XSchop's modded 5jr

xschop

What is the standard paint/coating for inside the cabinets?
I had to chip ALOT of dried dripped glue that would IMO cause alot of vibes as the globules were right up against the walls loosely.

xschop

The second cabinet was worse and the glue dripped all over the sound insulation, but I got it all cleaned out and coated both with 3 coats of auto flat-black primer. I'm testing weather Ill like a gloss-black or Brushed flat-black finish to go with the two-tone billet... Fusion plastic paint works excellent at bonding to vinyl and of coarse plastic. I've done a few 948 Porvette interiors with it....

xschop

The dimension specs are wrong on Mavins site for the SL5000....
Three holes 120° @ 3.10" on the Diameter is correct. The inner thru-hole has to be relieved to allow for tabs with 0.32" on the radius to allow plenty of material for the machine screws of which I will be tapping for 8-32 for all including woofers....

xschop

Chips are flyin'.....MW6502 cutouts are alot easier/faster....

xschop

I went with a 1.125" fluted port...

RandyCroissant

Lookin good! can't wait to see the finished project. Let us know how they sound

xschop

I temporarily reassembled one by clamping the new baffle down to the enclosure and installed x-over, tweet, and woofer to see how the new fluted port sounded.
The factory port noise is GONE. Low volume, high volume, GONE, finally. From owning a set of Monitor 4's and these 5Jr's, I always thought these 5Jrs had port noise that the 4's don't. Tweeters ..... sound MUCH smoother as well. I ran the new X-overs for a few days on the shop system and I know I have to "burn" them in some more.

I'm doing some more prepping to the cabinets. Looks like I'll be going with a satin-black Brushed look for them as well, then I'll assemble both and let em breath.

xschop

I'm growing fond of the hand-brushed look.
I glued the second one together tonight because I only have a pair of long clamps. The Power Grab is set on the other one and I'm starting the fine hand sanding/brushing before final paint and installing drivers.
The 2nd pic shows that the 1/2" billet plate with recesses for tweeter tabs clear by a long-shot. I'll still shrink wrap the terminals. The SL-5000 tweets have a small tab as positive and the large tab negative....

xschop

Looks like I added 5.7 lb to the enclosure. I didn't do the stress calculation, but I could probably park a car tire on the baffle without deflection....
I also found the Power Grab very forgiving on large flat interfacing surfaces up to about 25-30min. You still have time to adjust face plate and reclamp if it moves a little from initial clamping.
The extra .100" I gave for the separation between woofer and tweeter was a two-fold improvement. Extra bridge/deflection strength and at that dimension you don't have to touch/cut on the box at all...new tweeter clears perfectly....

Polkaguy58

I kind of thought that you might be cutting out the front baffle and maybe leaving a half inch shelf to set the metal faceplate into.
I'd be a little worried that any voids between the back of the metal plate and the original woofer's mounting area would cause air turbulence.
You could probably just fill the lower shelf with that glue and let it squish out the center, then trim the residue off with a blade ?

xschop

Ive got one burning in again tonight on my H+ class receiver in the shop. All I hear is beauty. I still can't believe the port noise is GONE.
I guess I could add extra polyurethane rubber bonding agent to fill the void. The Power Grab would take a solid year to dry.

F1nut

I consulted with John at Mavin about what Polk tweeter to use since these old SL1000's are 8ohm and the mw6502's are 4ohm In these early 5jr. So we chose these as they are silk dome as well as 8 ohm, but just as important they are ROUND.

There's more to tweeter specs than the ohm rating. Not to mention it's highly likely that the crossovers will need to be reworked, but it seems you care more about how it looks than sounds.

xschop

My thinking besides being round and Polk branded.... They are 8 ohm with a low extension of 2.2k up to 23k.
I found reference that the 5jr X-overs are at 3,000 hz and I made sure the SL5000's were hooked up polarity-wise like the 5jr's x-over. It's tweeter's NEGATIVE is connected to the positive input....
All I know is these things sound gorgeous.

Polkaguy58

I happen to like messing with speakers and have been doing so for 40 years now.
I know that higher end companies pour millions of dollars into computer aided design and have acoustic and electronic engineers who are light years ahead of me in their knowledge of how speakers work, but I've found that by just employing some common sense and the will to experiment, one can "luck out" once in awhile and come up with something great.
I once took a 50 dollar pair of Radio Shack T-100's, braced the cabinets with an old pair of wooden crutches, stuffed them with the innards of my old Boy Scout sleeping bag and added one high quality cap to the L-pad to bring the KEF silk dome tweeters that I added into the mix at a point where I thought the woofers range would slope off.
They were one of the best sounding speakers I ever owned !
One friend said he A+B'd them to his Klipsch Forte's and like them as much or better.
The thrill is in the hunt.................................

Hofy

I own a pair of Monitor 5jr and can also confirm they do NOT have a circuit board for the crossover. Mine are late 1985 vintage and had the SL2000 tweeters. I replaced them with the RDO194 tweeters and rebuilt the crossovers. A lot less messing around than you have done and sound is great. Of course yours "look" better.

xschop

Well, If you want yours to "sound" better in the bass region, a 1 1/8" diameter x 1.25" length fluted port opens them up and rids the port noise.
I spent most the afternoon listening to these and couldn't be happier. I also notice that I can clearly hear these at a wider angle than before... Icing on the tweeter.

Polkaguy58

I just received word a minute ago that my newest 5 Jr's have been purchased for me............and if that's not enough, my RDO194's got picked up and installed into my Monitor 5's tonight.
The stereo hasn't sounded this good in years !
Still trying to decide whether to run all 4 Jr's or to keep the large/small set up I have now.

xschop

Run em all... Im still hunting for another set to mod.
These have been running non-stop in the shop the last few days. I found a set of speaker stand copies I built years ago and just need to find poly bushings to bolt on. They are designed to mount/unmount longer rods for taller stands using 7/16-14 tpi set screws or all-thread....

Polkaguy58

I guess it's a good thing I don't have access to your equipment or the knowlege to run it............or I'd be making all sorts of FrankenPolk speakers......Like maybe a Time Aligned Junior, with a stepped woofer sitting proud of the faceplate about an inch or so. (heh heh)
Good job, wish I could hear them.
Still want to fabricate a pair of 1/2" clear Lucite cabs some day.
I just finished dialing in my four Jr's, by lining the wall behind the main speakers with cork tile.
I'm working on a couple more foam bass traps for the alcove area where I keep the NHT sub.
Houses Of The Holy never sounded so good !

xschop

Nice, I bet that's a thunderous affair. Four of these would sound symphonic. If I don't find another decent set of cabs, I may just construct an MTM set to match so they'll fit in my office shelves. The challenge would be to keep the front baffle 9 x 17, I would have to have deeper boxes made for sure.

xschop

I finally scored another set of these. I'm on the fence about what design to countersink into the next set or just fly-cut to a nice finish this time...

Polkaguy58

How about a nice brush finish with anodized gold ? (heh heh)

xschop

With a purple set of cabs..... Crown Royal specials?

westmassguy

xschop wrote: »

With a purple set of cabs..... Crown Royal specials?

Now that's an awesome Idea!

Polkaguy58

Well, if you go that far, then you must engrave an imperial crown on the top of the faceplate.............and then maybe fill it with red enamel.

deucekazoo

I think that would be cool to engrave the fronts as they do the high end shotguns.

xschop

And then burn them in with a pint of CR gold. You guys are onto somethin'.

lawdogg

JBL and (Teledyne) AR both at some point used foam or some kind of acoustic absorption material around the drivers (e.g. the JBL LE25 tweeter, and the whole front face of the AR9) ... Think there'd be any benefit to putting some felt padding on that bare metal front face?

xschop

Not unless you're going to put it in a purple Crown sack ha-ha.

lawdogg

xschop wrote: »

Not unless you're going to put it in a purple Crown sack ha-ha.

YES. DO IT!