"Gunning" a pair of SMGs - The journey

[squeegy200]

Several of you have inquired so I thought I'd post some pictures of the experimentation I did this past year with my humble pair of SMGs.

Peter Gunn's site intrigued me and reading the many positive reviews only made me more curious. After reading his many posts, lurking on his website for tips, tricks, & traps, and closely examining the many photos and samples, I slowly gathered the courage to attempt the modifications myself.

I purhased my SMGs off of eBay from a seller who recently had them refurbished at the Magnapan factory. So I considered the condition of my drivers to be in good shape. They came with factory fresh socks and the trim was unusual for vintage speakers of that era.
After lots of consideration, i finally removed the wood trim, the numerous staples, and removed the sock. Inside I discovered a crack in the MDF frame but otherwise, the drivers and wires looked fresh. The Peter Gunn commentaries warned me that I would find inexpensive crossover components buried inside the frame. I found some commentary discussing his experimentation with the values and components. I purchased Obbligato Film capacitors and Janzzen Air Foil and installed them according to some of the wiring diagrams I'd discovered in my readings.


I knew some of the Maggie models were wired out of phase. And my SMGs were no exception. I adjusted the wiring in one of the crossovers accordingly. The improvements in sound stage, dynamics, and delicacy were all dramatically improved. But the most notable improvement of all was the disappearance of the narrow focused sweet spot. I could now walk about the room and still hear some aspect of the music. I no longer had to sit in the perfect center to listen to the stereo image. I settled on a 22mF and a 30mF cap in each crossover. I'm no authority but according to my readings, this supposedly positioned the crossover point at somewhere around 1100-1300Hz. What I did find is that with the two capacitors, the mid-range moved forward in the sound stage giving the vocals a much bigger presence in the musical presentation.
After a couple of months, the speakers settled and I decided to plunge further into the madness. I closely examined the many pictures of Peter Gunn's amazing wood working craftsmanship. I was at first dismayed at the precision and expert execution of his craft. I was disheartened knowing I could not possibly mimic his beautiful Magnastand.
But after reading more about the benefits of the frame and stand itself, my curiosity motivated me to move onward.
According to Peter Gunn, the selection of wood did not matter. He chose several different types of wood specifically for their visual appeal. That said, I decided to use inexpensive "Select Pine" to mock up prototypes to achieve a proof of concept and to test my tools and skillsets. I eventually fabricated three sets of prototypes. Only the last had enough integrity to actually mount the drivers and test.

[squeegy200]

Only when I had fabricated straight clean corners and nice bevelled edges did I mount the drivers into one of my prototype frames.

Peter Gunn himself made mention of the challenges in the corners. He discussed the different methods for achieving the corners and mentioned that eventually the 45 degree corners would eventually fail. He much preferred the cabinet/door type corners for their strength. Of course I'm no woodworker so I'm sure my vocabulary isn't accurate terminology. But after attempting to create the frames myself, I now comprehend his comments.
I now could transfer the crossover components from the project boxes to the "cigar" boxes I made. For the cigar boxes, I selected Poplar wood for its integrity which Peter Gunn himself used on some of his own commissions. I like the color and texture of this type of wood.

These are the final prototypes. If I could describe the improvements, I would say that the sound simply got "bigger". Not louder --but bigger. These SMGs are simply much more grand than in their original form. I am fully aware that my own subjective perception in my listening room is my own characterization. However, I would confidently say, these now sound equal if not better than any of the Magnaplaner speakers I auditioned recently at my local dealer.

My woodshop is located in the mountains where winter recess stops all experimentation in my "wood shop" (aka garage) So this summer, equipped with what I've learned thus far, I'll attempt to use higher quality wood, finer finishes, and audiophile grade wires to fabricate a final pair of magnestands. The gentleman behind "Peter Gunn" is brilliant. And I'm so grateful he's shared so much of his experience and his notes so that DIYers like myself can also appreciate what he pioneered. Anyone who gives my amateurish handiwork an audition would likely conclude that Peter Gunn's magnastand modification elevates my humble maggies into true high-end territory

[squeegy200]

Here's the last set of prototype mockups. With each subsequent trial, I corrected mistakes, increased accuracy, and finished faster. I should be able to fabricate the final set using high quality furniture grade materials and audiophile components. That's about two weeks of uninterrupted work.

[blackraven]

Very nice work. I am sending my 1.6's and MMG's to you to Gunn them

[squeegy200]

Very nice work. I am sending my 1.6's and MMG's to you to Gunn them

He's written quite a bit about the 1.6 and 1.7s. I've restrained myself from buying a pair recently on eBay.

I'm seriously contemplating a set of MMGs and doing the same. Most of the SMG theory was derived from his work on the MMG. To be more accurate, he did not recommend doing this to an SMG but rather preferred MMGs. I simply did it because that's what I own and I saw it done to an SMGa.

[Feanor]

He's written quite a bit about the 1.6 and 1.7s. I've restrained myself from buying a pair recently on eBay.

I'm seriously contemplating a set of MMGs and doing the same. Most of the SMG theory was derived from his work on the MMG. To be more accurate, he did not recommend doing this to an SMG but rather preferred MMGs. I simply did it because that's what I own and I saw it done to an SMGa.

I owned MMGs several years and loved them. However it must said that these are inadequate speakers in medium or larger rooms, (though acceptable if crossed over to a subwoofer at 80 Hz). In general it will be preferable to put the money for "Gunning" them towards a new 1.7. Hey, just my opinion.

[squeegy200]

I believe the bulk of my expense was in time. I've probably accumulated over 200 hours over the past year experimenting with lots of trial and error.

The crossover components I bought from Hong Kong and the wood materials I picked up from Home Depot was somewhere around $200 in expenses.

I would like to audition these in a large space. My current listening space is only 14'x22' with a 12' ceiling at its peak--not very big.

I have to mention that once I did the crossover upgrade, I no longer felt a need for the subwoofer and reassigned that to the home theater system at the other house.

The Maggies for which I've compared against were in much smaller listening spaces. The Magnaplanar dealership near my home really doesn't have large listening spaces--they are similar if not smaller than my own dedicated listening space. And my ceiling is probably higher.

My total expense, if you include the cost of the original SMGs from eBay, is still under $500 total. Approaching the cost of a pair of stock MMGs and still about 1/5th the cost or a pair of 1.7s at retail.

[Feanor]

I believe the bulk of my expense was in time. I've probably accumulated over 200 hours over the past year experimenting with lots of trial and error.
...

My total expense, if you include the cost of the original SMGs from eBay, is still under $500 total. Approaching the cost of a pair of stock MMGs and still about 1/5th the cost or a pair of 1.7s at retail.

Considering you did the work yourself, (great job!), it sounds like good value. Having the work done by Gunn would be a different matter.

[blackraven]

I found that the MMG's put out much more bass when placed near the corner of a room. I placed bean bag cushions behind my MMG's at the corners of the room in my basement and I get nice smooth, tight deep bass from the MMG's. The Class D Audio amp helps quite a bit as well.

[rileyne]

Hi
new to this site and new to Maggies. Purchased the 1.7 a month ago after 10 years of Martin Logans. Spoke to Peter Gunn and he has given me the specs for the XO upgrade. Sounds like i will not get the db boost in the bass but thats ok, im looking for more coherent mids and highs. Parts on order. I will take piks of the XO when built and pics of the modified speaker when complete. Im very much an electronics new comer but with help from Pete and lots of sites like this I dont thinks it will be to daunting

[recoveryone]

I know nothing about MMG or SMG, but this is one of the best DIY mapped out from start to finish.

[Dawnrazor]

Here's the last set of prototype mockups. With each subsequent trial, I corrected mistakes, increased accuracy, and finished faster. I should be able to fabricate the final set using high quality furniture grade materials and audiophile components. That's about two weeks of uninterrupted work.

Great Job!!! That is amazing if you say you are not a wood worker! You will dig that i bet.

PG is right and when I saw his smgs the 45 degree joint did fail so take his word on that. I also thought the smg sounded better than the modded 1.6 he had on hand so great choice on your part!

Now there are some things you can do to improve even after this mod.

1. Try the choke tweaks. I know of 2 people with gunned mags that have tried that, and both have raved about the improvement. Put one on each driver. Al Sekela's RF-Choke Tweak

2. Same thing with the razor tweak. Everyone who has added that to their wooden frames has felt and heard an improvement. Some after hearing it decided not to do wood frames on their 2nd pair of mags. Razor your mags - Dawnrazor - Planar Speaker Asylum

3. If you have 8ft or shorter speakers try some 30g magwires for speaker cables.

4. Get rid of the driver tabs and put in some real binding posts. Those tabs are dreadful and I bet you can solder direct to the wires if you are careful and do some research on soldering aluminum. Or use some binding posts to hole the wires together.

5. One day go active with another amp and a good crossover or a PLLXO that mimics the smga series crossover curve or something flatter. ( where do you think that "db boost" is coming from but a tipped up crossover???)

If you can get them vertical and sit nearfield you will get a better soundstage and better sound as the room has less impact. If you sit far away then tilted is probably best.

If you have the room, dont be afraid to try them with the tweeters in. Dont just swap them and put the speakers in the same place, put the TWEETERS in the same place. If you have the room tweeter in the same place but in will give a larger soundstage than tweeters in the same place and out. Long story but it all comes down to the tweeter distances. If you start with them in you will prefer that because you will arrive at the proper tweeter distances. If you start with them out you will prefer that because you will end up with the proper tweeter distance apart. In both cases the distance will be similar, but the speakers will be in different places. If you have a small room, tweeters out produce the largest tweeter separation. If you have a larger room as it seems like you have, tweeters in produce the widest soundstage and there is something to be said for keeping the tweets away from the side walls.

Also think about building some grills. I know they might not help the sound, but see how great they can look when you arent using the speakers. Finally-MMG mods - powermatic - Planar Speaker Asylum

[squeegy200]

All good stuff. These types of tweeks always peaks my interest. Thank you for supplying the links to the relevant discussions.
So far there has been no deterioration in the woodwork. I've thought about redoing them with 90 degree "Door" style joints.

I have considered the "Razor" modifications just to see what it does. It is reversible so easily done without harm.

I'm not familiar with the RF Choke modification.

I have thought about trying active crossovers and adding another amplifier. I just may try that this summer.