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Heresy II Motorboards or "Neurosis Sets In!"


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Posted (edited)

I'm in the middle of my Heresy II refurbishing journey and have posted a few related topics recently.  I am about ready to apply Danish Oil having just finished a sanding of the cabinets with 220 and 400 sandpaper and 0000 steel wool.

 

But today the motor boards leapt out and caught my eye.  I am thinking of touching them up, perhaps with spray paint, and I am curious what others have done, but, but, but . . .  I also have another question/observation:

 

Suddenly I really noticed how thin the motor boards are.  I don't just mean the thickness of the plywood in and of itself, but also the fact that the drivers are so close together leaving not a lot of board to hold them.  In particular, the woofer hole gets within about an inch or less from the squawker hole with the result that there's a rather long and very thin arch (see picture).  Has anyone done anything to reinforce the area around the woofer?  It seems like a lot of weight is being applied to that area with not a lot of board.  The Heresy I design leaves more board because of the internal mounting and, of course, the Cornwalls have much more space between the drivers, so the potential issue seems unique to the HIIs.

 

And yet, a quick internet search doesn't seem to unearth this design as a topic of concern, so it's probably just my neurosis?  I have no desire to replace the boards, and wouldn't know how or with what in any event.  

 

Thoughts?

 

IMG_2518.jpg

Edited by Bulkogi
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Well, the baffle looks fragile, but I have the impression that it is reinforced and stabilized by the drivers themselves when installed, or am I wrong…perhaps similar to the parts of a chassis in racing cars, which only gain stability as a whole when they are mounted on the engine block and at the same time the position of the engine is strengthened. I think that the strength of the chassis is distributed over the entire surface around, and so the delicate parts of the baffle gain significantly more stability.

To stay in your imagination of psychic indications, I prefer the neurosis of a thin baffle to the paranoia of countless bracings.

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1 hour ago, KT88 said:

Well, the baffle looks fragile, but I have the impression that it is reinforced and stabilized by the drivers themselves when installed

 

Just what I was going to say!  The midrange horn flange should hold things firmly -- or not?  Small baffle boards don't resonate as much as large ones??

 

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While agree the back panel needs some bracing.....i just glued extra layer on mine and sealed it up better. I dont think the front motor board is a problem. But you could probably add a 1/4 layer to it to help out. 

 

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DSC00634.JPG

 

After I finished sanding and spraying a couple coats of urethane I papered and taped off the exterior of both cabinets so that the only thing exposed was the motorboard ( there was already overspray on the interior of the cab from the factory) and used a can of spray black lacquer.  

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1 hour ago, garyeanderson said:

DSC00634.JPG

 

After I finished sanding and spraying a couple coats of urethane I papered and taped off the exterior of both cabinets so that the only thing exposed was the motorboard ( there was already overspray on the interior of the cab from the factory) and used a can of spray black lacquer.  

Those are beautiful, Gary!  I'll do the same!  By the way, are your risers also in Oak, but stained darker?  Mine are birch and I'm thinking of staining the risers a dark chocolate for the contrast.  

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Moving the midrange further from the woofer will change the polars. You, meaning YOU, may not hear the difference.

 

I liked what Dean said.

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Posted (edited)
On 6/3/2021 at 12:40 PM, Marvel said:

Moving the midrange further from the woofer will change the polars. You, meaning YOU, may not hear the difference.

 

I liked what Dean said.

 

Thanks.  I didn't understand Dean's comments, but I'm certainly not considering moving the spacing of the holes.  There's no way to do that in any event because the drivers are crammed in and fill up all available space.  My point is that the motor board seems like a weak link and likely the main source of resonance.  It's a possible design issue, though seemingly a benign one, and the only solution would seem to be bracing, but I'm not likely going to try anything.

 

I really am not trying to criticize the sound or durability.  As others have stated, they sound great and clearly hold up well over time.  I was just surprised at how relatively frail they seem compared to the rest of the box.  And I'm neurotic, LOL.

Edited by Bulkogi
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My comment related to the picture Randy posted. Too much bracing radically reduces the internal volume of cabinet, which changes the mathematical alignment with the woofer. 

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2 hours ago, Bulkogi said:

 

.  I was just surprised at how relatively frail they seem compared to the rest of the box.  And I'm neurotic, LOL.

in order to flush mount the drivers , they CNC routed the MDF motorboard  ---on the Heresy 2-3-4 ---Cornwall 2-3-4 -Forte 1-2-3-4 -  Chorus 1-2 , Epic CF series -KLF series - and no issues thus far -

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On ‎6‎/‎3‎/‎2021 at 9:05 AM, Bulkogi said:

Those are beautiful, Gary!  I'll do the same!  By the way, are your risers also in Oak, but stained darker?  Mine are birch and I'm thinking of staining the risers a dark chocolate for the contrast.  

This topic has the gist of what I did but is a more recent build. The risers are made of Brazilian cherry (left over flooring from a friends new house). I have never used stain, I use wood that I like the color of, its tough to scrape through the stain if its not there to show the scrape, dig or gouge.  

 

The risers are not (NOT) the ones in the picture I posted here but they are built in the same manor. I tried to use the same taper cutting jig but it was damaged beyond use so I built another.

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I recently sold a 30-year-old pair of Heresy IIs, and the motorboards were in fine shape.  The new owner messaged me that he was very happy with them.  Klipsch have sold thousands, maybe tens of thousands, of Heresy IIs, with no known problems with the motorboards.

 

You have nothing to worry about.

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On 6/2/2021 at 11:07 PM, KT88 said:

Well, the baffle looks fragile, but I have the impression that it is reinforced and stabilized by the drivers themselves when installed, or am I wrong…perhaps similar to the parts of a chassis in racing cars, which only gain stability as a whole when they are mounted on the engine block and at the same time the position of the engine is strengthened. I think that the strength of the chassis is distributed over the entire surface around, and so the delicate parts of the baffle gain significantly more stability.

To stay in your imagination of psychic indications, I prefer the neurosis of a thin baffle to the paranoia of countless bracings.

 

Racing cars, and some motorbikes, often use the engine as a “stressed member”, meaning it shares the loads on the frame, and doesn’t just sit there in the engine cradle doing nothing but making power.

 

The most extreme cases of using the engine to support the frame that I can think of are the old Vincent V-twins.  The forks attached to the front of the engine, while the rear part of the frame attached to the back of the engine.  Those bikes were last built in the Fifties, but there are still quite a few of them being ridden regularly.  There’s one in my town.

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