Woofer in Everest DD66000

[Brian DK]

The new Everest DD 65-66-67000 is the only and first model where the woofers dont play in the same
freq. Only one woofer meets the mid driver.
In all the other, Older models, both woofers meet the mid driver

Do any of you know why?

[Earl K]

The new Everest DD 65-66-67000 is the only and first model where the woofers dont play in the same
freq. Only one woofer meets the mid driver.
In all the other, Older models, both woofers meet the mid driver

Do any of you know why?

Actually from within the archives of older models, the 4435 also used a helper woofer ( which only reinforced the lower frequencies ) .

The "DD Everest" models ( that you've mentioned ) all have woofers similar ( in functional specification) to the 2234H ( found in the 4435 ) .

<> :)

[fiedel]

The new Everest DD 65-66-67000 (tel:65-66-67000) is the only and first model where the woofers dont play in the same
freq. Only one woofer meets the mid driver.
In all the other, Older models, both woofers meet the mid driver

Do any of you know why?

It might have been designed this way because you otherwise would get 3 transducers spaced quite far apart, which would give you dispersion issues at and around the crossover point.

Regards
Anders

[Don C]

In the Tech note: Improvements in Monitor loudspeaker systems, available here in the tech notes section, JBL tells us:
"For uses where even greater low frequency output capability with an attendant reduction in distortion is required, a double woofer system has ben designed. (model 4435).
Directional characteristics have been left intact by bringing the second woofer in at 100Hz only."

[Hoerninger]

Do any of you know why?
Bass reflex design with "helper woofer".

http://www.audioheritage.org/vbulletin/showthread.php?13171-Thiele-Small-Parameters-definitions&p=138072&viewfull=1#post138072
___________
Peter

[jpw]

A good guess would be that the crossover frequency (around 800hz plus or minus) on the 65-66-67 Everest is too high for both woofers to operate to without significant frequency response errors and stereo imaging distortion. When sitting equal distance in between the speakers, only the inside woofer, because of their horizontal placement, can be time aligned with the mid range driver. Older 43 series 4 way JBL's had a 8, 10 or 12 inch mid bass driver that crossed over in the 250-350hz area before the woofers (often 15 inch) could become too directional. The goal of the Everest's and other newer JBL's is to crossover the woofer to the mid range horn at a frequency where their radiation pattern (directivity) is similar. This provides the smoothest frequency response both on and off axis, something that JBL deems very important from their research and listening tests.

[frank23]

Actually this configuration has to do with the system and driver efficiency as well as radiation patterns. The 2234 from the 4435 is the same as the 2235 without the mass ring. Therefore the efficiency in the midband is higher, but the resonance frequency is a little higher with less bass extension. So the 2nd woofer is brought in below 100Hz to counter that effect and bring bass to the same level as the midband.

[audiomagnate]

It's actually a fairly common configuration, sometimes it's called a 2 1/2 way. My old SF Cremonas rolled off the lower woofer lower than the upper woofer IIRC.

[Brian DK]

Thanks for all your answers.
it makes sense :)

Not that I doubted Jbl's decision.
It an awesome speaker.
I never get tired of listening to my Everest :):):)