Madison Speaker Works/Madisound.Parts-express usually offers good advice.Give it a try.
Zymaze, these passives went through a number of design changes. If the passives are missing I'm going to guess they were the older white ones with foam-like surrounds; these will have deteriorated over time. The current ones are black with hybrid rubber surrounds. I'd be really surprised if you could get these as "pulls", as Shahinian uses screws and a resin type bonding compound to affix them to the cabinet. I can't see how a pull could be made without ripping it apart around the surround.
Having said that, if you can find legitimate pulls in good condition then go for it - but I think that's unlikely. The passives Shahinian uses come from somewhere in Europe, and they are expensive to begin with, but with the weakened dollar more so still. I know it's not cheap, but unless you are confident in finding a set of replacements you might be better off just having to get them directly from Shahinian. There's a good chance going another way you could wind up with something that will change the transmission line loading.
The Obelisks are too good to do something like that to! :-)
Mr Z: The size and weight of a passive radiator is determined through a formula based on the Theil/Small parameters of the woofer and the volume of the enclosure. There are other factors involved, but basically the radiator takes the place of the mass of air in the tuned port of a vented box. It's clitical to get the correct ones for the design, IF you want the designer's intended bass response.
Thanks for your many responses. I understand and appreciate the purest perspective. I really have no idea what the speaker are worth so my query arose from a practical perspective aimed at bring the speakers up to snuff at minimal cost.
Please excuse my ignorance but there is very little information available on this company or its speakers. I would not ask for your valuable time if there were numerous of reviews and test results I could study. Most reviews are from the last few years and address the current models which have evolved much since my speakers were made.
I was not sure(and I am still not sure) if the PR was just a plastic cap or a drone speaker with a cap. I did not see any screw holes in the opening and I thought it might just be a cap that was glued in place.
Are there PR's that are just caps? On eBay I saw this: http://cgi.ebay.com/10-Passive-Radiators-PR-Speaker-Radiator-ESS-P-10PK_W0QQitemZ190092820392QQihZ009QQcategoryZ14993QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
Is that a PR that is simply a cap?
I have read that newer Obelisk's have weighted done speakers but I was not sure that was the case with much earlier versions.
I can understand special imported weighted PR's with installation kit costing $275. But, I have trouble imagining plastic caps jutifying that price. Especially if they sell on eBay for $35. I have emailed Shahinian Acoustics but I wanted this group's opinions first since my experience has been that if you ask a company if you should use their products they will invariably say yes.
And if you read my post I never complained, I am just trying to make an informed decision.
Lastly, does anybody know how the grill cover and pyramid on these speakers are best removed for inspection of the drivers?
As others have stated or implied, you got one heck of a deal on this speaker. If I were you, I would get a quote from Richard and Vasken Shahinian to bring your speakers up to date all around. Yes, it may be several hundreds of dollars with shipping but at the end of the day, you will have something worth much more. I mean this in instant gratification of a sound signature as well as investment for a future re-sale. Food for thought...you will find others who would be willing to purchase them as is if you are resonable and realistic in your asking price.
Zymaze, now that you've gotten a number of responses I will be more direct - everyone here is exactly on target. If the woofer and top drivers are in good shape (even if the woofers need replacing!) you've gotten maybe the deal of the century. Don't email, don't mail - CALL Shahinian Acoustics early to mid-afternoon tomorrow (that's when Dick and Vasken are usually in the shop together) and either get new passives or send the speakers back for total reconditioning. The cost will be significantly less than a pair of mint used Obelisks and you will have one of the most unique and killer speakers ever designed.
As an owner of Shahanian Obelisks for 20+ years, I can only add my voice to what Tonyptony and others have so eloquently said. These are killer speakers. Please, please contact Shahanian and invest the necessary money to bring these incredible speakers up to spec. You may well enjoy yours for 20+ years...that would amortize to less than $20 per year!