Different magnets. I have used DX3 in large-ish bookshelf BR/sealed, PM2A in Fidelio rear-opening horn, and PM6A in TLonken/aperiodic/sealed. They have low-ish Qts. Highly efficient, electrostatic-like fast, and extremely dynamic sound. Very different from Fostex.
Which of these drivers do you like the most?
You have used different boxes but you can give us a feel for what they are good at.
I have a Pass ACA amp with the Feedback loop out so the output impedance is 12ohms, maybe this would help. ?
Picture of the Fidelio PM2A Ticonal https://www.diyaudio.com/community/...d-options-recommendations.388862/post-7087076
Picture of PM6A "360" https://www.diyaudio.com/community/threads/replace-jordan-jx92s.394245/page-2#post-7230251
DX3 and DX55 on another continent...
The Fidelio PM2A are of course best, as in sounding balanced and realistic, but I'm not getting ultra detail out of them. Amps: YBA integrated; 300B SE with Ediswan 6DJ8 rest Chinese tubes.
The 15ohm (not silver) PM6A has been a work-in-progress; bass is acceptable in the 17L 1.5m TLonken, and with double-notch (1.5mH||2.7uF||15ohm @ 2.5k) -> (0.47mH||0.68uF @ 8.7k) finally realistic-sounding and actually relaxing (!) to listen to, though still rather "dry". Comp with other 8" fullrange https://www.diyaudio.com/community/...ile-city-of-22m-laid-flat.393338/post-7266571
The DX3 on SE tubes were not ear-bleeding like my PM6A. DX55 plus twin subs worked very well until one driver failed.
Given these have foam surrounds of unknown life, and are rather finicky or fragile, I can't really recommend them (unless I worked them better).
Picture of PM6A "360" https://www.diyaudio.com/community/threads/replace-jordan-jx92s.394245/page-2#post-7230251
DX3 and DX55 on another continent...
The Fidelio PM2A are of course best, as in sounding balanced and realistic, but I'm not getting ultra detail out of them. Amps: YBA integrated; 300B SE with Ediswan 6DJ8 rest Chinese tubes.
The 15ohm (not silver) PM6A has been a work-in-progress; bass is acceptable in the 17L 1.5m TLonken, and with double-notch (1.5mH||2.7uF||15ohm @ 2.5k) -> (0.47mH||0.68uF @ 8.7k) finally realistic-sounding and actually relaxing (!) to listen to, though still rather "dry". Comp with other 8" fullrange https://www.diyaudio.com/community/...ile-city-of-22m-laid-flat.393338/post-7266571
The DX3 on SE tubes were not ear-bleeding like my PM6A. DX55 plus twin subs worked very well until one driver failed.
Given these have foam surrounds of unknown life, and are rather finicky or fragile, I can't really recommend them (unless I worked them better).
p.s. At 5-10% of the cost of Lowther PM2A or Fostex F200A, my "drum paper" Hifi-bird 5.5" in oak 10L 1.3m TLonken, played last night "straight-through" -2 A-/A+/A+ and tonight notched (0.3mH||2.7uF @ 5.5k) -2 A/A+/A. I wonder if Markaudio Alpair 12P might be as dynamic and articulate.
You could make the lowthers sound high end with covering the diaphragm from both sides with thin aluminum foil, current drive amplifier what reduces distortion by 10 to 20db and a dsp or even Fir correcting for the time fault due to backloaded horn length
In many senses the Fostex FExx6 drivers are inspired by drivers like the Lowther. FFxx5wk are not.
Seems the PM6 are closer to FFs tha the FEs like (most?) of the others. Most like to be in a horn and used with a high R amplifier. If it works in a reflex it is less “old skool”
dave
This is the my notes from ACA thread,
Okay ACA feed back resistors R11, R12
Increasing feedback will reduce overall gain
But lower output impedance. Papa Pass said to change R12 to 150k , gain will be about 20 ,the 6.5ohms. Feedback loop out gain 23, 12ohms.
So I simply removed R12. The Lowther DX3 on a open baffle apparently had more bass with this change.
Okay ACA feed back resistors R11, R12
Increasing feedback will reduce overall gain
But lower output impedance. Papa Pass said to change R12 to 150k , gain will be about 20 ,the 6.5ohms. Feedback loop out gain 23, 12ohms.
So I simply removed R12. The Lowther DX3 on a open baffle apparently had more bass with this change.
Short version is the C series are their entry-level drivers with ceramic (ferrite) magnets. DX is the next step up, with a motor based around neodymium magnets: generally as you move up the numerics (2, 3, 4), then in like-for-like coil impedances & types (see below) the motor power increases & Qe / Qt decreases. EX units are basically the DX drivers with a cover over the back of the motor assembly; typically even lower Q values. A series are in effect their most expensive models with AlNiCo motors; usually middling in terms of outright magnet strength. There is, as noted, some variation in there, but as a general guide it holds.
Qt you can see for yourself, since they publish the data for each unit in 8ohm and 15ohm versions, and with aluminium & silver coil windings. In general, the silver coils tend to provide a slightly flatter frequency response, likely through extra mass in that part of the powertrain & often a slightly higher Q.
They are similar to equivalent sized Fostex models in that they are 8in whizzer cone wideband drive units, but that's about all. Lowther have been around since the 1940s (to a point, 1930s if you stretch the definition) so Fostex come a lot later. Much more expensive, hand-built in the UK, and with a few exceptions, they are basically horn drivers intended for use with amplifiers that have either a high output impedance e.g. a typical SET, OTL or similar, or adjustable output impedance as was not uncommon back in the day.
I have listened to PM2A silver in Hedlund horn.
They were compared to the B&W 802D3. I thought they were more organic. Very good rating.
I thought the PM6A was just okay. But it probably depends on music selection and box selection.
PM2A ;
B&W 802D3 ;
They were compared to the B&W 802D3. I thought they were more organic. Very good rating.
I thought the PM6A was just okay. But it probably depends on music selection and box selection.
PM2A ;
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I would be remiss if I did not mention that Dave has designed a miniOnken for the 8 ohm PM6A. It's a complex build and so, for the moment, remains on my "To Do" list, but it is available for anyone else interested, I believe.
I don't know why but the Markaudio taobao store currently lists no CHP, unfortunately.
and the 16Ω copper & 16Ω silver VC PM6.
Currently going thru a revision. Bob Berner is building a pair and is finding a few glitches.
dave