bug screens. I have no plans on removing the screens. With 5 cats raoming around the house all the time, I certainly don't want any kittie fuzz getting in there. LOL Also, am I correct in thinking that by building new networks with Kimber, Theta, Mundorf, etc caps and the new 3636 or 3619 autoformers, I might get a little extra sparkle on the top end as well? Charles

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. []

"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

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

Yes, thanks Bob. However, I'll have to read it at a later date as I am starting to doze off while reading it now. [:$]

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

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

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.

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... [:^)]

Everybody just ignoring this one, huh? Oh well.

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?...

Duke, I see you mention the dbx DriveRack. I went to their site to check "it" out only to find there's like 8 or so of them to choose from! Which one are you referring to? Also, what's so good about these DriveRacks over other parametric EQs? Any quotes on prices? Thanks, Charles

So.... If I go back to using the CT125s, what should I cross them over at?

No one is playing anything with you. It doesn't matter that the tweeter wasn't going through the autoformer. As you can CLEARLY see in Bob's plot, eventhough the squawker is attenuated throughout the entire range a few dBs, it does NOT drop lower at the top end of the range. IOW, it is NOT rolled off on the top end at all. It's really not that hard to understand. And unless you want me to cook Al's tweeter attenuator on the midrange, it's not going to work for me.

Charles, Glad your starting to like the combo.When you said yesterday that they seemed a little to rolled off I thought to myself he needs to give it some time.The sound is different from what you are used to.You might have to adjust the position of the 511's to maximize the sound.The one driver covering so much territory probably has a different dispersion into the room(highs).I would be curious to see on/off axis measurements.In my system off axis does fall off but if Im not on axis then I am not ctiticaly listening.There also seems to be more roll off in the vertical vs. horizontal plane.That might have more to do with the position chosen for my 511's which are now about 60" in height and pointed down to the sweet spot 12' away. Greg Greg, Actually, that Madonna CD is recorded fairly bright, so the 902s sounded pretty good. Now with other CD where they "should" sound right, the 902s are rolled off a little too much. To be honest, they sound more like the K77s BEFORE I replaced the old caps. I should kill myself for even doing it, but I'm using tone controls! YUCK! I have the treble turned up to +3dB, and it sounds better. However, the thing that sucks most about it is that the treble control is centered at 10kHz, where I DON'T need boosting. So I'm stuck at either staying 2-way and getting a parametric EQ to gently boost from about 15kHz and up, OR go back to 3-way and use the CT125s again to fill out the spectrum. Most likely, I'l go with the tweeters. [*-)]

Well, after listening to these 902 drivers for a while now, I'm really liking what I'm hearing. Their top end kind of reminds me of the alnico K77s, except a bit more refined. Last night, I played Madonna's latest CD, and I have to admit, these Altec drivers/horns did an excellent job. I was running the system at a sustained 101dB in the sweet spot, and I was very impressed and pleased with the sound. Even my "other" brother who isn't to fond of horns said that he really likes this combination. He said "Finally, a set of horns that don't chase you out of the room!"

Radios? Tuners? What are these strange things you talk about? [] The last two HT receivers that I bought, including this Pioneer Elite I have now, I wouldn't have the first clue if the tuners in them work or not. Same thing goes for the Clarion headunit out in my Miata. When I installed it, I conveniently forgot to connect the antenna. I hate hearing the dang radio on at work. Every stinking morning I have to hear those idiots MJ & BJ jabbering away for hours on end, yacking over the music, and then all of the stupid commercials. BTW, I feel the same way about TV as well.

Don't worry Greg, I'm sure someone here will snag these up before too long. []

Since the K55 was connected to tap #3 and gave me a 64 ohm load, that's why I am now using tap #2 with the 902, it still gives me 64 ohms. Still, most of this stuff is greek to me when only reading it. I usually need "hands-on" to really take hold of the whole concept. Once I get a hang of it though, watch out, cause I'll be going like crazy trying to learn new ways and get more involved in the whole deal. Once I find a genuine interest in something, I learn all I can about it and go full steam into it. Hence the reason for asking all of these dang questions. Thanks Dean! [] Charles

I guess the 6th time is a charm! LOL Again, exactly what I was thinking. It's like turning the volume up or down on a preamp/receiver. The entire range changes SPL at the same rate, not just one part of it. ---------------------- All if this reminds me of a little saying my father always says... "Some people just know enough to be dangerous."

Yeah, that's true. Thanks Bob for the reassurance. []

Bob, I kinda figured that as well, but didn't want to admit it. LOL A lot of mics that I've seen have this same problem though. What other mics are out there at a decent price that can be used? Charles

Thanks for clearing that up Bob. Honestly, I didn't think the T2A was the problem either since it has had the squawker and tweeter connected to it for the past 27 years, and after installing new caps and your CT125 tweeters, there was plenty of treble. However, from all of the measurements I've been taking lately of the system, there is a consistant -3dB drop or so from 18kHz and above. And all of these measurements were taken with the tweeters front mounted, per yours and Deans recommendations. This plot shows the fullrange output of the left speaker at 1 meter distance. (pre-Altec 902 drivers)

Hmm, interesting. You learn something new every day. Well I do anyway![][]