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Petter Persson 11th February 2009 06:10 PM

T&S Lowther PM2A
I measured T&S parameters of one om mine Lowther PM2A and thought it would be of general intrest:

Sd 209 cm2
Vas 36 liters
Fs 58 Hz
Mmd 12,9 g
Mms 14,7 g
Re 8,8 Ohm
Bl 20,2 N/A

Cms 0,588 mm/N
Rms 1,87 Ns/m

Qms 2,68
Qes 0,107
Qts 0,103

Close up

Note the cone breakups at 950 Hz and 2300 Hz.

Regards / Petter

Nelson Pass 11th February 2009 07:26 PM

Yup, that's a PM2A! It's not my favorite - I'm currently trying to
decide on the PM6A (16 ohm, Ticonal) vs the PM5A (bigger magnet).

I have the PM4A's coming, and I'll let you know eventually.


MJK 11th February 2009 07:34 PM

Measurements of the T/S parameters for my Lowther drives can be found here.

My pair of PM2A's seem to be a little bit different.

Petter Persson 11th February 2009 07:51 PM


Yup, that's a PM2A! It's not my favorite
Not mine either. Thatīs why they are in the book shelf, using
compression drivers instead for mid and highs. My pair is for sale
and i thoudht i would measure them before itīs to late.

There are a big differences in the Bl product between my sample
and those at quarter wave.

Scottmoose 11th February 2009 09:02 PM

Ye Gods! I make that as a 1.126KHz Fhm. That's a unit demanding a front-horn if ever I saw one... or a very large dose of series resistance / current source amp.

One wonders just what level of unit-to-unit consistancy Lowther achieve. No offense to them (although they're not exactly my cup of tea), and other manufacturers certainly have issues in this respect too. But one wonders...

hornophile 11th February 2009 09:22 PM

new or old version
your pm2A is the old version or the new one ?

I have the old version. It's on the shelf too...

MJK 11th February 2009 09:39 PM

All of my drivers are the new version with the rolled whizzer cones. I used my pair of PM2A drivers in my large OB for quite a while and they sounded very good. Personally I like the DX drivers the best but I did not have any complaints about the PM2A's sound. I have also tried my PM2A's in my ML TL with a variable correction circuit and it sounded very nice, I prefered it to the PM6A's in the same ML TL. Based on the T/S measurements, there is something very different in my PM2A drivers and the ones in the original post.

Petter Persson 12th February 2009 06:25 AM

Itīs the old version, and theay are probably reconed aswell since they the cone structure differs from the other PM2A I've seen.

CLS 12th February 2009 07:30 AM

I'm no expert of Lowther, but the frames look like AER to me. And there're no raidal pressed marks on the main cone, some suspicious concentric marks instead.

jdunham 12th February 2009 08:55 AM

Those are Lowther frames, not AER. They're the ones they used after the original square frames. I have some PM6A's with the same frames from the 1970's.

The cones look like they are from a "C" driver, not an A or DX driver. So probably are re-coned.



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