The Minimus 7 solution

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Well, I put the drivers in the M7 cabinets with some poly batting and took a quick listen. The verdict? Well, they're OK. No bass, that's for sure. They are very efficient. They also go surprisingly high in frequency for a 4-incher. I think they have potential, but need to have some of the upper mid 'fierceness' damped down. They sound more 'intense' than I like (not relaxed enough).

I'm thinking the frame may need some damping. Tapping on it creates a ringing that can't be good. I should probably dampen the M7 cabinet too. I'm sure it rings some.

I used to use Roma Plastilina modeling clay on cabinet walls and speaker driver frames. Maybe there's something better, maybe easier to use. Any suggestions?

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frugal-phile™
Joined 2001
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Both A6m & FR88 will need new baffles. The A6 brings some cosmetic issues (bezel wider than box)

Measured the box at 1.7 litre.

dave
 

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If working with one of the vented M7 version and using a subwoofer for the low-end, I'd just suggest to completely plug the vent to create a sealed box, or try to fill it with enough resistive material to go aperiodic (see that the BR double-hump disapears and yields a single peak on the system Z_curve).

As for being serious about converting an M7 enclosure for fullrange use, one could precisely cut a wood/bamboo baffle that will fit into the front recess of the grille-less enclosure. It would also be nice to adress possible ringing of the thin metal walls; ductseal or something similar might help, but will reduce Vb; possibly another reason to go aperiodic if that make the Q too high. I think a subwoofer will most often be needed, unless a fantastic driver is discovered! ;)

IG
 
Has anyone experimented with damping the driver's metal frame? Or is any ringing from that of so little consequence that it can be ignored until ready for the very final tweaking?

I put an L-pad on the W4-930SF/M7, Rseries of 3 ohms, Rparallel of 7 ohms, in the neighborhood of -5dB attenuation. Wired them in parallel with my Tannoys, and using them as "reflective" speakers (firing up, reflecting off the back wall, sort of a sound diffusion effect). It sounds OK, more dynamic than the Tannoys alone.

I'll experiment with dampening them to make them sound more polite. They're a bit too raucous for me at this point. But the W4-930SF is a drop-in fit for the Minimus 7 cab.
 
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Has anyone experimented with damping the driver's metal frame? Or is any ringing from that of so little consequence that it can be ignored until ready for the very final tweaking?

I put an L-pad on the W4-930SF/M7, Rseries of 3 ohms, Rparallel of 7 ohms, in the neighborhood of -5dB attenuation. Wired them in parallel with my Tannoys, and using them as "reflective" speakers (firing up, reflecting off the back wall, sort of a sound diffusion effect). It sounds OK, more dynamic than the Tannoys alone.

I'll experiment with dampening them to make them sound more polite. They're a bit too raucous for me at this point. But the W4-930SF is a drop-in fit for the Minimus 7 cab.

You might want to look into a zobel network for the TB to tame the rising response, that could be making it sound harsh.

Alternatively, try eNABLE to control the cone breakup modes, that also contributes to harshness at multiples of cone breakup frequencies.
 
OK, eNABL (Planet 10) looks like it would be worth a try. I'll need to read up on that...

Also, there's a big spike in the response centered at about 7kHz. I think a compensation circuit needs to be put in for that. Of course, that will decrease the efficiency of this full-range, decreasing its usefulness. No wonder the driver is that inexpensive. No free lunch.

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OK, eNABL (Planet 10) looks like it would be worth a try. I'll need to read up on that...

Also, there's a big spike in the response centered at about 7kHz. I think a compensation circuit needs to be put in for that. Of course, that will decrease the efficiency of this full-range, decreasing its usefulness. No wonder the driver is that inexpensive. No free lunch.

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I'm tempted to buy the same TB woofers for my Minimus 7. Do you have a graph of the response showing the 7k Hz peak? It looks very smooth on the graph published in Madisound / PE.

If you don't mind sharing details of the Zobel network that you are using?

Qualitatively, does the TB woofer full range sound better / worse than the original Minimus 7 woofer + tweeter with the original ragged response?

Thanks!
 
I'm tempted to buy the same TB woofers for my Minimus 7. Do you have a graph of the response showing the 7k Hz peak? It looks very smooth on the graph published in Madisound / PE.

If you don't mind sharing details of the Zobel network that you are using?

Qualitatively, does the TB woofer full range sound better / worse than the original Minimus 7 woofer + tweeter with the original ragged response?

Thanks!

The response graph in PE site is zoomed out and overly generalized. It makes the driver response look smoother than it really is. Look carefully at the +/- dB scale (vertical scale).

I used an online calculator to get the values for the Zobel network. Speaker Zobel / Impedance Equalization Network Circuit Calculator

I found the sound of the TB driver to be peaky and ragged in the upper mids to lower trebles. Not much going on above 12kHz, at least as far as my old ears can tell. I'm not getting much of an "airy" response from them.

Also, I'm getting no bass at all. My idea was to use them in a sort of "FAST" arrangement, sitting on top of a pair of old KLH 6 cabs with the tweeters removed, used as the bass speakers. This would be bi-amped with a little 8wpc EL34-triode tube amp for the TB's and a Hafler solid state amp for the bass. But the TB drivers need some taming before I get that far.

If you're looking for a woofer to replace the original in the Minimus 7, then I'd say this model TB ain't it. No bass at all in this cab.

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