Hartley 24" - anyone have parameters?

[rdr]

I have had two in 20 cu ft sealed enclosures for many years. Now I want to build a proper enclosure as a summed sub woofer for just one of them. My guess is if I build transmission lines it does not matter much and all I have to do is make them as long as the 1/4 wavelength of the cut-off. But I still would like the parameters.

[DorinD]

http://www.ferrario.com/ruether/Audio.html

[JohnL]

The folks at Hartley were a little funny about T/S specs. Saying that because of the unique magnetic suspension T/S parameters didn't accurately represent the working of their drivers. I think someone subsequently tested the drivers and found the measured parameters were what would be expected. I've never seen a full set of T/s published anywhere for their drivers, but the LDSG published some abbreviated ones.
LDSG: Subwoofers 15" and Larger

Also note these specs are for the 218HS and 224HS, the newer 'heat pipe' style drivers.

John

[Paul W]

RDR,
I have a factory spec sheet on the 24 somewhere and I'm pretty sure xmax is spec'd as 3/4" p-p (unlike the LDSG spec). Like John, no T/S parameters were available from Hartley when I asked them. FS for both of mine is 13Hz which agrees with factory sheet and LDSG.


John,
At one time, I think you said you had a pair of Concertmasters. Can you describe -or better yet share a picture- of the damping material behind the driver? From years ago, I recall hearing about concentric rings of dissimilar materials, but my memory is a little too dim.
Paul

[JohnL]

I know I'm going to be sorry trying to do this from memory, but I just wanted to let you know I'll take a look and snap some photos for you in a day or two (I don't get home until late tonite).

I haven't disassmbled these, but I did poke around in the back. Mine are an older vintage, they still have alnico magnets and the woofers with dust caps. The 7" tweeter and 10" mid are in a sub cabinet with a back on it and a 1" dome tweeter on the back. The 24" is in basically a damped u-frame with fabric across the back. The damping would remind you of a low density rigid fiberglass, just not scratchy, and about 2" thick around the four sides. I don't recall there being a "boffle" on mine.

Disclaimer: That's from memory and subject to change upon photographic inspection.

John

[rdr]

In the 78 Audio Amateur. It is detailed on the construction of the labyrinth but does not explain the design.

I believe the Levinson systems used extremely large (45-50 cu. ft.) acoustic suspension enclosures, bordering of infinite baffles. Others have mounted them in walls or floors using the next room as a true infinite baffle. Hartley recommended a large open backed enclosure with some kind of acoustic absorbant. I think that is what John has? I am curious as to what the compliance of these are. I think the magnetic suspension is what allows these kinds of baffles.

Thanks for the information so far.

[DeonC]

Try these for size. A pair of Jensen Imperial horns for the Hartley 24" (see pics below). To see the plans, go here (the links are at the bottom of the page):
Jensen Imperial horns for Hartley 24"

Enjoy,
Deon

[rdr]

from my two 20 cu. ft. enclosures. Those are enormous. Maybe OK when I used to live in a loft. I'm now thinking about putting some such huge box in the basement with a floor opening. Such craziness would probably not be tolerated by my wife. And not portable when we move.

[Paul W]

If you can vent into the basement, do away with the box entirely and install a manifold IB in the basement. I've used mine in two different IB installations and SQ is really excellent.

My last installation was in a 14,000 cubic foot room so the Hartleys didn't have enough displacement for big movie bass but, in a smaller room or for music only, they are great.
Paul

[JohnL]

Here's a picture of the back