Questions about using the Dayton Reference subwoofers on a passive design

[fjhuerta]

After much thought about the new design I've been working on, I finally decided against a WMTMW, and decided on an MTM with a subwoofer.

The M's are the Dayton RS225. The T is the SEAS 27TBFC.

Preliminary crossover points are 1.4 KHz, L-R 4th order from mids to tweeters, and around 150 Hz from subwoofer to mids.

According to my calculations, either the RSS265HF or the RSS315HF will work out with my current design. The 225 will actually run out of its Xmax before either subwoofer will. I'll probably get the 265 HF as soon as it's available (the subs and S/H are $100 less to Mexico than the 315!!!)

But I'm wondering. Would you do a completely passive crossover for the entire system, or would you add a subwoofer amp to the mix?

So far, the pros and cons I can find are:

Pros - subwoofer amp.

1) Easier load on the amp.
2) Easier crossover design.
3) Higher power rating.
4) Less expensive crossover.
5) Higher sensitivity.

Pros - passive crossover.
1) Complete control over crossover points.
2) No guessing about the upper crossover on the sub.
3) Possibly better sound quality due to better driver integration.

If I can get away with using a completely passive design, I'll probably go that way. I can't imagine trying to do a biamped system with the internal crossover of the subwoofer amp (I'm thinking about using the BASH PE amps).

Do you think a wholly passive approach is feasible?

[BobEllis]

Crossing at 150 Hz, you are really talking about woofers more than subs. You'll want two if you keep that XO point. The RS225 will comfortably go down to 50-60 Hz if you want to go with a single sub.

Crossing below 100 Hz really tips the tradeoffs towards active. My bias is towards all active anyway.

As for the pros listed under passive, #1 can be realized with either active or passive. You'll just have to build an active crossover and bypass any built in XO in a plate amp. There is a group buy of active crosover boards at DIY Audio, if you want to try that route. You could also use a DCX2496 to the same result.

Proper crossover design results in good integration whether active or passive.

Another thought considering your intended drivers. The 27TBFCG doesn't reach low enough for crossing to an RS225 which isn't really suitable for xo points above 1200. A better alternative would be an RS28A. Then you wouldn't even need to design your own crossover -there is a great one out there already.

Enjoy your project, whichever way you go.

[fjhuerta]

Thanks for your insights, Bob. I guess you are right. I see no real way a passive would work here - I just realized 2 225's have a lot more sensitivity than 1 RS sub, so I'd have to pad them down. And then there would be the issue of BSC... so I'd have to pad them even more.

I'm not yet ready to go fully active ($$) so I guess I won't go that way... for now. :T

[cjd]

You *really* don't want to pad the 225's down enough for this.

Active with separate amp, and cross lower, for the sub.

While you're at it, put a mid in there.

The TBFC can probably handle 1400 but will want special care in the crossover, recommending a C-E filter and 8th order LR slopes.

C

[fjhuerta]

You *really* don't want to pad the 225's down enough for this.

Hi C!

Yep, I agree. I hadn't thought about that earlier.

Meanwhile, I just got 4 W4's instead of the subwoofer... considering I (apparently) got them for $35, I'll interpret this as a sign from above that I should stick to my original plan.

Going active would cost me a lot of money... shipping and handling charges can get pretty high.