Let me know when you're done with the piezos, I've also got a pair of Selenium DT150 tweets & horns in a pair of monitors that will be idle for a little while. You're not busy, right?
je
Let me know when you're done with the piezos, I've also got a pair of Selenium DT150 tweets & horns in a pair of monitors that will be idle for a little while. You're not busy, right?
je
The Crites CT125 is Eminence APT-50 on a custom T-35-style horn. I need to go look at the specs on these different models. No curve at Eminence for APT-50; it's a phenolic diaphragm. APT-80 is the same driver on a conical dispersion horn. The curve appears to be heavily smoothed, and similar to what I measure with the Crites horn:Originally Posted by jackgiff
http://www.eminence.com/pdf/apt80.pdf
I'll be asking you to send up a pair of the Altec Valencia drivers, so maybe the tweeters could ride along. Looks like I'll be disassembling a T35B to try a 2407 driver on that horn, as nobody's volunteered any from their stash of treasures.
Nobody's been able to replicate EV's curves for T35 thus far, +/- 1.5 dB from 3.5 - 15+ kHz. Maybe if it were mounted on the requisite baffle:
I calculate 6 kHz at about 2.25". 10 kHz gonna be "problematic" at 1.35".
C'mon, Tractrix fans, how 'bout a little round 90° 5, 7.5, or 10 kHz horn to mount on 1" thread-on drivers?
Who can run the numbers?
yup -- good ole D.B.K. strikes again...
Amazed I'm still alive!
Tim
Good news: No tweeter required. (Needs tweaking)
Bad news: Probably not enough sensitivity differential available (~16 dB required) to do it full passive.
Sounds good, but beams vertically, 30° beamwidth at VHF, estimated.
Cyn = no filter, Org = compensated. Red = 1/12 octave smoothing.
Similar to Shane's results with Tact:
http://audioheritage.org/vbulletin/s...&postcount=149
After considerable listening, they have a rather pleasant "throaty" coloration; I can appreciate why Altec fans like that.
Patricia Barber is occasionally able to excite the bell resonance at volume. I'd hope that wouldn't happen if the horn were secured to a baffle.
I've asked Jack to send a couple of stock drivers up here for testing. Once those arrive, I'll so some serious measurements. Clearly there's no HF happening playing the Radian diaphragm sans compensation....
hey Zilch
if you get a chance, place a bag of sand or something on top of the horn and see if you can still get the bell to ring, seems to tame most of the resonances for me....
(I am currently using an extra large freezer bag stuffed full of rice (like a good little, well short anyway, asian kid))
Glad to see the JBL cowboy is back in your pix...
He is a trademark of this site
Amazed I'm still alive!
It will help, but in my experience, not all the way. It will be interesting to see your findings. I think it has more to do with the horn being used too close to its cutoff and the horns general shape as apposed to hitting it with your knuckles and hearing it ring. I don't think thats a great test because it's not the same kind of force as a compression driver.
If you are going to use clay/putty to damp them, I found it works most efficiently on the horn lips. You won't have to buy as much clay.
Are you using a DEQX for the compensation?
I would be interested to hear your findings as you go on to see if it matched my own. Maybe a small report when you screw them down securely, if there is less ringing, ect.
Some ideas if you have time,
1. EQ
2. A higher crossover point
3. Limit them to covering 3 or so octaves
4. dampening
And see which one kills the resonance the best.
It's a passive filter I have here.
I could maybe tweak that to +/- 2 dB, but I'm waiting on the stock drivers from Jack for comparison before I do anything serious. I sure don't like dealing with those notches, either.
Does anybody know the sensitivity differential between the woofer and the compression driver/horn in Valencia? I don't think there's enough to accomplish full passive compensation without replacing one or the other.
Earl cautioned me about trying to do better passive compensation with Model 19, even, for the same reason.
I have an 802 driver that'll get me another 2.5 dB, in theory, but that's not likely enough, and not a very good solution for many Valencia owners, either.
It's not my desire or intention to redesign the system....
Ah, never mind then.
For some reason I was thinking you had a DEQX which would make the things I suggested really quick and easy to test.
Going by the old Altec brochures a 416 should be 97.5ish and the 806 should be about 104db. (1w/4ft for both) A 902 or 802 would give you a couple more.
So, 6.5 dB differential. With twice that, we could probably do someting; padding down the woofer to get it is not a good option.
Active's not out of the question, though. I'm thinking compensation filter and chip amp like is working in the system I sent Heather to try. That's less expensive than mediocre tweeters, actually.
VHF beamwidth of the stock setup is a major factor in deciding on the approach. I'll give measuring that some priority here.
I'm told that's a light-cone high-efficiency woofer good to maybe 2 kHz. Moving the crossover frequency up to 1 or 1.2 kHz and getting rid of the 811B horn would help, but that's apparently a stab to the heart of Altec fans....
- Yea that "stock" 8 or 9 db spread in just too tight to create something better than what already exists.
- This is where the "real" 8 ohm impedance of an Altec 8 ohm driver really works against the principal of effective HF compensation.
- JBLs' 6 ohm drivers ( labelled 8 ohm ) effectively add a couple more db for the network designer to play with.
- JBL typically used 93 to 95 db woofers / which also adds at least a couple more db to the spread .
- These two different variables are just barely sufficient to create the needed HF compensation for the 4430.
- One could gain a couple more db of spread by being creative with inline ( &/or termination ) resistors added to the 416-8c circuit ( ie; make it a 10 ohm woofer or use a bonafide 16 ohm Altec woofer with an 8 ohm compression driver ) .
It's now apparent why Altec did that in Model 19. The compensation is driven from an 8-Ohm rheostat in series with the woofer. See N1201-8A....
- Ahh, you noticed that.
- I remember you did voltage drives for that filter . I didn't see much evidence of the rheostat doing much to the woofer circuit .
- An inline inductor bypassed by a resistor can also be used as a form of BSC ( baffle step compensation ) / though I don't know if the values used within the N1201 actually qualify for that designation . Anyways / I prefer my 288-8Ks to my 902-8b(s)
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