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JBL 4648A with SET's? [message #39329] Wed, 04 December 2002 06:07 Go to next message
jlharden is currently offline  jlharden
Messages: 94
Registered: May 2009
Viscount
You guys have me thinking again. The 2226J woofer is reported to be working well in a number of SET based systems. Has anyone tried the 4648A cabs off the the little amps? We'd gain our 3db(or is it 6?...depends on who you ask.) Would having the woofers paralleled also double the impedence at resonance? Seems it might...Can't win at this game!!! Some days I think I should just build a push pull EL34 amp!
Re: JBL 4648A with SET's? [message #39330 is a reply to message #39329] Wed, 04 December 2002 07:14 Go to previous messageGo to next message
BillEpstein is currently offline  BillEpstein
Messages: 886
Registered: May 2009
Illuminati (2nd Degree)
The 4648A has a total impedance of 8 ohms which kinda defeats the purpose. Plus it's a bass cabinet. So, while the SET's can do a job, it's better to try that EL-34 or maybe the Bedini 200/200 on Audiogon on the bottom and use the SET for the Martinelli Horns you lay on the top.
Re: JBL 4648A with SET's? [message #39332 is a reply to message #39330] Wed, 04 December 2002 08:56 Go to previous messageGo to next message
jlharden is currently offline  jlharden
Messages: 94
Registered: May 2009
Viscount
Hi Till,

I know the 4648 is a bass cabinet. I would be crossing over to the hf horn at 800 HZ. My point is that the dual woofer cabinet nets a good gain in system sensitivity which is a major plus when we're dealing with 3.5 watts. My concern is that that's a whole lot of speaker motor for a little triode to control. I know there's many of these 4648A enclosures around and wondered if anyone had tried running a pair of the 2226J's per channel rather than a single. Building up a dual 15" Pro Pi 4 in the Pialigned 3.9 cu. ft. enclosure would be one bad looking "little" cabinet, wouldn't it? That's where my system was at 1 year ago when I put all these 2226J woofers aside due to a gut feeling that they weren't going to sing with the set. Recent posts have indicated otherwise, at least in a single woofer cabinet. Who's got a 4648 with 16 ohm woofers and a Paramour? I think for some preliminary testing that might work. Perhaps one could tell pretty quickly if the amp "works" or if it rolls off everything and is "dynamically challenged". Hoping for some good feedback. Take care! Jerrod

Re: JBL 4648A with SET's? [message #39336 is a reply to message #39332] Wed, 04 December 2002 12:23 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18683
Registered: January 2001
Illuminati (33rd Degree)
A pair of 2226J's in parallel should act electrically very much like a single 2226H. The issue will be that peak at resonance, which is in parallel too, but it is a tank circuit that is paralleled, not a resistive load. Still, in many ways, the pair of 2226J's will act like a 2226H except efficiency is greater and cutoff is lower.
Re: JBL 4648A with SET's? [message #39339 is a reply to message #39332] Wed, 04 December 2002 13:46 Go to previous messageGo to next message
mikebake is currently offline  mikebake
Messages: 243
Registered: May 2009
Grand Master
Hmmm, well, I'm in favor of trying funky stuff to see if it works. My first reaction here was
a)don't do it
b)it's crazy
c)you need more power
d)wrong application of the 4648A
e)too high of a x-over point
f)JBL would laugh
g)then again, maybe not
h)WHY do this?

So anyway, if I was faced with all this it probably pretty well guarantees that I would try it..........just for the hell of it..and if it worked and sounded good, it would be all the more amusing!

Re: JBL 4648A with SET's? [message #39345 is a reply to message #39336] Wed, 04 December 2002 18:42 Go to previous messageGo to next message
jlharden is currently offline  jlharden
Messages: 94
Registered: May 2009
Viscount
Hi Wayne!

If I recall the Zmax of the 2226H was around 55 ohms, assuming two 2226J's are electrically very similar, the impedance at resonance shouldn't be an issue. The increased sensitivity is always a plus. I don't understand how two drivers offer greater extension than one though. I thought the actual response would be the same but a bit more efficient accross the bandwidth.

J

Re: JBL 4648A with SET's? [message #39346 is a reply to message #39339] Wed, 04 December 2002 18:48 Go to previous messageGo to next message
jlharden is currently offline  jlharden
Messages: 94
Registered: May 2009
Viscount
HA!

Thanks Mike!

I hadn't actually thought it that outrageous until reading your post. Problem is I have this extra set of woofers and need to do something with them. Have any Altec 811B's and 902's sitting around you want to trade for a pair of 2226J woofers? I'll have to see what develops, I can either run a single 2226 in a corner cabinet or run a pair in a reflex cabinet. Sensitivity is the same either way.

Tube friendly JBL's [message #39347 is a reply to message #39345] Wed, 04 December 2002 22:28 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18683
Registered: January 2001
Illuminati (33rd Degree)
I know that you've been through the archives for information on the subject, and have participated on many of the threads therein. But in order to make it easy for others interested in this issue, I suggest that the collection of posts about "tube friendly" speakers on this forum yields a lot of useful information.

As an aside, you'll notice that I used to consider the Professional Series offerings to be "tube friendly" until experience showed that their performance on SET amps was marginal in some cases. So maybe the 2226's work well for some people but not for others, as one might expect from its moderately high Zmax. It isn't terribly high, but isn't low either. It probably works well on some amplifier configurations and not on others.

Also, some very interesting articles on the technical issues surrounding interfaces between electrodynamic speakers and triodes have been written by Steve Bench and by Norman Koren. I suggest not only the articles directed by these links, but also the others at each authors' sites.

About how two drivers will interact, at low frequencies, they will combine and even act as acoustic mirrors to one another. It's like having them up against a room boundary in the way they reinforce one another. But as frequency rises, there comes a point where the two begin to form nulls in the room. The pattern looks like dual slit diffraction experiments, with hot spots and dead spots.

Re: Tube friendly JBL's; Only In Ohio [message #39348 is a reply to message #39347] Thu, 05 December 2002 02:27 Go to previous messageGo to next message
BillEpstein is currently offline  BillEpstein
Messages: 886
Registered: May 2009
Illuminati (2nd Degree)
There are only a few places in the world where 2A3 SET's will drive JBL's and Ohio is one of them. So we have that going for us.
Some other's are the empty diamond pipe's below the Witwatersrand, the caves beneath Eniwetok and the Mine's of Moria under the Dimrill Stair. But beware the Balrog!
Re: Tube friendly JBL's [message #39353 is a reply to message #39347] Thu, 05 December 2002 05:31 Go to previous messageGo to previous message
mikebake is currently offline  mikebake
Messages: 243
Registered: May 2009
Grand Master
Yes, I'd forgotten that as well, the comb filtering that would happen if you ran them both up high. JBL, when using two 15's i.e. JBL 4435 Studio Monitor, has one woofer just working from 100 hz on down. That is what you should do............
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