chops
-
Posts
1532 -
Joined
-
Last visited
Content Type
Forums
Events
Gallery
Posts posted by chops
-
-
Charles:
On the finer control of attenuation: A variable L-pad, selected to match the impedance of the driver, will work well for this application. I have great respect for Mr. Klipsch, and I understand his preference for a multitapped coil, but many speaker companies use resistive L-pads in their networks. I'm sorry, but I have used both over lots of years, and recently installed a switch on my autoformers. The difference in sound is not detectable to me -- at least as far as my acoustic memory goes, which I admit isn't far. It's a common practice, though. If you need finer adjustment ability, the autoformer as setup is not going to give that to you. The jumps in attenuation are rather course IMO, compared to what is available with a variable control that still maintains a constant impedance.
I have two I"m not using you could experiment with, but I don't know the impedance of the driver you're using.
If you didn't like it as well as the autoformer in terms of sound quality, it's something that, like anything else, does not have to be permanent.
Erik
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
-
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. [
] -
"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. [:$]
-
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
-
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
-
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.
-
"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... [:^)]
-
"Ah, Bellamy, for cryin' out loud. That's the the stinking, most awful,
stupid joke and you're always pullin' that stinking awful stupid joke.
You don't want in this thing, you don't get in this thing. I cut you in
on everything. I don't need you. Sixty feet of bridge I can get almost
anywhere. Schmuck!"
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?...
-
Now .... I haveta admit ...
the passive JBL 4430 X-over, sounds bettern' electronic
but, for what we are talkin' here , things are easily changed by goin' to, say , a DriveRack ...
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?
-
Sounds like you just tried a hand of the old shell game with me. Consider yourself caught. Why would I compare the green to the red. Green is squaker going thru the autoformer, red is tweeter not going thru the autoformer. It would be intresting to see the same graph with a red line showing tweeter going thru the autoformer and a green line showing tweeter not going thru the autoformer.
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.
-
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!"
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. [
] -
The reason your values aren't coming up right is because you aren't accounting for what the autoformer is doing to the impedance your amplifier sees. The first cap coming off of your input is called the primary cap, or highpass cap, and it goes to tap 5. The value of the cap is determined by a combination of the high pass crossover point you want along with the impedance that the autoformer is reflecting back to the cap from the output side. That is -- whatever tap the midrange is hooked to. It works like this:
Tap 4, the impedance of the squawker x 2
Tap 3, the impedance of the squawker x 4
Tap 2, the impedance of the squawker x 8
Tap 1, the impedance of the squawker x16
If you are off of tap 3 with a 16 ohm driver, the reflected impedance back to the primary cap position is 64 ohms. So, if you need to calculate for something on the input side of the autoformer, you need to make sure you have the correct impedance.
Now we do the output side: Taps 1-4 are output taps. These taps sit between the driver and autoformer directly. Anything you calculate here is based on the raw impedance of the driver/horn -- and you do not have to scale. When you use the calculator, you will have to do calculations twice. The first time will be to get the highpass value at the higher, reflected impedance -- the second time will be to get your low pass inductor value for the squawker bandpass -- which resides on the output side of the autoformer (16 ohms).
Notice that the calculator factors in the reactive component, and also will not let you create any filters that are less than three octaves apart.
A couple of things you will eventually figure out by playing with it is that 1) the Klipsch networks are based on 15 ohms and multiples thereof, and 2) there has never been a 6000Hz "crossover point."
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
-
Wow, We heard you all ready.
I guess the 6th time is a charm! LOL
Yes, the job of the autotransformer is to attenuate. But it attenuates
linearly. Set the tap for 3 db and it will attenuate the entire audio
range 3 db. Not more at higher frequencies.
Bob
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. [
] -
Chops,
I found part of it for you.
Bob
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
-
speakerfritz said "the rolling off at the top you are noticing is probally due to the squawker autoformer you are using. The autoformer was not desinged to pass high frequencies to a tweeter."
That is not the problem. The T2A is in fact meant to attenuate either a tweeter or squawker or both. It is good to well over 20 khz.
Bob Crites
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)
-
It seems sort of incongrueous, but its true.
The problem is caused by higher potential output capability from the larger driver going through too small of a throat and the resultant throat overload distortion.
The smaller driver in a larger horn doesn't suffer from that but rather diffraction effects in the horn, causing distortion which has nothing to do with the output level.
It would be best, of course, to use a matched combination, but there are times when some prefer larger diameter drivers with greater power handling capabilities in smaller sized horns for better dispersion characteristics and more control. It depends on the application.
I think it was on the Decware website that was touting a particular 2" driver on a smaller horn as being the cat's meow - they said it sounded better.
Hmm, interesting. You learn something new every day. Well I do anyway![
][]
]
It will sound better if you use Auricaps or Kimbers.
]
Altec 902-8B/511B Reunited!!!
in Technical/Restorations
Posted
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.