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

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Planar Speaker Asylum ]

---

[ Alert Moderator ]

---

Lies, more lies and damn statistics! :-)) ..

Posted by andyr (M) on October 23, 2010 at 18:51:44

In Reply to: RE: Old Fashion Walnut 2.5R posted by Peter Gunn on October 23, 2010 at 08:46:42:

Dear Mr. Gunn,

I am forced, this sunny Sunday morning to deconstruct your post and put you right on a few things. Your text is in italics.

I do have to comment on this separation of tweeter and state issue that redwood started. (leave it to an australian to cause problems) I do not agree with it, nor does it make sense to me.

His contention was the vibrations from the main driver are effecting the tweeter. Yet he also finally made himself mentally agree MDF was bad and he needed wooden frames. So in his mind he concluded mdf is preventing vibrations from getting off the main driver, and yet magically at the same time it is conducting vibrations thru itself to contaminate the ribbon?

You can't have your wallaby and eat it too....

Yes you can - wallaby is very tasty ... much more so than crocodile, IMO. :-))

The vibrations produced by the bass driver in a stock (ie. MDF framed) IIIa/3.X Series shake the ribbon cage. The T-IV and T-IVa are the only models that Magnepan made, which have the ribbon (and mid) on a separate panel ... to stop this problem.

Re. MDF frames vs. hardwood frames.

As you say, MDF is not a "helpful" framing material - hardwood is better. But with my IIIas - which had hardwood frames but the normal construction method of having all drivers in the one frame - I could feel the ribbon-side stile vibrating (ie. as far away from the bass driver as possible) when bass-heavy music was playing.

With my Frankenpans, this does not happen - this can only be an improvement !! :-))

And hardwood frames conduct vibration. I accept your theory that it conducts vibration away from the driver assembly (whereas MDF does not) but IME, it does not absorb these vibrations 100%. IE. you can feel the stiles - and the struts - vibrating with bass heavy music. Therefore if the ribbon cage is attached to the same frame the bass driver is attached to, it will get vibrated by the bass driver.

(I ignore the mid driver because that moves so little it does not generate any vibrations in its frame.)

But it gets better. His solution was to make a separate frame for the ribbon and then attach it to the main driver again. I know I'm a stupid Polak but am I the only one getting the pointlessness of this? If you feel your wooden frames when the speakers are playing they will be vibrating up a storm. (because they are absorbing and dissipating these vibrations) If the ribbon is in any way touching the midbass frame (which it appears to be) then you didn't separate anything and the problem never existed.

Correct - my first attempt allowed a pathway for vibrations to get into the mid/ribbon frame. It wasn't actually attached to the main (bass) driver frame but it was attached to the same base that the bass driver struts were bolted to. Thus vibrations were able to pass from bass driver --> bass frame --> bass struts --> stand base --> mid/ribbon strut --> mid/ribbon frame --> ribbon cage.

So I had to isolate the strut holding up the mid/ribbon frame from the stand base. Hoshi appears to have instead used 2 separate stand bases - so he solved the problem in a simpler manner. :-))

The ribbon cage is without question the most massive and costly thing magnepan makes. The ribbon is also held in it (and attached to it) by the most tenuous of means. Certainly it is making far more vibrational energy itself (which effects itself) than the midbass driver is somehow imparting to it, if it in fact can at all. (and which the facts we know about mdf would seem to indicate it can't)

I disagree the ribbon creates vibrations itself, which you can feel in its "cage" - let alone its hardwood frame (if it's a separate frame to the bass driver frame).

Regards,

Andy

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---