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ribbon tweeters in infinity QBBigsound
May 7, 2001 9:59 PM
Ok well my dumbass brother fried the ribbon tweeters in my dads vintage infinity QB speakers. So now we gotta replace em. What do u reccomend or where can i find replacements for these speakers? We want them to match the speakers as much as the originals were.
Infinity Qb'sBeatleFred
May 7, 2001 10:43 PM
Hey! I have a pair of Qb's also and I like 'em - ALOT!! Have you seen the site: www.bobbyshred.com/infinity.html which is dedicated to the great Infinity model speakers from the late 70's?

As for your fried EMIT (electromagnetic induction) tweeters: Call Infinity (now owned by Harmon Kardon and nothing like the great company they once were) at: 1 800 553 3332. You need to order Part#: 751-3722 which is the tweeter diaphragm- the etched conductor membrane "sort of thingy" that got scorched. You dont need the whole EMIT assembly itself. Order two of those from the Parts Dept- they are about $40 ea. If you like the Qb's as much as I do and think you might like to have them for a while to come in the future (and preventive precaution for your dumbass bro)- then order another pair of them as backups- before Infinity (HK) stops making them and they are permanently out of stock. Ive called Infinity before myself- unfortunately its a bit of a wait on hold before a human finally answers- but what can 'Ya do? The thing to keep in mind is its a bit cumbersome to replace the EMIT diaphragm - the magnetic force of the speaker itself opposes it as you'll see if you attempt to do it yourself, but with a little effort it can be done and youre back in business. Out of curiosity: How did the Bro fry the tweeters? What amp or receiver do you have connected to the Qb's? How is the condition of the other drivers? Are the woofers and midranges' still the originals?
I also recently bought a pair of Infinity Renaissance 90's (1991-1995) which are fantastic loudspeakers- see owner reviews on them on this site. But even so, I still liked the Qb's enough to keep them as my 2nd speakers- whereas a few others models I had were sold or traded away.
Infinity Qb'sBigsound
May 8, 2001 7:26 PM
I as well really like the sound of my QB's. Is it alot of work to rebuild the tweeters as u described? These speakers are downstairs in our house in the basement/wreckroom kinda place. There still powered by teh same amp that my dad bought at the same time as when he bought the speakers. Its a Scott 480A. It pushes about 85 Watts to each speaker at 8Ohms. But according to that webpage you posted the QB's are 4 ohms. So i guess there gettin around 170 watts? What blew the tweeters was my bro playing a 20KHz test tone at a very high volume. Dont worry.. i kicked his ass for doing so. At the same time as replaceing the tweeters i may replace teh woofers as well. The tinsle wire on on of them is starting to get frazzled and the woofer occasionally shorts out. Its only one woofer but i think it would be better to replace both of them while im at it and also would keep them balanced. Do you have any idea of what these woofers are worth? The mids are still perfectely fine.
Infinity Qb'sBeatleFred
May 8, 2001 10:48 PM
The difficulty with the tweeter is trying to put the new diaphragm in there - the magnetic force is very strong. The Scott sounds OK but I dont know if it can double its power output as the impedance halves (from 8 to 4 ohms). Not all amps can. ** By the way- about those fried EMIT's: did you check the glass fuse in the back of the Qb's? A loud 20Khz tone can blow the fuse which would cause a loss in sound. Check the fuse first. Also, the adjustment knob in the back is prone to getting dirty which can cause a loss or cutting in/out of the sound- a little cleaning spray on them is a good thing to do. Repairing audio gear is not my strongpoint but I'd say having your woofers checked out would be a good idea. Maybe its just some loose wires there or something. Infinity sells 10" woofers for the Qb's (Part# 902-2864) but they are generic substitutes- made of foam - not the original butyl rubber which I prefer. And the inferior foam's go for over $100 from Infinity(HK)- Ouch!! I did see an auction on Ebay recently for a pair of woofers for Infinity Qa's- they are the same as the Qb's except its 2 way- doesnt have a midrange. The 10" woofer is common to both models though. Check Ebay to see if they are still available or the Completed Auctions section to see if anyone bid on them.
Infinity Qb'sMark S
May 10, 2001 12:42 AM
I just picked up a pair of Infinity RS3b speakers (apparently built in 1980.)at a yard sale. Are these any good of a model?? 'They are gorgeous to look at. How much power do they need. I don't have an amp yet but want to buy one that is suited for it. Are these inefficient or efficient speakers??? I am not an audiophile but aspire to be one someday, money permitting. By the way they look, I think they must have been a big deal when they came out..Help anyone???
 


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