I theorize: 'Synchaeta'....a Minimus 7 revamp...

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Kinda what I thought, do you feel thats any better than the cap/res in parallel with the woofers coil? Personally I can't hear a difference, whats your take on the matter?

There is a difference in what a CR and LC(R) filter does. A CR will cause a change in the impedance and level of the knee before rolloff, so it does attenuate the broader range a bit. The LC focuses a resonance to shunt a narrower freq range, dictated by the Q of the filter's resonance, to 0 ohms or whatever resistance used as the R. The inductive rise of the lowpass affects the impedance to raise it back to a healthier range.

When you have a breakup peak, there are 2 ways to get rid of it- Attenuation, or shorting it out. This usually involves a notch rather than a CR filter, or it will not be completely compensated. A CR would not have done what was required to minimize the breakup to negligible levels.

Later,
Wolf

[6thplanet]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Kinda what I thought, do you feel thats any better than the cap/res in parallel with the woofers coil? Personally I can't hear a difference, whats your take on the matter?

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

It tanks the breakup.
Thanks!
Wolf

[6thplanet]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Nice little build there Benny! Whats the 0.1mH coil in series with the 3.3 cap doing for the woofer?

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Final pics and official xover schematic:







Thanks for looking!
Wolf

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

I buttoned them up about 1:30am Saturday. The woofer seal will be done now that I'm satisfied with the results. I used 1+ oz of fill in the cabs. 0.25 oz Ultratouch denim in the back, and 0.75 oz premium poly-fil in front of that (measured on my scale). I also had a very small amount of the single layer Sonic Barrier left over, so I cut it in half and used about a 2" square on the inner top panels.

Had them over at Matt's waaayyy early this morning before coming home to sleep, and they really do a nice job at most anything. Sweep from the IMM-6 on his phone into the DTA120 shows relatively flat response, if not just a touch polite on the very top end- when sitting on his computer desk. The close boundaries really do emphasize the lowest bass, and it does a relatively good job in that area. It even does better than the Rat Shack 40-1030- so the revamp is an upgrade for sure!
The bonus is the vocals never sound thick even when on the desk, so the dippy 500-900 Hz range did improve that aspect of the design for easier placement. Raising it on stands and evening the tweeter to ear level was also better. Tonality didn't change much standing at a distance either.

Oh- they get pretty loud pretty quick too!

I'd say the xover is good as it is, and I won't be changing it. I know most steel core coils don't go below 1.0mH due to core saturation and such, but unwinding one to 0.9mH isn't going to harm much at these levels.

I'll post the official schematic in the near future,
Wolf

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

That's a pretty tidy little crossover board.

Thank you! Winding the coil around that cap was not the easiest thing I've ever done either....
Saved a LOT of space though,
Wolf

[Navy Guy]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

That's a pretty tidy little crossover board.

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Here's the pic of the patch:
Sorry for the fuzz- I was also trying to get the picture of the rubber floor tile glued to the side walls. This adds mass and lowers the Fb of the panels since they are 3/16" thick.



Xover in position:
I did not solder the resistor to the tweeter, as the leads on my used 15 ohm were not long enough. The space between the terminals is long enough to fit the resistor though. 3" hole saw for the boards. I had to go 'off-board' to get it all on there.




Mounting hole yet to be drilled marked by the blue dot, will allow installation through the tweeter hole with a simple screw:



All poly'd up:



Wall mount included to keep true to the original:



I have yet to build the other and solder both xovers, install the terminals and stuffing, and then apply seals for the drivers and torque them into place.

I should have them playing this weekend,
Wolf

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Seemed to do what I wanted.

2nd cab is glued up, one xover assembled, and hope to finish within the next week.
Later,
Wolf

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

If you want a great, super strong putty that dries into something like glass: 8 parts Durham's, 3 parts Titebond, 2-3 parts water. Great adhesion, super-strong.

Thanks! I'll give that a whirl....
Wolf

[JasonP]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

I'm going to try some Durham's Rock Hard Water Putty in the blemish, and reshape if possible.
Glad you're enjoying it.
Later,
Wolf

If you want a great, super strong putty that dries into something like glass: 8 parts Durham's, 3 parts Titebond, 2-3 parts water. Great adhesion, super-strong.

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Hey Ben, I'm enjoying your thread. Looking forward to seeing how it all turns out.

I'm going to try some Durham's Rock Hard Water Putty in the blemish, and reshape if possible.
Glad you're enjoying it.
Later,
Wolf

[Jeff B.]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Hey Ben, I'm enjoying your thread. Looking forward to seeing how it all turns out.

[Wolf]

Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

Time for some photos...

They drop into the Min7 cabs:


Drivers:



Size compare and early assembly:



She fits after I cut away the remainder! I used a flush trim bit with the collar bearing from a pattern bit, and the flush radius is slightly less than that of the pattern bearing. This leaves the lip for the 4" to set against and seal easily. I also had to dremel the tweeter a smidge to allow the midbass to sit properly in that ridge. Outer hole is a true 4".



Oh- you see that spot on the left of the hole in the 2nd pic above? Yeah- I'll explain that....
You see- smaller cabs don't have the potential energy of larger cabs, and therefore move easier. I had the shop vac hose in the tweeter hole to extract the dust when I was using this BIG UGLY BIT to relieve the inside of the hole. This is a 1/4" shank, with a 1/2" roundunder from MLCS, and it's NLA from the on-line website anyway.

But I digress....
When I was finished and shutoff the router, and proceeded to lift it, the cab shifted due to the weight of the hose, and that still spinning bit made a nice large gouge in the recess of the woofer. I won't do that on the second one!


Luckily, the woofer all but covers the issue created. I should be able to add a bit of foamie or sealant and keep the integrity of the cabinet. All is not lost. The 1/4" holes you see are for dowels to be glued in and increase the integrity of all of the joints against the baffle/back. They will be flush trimmed once the glue has set.


And the final 2-way fitment...


Next step is to do the same to the other cab, and then cut for xover/terminal plate for the rear.
Later,
Wolf