Got Some Qb's in Need of Some Lovin'

Met an interesting guy while doing so. He had to start cleaning things out and decided to keep the JBL's he's acquired and get rid of these. He's going to stick with his JBL L-200's and rebuilt Metrogon along with numerous smaller ones.

Anyway once I determined everything works I bit on them because out here they just don't come up that often. Especially at a decent price. The velcro strips are long gone along with the Infinity symbols but all drivers work and are original.

First to check was the fuses on the EMIT's. 3AMP! So I replaced them with the smallest I had on hand which is 1amp until I can track down some 3/4's. The pots work smoothly and easily with no scratchiness or dead spots.

The obvious thing is they used screwed in furniture trim to hold the grills on no matter where the holes ended up on the baffle or if it screwed up the acoustic seal. After pulling and resealing all the drivers, adding some fill and replacing missing screws, I hooked them up and they sound wonderful! Quite frankly I was surprised how much smoother and natural they sound compared to my RSb's. Especially the mids are so freaky good I can't stop listening!

Before I embark on some of the tweaks I've seen others do to brace the cabinets, replace the midrange caps and reseal the cabinets I think I'm just going to enjoy them for a while.

Welcome!

Being so similar to the RSb, I'd expect they perform similar...

Do the mid-range cap, it's a very easy task, and a very noticeably change.

It's odd but the differences between them are quite a change. Poly mids and woofer in the RSb with paper mids and woofer in the Qb. Cabinet is a tad bigger and heavier on the Qb but the RSb has wood veneer instead of vinyl. One thing I noticed is the QB has a sealed chamber around the mid stuffed with rock wool. From what I'm hearing I'm wondering if that isn't something worth doing on the RSb's as well.

While looking similar the sound is much smoother from the mids on down on the QB. Also the bass on the Qb is faster and tighter on recordings with a lot of drums or percussion in general. It's fascinating comparing the two when one is supposed to be a "new and improved" version over the older model yet sound wise obviously isn't.

I did get some velcro strips to put the grills and they are working fine. For a total investment of $4 for the strips why do what happened to these poor guys? Holes through the cabinet that needed to be sealed, one grill broke in half, and upon closer inspection, one of the mids has a hole pierced in it through the surround and the top edge of the speaker. Looks like it was glued back together but it's starting to separate now. I've seen folks recommend using all sorts of things to repair them and I think I'll go get some Aleene's tacky glue and give it a shot.

If that doesn't work I went ahead and ordered a replacement pair on that auction site and will use these as back ups once they come in. Frustrating!!!

Freaky Good

The Qb's are freaky good, aren't they? They just sound so "musical" to me - no extra color or weight, just good response.

Did you measure the resistance of the EMIT yet? Should be around 3.2 ohms, I think. That 3 amp fuse would be a scary find. Hope they didn't abuse the EMIT. I have the same grill design on my set. The plastic tabs that held the grill frame to the cabinet just never worked well.

Check out the thread where someone got some new fabric for his grills. I think that was on a set of Qa's. He went with black fabric of the same weight and type we have on the Qb's and they looked great.

I got the replacement mids today and will be testing them out tomorrow as tonight I'm just too tired and I don't want to make a silly but costly mistake. When I do replace them however I'm going to reseal and brace the cabinets while I'm in there. I was able to repair the one grill frame with some glue and a clamp so they fit nice and snug now. I will need to either rebuild or replace them at some point though as you can tell the material and the cheap fiberboard they used for the frames is falling apart.

What's odd here is these are original black grill cloths so I don't know if that means these are early or late models Qb's. What doesn't come through in the pictures is they're not a pure black but rather a dark brown/black combination. You can also tell these were sitting in direct sunlight at some point for an extended period.

All drivers worked when I got them I just wasn't paying close enough attention in all my excitement that I actually found some and for so cheap. I've seen EMIT's that fit these on the auction place for 120 or more which is 40 more than I paid for them.

I know what you mean by "musical" as these make playing music seem so effortless. No strain at all in anything I've thrown at them. It's going to be hard to take them down for upgrading as I go.

Dark Brown grill cloth on mine, probably the same. I Think they are a later version because of the fuse holder. The earlier series that I've seen have a "clip in" fuse holder where the entire fuse is visible. I think it is the later ones that have the type you and I are looking at, where you have a screw out "plug" that accepts the fuse.

I think there might even be a later version of these. They would have a different grill attachment method, with four holes in the front baffle that accept pins on the grill frame. Maybe they are pins on the baffle with holes in the grill, I don't know for sure.

Fuse for emits should not exceed 1 1/4

Spitfirejoe said:

Dark Brown grill cloth on mine, probably the same. I Think they are a later version because of the fuse holder. The earlier series that I've seen have a "clip in" fuse holder where the entire fuse is visible. I think it is the later ones that have the type you and I are looking at, where you have a screw out "plug" that accepts the fuse.

I think there might even be a later version of these. They would have a different grill attachment method, with four holes in the front baffle that accept pins on the grill frame. Maybe they are pins on the baffle with holes in the grill, I don't know for sure.

Click to expand...

And I have personally seen two versions of the clip-in type fuse holders; vertical Like my 1978 Qbs and a horizontal version. Both of these styles have only one adjustment pot on the crossover, for the midrange.

Yes there seems to be several versions of which I must have a later model I'm guessing. I've seen both types of crossovers on epay. One with the mid only pot with a visible fuse and Qb clearly on the label and ones like mine that have both and the mid and high and the screw in fuse holder.

It's not really a surprise as Infinity seemed to have a great deal of experimenting going on and would change designs in many ways without a peep to anyone. I'm just glad I got a fully working pair even if they do have some issues I can deal with as I go. From many of the other threads here and elsewhere it seems the baby Q series - b,a & e had cabinet sealing issues and a decided lack of helpful polyfill.

Having the Qb and Qe I can say they sound wonderful when working! The Qb is causing more stop and gawk moments than I'm used to. I worry for my neck bones from being pulled up short all the time.

Chigger: Yes I know it SAYS to use a 1 1/4 amp fuse but I trust many of the gurus here who say 1 amp or less is crucial to a long happy life for the EMIT's. Most recommending finding a 3/4 and sticking with that. My Qe and RSb both have 3/4's which one will donate to the Qb's shortly.