Infinity Quantum 2 - High Impedance Readings

I'm not following the numbers in that chart - the % is obviously a +/- error range but what is the "+3" etc. after each percentage?

There is very little that can go wrong with inductors. Meltdown from overheating is about the only failure mode, and you'd have other damage in the speaker. If two identical inductors from the two crossovers measure the same resistance, they're most likely not shorted internally, since it would be a miracle for both to melt down in exactly the same way. And if they measure the same inductance (even it appears 'wrong'), I'd move on, because it's most likely the meter.

I still maintain that capacitance and inductance do not truly vary with frequency. Otherwise you couldn't sell a 1 mH inductor without specifying the frequency at which it is 1 mH, and similar for capacitors.
 
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I have been looking at these Erse and also the toroidal ones from Jantzen which have lower resistance. If I remember correctly the infinity "20 mh" coil measured a DC resistance of about .15 ohms. The Erse has a DCR of almost .6 ohms, that is problematic since the woofer voice coil is only 2 ohms. Too much power will be lost to the Erse coil. The largest Jantzen they have is 18 mh and has a DCR of .174 ohms. Not bad but still need 2 mh more... That 18 mh Jantzen coil costs $77/each and I would want to fix the 6.5 mh and the 5 mh on the mid bass also in both speakers.

So what I am leaning on doing is opening up the speakers again and measuring the values of the existing 3 coils for bass/mid bass and adding in series the amount I need to get the right value. I probably need about 5 mh to get 20 mh, 2 mh to get 6.5 mh and 2 mh to get to 5 mh, in each speaker. I would use the 14 ga. Jantzen types to get the lower DCR. It won't cost as much since I will be adding small values.

After experimenting with the driver level controls, it's becoming clear that the woofer IS rolling off too high. This is consistent with the coils being too small. I found that I need to turn the level close to minimum on the mid bass to get a somewhat smooth transition from the woofer because the woofer is producing too much mid bass. Since I need to keep the mid bass low, I also need to keep the mid and tweeter levels low to match. Also, the woofer 2 ohm coil is crossing to high and producing sound that should only go to the woofer 4 ohm voice coil. If this theory turns out to be true, I will have a perfect set of QLS-1's!
 
I'm only using my ears. Maybe I could find an app for my phone or laptop that can help me measure frequency response.
 
Vinny, your plan sounds good. But I wouldn’t overly fret about the DCR of the Infinity parts. They may measure 0.15 (that seem low to me for such a big inductor), but they aren’t 20mH. If they were, they’d have a higher DCR.
 
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I have a pair of QLS-1 I restored so I know a few common problems and their solutions.

1. The EMITs become high impedance and therefore quieter. You must re-melt the "soldier buttons" on the diaphragms. You'll need a pair of 6/32 1 1/2" machine screws to safely disassemble the tweeters. Take out two of the pan head machine screws at diagonal corners from each other, and thread in the 1 1/2" screws in their place. Now remove the four remaining pan head screws and the hex head wood screws that mount the tweeter to the cabinet. CAREFULLY separate the two halves of the tweeter to expose the plastic diaphragm with the little metal "racetrack" on it. Find the two little "soldier buttons" on the back of the diaphragm where the race track connects to the speaker wire. Test them for resistance, they should be about 4.7 - 5.2 ohms, if they are higher they need their soldier buttons reflowed (if they are "open" the racetrack might be broken, which might be fixed with an automotive window defroster repair kit.) Using a very well tinned, low power (15-23 watts), iron with a fresh tip, Just touch the buttons until they give, then IMMEDIATELY remove the iron. Check for resistance and repeat if necessary. When an acceptable resistance is achieved, use the 1 1/2" screws to reassemble the the tweeters, be sure to get all the spacers and other parts back in the right way, and be careful of those super powerful magnets! The long screws hold the parts in place while you close the two halves and re assemble the tweeters. This really helped my speakers to image.

2. The pots in the crossover are known to get very corroded, this can make to drivers sound muffled or cut out completely. They are pretty easy to clean however. Take out the Watkins Woofers, this is a good time to test the woofers too, should be about 4-5 ohms on voice coil 1 (red wire) and 2-3 ohms on vc2 (black). Then draw or photograph the crossover for easy reassembly. Unsoldier (desoldier?) the wires from the pots and remove the control knob and mounting nut. The pot will come right out, it is held together with a bale, by flipping the bale wires to the side, you can open the pot. Clean it out with some DeOxit D5 or the like and a soft toothbrush. Don't use rough sandpaper of anything that might scratch the wires, this will just promote more corrosion, if it's really crusty, try a small brass wire brush. Reverse the procedure to reassemble.

3. Electrolytic caps have a finite life span because the electrolyte drys out. Replace any black and red caps you find in there, they are DONE, every single one in my speakers was leaking crust!. Big caps, like soda/juice can size, last a long time, the yellow oval caps are film caps which have a very long life, they are part of the "Infinity Sound"; leave them alone.

4. Check for air leaks. I had a bad one around one of the mid-bass couplers. It would make a weird noise when the speaker played a certain frequency.

I hope this is clear enough to follow, if not please reply with questions or comments. These are such nice speakers and everyone here at the Infinity forum wants to see you bring them back to their former glory!

RIP Arnie Nudell

I have a pair of Q2's that I purchased a year or so ago and have really enjoyed them. The seller had told me that he had gone through all the speakers, rebuilt the crossovers including replacing caps and pots. My impressions have been that they sounded very good if not power hungry and can be driven by either my Counterpoint NPS-400A MkII or a relatively newly acquired Odyssey Kismet Reference. I was dinking around checking resistance across other speakers in my collection and measured about 3 ohms across a some Alon II's and 10 ohms across my Avantgarde Duo Grosso's but when I checked the Infinities the readings were 5.8 M ohm on each. So I checked fuses, they are good but interestingly when removed have no effect on readings. If I assume the pots are good, does this imply problems with the EMiTs as you describe above? Any other thoughts?

Thanks,
Brock
 
I have a pair of Q2's that I purchased a year or so ago and have really enjoyed them. The seller had told me that he had gone through all the speakers, rebuilt the crossovers including replacing caps and pots... when I checked the Infinities the readings were 5.8 M ohm on each. So I checked fuses, they are good but interestingly when removed have no effect on readings. If I assume the pots are good, does this imply problems with the EMiTs as you describe above? Any other thoughts?

Thanks,
Brock
The Q2s don’t have any DC connected paths in the crossover. Every branch contains a capacitor, so your measurement is probably fine.
 
Thanks pauljh....I didn't realize the caps isolated the inputs. Much appreciated as the speakers sounded just fine...

...except for an annoying sympathetic buzzing that occasionally shows up with low frequency bass. It comes from the plastic mounting plate for the input terminals, pots etc. I have even noted that the plastic plug to switch the tweeter crossover frequency from low to high will buzz a bit. Are there any recommendations for damping that area?

Thanks again,
Brock
 
There’s nothing magic about tracking down unwanted vibrations. Get some sort of source where you can sweep sine-wave frequencies (there are a lot of choices on smartphones), a screw driver, and some silicon rubber caulk, then have at it.
 
Then cheap iron core coils can suffer from corrosion, 2 of mine were...I went with laminated steel to replace them...

parts express can make custom windings to meet your requirements
 
It'd be nice if you were to provide us pics of your progress.
Many Infinity crossovers showed different parts and arraigned in varying ways and condition.
Those black caps are bad.
How to tell if the black (and for that matter, the big silver and blue) caps are bad?
 
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