Extremis 2-way design questions

[chAse]

I'm planning an extremis 2-way with an rs28a, and was looking for some input on the cabinet, and also the crossover. Right now I have some 38L cabinets that I built for some rs225's but have changed direction. Most of the MT designs for the extremis are the recommended 22L @33 but I saw that someone (Grahamt?) mentioned that they had them in a 34L box tuned a bit lower.
Any advantage in running them in the larger box, or should I just go with the standard 22L. I am running them in my bedroom, so no HT use, but I would like decent extension down below 30hz.

Also, what crossover point have you guys been using? I see people mention up to 3k, but some of the graphs I see of the extremis indicate that I would like to start getting off them somewhere short of 2k. Somewhere around 1600 seems like a decent spot to me, any opinions?

[Cal Weldon]

Hi chAse,

I have enjoyed the Extremis in a 3 way system more than a two way. Perhaps it's my ears but I just don't get the mid I'm looking for. When crossed over a little lower to those CSS 125 drivers, the mid magic is back.

Have you heard them in a two way?

Cal

[Grahamt]

Hi ChAse,

Yep that was me. The cabinets were 34L net and tuned with a 3" single flare to 29 Hz. They were flat to about 20 Hz if I recall correctly in my 3000 cubic foot room. There may be some FR plots here somewhere. I know of another person who is building a pair of about the same size.

The box is larger than recommended, but JonMarsh helped me design it and he certainly knows what he is doing. They were designed in Unibox.

The crossover point for a two way has been a somewhat controversial topic. On our project Jon recommended a low cross over point so we went with about 1.2 kHz. The reason for this was the excellent performance of the Seas 27TCFC, and testing results of the Extremis, as well as the center to center spacing. To each his own.

We definitely considered the RS28a but went with Seas. They seem to be very close in performance.

Here are the links for the project and testing.
http://htguide.com/forum/showthread.php4?t=12992

[chAse]

Havent heard them yet, but for this project I'd like to keep them 2-way for simplicity and keep the crossover components down to a reasonable number.

[chAse]

Yea I've been following the Extreme MT thread, but Jon's crossovers like to get a bit large for me Some of those caps are probably as big as my arm.
I hope to build one of his designs later, but for now I'd like to keep the component list down and run a LR 2nd order. These arent going to be for super critical listening, just looking for a decent response in room with a nice low end since I dont have room for a sub. I still may decide to do a bit more with the crossover after I get the box finished and drivers mounted, but for now the plan is to keep costs down.

As far as the box goes, maybe I'll squeeze the box down to 30L internal. I think 38L is going to be a bit too large. Tuning any higher than 30 hz is going to make the port length a bit to long for this box, so I think thats about where im going with the box.

[GM]

Originally posted by chAse
I think 38L is going to be a bit too large. Tuning any higher than 30 hz is going to make the port length a bit to long for this box, so I think thats about where im going with the box.

Greets!

Oh, really?! To get good damping with a large, short vent at 30 Hz, I calc'd a ~7.49 ft^3 (212.1 L) 1/4 WL tapered ML-TL using published specs. Sims real good too in MJK's ML-TQWT WS.

GM

[chAse]

I wish I know what you just said