Active or passive filters? If passive, measure the DCR of both phragms to ensure they're fairly close.
My other thought is a weak magnet.
Any evidence of either driver being dropped or otherwise suffering an impact?
Hi,
I have had some time to listen to the 803B/291's
I find one horn goes decidedly lower in frequency than the other. Have not measured it but it is clearly audible. I am crossing these at 350hz 24db/oct. This means the output is -6db at 350hz.
I noticed when inspecting the diaphragms, that they are original Symbiotik. one had some very slight marks on it not really deep impressions. I cannot say if that is the one that is misbehaving or not. I did not mark it.
I do plan to replace these with GPA 390's since they are guaranteed to 300hz.
Any speculation why one driver would not go as low as the other?
Kevin
Nov 23 2010
Active or passive filters? If passive, measure the DCR of both phragms to ensure they're fairly close.
My other thought is a weak magnet.
Any evidence of either driver being dropped or otherwise suffering an impact?
Not all vegetables make good leaders.
Usually a weak magnet will take away response toward the top end, as the mass break point is shifted downward. If the response is inhibited on the low end I would suspect a rubbing condition, either junk in the gap or a misaligned or out of round voice coil. If this is the case you would hear it on a very low power sweep of the lower frequencies.
Hi,
Ok, here is the follow up. I measured them tonite with pink noise gen.
Response is OK.
One driver is 4-5 db lower in overall output then the other.
I re-balanced the system and they sound much better.
How much variation would you expect to see between drivers?
the Eq is Marchand active crossover 24db/oct 350/3500
the amplifiers are Glow 11 watt P-P pentode amps.
Kevin
Nov 23 2010
I guess what i was really wondering is if one of the diaphragms had been replaced at some point in time with an 8 ohm version(assuming they were both 16 ohm originally). That was the basis for my curiosity about the DCR of the coils.
Not all vegetables make good leaders.
they were changed at some time yes. both are 8 ohm symbiotik's. One reads 7.5 and the other 7.6 ohms. I mentioned one dome had a very slight narrow line depression in it.
Considering all this, I would lean torwards low magnetic strength, but I defer to those on the board who have much more experience with these than I.
Kevin
Nov 23 2010
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