LE 10s @ Orange County

[midlife]

I sent my L96 woofers to Orange County for new surround installs. Has their work been pretty good lately? thanks

[toddalin]

Yes, but just to be sure, I would still specify that the foams are to be installed on the backs.

I've had them do several speakers for me and never had a problem with their refoam jobs.

[jdurbin1]

+1 on both the quality of work, and always include the request to mount the surrounds from the rear if that is your preference. Their default process is to mount to the front of the cone in the absence of that request.

John

[rdgrimes]

Their default process is to mount to the front of the cone in the absence of that request.

John
No, this is not accurate. Their default is to rear-mount unless some condition prevents it. This was told to me by one of the techs there who was having trouble with a cone and called me to ask if I wanted it front-mounted. I've never asked for rear-mounting and have never gotten anything but rear-mounting.

[toddalin]

No, this is not accurate. Their default is to rear-mount unless some condition prevents it. This was told to me by one of the techs there who was having trouble with a cone and called me to ask if I wanted it front-mounted. I've never asked for rear-mounting and have never gotten anything but rear-mounting.

For the last several years, their policy has been to mount the foams on the side that they were originally installed on unless you ask for otherwise.

They did have problems in the past of mounting JBL foams on the front when not specifically requested on the rear, but this practice has long since been terminated.

Still, I always specify and get it in writing just so that there are no suprises.

[badman]

Agree with all above. Specify, but by default they should be doing it correctly.

Fortunately in either case, the surround contributes very little of the Qms, particularly in the z-axis, so it's more a 'historically correct' issue than a performance one.

[jdurbin1]

I have e-mail from Orange County in that period that say they mount from the rear as a default, wouldn't have volunteered that info otherwise.

This came up after I sent them a pair of either PR300 or 128H from one of my sets of 150A's that were originals and had the rotten foam mounted from the back.

When I got them back and noticed the surrounds were attached to the front of the cones, I wrote them a WTF? mail (polite one) asking why they had changed it, and got that response along with the suggestion to always state preference. I've done that ever since and been happy with the results. I also shuffled that pair off to a new owner, as they never looked "right" to me.

If that's not their official policy, someone there was out of sync with policy that day.

John

P.S. Just saw Toddalin's post above and it is possible that we're in agreement, just one or the other off a bit in terms of timing for that change. I know that was my experience of 3-4 years ago though.

[4313B]

Fortunately in either case, the surround contributes very little of the Qms, particularly in the z-axis, so it's more a 'historically correct' issue than a performance one.It's a performance issue that JBL takes fairly seriously. JBL has always been known for their above average attention to transducer design and manufacturing. ;)

"Mounting the software incorrectly in the hardware results in undesirable dynamic offset."

And if one wants to see just what a surround contibutes to Qms measure the parameters with it removed. :rotfl:

Oh wait... my bad... I read on the Internet somewhere that it doesn't affect the sound...:slink:

[badman]

It's a performance issue that JBL takes fairly seriously. JBL has always been known for their above average attention to transducer design and manufacturing. ;)

"Mounting the software incorrectly in the hardware results in undesirable dynamic offset."

And if one wants to see just what a surround contibutes to Qms measure the parameters with it removed. :rotfl:

Oh wait... my bad... I read on the Internet somewhere that it doesn't affect the sound...:slink:
The dynamic offset under discussion is probably based upon klippel analysis of the suspension linearity, which (or something similar) wasn't likely implemented until perhaps 20-25 years ago. And the spider IS the vast majority of the mechanical restoring force in the Z-axis which is what we're concerned with for offset, particularly in the case of the foam surrounds under discussion.

And your reference with the surround removed is an erroneous one, as it performs most of its mechanical influence in the X and Y axis (keeping the cone centered), and as such, when removed, you get cone sag and other effects that aren't relevant when a surround is properly mounted to either the front or the back.

But, I'd rather have the original location, and I'd specify it as such (despite the fact that current OC speaker repair policy is to maintain original location when possible), as I said in my post.

[Zilch]

OCS changed their policy largely in response to our bitching about it here, and the exchange is documented in this forum.... :yes:

[4313B]

The dynamic offset under discussion is probably based upon klippel analysis of the suspension linearity, which (or something similar) wasn't likely implemented until perhaps 20-25 years ago. And the spider IS the vast majority of the mechanical restoring force in the Z-axis which is what we're concerned with for offset, particularly in the case of the foam surrounds under discussion.

And your reference with the surround removed is an erroneous one, as it performs most of its mechanical influence in the X and Y axis (keeping the cone centered), and as such, when removed, you get cone sag and other effects that aren't relevant when a surround is properly mounted to either the front or the back.

But, I'd rather have the original location, and I'd specify it as such (despite the fact that current OC speaker repair policy is to maintain original location when possible), as I said in my post.I'm quite sure the proper people get my point...

[badman]

I'm quite sure the proper people get my point...
:banghead:

Care to address the question of suspension linearity (read: dynamic offset) as it pertains to the JBLs prior to the testing tools being available for it?
The role of this is in harmonic distortion, and accordingly, the audibility is debatable. Suspension related distortion is going to be more pronounced with more excursion, which is one of the points of going to big, JBL style speakers-to minimize excursion and associated distortion.

As far as I know, there were no tests present when the LE series speakers were manufactured with sufficient resolution to define the 'correct' mounting location of the surround. If you'd care to speak to something I'm missing, I'd be glad to hear it.

I'm not against doing it the right way, I'm all for it, but again, it shouldn't dissuade someone from getting a pair of classic JBLs just because a minor POTENTIAL issue exists with the mounting of the surround. Again, in this instance, it should definitely be specified to mount the surround in the original location.

[4313B]

I'm not against doing it the right wayOutstanding! That pretty much sums it up then. :yes:

[midlife]

My L96 woofers will be back in about a week, I'll see if I can get some pics posted...

[jdurbin1]

That's good to hear, thanks!

John


OCS changed their policy largely in response to our bitching about it here, and the exchange is documented in this forum.... :yes: