Crossover advice needed

[henriksommer]

I'm working on a project with two Peerless 6½ inch HDS (without phaseplug) and a Scan Speak 9500 tweeter. I have chosen these drivers because they seem to relatively easy to work with for a newbie such as myself, yet having a lot og quality. The problem is that this combination requires for the two HDS drivers to be dampened 5 og 6 db. I have just planned for an L-pad in the woofer section, but now I have read that this is not a good idea. Any suggestions?

Thanks!

 

[pinkmouse]

Where did you read that? I would guess that 80% of speakers use Lpads, 10% have matched driver sensitiviities, and the other 10% are active.

 

[henriksommer]

I read it on a danish homepage, the issue being that an L-pad in the woofer section makes the resistors go very hot, and makes the speaker more difficult for the amplifier to control.

 

[wintermute]

I don't know the specs on these drivers but are the Woofers alone the same sensitivity as the tweeter? say the tweeter is 91db @ 1W 1M then each woofer would have to be 91db @ 1W 1M to need 6db of attenuation when paralleled I would think.

If you take baffle step compensation into account you may find that you don't need any attenuation after all (although from what I have read you usually don't need the full 6db of attenuation on the highs due to room effects boosting the lows).

The other thing is that L-Pads present a constant impedance to the crossover which should (I think) make the amp happier not strain it. Don't believe everything you read on the Internet

Of course I could be full of &*(^%

Tony. (who shouldn't post after drinking most of a bottle of wine )

 

[henriksommer]

I think I've a wrong word here - sorry... The solution that I've made so far is to have resistors both in series and parallel which should provide the nessesary damping. The issue is that I'm using 2 woofers (87.6 dB) in an MTM setup, which increases the overall sensitivity of the woofers making them louder than the 9500 tweeter (90 dB).

 

[BobEllis]

once you throw in baffle step compenation, I would be surprised if you really need to attenuate the woofer output. Don't forget that there will be losses in the crossover as well, reducing the effective woofer sensitivity.

Resistance in series with the woofer affects the system Q, so your box won't work quite the way you expected if you pad down the woofers. You might try putting the woofers in series, to reduce the gain or do a 2.5 way if you don't want to go to an active XO. (my preferred solution)

 

[henriksommer]

Thanks for the advice! I'll make them without any attentuation to begin with, and see if the baffle step compensation will do the trick. Naturally I would prefer an active XO, but I can't spend that kind of money on speakers yet (I'm married...)