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Old 22nd March 2004, 01:31 AM   #1
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Lightbulb OHM Acoustics "Walsh F" Speaker remakes

Hello DIYers,

For along time i have been a lover of the OHM Acoustics speaker company. I was wondering if anyone on this site had heard of them and was wondering what there thoughts were on the company.

Another question is, has anyone tried to replicate there landmark speaker the Walsh F?

I know the speaker to begin with was particularly difficult to build. It was also fuzzy. But if you were able to set up the WALSH "F's" just right, they sounded like a million bucks. some saying it is the best speaker ever made.

I was wondering if anyone was able to replicate this unusual design and make a speaker using the WALSH technology.

Thanks.
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Old 22nd March 2004, 04:51 AM   #2
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The standing joke was that it took 200W to get the original Walsh speakers to make sound and 201W to blow them up.
The Ohm versions were poor copies. They were basically a one trick pony. They could do that weird where's-the-speaker imaging thing, but the sound quality was sad compared to other speakers. The shop I worked for bought something like two dozen pairs of the stupid things and we could hardly give them away. For all I know, they still have a pair or two.
The basic idea is simple enough--just turn a driver face down into a box so that you're listening to the back of the cone with no cabinetry. It images well, and is close to omnidirectional. So far, so good. The problem is the frequency extremes. The way they got anything like reasonable frequency response out of the original Walsh was to vary the makeup of the cone from (as I recall) metal at the voice coil to paper at the surround. Each ring of material had to be bonded to the next quite carefully. Note that the metal and bonding agents increased the mass of the cone considerably, and transients suffered as a result.
The Ohm speakers used really cheap drivers and treated them.
Of the two approaches, the Ohm strategy is going to be more practical to the average DIYer. I'd reccommend getting a case of really cheap "buyout" paper cone drivers from Parts Express--the 99 cent specials--and experiment with different treatments. Your goal is controlled cone breakup, which is a difficult horse to ride. Once you set different parts of the cone in motion, things are going to get complicated fast.
Suggestions for paper treatments: rubber cement, super glue, varnish, polyurethane, etc. Also consider the careful application of water to loosen up the paper fibers and make the cone more floppy. Your goal is to have the cone as stiff as possible up near the voice coil so that it acts like a tweeter. As the frequencies decrease, you'll need to assign more cone area to radiate.
You'll end up trashing a lot of speakers in the beginning, which is why I suggested starting with really cheap ones.
On the other hand, you might just decide that you like the sound of an ordinary driver upside-down, in which case you're done.

Grey
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Old 22nd March 2004, 07:17 AM   #3
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There was once a website of someone who actually did what Grey mentiones above. Mabe you will find it by using a search engine.

Regards

Charles
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Old 22nd March 2004, 01:56 PM   #4
vuki is offline vuki  Croatia
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I've listened to some German Physiks speakers and they sounded very good.
German Physiks
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Old 22nd March 2004, 02:05 PM   #5
hifi is offline hifi  Sweden
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The German physics speakers do sound good indeed, but I cant help think:

"Danger Will Robinson Danger!"



/ Mikael
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Old 22nd March 2004, 02:09 PM   #6
hifi is offline hifi  Sweden
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Sorry I almost forgot, here is some constructive input

http://www.audiodesignguide.com/full/conus1.html


/ Mikael
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Old 22nd March 2004, 02:15 PM   #7
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Congrats Mikael, that's the one I meant.

Regards

Charles
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Old 22nd March 2004, 03:13 PM   #8
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Interesting website you've got there. I hadn't envisioned actually disassembling the driver, since that leads into cone/voil coil alignment difficulties.
That said, here's a trick that will help keep the voice coil aligned. Once you've got the center dome off, you have access to the inside gap between the coil former and the center pole of the magnet. Take a piece of paper--ordinary notebook paper will do--and wrap it into a tube the same diameter as the gap. The goal is to wrap enough turns of the paper onto your tube that it fits into the gap quite snugly. You may have to try two or three times to get the right thickness to fill the gap, but don't worry about it, notebook paper is cheap. This gives two benefits. One is that it evenly spaces the voice coil in the gap so that it doesn't rub when you're done. The other is that it will hold the voice coil relatively still while you're gluing things to it.
Obviously, you'll need to remove the paper tube before trying out your new driver.
Note that removing the old cone and replacing it with a new one made from new experimental materials will change the effective mass and stiffness of the cone. As such, the T-S parameters go out the window. You'll need to measure the new T-S parameters of the driver yourself, then build a cabinet to suit those numbers, not the old ones.

Grey
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Old 22nd March 2004, 03:46 PM   #9
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Default OHM Walsh "CLS" Driver

Thank you for the quick replies.

From the way it sounds the Walsh F driver was an under designed speaker. I know that OHM still manufactures a Walsh model but they now use different technology. They are suppose to be better than the origional. They can handle more power, more sensitive, play louder, have better imaging, and are easier to drive. I have been told they arn't particularly hard to drive but thrive when they have good power. The problem with the "new" OHM Walsh's from was that they lacked microdynamics. However after reading a review on a pair of Blue Circle Audio BC8 amplifiers the impression of the Ohm Walsh was changed. This amplifier took ahold of the speaker and was able to transform them into a marvelous speaker. The person who reviewed them though the BC8's and the Walsh 300 MK2's were the best pairing of speakers and amps he had ever heard in the 12k price range. the speakers themselves cost roughly 4k with the amps around 8k.

Has anyone heard the Ohm's current Crop of Walsh speakers. Has anyone tryied to replicate or modifiy them? Are the new designs better than the origional?

http://ohmspeakers.com/CLSDbig.gif[/URL]

Thank you,
Microwalsh
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Old 22nd March 2004, 04:14 PM   #10
hm is offline hm  Europe
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Default ohm F + DDD driver

Hello,
I heard both:
Ohm F nice but slow, the driver is an 38cm Bass with a heavy
membran weight.
The DDD with a Horn is my solution:
http://www.hm-moreart.de/6.htm
The best room impression, fast and the bass very tight.
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