RTA8 - TL mod?
Comments
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Welcome back ☺️
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Took mine home from the shop and have been trying to carefully clean off the adhesive that Polk used for the angled plate. I still believe the RD0198 throat angle/profile negates the need for the deflector plate. These are the most dynamic and accurate ones I've modified to date. Slowly but surely adhesive is coming off with 70% Etoh without affecting the finish of the baffle laminate....
Of all the vintage Polks I've had, these are the best built cabinets and finish...
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Prepping for rear mounted Power Ports...
Don't take experimental gene therapies from known eugenicists. -
Glue is dried. This time I used Liquid Nails as it cures better than Power Grab to the alum and pvc plastic. I simply used a 2" PVC coupler because I only needed an extra 2" length (3.5" long by 2.25" ID. and I can test and pull out cabinet and lathe turn 'til I like the bass tuning)
I also glued and punched out the factory rubber pad for easy access to cabinet mount screws this time. I Don't know why Polk didn't do this originally, but this added alot more mass and damping to the platform, and I don't have to peel back the pad for access...
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Is this the first time someone has retrofitted a power port? I am very curious how this works out. Back in '91 I looked at the RTA8TL and the RTA11TL. I just couldn't get past the port sound of the 8TL vs the cleanness of the PRs and went for the 11TL.Stan
Main 2ch:
Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.
HT:
Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60
Other stuff:
Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601 -
AFAIK, I haven't seen any pics or posts of anyone else having done the conversion. The bass output is a little more than a standard port and PR from previous experience, at any given volume. Also the lower freqencies are very controlled and articulate like a PR.
I'll have to make a plug 2.45" x 0.75"...
I like that polk cross-braced the cabs right under the lower MW. I didn't even use an MW backer ring here because front baffle is SOLID in this area.
I'll temporarily putty in the Power Port adapter until I'm happy with the tuning and roll the adhesive in a nice lip on final glue-in...
The factory terminal cups clear and drop in. I'll have to adjust the area on the new style billet terminal plates that encapsulate the factory cups however....
The 3" x 1" plug billets showed up as I was posting this, they'll look nicer than the socks stuffed in there now lol....
Post edited by xschop onDon't take experimental gene therapies from known eugenicists. -
Forgot to include this in my last post. This time I used double-sided sticky tape for easier removal of the port adapter. I took them down to 3.25" total length now after listening to them a couple days.
The bass impact and definition is incredible, more detailed and well-balanced. Most importantly, the midrange that was coming from the front ports is no longer smearing the sound. A major improvement for someone that would only install rear-firing standard ports...
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Looks great!- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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Interesting that the TL version had internal bracing. When I took my RTA 8t's apart there was absolutely none...Remember, when you're running from something, you're running to something...-me
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What's also interesting is the plastic ports were only 0.072" thick walls and not glued to the bottom brace. Curious if they were contributing to the unwanted "midrange" myself.Don't take experimental gene therapies from known eugenicists.
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These will look much better than the stuffed ports...
Don't take experimental gene therapies from known eugenicists. -
Setting them up for the extended weekend...
Don't take experimental gene therapies from known eugenicists. -
WOW!! They are coming along nicely.. Great job!!
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Thanks Larry. I'm tickeled by the dynamics that these small towers emanate. If I were to come across a set of 11TL's, I'd pass right now.
If I find another set of these, I'd experiment with a 10" PR. Which 10" would sound the best is anyone's guess. CRS+, Monitor 10 donors? Thats why I like the Power Ports, as they are easy (and dirt-cheap) to mod to taste.
Final OD of plug lip is 2.90" and 1/4" tall. It clears the factory grill cutout nicely.
As an aside, someone could also make 10" passives fit nicely on their sides...
Post edited by xschop onDon't take experimental gene therapies from known eugenicists. -
After a solid week of daily listening, I can report back that the seismic ball isolators deliver even more resolution across the full freq. spectrum. I'm really caught off guard by the increased definition in all string instruments that I didn't think could improve much more. Especially violins and classic upright bass. I have a go-to track by Bob James (Oliver's Bag) and Simply Red's Sad Old Red, on every mod that I do, and the improvement in bass string resolution is undeniable.
I found a good method of installation with these...
After a week of playing regularly, sometimes all day, and motioning them in their concave seats, the slight micro-polishing of the 7075 alloy by the stainless balls is taking place. Exactly as the bearing engineer that I consulted with explained...
Hopefully my kid doesn't find out the new anomoly...
https://youtube.com/shorts/TE95bIe7Rrg?feature=share
Post edited by xschop onDon't take experimental gene therapies from known eugenicists. -
Amazing huh? It was hard for me to believe at first, how much micro vibrations apparently affect the voice coil motions. I am still only using my MaGyver style soup spoon isolators that I made with epoxy putty molded bases. They aren't a uniform spherical shape so inherently inferior and yours will be so much better for top and bottom opposing cups used in pairs. I never wanted to try mine that way.
Have you tried them underneath any other components like your amplifier? Supposed to reduce the effect of microphonics and I believe it does so.
Far rear one on right has the epoxy putty.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Haven't tried them under my amp, but could see the benefit.
From what I can tell, any remaining cabinet resonance is being isolated from transmitting through the floor. I believe these 8TLs still need an internal cross-brace between top MW and tweeter to deaden the cabinets completely. With these isolators installed, the tonality changes in the mid bass freq. that would normally be heard at the highest volumes.
Whatever the exact physics involved, these are no gimmick. I've heard quite a few speakers before and after their spike isolation installs and this is a different, but welcomed animal.Don't take experimental gene therapies from known eugenicists. -
I’m a pay grade or two behind you guys.Samsung 60" UN60ES6100 LED Outlaw Audio 976 Pre/Pro Samsung BDP, Amazon Firestick, Phillips CD Changer Canare 14 ga - LCR tweeters inside*; Ctr Ch outside BJC 10 ga - LCR mids, inside* & out 8 ga Powerline: LR woofers, inside* & out *soldered LR: Tri-amped RTi A7 w/Rotels. Woofers - 980BX; Tweets & “Plugged*” Mids - 981, connected w/MP Premiere ICs Ctr Ch: Rotel RB981 -> Bi-amped CSi A6 Surrounds: Premiere ICs ->Rotel 981 -> AR 12 ga -> RTi A3. 5 Subs: Sunfire True SW Signature -> LFE & Ctr Ch; 4 Audio Pro Evidence @ the “Corners”. Power Conditioning & Distribution: 4 dedicated 20A feeds; APC H15; 5 Furman Miniport 20s *Xschop's handy work
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Haven't tried them under my amp, but could see the benefit.
From what I can tell, any remaining cabinet resonance is being isolated from transmitting through the floor. I believe these 8TLs still need an internal cross-brace between top MW and tweeter to deaden the cabinets completely. With these isolators installed, the tonality changes in the mid bass freq. that would normally be heard at the highest volumes.
Whatever the exact physics involved, these are no gimmick. I've heard quite a few speakers before and after their spike isolation installs and this is a different, but welcomed animal.
It would be a bit unstable without outriggers to widen the footprint, but if you were to also add vertical vibration isolation in the form of a set of 4 springs selected for your load to give a resonant frequency of 2 Hz or less that would be the icing on the cake. You'd probably have to add a 4th roller bearing then. I think there is enough compliance in your 3M PSA mounting discs to make that work just fine, as far as any out of planar condition would be concerned.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
To add springs, I believe an interconnected platform would be in order to stabilize the base correctly. An experiment for another day, surely.
For these 8TL's, they are surprisingly heavy for their size. When trying to tip them over by hand, the 3" cup radius does not allow them dislodge from the cups in any way. They immediately move away from the hand force, and re-stabilized by gravity from any direction.
I have material to make custom outriggers for these, but these are plenty stabil.
My next mod to these are to build an adjustable internal cross-brace to completely stiffen the full perimeter of the cabinet between top MW and tweeter. Why Polk stopped at the lower MW brace is well...anyone's guess.Don't take experimental gene therapies from known eugenicists.
