Crossover upgrades/mod(s) for newer MMG's

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mike_p

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Crossover upgrades/mod(s) for newer MMG's
« on: 6 Sep 2012, 05:17 pm »
Hi all,

Finally ordered that Hakko soldering station from Parts Connexion.  Please share your thoughts/plans for offloading, upgrading or otherwise modifying the crossover on the newer version MMG's. I assume that there are different schools of thought on this.

I have seen the mods on the MUG site, but don't know if they work for my speakers (early 2012 vintage).

Thanks in advance,

Mike

josh358

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #1 on: 6 Sep 2012, 09:12 pm »
Hi all,

Finally ordered that Hakko soldering station from Parts Connexion.  Please share your thoughts/plans for offloading, upgrading or otherwise modifying the crossover on the newer version MMG's. I assume that there are different schools of thought on this.

I have seen the mods on the MUG site, but don't know if they work for my speakers (early 2012 vintage).

Thanks in advance,

Mike

Some have reported good results applying the older crossovers to the newer units, I can't vouch for it personally. The two versions have different sized tweeters.

Upgrading the caps while keeping the existing configuration is I think a safer bet.

(A bit off topic: From my perspective, the must-do mod on the MMG is to make a stand that raises it up vertically and gets it up off the floor. This makes it image more like its bigger cousins. You will lose some bass response, though, so I'd only do it if you have a sub.)

SteveFord

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #2 on: 6 Sep 2012, 09:49 pm »
The coolest thing I've ever seen done with MMGs resides in Kevin360's uptown sin den.
Perhaps he'll chime in and post some pics as well?
I hung mine up in the air on hinges for what little it's worth.  It works for me.

mike_p

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #3 on: 6 Sep 2012, 10:02 pm »
Hi all,

Finally ordered that Hakko soldering station from Parts Connexion.  Please share your thoughts/plans for offloading, upgrading or otherwise modifying the crossover on the newer version MMG's. I assume that there are different schools of thought on this.

I have seen the mods on the MUG site, but don't know if they work for my speakers (early 2012 vintage).

Thanks in advance,

Mike

Some have reported good results applying the older crossovers to the newer units, I can't vouch for it personally. The two versions have different sized tweeters.

Upgrading the caps while keeping the existing configuration is I think a safer bet.

(A bit off topic: From my perspective, the must-do mod on the MMG is to make a stand that raises it up vertically and gets it up off the floor. This makes it image more like its bigger cousins. You will lose some bass response, though, so I'd only do it if you have a sub.)

Hi Josh,

Thanks. Any recommendations on specific replacement caps?

I did see Davey's hardwood/ply frame mod photos on another thread here ("Magnestand MMG Cheaper Alternative") and would like to try that one myself.

Best,

Mike

Davey

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #4 on: 7 Sep 2012, 12:23 am »
I don't think the alignment of the stock crossover (later version) is too bad at all.  If you want to rebuild it I'd recommend a 2.0mH 14awg air-core inductor and 16uF poly capacitor on the tweeter.  (2.2mH and 12uF is stock.)  That boosts the midrange just a touch without going completely overboard as with other designs I've seen.  :)
Obviously you can round file the fuseholder and related wiring to simplify the connection scheme.

I used six 2.7uF polypropylene surplus capacitors in parallel to form the 16uF and a Solen inductor.  A resistor in series with the tweeter is also preferred...in my situation.

http://www.madisoundspeakerstore.com/surplus-capacitors/2.7mfd-panasonic-capacitor/
http://www.madisoundspeakerstore.com/solen-14-awg-perfect-lay/solen-2.0-mh-perfect-lay-inductors-14-awg/

If your amplifier has significant output impedance you could add a conjugate network across the input terminals to level the impdance so the midrange is not bumped up even more.  See the bottom of this page:  http://home.comcast.net/~dreite/MMGPLL.htm

The frames are fairly easy to build if you have access to a table saw or chop saw.  I used off-the-shelf materials from my local Lowes.  I'm much more about performance than I am aesthetics, but if it floats your boat (and you have the money) you can go crazy with the woodworking as well.  The "sandwich" scheme I used is superior to all others with regard to the "vibration dissipation" condition.  And it also allows to not mutilate your transducer units with a whole bunch of holes.

I also recommend use of a dipole woofer scheme (with active analog crossover) to create a three-way system.  This allows bandwidth limiting the MMG's to above 80Hz.  That's not easy to accomplish since a custom crossover is required.  (DSP units can create the proper curves, but they have other problems that need attention.)

Josh's comment about raising the speakers is correct.  I believe the center of the transducers should be at ear height and they should be orientated vertically.

There's been much discussion of MMG modifications through the years......some of it just outright nonsense.  :)  But the fact remains that it's an excellent platform, both from a performance standpoint and from a value standpoint.

I've moved on to other projects, but would have no problem listening to the MMG's long term if I only had one set of speakers on a desert island.

Cheers,

Dave.
« Last Edit: 7 Sep 2012, 01:07 pm by Davey »

mike_p

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #5 on: 7 Sep 2012, 12:48 am »
Damn, Dave. Time for me to go back to school!

mike_p

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #6 on: 7 Sep 2012, 12:57 am »
Sorry. That last post came after reading the info above the schematic for the conjugate network.

josh358

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #7 on: 7 Sep 2012, 02:00 pm »
Hi Josh,

Thanks. Any recommendations on specific replacement caps?
Hi Mike,

I'd go with Davey's recommendations. He took his MMG mods much farther than I ever did, check out his dipole woofer.

Davey

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #8 on: 7 Sep 2012, 02:14 pm »
Here's the write up on the reframing project for those interested:

http://home.comcast.net/~dreite/MMGframe.htm

There's a photo of the dipole woofers and active crossover schematic near the bottom.  Unfortunately, the crossover is custom work and not easy to recreate with off-the-shelf commercial active crossovers.

Cheers,

Dave.

medium jim

Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #9 on: 7 Sep 2012, 07:23 pm »
Dave:

Your Pictures aren't loading in the link.   Nevermind, I reloaded and they appeared!   

Jim

kevin360

Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #10 on: 8 Sep 2012, 02:49 pm »
The coolest thing I've ever seen done with MMGs resides in Kevin360's uptown sin den.
Perhaps he'll chime in and post some pics as well?
I hung mine up in the air on hinges for what little it's worth.  It works for me.

Thanks Steve, but you must not 'get out much'. :lol: I've seen lots of really cool projects with MMGs. My own project was nothing more than an answer to a suite of conflicting constraints and desires. The 'stacking' solution is even more suited to their current use in a bedroom -  quite near-field. I'll resist the temptation to be self-deprecating about my woodworking skills (the photos say enough), but I will point out a few things about the design which I thought made sense.

Since these photos are hosted elsewhere, I'll be a little liberal with 'em. Here they are in their current application and I think they are truly phenomenal near-field speakers. For better and worse, being really close takes the room out of the equation (well, to a pretty significant degree). I can lean forward in my chair and touch them.



Here's a rear view that shows what's in the space beneath each MMG – an REL Q150. This photo is of the 11th iteration of my modded MMGs (12th if counting stock). For louder volumes, no setup bettered using a crossover to divide the chores between the subs and Maggies, but at the levels at which they play these days, running them full-range while allowing the subs to augment works beautifully. At one time, the connector plate (just the plate itself) was attached to the crossover box, hence the off center wire entry and the holes where screws used to be – I couldn't care less how ugly the back is as it faces the wall (as I mentioned, they've been through lots of changes). My idea for these hybrids was for the MMGs to straddle the subs rather than be physically attached to them in any way.



A peek beneath the hood reveals a 1st gen Magnepan crossover design (in a 2nd gen MMG). I tried a different 'popular and highly touted' design for while, but came back to these. For those concerned about the markedly reduced DCR of a foil inductor, the 'total circuit' shift is negligible – if there's an ill effect, I haven't heard it.  The components are mounted on plywood which rests on vibration damping material. The speaker cables have screw-on terminators (spades or bananas), but I thought it made more sense to just attach the crossover wiring (and the wire for the sub) directly to the screws, and the rather substantial ends are (well, were – using some Kimber wire presently) secured in the box (ergo, there's no strain on a connector or the wires inside).



Although I appreciate your 'coolest' comment, I think Dave's is the smartest – making true 3-ways with dipole woofers taking over the bottom end from hardwood 'sandwich' framed MMGs. :thumb: Were it not for space constraints (nowhere to put the subs), that's the approach I'd take. I also had a great experience using a PLLXO, thanks to Davey. Once again, present system constraints preclude my employing the best approach, but I assert with the greatest confidence that I am not suffering in the least. In fact, I think these MMG/REL hybrids sound phenomenal in their near-field setup.

medium jim

Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #11 on: 8 Sep 2012, 03:10 pm »
Kevin:

Pretty darn awesome!   

Jim

Davey

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #12 on: 9 Sep 2012, 01:51 pm »
Kevin,

I like the last photo.  You have those monster speaker wires making the transition to the (20awg?) internal wire with twisted together connections.  You must be some sort of internally conflicted audiophile.  :)

Or are those monster speaker wires actually the interconnects?  :)

Dave.

mike_p

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #13 on: 10 Sep 2012, 01:57 am »
Here's the write up on the reframing project for those interested:

http://home.comcast.net/~dreite/MMGframe.htm

There's a photo of the dipole woofers and active crossover schematic near the bottom.  Unfortunately, the crossover is custom work and not easy to recreate with off-the-shelf commercial active crossovers.

Cheers,

Dave.

Dave,

Please explain the purpose of the pocket holes in the hardwood cross-pieces at the bottom of the frame.

Thanks,

Mike

Davey

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #14 on: 10 Sep 2012, 03:14 am »
They're on the top cross-piece as well.  (You just can't see them easily in the photo's.)

The pocket holes are for the pocket screws that hold the frame together.  It's a joinery technique that's really easy, but you need a drilling jig and special bit to implement.

http://www.kregtool.com/Pocket-Hole-Jigs-Prodlist.html

I could have used a number of other techniques as well.  Biscuit joint....a couple of different dado joints....a miter joint....a half-lapped joint...etc...etc.  Even a simple, glued butt joint would be fine.
Each half is not unlike a picture frame.  The critical piece is the 1/4" plywood spacer in between the two halves.  The thickness of this creates the proper squeeze (contact to the xducers) but still allows seasonal movement of the wood to not damage the xducers.

Cheers,

Dave.

kevin360

Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #15 on: 10 Sep 2012, 03:18 pm »
Kevin,

I like the last photo.  You have those monster speaker wires making the transition to the (20awg?) internal wire with twisted together connections.  You must be some sort of internally conflicted audiophile.  :)

Or are those monster speaker wires actually the interconnects?  :)

Dave.

Hey Dave,

Aren't all audiophiles internally conflicted? The engineer in me laughs at my audiophile foolishness while the audiophile in me scoffs at my scientific understanding. For decades, the audiophile in me has been suppressed. That was largely out of necessity, as life was moving rapidly and there were always more important things. Nowadays, I have lots of free time and preciously few expenses. That silly audiophile got out of his box and has been doing a pretty good job of making up for lost time, but I have drawn lines in the sand here and there (there are some things about which I'll never be conflicted).

The wire is DH Labs IIRC, and it's 14 & 18 AWG. It was secured to the end of the PS Audio Statement wire pictured below. As I posted this photo, I realized that you might be interested in what's in the background. It's an REL plate amp. The two input paths merge into one after the high level input is subjected to a voltage divider. I ordered a pair of caps for it – should be here tomorrow. One of the electrolytics is shorted (a victim of vibration? (caps don't short that often and it seems likely that serious mechanical stress could lead to dielectric breakdown)). I have to torque the screws that secure the plate amp and driver once a year. Otherwise, they vibrate their way loose. Anyway, I'm going to replace both just in case the violent environment contributed to the cap's failure (and they're only $5/ea).



The wires are twisted, then soldered. A couple of the wires on each panel got rather short when I abandoned the crossover pictured below in favor of the one it replaced (which is Magnepan's design). Being somewhat lazy, I spliced in some new wire rather than replacing it at the tabs (which is something of a PITA).



I thought you might find interest in the photo below as well. Early tinkering included Maggie Mates – 4 caps per device (a pair of electrolytics to provide the necessary capacitance with a pair of film bypass caps). So, it's just a first order filter, but it was pretty effective. It was a fairly short-lived experiment, but I was curious. Raising them also benefits sub integration (that project was in an early stage of development when the photos were taken). I'd like to have a crossover between my MMGs and subs , but I'm quite fond of the integrated amp in that system and it's in a tight space. Besides, I don't exactly crank the volume with that system.


mike_p

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #16 on: 10 Sep 2012, 04:57 pm »
They're on the top cross-piece as well.  (You just can't see them easily in the photo's.)

The pocket holes are for the pocket screws that hold the frame together.  It's a joinery technique that's really easy, but you need a drilling jig and special bit to implement.

http://www.kregtool.com/Pocket-Hole-Jigs-Prodlist.html

I could have used a number of other techniques as well.  Biscuit joint....a couple of different dado joints....a miter joint....a half-lapped joint...etc...etc.  Even a simple, glued butt joint would be fine.
Each half is not unlike a picture frame.  The critical piece is the 1/4" plywood spacer in between the two halves.  The thickness of this creates the proper squeeze (contact to the xducers) but still allows seasonal movement of the wood to not damage the xducers.

Cheers,

Dave.

Neat. Nice web site. The standard Kreg Jig could also help me turn our old 30" x 50" x 3" maple kitchen island top into a pretty decent hi-fi stand. I've been meditating on taking it to a furniture shop for a few careful cuts, and then putting solid hardwood legs on. Although I've been remodeling the house, I'm no cabinet maker. It looks like with this thing I won't have to be.

Best,

Mike

medium jim

Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #17 on: 10 Sep 2012, 06:34 pm »
Kevin:

Thanks for the photo of the Maggie-Mates without their cases. I agree with you that they are effective.  Some day I might opt for digital bass mgmt., but I'm of the school, less is more. Besides, I detect no defects in the way my system sounds, so why mess it up.

Jim

Davey

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #18 on: 11 Sep 2012, 02:33 am »
Kevin,

The REL amp uses a simple voltage-divider to reduce the high-level input to low-level?  How 'bout that.  :)

I thought it was some sort of magical high-quality proprietary circuitry that performed that function for REL.  :)

Cheers,

Dave.

jk@home

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Re: Crossover upgrades/mod(s) for newer MMG's
« Reply #19 on: 16 Sep 2012, 09:07 pm »
I have heavily modded my MMGs, used Davey's sandwich frame design but layed out more on the lines of the Magnestand product. Built the sandwich frames, but have them tilted so that middle of the driver aims towards my ears. With attached back struts, all resting on a base, with an external x-over box in the rear.

The speakers set up straight vertical worked better in my old larger room, but in the MMGs present location in a smaller dedicated room, I prefer the tilt. So IMHO, you should try it both ways.

Also, with a reframing job, you have the option of whether you want the pole pieces (opposite of the mylar side) facing the front or back (I prefer the latter). And you should check into the "Razor" mod (search the planar asylum), I found that to be an improvement.