XR6 Isoplanar Loudspeakers on the way

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

Ok.. how about if I cut some black foam or foam rubber absorber pieces on a 45° bevel to line the cabinet door frames behind the grille? How best to attach it without disturbing the baffle board surface?


-Greg
 
Last edited:
If I remember correctly there were horizontal rods to which a grid was attached with pull ties??? Would need to wedge in card to eliminate rattle. Thinking about it now a slit rubber tube (like for windsheild fluid) would work beter.

Never took (or had the time) to do a TEF or FFT analysis on a XR3-7 or ML1-4. Did do 16 and 14 as well as later 2000s models. I guess I am going to have to do some math. I seem to remember some Freq. abberations common to many of the early XRs as Roger Russell reports after the 5s were analyzed by Dr. Toole.

In essence there is a 1.5 dam that will be reflecting back wave fronts that will interact with the primary wave as well as being a new origination edge for the wave fronts that would "spill" over. Isn't physics fun!!!!!

I hope others in the community might help with my rusty math skills. For a quick look at what Roger did look at the XR1051 in which I believe he used a felt like material.
 
When will you finally get to listen to them? While my first thought would be to try to absorb the wave front I think that a better approach would be to spread out the interference effects by using diffraction. But first enjoy for what they are, you can listen wih doors open and closed and make your own judgements.
 
If I remember correctly there were horizontal rods to which a grid was attached with pull ties??? Would need to wedge in card to eliminate rattle. Thinking about it now a slit rubber tube (like for windsheild fluid) would work beter.

Never took (or had the time) to do a TEF or FFT analysis on a XR3-7 or ML1-4. Did do 16 and 14 as well as later 2000s models. I guess I am going to have to do some math. I seem to remember some Freq. abberations common to many of the early XRs as Roger Russell reports after the 5s were analyzed by Dr. Toole.

In essence there is a 1.5 dam that will be reflecting back wave fronts that will interact with the primary wave as well as being a new origination edge for the wave fronts that would "spill" over. Isn't physics fun!!!!!

I hope others in the community might help with my rusty math skills. For a quick look at what Roger did look at the XR1051 in which I believe he used a felt like material.
Gregory are an engineer. He can do the math. Nice that you can purchase 'canned' TEF and FFT and other programs for your home computer these days. Or, an TI Inspire graphing calculator app. On the other hand, a fair amount of what RR has to say is "one man's opinion".
 
When will you finally get to listen to them? While my first thought would be to try to absorb the wave front I think that a better approach would be to spread out the interference effects by using diffraction. But first enjoy for what they are, you can listen with doors open and closed and make your own judgments.

The UMs arrived yesterday late afternoon via UPS. That means Saturday will be XR6 reassembly day. They should be playing by late Saturday afternoon!! I've purchased all new black oxide stainless steel screws for the drivers and cover plates. It was tricky in that dissimilar fasteners were used in each cabinet for the same components. That explains why you've seen LOTS of zip-lock bags with screws. #8 for the fuse plate on one side, and #6 on the other. I could not come up with a way to make them both #6 or #8, so will stick with the original threads.


-Gregory
 
If I remember correctly there were horizontal rods to which a grid was attached with pull ties??? Would need to wedge in card to eliminate rattle. Thinking about it now a slit rubber tube (like for windshield fluid) would work better.

Never took (or had the time) to do a TEF or FFT analysis on a XR3-7 or ML1-4. Did do 16 and 14 as well as later 2000s models. I guess I am going to have to do some math. I seem to remember some Freq. aberrations common to many of the early XRs as Roger Russell reports after the 5s were analyzed by Dr. Toole.

In essence there is a 1.5 dam that will be reflecting back wave fronts that will interact with the primary wave as well as being a new origination edge for the wave fronts that would "spill" over. Isn't physics fun!!!!!

I hope others in the community might help with my rusty math skills. For a quick look at what Roger did look at the XR1051 in which I believe he used a felt like material.

Thanks for that!! The next question would have been: what specifically about the grills needs attention? Are you referring to the 'dam' as top cabinet plate overhang? How do the fuses decrease sound quality?


-Gregory
 
Nice that you can purchase 'canned' TEF and FFT and other programs for your home computer these days. Or, an TI Inspire graphing calculator app. On the other hand, a fair amount of what RR has to say is "one man's opinion".

It would be nice to record frequency response data and export to XLS spreadsheet format. For now it will be the old (tired and damaged) ears to measure the sound.


-Gregory
 
I can still remember kiickin it around with Vandersteen when he was remembering the days he was moving little boxes around trying to find the sweet spot for the mid and treble units by ear. I remember him saying it drove his wife crazy to have "those ugly" boxes in her LR so he came up with the socks to cover them for her.

Anyway a FFT was a 30k plus investment, made time allighnment and problem solving so much easier, and unveiled new issues that might or might not be a problem. He was struggling with all this, feeling it could take away the soul of the speaker craft.

Years later when I took my TEF training the price had dropped to a mere 8k and did not include the hot shot $2800 486 laptop.

Part of my training I did at the church of Crown's national service manager and I brought my trusty McIntosh AA2 along to compare. It shocked the Crown guys that a consumer product company made available such a powerful tool for its dealers. It held its own allowing accurate 1/3 octave low frequecy curves of this 3500 seat church. While it showed the cancelation issues it can not resolve the time. The ability to shift time with the TEF or FFT alows you to explore why there are ripples that you can see in your 1/3 octave AA2 analysis but can't really naildown whats causing it. I now use both taking the output from the AA2 into my laptop to use the AA2 mic and have the AA2 available to excite the room to do low (1000 Hz down)frequency room/speaker analysis.

Whats wrong with a red pen and graph paper?
 
Last edited:
Thanks for that!! The next question would have been: what specifically about the grills needs attention? Are you referring to the 'dam' as top cabinet plate overhang? How do the fuses decrease sound quality?


-Gregory

After a customer complaint about his XR14s sound I found he had replaced the 1.25 amp fuses for his mid/tweeter with 1/2 amp. All I had available was the spare 3 amp which seemed to open up the sound compared to the "stock" 1.25 amp speaker. In good conscience I could not leave it that way so I got the correct fuse and let it be. It opened up an area to explore though, and I was known to use much larger fuses when the speakers would be safe from my teenage boys. They probally limit current turning signal into heat.

Sub note: I used to put a smaller fuse in the kids Surround sub to take it away from them when they would over do it. "There is no sub big enough for a teenage boy"

I think that the entire swing door frame is a dam as well as the overhang. In my opinion the 14/16s with mostly the same parts had a bigger sound stage because of the minimal grilles.
 
Anyway a FFT was a 30k plus investment, made time alignment and problem solving so much easier, and unveiled new issues that might or might not be a problem. He was struggling with all this, feeling it could take away the soul of the speaker craft.

Years later when I took my TEF training the price had dropped to a mere 8k and did not include the hot shot $2800 486 laptop. Whats wrong with a red pen and graph paper?

Forgot to mention there's a Tiltall tripod, a vintage 80's Tandy Sound Level Meter (with output jack), an AudioControl C-101 SA with built-in Pink Noise generator/Mic and a 10-band EQ.

So many EQs -- the C33, the speaker systems both have EQs, and the SA graphic EQ. Might as well play!! can always switch them out. :D


-Gregory
 
I believe there is is freeware available to use the Ratshack meter to do basic FFT work.

Years ago when I went to work for the local BW/Classe dealer the 802Ds sounded horrendous and were embarassing when I invited McIntosh customers to listen and hopefully do business. I was prohibited (complicated story) from using my analysis tools, so for weeks in spare time tried to tweek out the errors. Got tired of fussing around so when boss went out of town brought in tools and got system sorted out in a hour. And still have the documentation in my book of rooms.
 

The XR6s are finally back together again and operational!!


It was a very busy weekend and the reassembly took two days. Saturday was preparation day, soldering the wires to the fuse holders and terminating them. Next was installation of the Upper Mid domes.

Later in the afternoon the woofers were installed. On Sunday the crossovers were installed and the cover plates re-attached. The speakers were tested using a B&K audio signal generator at various frequencies and power levels.

Here are some pics:

XR6_reassembly_08_mids.jpg
Upper mid domes on the bench, one measured 9.9 ohms and the other 10.4 ohms. Screen on left is black, the right one is a slight shade of gray.



Tinsel wires can be seen under the perforated covers/screens in both the above and below photos.

XR6_reassembly_28_tinsel.jpg
Close-up of the installed Upper Mid dome with tinsel wires under the cover/screen.



Driver plate touch-up

The Sharpie pen can be used to touch-up everything from the edges and tips of Mc heat sinks to dome driver base-plates. :)

XR6_reassembly_14_touchup.jpg
The edges of the aluminum base plates got scraped during rebuild. A Sharpie pen makes them `black´ again. You can see where new adhesive was applied.


New wires to Fuse Holders

Wires should have been soldered to the fuse holders first, then twisted and trimmed to the same length before attaching the QD terminals so they would be all the same length. There's only ~1/2" error in length, which is not a show stopper.

XR6_reassembly_11_wires.jpg
Wires were terminated and cut to 15", then soldered to the fuse holders.



Driver installation

The Upper Mids were installed first using Deoxit on each terminal. Then the woofers were installed. The large bass driver gaskets are still intact after more then 30 years!! Laying the cabinets down on the carpet and swinging the doors open onto the sectional sofa works well.

XR6_reassembly_15_cabinet.jpg
View of the XR6 cabinet. Note inside the crossover opening, a cabinet top screw apparently has a misaligned pilot hole.



Grill rattles

There was a concern about grill rattle. Someone, perhaps the original owner used black tie-wraps to the attach the grill to the horizontal grill frame dowels. That should work ok, yes?

XR6_reassembly_27_grill.jpg


Indicator lamps and EQ

The ORANGE warning lamps come on as expected around 100 watts CW. Both LEFT and RIGHT lamps light-up at the same power level thanks to the NEW precision resistors installed on the crossover boards. The recapped MQ104 works fine and the five bass boost positions work ok.

Crossovers

The crossovers were wrapped in packing material and set inside the upper cabinet compartment, propped up against the back wall behind the inside brace. Due to the height of the inductors the bubble wrap is lifted off the power resistors and will not melt. The crossover boards will be CAREFULLY attached to the inside back wall. I believe it was a wise more to fore-go the crossover enclosures. That whole assembly and its damping issues were eliminated. The enclosures are being stored in a safe place, should anyone want to reinstall them.

How do they sound?

Initial tests with an audio Sig-gen were good and all drivers were radiating. There was a problem with the RIGHT S/N 1635 woofer. It has a `buzz´ at all frequencies below ~85 Hz at power levels above 20 watts continuous sine wave. It sounds like a wire is against the cone, but I fear it's the voice coil. This driver may need to go back to the NewFoam. They have a warranty (one year was it?) so there's no big risk, however at higher power levels (20 to 100 watts) the driver goes into a 'whop-whop-whop-whop' mode below 30 Hz, like a helicopter blade!! What do you suppose that means? :scratch2:

Generally I like the way they sound, with more lower mid presence that the Thiels. Both LEFT and RIGHT XR6s sound well matched, as they are only 3 to 4 feet apart right now. We played a Blue-ray DVD "Black Hawk Down" last night and they sound fine. They're warm and much less harsh that the Thiels, but lack the transient attack.

More photos

New shiny black #6, #8 and #10 x 1" stainless steel screws were purchased to replaced the original sheet metal screws, some of which were `lunched up´ from previous servicing. The factory screws were apparently from multiple sources and inconsistent in shaft and head diameter. The new screws are more uniform. Additional photos of the reassembled XR6s will be posted soon.


They sure are beautiful looking.. and have a nice warm and full sound!! :thumbsup:


-Greg
 
Last edited:
Sounds like you have a air leak. It was easy to warp the frame on the gasket models and scrapping off the black caulk was a pain. Would use window rope caulk (comes in strips like a ribbon cable) to seal.

The pull ties were factory, grill would rattle against dowel.

I'm sure the speaker guys would have tested in free air, I think you might have a wire touching the frame.
 
Last edited:
Sounds like you have a air leak. It was easy to warp the frame on the gasket models and scrapping off the black caulk was a pain. Would use window rope caulk (comes in strips like a ribbon cable) to seal.

I'm sure the speaker guys would have tested in free air, I think you might have a wire touching the frame.

The pull ties were factory, grill would rattle against dowel.

You say it could be either an air leak around the gasket, or a wire buzzing on the frame? Would you install the woofers with cabinets standing, or lying on their back? The Thiel woofers were installed with the cabinets leaning on the sofa at an incline, but they didn't have hinged doors!

I'm starting to worry because #1635 was ~1.5 to 2 years older than #1634 and the surround of '35 had detached. Whats more, the material had shredded and fragments had fallen into the absorber. I tested that one with the EQ when the foam was shot, and it went into the same 'wop-wop-wop' mode. Hopefully the rear come edge isn't hammered.

The bass drivers sound ok at 20 watts, but they must be able to cleanly handle 100 watts CW down to 20 Hz, or I'm not going to PASS them as functional!!


-Gregory
 
Last edited:
I've emailed you a copy of the schematic repair notes.

If I remember right the woofer wires were twisted togather and covered with rockwool to either side of the woofer. With the speaker on its back you have to be diligent to spread the wires to not touch the woofer magnet. Help is OK. Woofer is heavy, ackward, and the wires are just long enough.

I do not remember what part of the cabinet is subject to woofer pressure but when there are leaks weird sounds prevail.
 
I've emailed you a copy of the schematic repair notes.

If I remember right the woofer wires were twisted together and covered with rockwool to either side of the woofer. With the speaker on its back you have to be diligent to spread the wires to not touch the woofer magnet. Help is OK. Woofer is heavy, awkward, and the wires are just long enough.

I do not remember what part of the cabinet is subject to woofer pressure but when there are leaks weird sounds prevail.

Thanks man, got your PDF doc. I'll have to make some calls (messages) and come up with a troubleshooting plan.


-Gregory
 
Woofer buzzing

Turns out that NewFoam in Rochester, NY is going to be a big help in remedying the bass driver issues. They're the ones that refoamed the woofers as recommended by Roger Russell. David (at The Speaker Place) has been especially helpful, advising to operate the driver and gently press on the cone in four positions (N, S, E, W) near the outer edge to check for 'rubbing' or alignment. Also to test the driver out of the cabinet and check backside of the cone and tinsel wires, etc. Roger also suggested four or five tests that he used to do back at the Lab.

NewFoam www.newfoam.com/ can do whatever it takes to make it right, up to and including exchanging for a new driver which would be refoamed just like the other 'good' one.

So the McIntosh projects go on! :thmbsp:


-Gregory
 
Last edited:
I've emailed you a copy of the schematic repair notes.

If I remember right the woofer wires were twisted togather and covered with rockwool to either side of the woofer. With the speaker on its back you have to be diligent to spread the wires to not touch the woofer magnet. Help is OK. Woofer is heavy, ackward, and the wires are just long enough.

I do not remember what part of the cabinet is subject to woofer pressure but when there are leaks weird sounds prevail.

I remember trying to get the leads on the back of those woofers too! man that was an exercise in manual dexterity! they are on either side of the magnets and its as if they JUST arent long enough, but I got em back in. :banana:
 
I remember trying to get the leads on the back of those woofers too! man that was an exercise in manual dexterity! they are on either side of the magnets and its as if they JUST aren't long enough, but I got em back in. :banana:

Woofer whop

Have made progress on the XR6 verification tests. Starting with the whop-whop-whop sound from S/N 1635 woofer (Right side), step one was to tighten the woofer mounting screws with took an extra 1/4 turn or more. It became apparent that I was using low preamp/amp gain and little Sig gen attenuation. After switching to -20 dB on the B&K (0, -20, -40) the 'whop-ing' cleared up.. but why the right channel and not the left? Could be an air leak?

XR6_generator_16.jpg
Low-end B&K audio generator used for system test. The unit was purchased on ebay and extensively restored. Also note Spec-An Mic on left.



The Sig Gen was bought on ebay and misrepresented as 'like new.' What was delivered was a rusted and corroded piece of junk that wasn't usable without extensive restoration inside and out, and someone bid the price WAY too high. :no:


Buzzing

Now that the whopping was gone, the tests focused on remedy of the 'buzzing' which develops below 85 Hz and diminishes down to ~30 Hz. It's either a loose wire or the coil is rubbing. The woofer will need to be pulled and inspected, then operated out of the cabinet. That is the recommendation of both NewFoam and Roger.


Speaker Terminals

While at it, I took the opportunity to examine the spring loaded input connector assembly for conversion to 5-way binding posts. Here are some photos of the input parts:

XR6_connector_01.jpg


XR6_connector_03.jpg
Photos of XR6 input connectors. One of the spring tab pieces is missing.


What would you suggest for a 5-way post mounting scheme? It must be first rate quality and NO hacking!! Was thinking of buying some aluminum plate stock, drilling and spray painting it black. Any suggestions on connectors? Parts Express?


-Greg
 
Last edited:
I always used Ponoma 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 probally 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.
 
Last edited:
Back
Top Bottom