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

[Wolf]

If you are using the Minimus7 cabs, then the layout as above with the 1.1mH coil is correct. The aluminum reduces the value of the I-core coil, so it had to be increased. The 0.1mH air-cores do not seem to be affected. This is as Matt and I laid his out (guess I never posted this!?):


If you find a white pair that is in really good shape, keep Matt in mind. He's been looking for a pair of white cabs.

Later,
Wolf

[Dirk]

So is this the "final form" as far as crossover? There's a guy in town selling 5 or 6 pairs of Minimuses for less than I'd be able to get them on eBay.

...Minimusen? Minimae?

[Wolf]

For those using Minimus 7 cabinets....

Update for the Min7 owners....

My buddy MusicforMatt just received his drivers for the revamp of his Min7 cabs. As it turns out, the surround of the ND25 no-face is just a bit too large in diameter to fit within the hole on the tweeter's faceplate. He used a box-cutter knife to remove a bit of plastic on the face to allow them to fit properly. He used super glue to adhere them to the Min7 faces.

Electrically, the filter is the same, except the 0.9mH LP coil needs to be a slightly larger 1.1mH if the Min7 aluminum cabinet is used. It reduces the inductiveness of the coil just being in the aluminum housing. I dropped the original 1.2mH coil into the cab attached to the LC meter, and it dropped to 1.0mH, therefore 1.1mH I/bar-core will be 0.9mH. The 0.1mH 18AWG air-cores seem to be mainly unaffected.

Here is a layout using the Jantzen Standard Z-caps (they are a very small poly, and what Matt bought):


This 1/8" hardboard substrate will fit with drivers mounted inside the cabinet, and mount to preexisting holes. You may have to dremel off the first nub above the terminal hole to get it to lay flat. You can use adhesive on the other 2 nubs to add mounting if you wish.

More as Matt completes his....
Later,
Wolf

[Wolf]

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

Ben,

I was thinking about putting the amp and crossovers in the sub enclosure. I didn't contact Meniscus today and I suspect the freight may cost me more then the inductors. I do have a couple of other items I wanted to order from PE for another project, so was wondering if I could substitute a .9mH/18awg for the iron core without effecting the performance of the crossover too much. There is not much difference in the cost. I see the DCR goes up, but I don't know how that would impact the crossover??

You will lose bass output by the order of a couple decibels. You could use a P-core.... They're HUGE though. Either way, an 18awg air will shift the tonal balance due to the higher DCR.

Later,
Wolf

[Kevin K.]

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

Ben,

I was thinking about putting the amp and crossovers in the sub enclosure. I didn't contact Meniscus today and I suspect the freight may cost me more then the inductors. I do have a couple of other items I wanted to order from PE for another project, so was wondering if I could substitute a .9mH/18awg for the iron core without effecting the performance of the crossover too much. There is not much difference in the cost. I see the DCR goes up, but I don't know how that would impact the crossover??

[Kevin K.]

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

I believe it says "On a desktop, 2-3" above, freestanding, or on-wall." Those are 4 options. For best results, I think free-standing or 2-3" above are the best.
A false bottom would be fine, but the extended baffle height may change some things very minimally. Being the impedance is only 4 ohms in 2 places, I think the amp will be fine.

I'm curious- did you get the steel laminate 1.0mH/18AWG to unwind a bit, or which other coil? I just want to know what you end up with.

And also of note- I think you should try them first without the woofer sealed to the baffle. It seems the leakiness allows it to reach a little lower if it's not sealed, but it won't take as much power. I also used these jacks:

http://www.parts-express.com/gold-plated-banana-jack-pair--091-1160

They are through holes, and allow a little leakage.

Keep me posted!
Wolf

As luck would have it, PE was out of the 1.0 Iron Cores. I didn't get a chance to contact Meniscus but they show an option to order the 1.0 modified to .9, so that is the route it looks like I will take. I ordered the ND25 without the faceplate. Was planning on rear mounting both drivers. Still trying to decide on a small sub to tie to the 2.1 amp. Wanted something fairly efficient due the size of the amp. Was thinking either one SD215A-88 or two of the Peerless 5.25" buyouts wired parallel. Trying to keep the total project cost under $200.00 which would include the parts for the amp, your Synchaeta's and the sub. I've got about $35.00 left for the sub. Thanks for responding and I'll keep you posted as the project begins to move along.

[Wolf]

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

Question, you put a note on your crossover schematic "2-3 inches above". Would it be ok to build the enclosure 3" taller with a false bottom and place the crossovers down there upside down? I guess I could use some standoffs to suspend them right side up if it wont work. Thanks for posting the design, looking forward to building them.

I believe it says "On a desktop, 2-3" above, freestanding, or on-wall." Those are 4 options. For best results, I think free-standing or 2-3" above are the best.
A false bottom would be fine, but the extended baffle height may change some things very minimally. Being the impedance is only 4 ohms in 2 places, I think the amp will be fine.

I'm curious- did you get the steel laminate 1.0mH/18AWG to unwind a bit, or which other coil? I just want to know what you end up with.

And also of note- I think you should try them first without the woofer sealed to the baffle. It seems the leakiness allows it to reach a little lower if it's not sealed, but it won't take as much power. I also used these jacks:

http://www.parts-express.com/gold-plated-banana-jack-pair--091-1160

They are through holes, and allow a little leakage.

Keep me posted!
Wolf

[Kevin K.]

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

I will confirm that the little 2.1 amp has no problems with a 4 ohm load... My little oak bluetooth speaker was running for about 8 hours straight at the speaker competition on Saturday at fairly high levels (those little Aura's are quite inefficient) without an issue. 4 ohm load on the left and right channel, 8 ohm on the subwoofer.

Thanks for the confirmation Chris. After I get all of this stuff built, I will provide feedback on how it worked with my set up. I may be running 4ohm on the sub also, so it will be interesting to see how that goes.

[Chris_Perez]

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

I will confirm that the little 2.1 amp has no problems with a 4 ohm load... My little oak bluetooth speaker was running for about 8 hours straight at the speaker competition on Saturday at fairly high levels (those little Aura's are quite inefficient) without an issue. 4 ohm load on the left and right channel, 8 ohm on the subwoofer.

[Kevin K.]

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

Ben,

Told you I liked em! I pulled the trigger on the order today, should have the parts in time for the weekend. I am going to use Tom's new 2.1 plate amp that is in the new flyer and build it into these as desktops. Tom mentioned he had run the amp with 4ohm speakers and didn't notice any problems. I figured as efficient as these little guys are and being near field on a desk, it should probably work fine.

Question, you put a note on your crossover schematic "2-3 inches above". Would it be ok to build the enclosure 3" taller with a false bottom and place the crossovers down there upside down? I guess I could use some standoffs to suspend them right side up if it wont work. Thanks for posting the design, looking forward to building them.

[Kevin K.]

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

I got to hear these little guys last night with a group of guys in Ben's room and then heard them again at the competition in a very large room. They sounded fantastic for their size. I was floored at how well they filled up the room in the competition. If you need to go small but don't want to give up much sound quality, these are going to be hard to beat. I'm ordering parts for a pair to put on my desk next week! I may add a small sub under the desk to compliment them only because my desk is out in the middle of the office.

[6thplanet]

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

Cool, thanks for the explications.

[Wolf]

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

Apparently, I forgot to add the relative driver centers to the thread, and I never mentioned the actual built dimensions.
The depth on mine are different to compensate for using 1/2" back and 3/4" baffle. All edges are rounded with a 1/4" roundover.
I used 3/16" wood paneling for the sides top and bottom.
HWD on mine is 7" x 4 5/8" x 6", and the real actual Min7 dims are listed easily on google:



Driver positions:



There- all info is included in the build thread!
Later,
Wolf

[Wolf]

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

So essentially what your getting at is if the break up is a bunch of crap at the end of the FR of a driver you'd shoot for a CR shunt. If its more of a large peaky looking break up then using a L w/ CR notch would be the better choice.

I have sufficiently rolled off a resonance in a driver with a 3rd order filter and no notch. As long as the peak is reduced to a decent level, notches aren't required. Typically when I use a CR, it's more to tweak the knee of the xover to rolloff the woofer as I want it to. Some drivers like the Seas L18 require an LC (no R) to suppress the breakup, as well as a 3rd order:


In the case of the Stance, the RS125-4 has a gnarsty breakup that is +5dB above reference, from 8-15k. I had to take it to -50dB for it to not affect the FR or be heard.

If it's a broader peak, and of low amplitude like in baffle step bump, and in-bandwidth, then a parallel notch placed in series with the driver is your best bet. This also will not affect the impedance detrimentally like a shunt/series notch will. If it's out of bandwidth, then an LC(R) is usually easier, and won't affect the impedance due to the LP's inductive rise.

Another thing to try is a broad LC that is out of bandwidth on a woofer. This can work like a tank cap does across the main LP coil in terms of breakup suppression, and works sometimes when the tank won't.

I guess- it really depends on the application,
Wolf

[6thplanet]

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

So essentially what your getting at is if the break up is a bunch of crap at the end of the FR of a driver you'd shoot for a CR shunt. If its more of a large peaky looking break up then using a L w/ CR notch would be the better choice.