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In Reply to: RE: This topic is very confusing posted by Carl G on July 25, 2015 at 08:59:24
The reason there's differing opinions is because there's differing opinions. Sorry about that, but this is not an uncomplicated black/white issue. :)
The primary (I think everybody agrees with this) issue is the suitability/safety of the ribbon tweeter if connected directly to an amplifier.
The priority is as follows:
1. Use an amplifier that is extremely well behaved at turn on/off and exhibits no DC offset.
2. Make sure devices upstream of the amplifier make no transients that might pass through the amplifier on power failures.
3. Protection capacitor. (distant third.)
4. Protection device like a fuse. (extremely distant fourth.)
If you're not comfortable with any of this, I would suggest to leave the internal crossover in place and bi-amp instead.
Dave.
Follow Ups:
Not to confuse the OP more I would derate items #3 and #4 from "distant" to pretty much useless. We have discussed #4 (fuses) in the past and I think the consensus is that a standard fast-blow fuse is useless. A polyswitch is preferable but the choice is not a simple 1 for 1 swap for the fuse. A RXEF110 (1.10A) or perhaps less would be a reasonable choice (available from Parts Express for $1.50) for the tweeter but only protects from overvoltage. However, the same protection could be had by maintaining sane listening levels.
As far as #3 (cap), I fail to see how this is going to help very much. The cap will block steady dc but is useless against high frequency overload caused by clipping. Also with on-off thumps even though the signal may be dc it is not steady state but transient and the cap will not block the signal -- it will only charge up and then discharge through the ribbon. The larger the cap the better at blocking dc and lower frequency signals (2 or more octaves below the -3db point of the HP filter) but then more energy is stored (and released). Smaller caps will still block dc but then the crossover frequency and slope are altered and the design of the crossover needs to be reconsidered.
My suggestion is to follow items #1 and #2 - a well-behaved amp with no thumps and no dc offset. FWIW, I use a class D amp which has an idle power consumption equivalent to a night light and leave it on all the time.
Regarding point # 3 for capacitor.
Based on Neolith's work up for triamping, he suggested a Xover point around 1580 Hz. Two questions. 1)What size cap would is suggested , even for minimum protection, and 2) May I assume that a higher end cap such as a Mundorf Supreme would be giving me better sound than a lower audio quality cap in this application (dont want to open a can of worms on cap quality)
Thanks for the direction.
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