Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Planar Speaker Asylum


Message Sort: Post Order or Asylum Reverse Threaded

Maggie slap / Mylar Stretched

74.11.152.187

Posted on July 30, 2016 at 05:36:50
pistonengine08
Audiophile

Posts: 24
Joined: February 25, 2013



Hi folks, this is the second time this has happened to me. First with the 1.6, I thought my fault, I had them setup weird, needed to drive one Maggie very hard to balanced volume at listening position. Sent them into factor for repair, lesson learned (or not!)

Sold those for 1.7i. Normal room, normal setup, Mylar is extremely distorted and slaps at low frequencies at modest volumes. When I listen to test tones, like for processor setup/eq, one Maggie produces a noticeably different tone from the other.

Amp is B&K Ref 7250. The Maggie's have gotten some time in direct sunlight when I open the curtain. Hot Florida sun. I typically have the preamp set to around -25 and the amp gains set accordingly to a comfortable volume - maybe somehow I was causing clipping or the amp is defective?


I'm considering sending the 1.7is in for repair, but I don't want this to happen again.

Has anyone experience this issue? Any advice?

 

Hide full thread outline!
    ...
RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 06:44:30
j beede
Audiophile

Posts: 239
Location: NorCal
Joined: March 28, 2011
FYI:

1) One of my Martin-Logan CLS exhibited nearly identical corner wrinkling in one diaphragm. It was due to localized failure of the adhesive that holds the stator/film "sandwich" together.

2) I have seen similar wrinkling in the treble dust covers in my QUAD 57s when I release the panel clamps to remove a bass panel.

My guess is that your clamping system or frames are mechanically distorting the failed panel's planarity.

In my experience direct sunlight is bad for just about everything...

 

Agree with j beede, posted on July 30, 2016 at 07:23:39
grantv
Manufacturer

Posts: 7717
Location: B.C.
Joined: January 15, 2002
Looks like you are forcing the edge of the panels inwards causing the issue. Find yourself a better way to hold the panel to the frame you made...

 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 09:32:32
Agree with the other two posters. The mounting scheme is non-optimal.

Dave.

 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 10:33:06
pistonengine08
Audiophile

Posts: 24
Joined: February 25, 2013
Well that is the last thing I wanted to hear. In the factory frames they sit pretty snugly in the MDF and have the staples holding them in face - not a ton of pressure. I'm definitely putting more pressure with the screws and washers than the factory setup.

If it's really the frames I'm not sure if there's a way to modify them easily - would likely have to be a full rebuild or stick with factory.

Just humorist me - is there a way I can tell if the amp is a problem? I'm just paranoid about having an issue when I repair/replace (with better mounting).

 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 10:33:39
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
You really need to redo the clamping setup t avoid distorting the driver's steel frame. Hopefuy the deformation is not permanent and remounting with an even distribution of stresses - like using a sandwich frame will straighten it out. If nt then send it back home to magnepan to undo the damage.

2nd, do not put it in direct sun. No transparent polymer can take it for long, and definitely not something like the thin mylar.

 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 11:40:26
Green Lantern
Audiophile

Posts: 16952
Location: San Diego, Ca
Joined: November 12, 2002
Contributor
  Since:
June 17, 2003
If you must have curtains drawn back to allow sunlight in, I'd suggest cloaking the panels with a heavy fabric. I'm surprised no one's come out with a pair Maggie 'sun socks' yet ;)









 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 13:44:31
The factory, stapled frames apply a much more consistent (and lighter) holding force around the circumference of the transducer. Some sort of a sandwich frame is the best approach, but even that has to be very carefully implemented or transducer damage can occur.

The sandwich frames I constructed for my MMG's a few years back are a superior approach. Those speakers are still working flawlessly.

Dave.

 

Some sort of long aluminum L-bracket with holes for screws for mounting. nt., posted on July 30, 2016 at 18:30:59
MWE
Audiophile

Posts: 2196
Location: Burlington, NC
Joined: June 8, 2000
nt.
Mark in NC
"The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon

 

RE: Maggie slap / Mylar Stretched, posted on July 30, 2016 at 20:28:16
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
I have a design for a full-length clamp which puts even but minimal pressure on the entire edge of the driver. Between driver and frame should go something like Teflon tape. I have this and it is Scotch #5181 which is 6.5 mil. NOT the stuff you wrap on pipe threads. The idea is to 'float' the panel in the frame.

One other note: Mylar is VERY low stretch and temp / chem stable.
Too much is never enough

 

RE: Maggie slap / Mylar Stretched., posted on July 30, 2016 at 23:25:20
berni
Audiophile

Posts: 184
Joined: May 30, 2011
The heat input on the mylar is quite large if it is painted black as here. Also the difference between a clear mylar and black can cause strange shrinking then we have a metal frame which also gets a heat input. I also think that the bolt with the washer tends to twist the frame outside, lay something under the washer so you get the wanted pressure with no twist to the frame.

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 00:17:47
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
Black mylar? You mean the EDGE which may be painted? How much heat input does the metal frame get? It's only exposed on a small part of it, the rest will RADIATE heat. I'd have to figure out the mylar physical data to see how HOT and how much STRETCH it gets.

I agree totally with the bolt / washer idea. It is BAD. I've got a design (thanks SketchUp) for a full-length low pressure clamp for driver to frame. In my design a SPRING applies pressure and between driver and frame is THICK Teflon adhesive tape, a Scotch product. Minimal amount of metal are used.
Small amount of pressure over a larger areas is good.

Too much is never enough

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 12:32:10
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
It can be a high pressure clamping just that it mus not distort the intended shape of the frame including not altering the curvature of the magnet board. The washers and screws definitely will not do it right.

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 12:55:06
No, it should definitely not be a high-pressure clamping scheme. There is no need for that, and if implemented as such you could incur similar problems to those already experienced by the OP.

The panel should be allowed to "float" in whatever frame it's installed. A spring-loaded scheme would probably be okay.....as long as the perimeter spring pressure was minimal.

Dave.

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 13:17:46
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
Many mod projects shown here used high pressure clamping without distorting the drivers' shapes, so why is high pressure something to be avoided? It would be beneficial for draining the frame of excess vibrational energy - PG's bolting technique does this in a rather brute force manner but is very successful in clearing up the midrange of the MMGs and 1.6's, as his fans attest.

 

RE: Maggie slap / Mylar Stretched, posted on July 31, 2016 at 15:07:46
Early model Maggies eventually became damaged by continued exposure to the sky-light UV which passed through windows, direct exposure to sunlight not being required. I owned Tympani 1C's which became damaged by this indirect exposure to light. I suppose Magnepan themselves were unaware of this, otherwise they would have advised accordingly. Of course later model Maggies did not contain using UV sensitive material. Nonetheless my T IV-As receive very minimal exposure to window light.

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 15:32:04
pictureguy
Audiophile

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



Screenshot, above is an idea I had to use bend wood for the spring. The clamp shown is also a non-starter and was substantially changed in the next revision.

We aren't talking a LOT of energy here. A firm clamping with no 'pressure' points is the way to go.
IMO, the secret is in the SPRING. No coils. No 'torsion' springs. I don't know what it's called, but a spring that is flat and 'wavey', maybe 1/2"wide and the length of each side. Use adjustable clamps and a torque wrench and adjust tension by ear. The correct name is 'Linear Wave Spring'.
Between the panel and the frame should be the 'float' in the form of easily source TEFLON tape. This is thick stuff made by Scotch.

Scroll down to the drawings.
Too much is never enough

 

RE: Maggie slap / Mylar Stretched, posted on July 31, 2016 at 20:22:15
Limniscate
Audiophile

Posts: 13
Location: TX
Joined: May 29, 2016
I believe that I had the same problem on my 1.7i's and ended up sending them in because they were still under warranty.

I think user "shoey" had the same problem and did a DIY solution.

Here's his thread:

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 21:15:28
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
Actually, the energy dissipation/pass through required may be a significant minority of the power input. A wave spring is not a bad idea for absorbing some of the energy, but it could have a narrow freq of max absorption rather than a broad range of freq the way a CLD damper would. but I am sure you can choose the compression pressure to provide a broader range.
The hard rigid contact for energy transfer to drain the driver frame (and magnet board) to the side struts would be my choice considering how well that is reported to work in PG's design..

 

RE: Maggie slap / Mylar Stretched., posted on July 31, 2016 at 23:55:39
pictureguy
Audiophile

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



I'm not going to have 'side struts'. I have a unique triangulated design using a SINGLE strut.
The trianulation provides incredible rigidity without additional metal AND at the same time a single path to a mechanical ground plane.
the key is ratio of length of the elements. And the mounting points on the frame.

The including drawing is my first generation 'noodle' for what I intend. This has also been changed since than. This drawing is for proportion / geometry ONLY. NOTE: The roller under the panel. The strut includes a VARIABLE tilt mechanism built-in and also acts in a manner similar to SPIKES do on box speakers.
Too much is never enough

 

RE: Maggie slap / Mylar Stretched., posted on August 1, 2016 at 06:58:44
Maybe you should define "high" pressure?

The transducer units have a "curvature" to them, and if any securing method aggressively removes that and/or creates a twist and/or creates a vice-like grip on any portion of the edges a user can run into problems.

I'm not sure many users are appreciating the forces involved here when fabricating different frames for their speakers.

Dave.

 

RE: Maggie slap / Mylar Stretched., posted on August 2, 2016 at 08:56:22
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
My favored approach is viscoelastic damping on one side and clamping with vertical Al or or wood "L" forms bolted to the wood frame in multiple locations along its length. That would be on the sides where there is no curvature. The bolts should screw to finger tight with the screwdriver and you can tune the spring loading from there by adjusting with extra torque..

 

Sunlight/Direct Sun? 100% the cause nt, posted on August 2, 2016 at 16:15:45
.

 

RE: Maggie slap / Mylar Stretched., posted on August 2, 2016 at 19:35:05
Did you look closely at the sandwich construction scheme I used on my MMG's a few years back? It's a much preferable setup to your favored approach.
It provides coupling to both sides, very even tension across the full perimeter, requires less fabrication of special pieces, has no finicky screw tension to worry about, requires no drilling of the transducers, etc, etc, etc.

Dave.

 

RE: Maggie slap / Mylar Stretched., posted on August 3, 2016 at 07:54:05
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
Actually I don't remember it specifically.I will look it up.

Thanks

 

Page processed in 0.031 seconds.