Squaker measurments

[sfogg]

Gil,

"One issue is that we're not seeing all variety of the drivers and not on a K-400.  "

I don't have an adapter for the Altec driver for the K-400. When I get a chance I'll run the two K55s on the K400. I doubt that will effect the high end glitches of the drivers though. I haven't bothered trying the K400 as I much prefer the 511.

" One suspicion is that they've switched over to a bandpass for the midrange. "

The normal ALKs do this too. Some of the comments on it talk about 'taming' the K400. This might be from attenuating those peaks.

The attached is the 902-8B driven through the ALK. In this one the mic is actually in the horn itself as the tweeter and woofer were still active and I just wanted to measure the midrange.

The background green trace is the 902 run full range. The blue is through the ALK.

Shawn

[sfogg]

This is the K55v on a K400 mounted in a La Scala. Run full range and measured with the same setup as before. The mic was a few inches from the mouth of the horn and this La Scala has a grill on it.

Shawn

[sfogg]

Same setup except this time the pink noise source is feeding the ALK crossover and it is feeding the k55v.

Shawn

[sfogg]

Jut because I was curious this is an Alinco T35 fed through the ALK.

Shawn

[ZAKO]

Holly crappoly The T35 RTA confirms my sweep frequency chart. Mine barely does 10k

[sfogg]

"T35 RTA confirms my sweep frequency chart. Mine barely does 10k"

This one does 10k OK but then is dropping off about there. The Altec looks like it should be able to replace the T35 pretty easily. I'll need to do some dispersion FR tests on it though too.

I also have the mud magnet version of the T35. According to, I think, one of the Dope For Hope papers it is supposed to have 2 or 3dB more output up high. They aren't at an easy place to measure them but I'll try to do that at some point to see what they look like.

Shawn

[3dzapper]

Shawn,

There apears to be a drop off in all of your graphs at the fundamental frequency of 400hz and it's harmonics. Is this a chariteristic of all the drivers or your test mike? If these dips are smoothed out all the graphs would look better. The continued output of the K55 into the tweeter range might explain the "note" I hear in my Khorns. It seems that whenever that "note" is hit it "blares" (might be too strong of a word but it works). I don't know the frequency but it is at the high end of an alto sax.

It could be the f of the tweeter combined with the K55.

As John Warren (same last name, no relation. He is of the intellegent Warrens) discussed in a recent post.

Rick

[sfogg]

Rick,

" Is this a chariteristic of all the drivers or your test mike?"

It isn't the mic and it probably isn't all that much the driver. I believe that is a function, mostly, of the horn.

Look at the K55V on the 511B (which is rated to 500hz but apparently can go about 100hz lower) then compare the same driver on the K400. It goes about 100hz lower on the K400 starting to really roll off at 300hz compared against 400hz. If I put them all on an Altec 811b they will all be rolling off around 700hz.

Of course the drivers will also be rolling off at some point to but I think the main part, at least in these graphs, is the horn.

"If these dips are smoothed out all the graphs would look better."

Of course, but since I was trying to see what the drivers were actually doing applying smoothing to them wouldn't help that. Ditto 1/12 or less measurements compared against 1/24.

Shawn

[Al Klappenberger]

Hi guys,

Here's a new can of worms to examine.

Shawn sent me one of his 902 drivers. Attached is a vector impedance plot of it mounted on the Klipsch K501 horn (Belle Klipsch squawker horn). It's a nice 8 Ohms below about 800 Hz. From there up to about 3500 Hz it really gets goofy! I think that's the price you are paying with the tangerine phase plug and the extended high end. Maybe (and I really don't know) that's why it is rated at a lower power level than other Altec (and JBL) drivers.

I will be doing response plots with it on an Altec 811b horn sometime soon.

Al k.

[sfogg]

Al,

" Maybe (and I really don't know) that's why it is rated at a lower power level than other Altec (and JBL) drivers."

Part of the power rating is because of the diaphragms in the 902. When replacing them there are a few different ones that can be used and they are apparently a trade off between HF extension and ruggedness/power handling.

Very interested in seeing your FR plots and how they compare to mine when you chart that out.

Shawn

[3dzapper]

Shawn,

Believe me I wasn't carping. I am very impressed with your work here.

Al,

Your work too.

Don't you mean the curve gets wacky below 800hz with those camel humps down there?

(EDIT)

I'm also very impressed with how the ALK flattens out the K55/400. +/-3db from 400 to just under 5k where the tweeter is under 3db down if crossed over at 6k with a 6db/octave slope. I bought one of those parts set-ups from Shawn today I wanted two but our emails didn't mesh. So I have to round up the parts for another.

Rick

[sfogg]

Rick,

"Believe me I wasn't carping."

I know. Some of these measurements look pretty bad compared to what you might see elsewhere. But a good part of that is because the curves elsewhere have been 'massaged' to make them prettier. If the dB per division were greater that would flatten everything out and if it was 1/3 octave that would too.

"I'm also very impressed with how the ALK flattens out the K55/400. +/-3db from 400 to just under 5k"

When I get a chance I'll do the same thing with the K55M. Based on its measurements on the 511b I suspect the area between 4-6k will be a little more inline with the rest of the spectrum. Making the squaker crossover a bandpass certainly cleans up the nastyiness of the K55v above 6k. BTW, some of the difference in the midrange there could be because on the K400 tests the mic was not in exactly the same position for both tests.

BTW, I packaged up your parts tonight so that should go out tomorrow. All the regular parts are exactly as Al specified. For the smaller mounting stuff and the barrier strips I'll see if I can find the part numbers I used from Mouser. There is also parts to do the poly switch tweeter protection in there if you decide to use it.

Shawn

[3dzapper]

Thanks shawn.

Rick

[WMcD]

Thanks, Sfogg, for all the good work.

I certainly agree that our curves look more ragged than what is published by manufactureres. I had a similar experience with my LMS measurements.

If I'm reading your results correctly, and my understanding of the A and AA and ALK is correct, there is something odd going on which I can't explain. Again these crossovers are just high pass. None the less, you're seeing, roughly, a 12 dB per octave in the high end.

I'll let you and Al K. comment, if you'all care to.

I know this is extra work. However, it would be interesting to see a curve of the output of the crossover while hooked up to the driver/horn. That way we could get some idea of where the variation originates.

Best,

Gil

[sfogg]

Gil,

"If I'm reading your results correctly, and my understanding of the A and AA and ALK is correct, there is something odd going on which I can't explain.  Again these crossovers are just high pass. "

The A and AA are just high pass. The ALK is band pass for the squaker. Is that the difference you are seeing?

Shawn

[Al Klappenberger]

Guys,

Here's a paste-up of the response plots of an Altec 902 and a JBL 2426H

driver on the same Altec 811b horn. The mike was about 6 Inches away from the

mouth and on axis. Both plots were done using transfer function mode to

compensate for the frequency response of the input noise. Amp was my McIntosh

MC50 Mono.

NOTE: The input levels are not the same for both plots, so sensivity / efficiency differences shown are NOT real.

The mike is an Old Colony Mitey Mike 2 and is certified flat to 10 Khz and

down about 1.25 dB at 20 Khz.

The JBL is nice and smooth but straight down hill! The Altec is much flater.

Al K.

[Al Klappenberger]

Here is the vector impedance plots of the two drivers on an Altec 811b horn.

Both of these are 8 ohm drivers, believe it or not! They are both neary 8 Ohms around the frequency of the recommended crossover, but that's about all!

Al k.

[Rockets]

Shawn, I'm a little corn'fused here. In the "902-8b.jpg" there's of only two to three db difference between 400 to 500 hz. This chart is with the 902/511b combo without a XO, correct?

The "Altec 902 Crossover.jpg" shows the same configuration, but with and with out the ALK crossover. The problem I have is now the w/o has a big notch in it in the 400hz to 500hz range. Can you explain this? I'm really interested in what you're learning here, but this puzzles me.

I have another dumb question. What kind of amp are you planning to run this with? The 902, from what I've read is rated at 15w, while the 909 (same family of driver) is 30w to 160w depending upon the measurement methods/bands used(scary). Unfortunately, the freq. response plot is not nearly as flat as the 902 you've shown, as it drops off at 5Khz. The reason for my question is for my own application, where using a low power amp is not possible.

Thanks for the help!

[sfogg]

" problem I have is now the w/o has a big notch in it in the 400hz to 500hz range.  Can you explain this?"

That might be from different measuring positions both of the horn/driver and the mic and a possible room bounce problem.

Also, so that the crossover was functioning properly I had the crossover hooked up to the woofer/tweeter in one cabinet and the squaker running on the 511b in the other cabinet. The distance between them might have been causing some cancelation near the crossover frequency.

Unfortunatly measurements are of course not perfect. What would be better is doing a lot of measurements with different mic positions and then averaging them all to get a spatial average response plot. But that takes a lot of time of course. And these being 1/24 octave also makes things look worse then they really are. I'll have to try measuring the 902 at 1/3 octave (or maybe even less) and I bet it would look quite flat.

"What kind of amp are you planning to run this with?"

Monarchy Audio SM-70.

"The 902, from what I've read is rated at 15w, while the 909 (same family of driver) is 30w to 160w depending upon the measurement methods/bands used(scary)."

Yeah, the lower power rating of the 902-8B doesn't really worry me at all. 15w is still a lot of power when you aren't going to be including hardly any info below 600hz. And this are being used in a home environment not a sound reinforcement setup so they are really going to be loafing along.

Shawn

[JohnA]

Shawn,

Can you run a La Scala bass horn curve the way you have the tweeters, but do it outside? I believe the La Scala bass horn will go up to 1000, but I'm not sure. I believe I want to set my crossover point at 600 Hz to help tame a bump I see in your graphs.