Infinity Qb Help?

[rebelliondog]

I have always been a fan of Infinity speakers and have recently acquired a pair of Qb's.....I am attaching some pictures. They are very good cosmetically, but I believe will need some help with one of the EMIT tweeters.


Ideas (other than eb*y) for finding replacements? I found some on the bay used but not sure of the quality.

The model numbers are as follows:
Diaphragm #751-3722
EMIT Tweeter #902-0221

I will keep these for myself (planning to)....so if anyone has suggestions on an 'upgrade' that they have done on some of these, feel free to let me know what that is as well.

Thanks in advance for your time.

 

[slimpikkins]

You could try fixing them with rear window defogger repair to retrace the broken traces. This can be found at auto parts stores.. There's a thread or two which cover this. Looks like you have the diaphragm out... I've done it and it works but will raise the impedance a bit. For replacement eBay is your best bet.

 

[goodolpg]

On ebay, use the zoom feature to check the flatness of the diaphragms as well as look for lifted traces and general condition of the faceplates. JMO---those chrome faceplates almost always look a bit yucky, maybe it's just me.
I really really really prefer when the seller shows each EMIT hooked to a digital multi meter and the reading is between 3.0 -3.6 ohms, most good EMITs seem to read in the center of that range.
Failing pictures with meter, a seller that says they measure 3.XX ohms is almost as good as pictures, but not quite.
And then check the sellers feedback anything under 99% (and some say anything under 100%) unless a huge number of sales is not that great.
Check their feedback for hints about their packing skills.
Have they sold lots of audio gear or is this a one time deal, if one time it MIGHT be a clueless seller.

 

[swechsler]

IME most EMITs of this age will show some delamination. We're talking about 40 year old drivers here. You can probably substitute newer ones (i.e. the type with round faceplates) with no or minimal difference in sound quality. For upgrades,I'd start by replacing the capacitors in the crossover. Also some internal bracing might be in order (IIRC these have none). I'd probably also replace the wire clips with decent binding posts - these are probably somewhat corroded and even if not, if you're going to be fixing up the crossover anyway, it's a cheap mod. But these are great speakers on their own, so I wouldn't go replacing drivers other than the EMITs; you're more likely to make them worse than better.

 

[rebelliondog]

Thanks. I went ahead and made an offer to the seller(accepted) stating that the EMITs had been removed and working well from some infinity Qe's (same tweeter). Hope it works out well for me.

This means I have......A spare, working EMIT as well as one to work on to see if I am able to recondition it.

I will update this thread as I progress over the next week or so.

 

[goodolpg]

I hope it works out just fine for you, it should.
Lots of folks like the Qb's.
Hopefully you will too.
Got to hand it to you...you dove right into that EMIT...took me 34+ years from my first Infinity purchase until I tore an EMIT apart.

I've bought several pairs of EMITs on ebay using the method I mentioned.
All were working as advertised.

 

[rebelliondog]

I have been taking things apart most of my life and can usually (?) get them back together.....sometimes(?) functioning properly. The
EMITs were $75....speakers were only $20....I am still feeling ahead of this game.
I'll start looking into the internals tomorrow.

 

[Spitfirejoe]

Use ONE amp fuses, not 1.25 amps. They should be "quick blow" types, not the slow blow I prefer in my British cars. You can find them, you just have to look. I think 1.25 amp fuses are just enough to result in the kind of damage you saw in that emit. Odd that a quarter amp of power can do that...

 

[rebelliondog]

But it says the warranty is voided by use of anything other than 1 1/4 amp fuse.........where would I go for repairs if necessary??

 

[goodolpg]

But it says the warranty is voided by use of anything other than 1 1/4 amp fuse.........where would I go for repairs if necessary??

Back in time to around 1982 (Infinity had 5 year warranty?)

Shirley you are joking.
Many Infinity owners are using 1 amp fuses.

 

[rebelliondog]

I sometimes think that the warnings manufacturers place on items are funny....wouldn't 1 amp have been safer, even in 1982. Why should that void the entire warranty? Anyway.....

I bought 1.25 while I was out......may rethink that.

Thanks for the input / warning.

EBay EMITs came today....paint is done, resealing is drying....bad weather on its way to the Texas coast. That'll give me few days inside to work on them.

 

[goodolpg]

If you are in Harveys sights, stay safe, stay dry.

 

[rebelliondog]

With the rain here in the Houston area (I am in Pasadena TX)......I had time for my newest project.

The sound is unbelievable for the size and seeming simplicity of these speakers.....just a 3 way average size speaker......wow.
I took most (some) of the advice I read in this forum.

After I cleaned up and painted the speaker baffle and the back....

I resealed the cabinet.

I braced the cabinet on the inside....used some MDF scrap pieces, roughly 1"x1". I think it worked well.

I changed the capacitor...nothing fancy for now, just local pickup close to home. (Improvement over what was in there?....probably.)

I did not get a 1 amp fuse (as was recommended)....still the voided warranty issue I didn't want to risk.

I decide to add some speaker terminals (I think banana plugs are very convenient for rotating speakers). I did this by just soldering wires onto the crossover. Now the spring clips are still there, in addition the much more user friendly terminals I installed. Use either one you want....just not both.

 

[rebelliondog]

End Result....now I guess I turned this into:
'Another Infinity Qb rebuild thread'....
Thanks for everyone's help.

 

[Spitfirejoe]

A fuse of lower rating provides MORE protection to the tweeter. I don't think there is any way it could make damaging an EMIT easier to accomplish. But - that said - a 1.25 amp fuse should be fine. Just don't ever put a larger value in there.

Nice work on the rest of the refurb! I especially like the additional speaker terminals you added. That worked out well, and shouldn't change anything adversely, I would think.

Did you clean and lube the potentiometer? Caig branded DeOxit and Fader Lube is what I used. You can find threads describing the use of these products on AK.

 

[merlynski]

Definitely go with the lower current fuse, I toasted a number of diaphragms without blowing the fuse.
Also note that Qbs are 4 ohm speakers. I have a pair I bought new in the early '80s and didn't know it. Probably why I fried the tweeters .

Qb Parts pop up in Bartertown occasionally also.

 

[rebelliondog]

Well, for today there has been some flooding and some wind (I'm just northeast of Harvey's landfall).....so, the 1a fuse will have to wait.

My receiver, HK3480 should handle the 4 ohms without issue....it is rated 120@8, 150@4.

Funny thing with the dual (either/or) inputs.....I once sold a dual subwoofer box to someone, it worked great. I had installed terminals on both sides of the box.....convenience for placement.....for an 'either/or' situation and had explained that to the purchaser. However, rather than bridging his 2 channels to make one and then using just one terminal on the subwoofer box......he did a left/right scenario.....then called me asking why that did not work. Then, why his amp would not work.