JBL 4-way pictures posting

[jbl_daddy]

Someone talked about a 4 way picture post.
4340
:)

[[email protected]]

I've always wanted to ask this, so excuse my stupidity if it's an obvious answer.

Why do some drivers have the dust cap recessed, rather than protruding like most speakers these days? Is it because of sound, or what...?

[rdgrimes]

Why do some drivers have the dust cap recessed, rather than protruding like most speakers these days? Is it because of sound, or what...?
Some have no dust cap at all.
http://www.audioheritage.org/vbulletin/image.php?u=606&dateline=1176230278

[Titanium Dome]

Some have no dust cap at all.
http://www.audioheritage.org/vbulletin/image.php?u=606&dateline=1176230278

..or the whole thing's a dust cap. ;)

[mech986]

Hi JBL_Daddy,

Thanks for the 4340 picture post. Could you do a favor and remove the slant lens and repost a pic? I'm curious to see how much higher the centerline of the midhorn is over the 2405. I always thought the drivers were in a horizontal line but that doesn't seem to be the case.

Do you have other overall pics of your speakers?

Regarding the dust or center caps: I think that some manufacturers have done studies on how the dustcap affects the overall performance or whether it has a negligeable affect. Since most (seems to be 99%) of woofers have a convex cap, its likely that its designed to work that way and taken into account when produced.

I also suspect that it is easier overall to apply and for repair. I thought though that some woofers (like in the L40) the cap was designed convex for a reason and sounds a bit different if repaired the other way.

I kinda like the way concave caps look and is alwys felt it might be a little stiffer. The convex cap could limit ultimate cone excursion though whereas the concave has much more room for movement absent the voicecoil mounted mass rings.

Why didn't JBL design the mass ring to fit around the voice coil circumference or vc/cone termination instead of inside the voice coil? Seems you could have the mass and not have a built-in stop limiter. Don't know.

Regards,

Bart

[4313B]

I kinda like the way concave caps look and is alwys felt it might be a little stiffer.I always liked the look of the concave dustcap on the LE10A and 2121; Unfortunately it causes undesireable breakup that the LE10H and 2122H with their convex dustcaps don't suffer. Regardless, some people survive just fine while listening to such systems as the Lancer 66, Lancer 77, 4340, 4341 and 4343. :)

Why didn't JBL design the mass ring to fit around the voice coil circumference or vc/cone termination instead of inside the voice coil? Seems you could have the mass and not have a built-in stop limiter.Actually the bottom of the mass ring and the spider are on the same plane, so if you are smacking the mass ring you are also hitting the spider. JBL still uses a mass ring in certain rare instances.

[JBL 4645]

jbl_daddy

Question?

I’m curious is the design of the JBL 4330 divided into two halves one for the low end and one for the midrange as I noticed the port hole is very narrow on the top half also I noticed the holes to swap around the UHF driver for mirror image is that how the 4330 works?

[JBL 4645]

..or the whole thing's a dust cap. ;)

I don’t thing there is whole lot one can do about dust these days. :D Except keep the home dusted and polished on daily basis.;)

[jblsound]

Some have no dust cap at all.
http://www.audioheritage.org/vbulletin/image.php?u=606&dateline=1176230278
Actually, those inverted domes are Elliptical Oblate Spheroidal (EOS) waveguides, due to their unique shape.

[Titanium Dome]

^^^^^^ That's just an inverted dome.

Take out the Ti drivers in the following pictures, and these are EOS Waveguides.

[hjames]

4340 and 4341 are basically the same speaker - same cabinet and drivers, but the '40 is biamp only and the 41 wasn't.
many of the big 4 ways had two possible locations for the 2405 slot driver - you move it as needed for a mirror imaged pair.

See - 4340/41 reference thread ...
http://audioheritage.org/vbulletin/showthread.php?t=16493


I put some photos of the interior of the cabinet online right after I bought my set (may07), but can't find them right now to show you.

The 10 inch Mid-Bass driver has a small sealed chamber behind it within the main cabinet space (some folks here call it a doghouse), but otherwise its one large chamber for the big woofer to use.

The ports are in the main chamber, not the doghouse.


Question?

I’m curious is the design of the JBL 4330 divided into two halves one for the low end and one for the midrange as I noticed the port hole is very narrow on the top half also I noticed the holes to swap around the UHF driver for mirror image is that how the 4330 works?

[JBL 4645]

Oh, right I was guessing that the small narrow hole at the top was for the 10” some type of port that along with swapping around the UHF driver. Pictures of it inside please let’s have look lets all have peek for those of us who don’t own one.

Isn’t there a custom model that uses 18” 15” 12” 6” and so on LOL now how tall would you think that would be?:D With a HF horn I think it would be close to 7 feet! LOL

[jblsound]

^^^^^^ That's just an inverted dome.

Take out the Ti drivers in the following pictures, and these are EOS Waveguides.

Yes, they are the EOS
But according to this 2002 review of the PS, by Gordon Holt, JBL also refers to the cones as EOS.
Here is one paragraph from that review:

I put "cone" in quotes because the Performance system's diaphragms aren't cones at all, but what JBL calls "Elliptical Oblate Spheroidal (EOS) waveguides." What the hell, you might well ask, are those? An elliptical oblate is a flattened sphere, like a beach ball with someone sitting on it, and a spheroid is a shape that's almost a sphere but isn't quite. Imagine the flattened sphere with three fourths of its height sliced off, and that's about the shape of the Performance's diaphragms.
http://ultimateavmag.com/speakersystems/31/

[jbl_daddy]

Attached are the pictures of the horn with the lense off.

PS. does the other speaker count as a 4 way?:barf:

Just kidding

[Titanium Dome]

Yes, they are the EOS
But according to this 2002 review of the PS, by Gordon Holt, JBL also refers to the cones as EOS.
Here is one paragraph from that review:

I put "cone" in quotes because the Performance system's diaphragms aren't cones at all, but what JBL calls "Elliptical Oblate Spheroidal (EOS) waveguides." What the hell, you might well ask, are those? An elliptical oblate is a flattened sphere, like a beach ball with someone sitting on it, and a spheroid is a shape that's almost a sphere but isn't quite. Imagine the flattened sphere with three fourths of its height sliced off, and that's about the shape of the Performance's diaphragms.
http://ultimateavmag.com/speakersystems/31/

I know Holt's article inside and out and linked to it multiple times here at LH and elsewhere. He's incorrect on that point. He tripped up on the nomenclature. When in doubt, go to the source, JBL.


Pure-titanium, high-frequency-transducer domes with neodymium magnet structures are ultralight to accurately reproduce lightning-fast sounds like cymbal crashes, yet extremely rigid to eliminate distortion and ear fatigue in the transition between the midrange and high-frequency bands.

Elliptical Oblate Spheroidal™ (EOS) waveguides were first developed for our JBL Professional LSR studio monitors. They enable Performance Series speakers to evenly disperse high frequencies and create precise stereo imaging over a wide listening area.

Pure-titanium, inverted dome midrange transducers seamlessly blend with the titanium dome tweeters by offering nearly perfect pistonic motion that eliminates uncontrollable flexing found in conventional cones. The inverted dome is driven precisely at its center, which cancels resonances inherent in cone materials. The result is ruler-flat frequency response well beyond the crossover point.

Titanium-alloy, inverted dome low-frequency transducers deliver precise, undistorted bass reproduction that matches the titanium tweeters and midranges. The powerful neodymium magnet provides its own video-shielding, allowing flexible placement, even near video monitors. Cast-aluminum frames remain rigid even at the highest volumes, avoiding distortion found in some other speaker designs. And aluminum doesn't affect the magnetic flux, so that driver movement is precise and unmuddied.

http://www.jbl.com/home/products/product_detail.aspx?prod=PT800BLK&Language=ENG&Country=US&Region=USA&cat=BFS&ser=PER

[jblsound]

I know Holt's article inside and out and linked to it multiple times here at LH and elsewhere. He's incorrect on that point. He tripped up on the nomenclature. When in doubt, go to the source, JBL.

Like you, I've read that info many times.
But I think he is right about the shape of the inverted domes. They're certainly shaped more like the EOS waveguide than a typical cone.

I've always thought that the description he used for the transducers was some info he got from JBL at the time he got the system to review. I don't see how he could confuse the EOS waveguides around the tweeters with the midrange, midbass drivers. The EOS are so obvious, and not the first time he would have seen them. But I suppose anything is possible when one starts to write a review.

[Fred Sanford]

Like you, I've read that info many times.
But I think he is right about the shape of the inverted domes. They're certainly shaped more like the EOS waveguide than a typical cone.

I've always thought that the description he used for the transducers was some info he got from JBL at the time he got the system to review. I don't see how he could confuse the EOS waveguides around the tweeters with the midrange, midbass drivers. The EOS are so obvious, and not the first time he would have seen them. But I suppose anything is possible when one starts to write a review.

If he was correct, wouldn't the inverted dome drivers not be round?

Oblate Spheroid
An oblate spheroid (http://encyclopedia.thefreedictionary.com/spheroid) is a rotationally symmetric (http://encyclopedia.thefreedictionary.com/rotational+symmetry) ellipsoid (http://encyclopedia.thefreedictionary.com/ellipsoid) having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it.


je

[jblsound]

If he was correct, wouldn't the inverted dome drivers not be round?

Oblate Spheroid
An oblate spheroid (http://encyclopedia.thefreedictionary.com/spheroid) is a rotationally symmetric (http://encyclopedia.thefreedictionary.com/rotational+symmetry) ellipsoid (http://encyclopedia.thefreedictionary.com/ellipsoid) having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it.


je
I does look like a flattened beachball, with the depth less than the diameter, but ya, its edge is not oval like the tweeter EOS.
I just don't believe the description he wrote is something he just picked out of thin air. But wko knows?