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JBL 2441Throat Diameter

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Posted on February 25, 2017 at 15:33:09
Jim Hodgson
Audiophile

Posts: 359
Location: New York City
Joined: March 9, 2006
Apologies in advance for what might be a ridiculously tedious question...

JBL product literature (link below) gives the throat diameter of the 2441 as:

"49mm 2in"

The fact is, however, that 49mm is significantly shy of 2" (by 1-59/64" ... so more than 1/16" but less than 1/8").

My question: is the 2441 compatible, throat-wise, with a horn that was set up for the TAD TD-4001, with its 49.2mm / 1-15/16" throat diameter? Basically, if the 2441's 49mm spec is to be believed, then it's a tiny bit narrow; and if its 2" spec is to be believed, then it's a tiny bit wide. Maybe someone here who knows the 2441 can shed some light?

Again, my apologies ... I know this is tedious. But, depending on tolerances, this may mean the difference between compatibility and incompatibility.

THANKS!

 

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RE: JBL 2441Throat Diameter, posted on February 25, 2017 at 18:45:22
EduardG
Audiophile

Posts: 240
Joined: May 30, 2002
You're absolutely right - the JBL 2441/2440 throat is smaller than 2" by just about 1/16. God only knows why JBL decided to make them this way. It has no impact on the sound and Dr. Bruce Edgar has routinely used a 2" forstner bit to manufacture mounting plates for 2" JBL compression drivers for his Edgarhorns.

 

RE: JBL 2441Throat Diameter, posted on February 25, 2017 at 19:34:42
Coner
Audiophile

Posts: 1843
Location: S.W. Washington state, USA
Joined: November 17, 2001
I think why JBL did that is to avoid any horn throat obstruction
edge do to mfg. variations and misalignment due to the side
play due to the bolt holes.

Or, am I overthinking this?.

 

RE: JBL 2441Throat Diameter, posted on February 26, 2017 at 11:00:07
Jim Hodgson
Audiophile

Posts: 359
Location: New York City
Joined: March 9, 2006
Thanks for the information / confirmation.

I'm wondering if the horn that I have in mind for these, which has a 1-15/16" throat opening (measured carefully -- not based on specs), is going to be too tight for the 2441? I guess that depends on how my particular drivers match up to the "smaller than 2" by just about 1/16" figure you just gave!

 

RE: JBL 2441Throat Diameter, posted on February 26, 2017 at 11:27:33
Jim Hodgson
Audiophile

Posts: 359
Location: New York City
Joined: March 9, 2006
I think that sounds totally reasonable.

It also gives effect to the idea that, if there is going to be a slight mismatch between driver throat opening and horn throat, better the driver throat opening be the smaller of the two ... with the preference for any "step" to be in that direction (i.e., narrow-to-wide as opposed to wide-to-narrow)? Isn't this correct?

 

RE: JBL 2441Throat Diameter, posted on February 26, 2017 at 12:57:33
Rod M
Web Geek

Posts: 10548
Location: So. California
Joined: March 1, 1999
Contributor
  Since:
March 1, 1999
I've used both TAD TD-4001s and JBL 2441s interchangeably with my Edgar Salad bowls and never noticed any issues. They're bolt on compatible.

-Rod

 

RE: JBL 2441Throat Diameter, posted on March 1, 2017 at 13:57:24
tomservo
Manufacturer

Posts: 6866
Joined: July 4, 2002
AS long as the step in size for increasing area is less than about 1/4 wavelength at the highest frequency of concern, the transition has no significant / measurable impact.
20KHz has a wl of about 5/8 inch fwiw.
Going down in size can act like a low pass or worse depending on how large it is.
Best,
Tom Danley
Danley Sound Labs

 

HOMs !!, posted on March 11, 2017 at 09:01:24
Rafaro
Audiophile

Posts: 116
Joined: July 30, 2005
Hi Tom:

In acoustics as you know "Not all that can be measured can be heard and not all that can be heard is usually measured" !! Psychoacoustis are rarely looked into or measured. According to Earl Geddes High order modes (HOM) can be produced by the inconsistencies of CDs to horns at the throat even if below the less than 1/4WL landmark standard.
Rafaro

 

RE: HOMs !!, posted on March 12, 2017 at 08:55:34
tomservo
Manufacturer

Posts: 6866
Joined: July 4, 2002
If and when present, their radiated energy can be seen in a high resolution polar plot or the time energy envelope measured at an angle of ones choosing off axis.

 

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