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3.6R mods

96.245.215.96
Posted on May 1, 2023 at 12:38:49
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004

I had some buzzes in my 3.6Rs and decided it was finally time to tackle the repairs. Pressing on the perforated pole piece in certain places stopped the buzzes, so I was pretty sure it was loose panels. So, I tore into them and bolted the panels to the MDF frames with 28 10-32 screws per speaker. I ran the idea past Mick at Magnepan before doing so, and he said it should work great. I also added two pieces of 1/4" x 1" 6061 aluminum to the back of each speaker which is held by the 28 panel screws. These pieces run slightly longer than the whole length of the driver panels and really stiffened up the entire speaker. It's actually pretty amazing how much stiffer the speakers are now that everything is bolted together. While the speakers are laying on a table, there is absolutely no sagging or bending when lifting one end up from the table as there was before the aluminum pieces were added. When the speakers are mounted in their stands, they are rock solid.

My speakers always had a bit of a bow to them. While I had them apart, I managed to get them pin straight again. This was a pretty easy process which took about an hour or two per speaker. All you need is a 6' straight edge and some patience. The steel strips that are glued to the MDF are responsible for holding the speakers straight. All you need to do is carefully tweak the speaker, measure, tweak, measure, tweak, etc. The steel strips will hold the shape. Now that the aluminum pieces are part of the speaker, they won't be developing and bends in the future.

I built a jig to hold the speakers perfectly level and in one plane for the drilling and bolting operations. I 3D printed drill guides that attached to a vacuum to capture all of the MDF, steel, and aluminum swarf, I machined new mounting brackets for the stands' diagonal supports, I had to precisely straighten the aluminum extrusions because they weren't perfectly straight as purchased. Just straightening the aluminum extrusions took about 8 hours! The whole project was a ton of work that took me about three months to complete, but it was so worth it. There is absolutely no buzzing on any tracks or frequency sweeps anymore, they are perfectly straight, and the bass that I'm getting out of them is incredible! I can actually feel the bass is my chest and the bass now excites the floor of the room. They never did that before. I'm certain that preventing movement of the driver panel within the MDF frame is responsible for some of the additional bass, but I strongly believe that stiffening the whole speaker has something to do with it, too. Thanks for reading.

 

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RE: 3.6R mods, posted on May 1, 2023 at 12:39:54
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004

Inside

 

RE: 3.6R mods, posted on May 1, 2023 at 12:40:37
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004

Extrusion detail

 

RE: Great job - yeah ..., posted on May 1, 2023 at 15:36:30
andyr
Manufacturer

Posts: 12550
Location: Melbourne
Joined: September 2, 2000
 Stiffening up the mdf frames is a 'must have'.

 

good Lord ....., posted on May 1, 2023 at 15:40:56
trioderob
Audiophile

Posts: 753
Joined: May 15, 2015
 why did you have to show me those aluminum pieces ?

those are called " item extrusions "

I must have worked on 200 designs using those in my lifetime for robotic systems !

the 3rd photo down from the top of this link will show you the kind of design I worked on

 

RE: 3.6R mods, posted on May 1, 2023 at 17:28:46
Barry
Audiophile

Posts: 1003
Location: PA
Joined: November 24, 1999
Contributor
  Since: January 18, 2009
 Wow. I'm impressed with the work you did. Great job!

I think this problem is more common than most people realize. Some may have bought better stands, and thought they fixed it because of the improvements they heard, but there's still some residual mechanical vibration.

 

RE: 3.6R mods, posted on May 1, 2023 at 19:24:14
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 Thanks, Barry! I have never seen anyone do anything exactly like this, so I wanted to share it with you guys. Is it better than a hardwood frame? Maybe, maybe not. It's definitely significantly better than stock.

 

Nice work!, posted on May 2, 2023 at 07:07:05
E-Stat
Audiophile

Posts: 37645
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 That's the primary reason I opted for the tubular steel framed Sound Lab stats.

 

RE: Nice work!, posted on May 3, 2023 at 07:09:28
Roger Gustavsson
Audiophile

Posts: 2058
Location: Huskvarna
Joined: February 12, 2010
 The extrusions certainly stiffen up the baffles but I think the perforated sheet metal need stiffening as well. If the that moves, it is distorsion. The small crossbars Magnepan puts there is not doing much of a job.

 

RE: Nice work!, posted on May 3, 2023 at 08:46:19
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 I have a couple of ideas on how to stiffen them up. Now that the socks are off, I can feel them while they play and get a sense of how much they move. They certainly vibrate, but it doesn't seem like that much even on loud, bass heavy music. I wonder how much this movement affects the sound. I'll probably rebuild the internal crossovers before doing any additional stiffening. For now, I'm really enjoying the higher resolution, more accurate sound. The bass is just so much more well defined. In some ways they sound like totally different speakers.

 

++1 nt, posted on May 3, 2023 at 16:36:46
Green Lantern
Audiophile

Posts: 16952
Location: San Diego, Ca
Joined: November 12, 2002
Contributor
  Since: June 17, 2003









 

RE: Nice work!, posted on May 5, 2023 at 19:46:44
emailtim
Audiophile

Posts: 5476
Joined: July 2, 2017
 Nice job.

As for the vibrations, have you seen the Razor mod ?
.

2022/03/30 Historical Records CENSORED

 

RE: Nice work!, posted on May 7, 2023 at 11:55:45
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 I have, but it's a little too crude for me and pretty much irreversible. I have used that kind of sound deadener in vehicles and there would be absolutely no way of getting it off of the pole piece if I ever wanted to. I can't see myself doing it, to be honest.

 

+1, posted on May 7, 2023 at 12:29:41
Barry
Audiophile

Posts: 1003
Location: PA
Joined: November 24, 1999
Contributor
  Since: January 18, 2009
 Several years ago I bought a couple of boxes of sound deadener to do the Razor damping mod, but I just didn't like the mess they'd make. I still have the stuff.

If you think of a more elegant solution that the average person could do, please share it.

The XO cap mods are a major improvement for the tweeter-mid internal crossover, but bi-amping the bass panels are a better first step. Sadly, there's no cheap way to do either.

 

RE: +1, posted on May 7, 2023 at 13:08:06
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 I'm currently horizontally biamping. Internal crossover mods and rewiring with good wire and connectors is probably going to be the next project. You're right. None of this is cheap!

 

Whatever you do, posted on May 7, 2023 at 15:34:05
Barry
Audiophile

Posts: 1003
Location: PA
Joined: November 24, 1999
Contributor
  Since: January 18, 2009
 with the internal crossover, you've got to get a nice box to put the parts in! I was inspired by Peter Gunn's work many years ago and got someone who made humidors to make a pair of these.






I wish I was as good with metalwork as you are.

 

RE: Nice work!, posted on May 7, 2023 at 17:18:33
emailtim
Audiophile

Posts: 5476
Joined: July 2, 2017
 I tend to agree with you, but dampening appears to help if it can be achieved by suitable alternative means (another oldie, chopstick/string dampening).

I had one car done with Dynamat Extreme. Doors, floor, trunk pan, firewalls. It really quieted down the road noise and made the doors sound like they were no longer stamped out of a beer can.

I have also used it on the back of high velocity vent grates to get rid of the vibrations.

I used the cheaper metal foil backed peel and stick Snow & Ice Shield for roofing on appliances to quiet them. Did the back of my new refrigerator and lined the inside of the front door skin and outside of the drum of my dish washer.

Made both quieter and also adds some insulation so the fridge stays cooler, runs less and the dishwasher's hot water heater works better. We can no longer hear the dishwasher running.

I had to replace the DW pump, so while I had it torn apart, I decided to try to quiet it down and it made a difference. The newer appliances are a joke compared to the old ones.


.

2022/03/30 Historical Records CENSORED

 

RE: 3.6R mods, posted on May 9, 2023 at 05:34:44
watts
Audiophile

Posts: 536
Location: B.C.
Joined: June 30, 2004
 Cool! My next (and final?) speaker project. I have yet to do anything with the rigidity of the speakers, I haven't even mass-loaded the space in the Mye-stands.

If it wasn't too much more money, as aluminum is not "cheap" these days, I wonder about the investigation of carbon fibre extrusions? If rigidity is the primary objective I believe carbon fibre has more resistance to bending.
But perhaps we wouldn't mind the extra mass of the aluminum anyway...


Trioderob do you have any input?

 

RE: +1, posted on May 9, 2023 at 06:46:45
Roger Gustavsson
Audiophile

Posts: 2058
Location: Huskvarna
Joined: February 12, 2010
 I still think this is the way to go, tinyurl.com/2p93dtpw

 

RE: 3.6R mods, posted on May 9, 2023 at 09:44:29
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 Carbon fiber may work, but I wanted something thick to provide a very even clamping force. It seems like most carbon fiber is pretty thin, but I didn't even consider using it due to my familiarity with working with aluminum and knowing that it would do exactly what I wanted it to do and machine exactly how I would expect it to. No experimenting or guessing was involved as there might have been with CF. And if the aluminum pieces weren't perfectly straight, as they weren't, they can be straightened. Not so with CF.

The aluminum extrusions are only about 2.5 lbs per piece. CF would be lighter, but we're only talking a difference of a couple pounds per speaker between CF and Al.

I've listened to my stiffened Maggies every day, and I continue to be amazed at the improvement and wonder how much further they can be pushed. Since completing these mods, I have been dreaming up a whole new frame design. It will be a frame and stand integrated into one piece for extremely high strength and likely constructed of heavy gauge square or rectangular steel tubing loaded with sand or foam damping material. The frame/stand portion will be built around the driver panel only and the tweeter will be in a satellite frame, connected to the main frame, but decoupled from most of the vibrations of the panel. The tweeter frame would need to be pretty substantial, too, to make sure the tweeter is clamped straight since they have a natural bow to them. This would probably be the ultimate solution. I'm not a huge fan of wood as it tends to move around a lot and will push and pull on the drivers, potentially changing mylar tension in an unpredictable manner. I'll probably never get around to doing this, though. Maybe if I got ahold of another pair of Maggies as I don't want my system to be down for too long.

 

Do a search on AndyR's Frankenpans, posted on May 9, 2023 at 11:24:28
MaggiesAndCats
Audiophile

Posts: 697
Joined: August 31, 2009
Contributor
  Since: July 16, 2010
 It seems you're going down a similar path.

Regards,

Steve

 

RE: 3.6R mods, posted on May 22, 2023 at 14:52:44
RickeyM
Audiophile

Posts: 2208
Location: East Coast
Joined: March 15, 2003
 Years ago when I Quazi-Gunned my MMG's (same mods a PG's but with different components) I did a variation of the hardwood frame termed a sandwich frame. Two frames of wood with the driver sandwiched in between. The wood frames have much less flex than the factory MDF and my frames were effectively twice as thick. My frames also incorporated diagonal braces and thick wood bases. All this to say I know what you mean when you take the flex out of these speakers. The bass, for lack of a better term "hit" much harder. They didn't play any deeper but what they did play they played with more authority.

 

RE: 3.6R mods, posted on May 22, 2023 at 14:54:40
RickeyM
Audiophile

Posts: 2208
Location: East Coast
Joined: March 15, 2003
 Now you've got me wondering if it would be a plus on a pair ow hardwood framed speakers?

 

RE: 3.6R mods, posted on June 8, 2023 at 10:19:25
ketchup
Audiophile

Posts: 622
Location: Pennsylvania
Joined: February 29, 2004
 If I ever build hardwood frames for these, the aluminum angles are definitely going to be used. I think they will stiffen hardwood frames and maybe even prevent them from warping as wood tends to move around a bit.

 

RE: 3.6R mods, posted on June 11, 2023 at 17:02:58
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008



Incomplete article on Al V Carbon.

Aluminum has No fatigue strength. Each stress cycle eats into ultimate lifetime.

And there are plenty of alloys available.
For some? It is OK to glue. For others? You heat treat for maximum strength.
They sell a lot of 6061 T6 aluminum bike frames. Which are basically the strength of mild steel.....

If you told me I'd HAVE to use Auminum for a reframe? I'd use a 7000 series. This series has the highest strength Al alloys, but not the highest fatigue properties....which may probably be found in a 2000 series. I'll take the strength over fatigue in THIS APPLICATION...

Some other materials to be considered for a reframe?
You may want to consider CORIAN.....Available in suitable thickensses, it is used for countertops..

You may also consider PLYBOO....Which is Bamboo Plywood. This is available in 3/4" thickness and in some varieties fairly dense. Differnt fiber lays make choosing fun.

Certainly, rigidity is desired in a reframe. But also the conduction of such vibrations also plays into the final result. And you don't need a rigid material if designed for rigidity. Look at a bridge where some effort is made to keep it light. The Tacoma Narrows bridge collapse of about 1940 is a case in point. Easily capable of withstanding the static load, it also was light AND had aerodynaic properties. When a BIG wind off the ocean hit......it induced an oscillation which dumped the whole thing in the ocean. And I think the insurance hadn't been paid. Good luck with THAT.


Attached is a 'noodle' of mine. Considering how to make a backsupport for a panel that was both Light and Rigid......The twisting is resisted by the triangulation....

Too much is never enough

 

RE: 3.6R mods, posted on June 13, 2023 at 12:03:42
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 Ingenious design will Trump brute force and mass......
Too much is never enough

 

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