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targeteye
08-31-2015, 08:05 PM
What is a good capacitor size to run in series with an 8 ohm LE85 for testing purposes and is this even a good idea?

Thanks

4343
08-31-2015, 10:33 PM
What is a good capacitor size to run in series with an 8 ohm LE85 for testing purposes and is this even a good idea?

Thanks

Are you talking about a protection cap for bi-amping, or an actual crossover cap for passive listening? The protection cap needs to be an octave below the crossover frequency so as not to interfere with the slope, while a passive crossover filter cap _sets_ the crossover frequency.

First pick a crossover frequency, then determine the impedance of the diaphragm. With those in hand you can find any number of on-line calculators that will tell you the value of the cap. For bi-amp protection double the value that you get from the calculator.

IMO, LE85 will last forever with a 2-3 KHz crossover frequency, the closer you get to 1K, the less power it can handle. Never go below 800 Hz unless you have it on a yuuge horn!

Odd
09-01-2015, 01:31 AM
66696

(From 5234 manual)

targeteye
09-01-2015, 06:49 AM
"then determine the impedance of the diaphragm"

I want to set them up and test them with actual music. This is just for testing purposes and not in a "biamp" scenario. In terms of determining the impedance. I could measure the dc resistance but is this the correct value to use? A capacitor that will roll off at about 1200hz i'm guessing would be desirable for this purpose.

grumpy
09-01-2015, 08:32 AM
20uF or preferably smaller, don't play too loud. Use a horn of some sort.

The rolloff rate of a single cap isn't steep enough to provide much protection from lower frequencies...
(If I remember right, excursion increases with frequency f**2, capacitor only drops output as 1/f)
so one can set the crossover value conservatively, -way- overspec the driver, or live dangerously.

DC measured resistance is not generally useful for calculating passive crossover values
as the value often varies significantly with respect to frequency and how the driver interacts
with its environment (box, ports, horn, ...).

targeteye
09-01-2015, 08:56 AM
Thanks Grumpy. i'll be playing them thru h91 horns.