Well, I finally have the Model 19's that I acquired in March up and running with the correct parts. I installed the Great Plains diaphragms around a week ago and have been playing with them ever since.
As a quick recap, when I first got the speakers, neither compression driver was working since the tinsel leads had snapped on both of the diaphragms. It took nearly three months, but I finally got replacement diaphragms. In the interim, John of our forum, was kind enough to let me use a set of Symbiotic diaphragms.
With the Symbiotic diaphragms, the sound was not that good. HF was really lacking. The mids were piercing and somewhat raspy. Obviously unrelated to the diaphragms, the bass was boomy and not very extended. Fortunatey, I was able to rectify much of this with a parametric equalizer. After much playing around, I managed to get a sound quality that was at least acceptable.
When I took the speakers apart to install the new diaphragms, I decided to relocate the system. Orignally, they were in the same position as my previous primary speakers, a pair of Dahlquist DQ10's. That is to say, that they were in the corners of a 13' side wall. Since the DQ10's are notoriously bass shy, the corner reinforcement really helped their response. However, the Altecs seemed to be suffering from that positioning.
I moved the Altecs to the long wall (23') with the closest speaker to a corner being about 5' away measured from the center of the woofer. With the new diaphragms and new positioning, the speakers took on a whole new life. Bass response was no longer a one note boom. It's now apparent that the corner placement was exciting room modes in addition to gaining boundary reinforcement. The new diaphragms are much smoother through the midrange and have very good HF extension.
The mids are still too pronounced for my liking, and I find this a characteristic of every Altec horn speaker I have ever listened to. Kicking down a peak centered at around 3khz with the parametric eqaulizer does wonders for this. I find the speakers still need an extreme LF bass boost at around 40hz to counteract the natural rolloff of the woofer. With just these two tweeks, the speakers sound marvelous.
They're still not as neutral sounding as my DQ10's and they don't quite match the holographic imaging, but to my surprise, they are not that far off at all. More significantly, the Altecs have an ease of dynamics and lack of stain that the DQ10's could never hope to achieve. They are just outright toe tapping fun to listen to and this is something I have not experienced in many years.
Reply With Quote
