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Lowther PM6A xFonken?

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Would the Lowther PM6A, 15 ohm silver (Qts .381), be a candidate for a trapezoidal Onken style enclosure?
 

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frugal-phile™
Joined 2001
Paid Member
I am surprised, but yes, given those numbers it will get in the high 50s F6/low 50s F10 in 35 litres — i already have a 35 litre trapezoid for the A12pw & FF225wk that could be adapted.

It won’t deal with the rising on axis response, but Martin’s measures suggest that flattens out off axis.

dave

dave
 
Thanks. Interesting. I would've thought a driver that large would go lower.

I made a pair of Martin King MLTLs for someone else's Lowther DX4 back in May, and was so impressed with the build quality of those drivers that it made me curious to hear them (haven't gotten the chance yet). And I've loved the Alnico drivers I've heard in vintage systems, so PM6A seems like a natural choice (plus its frequency response is the flattest of the entire product range).
 
I wasn't able to post in the Planet 10 picture gallery, so here are the trapezoidal Onkens for Lowther PM6A. Special thanks to David for the bespoke design. I've only listened for a couple hours but they sound superb.

18mm Baltic Birch plywood with solid red oak vent spacers. Finish is 12 coats of amber shellac and a top coat blend of orange oil, beeswax, and carnauba wax.

Also pictured are mFonkens for Fostex FE103Sol and MarkAudio Alpair 10P.

Some thumbnails appear sideways but are corrected when you click to view the larger version.

Those interested in more pics as well as thoughts on build process and creativity can follow me at Instagram: @boisetverre.
 

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frugal-phile™
Joined 2001
Paid Member
Jeff,

Thanx for the email with the pictures, these are gorgeous.

With positive initial comments i am eager to hear what you think of the sonics as they break in. Enclosures for Lowthers that are not big horns are rare and hopefully this design challenges that notion.

Since there is only one, it is called a Low-Ken or Low-KenPM6T, if more follow it may well get a longer designation.

dave

PS: there are 2 gallery threads in the P10hifi forum, one stickied where only i can transfer posts that just have pictures and a longer one with comments below.


miniOnken/Fonken Picture Gallery

I have copies your post from the FR gallery to those 2 threads.
 
Thanks! I will definitely report on the break-in process as noticeable changes occur, with a thorough review at some point. I'll say right now that these by far present the most "air" or "sparkle" (or other audiobabble synonym) of any speaker I've heard. Also percussion -- the hi-hat and cymbal in bebop: Wow! Otherwise they're just so musical and involving, with microdetail that's almost kinda scary.

Timbre of acoustic instruments and jazz guitar is gorgeous.

Also they handle complex passages remarkably well.

These will become a family heirloom.
 
Bass extension is very adequate. It's musical and detailed. Not quite the umph of the A10P in Mar-Kens, but I certainly don't feel like anything is missing. There is no "shout" at all. The frequency spectrum is beautifully balanced without an overemphasis on any one part of the range. I've heard DX4's in a pair of transmission lines that were definitely tilted toward the treble, but not harshly so. In contrast, the PM6A in Low-Kens are perfectly balanced, to my ears.

I really do wish we lived closer so that you could hear them.

Bass did seem to fill in over a couple hours last night as I listened to jazz and funk (Jimmy Smith, Medesky Martin & Wood, Miles Davis) as well as contemporary rock/electronic (Atlas Sound, Grizzly Bear, Beach House). As of right now the Lowthers don't even have three hours on them, though.

I'd guess they're strong down to 55Hz but I haven't measured. Maybe it's time to break out the measuring microphone I ordered years ago but have never set up. Any suggestions on how to take measurements in-room would be most welcome. My instinct is to put the mic at the listening position to measure real-world frequency response, but maybe there other suggestions?

Jeff
 
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very interesting, this silver coil PM6A is the (only) one Lowther driver I would consider trying and my curiosity about this legendary driver goes back many years, before I was DIY savvy. Don’t see them here much due to their price so hard to see a consensus opinion developing. I remember the late Sakuma-san liked his Lowther drivers too, even had one mounted in a beer keg if I remember correctly, said it was the tone he had been searching for.

Since I have the A10.3Ms and access to a friends A10Ps your comparison with the A10p is relevant and lends some context to your impressions of this Lowther. I might yet grab a pair, perhaps even consider a FAST version; it’s fun to consider new projects.
 
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Here's a couple videos I took with my phone. The sound quality is not great but they'll give you a sense of the bass capabilities. The first is The Flaming Lips, "One Night While Hunting for Faeries and Wizards and Witches to Kill" from Oczy Mlody. The second is "The Lemon Song" from Led Zeppelin II.

Trapezoidal Onken with Lowther PM6A 02 on Vimeo

Trapezoidal Onken for Lowther PM6A on Vimeo

In both videos, a CD player is plugged directly into a self-designed single-ended triode-strapped 6L6 amp (1.3 watts) with the volume knob at the halfway mark.

This project challenges the notion that Lowthers are only good for horns and open baffles, and also shows that they can rock with plenty of bass! The audio doesn't capture how impressive the bass sounds. It was shaking the house and angered my kids who were trying to watch cartoons.
 
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