KLH-6 - Measurements

[GordonW]

I had an original 1973 pair of Large Advents... the first-generation with beveled front edges. Had foam blocks. So they were using foam, at least that far back.

Only the very earliest Advents used fiberglass... I've never seen one with fiberglass with build dates after 1972... and I've probably refoamed 200 pairs or more of these, over the last decade and a half...

Regards,
Gordon.

 

[Zilch]

The effect of foam vs. fiberglass in Large Advent is documented in my Advent Loudspeaker thread, and I think we here see why foam was used.

By the introduction of the Smaller Advent, they were back to fiberglass, and even then, underdamped by contemporary standards, as observed by John Atkinson in this 2006 retrospective:

http://www.stereophile.com/historical/506advent/index4.html

See Figure 4 there showing his nearfield bass response measurements. Are we on the same page?

If Carl and I are correct, there is a delicious irony here, very much at odds with common wisdom regarding these vintage classics, in which respect I am anxious to review Atkinson's measurements of Shacky's AR3a's, due for publication imminently.... :thmbsp:

 

[Zilch]

smaller advent

:thmbsp:

I'm continue to be amazed that the little Indignia matches or beats the much larger KLH-6 down to 35 Hz.

The AK Design Collaborative team did very well with the Indignia project, as just about anyone who has built them will attest. There's a lot of performance packed into those little fellas. :yes:

Just curious.....would like to see an Indignia port open vs. port closed graph to see how the LF response changes. Or, does the port adulterate the nearfield measurement?

It is possible to measure vented alignments nearfield, but you must measure the driver and vent separately, apply a correction factor for the vent diameter relative to the woofer piston diameter, and sum the two. It's not a "slam dunk" easy measurement that just about anyone can do like with closed boxes....

 

[gkimeng]

If Carl and I are correct, there is a delicious irony here, very much at odds with common wisdom regarding these vintage classics

Could you be a bit more specific about which "common wisdom" you're referring to? Is it: (a) that these speakers are "accurate," (b) that these speakers' response is "flat," or (c) that whatever it is that makes the sound of these speakers pleasant to those who prefer them is not showing up in the measurements that most people believe are what define a speaker's sound? Those are the ones that seem to be voiced most often, but I may be forgetting something else.

 

[lumpy]

Zilch is a riddle wrapped in an enigma

 

[Zilch]

Could you be a bit more specific about which "common wisdom" you're referring to?

I'm sayin' nothing 'til Atkinson weighs in on AR3a....

 

[gkimeng]

I'm sayin' nothing 'til Atkinson weighs in on AR3a....

Oh come on, that article is most likely already gone to press. You don't want to see if you can predict the results?

Well, until then, maybe we can work on filling in my list of "common wisdoms." I'm sure I must have missed one or two...

 

[Zilch]

Oh come on, that article is most likely already gone to press. You don't want to see if you can predict the results?

Them other guys are certainly willing to, and will surely blather about it for months.

Me, I just want to see the measurements.... :thmbsp:

 

[automojo]

I had an original 1973 pair of Large Advents... the first-generation with beveled front edges. Had foam blocks. So they were using foam, at least that far back.

Only the very earliest Advents used fiberglass... I've never seen one with fiberglass with build dates after 1972... and I've probably refoamed 200 pairs or more of these, over the last decade and a half...

Regards,
Gordon.

I have a original pair (OLA-Walnut) I got from my father, buil date Feb 4 1974, and they have pink fiberglass. This pair was bought new.

 

[lumpy]

Zilch, You ever listen to an original 25 year old Cambridge Soundworks 12 inch passive slave subwoofer? That would be a good canditate to turn into a full range system. Useable bass below 30 HZ. Cabinet is perfect for modification. Perhaps Kloss's best acoustic suspension woofer system. Certainly his last real no compromise design.

 

[Zilch]

Zilch, You ever listen to an original 25 year old Cambridge Soundworks 12 inch passive slave subwoofer? That would be a good canditate to turn into a full rage system. Useable bass below 30 HZ. Cabinet is perfect for modification. Perhaps Kloss's best acoustic suspension woofer system. Certainly his last real no compromise design.

For 2-way, they've also got to play nice through ~800 - 1 kHz, as well. That's the problem with vintage AR 12" woofers; they's apparently all done @ 1 kHz. 3-way's an option, but I don't do those often.

[I'll keep an eye out for a pair, tho.... :thmbsp: ]

 

[Pete B]

I have a original pair (OLA-Walnut) I got from my father, buil date Feb 4 1974, and they have pink fiberglass. This pair was bought new.

I also have a pair of OLA s that were bought new to our family in 1973 with pink fiberglass,
and another pair that look untouched internally also with pink fiberglass.

The vast majority if not all NLA s I've seen had foam.

And the Jensen 5002/12 went back to yellow fiberglass.