MCM 8" 55-2421 Isobaric

[tb46]

Hi ODougbo,

Post #199: "...If you are interested in another concept take a look @ xrk971's nice ideas here...PP Slot Loaded Sub with Alpine SWR 12D2...I added a number of sketches, e.g.: Posts #177/187/192/195/223. xrk971 added a bunch of AkAbak simulations, e.g.: Post #185. lawbiding build this there are build pictures throughout the thread, e.g.: Post #254. That should give you an idea, either way it's an interesting thread with all kinds of enclosure ideas."

Here is the link from Post #199 again, don't know why it didn't work the first time:

http://www.diyaudio.com/forums/subwoofers/264737-pp-slot-loaded-sub-alpine-swr-12d2.html


Regards,

 

[ODougbo]

Okay thanks snappyturtle, I didn't go crazy with the fill/lining on the second box.
So some feedback...the the lining/fill sounded a little better and didn't lose db.

Also tried several positions and speaker stands. This old metal stand (8"high) works nicely in a down firing setting, but it's fine woofers forward, up off the floor on the same 8" stand.

*shown is the second box, with the removable back.

not likely. the peak is a function of the design. stuffing it, or even heavily lining it, will only serve to lower upper band response/peaks. could also muffle some nasties that may be making their way out of the port (ie motor noise, etc) heavy lining or stuffing could also reduce system sensitivity across the band.

 

[snappyturtle]

Okay thanks snappyturtle, I didn't go crazy with the fill/lining on the second box.
So some feedback...the the lining/fill sounded a little better and didn't lose db.

Also tried several positions and speaker stands. This old metal stand (8"high) works nicely in a down firing setting, but it's fine woofers forward, up off the floor on the same 8" stand.

*shown is the second box, with the removable back.

looking good. appears you calmed that peak down 5ish decibels, which likely makes a significant in room difference. though it looks like you picked up a big 60hz null, did measurement location change? does changing the orientation of the driver remedy that at all?

 

[ODougbo]

Hi and thanks,
Tried all the easy fixes, spinning the box in every direction, the best was up on the 8" stand, forward.
The 60hz null: Moved the mic around the room, the reading were close to the same, best results are back by the big-guy's chair (0; Other than that, the first peak just tilted in both directions, not by much. I've been checking several other subs in the room also, there's always a dip, sometimes lower than 60hz. Which may not bad in my case, the other BR speakers in the HT sail past 60hz.

adding pic, the red line on left is a completely different sub

I can hardly believing the compact box can cranks out sounds like canon/gun fire, explosions, etc., at high the levels, with no problems at all. For a long time we used two of them, only need one now, with the addition of a high pass filter.

 

[gkh]

Hi ODougbo,

You probably are aware of this, but for a symmetrical layout as in Post #198 you don't need a center divider board in the port.

Cork board works, but it will reduce the internal volume (about by the volume taken up by the cork). Some felt would be better, even thin carpet underlayment felt will work.

So, this means to just have a common port of 3/4" - or common 1-1/2"? Both plus thickness of whatever lining used, of course.

Sorry for the noob question!

Rgds
Gerald

 

[ODougbo]

Gerald,

Are you using the MCM woofer for a project?
The easiest thing to do is put it in a small sealed box with a bit of eq.
e.g. YUNG 200 watt with 6db boost, quite impressive really.

 

[gkh]

Gerald,

Are you using the MCM woofer for a project?
The easiest thing to do is put it in a small sealed box with a bit of eq.
e.g. YUNG 200 watt with 6db boost, quite impressive really.

This very project wouldn't allow for EQ or plate amp, I have to use the available signal from the amp and just cross over the main speakers.

But thanks for the advice!

Rgds
Gerald

P.S.: Besides, being in Europe, I have to find a supplier for the MCM...

 

[ODougbo]

The paper cone is pretty thin for a speaker with a huge magnet. It will start to waffle if it is played to loud (and good reason to go ISO)
The MCM will certainly go low, but at a cost.
Attachment, MCM woffer modeled in a few different boxes.

 

[tb46]

Hi gkh,

Post #205: "...Post #198...a common port of 3/4" - or common 1-1/2"?..."

1-1/2"

Regards,

 

[gkh]

Hi gkh,

Post #205: "...Post #198...a common port of 3/4" - or common 1-1/2"?..."

1-1/2"

Regards,

Thanks

 

[gkh]

New drawing...

 

[ODougbo]

gkh,

I think you'll receive more replies if you start a new thread on your project, with more details on your ultimate goal and equipment you plan to use.

Cheers, Doug

 

[gkh]

Sorry, didn't want to hijack yyour thread.