A whimsical Monitor 4.6 upgrade, with pics

geoff727

Hello all,

This is a project that's going to Salt Lake City very shortly. I've had these speakers for a few years. The pictures show a Monitor 4.6 pair that was on ebay recently. I don't have any pictures of mine in their original state, but they looked just like those black ones in the photos, except not in as good of shape.

The agenda for these included:

1. Build out the enclosures. For this, I debated on what I wanted to do, but finally settled on making the enclosure walls 1/2-inch thicker, all the way around. I've been curious about the look of a larger bevel on the Monitor speakers, and with these I had the chance to experiment.

2. Crossover work, of course.

3. New oak veneer and finish.

4. New grill cloth and refinished metal badges, which replaced the plastic ones.

5. Replacement of the vinyl front face with a twill-weave carbon fiber (the real thing, not vinyl look-alike).

6. Inserts for spikes, furniture gliders, whatever.

7. Mix and match better individual drivers.

8. Beef up the mounting for the woofer.

Pics following....

geoff727

I'm just going to post a bunch of pictures....

Here are the new crossovers, built on MDF. The inductors were retained from original, but that's all. The original PCB was hung off the back of the spring-clip cup. This one is obviously much more robust.

The underside looks messy, and it is. I quickly hand-routed channels for each of the wire runs. Everything is soldered up and tucked into the channels, after which it's all sealed in epoxy. There is no exposed copper anywhere on the crossovers, binding posts, or quick-disconnects. Everything is soldered and sealed. Thus, one never has to worry about oxidation of the Monster Cable wire. Even though the bottom looks messy, I wanted to keep top-side nice and neat.

The crossovers are very chunky-feeling. Thumping on them yields a very dull and quick-decaying 'thud'.

One small thing that I think is kool.... The nuts on the underside to hold the terminal strip- in order for one to loosen, it has to force a tightening of the other one, and vice versa. I like details like that.

geoff727

I added some MDF material behind the cutout of the woofer mount. It is 1/4-inch thicker now, for the woofer to have a bit more material to work against when producing sound. I subtracted some material from the rear wall, since I was thickening out the enclosures anyway.

The T-nuts are cemented and contoured in. Yes, I know about hurricane nuts, but T-nuts are what's available when I go to the hardware store down the street, so that's what I use.

There are two pictures which show the difference between original and the better mounting.

geoff727

On the outside...

I far prefer the look of the larger enclosures and more pronounced edge bevel. At least when the grilles are off. With the grilles on, at some angles the look is slightly awkward. I think it would look better with the softer-lined grilles of the '80's Monitor series instead of the highly angular Series 2 grilles.

The angles of the grilles don't match the angle of the enclosure bevel, and this may be part of the odd look at certain angles. Not to mention that the grilles themselves are not made with a perfect fit. The angle of the bevel is the same as what existed when the speakers were stock.

Stock, I thought, it's too much grille for the speaker. Now, it's too much speaker for the grille at certain angles. I say, ditch the grilles! Most things sound better with the grilles off anyway.

I notice that in some of these photos, the stain appears blotchy. This bothers me, as the appearance of the speakers in real life is not that disturbing. Most of this is the background that is being reflected off the semi-gloss finish.

geoff727

Enough of the grilles They look better without them!

geoff727

Some more....

geoff727

The rear....

geoff727

The attachment hardware, stainless steel. The back of the tweeter (SL2500) faceplate was molded with lots of recessed cavities. This is nice, as I was able to fill each one with an epoxy/Repti-sand mixture to help damp vibrations in the faceplate. A knuckle rap on the faceplate now gives a quick-decaying "thud" instead of a long-decaying "theeeeng".

For the woofer, I did things a little different this time. Accompanying the bolt is a lock-washer, then one of those plasticized washers with one flattened edge (for the sake of the woofer surround), and then a contoured speed-nut. I put the speed-nut on there so that pressure from the bolt was a little more evenly distributed around that immediate area. I like the way this came out.

geoff727

And a few more pictures to finish up.

Things I like about this project:

1. The carbon fiber. This is a big improvement. Aside from the exotic looks, it helps the damping of the front baffle. Using a stethoscope held to various spots on the front baffle, I tapped on places around the enclosure of the speaker which was not yet treated with the carbon fiber vs. one that had the fiber applied. The difference in damping was immediately noticeable. Although I am not good at identifying frequencies by ear, there was a very prominent frequency present in the untreated front baffle vs. the treated baffle. On the untreated baffle, this frequency 'hung on' for an identifiable period of time. On the treated baffle, it was gone, or at least so short in duration that I could no longer detect it by ear. Finances allowing, I'll be doing this on future Polk projects, including the SRS 2s. This stuff is not cheap; and with a (45-degree) twill weave, if you want a symmetrical look between the two speakers you have to rotate the fiber 90 degrees. This requires buying a lot more material. In the future, I will probably use a plain weave for large projects.

2. I like the way the semi-gloss finish turned out.

3. Much better vibration damping across the board- thicker enclosures, tweeter faceplates, woofer Dynamat (of course! ), more stout crossovers, custom tweeter and woofer gaskets, front baffle damping, etc.


Things I don't like about this project:

1. The somewhat awkward look of the grilles. It might have been better to make new grilles.

Anyway, I hope you all enjoy!

Geoff

Nightfall

Good lord man. Those might be the nicest Monitor 4's on the planet.

[Deleted User]

Very nice project, well done!

Nightfall

I have to know. How much money and hours?

westmassguy

Beautiful job! Just a suggestion, the RDO-198-1 Tweeters are much smoother and more detailed than the SL2500s.

heiney9

Awesome, but how do they sound?

H9

drumminman

Really nice Geoff. Outstanding workmanship as usual.

Mr. Bubbles

Very nice work! I didn't see any blotchyness, just some reflections from the carpet/ rug it appeared. Again; Very nice

Easy Runnin

Beautiful work. I really like the carbon fiber. Wher do you get it?

Face

Nice job!

zingo

You are a mad scientist of the best kind, and I bow to all your knowledge and talent.

Wanna bring these speakers over when you come to checkout my SRS 2s?

gmjungbluth

These are beautiful! Excellent work!!!!

cnh

Absolutely "beautiful"! Too bad I spent most of my shop days daydreaming and carrying around copies of Camus' The Stranger, Oscar Wilde's De Profundis, and Hesse's Magister Ludi. I spent a lot of my time outside the practical world of tools and labor. And I'm still pretty much of a dreamer who'd rather read, write or just listen to music than solder, sand, or saw. lol

But I can appreciate the beauty of good craftsmanship. And that's pretty impressive. But don't expect yours truly to ever do anything like that. lol

cnh

Mystery

Man, some people have all the time and skill.
Good job!

TNHNDYMAN

Very, very nice. The finish is gorgeous.

VR3

Those turned out great! Very nice!

geoff727

Regarding time, money, sound, etc.

These were done for somebody else, of course. And there are always priorities given as far as what to spend money on and what not to. RDO198 vs. SL2500....not a priority in this case. The veneer and finish...using veneer and dyes/stains/finishes I already had on hand. Building out the enclosures...not expensive, just some MDF. The carbon fiber...willing to take the plunge here.

Ultimately, one can spend incredible amounts of money on what really is, and will always be, just a Monitor 4.6 (albeit a much better one). Same drivers, same internal volume, same vented alignment. In that respect, projects like this are kind of goofy. But, if someone has a specific need (like a bookshelf speaker no taller than 18" for example) then they fit the bill nicely while maintaining a fairly reasonable cost. In other words, they are going to someone who has a specific need for something this size. Were I going to keep them for myself, I would sell the 2500's, buy two more 6502's, take a full round of measurements on the drivers, and re-engineer as a flat vented alignment (like a QB3) in an MTM configuration - in other words a whole new speaker that looks more like an 8tl. This would take a little more time though. I've actually toyed with this idea. See the attached photo, a picture of an 8tl that I modified.

As far as the time committed, these took me about 3 months.

I'll see if I can find a picture of the network mounted inside the enclosure.

G~

geoff727

Here's the photo I was thinking of, the crossover mounted inside the enclosure. It's hard to see, but it's on 1/4" standoffs, screwed down with just a bit of cement so nothing comes loose in transit. Plus, one more of the carbon fiber finish.

Thank you guys for the compliments, it's nice to see the same names as last time!

Jake, I would be happy to bring them over. But honestly, I want them boxed up and out of here, as quick as possible

boston1450

Beautiful job well done. Now time for them to enjoy them

geoff727

geoff727 wrote: »

Were I going to keep them for myself, I would sell the 2500's, buy two more 6502's,

I should have said... 6502's or other appropriate driver considering the parameters.

Oldfatdogs

As always beautiful work,good to see you posting again.
Dan

kcoc321

Those look awesome Geoff... but then I would expect nothing less
You are an artist ")

The most amazing thing to me, aside of your dedication to 'perfection' is
that you do this all out of a two bedroom apartment, with no shop/ garage or
paint booth or nuthin... in your flippin dining room & deck ...lol

Mike Reeter

Love the new look, you have an amazing talent indeed.