# MTM build sort of...



## domwilson (Oct 31, 2010)

I'm building an MCM 55-3870 MTM sort of. The woofers are spaced a differently from the tweeter which is a Vifa D27TG-35-06. One is at 6.5" center to center and the other is 5.5" center to center from the tweeter. I've modeled it in Response Modeler for BSC. Then in speaker workshop and gspeakers. I've also did the enclosure in WinISD pro. I've checked and double checked the parameters with and without the FRD files from Response modeler. But I don't know if or feel comfortable with the results that this is correct. The response looks a little too perfect. What are your thoughts? I've attached the responses and the crossover. This is a tower with 1.33 cu. ft. volume with a 2.5" rear mounted port tuned to 46 hz. The hump at 200 hz is the gated response from Response Modeler when I did the Baffle step Response.
Attached Thumbnails


----------



## GranteedEV (Aug 8, 2010)

What about off axis response? Any idea what that's going to look like?


----------



## Zeitgeist (Apr 4, 2009)

Interesting. What are the cabinet dimensions?


----------



## domwilson (Oct 31, 2010)

Zeitgeist said:


> Interesting. What are the cabinet dimensions?


It's 38" tall X 7.5 " wide X 12" deep.

I don't have off axis data. Don't know how to simulate that with speaker workshop. Do you have a recommendation for simulation?


----------



## fusseli (May 1, 2007)

No such thing as too perfect  So this is a 2.5-way in an MTM layout? Have you tried modelling as TMM then?

Can you provide a plot zooming in on the passband a bit more (like display 85-95dB only) that shows a grid of 1dB increments? I'm guessing it will look less perfect. The jump at 200Hz is probably just from your splice in the response modeller?


----------



## domwilson (Oct 31, 2010)

Unfortunately, the shop I had the wood cut messed up the baffles. So I just went with it as is. Here is a response graph in 1 db increments.


----------



## fusseli (May 1, 2007)

Gotcha. Ya I've also had to live with my mains varying from the exact simulated baffle. It does effect FR but isn't too much of a difference. Looks like you're +/-2dB, still not bad!

So why are you doing a 2.5-way in an MTM and why not go TMM?


----------



## domwilson (Oct 31, 2010)

I had the MDF cut by a shop that does custom automobile installations. Only they screwed up.
The baffles were cut with the MTM configuration. Except the tweeter was not evenly spaced between the midwoofers. The offset was correct but just not the spacing. So when I did the BSC I had to compensate for the alignment. Thank goodness they mirrored the baffles correctly. Just not the spacing of the driver holes. These are going into my bedroom system. 
See pic...


----------



## domwilson (Oct 31, 2010)

Here are some pics of the finished speakers...


----------



## StereoClarity (Apr 22, 2008)

Lovely, but we need better pictures to be able to tell just how nice they really are!


----------



## Zeitgeist (Apr 4, 2009)

That's a nice bedroom system.

I noticed the HSU sub in the corner..  I'm planning on doing that with my old HSU at some point..


----------



## domwilson (Oct 31, 2010)

Sorry. That's not the bedroom. The sub isn't a HSU sub either. It's a old Realistic sub cab and amp. Been braced and dampened. Then I thru a different sub in the cab. Not as boomy as before. Fills in the bottom end for the maggies. These speakers replaced some prodigy towers in the bedroom. I do most of my music listening in the bedroom.


----------



## Owen Bartley (Oct 18, 2006)

Really nice finish Dom! I agree though, we need to see some better pics of that gloss! It looks like a dark stain that still shows some grain in it? Nice job.


----------

