Original Owner Of Monitor 5JR Plus

Gardenstater

https://www.youtube.com/watch?v=AqSDQ5mR1gU

melchionda

They're done! :-)

And they sound f$%ing amazing! Super crystal clear and detailed. Voices are really jumping out of these speakers now. Exactly what I wanted. Its been several months since I heard them pre-mods and so comparing SPL to now vs then is hard, however they don't seem deficient compared to my other speakers. Only two issues. I need oval head black oxide screws for the tweeters and I cant find them anywhere in a quantity of less than a couple hundred so I might have to use regular pan head screws and with the new tweeter plate the grill doesn't fit, so I'll need to modify the grill frame a little bit.

Here are the final pics. They actually look better in real life. The walnut is darker in real-life and the black color of the speaker drivers and tweeter has a softness to it that you cant see in the pics.





On the back you can see I re-applied the Polk Audio product sticker... thought about putting it back in the original location in the upper right corner but instead opted to put it near the binding posts. The binding posts are GR Research Tube Connectors.



I'm glad I did this project. Even though I've had these speaker for a really long time I was never really satisfied with them. Not enough clarity or imaging. These mods really helped to address that, plus the walnut veneer is a nice change after 30 years of the black vinyl veneer. Also I think that the combo of the black drivers set into the walnut baffle looks fantastic.

This has been a long journey, I started this back in March and back then my plan was just to improve the drivers with dynamat. Thanks to everyone who offered advice and guidance on this project! Special thanks to Xschop for firing up his lathe to make me some awesome tweeter plates and waveguides! They defintely take these speakers to the next level!

melchionda

I just tried to do my final update but it disappeared! Ugh! Anyway, here is attempt number 2. Shorter because I dont feel like re-typing everything!

The speakers are done and they sound fantastic! Dramatic improvement over the pre-mod performance.






I'd love to find some Oval head 1.25" 8-32 machine screws in black oxide for the tweeter plates.

Thanks to everyone that offered advice and guidance; its been a long journey! Special thanks to Xschop for firing up his lathe to make me some tweeter plates and wave guides! They really took this to the next level!

xschop

Those are gorgeous. The plates are designed to take 8-32 flat heads with an 82° head.

Let us know how they meld with your subwoofers.

Polk should take note of the aesthetics here too, if they revamped their vintage era.

melchionda

xschop wrote: »

Those are gorgeous. The plates are designed to take 8-32 flat heads with an 82° head.

Let us know how they meld with your subwoofers.

I was hoping for oval head screws so that they would match the screws I used in the woofer and PR

The speakers meld with the subwoofer pretty nicely. They do a better job than the warfedales because I think the polks have more range. I have DSP on the subwoofer amps so I’ve programmed in some curves to help that along.

plastic_avatar

Gorgeous. Really. Just gorgeous.

Gardenstater

Flush is mo better for tweeter plates to avoid reflections. I came across these flat head phillips screws on ebay to unify your look:

https://www.ebay.com/itm/224997962535

How are they sounding after a few days? I bet you are hearing more clarity in vocals and better perceiving words of songs you thought you were familiar with previously?

melchionda

Thanks for the link.

Yes, the sound is way more clear. I am definitely hearing more clarity. Last night while listening to a broad range of music I noticed that one song that previously sounded sonically "mashed up" now sounded more like a conglomeration of many distinct sounds all coming together. Really amazing. I can't remember exactly what I was listening to when I noticed that detail, but it was definitely there. Supposedly the crossover components will take a bunch of time to break in, so it should get even better. I'm also really enjoying the look of these. The walnut veneer has visual depth, the polyurethane feels wonderful to the touch, and the tweeter plate looks really substantial. All of these details come together to give the speaker a much more high-end look vs their original look. Its a little frustrating that I left the end-grain exposed, but that was due to a change in plans mid-project and I wasnt going to go back and fix it. this project took a long time.

MrGeology

melchionda wrote: »

They're done! :-)

Those look beautiful. Very nice work indeed!

xschop

plastic_avatar wrote: »

Ohhhhh... gasket pornn!

Tearing that one off soon...Think I finally found what Im looking for.
Tight weave aramid fiber bonded butyl rubber...0.050" total thickness...
Doesn't deform or puncture unevenly.

melchionda

Hey @xschop. What is the black stuff on the baskets? I’m guessing it’s some sort of damping material.

xschop

This was the flimsy frame from the odd-ball 6502 Mr Geology sent. I was testing for stiffening and dampening using a 1-piece fiberglass sheet sandwiched between 2 layers of polyurethane. Can't say much for stiffening, but damping is the beezness...

Found this pic before 2nd layer...

StantonZ

Those cabinets do look nice! Makes me want to do it...but I'm not "handy" that way. The XO's are definitely worth it. I see we share the same taste in AVRs/Receivers...

melchionda

StantonZ wrote: »

Those cabinets do look nice! Makes me want to do it...but I'm not "handy" that way. The XO's are definitely worth it. I see we share the same taste in AVRs/Receivers...

Actually, we both have the same TV also! :-).

melchionda

I'm still evaluating these speaker mods and I have a question. If I removed the Polyfill (the white stuff) from the inside of the speaker what impact should it have on the sound? Also, I noticed that when I took the speaker apart it was stuffed into the upper portion of the cabinet behind the tweeter and the bottom of the cabinet was open. Is this consistent with what you folks are seeing?

Gardenstater

One thing I do know is that polyfill effectively increases the enclosure size by reducing the speed of propogation of a sound wave through it. That effects the design parameter target of Vas. Also, it reduces standing waves which will improve sound quality by reducing their negative effects on the back of the cone of the midwoofer and the resulting transmission through the cone. My 7Bs came from factory with the polyfill only in the upper part, behind the tweeter and the midwoofer.

xschop

Yank it and have a listen.

F1nut

Leave it where it is.

pitdogg2

xschop wrote: »

Yank it and have a listen.

Are you still talking about polyfil ?

xschop

^^^ Good one^^^

I don't believe it would affect the low frequencies more than what's been done to the interior walls already.

As far as mids, they should be the cleanest sounding, as all rear cone reflections have already been mitigated by the inner frame foam mods also.

Mock away, but pure physics dictates that the foam on inner frames is the first line of defense against rear cone reflections.

Gardenstater

One thing I'll add is that No Rez is different from Blackhole5 in the respect that it does not have the polymer (vinyl?) barrier that is sandwiched by the relatively small thickness of closed cell foam beneath it and the relatively larger thickness of open cell foam above it. Danny Ritchie states that he believes that is undesirable in a loudspeaker because it can actually mass load the speaker diaphragms dynamically. BH5 claims that it makes their product neutral with respect to enclosure volume because the volume of displacement of everything beneath and including the vinyl layer compensates for the open cell foam's effect of increasing the effective enclosure volume.

The No Rez and the polyfill together would increase the effective enclosure volume more than the No Rez alone.

odcics2

It would be interesting to hear how much better a 6.5" Polk mid-woofer would sound
if redesigned like an old Henry Kloss designed KLH woofer...

Gardenstater

Cool but I don't care much for the use of particle board. Maybe it was a mockup?

odcics2

Not a prototype, but a real production piece from 1958.
MDF was introduced in 1966.
Plywood would have been a second choice.

The Kloss design surely gets rid of any basket related reflections!

Only issue would be magnet reflections.

Gardenstater

It almost looks like it was permanently/integrally attached to the baffle and somebody cut it out with a jigsaw

melchionda

I asked the question because when I put these speakers back together I forgot to put the polyfill back in! Unfortunately i can't do a before and after comparison because while I was putting the polyfill back into the speakers yesterday I had two new livingroom couches delivered. The couches have dramatically changed the acoustic characteristics of the room.
I will say that Danny told me to put the polyfill back into a pair of Warfedale Diamond 9.1 speakers that I upgraded using one of his kits, that kit included No-Rez for the Warfedales. Danny is is really proud of that kit claiming that it dramatically improves the speaker because the speaker already has good drivers and cabinet but suffers from a poor crossover and no cabinet damping. After doing the Warfedale upgrade they do sound much better.
But back to the Polks. In comparison to the Warfedales the Polks have a "fuller" sound. So far the new SL2500 tweeter sounds a bit harsh. I didnt hear that harshness right away but seems to have popped up after a few hours of listening. Is this an artifact of the tweeter and new crossover parts breaking in?

odcics2

Gardenstater wrote: »

It almost looks like it was permanently/integrally attached to the baffle and somebody cut it out with a jigsaw

That’s how they were built!!!
Yes, to sell it, it was cut out of the cabinet!!’

Gardenstater

melchionda wrote: »

I asked the question because when I put these speakers back together I forgot to put the polyfill back in! Unfortunately i can't do a before and after comparison because while I was putting the polyfill back into the speakers yesterday I had two new livingroom couches delivered. The couches have dramatically changed the acoustic characteristics of the room.
I will say that Danny told me to put the polyfill back into a pair of Warfedale Diamond 9.1 speakers that I upgraded using one of his kits, that kit included No-Rez for the Warfedales. Danny is is really proud of that kit claiming that it dramatically improves the speaker because the speaker already has good drivers and cabinet but suffers from a poor crossover and no cabinet damping. After doing the Warfedale upgrade they do sound much better.
But back to the Polks. In comparison to the Warfedales the Polks have a "fuller" sound. So far the new SL2500 tweeter sounds a bit harsh. I didnt hear that harshness right away but seems to have popped up after a few hours of listening. Is this an artifact of the tweeter and new crossover parts breaking in?

I forget how it came to pass that you got a "new" pair of SL2500 tweeters. I am sure they aren't making them anymore. Were they NOS? If those are ferrofluid tweeters I wonder if the ferrofluid can dry up over time.

xschop

Those billet plates ONLY bolt up to RD-0194's or RD-0198's.

melchionda

Its an RD0198-1 but the place that I bought it from refers to it as the SL2500 also. I find it easier to remember. The crossover I built (using new components) for these speakers is the same specs as the one that was used on the Monitor 5Jr+ (rev 2). And that version used the SL2500 Tweeter.