Peter Gunn’s - “The Emperor’s New Clothes” - MG1.6/QR redo

OK, I dragged them downstairs after giving up all hope of taking pictures in my listening room, and I got a few shots before they got crated and sent packing to their new home today.  Click thumb for large image.

The wood chosen for these was African Makore.  I’d heard it had what guitar builders call good “tap tone” (whatever the hell that is), and as I had the chance to get ahold of enough of it to do the work I tried it.  It works quite easily with hand or power tools and has no bad habits, except for the fact that the dust causes violent choking fits which requires full respirator use while working it.  In real life it is a much darker color than these photos show, looking much like 200 year old cherry, although the wood changes hue dramatically depending how the light hits it.  I got a little creative with the crossover boxes, making an oriental design and using Makore, Oak and highly streaked Poplar for the tops.  This will probably be a permanent trend as making the crossover boxes on every pair different appeals to me (and allows the only creativity in the whole project).  The only original part used from the stock MG1.6’s as I received them are the drivers.  (oh, and 4 of the bottom bracket bolts)

People tend to obsess over the wood chosen, as if one in particular has some magical properties, but so far I have not noticed one sounding so much better than any others.  Thus, it’s contesion any good hardwood would probably yield rather good results for you.  To me, fancier woods only look better.  Ash might be better if you can get it, but oak is probably your most easily obtainable choice and a safe bet.

As far as the mod goes, it was my hope to redesign them along the parameters of the SMGa because I believe that design most fully captures what Maggies do best.  On top of that the stock MG1.6 is full of what I perceive to be flaws that needed addressing.  Among the things needing correcting were turning the pole piece (magnets) from the back to the front, removing the MDF frame which was shabbily made, allowing for some rear tilt and redoing the crossover to a 1st-order (6dBl/oct) shared type like the SMGa uses.  After some trial (and much error) I finally got it dialed in, and they have the magical, live and very musical presentation the SMGa’s are noted for.  The differences being a larger presentation (naturally) and slightly more extended highs due to the quasi ribbon tweeter. 

If it would be your guess that they have more bass or dynamics than the SMGa, I believe they do not.  The larger panel makes for more decibels, but that’s not more resolution.  They simply sound bigger and more grand, the SMGa’s more intimate and personal.  (That doesn’t mean quiet however, as the SMGa’s can blast)  Both reproduce the audio spectrum with the same glee, and are cut from the same sonic cloth now.  It’s really a matter of personal taste, IMHO.

All future MG1.6’s I do will be done ‘this’ way.  They must be full frames because I can’t work with the MDF frame as it comes for these, and it’s just horrible anyway.  If it’s your desire to copy it, I suggest you do likewise.

Now, for those interested in copying it, like Ben Franklin I’m giving full disclosure.  The bases are simple and don’t need any explanation.  The metal feet however from the original can’t be used.  You will need to go get iron bar (½″ wide by ¾″ thick [but 3/16″ may do]) and cut, drill and bend it yourself to the desired shapes.  This will require a well made steel bending brake.  The angle I use is about 2°, give or take .  What matters most is making them all identical.

Frames are the toughest part for a DIY’er.  First, the corner miters are not 45°, and can’t be.  I also can’t give you dedicated sizes.  The why is because we must be a slave to what the lumber yard gives us.  It’s all great to figure out a “plan” on paper where everything fits nicely on an 8″ wide board, only when you go to collect your 8″ wide board you find there are none, or a nicer looking board is a different size etc...  So you really have to make your plans there and take what nature (and the sawyer) gives you.  So while the side rails here are about 4″ , if you can only find boards that allow 3¾″ width rails, that’s fine, do that.  However, whatever you do will determine what the corner angles will be.  My parts were sized about 4″ for the sides, 2¾″ for the tops and 6″ for the bottoms (which lowered the drivers compared to the MDF frame.  They were up way too high in the stock speaker)

Since the insides must be routed for the driver frame, the corners use biscuit joints towards the inner front facing part and dowels along the middle of the outer part.  Yes, it’s double the work and a PITA but you’ll be glad once you rout AND glue up.  If you don’t use dowels the frame will wrack badly once the clamps start going tight, and even then it takes prudence.  The corners are essentially wedges and want to slide along each other, not compress.

I had to install fabric on these as the pole piece was really crappy looking on them (just that way from the factory) and that is a step you won’t love either.  You’ll first have to make shims out of ⅛″ masonite to support the frames between the metal cross bracing pieces on the driver.  I installed the fabric alone, but it would be far easier for 2 people to stretch the fabric across the opening while you, using a gauge to mark the location of the cross braces insert the shims and adhere them with a staple gun.  The driver is attached with screws thru holes drilled in the metal side frames (be very careful doing this as the fine and sharp filings go right to the mylar and stick because of the magnets.  Keep a good shop vac nearby and suck all the filings after every hole is drilled, but don’t suck the driver.  Use a fine brush to wisk them into the vac) On a final note, allow for some extra room when routing the frame for wood expansion.  In other words, don’t make the driver fit “snug”.  (and don’t forget to install them with the mylar to the back)

The frames attach to the bases and the strut to the frame with threaded inserts.  The strut to the base with a hanger bolt.  Sizes you’ll have to determine when you do it.

All that leaves is the crossover.  I have noted in the past I keep my boxes closed because I don’t want the owners obsessing over what’s in there.  Nobody tears open their new Sonus Fabers to make sure the caps are up to snuff, and nobody should worry about this.  (They sound as good as Maggies can, and if you don’t like that my advice is to sell them, not change anything).  In light of that, I won’t get into specifics here.  However, if you want to do it my way, email me and I will be happy to tell you what parts and of what values to buy, and how to wire it all (and how to rewire the speakers as they need it too).  I will say I used a 1.5Ω Duelund resistor on them to make the tweeters behave and they are very nice and worth the money.  I tried Mills first and they were OK, but compared to the Duelunds they were a picture with the top of the photo cut off.  The Duelunds make it sound like the sonic image is imperceptibly cropped.  They’re close to $20 a pop, but well worth it!

I think that’s it.  If you have any construction queries feel free to ask, and if you attempt it by all means let me know how it turns out.

Thanks!

It’s all about the music...