XR6 Isoplanar Loudspeakers on the way

I always used Pomona chassis mount 5 way binding posts that would fit right in the existing holes. Will need to change the connectors to rings and would use bananas for speaker wire termination.

You also probably have a air leak where the wires exit the box per the picture showing the loose fit of the caulk around the wires. When you can move this much air to deliver bass to 20 Hz leaks are a pain. I would also check the other pass thru holes making sure the putty is sealing the holes.

As I've stated earlier the crossover mounting is the least of the issues you need to address as you do this update restoration. The 16 is not applicable as it is point to point wired. But I'll think about it.

Measuring with calipers, the two large holes in the connector bracket at 0.62" dia. I didn't think to measure their spacing or check for standard spacing of bananas. The two threaded screw holes are 1.75" apart. Also the Bakelite bracket/plate is 2-3/8" wide.

The speaker can be operated at power on its side to check for air leaks around the input pass-through hole, but not on its back according to Roger. Thinking of it more, the cabinets can be tipped onto their back for servicing... but not on their side due to xover boards temporarily propped in there. I was hoping that everything would be fine on the first shot, but this is going to be an ongoing project. Does that sound familiar? :D

The crossovers in the Thiels are point-to-point wired on 1/4" pieces of Masonite that attach directly to the back wall with sheet metal screws. Gary sent damping pads to go underneath the boards and I bought slightly longer stainless screws at the hardware store. I repositioned them and drilled new pilot holes using three screws each instead of two. They're just as firm and tight as can be!! The issue with the XR6 crossover is.. the rear edge connector comes off at a 90° angle downward (or toward the wall in the new config) so there will need to be standoffs of some kind. I'll probably mount them sideways with connector on the left, and am absolutely convinced that removing the aluminum boxes is the way to go.


-Gregory
 
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Crossover mounting on rear wall


In the last week or two it was discovered (or was it lack of forethought) that the XR6s couldn't be tipped on their side to inspect the input jacks without possible damage to the crossovers, which were stuffed inside wrapped in packing material. The crossovers HAD to be installed permanently before any further tests or restoration could proceed.


Marking and drilling center hole

The mounting process began by determining where to best drill mounting holes in the Crossover Boards. The top-center holes were already there (probably production stations.) A strip of 1/4" thick by 3/8" wide plywood was used to space the boards from the top wall as seen in the photo below. The boards are then centered left-to-right and a pencil was used to mark the edges/corners.

>> Many photos below were taken upside down looking through the crossover port from above with the speaker on its back. <<

XR6_crossover_mounting_17.jpg
Strip of 1/4" thick by 3/8" wide plywood used to space the boards from the top edge (view inverted.)



After the top-center hole is spot drilled, the board is removed and hole is drilled to a depth of 1/2" or until the countersink cutter just makes contact. Turns out that we had a battery powered articulating screwdriver that was perfect for drilling inside the XR6 cabinets through the narrow crossover port. Some photos as follows:

XR6_crossover_mounting_19.jpg
Tiny battery powered screwdriver with hex-drive wood screw pilot bit (view inverted.) PERFECT for the job!!



Fortunately Craftsman has a wood screw Pilot Bit Set (4-piece) available with 1/2" long leading drill points for only $7.99. Since the cabinet walls are 3/4" thick HD particle board, the #8 bit was again PERFECT for drilling to depth. Here you see the pilot bit with hex-shank is inserted into the mini screwdriver. The holes are then opened up by 0.006" with another drill bit.

XR6_crossover_mounting_22.jpg
A second drill is same diameter (0.120") as the sheet metal screw minor diameter. The correct drill-size is important in order to thread the holes properly!!



Marking and drilling side holes

Once the top-center screw is installed and holding the board in place along the spacer strip, the side screws can be marked and drilled. Best is to drill the crossover boards (glass epoxy) to the same diameter as the Pilot bit, then open them up for #8 clearance holes later on. This improves hole alignment.

XR6_crossover_mounting_25.jpg
View of lower right mounting hole being spotted with bit (view inverted.) Crossover board is removed to drill 1/2" deep. See top screw in place to align.


Another view of the handle and 0.120" drill bit which is the same as the minor diameter of the #8 sheet metal screws. This shot is flipped 180° which would be the view when normally looking through the crossover port. The cabinet is laying on its back.


>> It is recommend to have a vacuum handy to suck out chips and drillings at each step of the process. <<


XR6_crossover_mounting_31.jpg
Photo of lower left pilot hole being opened up by 0.006 in.



Here are three crossover board mounting holes drilled and threaded into the back wall of the cabinet.

XR6_crossover_mounting_01.jpg
Three mounting holds drilled with threads cut (screws driven to depth w/o boards.)


Once the pilot holes are drilled, the screws are driven into the holes to cut the threads with a STUBBY #2 Phillips screwdriver. There isn't much trouble threading in the screws with the correct diameter holes. If the pilot hole is too small the Phillips bit will 'jump' the screw-head slots and ruin them!!


>> Mounting screws are #8 x 1-1/2 inch Sheet Metal, Phillips head, 3 each. <<


Crossover Board mounting

High quality 1" thick foam pads were used INSIDE the three mounting screws. Foam cannot be drilled as it will be torn and destroyed. Since the crossovers boards were dissimilar with large BASS inductors located in slightly different positions, the lower-right mounting holes weren't in the same spot for S/N 1634 and 1635 (see screw locations near LARGE inductors.) Therefore foam pads of different width (~1/2") were used. Below is a foam pad (bottom-side up) with double sided tape being applied.

XR6_crossover_mounting_37.jpg
High quality 1" thick, medium stiffness foam with double-sided mounting tape applied. These pads are fixed in place between the screws.


Additional strips of foam could be attached OUTSIDE the mounting screws, extending to the board edge for better support and damping. That would be a good future upgrade!!


Mounting complete

S/N 1634 Crossover Board mounted with edge connector oriented down.

XR6_crossover_mounting_49.jpg


S/N 1635 Crossover Board mounted with edge connector oriented down.

XR6_crossover_mounting_05.jpg
Difficult exposure settings and post processing on these photos.



Close 'em up and Play

It was getting to be 5:00 pm and time to close 'em up and play some music. The crossover cover/fuse wires were attached and the systems tipped back into the standing position. As you can see, the fuse terminals are easily accessible through the front port.

XR6_crossover_mounting_55.jpg
View of crossover board through top port. A very neat job!! The boards are held firmly with three #8 screws and access to the fuse terminals is excellent.


The XR6s are sounding GOOD

We enjoyed listening to the local Country FM station through dinner into the evening, and later played a DVD video from 9:30 to 11:45 pm. The XR6s have a different sound than the Thiels, definitely softer and warm and not as aggressive. The bass extends low to 20 Hz, but it can't compare to the tight and coherent bass extension of the Thiels. These XR6 speakers are keepers for all day listening!!

The older S/N 1635 still cannot pass power handling tests below 85 Hz. There could be an air leak, and perhaps a wire buzzing on the bass driver or the voice coil is rubbing. Below 20 watts they are fine, but there speakers must MEET ALL SPECS as McIntosh guarantees when NEW.


-Greg
 
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XR6 Crossover Board mounting - Part 2


Oops.. posts here on AK can have a maximum of 10 embedded photos including emoticons, so here's the final view of S/N 1635 Crossover Board mounted with edge connector in place. A foam pad or spacer is required behind the Crossover Board because the edge connector need space at the bottom.

The crossovers were propped up behind the horizontal brace over the past couple weeks for initial tests. :no:

XR6_crossover_mounting_13.jpg
S/N 1635 crossover board mounted to the back wall of the XR6 cabinet with edge connector attached. The horizontal cabinet brace is seen inside the upper compartment.



The 1" thick, high-quality foam pad (medium stiffness) is attached to the crossover board with double-sided tape.

XR6_crossover_mounting_42.jpg


The crossover port is narrow from top to bottom. Working in the cabinet and taking photos through that opening isn't easy. It's a challenge but well worth the effort.


A very satisfying project!! :thumbsup:


-Greg
 
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Time to revisit the XR6 restoration and update project


Last we left it, the X-over boards were rebuilt and mounted inside the cabinet on the back wall. Much as I tried and wanted to install the boards into their baffle-mounted chassis, there was no practical way to `dampen´ the rattles and resonances of these boxes!! Paul Klipsch in his bibliography of audio papers wrote the "10 cardinal points" of loudspeaker design. One of these points is: the cabinets will be free of rattles and loose parts

The Next on the agenda is damping of the front grills/doors.. and replacement of the input terminals. Clay is working some fixes as well.


Have ordered a pair of these from PE.

speaker_jacks_1.jpg


Might want to get the dual banana jack assembly which is spaced correctly.


-Greg


p.s. anyone have a shipping carton drawing or recommendation for these?
 
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Seems we all have a better idea of the XR6 frequency response from recent experiments, and the midrange drivers will of through another "subjective test" with ramped/ranging CW from the Sig Gen. It seems the XR6s will need an GRAPHIC EQ to operate enjoyably. That is no problem. Putting it bluntly.. these XR6s are going to need a 10 or 20 band equalizer to sound good, and I think the MQ will be used as well.

This is the most recent Graphic EQ contour for the XR6s on the evening of Dec 23th with MQ-104 Bass set to 3.

The Next on the agenda is damping of the front grills/doors.. and replacement of the input terminals. Clay is working some fixes as well.


Another DVD video last night while seated and listening up close.. the voices and midrange in general were sounding good.

They may take some getting used to. :yes:


-Gregory

So you have the graphic EQ as well as the MQ.....that is an awful lot of EQ filters to bring some normality to those speakers....?
I cant believe the amount of EQ going on there, it just cant sound right like that.....
You are trying to correct deficiencies in the response of the speaker system with EQ which I think is not really the desired approach......
Have you got some other speakers which you can use as a reference while you are auditioning?
You may not realize how your hearing will becoming "familiar" with what these speakers are producing, its definitely worth having some kind of ideal reference so you can monitor how close you are to a well balanced sound....
You would be amazed at how adaptive your hearing is......
Not criticizing what you are doing Gregory, just offering points of observation....
 
Gregory. I'm glad you are listening to them. I was just looking at the picture of your EQ???? it looks like you have the upper bass adjusted lower for the spike??? & the upper mids adjusted lower too???? I can't really see 0 from the angle. Hope you had a good holiday & get a chance to spread the XR6s out a bit.
 
Gregory. I'm glad you are listening to them. I was just looking at the picture of your EQ???? it looks like you have the upper bass adjusted lower for the spike??? & the upper mids adjusted lower too???? I can't really see 0 from the angle. Hope you had a good holiday & get a chance to spread the XR6s out a bit.

Some good questions! With the exception of DVD/ Blu-ray movies, we gave the sound system a rest the last couple days and concentrated on a new PC that Santa delivered. :)

Yeah the sliders are all negative except for the end points. It doesn't matter really (unless you have a good reason to use + slider) because it's all relative. The overall Gain can easily be increased.


The frequency response charts have been moved to the appropriate XR6 thread.


-Gregory
 
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XR6 Grill Damping


Thanks to Clay the ever driving force, I went about suppressing grill resonances/rattles on the XR6s today. The grills are actually doors with high-quality hinges and diamond-cut metal sheets on front, then wrapped in grill cloth.

Step 1. Cut tie-wraps from horizontal dowel rod

cut_tiewraps.jpg


Step 2. Cut rubber strips to size

These are test strips ~1" wide x 3-1/2" long cut from a sheet of 0.063" adhesive-backed rubber left over from efforts to damp the crossover chassis/compartments which wasn't successful.

rubber_strips.jpg


Step 3. Apply strips between dowel rod and grill

Here are two strips inserted between the grill and dowel rod astride the center staple. Best to fit rubber underneath the grill crossings (or X's) directly adjacent the staple.. as long as wedge forces don't pull the staple out! Putting a new and heavier tie-wrap around the dowel, staple and grill would be a GOOD idea. :yes:

grill_staple.jpg


A broader view of the grill door. Not a pretty site at this point.

rubber_damping.jpg


Grill Damping Results

Applying strips or pads of 0.062" (1/16") rubber sheet between the metal diamond-cut grill and the center dowel rod is effective in damping grill door rattles and resonances. The difference is very significant. The plan is to install these rubber pad or bumpers ASAP.


Connector replacement

While the UM drivers are removed from cabinet for unit-level test, and to replace internal FOAM PADS, the original connector strips are being changed to banana jack / binding posts. Below is the terminal with a broken tab.

XR6_connectors.jpg


Pomona binding post

I'm not sure the Pomona 5018 will fit too well. The pass-through holes in the metal bracket are 0.62" dia. Plus they are $47 for a set of four.

Pomona_5018.png


Parts Express binding post

Only one type of binding post was ordered from Parts Express. They may or may not be the final connectors installed.

The threaded shaft of the jack below is 0.187" dia, and the black shoulder-sleeve 0.228" dia. A suitable hole could conceivably be drilled opposite the "slotted hole" where there is enough surrounding material between it and the parallel rectangular holes.

XR6_binding_post.jpg


What do you think? Will we get these babies back in shape? :music:


-Greg
 
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Installing new binding posts


After thinking it over for a few hours, I've decided to simply mount the original connector bracket backwards at the speaker base.. same holes and screws of course. There will be a slight setback WRT to the base board, but the binding jacks protrude 0.875" from the surface due to their length. Be sure to think carefully about mods and proceed conservatively!

Turns out the setback is 0.882" so the new "posts" will be slightly recessed. :thmbsp:

XR6_conenctor_place_rev_II.jpg
Original terminal bracket turned around to install new binding posts on the back side.



Bracket reversed

There will be small gaps on either side when the speaker is back on the floor, but we're talkin' lower base of cabinet so it'd doubtful anyone will notice.

You'd have to get down on the floor like in the photo below to see the bracket anyway.

XR6_conenctor_place_rev_III.jpg
The solution is to turn the original brackets around and drill TWO small holes for the binding posts.



New posts

Mounting holes for the new 0.23" Dia binding posts can be drilled in the opposite face of the bracket.

Best to use the standard dual banana jack spacing.

XR6_binding_post.jpg
New connectors from parts Express should work fine, and have relatively small threaded shafts.


The original connector interface can be restored at a later time if desired simply by switching it around.


-Greg
 
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Back to XR6 restoration


It's winter time again, and I though it would be good to get the XR6's back in the spotlight. The project stalled ~1 year ago, about the time grill rattles were tamed and new rear connectors were about to be installed. You might remember that a bunch or UM drivers didn't seem to be cutting it, or were defective.


UM drivers

There are four Upper Mid (UM) drivers on the shelf here.. make that in the cabinet on the shelf. Two of them are out of Clay's XR16's, and two are from my XR6's. One of Clay's drivers is defective with serious frequency response issues, and BOTH of my drivers came back from McIntosh with damping pads removed. I don't know if Mc is telling the boat'of us to take a hike or what?

XR6_UMs.jpg


Driver unit test

I used a Mic and SPL meter in a controlled set-up to `unit test´ these drivers (like the rebuild vendor should have) and rejected some, reporting distortion. Turns out the SCREENS that cover the domes need to be SECURED with either tie-wraps or screws before test or they will vibrate/resonate which would result in a `test fail.´ At that point, it seemed like a lot of time was wasted. Furthermore drivers should NOT have loose parts, nor should speakers or speaker cabinets! Somebody relay this info to the vendor and let's get real!


What's the way forward

Now it's time to ask the question... stick with the original UM's? or go with a replacement? and if so, which driver? This is no longer a profit decision.. it's about getting a classic pair of speakers up to par, to enjoy in the coming years. Already have well over 1k into these, but not as much the original selling price. It's more about having them in the room producing music. :music:


Please comment!


-Greg
 
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Sorry I don't mean to flood, but there's a lot of material to post.

Had to get the parts out of storage which didn't take long. The current state of the XR6s is.. open wires out the back, and UMs removed from the cabinet.

XR6_terminal_parts.jpg


So many projects.. so little time, and that doesn't count getting confused, having worse eyesight and going deaf! Lol


-Greg
 
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What Greg has done with XR6 was amazing. The information presented here is invaluable. After I updated my XR5 and XRT18, I also found substantial improvements in sound quality by doing the following:
a. Remove fuses out of the circuit
b. Replace internal wires with OCC wires
c. Solder the driver leads, no clips
d. Replace spring clip terminals with quality 5 way binding posts
They are relatively easy tasks and yield tremendous returns in SQ.
 
What Greg has done with XR6 was amazing. The information presented here is invaluable. After I updated my XR5 and XRT18, I also found substantial improvements in sound quality by doing the following:
a. Remove fuses out of the circuit
b. Replace internal wires with OCC wires
c. Solder the driver leads, no clips
d. Replace spring clip terminals with quality 5 way binding posts
They are relatively easy tasks and yield tremendous returns in SQ.
Unfortunately, Greg passed a couple of months ago. I had his speakers here to sell to help settle the estate. They really rocked. Excellent soundstage and depth. The 4 driver layout really exposed details I had not heard on some tracks. Fortunately, we have this thread as an archive and a local HIFI’er bought these to use with a Mac 1900 @cawgijoe sold at the same time.
 
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