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Infinity Qb Transformation

Thumbs up! How much of a difference in sound between original and updated version? Did the caps make a big difference? If you were to do it again, what would you do differently? And...did the inner cabinet stiffening and lining make a difference?

I may have to dig my pair out of the closet and put them back into rotation. The Qb's sound good. I really need to audition some of Infinity's top tier speakers!

Again...Good job!!!
 
elnaldo said:
Nice !! You did what all we Qb owners want to do some day :)

Please post listening impressions, and if you would do it again...

BTW, what is that small brown resistor I see on your crossover? My Qb have just 1 resistor:

Original:
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/6_P1060617.jpg


After recap (tweeter by-pass not in the pict, but added later):
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/8_P1060623.jpg
Click to expand...

It is. The crossover described in the technical manual lists a
5 ohm/5 w tweeter level control.
http://www.bobbyshred.com/images/Qb_Tech_Sheet.pdf
I inserted the resistor. After a lot of critical listening, I think the speakers sound too reserved. I'm going to remove this resistor.
Thanks for the head's up!
Mike
 
Kahoona said:
Whoa!! Those are some really fine speakers and you are pulling out all of the stops to get the max out of them! I am intriguer by the slurry. What are you mixing the sand into and what proportion? I have never seen this. Does it reduce reflection also or is it primarily to reduce vibration? Will it replace bracing? I cannot wait to hear about the results. The tweeter is the star of the show IMHO but that mid is some serious stuff too. Thanks for sharing this.
ROb
Click to expand...

Is this a secret slurry or can you share your methods with us. I see it's play sand and some kind of paint????
 
Idea; how about opening the tweet recess on the inboard side to allow it to shift away from the veneer? You may have to fill a couple of screw holes but it would look better IMO.

Nice parts selection in that Xo.
 
Pretty sure you can swap the round face plate on the EMIT with the original square face plate. Then you don't have to worry about routing out the grill.
 
I'm almost done!
IMG_2665-XL.jpg

Here are the photos of the grill assembly:
IMG_2669-XL.jpg


IMG_2671-XL.jpg


IMG_2673-X2.jpg


IMG_2677-X2.jpg


IMG_2678-X2.jpg


I just have to remove the resistor in the tweeter circuit, and they'll be all done. Three weeks until the 2014 THE Show.
They'll be hooked up to a really cool and dead quiet Luminous Audio Axiom II Passive pre-amp with the Walker Modifications
http://luminousaudio.com/axiom2/walker.html
and a Marantz 8b modified by George Kaye of Moscode Amps in NY.
If you are in Vegas for CES Jan 7-10th, stop by our NFS Audio Room 4001 at the Flamingo during the THE Show.
We'll have some other speakers to play with as well, including a pair of Fritz speakers and a modded pair of Sunfire CRM-2's.
Cheers!
Mike
 
There are a number of inquiries about the infamous deadenig slurry. I buy a cheap can of paint and mix enough sand to make a thick muddy paste. This is smeared onto all the inside panels and dried completely. Make sure you put some masking tape on the inside edge of the crossover opening. This way you will have a surface free on the compound in order in order to attach the crossover plate. I have no recipe, I just mix it 'till I think it's right.
I cook this way as well...drives the wife nuts ;)
Mike
 
I took the resistor out of the tweeter circuit.
Gadzooks!
These old dogs sound great!
All of you Qb owners, I think it is absolutely worth the time and $$ upgrading these speakers with 21st century crossover components and cabinet treatment.
:banana::banana::banana::banana::banana::banana:
Mike
 
Very nice!
Some 1X2s glued up between the front and back baffles , under the woofer screw holes, really did wonders for lower mid bass.
 
I am glad to see someone asssign importance to treating the cabinet. Thank you! Damping a resonance here and a vibration there really does make a difference in the end. I have used a similar 'goop', ReptiSand embedded in two-part epoxy. It does great on the back of driver frames, especially in recessed spaces that are just "made" for holding damping goop, like the back of a lot of tweeter faceplates. Another good one is sand in resin (like fiberglass resin that hardens via a catalyst). These are probably a bit trickier to work with than your solution, though. Have you ever tried Cascade VB-1X? It's not the cheapest stuff but seems to work well. The interiors of my RS-IIIa's are lined with it.

Very enjoyable read, sir!!

G~

Edit: If I may make one observation on the solder joint to the foil inductor....
It looks like you have folded or pinched the foil around the lead wire going to the caps, and then soldered that. Specifically, I'm looking at the last two photos in post #18. One technique that I think works quite well for foil inductors is this: poke a hole through the foil near the end using a pick or drill it with a small bit. Form a j-hook with the next wire, just like the ones you did on the leads going to the laminated steel inductor. Run the j-hook through the hole in the layers of foil, and then pinch it very tight with needle-nose pliers. Make it tight enough so metal-to-metal contact is gas-tight. This is the primary electrical contact area, and then soldering into the joint between the wire and the foil is 'icing on the cake' to make it that much tougher. Just a thought for the future...
 
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geoff727 said:
I am glad to see someone asssign importance to treating the cabinet. Thank you! Damping a resonance here and a vibration there really does make a difference in the end. I have used a similar 'goop', ReptiSand embedded in two-part epoxy. It does great on the back of driver frames, especially in recessed spaces that are just "made" for holding damping goop, like the back of a lot of tweeter faceplates. Another good one is sand in resin (like fiberglass resin that hardens via a catalyst). These are probably a bit trickier to work with than your solution, though. Have you ever tried Cascade VB-1X? It's not the cheapest stuff but seems to work well. The interiors of my RS-IIIa's are lined with it.

Very enjoyable read, sir!!

G~

Edit: If I may make one observation on the solder joint to the foil inductor....
It looks like you have folded or pinched the foil around the lead wire going to the caps, and then soldered that. Specifically, I'm looking at the last two photos in post #18. One technique that I think works quite well for foil inductors is this: poke a hole through the foil near the end using a pick or drill it with a small bit. Form a j-hook with the next wire, just like the ones you did on the leads going to the laminated steel inductor. Run the j-hook through the hole in the layers of foil, and then pinch it very tight with needle-nose pliers. Make it tight enough so metal-to-metal contact is gas-tight. This is the primary electrical contact area, and then soldering into the joint between the wire and the foil is 'icing on the cake' to make it that much tougher. Just a thought for the future...
Click to expand...

Thanks for the advice on the foil inductors. If I find anothe set of Infinity's for the 2015 THE Show, I will certainly use your technique.
I am really enjoying the sound of these speakers. I have to hook up another pair of speaker wires to the Yamaha CR3020 so I can do a side by side comparison to the WTLC's I re-built last year.
M
 
Hello Mike,

Very nice job on the Qb. I have an early model of Qa wich I love very much.
The speakers in good shape except I missing the stands for them.
I only had one capacitor per speakers so it was an easy upgrade. (Claritycap ESA)
I liked to make the stands myself but could not find any detail about there size.
I have seen your photos and I can get some rough estimate on there size and shape, but I like to inquire some proper messurments.
So I could make mine as close as possible to the original.

I appriciate any help I get.
Thanks
B
 
Here I have the drawing I've used to rebuild mine:
http://dl.dropboxusercontent.com/u/1640933/infinity/pie_Qb.pdf

All measurements in centimemeter. Round to standard values, small differences come from the innaccurate CAD drawing.

The 1.2 cm dent should match the gap at the back of your cabinet.

Material thickness is 6mm .

I hope this will help other people too.

Here are some pictures:
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/P1070002.JPG
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/pie_P1070003.JPG
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/pie_P1070005.JPG
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/stand_P1070030.JPG
https://dl.dropboxusercontent.com/u/1640933/infinity/bafles/nuevos/stand_P1070042.JPG

What's the capacitor size on yours? 9.5uF?
 
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Here I have the drawing I've used to rebuild mine:
https://dl.dropboxusercontent.com/u/1640933/infinity/pie_Qb.pdf

All measurements in centimemeter. Round to standard values, small differences come from the innaccurate CAD drawing.

The 1.2 cm dent should match the gap at the back of your cabinet.

Material thickness is 6mm .
Click to expand...




Do you have a native CAD file to download? I use Solidworks and I may model this in 3D and have a pair made
 
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