Seas MTM enclosure question

[mathman]

Hi all; long time lurker, first time poster.

I have all of the parts to build an MTM setup, and the crossovers are wired, so now I just need something to put them in, so I thought I'd take suggestions. I have the W18E-001 woofer and T25CF-02 (Millennium) tweet.

So, my question is: how big, and what tuning frequency? The crossover is from the Thor/Odin, so the baffle width is fixed at 9". The height will be around 50-52" to keep the tweeter at an appropriate height. As for depth, maybe 12-13". If you factor in a 1.5" baffle, a port, and some bracing, it looks like my max volume is about 2.2 ft^3. If I'm using WinISD correctly, at 2.2 ft^3 with a 33Hz tuning frequency, it yields about a 1dB bass shelf with a 33Hz f3. A 3dB bass shelf would require about 3 ft^3, a bit too big.

Any thoughts? The EBS seems preferable to a QB3, as I would really like the extension, but I'm open to suggestions!

[graks]

Have built the Seas Odin, havent the finish yet... The elements are in offset.

[mathman]

Hey groks. I looked at the Odin enclosure, which I believe is about 1 ft^3 tuned to 40Hz, give or take. If you get them wired, I would be interested in hearing your thoughts on how they sound.

My guess (from looking at WinISD's predictions) is that a larger box tuned slightly lower would deliver a lot more extension at the expense of a slight loss (about 1dB here) in the 60-100Hz region. The real rolloff in the larger EBS box begins at about 40Hz, which I hope will work well in-room to deliver some serious impact.

[mathman]

Sorry graks, I seem to have misspelled your name!

Last night, I reduced the dimensions slightly to about 1.85ft^3 - to keep the size a little bit more manageable. It looks like tuning will still be around 34Hz, with a very, very slight bass shelf.

I'm somewhat concerned about the in-room response - that this may get a little boomy. Could someone comment on that? The freq response is flat to about 100Hz, at which a 0.5dB bass shelf begins. The real rolloff begins around 40Hz, and the f3 is around 34Hz. Would that get too bass-heavy in a 12' X 15' X 9' room?

[graks]

How did your project go? i have used the Odins for many months now, with a sub for each channel as stands.

[mathman]

Hello again.

I got everything built and tested, and was completely blown away. This was my first experience with the Seas Excel drivers, and I have virtually no complaints. They sound really neutral to me, and I don’t find the woofers to be unforgiving – a common complaint. The tweeters sound perhaps just a bit soft, but that’s fine by me – I listen to a lot of rock music that’s pretty hot. I’d like to hear the Scan 9500 tweets again for comparison, as I remember them very fondly. The bass was surprising… the modeled F3 was (I think) 32Hz, and the bass is really well-controlled. These guys are going to be hard to top…

[graks]

Hi.
What dimension have you cabinets? Nice to hear you are satisfied with the result!

[mathman]

Externally, about 49" x 9" x 12.5", or 124.5cm x 23cm x 32cm. Construction is 0.75" (19mm) MDF with a 1.5" (38mm) front baffle and bracing. Net internal volume works out to 1.95ft^3 (55l).

Just checked, and tuning (using WinISD) is 34Hz with a predicted F3 of 34Hz. There is a 0.7dB bass shelf.

[imjatse]

Just in case you didn't see it, there is a huge thread on the thor design here

I built the short thor variation and am quit pleased. The boxes are big, so if space is a concern, I would recommend a different design.