GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Midbass impedance bumps -- why and what to do?

Post Subject: Useful findings.Posted by noviygera on: 10/25/2010

Romy,

Thank you again for a helpful reply. Your comments are very appreciated inspite of not suggesting what to do. I will figure that out myself. And here is what I've learned so far:

>> Herman, if you use Precision Devices hen you are at mid-high 90 sensitively, I am right?

Actually the driver is, I believe, a custom made 10" mid by PD (looking at the magnet and model markings) for Funktion One. It has almost no excursion, maybe 0.5 mm, paper cone, Fs of about 180Hz, 109db sensitivity (in the horn), 12 Ohms. Very fine sounding horns.

Back to the Edgar midbass. I did talk to Bruce Edgar per your suggestion. First off, he is a good person to talk to, I believe very honest and trustworthy. I'd like to thank him and express my respect. He talked to me for about one and a half hours.

1st problem:
the amp I was using. Per B.Edgar's recommendation I changed from Spectron digital amp to Dynaco St-70 to power the 80Hz horns. Much better sound, at least much more tolerable to listen to for longer than one minute. I will continue to analyze the sound I am hearing, but with the Dynaco, the 80Hz horns may be actually useable and worth experimenting to improve the box structure. I cannot believe how much the sound changed in a good direction. I would NOT say it is no longer muddy sounding, but at least it does not pierce the ears like it used to!

2nd problem:
Inheritant design compromise (size). It may be possible to extend the flare and increase the mouth size. Also, this can be solved by using a different, properly shaped/sized midbass horn.

3rd problem:
Enclosure resonances. The problem is in the horn flare being excited near the mouth area. It is definitely an issue. I thought it was originating in the back chamber but it is not. I removed the chamber, ran a sweep test and the impedance bumps were still there, just moved lower.

Question, Romy:
Why do you suggest to add the extension on the back, not the front, as B. Edgar suggested. He specifically commented that the MOUTH area is too small and said the throat size was OK?

Thank you,
Herman

Rerurn to Romy the Cat's Site