3 way Dayton confusion..

[Beau]

Hmmm.... With all the talk of dayton rs based setups on ths board Ive totally confused myself. Im half way through building an enclosure (originally meant for a 3 way Scan combo) and think maybe I should go for a RS setup. The enclosure is approx 75litres, 11 inches wide. Is this enough volume for a rs270, 180, tweet combo,or am I better off sticking with an MTM, 225 (or180) combo??
Thanks Beau

[JonMarsh]

If you have Excel on a PC, my first suggestion would be to use that and look at the tradeoffs for yourself, because you know what your preferences and goals are.

RS270's like relatively large boxes- so do RS225's, if ported, though sealed alignments could be much smaller. How are you going to use this system? That would have a big impact on your choices.

In your shoes, I'd even consider an MTM with the RS180, tuned for optimal extension - the RS225 would have an advantage in the bottom end, but the RS180's would be easier to work with for the tweeter crossover, with a more moderate crossover frequency (say, 1400 Hz instead of 1100 or so). The RS180 MTM's I have now are pretty nice; lots of midrange detail, good control in the bottom end; don't go as deep as they could because it's only a 1 cu ft enclosure. (28 liters). With a larger enclosure, I'd tune for ~ 28 Hz with a 3" diameter port. Will have a gradual taper anechoic, should sound pretty nice in room.

The other alternative might be a three way with RS225 as the bass RS125 or RS150 as the mid, RS28A as the tweeter? It's just that the crossover gets a lot more complex and "interesting" to design for a three way. If going that later route, I'd consider emulating/Kloning the Joseph Audio RMSi33. But then if it was my project, I'd be tempted to do something like a Wilson Sophia, with the RS180 on the "midrange" chores, and the RS270 for the woofer. Might need a bit bigger cabinet though, unless sealed with a cutoff a bit higher up is OK. Again, that's not a cheap crossover...

Lots of possible ways to go- I'm sure others will chime in with their ideas. Do you have measuring gear?

~Jon

[Beau]

No, hence my unsurity (is that a word?) How big an enclosure are we talking for an mtm rs 225? The 3 way does appeal to me, but without a proven design im in the dark...

[cjd]

There are designs floating around for 3-ways with both 270/180/28A (WWMTM) and 225/150/28A (WWMT) not to mention 225/28A (MTM) and others. They may shed a little light on things.

A pair of 225's in 75L heavily stuffed and a passive crossover (i.e. there is some series resistance to account for) will probably have an F3 around 50Hz. Q of .62 - stuff lighter and the Q goes up.

On the other hand, a single RS225 tuned to 22Hz has an official F3 of 28Hz but in-room will extend low quite nicely. It has a very nice bottom roll-off that Jon would like. You're power limited at this point though - probably good for peaks in the 95dB range max (at 1M) if there's no content below 20Hz. Below, you hit excursion issues really fast.

C