How do you improve mid-range?

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Hello
Out of frustration of unable to build a small portable speaker, I build a large one using 12mm MDF. Roughly 7 x 7.5 x 13.5 inch, which translates to 0.4 ft3 enclosure, internal.

Build the speaker using two Tymphany TC9FD18-08. No internal separation.

The low end is impressive but only in terms of the range. Can get down to roughly 40Hz.

Now one thing which I noticed is there still remain some lack of detail, not much but noticeable, in the mid-range. How can I improve that.

I had the same problem whilst building a small set, 10 x 4 x 3 inch unit(0.07ft3).

What general measures can I take to improve the clarity?
 
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If you are convinced that it's not the driver that is at fault here, try chamfering the rear of the driver cutout. In general terms for a 3" speaker 12mm material will need a chamfer. Small drivers tend not to breathe well through the rear, and a right-angled cutout will create some congestion in the midrange.

Also experiment with damping - sometimes reducing the stuffing in the area directly behind the driver may help. Do you have a filter to correct for BSC or is the driver running direct from the amp output? A filter would be able to properly solve the dip in the midrange and the rise in HF. Also achievable through EQ if you use the right software. The top will still remain fairly ragged, but the rise can be quite effectively damped (if it is deemed to be an issue in the first place).

That driver looks more like a widebander that needs tweeter support past 5k or so. At least, that's how I think it should be used.
 
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Some frequency response measurements would go a long way to debug this. The TC9FD is known for its exceptionally clear midrange and ability to render vocals astonishingly well. Sharing same chamber may be causing some cancelation of the mids of distance between drivers in back of chamber match range. I am guessing they are spaced ~9in apart center to center? That corresponds to a half wave frequency of 750Hz. You may be getting a depression near the mid range of 750Hz and this is what you perceive as lacking in the mids. Again, a measurement would show this if it indeed is happening.

Try adding a divider between interior chamber to isolate. Also the comment about chamfering the material on baffle to let drivers breathe is important.

Also, the precious comment about baffle step losses are important. With such a small box, the driver response will start falling off around 1kHz and you will have maybe 3dB less by time you get down to 750Hz. This combined with possible rear cancellation may cause problems.

Try adding about 0.5mH and 5ohm BSC between amp and driver to see if mids come back up. Might require 10ohms even.
 
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