Another Qb Refurb Job

Hmmmm... not sure I follow. The woofer and mids are not recessed into the front baffle, so no need to route those edges. However, the inset hole for the tweeter would make it impossible to use the same spot. You'd end up with a hole through the baffle behind the tweeter - creating a big air leak and not through a "tuned port". Does that make sense, or am I missing something?

Minor update - that first speaker is back together, and looks pretty good. There is some damage to the vinyl covering on the outside edges, but I used a touch up "crayon" type thing to fill some of the gaps and the damage I caused is pretty well hidden now. You can see it if you look for it, but I think I can live with it. If not, I'll peel it all off, sand the cabinets down and paint them or try a wood veneer. The second crossover has been updated. I'm now running a bead of wood glue around all the joints inside the cabinet. A few of the seams looked to have no sealant at all. I bet they were glued in the "tongue and groove" area, but I didn't see any evidence. I think the wood glue is going to seal these cabinets up nicely. I still have to cut and install the wood dowel brace behind the woofer, and will repaint the front baffle to match the first one. Can't wait to hear the finished result.
 
Gotcha. I thought the tweeter hole went clear through the baffle. Your repair/filling of the old hole looks great. Great project!
 
My "new" baffles had a "real" hole for the tweeter (even if I brought the original box as a model, and the guy who did them had a CNC machine, he did a hole instead of routing just some mm). So I've ended gluing a piece of MDF from the back, to seal the tweeter hole.

The woofer and mid are not recessed, but they are actually off-centered. The idea of using the same baffle is a good idea, but I think it's easier just to cut a new one, and remove the old one with a router to save the box edges.

The front edge is not visible with the grill cloth on, so I wouldn't worry not even a little. My edges are a DISASTER, very bad looking, very unpolite work, but I never realize about them , I didn't see them in years.
 
Spitfirejoe said:
Here's how they are listed: Sure Electronics AA-AA11151 Mini Gold Plated Insulated 5-Way Binding Post Set 2 Red 2 Black. Part Number is 320-3375. Model Number is AA-AA11151

I like these because they give me three options - twisted bare wire through a hole in the post, the U shaped spade lugs, or banana jacks. I've never used banana jacks, but am thinking about trying them.

I had to drill out the main hole just a bit bigger and then the jack slipped right in place. I used some black silicone RTV sealant to seal up the other two small "slits" below the main hole.
Click to expand...

The BFA style banana plugs are awesome. Short of bare wire, the BFA style bananas make the most secure connection. They also have a serious amount of surface contact, are very secure due to the spring/sprung presure, and generally won't fall out, or get pulled out easily like spades or those spring type bananas. I highly recommend the inexpensive crimp-on style, but don't just crimp them. Crimp them and solder, or just clip off the crimp tab and solder.

I first was exposed to the BFA style bananas on a pair of Nordost speaker cables. Later I found a source for the banana plugs and started making my own speaker cables. They are readily available these days on eBay or other places.
 
I don't know why I didn't finish this thread with a listening report. Another AK'er was asking about Qb's and it brought me back to this thread.
They sound great again - beautifully smooth mid range with that effortless and crystalline high end that I always liked. They may lack a little in the lower register compared with larger speakers, but I filled out that range with a BU-120 sub-woofer. Acoustic guitar and male voices are again sounding fantastic, and good female vocals are amazing. David Crosby, James Taylor, Norah Jones and Alison Krauss are right there in the room. I think the replacement capacitor really helped and other work to the crossover (cleaned pots, re-soldered connections, banana plug connectors instead of the spring clips) certainly didn't hurt. I did add some more fiberfill, as well.
I think the upgrade to a more powerful receiver has also been helpful - still using a Pioneer multi-channel AVR, but I went from an older VSX-D606 to an SC-1222-K with Class D amplification. The learning curve on using the new receiver has been tougher than I thought it would be - too many features and I play with settings too often.
I don't think moving the EMIT tweeter made any difference at all, but I'm running them in a still unfinished basement area. It's possible that a better environment would be more revealing. I also didn't move the location of the woofer and midrange, and they are slightly offset in the baffle. It's possible that moving those to make the speaker a true mirror image would have made a difference, but I rather doubt I'd hear a difference.
I should move them to a more photogenic area of the house and take some photos...
 
I received a question by PM about the capacitors I used in refurbing the crossovers for my Qb speakers, so I thought I would throw that information into this thread for posterity. Everything is still holding up quite well, and I'm still pleased with the results. Information on the parts is below...

Joe


Here's what I ordered for that Qb job. Everything was from Parts Express. Prices could have changed by now, but the part numbers should be the same.

I couldn't find a 12.5 uf capacitor, so I used a 10, a 1.5, and a 1.0. That adds up to 12.5 uf, so works out to function the same. I just twisted the leads for all three caps together and soldered them. I ended up not using the 6.8 uf caps I ordered because I was assured by more knowledgeable members that the yellow 6.8 caps don't deteriorate and can be important to "The Infinity Sound".

Dayton Audio PMPC-6.8 6.8uF 250V Precision Audio Capacitor
Part # 027-238.
2 @ $5.19 = $10.38

Dayton Audio PMPC-1.5 1.5uF 250V Precision Audio Capacitor
Part # 027-212.
2 @ $2.24 = $4.48

Dayton Audio PMPC-10 10uF 250V Precision Audio Capacitor
Part # 027-244.
2 @ $7.65 = $15.30

Dayton Audio PMPC-1.0 1.0uF 250V Precision Audio Capacitor
Part # 027-210.
2 @ $2.03 = $4.06

Sure Electronics AA-AA11151 Mini Gold Plated Insulated 5-Way Binding Post Set 2 Red 2 Black
Part # 320-3375
1 @ $9.26 = $9.26

Acousta-Stuf Polyfill Speaker Cabinet Sound Damping Material 1 lb. Bag
Part # 260-317
1 @ $8.95 = $8.95
 
Fantastic info here. It's write ups like this that gives me confidence to chase a pair of Qb s. I recently picked up some Qe s and the emits are the special sauce - so I'm looking for something larger on a tight wife approved budget.
 
Thanks everyone for a great Qb thread. Mine were supposedly reworked a few years ago (recent purchase) but I'm sure I will open them up some day. When that day comes a resource like this is invaluable.
 
I'm going to do a vinyl delete on them.. change the surface on the outside, thin layer of color perhaps or illustrations.

I'm thinking of routing a design in to them - like tooled leather, think future primitive. we will have to see how dense the particle board is.
 
It is not too compact. Feels cheap. But perhaps the surface is sealed and smooth enough to adhere some vinyl or glue some paper on it.

I'd re-veneer them with real wood veneer.
 
chef free said:
I had that exact same rattle and it motivated me to open my Qb's up for the first time too!

Here's my advise:
Do not change out the yellow film caps, they are part of the Infinity sound.

Clean the pots thoroughly with some DeOxit and lube them with FaderLube.

I added about 30% more stuffing to tame their 100Hz "thump", you might want to play around with that.
Click to expand...
I am working on a set of RSb's and the large yellow capacitor in these crossovers show a value of 3.5 uf. I was able to borrow a quite accurate meter and measure the capacitance and ESR. They measured @ 3.56 and 3.57 which is almost exactly matching. I can't remember the ESR but it was like 0.1 ohms. So these are good capacitors that appear to hold up well. I did replace mine with Jantzen Audio 800V Z-Superior Capacitors. Haven't finished the project or listened to them yet, but If I had the measurements before rebuilding the xovers, I would have left the original yellow 3.5 uf caps in. If they don't sound right after some burn in, I can always put the 3.5 caps back or try bypassing with some 0.01uf glass encased paper in oils that i have. So more than likely, these caps in similar vintage speakers can be left in without any worries. The electrolytics were all 25-35% off and the ESR's were all shot as well.
 
Spitfirejoe said:
Here's how they are listed: Sure Electronics AA-AA11151 Mini Gold Plated Insulated 5-Way Binding Post Set 2 Red 2 Black. Part Number is 320-3375. Model Number is AA-AA11151

I like these because they give me three options - twisted bare wire through a hole in the post, the U shaped spade lugs, or banana jacks. I've never used banana jacks, but am thinking about trying them.

I had to drill out the main hole just a bit bigger and then the jack slipped right in place. I used some black silicone RTV sealant to seal up the other two small "slits" below the main hole.
Click to expand...
I have used these binding posts on three different sets of infinity speakers I have worked on. In all cases, I was able to find room above the original clamps. They accept banana, spades and have a cinch hole as well.
Oiyagai 4mm Banana Plug,Pure Copper Binding Post. About $9.00 for a set of 4
 
jefferylhenr said:
I have used these binding posts on three different sets of infinity speakers I have worked on. In all cases, I was able to find room above the original clamps. They accept banana, spades and have a cinch hole as well.
Oiyagai 4mm Banana Plug,Pure Copper Binding Post. About $9.00 for a set of 4
Click to expand...

Have you used these on your RSb's? Do they protrude beyond the back panel? One of the clamps on my RSb's has fallen apart and I want to replace the clamps with short binding posts.
 
They are exactly 3/4 inch and since I am using 3/4 inch birch plywood and a silicone gasket cut out of a cheap placemat between the xover and the back of the cabinet, they do not protrude. They are flush with the back of the cabinet.
 
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