New A7's

[Phil-G]

Should you remove the 909 from the horn would you please measure the throat exit diameter. There is some uncertainty as to whether it is 1 inch as shown, here: http://alteclansingunofficial.nlenet...909-8AData.pdf , or 7/8 inch as in all other 90x models.

its been settled. search my posts

[mah]

Senior-moment there, Phil. The 909s are all 1 inch exit(you posted that you asked an Ebay seller to measure his 909s but I couldn't find a follow-up post).
The late 902s and 908s were said to have gone from 7/8 inch exit to 1 inch exit about 1989 according to Jim Dickenson. I can't recall this change being confirmed in the July, August, 2016 threads on the topic, i.e. no one had seen the 1 inch versions. I couldn't find an entry that resolved the exit change issue, however the most recent thread listed under View(PhilG) Forum Posts is dated August 7, 2016.
The following 8 months of threads are too many to search if you have the answer.

[Phil-G]

Senior-moment there, Phil. The 909s are all 1 inch exit(you posted that you asked an Ebay seller to measure his 909s but I couldn't find a follow-up post).
The late 902s and 908s were said to have gone from 7/8 inch exit to 1 inch exit about 1989 according to Jim Dickenson. I can't recall this change being confirmed in the July, August, 2016 threads on the topic, i.e. no one had seen the 1 inch versions. I couldn't find an entry that resolved the exit change issue, however the most recent thread listed under View(PhilG) Forum Posts is dated August 7, 2016.
The following 8 months of threads are too many to search if you have the answer.

I actually bought a pair and posted pics.

[RonSSS]

I can see the flange on the 902 drivers I'm using looking into the 811 horn.
Never measured the horn, but the driver exit is smaller.

The 900 series drivers don't use pins to locate the diaphragm. So they come apart quite easily. I also don't think they center as well in the gap as the earlier drivers.

I've had 2 of my four 902 drivers with loose tangerine phase plugs.

Ron

[Analogluvr]

Hi guys, thanks for the help so far! I swapped sides with the high-frequency arrangement and it followed the horn/driver So I took apart the driver and found the problem. The voice coil ring has become slightly delaminated in one spot where it looks like perhaps some moisture trickle down. There was also a little bit of debris in the gap. I cleaned out the gap and tried to re-center and it has gotten better but not yet perfect I can't understand why all tech would've dropped the Locating pins??! It was a perfect arrangement, it seems they have gone backwards. The holes are still there and the driver for the pins but the pins aren't there. I'm going to try using a little nail polish on the spot with the delamination. It is very small.
Regarding the exit diameter it is 1 inch. I cut away the bug screen which helps you see the actual exit hole. Perhaps some of the folks saying they are seeing seven eights are actually seeing the gasket/screen.

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I bought a analogue Ashley three way crossover and try dad today. It does inject some noise into the system. Definitely need to tweak and play with it some more. I would just try optimizing the passive crossover but I have a N 500 And everything I read says it sounds better with a higher crossover point. Maybe I should hunt down a N800. Anybody have an old crappy one they want to sell me?

[LowOhms]

You can EASILY convert a 500 HZ crossover ( stock) to an 800 HZ crossover, by unwinding some of the coils, on the inductors, to make them lower in mHY and installing a proper sized high quality film caps. to effect a 12 dB second order Butterworth Filter.

I am talking ( below ) for 8 ohms drivers now, not 16 Ohms. Calculators are available on-line to do the math, 8 or 16.

My vote is to do it at 913 HZ.

This neatly allows you to use a 4 Pin WIMA DC LINK 15 uF main film cap, bypassed with several small value WIMA FKP1 caps, to get high frequency fill-in properly ( total equals about 15.32 uF ). The chokes get unraveled till they read 1.96 mHY, and you are in business. All else can remain stock. It all fits inside the metal Altec enclosure.

I am doing that this week, for a fellow in SWITZERLAND, new to Altec. You need an L/C meter to judge the coil unwinding. Doable .

I would be so glad to see you reject an active biamp !! Just IMHO. KISS rules.

When you cut out the bug screens it allows the driver to create hot spots, that the stock bug screen avoids. If you need more high frequencies, correct the typically - faulty power amplifier and system wiring to get it, do not change the drivers permanently. You CAN now, after the fact, add external bug screens in the gasket, so all is not lost.



Jeff Medwin.....Low Ohms

[RonSSS]

Good job on finding the issue with the diaphragm.
Hopefully that fixes it.
Did you get the part number on it?
You might still need to buy a new one.

I have been having the same issue. So took mine apart. 902-8A.
I didn't see anything, so I swapped in another diaphragm from a spare driver I have.
Seems to have fixed it. I'll have to see, it is rather elusive!

To my ears removing the bug screens has been nothing but positive. I did it many years ago.

Ron

[Analogluvr]

One reason I would like to go Passive again is so that I can use my one set of good amps instead of using other amps as well.

[GM]

FWIW, my 802 ultralite coils kept pulling loose from the dome, so kept supergluing them over the decades till all tabs were done only to have a massive lightning strike pop them and the amp. At least the 515Bs seem OK, but won't know for sure till I get an amp working to test them at high power.

GM

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Yes I guess I'll have to do some more digging for the thread. Did you find a radical difference sound quality wise between running them passively or actively?

Use Google as too often I can search here for posts I know I've done and not get a single hit! Happens to me occasionally on other forums too: Google

If by 'radical' you mean different, then yes, finding that an active/passive hybrid was the best overall, though super low noise active is [was?] way expensive when I did it several decades ago.

GM

[mah]

Analogluvr, Good practical point re passive crossover and single amp.