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-   -   Combining active and passive crossovers (http://www.diyaudio.com/forums/multi-way/228708-combining-active-passive-crossovers.html)

Rodeodave 26th January 2013 08:52 PM

Combining active and passive crossovers
 
As you can see in my other thread http://www.diyaudio.com/forums/multi...alization.html, I have built me a nice pair of 2-way TQWT floorstanders.
I am currently using a 2nd order PLLXO as per TLS.org | Passive Line-Level Crossover to separate high and low frequencies with consequent bi-amping. The design really calls for a 3rd order crossover, but that's hard to implement as a PLLXO.

Now my question is the following: Will adding a 1st order passive crossover at the speakers, combined with the 2nd order PLLXO, convolute to a 3rd order characteristic in total?

The woofer is the TangBand (TB) W6-623I (R_e=6.11R) and the tweeter is the TB 28-847SE (R_e=6R).
Would a 0.39mH inductance for the woofer and a 7.5uF cap do the trick if the crossover frequencies are 2.5kHz and 3.5kHz respectively (spread frequency crossover)? Should I be using a impedance compensation network for the woofer?

sreten 26th January 2013 09:09 PM

Hi,

Yes you can get to a third order function (eventual 3rd order roll-off)
but your very limited to very overdamped with cascaded 1st order.

The speaker design is poor as it has no BSC (baffle step compensation),
and BSC is the easiest thing to do at passive line level of all the options.

With equal sensitivity drivers and a typical decent 2 way the best
option for amplication is about 4 to 1, for chip amps a normal
amplifier for treble and bridged parallel for bassmid, one supply.

rgds, sreten.

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gootee 26th January 2013 09:18 PM

Wouldn't it be better to go to an active line-level crossover circuit?

Rodeodave 26th January 2013 09:21 PM

Quote:

Originally Posted by gootee (Post 3343540)
Wouldn't it be better to go to an active line-level crossover circuit?

Eventually, yes. But until I get around to building the active circuitry, the addition of an inductance and using a smaller cap could be a temporary solution.

tvrgeek 26th January 2013 10:08 PM

Quote:

Originally Posted by gootee (Post 3343540)
Wouldn't it be better to go to an active line-level crossover circuit?

No excuse. Spend $50 on e-bay for a used Behringer or DBX. It is FAR better than what the passive crossover is doing to the input of the amp. Then when you save up, build a really nice active one.


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