Geometrically Challenged Fifteen

[speakerdave]

This question has been hanging in the bat cave of my mind for some considerable time, so I have decided to ask it.

What is it that would cause an audio engineer to prefer, not specific to any model as far as I know, the 10" woofer to the 12" and the 14" to the 15," as has often been mentioned here?

#2. I assume the comment that the 150xAL woofer series is the first fifteen that is not geometrically challenged is related to the question above.

Thanks in advance.

[4313B]

It was a comment made while discussing what might be the reason why the 2235H wasn't a big favorite with some people. The comment was made by its designer.

I personally liked the 2235H just fine. It did its job during its era.

There are tons of 2235H's out there so someone else must like them too.


The ten was tight and true compared to the twelve and worked a bit better with boundary reinforcement. The twelve offered increased output.

[speakerdave]

I suppose similarly, back in the day Acoustic Research had in its line the AR5 with the midrange and tweeter of the AR3a but a ten inch woofer since there were those who thought the AR3a bass-heavy in some rooms.

Well, OK, but . . . .

[subwoof]

smaller cones have ( usually ) lower mass therefore greater acceleration compared to larger cones when used on the same size amplifier ( with it's defined output impedance / geometry ).. think damping factor here.

And then there's the relationship to the next component above and *it's* response that will color the subjective "sound"

Not to mention the different size enclosures, tuning, baffle contours and the wife-dictated placement and the mass of plants placed upon said enclosure.

In short, WAY too many variables to even consider a valid reply let alone treatise.

sub

[speakerdave]

:)

I would not not like to have to choose either exclusively myself. I can certainly see how with a given motor, voice coil diameter and cone material that at outputs less than the marginal capacity increase advantage goes to the incrementally smaller driver. It's that it has come up a number of times, and I thought maybe there was something more arcane and that perhaps someone could drill down a little and show us how a confluence of trend lines and moving ratios or whatever beatifies an unchallenging geometry.

[honkytonkwillie]

14 is kind of an ugly number. The notion of 14" doesn't aesthetically fit well with 1", 2", 3", 4", and 6" drivers that may be working near by. Converting it to 35.6cm doesn't improve things either.

I'm weird like that.

[speakerdave]

Ha! Numerology!! It never occurred to me!

[4313B]

:)

I would not not like to have to choose either exclusively myself. I can certainly see how with a given motor, voice coil diameter and cone material that at outputs less than the marginal capacity increase advantage goes to the incrementally smaller driver. It's that it has come up a number of times, and I thought maybe there was something more arcane and that perhaps someone could drill down a little and show us how a confluence of trend lines and moving ratios or whatever beatifies an unchallenging geometry.At the time I attributed it to the cone assembly. Out of the LE10H, 128H, LE14H, 2235H and 2245H only the 2235H used a mass ring instead of aquaplas. If I remember correctly, of the LE14H, 2235H and 2245H, only their cone assemblies (including three different geometries) and frames varied, the voice coils and magnetic return assembly were equivalent. There was a time when I cared enough to remember and could have answered definitively. ;)

I believe the same held true with the LE10H and 128H, only the cone assemblies and frames varied. I do know that JBL added or subtracted a few coil turns from both the LE10H and 128H at some point to achieve whatever changes they were looking for.

In any case, transducers such as the 1501Fe, 1501AL, and 2216Nd really are "light years better". And that doesn't have to be a problem.

[speakerdave]

At the time I attributed it to the cone assembly. Out of the LE10H, 128H, LE14H, 2235H and 2245H only the 2235H used a mass ring instead of aquaplas. If I remember correctly, of the LE14H, 2235H and 2245H, only their cone assemblies (including three different geometries) and frames varied, the voice coils and magnetic return assembly were equivalent. There was a time when I cared enough to remember and could have answered definitively. ;)

I believe the same held true with the LE10H and 128H, only the cone assemblies and frames varied. I do know that JBL added or subtracted a few coil turns from both the LE10H and 128H at some point to achieve whatever changes they were looking for.

In any case, transducers such as the 1501Fe, 1501AL, and 2216Nd really are "light years better". And that doesn't have to be a problem.


Thanks for that.

[subwoof]

I kinda like that monikor..:)

the 2245's mag assy was scaled larger ( the deeper 2220 top plate and thicker E series 7/8 magnet ) but the coil assy would fit ( and is used in the 136HS woofer actually ) in any of them.

And I prefer to call the "14" either a 12.75 or 13.25 depending on the model just to confuse people..HA
sub

[4313B]

It is a moniker that JBL has applied to many favorite systems, parts and transducers.
No Longer Serviceable has become quite popular too.

[ivica]

At the time I attributed it to the cone assembly. Out of the LE10H, 128H, LE14H, 2235H and 2245H only the 2235H used a mass ring instead of aquaplas. If I remember correctly, of the LE14H, 2235H and 2245H, only their cone assemblies (including three different geometries) and frames varied, the voice coils and magnetic return assembly were equivalent. There was a time when I cared enough to remember and could have answered definitively. ;)

I believe the same held true with the LE10H and 128H, only the cone assemblies and frames varied. I do know that JBL added or subtracted a few coil turns from both the LE10H and 128H at some point to achieve whatever changes they were looking for.

In any case, transducers such as the 1501Fe, 1501AL, and 2216Nd really are "light years better". And that doesn't have to be a problem.

Hi 4313B,

Many thanks for the "historical overview" of the JBL ancient, old school drivers such as 2231, 2235, 2245, 128H.
Unfortunately, new, larger top plate size and later dual VC, became almost unavailable, with the price of gold-maden swiss watch, personaly I think that using today technology that they are overpriced, but fortunately some of the forum member can afford them, and are willing to presetn us their experience.

My wonderqs about new 150x drivers are mainly focus on the cone construction and their materials, beliving that improve their tonal chacter over old school 22xx drivers.
What would happen if say 1501 cone is put in 2235 or E140 basket and their VC.

regards
ivica

[tomee]

At the time I attributed it to the cone assembly. Out of the LE10H, 128H, LE14H, 2235H and 2245H only the 2235H used a mass ring instead of aquaplas. If I remember correctly, of the LE14H, 2235H and 2245H, only their cone assemblies (including three different geometries) and frames varied, the voice coils and magnetic return assembly were equivalent. There was a time when I cared enough to remember and could have answered definitively. ;)

I believe the same held true with the LE10H and 128H, only the cone assemblies and frames varied. I do know that JBL added or subtracted a few coil turns from both the LE10H and 128H at some point to achieve whatever changes they were looking for.

In any case, transducers such as the 1501Fe, 1501AL, and 2216Nd really are "light years better". And that doesn't have to be a problem.


Thanks for that run down - over various threads scattered about you've commented on the commonality of some of the 4" and 3" VC woofers. Is the 2108 also an LE10 magnet and coil? Or maybe the 2121 coil? My guess has always been 'yes it is'..

Personally, I don't see the LE14A and those other drivers as using 40+ year old technology because it was 25 years ahead of its time when it came out - IMHO nothing made by other makers at the time can match what JBL was doing in the early 60s. It looks like they're keeping that tradition of being ahead of the curve with these new drivers, both in performance and expense. Eventually it'll all trickle down to 'the rest of us'.. haha.