XR6 Isoplanar Loudspeakers on the way

[Gregory]

XR6 Crossover update

It's been a very productive day. The last few caps arrived yesterday, and by noon they were tabulated and matched up for installation. Let's get right into the photos.

Rebuilt XR6 networks with precision components







Close-up view of components mounted with Hot Glue

Everything was checked, checked again and triple checked. They should plug in and play just fine!! A couple more close-up views.








Error charts

Let's take a few minutes to look at the NEW component errors vs the schematic values. After measuring three or four batches of 22uF, 47uF and 50uF caps an error correction factor was found that was applied to the electrolytics. Here are the results.






Well the cap errors aren't quite right. C4 which is the 6.0uF cap, is actually a 6.2uF Poly at 1% tolerance, so the errors for that component will be higher. At least they're well matched side-to-side.




Original crossover boards

Compare the NEW build to the original crossovers.. a significant improvement and more uniform!!







That's about it for now. What a FUN project!!


-Greg

 

[MX117.MC7150]

As always, very nice work (and pic's). What clear 'goo' did you use to mount the caps?

 

[Gregory]

As always, very nice work (and pic's). What clear 'goo' did you use to mount the caps?

Thanks for the fine comments.

In contrast to the original crossovers the new build is a BIG improvement and will most definitely sound better!!

The `goo´ is from glue sticks. I bought a hot glue gun and a supply of High-Performance glue sticks (labeled Super Glue) at Sears for the Thiel crossovers. That glue was more of a white color. There were only two sticks left, and when going back to Sears, that item was no longer stocked. Instead they had Ad tech Multi-temp glue sticks which are CLEAR.


The application started off nice and smooth, but the glue started coming out with lots of air bubbles (see below.)







The components are stuck down all right!!

It took 2-1/2 to 3 sticks of glue to do both crossover boards. Tiny `strings´ like spider webs trail off each bead. I'll have to contact Ad-tech and ask about air in the glue. Turns out I got dozens of FREE GLUE STICKS from the regional distributor!!


Crossover boards and components drawn in AutoCAD

It was known that the caps from Parts Express would fit because they were laid out in CAD previously. See the sketch below.




Looking good!!


-Greg

 

[Gregory]

Let's give this one bump, as some have expressed how they enjoy seeing detailed rebuild projects. It could be motivation for others to restore old Mc units.


Woofer Rebulid

The 036-0347 bass drivers (woofers) came back from re-foaming on Friday! It took just three weeks to turn them around, well maybe 3-1/2 counting packing and shipping. Suppose the seller, who was the original owner apparently didn't want to bother with disassembly etc. What a great opportunity for an electronics tech-minded individual!! Let's have a look.

Before

The following is a photo of the XR6 woofer on the table being prepped for shipping. You can see the deterioration of the surround, primarily on the UPPER edge. There's a slight buildup of micro-dust on the lower cone that looks like a semi-circular ring. The local home store had 16-packs of inexpensive flat-head screws which were used as standoff for packing. How about that 60's style GE `tire wrench´ nut driver?




Packaging

The woofers were cling-wrapped to 12"x12"x1/4" plywood panels that set perfectly in 12"x12" INNER boxes. The warp also keeps out foam chips and other debris. The 12" cubed boxes had break-lines near the top to cut down or adjust the height. The extra length was used as `flaps´ to hold the units in place. These parcels were then double boxed. The total shipping weight of each package was 18 lbs.







After

The drivers showed up on Friday, however UPS destroyed the boxes that I bought specifically to ship the woofers. Both were crushed and one was split open down the corner! Good thing for double boxing. Here are a couple views of the new surrounds and dust caps. They are BIG and soft, and made of a polyether (sp) that should last at least 10 years depending on the air in the users home. If you look closely you'll see the slight dust ring on the right 3:30 position in the closeup view.







So you don't have to ask, they were sent to NewFoam in Rochester NY as described on Roger's web page. I'm a tough customer and so far am satisfied with their work which carries a 1 year warranty on materials and workmanship.

It's getting exciting with only one month to go until these beauties are ready for regular duty.

Hopefully they will replace the Thiels that are so bight and forward, but to their credit they are VERY good for DVD video watching!! The XR6s are beautiful and really catch ones eye in the room. Hopefully they will sound GOOD and be suitable for extended listening without fatigue.. that's the plan anyway.


-Greg

 

[jchouston]

Greggory, you are one intense man.


I found a pair of XR5's at an estate sale recently, but haven't put them to use because they need to be repaired. The condition of both speakers is great (7.5/10), but I fear some of the drivers need to be worked on. Moving these things is a chore!

The sad thing is that my knowledge of such matters is SO rudimentary (especially in light of your posts) that I almost fear inept at attempting to diagnose the problems.

 

[Gregory]

I found a pair of XR5's at an estate sale recently, but haven't put them to use because they need to be repaired. The condition of both speakers is great (7.5/10) but I fear some of the drivers need to be worked on. Moving these things is a chore!

Thanks man.. too bad we don't live across town from each other, as I'd enjoy getting involved. :yes:

After posting the photos, there appears now to be a misalignment in the new surrounds? Have a look at the lower close-up edge photo. Notice the standoff nut is right up against the foam. Now look at the wide photo above it.. at the opposite standoff nut on the left. You'll see a space between it and the foam. That draws ones eye to the surround which appears shifted to the right. There is no exposed cone shoulder on the left, and some exposed on the right with adhesive visible.

Is that going to be ok?

I told those guys at NewFoam "this is an important (and hi-vis) project!!"

-Greg

 

[jimreeves]

That draws ones eye to the surround which appears shifted to the right. There is no exposed cone shoulder on the left, and some exposed on the right with adhesive visible.

Is that going to be ok? :scratch2:

I told those guys at NewFoam "this is an important (and hi-vis) project!!"

-Gregory

Hi Gregory, enjoying your post!

I had similar results refoaming my Infinity Watkins woofers and in my case the foam offset was important. In my case, the original spider-to-cone attachment was slightly misaligned so that the outer cone edge was approx 2mm out of alignment with the basket. Because of this it was necessary to mount the foam surround out of alignment with the basket in order to center the voicecoil in the flux gap and avoid rubbing. I can't say that this is true in your case, but could be the explanation.
It should be easy to check this by connecting the woofer to a 30hz test tone on your bench. Hold the woofer at various angles to be sure there is no vc rubbing. Good luck! :thmbsp:

 

[jdwk]

Thanks man.. too bad we don't live across town from each other, as I'd enjoy getting involved. :yes:

After posting the photos, there appears now to be a misalignment in the new surrounds? Have a look at the lower close-up edge photo. Notice the standoff nut is right up against the foam. Now look at the wide photo above it.. at the opposite standoff nut on the left. You'll see a space between it and the foam. That draws ones eye to the surround which appears shifted to the right. There is no exposed cone shoulder on the left, and some exposed on the right with adhesive visible.

Is that going to be ok? :scratch2:

I told those guys at NewFoam "this is an important (and hi-vis) project!!"

-Gregory

My XR 7's came back like that too. He told me the woofer baskets are stamped out imperfectly. I have heard no rubbing on mine.

 

[jdwk]

Ya know I was thinking of updating the speaker terminals to the newer ones that will take banana plugs and up to 4awg, was wondering if you had thought about it?

 

[Gregory]

Ya know I was thinking of updating the speaker terminals to the newer ones that will take banana plugs and up to 4awg, was wondering if you had thought about it?

One of the items that need attention is.. terminals on S/N 1635. The original are spring-clip type, and one of the TABS is missing its plastic piece. It would be relatively easy to fab a part for that end of the speaker. The cover needs some spray paint too.




A tighter and more positive connection would be best. Convenience isn't the most important factor. Hate to say it but someone mentioned RadShak for a replacement spring clip. In all honesty I haven't paid much attention to that side of the boxes since they arrives. The pic is an inspection photo.

You would have to design a scheme based on available parts, and it must be of high enough quality so as NOT to look like a kludge.


-Greg

 

[c_dk]

This was a design issue that I could never get a satsifactory answer to.
The earlier MLs had bannanas so we would pull the clips and replace with bannana jacks. On later XRs had to pull woofer to attach to X-over.

 

[jdwk]

This was a design issue that I could never get a satsifactory answer to.
The earlier MLs had bannanas so we would pull the clips and replace with bannana jacks. On later XRs had to pull woofer to attach to X-over.

so you cant just remove that plate and put the new connectors on by just soldering new ones where the old ones go in? if you unscrewed the plate and fashioned a new one?

 

[c_dk]

As I remember.....

Purchase two pr chassis mount 5 way binding post(r&b) and some 14-16 ga. ring w/crinpon lugs.

Flip over your 3,5,6,or 7 and remove the screws, The wires pass thru 2 holes in the metal bracket. Cut, crimp, assemble posts wirh insulators, tighten and enjoy with bananna plugs on your wires.

These did not fail as often as the later XRs which had their connections a foot off the floor and therefore subject to much more leveridge. Those needed the woffer removed to repair

 

[Gregory]

Thought I'd give this one a bump

As of yesterday the upper-mids have been out for rebuild 12 weeks. McIntosh quoted 10-12 weeks so apparently they are busy or short staffed.. purely speculation. I'd not want to rush the process and compromise quality. The XR6s have been moved to a `safe´ corner of the room for the time being. We really would like to hear them soon. The XR6 purchase and restoration project began on March 15th of this year when I first contacted the seller. That would be 5 months ago!!

New QD terminals

A set of replacement Quick Disconnect terminals arrived from Digikey in the past couple of weeks. It was difficult to locate the correct size, which is female 0.205 wide x 0.020 thick, AWG 16.


New 0.205 x 0.020 female Quick Disconnect terminals for the XR6 fuse wires. There's still some black goop on the left lug.


Already have a supply of 16 AWG Red and White hookup wire!


Spools of red and white 16 AWG hookup wire to connect fuse plate to the crossover terminals.


Now all the wiring will match, and I'll have the option of LONGER fuse wires should the crossover boards be mounted in back.

These XR6 babies seem rather oddly matched for sequential S/Ns. I think the 4-way, 12" XR6 system will be quite adequate for the room size and a good bit warmer than the harsh Thiels.


-Greg

 

[Gregory]

Another update.. got a call from Brian in Parts yesterday and the UM (upper-mid) domes are ready!!

Woo-hoo

I has been 15 weeks since they went out!! So the XR6s will be re-assembled and tested next Saturday the 18th. The plan now is to abandon the original crossover enclosures, putting them aside on the shelf, and instead place the crossovers in the upper compartment in bubble wrap for initial tests.

Then a small cordless drill (or hand-cranked drill) that will fit through the crossover port will be needed to CAREFULLY drill holes to depth in the back wall. The crossovers will be mounted there with absorbed pad underneath (same as the Thiel crossovers.) That should remove ANY resonance or coloration due to thin sheet-metal crossover boxes that were attached and coupled to the front baffle board.


-Greg

 

[c_dk]

Back in the day I tried to convince Mr Painchaud to start a core program like the auto repair industry does for water pumps etc. but he would not.. I even offerd to supply the first cores from the blown domes I had in the back room from MLs and XRs, but to no avail.

I know you are worried about the Xovers, but back in the day, the grills, and binding posts drove us nuts. THE GRILLEs will rattle. Would use business cards out in the field to shim, a lasting memory of me in all those voiced systems. If I was modding these I would look to tame early refections off the grille box frame and replace the binding post with 5 ways.

If you dare, increasing the value or bypassing completely the fuses will improve the sound but at $65.00 back in the 80s, never dared leaving the domes exposed that way. If I was modding a pair I would look to a modern thyristor type circuit.

Have fun going back to 1978, and remember I can help with the MQs.

 

[MX117.MC7150]

.......putting them aside on the shelf, and instead place the xovers in the upper compartment in bubble wrap for initial tests. -Gregory

Bubblewrap? Doubt that any parts in an x-over will get very hot, but the melting point of bubblewrap is quite low, so never say never.

 

[Gregory]

Back in the day I tried to convince Mr Painchaud to start a core program like the auto repair industry does for water pumps etc. but he would not.. I even offered to supply the first cores from the blown domes I had in the back room from MLs and XRs, but to no avail.

I know you are worried about the crossovers, but back in the day, the grills, and binding posts drove us nuts. THE GRILLs will rattle. Would use business cards out in the field to shim, a lasting memory of me in all those voiced systems. If I was modding these I would look to tame early reflections off the grille box frame and replace the binding post with 5 ways.

If you dare, increasing the value or bypassing completely the fuses will improve the sound but at $65.00 back in the 80s, never dared leaving the domes exposed that way. If I was modding a pair I would look to a modern thyristor type circuit.

Have fun going back to 1978, and remember I can help with the MQs.

Thanks and sorry for the delay in responding. I'd like to PM you with some off-line questions. You have a LOT of good info and insight into the older products.


-Greg

 

[Gregory]

Bubblewrap? Doubt that any parts in an x-over will get very hot, but the melting point of bubble wrap is quite low, so never say never.

Good point. Might as well get them mounted. All that's needed is a small hand drill, then vacuum out the shavings and apply the screw.. not too tight and not too loose. It should be a fun weekend!!

BTW, the UMs should be arriving today or tomorrow, certainly by Friday.


-Greg

 

[c_dk]

PM is fine but in a forum we all will get more input.

With the chatter about room perfect and audissy it causes me to remember when we would use our tools to correct room issues before we had to cover them up. Gordon would send me on so many goose chases but I learned stuff.

The turntable guys have now got me thinking again about Turntables. When I was in my audio storage I also saw my Wild boxed up. Might have to get it out to post some pics.