Westmassguy's Idea: Employing Damping to Mitigate Comb Filtering and Lobing
Comments
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Stogie: That is indeed the 1 1/4 Sonic Barrier - the thickest version. I had almost enough from one sheet to do my cabinets, which are larger than 10's, so one sheet may be enough for you.
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One more thing to add to this discussion... If you do Dave's mod as described above be prepared to experiment with the placement of your speakers, specifically the toe-in. The original Polk instructions recommending quite a bit of toe-in (which I applied to some degree in my room) don't seem to apply any more. I've settled on very little toe-in which now produces the largest, clearest soundstage I have ever heard them produce.
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I got a board and cut it for my 10's to expand the center divider board all the wall to the top and have one speaker finish except for the Sonic-barrier which says monday now for delivery. Have not started no#2 yet.
will report back when finished!2 ch- Polk CRS+ * Vincent SA-31MK Preamp * Vincent Sp-331 Amp * Marantz SA8005 SACD * Project Xperience Classic TT * Sumiko Blue Point #2 MC cartridge
HT - Polk 703's * NAD T-758 * Adcom 5503 * Oppo 103 * Samsung 60" series 8 LCD -
Get'r Done! SlackerI got a board and cut it for my 10's to expand the center divider board all the wall to the top and have one speaker finish except for the Sonic-barrier which says monday now for delivery. Have not started no#2 yet.
will report back when finished!
Home Theater/2 Channel:
Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
dhsspeakerservice.com/ -
@voltz When you expanded the center divider to the top, how did you get around the tweeter centered above the two MW's? Any pictures? thanks, donSpeakers: Polk SDA-SRS xovers rebuilt by David, RDO194's, Dynamat, BH5, glued magnets, new cloth, custom aluminum terminal plates with Cardas posts and Speakon interconnect
Speaker Cables, Jumpers & Interconnect: DIY Douglas Connection
Power Amp: Sunfire Architect's Choice Series II
Preamp: Adcom GFP-750
SACD/CD: Oppo BDP-95
Tuner: Sansui TU-717
TT: Technics SL-MA1
Phono Pre: Emotiva XPS-1
Music Server: Mac Mini w/JRiver - iPad w/JRemote
DAC: Eastern Electric MiniMax Plus
Other Polks: SDA: 1A, 1C, 2B, CRS+ / Monitor: 10A, 5jr, 4 / RT5 -
After it was cut to size and while I was test fitting it, I just mark it with a pencil thru the tweeter hole. then clamp it to my portable table and used a jig saw.
only took about a 3/8 deep cut.
2 ch- Polk CRS+ * Vincent SA-31MK Preamp * Vincent Sp-331 Amp * Marantz SA8005 SACD * Project Xperience Classic TT * Sumiko Blue Point #2 MC cartridge
HT - Polk 703's * NAD T-758 * Adcom 5503 * Oppo 103 * Samsung 60" series 8 LCD -
Great thread! How did the M10 mod turn out?
Edit - I see voltz hasn't been around in quite a while.
Really impressive RTA12 mod. These are the speakers I lusted after circa 1979 when all I could afford were my 7Bs!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 -
I had great success with this. I really appreciate Dave thinking out of the box on this one and taking the time and effort to help me because it opened up the door for these speakers to perform at a much higher level. One wrinkle I had to work out was the polyfill. When my speakers were built someone stuffed them with so much polyfill that I could not physically get it all up above the PR area. I spent a while listening until I settled on a "just enough" amount to get correct sounding bass. I also fabricated a tweeter diffraction ramp/device much like the 12B/12C (but with a slightly larger footprint) from dynamatted aluminum that was another huge leap forward. The fuses have also been deleted (my amps run at 800 wpc so no danger of clipping). These speakers are now very detailed and are capable of some really "spooky" imaging. Sometimes I play a particularly nice recording and shake my head at how good some 42 year old Polks can sound.
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Polk Folks:
I have a pair of 1980 vintage RTA-12's that I have been modding for months.
Forgive me, but that sounds like the introduction to a 12 step program.....
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More pics please?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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🤯 I am going to have to really consider this one… the Monitor 11’s I have would benefit from this. I was considering keeping all mods reversible and I like them how they are but… like I said in another thread, I am enjoying the rabbit hole. The biggest downside is that BH5 is pricey!
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You might want to try Sonic Barrier from Parts Express. Some say it works about as well as BH5.
Sonic Barrier from Parts Express 1 1/4" thick sheet 18x24 $29.98 -
The Sonic Barrier works quite well. No, it's not Black Hole 5, but for the price, it's well worth it. As mentioned, purchase the 1 1/4"Home Theater/2 Channel:
Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
dhsspeakerservice.com/ -
I've been reading up on this tonight. Great work, guys. Wow.
If I tried this on my Monitor 12:
- it's an extension to the top and to the bottom of the lower mids
- 1.25in Sonic Barrier on the top, back, and sides of the outer mw chambers
- no poly in the outer chamber, but original poly in the inner chamber?The Thrifty Setups in Mah House Big thrifty stereo in the basement w/ my custom SDA-1C (built with help from kind forum members) * Beautiful 1966 MCM GE console upgraded w/ Bluetooth, Dual turntable, and Paradigm speakers in family room * Swanky 1980 Realistic system and great TEAC eq with dancing colored lights in the living room * custom 5B on a system for my Dad * Ye Olde college stereo in the garage -
plastic_avatar wrote: »I've been reading up on this tonight. Great work, guys. Wow.
If I tried this on my Monitor 12:
- it's an extension to the top and to the bottom of the lower mids
- 1.25in Sonic Barrier on the top, back, and sides of the outer mw chambers
- no poly in the outer chamber, but original poly in the inner chamber?
Sounds about right
Jazzhead's photos
Home Theater/2 Channel:
Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
dhsspeakerservice.com/ -
plastic_avatar wrote: »
- no poly in the outer chamber, but original poly in the inner chamber?
@westmassguy answered this question earlier in this thread. Is that still the preferred method Dave?
"lawdogg wrote: »
» show previous quotes
Thanks - and polyfill, cut it in half and stuff it like normal but just in 2 pieces?
westmassguy wrote:
Divvy up what batting you have equally between each side, behind the woofers".
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plastic_avatar wrote: »
- no poly in the outer chamber, but original poly in the inner chamber?
@westmassguy answered this question earlier in this thread. Is that still the preferred method Dave?
"lawdogg wrote: »
» show previous quotes
Thanks - and polyfill, cut it in half and stuff it like normal but just in 2 pieces?
westmassguy wrote:
Divvy up what batting you have equally between each side, behind the woofers".
Unless @Jazzhead modified it, no batting in the lined sideHome Theater/2 Channel:
Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
dhsspeakerservice.com/ -
It comes down to where the polyfill will fit without over-compressing it. If you compress it against the entire back of the midwoofers and don't leave a window with both drivers for air/soundwaves to access the PR you'll lose slam, bass, kill the life (@westmassguy knows I learned the hard way, lol) I have little in the damped side, because there wasn't much room left. Different speaker models will have different amounts of room left. There's a reason the Polk engineers chose a given amount so I'd try to stay with the original amount as much as possible. You don't want it below the midwoofers, however. My stock speakers had it stuffed up top, and a large amount down in the PR area (Polk employee error?). I was forced to remove some, but currently have the best bass they've ever produced.
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I just finished doing this to my Monitor 10's and I can echo everything that @Jazzhead has said. Definitely improved everything about these speakers. Thank you @westmassguy for the advice! I have these and also a pair of 7b's in a small vintage setup and I rarely used these because the 7's just sounded so much better. I still prefer the 7's but it's MUCH closer now! To be honest, the room is very small and the placement of the 10's is not ideal. Maybe I should loose the Kabuki speakers or at least swap positions with the 10's.
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Put them on the Kabuki stands and try them there, off the floor.
Got the Peerless, too? Nice
Nice stack, too, btw!
I have a little Technics of my Dad's on the fix-it-up stack here...
The Thrifty Setups in Mah House Big thrifty stereo in the basement w/ my custom SDA-1C (built with help from kind forum members) * Beautiful 1966 MCM GE console upgraded w/ Bluetooth, Dual turntable, and Paradigm speakers in family room * Swanky 1980 Realistic system and great TEAC eq with dancing colored lights in the living room * custom 5B on a system for my Dad * Ye Olde college stereo in the garage -
Westmass,
Has this been tried on the SDA SRS’s? -
@joebass3 It's good to finally get actual feedback from someone with 10's (several expressed interest, but we never heard back). How's the bottom end? They should be imaging better (try them out away from the walls for kicks), and perhaps the presentation is less mid-range shouty? Also, they should play louder without losing composure as quickly. This @westmassguy mod is genius, as it potentially can improve more than one shortcoming on the older models with both drivers operating at identical frequencies. IMHO this mod is fundamental for anyone with these older model speakers that is modding for maximum performance.
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@joebass3 It's good to finally get actual feedback from someone with 10's (several expressed interest, but we never heard back). How's the bottom end? They should be imaging better (try them out away from the walls for kicks), and perhaps the presentation is less mid-range shouty? Also, they should play louder without losing composure as quickly. This @westmassguy mod is genius, as it potentially can improve more than one shortcoming on the older models with both drivers operating at identical frequencies. IMHO this mod is fundamental for anyone with these older model speakers that is modding for maximum performance.
The bass is less boomy but just not tight like the 7's. I'll put them on the stands, play around positioning and see if they improve. Imaging is hugely improved and not shouty like before. Overall I'm thrilled with the transformation! I guess now I should just finish the job and rebuild the x-overs. -
Giving them some air (away from walls/corners) will help you assess the bass. My recollection is 10's sound inherently bass heavy relative to 7's anyway. The bass/midrange should also sound tighter due to that brace stopping vibration at the PR/midwoofer intersection. Have you installed rings or hurricane nuts (rings are best) as that will further tighten bass, and increase slam. Yes, splurge and do the crossovers. Do you have the stock binding posts (you may have posted this elsewhere - sorry)? Replacing them is an audible improvement (I'm gonna empty your wallet, lol).
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Bass heavy explains what I am experiencing. Its possible that the slam i get with the 7's can't be duplicated with the 10's. I used hurricane nuts for the 10's but did some serious bracing and semi rings for the 7's.
https://forum.polkaudio.com/discussion/197673/monitor-7-baffle-strengthening#latest
I'm sure those two mods really helped with the slam I get with the 7's. Maybe when I pull the x-overs I'll experiment with bracing at the same time. -
At this point with the newly extended brace you are probably good. You'll know more after you reposition and listen some. Glad you are getting positive results. Some of this bass business is amplification/cable related. My 12's crave current - the more they got, the tighter they sounded. 10's may be different.
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The 10's would benefit from a front to back brace above the 10 and 2 o'clock PR fasteners.Don't take experimental gene therapies from known eugenicists.
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Some pics...
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Excellent. I'd dampen that last part behind the tweeter area as well (second photo from the top one). Get every surface.
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After doing this mod, these speakers sound amazing. Big and wide soundstage! Just wish the bass was tighter. Is being bass heavy just the nature of the beast for the Monitor 10 or is there anything that can be done to bring down the bass response between 70hz-120hz to keep it in line with the rest? You can see in the graphs that there is a jump (red line is peak response) in the 10's that is not there in the 7b's. Either way, I'm enjoying these so much more since doing the mod!
