Planar Speaker Asylum

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Planar Speaker Asylum

Maggies are not invincible

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In Reply to: RE: IF You own 20.1's and you biamp posted by russ69 on March 09, 2015 at 22:32:16

Again, my goal is safety.
My concern is delamination. Shipping 20.1's is >$800 on a pallet.
Ive read of too many 3.6's with delam probs that were pushed too hard and overheated.(i know, some were old Miloxane)
My first experience with the MMGs which were trial trial speakers which were pushed too far and I know I damaged them...I then went on to get 1.6s.

My goal is to send the frequencies which are beyond the safe handling of the 20.1s away into the ether.
What do you suggest as that cut off frequency and slope?

Follow Ups:

"Again, my goal is safety ... My concern is delamination" ... - andyr 19:12:50 03/11/15 (1)
That's certainly a conundrum - however, your thinking is a bit misconceived.

As someone said - delam basically comes from the glue failing (not so much of a problem these days, I believe, with the glue Magnepan is now using). Playing LFs very loudly will not cause the wire/foil to lose contact with the mylar ... however, it can possibly cause another problem (which I saw on some IIIas a decade ago). This is ... loud LFs causes a lot of current to pass down the bass wires - the louder the music, the higher the current. The higher current causes the mylar to excurt more (hence, a louder sound).

The more current flowing down the wires ... the more they heat up ... and the wires try to expand lengthways. The wires that are clamped under the 'tuning discs' cannot move (at the disc end, anyway) so the only way they can expand is sideways - ie. you can get an 'S-bend' produced, adjacent to the tuning discs, for those few wires that are clamped by the tuning discs.

This may well cause the wire's adhesive to lose its grip on the mylar (although in the instance I saw, this hadn't happened).

So if you absolutely do not ever want to have to send your 20.1s back to Magnepan AND you play music which has a significant LF content loudly then, yes, I suggest you should apply a HP filter to the bass panel.

But I suggest you will ruin your musical experience if you do this without adding a pair of subs to your system, to present the LFs you are excluding from the Maggie bass panels!

You see, a 48dB slope @ say 30Hz is not a 'brick wall' filter - it has a slope, so some notes below 30Hz still get through to the bass panels. Also, the response of the bass panels doesn't start rolling off at 30Hz ... there will actually be a hearable reduction in bass probably as high as 40Hz. (The 30Hz is the -6dB point on the roll-off curve - ie. where the signal level has reduced to 50%.)

If I was as paranoid about damaging my Maggies as you seem to be, I would:
* add a pair of subs,
* use a 2-way active XO (which may come with the subs)
* set the LP filter for 24dB at 40 or 50Hz (higher slopes produce their own problems)
* and set the HP filter (the Maggie feed) for 24dB at 40 or 50Hz.

This arrangement will mean you:
1. have protected your 20.1s
2. don't lose the underpinning bass which is essential for musical enjoyment, and
3. get an extra benefit ... because the amp driving the 20.1s no longer has to 'use up' power on the extreme LFs, it has more grunt to drive the rest of the frequencies which the bass panels are handling! This is really equivalent to getting a new amp at, say, twice the power! :-))

I will be doing something similar, at the end of 2015. Not because I'm afraid of damaging my 'Frankenpans' but because, after over 20 years of Maggie ownership, I am finally adding a pair of 15" sealed subs to my system ... so I can get more enjoyment from my Bach organ music and Yello albums! :-)) I will probably set the roll-off point at 60-80Hz so the room gets pressurised by the cone sub drivers; the digital XO will also give me bass frequency room EQ facilities.

Good luck,

Andy
- RE: "Again, my goal is safety ... My concern is delamination" ... - Satie 22:02:13 03/14/15 (0)
  See post above.
  
  I would not worry about driving the 20.x bass panels into oblivion unless you have in excess of 3kw/ch available and a 50 amp circuit.
  
  I have toasted my very powerful amp (see above) and am now considering a subwoofer again for sub 30hz. Not because the Tympanis can't handle it but because the amp can't. At least not for prolonged ear popping bass.
  
  I really don't want to get a more powerful amp.Outside of these experiments my usual bass listening levels are not that extreme - though far heavier than anyone else has reported here.
  
  The one good reason to XO to a sub is to avoid the IMD from high energy low freq. signals going into your mids and tweeter. Basically that is why I prefer the Tympani models to the 20.x as the bass panels are separate.
RE: Maggies are not invincible - russ69 21:53:28 03/10/15 (0)
Delams are from age not playing loud. I think that problem is history now with a change in design and materials. Some of the experts can give the details.

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