Biamping seperates

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cwahls@uiuc.edu - 19 Apr 2004 18:18 GMT

I just purchased a MTX 5 ch amplifier and can't resist the urge to
biamp my ADS AL6's. I have just a couple questions for those doing
this now.

1. The amplifier has no provisions for a bandpass config for the mid
woofer, should I try it and try to match the tweet to the natural
rolloff of the woofer or should I calculate the value and purchase a
HIGH QUALITY inductor to roll off the highs a bit.

2. Is anyone putting a cap in series with the tweet to guard against
DC if the amp were to fail. My tweets are out of production and I
would like to protect them. What value are you using? I want to go
large to prevent it from acting as a crossover, just DC protection.
Any brand reccomendations? I want something of quality as to remain
transparent to the intended audio path.

Thanks for your time,
Chad

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MZ - 19 Apr 2004 18:27 GMT

> I just purchased a MTX 5 ch amplifier and can't resist the urge to
> biamp my ADS AL6's. I have just a couple questions for those doing
[quoted text clipped - 4 lines]
> rolloff of the woofer or should I calculate the value and purchase a
> HIGH QUALITY inductor to roll off the highs a bit.

There are two problems with this strategy. First, it's not adjustable.
This is the main reason for biamping. But by adding passive components,
you're losing that feature to some degree. Ideally, you should probably
look at getting an external adjustable active crossover, even if it's just
for providing this low-pass. If you shop on ebay, you should find a
reasonable deal (ie. under $50).

> 2. Is anyone putting a cap in series with the tweet to guard against
> DC if the amp were to fail. My tweets are out of production and I
> would like to protect them. What value are you using? I want to go
> large to prevent it from acting as a crossover, just DC protection.
> Any brand reccomendations? I want something of quality as to remain
> transparent to the intended audio path.

Yes, this is a typical strategy. Just use one that's below the crossover
point of the tweeter, but at the same time not so low that it has a high
ESR/ESL which could attenuate the high frequencies. Any decent cap will
suffice in this regard.

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Peter Klein - 22 Apr 2004 21:39 GMT

Do you really think you will hear a difference by bi-amping component
speakers which are very small? Tweeters need fractions of a watt to play
their limited high frqeucies and midrange only use a few watts. Subwoofers
require lotts of wattage to play because they are ver large drivers. P.

> I just purchased a MTX 5 ch amplifier and can't resist the urge to
> biamp my ADS AL6's. I have just a couple questions for those doing
[quoted text clipped - 14 lines]
> Thanks for your time,
> Chad

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MZ - 23 Apr 2004 00:01 GMT

> Do you really think you will hear a difference by bi-amping component
> speakers which are very small?

Biamping is usually done for adjustability (ie. level control and crossover
settings) purposes, not power purposes.

> Tweeters need fractions of a watt to play
> their limited high frqeucies and midrange only use a few watts. Subwoofers
> require lotts of wattage to play because they are ver large drivers.

This is demonstrably false. While it's true that the bulk of the energy is
in the lower regions of the spectrum, it's not nearly as skewed as you're
suggesting. In general, typical music can be approximated with the 1/f rule
[or thereabouts...for a lot of rock and pop music I've analyzed, it tends to
resemble something closer to 1/(f^3/2) starting anywhere between 50 and 70Hz
on average]. That is, a very rough approximation of how much power you need
for your sub, mid, tweet, etc can be obtained by calculating the percentage
on a cumulative log curve.

I've been working on refining this idea and putting it up on my web page,
but progress is slow because I don't have enough time to devote to it. But
currently, the best approximation on the net that I can find is here:

http://sound.westhost.com/tweeters.htm#pwr-dist

According to this figure (which, by the way, I don't entirely agree with,
especially in a car environment, but it's a decent approximation
nonetheless), roughly 15% should be devoted to the tweeters.

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