New A7's

[LowOhms]

Hi guys,
I have been lurking on here for a while and reading some of the knowledge that is accumulated in this board. I have just gotten myself a pair of A7 voice of the theatres. They have 416s on the bottom N 501-8 crossovers 511 horn's and 909 drivers. I just noticed that the one 909 driver seems to have a little bit of static distortion around some of the high-frequency notes. Any ideas as to how I can fix this? also how do I reinforced the midbass horn flare? And I have an Ashley active crossover Will that be an upgrade over the 501 passive? also does anybody have a schematic for a better version of a passive? Or if I'm sticking to the passive route should I just replace the components with newer versions of the same values? Thanks in advance for any help, I apologize for all the questions.

Hello,

I commented on another post in this thread, on trouble shooting / finding the treble distortion.

There are pros and cons, active and passive.

I will discuss crossovers from "my" perspective, which is " theoretically " to obtain the highest possible fidelity. So friends, this is written only IMHO :

(1) Avoid active. It adds an un-necessary line stage to the audio electronics. It, like a passive, also uses caps, etc to get the roll off in that line stage. Why add an un needed stage??? KISS rules.

A second problem is that when biamping IDEALLY, one should use two amps of exactly the same design, on the top and bottom, hopefully a zero feedback design to keep the music intact. MOST all active biampers I see do not do this and there is an audible discontinuity between differing amps IF the system is executed at the highest level. .

(2) Optimize the passive crossover. Optimize every aspect of feeding a signal to the A7, from the amp to crossover, system wiring, the crossover itself, pick a frequency, and use GOOD parts, and optimize it.

Then use a single highest-possible-quality no-negative feed back mono amplifier on each channel, to run the whole shebang.

- - - - - - - - - - - - - - - - - - - -

This is ONLY my opinion, but optimized passive is how I would suggest one do it for the best possible " ultra fi" result.

BTW, a very conservative alternative to internal bracing is mass loading, its very inexpensive, its totally reversible - which keeps the enclosure original, and has benefits bracing alone does not provide. YMMV, yada yada.

Have fun. There are lots of people who will want to assist you, and opinions differ.

Low Ohms.....Jeff Medwin ( A7-800 VOTTs, 515B, 802D )

[Earl K]

One needs to keep in mind that if the plastic phase plug has become unglued ( an excellent source of distortion ), then a simple dcr test won't illuminate that as a problem.

These plastic phase plugs ( in the 900 series drivers ) do let go from time to time .

Gently shaking the driver ( off the horn ) & listening for rattles will give an indication of a loose phase plug ( as will removing the diaphragm for a visual inspection ).

[LowOhms]

One needs to keep in mind that if the plastic phase plug has become unglued ( an excellent source of distortion ), then a simple dcr test won't illuminate that as a problem.

These plastic phase plugs ( in the 900 series drivers ) do let go from time to time .

Gently shaking the driver ( off the horn ) & listening for rattles will give an indication of a loose phase plug ( as will removing the diaphragm for a visual inspection ).

Good point Earl ! Liked that post.

You know, from the " human " aspect, many brand-new owners will be afraid, or not confident, to touch it, let alone open - up a high frequency driver.

[Elitopus1]

Everyone has to start somewhere. Take the plunge!

[mah]

Analoglvr, here's how: http://www.greatplainsaudio.com/SmDrvrDiaRpl.pdf Note the caution message.


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.

[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.