Posted by John Vogt on December 06, 2004 at 20:14:37:
I recently had my U1 panels(circa 1998) updated to the New Technology cores. What follows is the correspondence I've had with Dr. West regarding my impressions and experiences:
Soundlab West wrote:
> Dear John,
>
> Connie mentioned that you called. I've had computer problems as a result of attempting to set up a LAN system in my office, which has delayed my correspondence. I still haven't got it working yet, but at least I'm back on the internet and have been able to access my email.
>
> You mentioned in your note that your newly rebuilt panels are basically the same in sensitivity as before the update. There have been some people that have published on the internet that they have had large increases in sensitivity due to some panel changes that we made. This is true when comparing the technology that we used in the last two to three years. During this time we tried a new stator insulation and geometry that was supposed to provide ultimate reliability. Reliability in the past years wasn't terribly bad, but I just wasn't satisfied with it and felt that it could be much better. The cost was a decrease in sensitivity.
>
> During the last year, I found a material and a technique that would provide the very high reliability without compromising sensitivity. Your panels, before and after the update, bridged this period of lower sensitivity. However, your new panels have the new material and technique. To provide you with a brief explanation of this new approach, I found that the major reason that unexplained failures occurred in panels that performed perfectly at the factory, but failed weeks or months later, was due to air inside the insulation. The intense electrostatic field within the stator insulation can ionize the air, creating corona discharge, which is extremely oxidative and can eat through just about anything, given time. I found that most of the failures that occurred were the result of this failure mechanism, so the air must be eliminated. I'm now using a heat-shrink material that provides a glove fit over the stator wires, and eliminates any internal air. It requires the stators to be slowly heated under exacting conditions starting from one end to the other of the stator, so that any air is pushed out of the tubing as it shrinks. The results have been excellent, and the return to a higher sensitivity has been most welcome. I have not openly published this new technology, but others have done so on their own volition. The major advantage of the new technique is a product that has no inherent degradation processes.
>
> Sometime, probably during the coming year I may unveil a new backplate technology that will increase both the sensitivity and dynamic range of our products by a minimum of 6dB. I can do this because of eliminating the air-ionization problem. This has been a deterrent to the technology I'm in the process of developing. I wouldn't recommend the new approach to those who don't have the new panel technology.
>
> I hope that this adequately answers your questions. If not, please let me know. It's nice to hear from you.
>
> My warm regards,
>
> Roger West
>
>
message -----
From: John Vogt
To: Soundlab West
Sent: Tuesday, November 09, 2004 2:46 PM
Subject: Re: Rebuilt panels
Hi Roger,
Thanks for responding to my previous post.
I understand what your telling me as regards the panel sensitivity. I would have appreciated someone clarifying that although the new stator insulation is better there would be no other improvement compared to the panels I was currently using. I feel at this point that I've wasted almost $4k on an upgrade that really wasn't needed at this point in time.
I wouldn't have minded doing this with the new backplate technology but being your not even sure if your going to release this upgrade just makes it all the more irritating.
On another note, I also installed new bias supplies. These appear to operate a little different than the previous version I was using. Specifically, I can advance the bias level quite high without any cracking (although one core does arc around the perimeter in spots if the bias is raised to max, is this a problem?) but there is a general "hissing" or "frying" sound that emanates from the top 1/4 of the panel. Is this noise typical? To completely eliminate this the bias level must be reduced considerably with a significant reduction in sensitivity.
Lastly, while doing impulse testing for room correction I note that one panel has a significant depression from 4k-10k, on the order of 4-5db. I verified the toe in was the same for both panels but this condition still exists. What if anything can be done, short of returning the core, to correct this situation.
Thanks,
John Vogt
Hi John,
I don't think that you will be sorry, over the long run, that you had your panels rebuilt. The update opens the door to our efforts to increase the output intensity and sensitivity of the panels. The new backplate design is under way and will be realized. It's a matter of having the proper components manufactured for us by our sub-contractors. Unfortunately, lead times can be long and some iterations in design will probably occur as we optimize the design. As a result, it's not possible to predict when the new design will be ready to market. We're early in the project, but it will be accomplished, as we're committed to it.
Concerning the noise that you hear from the top of the panel, it's more than likely due to the higher output of the new bias supply (at full output). The new supplies are capable of increasing the potential to the point where it can arc from the copper foil on the periphery of the membrane. I'm sending you plastic insulating strips that need to be put on the mounting flanges of the frames to prevent this. That should permit you to turn the bias up without arcing. The noise that you mentioned should also disappear. I'll have Brett mail you the strips, along with directions, tomorrow. The U-1s that we've made in the last two years have plastic mounting flanges on the frames instead of steel for this reason. The insulating strips will work as well as the plastic flanges. It's unlikely that there's anything wrong with the panel. The panels were carefully tested here before shipping. The drop in output in the 4K to 10K region is a mystery. I'd suggest interchanging backplates to see if it follows the interchange. If the backplate interchange doesn't change things, I'd suggest interchanging the speaker positions to see, again, if the situation follows the interchange. Objects near the speaker can cause diffraction effects, and room modes are very capable of causing amplitude variations in the frequency response. Please let me know the outcome of these tests.
My regards,
Roger West
As things stand at the moment I have received and installed the plastic strips mentioned above. This has cured the arcing but not the constant "hissing" from the top 1/4 of the panel. I'm still trying to sort out this noise.
Am I unhappy at this point, yes, but I'm not going to editorialize, complain or pontificate on the experiences noted above except to say that those contemplating updating their panels should contact the factory to qualify/quantify what improvements can be expected in their particular situation.
John