PMC OB1 clone

[vincentrubble]

Does anyone know what 6.5"/170mm bass driver PMC uses in their OB1 speaker? It looks like it could be a Peerless 830946 or possibly a Morel HU631. PMC's web site says it is a doped 170mm driver with cast magnesium chassis. This would indicate to me that this is a paper coned woofer. Also, PMC seems to like using the Typhany Group's (Vifa, Peerless & Scan-Speak) drivers. Any suggestions? I have already selected the Scan-Speak R2904/7000 tweeter & ATC SM75-150S midrange and am now trying to pin down which woofer to use. Any ideas are more than welcome. I am using Martin King's transmission line tables to help out with the design. Has anyone used them before? They look like he really knows what he is doing.
Thanks to all,
John

[Tenson]

Hi,

PMC do not use standard transmission line design ethos. So with a different midrange, tweeter and transmission line design it will likely sound nothing like the OB1 I'm afraid. Still probably sound very good though!

[vincentrubble]

Thanks for your reply.

I have emailed ATC and Solen (ATC's Canadian distributor) to see if there is any way to beg, borrow, or steal a pair of the 170mm drivers used in the ATC SCM40 speakers. I think that this might well do the trick. I need to keep the speakers as narrow as possible to improve the spousal factor or I would try to use an 8" or 9" bass driver.

Thanks again,
John

[Tenson]

Take a serious look at the Hi-Vi D8.8+, it would do very nicely as a bass driver with an xover anywhere up to as high as 1.5KHz. Its a very, very good driver but with an affordable price tag

I also feel that both the tweeter and the midrange you mention are over-priced for the performance on offer. I would likely go for either the Vifa XT25 or more likely the recently announced Peerless 810921 which looks absolute irreproachable for the money, having performance on par with the best there is.

As for midrange I guess there is not a huge choice. The ATC is good, but is pricey. Volt do a midrange unit but its not on their site. PMC actaulyl use this with some slight mods in their big boys speakers Give Volt and email.

[vincentrubble]

ATC's 180mm bass driver is not for sale. They want to keep it for themselves. According to Solen, the Morel HU631 is not up to the quality of the SS R2904/7000 and ATC SM75-150S. Solen is recommending an Audio Technology custom built driver. This sounds like a pretty cool way for the hobbiests to pretend they are speaker manufacturers. You select your driver size, magnet size, voice coil diameter, coil height, gap height, desired fs, Qts, Vas & Qmin and 'voila!' they build you a driver. See http://www.audiotechnology.dk/iz.asp?id=4|a|119||| for more info. It turns out these guys started Scan-Speak & Vifa, among others. I am just starting out in the custom order process but I'm excited to see how it works. Solen has been very helpful with various questions I have had regarding desired parameters, etc. This is usually a process reserved for manufacturers.

Thanks,
John