Aluminum Tweeter Face Plates For My SDA SRS 1.2TLs - Review
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DarqueKnight
Posts: 6,765
Introduction
My interest in this modification was purely mechanical. I wanted to replace the flimsy, prone-to-cracking plastic bezels with metal bezels that offered increased durability and mechanical stability. I expected some (small) degree of sound quality improvement just from the fact that more rigid face plates that would be less prone to "singing".
Audiophile Eye Candy
Figure 1. Original aluminum plates. This was too much bling for the Mysterious Monoliths.
Figure 2. Front side of black anodized tweeters.
Figure 3. Rear side of black anodized tweeters.
Figure 4. Completed tweeter assemblies for the right 1.2TL. The anodized (aluminum oxide) surface is not electrically conductive. However, I covered the tweeter leads with electrical tape anyway. I did not see any jagged-edge solder joints, or anything else that would scratch the surface...but one should not tempt fate.
I was going to use the same anodizing shop that @Toolfan66 used, but he suggested a shop that was a one hour drive from me. It turned out to be a great choice. They did a great job, were very pleasant to deal with, and I received a 24 hour turn around time and a 40% discount because they ran my small job with a larger job.
Figure 5. The backs of the metal bezels are so smooth and so flat that I decided to reuse the original gaskets...which are still in very good shape after 33 years. I initially planned to make new gaskets out of Armacell tape. I might make some new tweeter gaskets in the future...when I am more dedicated to audio than I am now.
Figure 6. Up close.
Figure 7. Angle view.
Figure 8. Full length view. The crossover plate is not purple, nor is it faded on the right side. That's just glare and shadow. The plate is silky black, as shown in figure 6.
The Sound
Listening evaluations were done pre-modification, then with just the right speaker modified, then with both speakers modified. Both of my home's air conditioning units were turned off during the listening evaluations and measurement exercises.
Four music selections were used. The Rollins selection was ripped to a DSD64 dsf digital file from the SACD. The other three selections were ripped to 44.1 FLAC files from the CDs and converted to DSD64 dsf files.
1. "You Don't Know What Love Is", Sonny Rollins, "Saxophone Colossus" SACD (Mono recording):
2. "Last Night In Los Feliz", Niia Bertino, "Niia I" CD:
3. "Healing Song", Gregg Karukas, "Heatwave" CD:
4. "Isunova Pi", E.S. Posthumus, "Cartographer" CD:
After comparing sound stage maps and listening notes from previous evaluations using these recordings, there were no apparent changes in the placement and size of images. There were big changes in definition, clarity, detail, image weight and dynamics. I particularly liked the increased definition and silkiness of saxophone reed sounds and the enhanced growl of electric and acoustic bass instruments.
With the metal tweeter plates installed on just the right speaker, there was a shift in the center image to the right. The right side also sounded louder and images had more weight and detail. This was true whether listening with the preamplifier set in mono or stereo mode.
I found that clarity, detail, image weight, and tactile sensation improved for two days after installation. Similar results were realized with previous vibration abatement devices and treatments in my stereo system.
Measurements
Room response, harmonic distortion, and bass decay measurements were taken with the Dayton Audio Omni-Mic system. Thiele/Small parameter measurements and frequency response measurements for the RD0198 tweeters were taken with the Dayton Audio DATS VS system. The Omni-Mic microphone was placed at the listening position at ear height.
The differences in the room response plots are subtle. They are more discernible if the plots are saved and viewed sequentially. Larger versions of all plots can be viewed if they are opened in a separate tab.
Figure 9. Room response with plastic tweeter bezels.
Figure 10. Room response with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 11. Room response with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
In the harmonic distortion plots, the color coded lines represent the following:
Black - Room response
Red - 2nd harmonic distortion level
Purple - 3rd harmonic distortion level
Green - 4th harmonic distortion level
Light Blue - 5th harmonic distortion level
Dark Blue - Total of the 2nd through 5th harmonic distortion levels
Figure 12. Harmonic distortion with plastic tweeter bezels.
Figure 13. Harmonic distortion with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 14. Harmonic distortion with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Bass decay plots - When a bass note is stopped within music, the sound in the room at some frequencies may still continue for some time. That is because the sound reflects back and forth between walls, resonating and forming "modes" before eventually dying down. This is not altogether bad and some reinforcement is normally desirable for natural sounding playback. However, if this is not kept under control, muddy or smeared bass can result.
The bass decay plots show how long it takes the sound to decay at each frequency. As shown on the legend to the right of the decay graph, the white area extends upward to indicate when the level drops no more than 5 decibels (dB). The light blue indicates when the level has dropped between 5dB and 10dB, The medium blue indicates when the level has dropped between 10dB and 15dB. The dark blue indicates when the level has dropped between 15dB and 20dB.
Figure 15. Bass decay with plastic tweeter bezels.
Figure 16. Bass decay with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 17. Bass decay with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
The Thiele/Small parameters and frequency response of the top two tweeters in the right speaker were measured with plastic and with metal bezels. The RD0198 tweeters are able to make Such Good Sound because all that plastic is no longer singing along with the tweeter.
The following tweeter frequency response plots correspond to trial five in each of the T/S parameter tables 1 - 4.
Figure 18. Right tweeter #1 frequency response with plastic bezel.
Figure 19. Right tweeter #1 frequency response with metal bezel.
Figure 20. Right tweeter #2 frequency response with plastic bezel.
Figure 21. Right tweeter #2 frequency response with metal bezel.
Conclusion
One of the frustrations of the engineering profession is design constraints. Excellent engineering designs are often compromised by implementation constraints due to limitations of time, money, human resources, materials, and manufacturing methods.
I concur with JayCee's idea that the metal tweeter plates are reinforcing the stabilizing effect of increased rigidity brought by @Toolfan66's rings and brackets. This modification is another that has moved the original SDA design closer to its full implementation and performance potential. Other examples are cabinet rings and brackets, the Dreadnought non-common ground interface, the TL tweeter modification for the SDA CRS+ and SDA 2B, and low DCR SDA inductors. Of course, the "gold standard", primo modification is replacing the crossovers with modern, high performance parts.
References
JayCee's Aluminum Tweeter Face Plate Review
Attachment - DarqueKnight's Audio System Equipment List
My interest in this modification was purely mechanical. I wanted to replace the flimsy, prone-to-cracking plastic bezels with metal bezels that offered increased durability and mechanical stability. I expected some (small) degree of sound quality improvement just from the fact that more rigid face plates that would be less prone to "singing".
Audiophile Eye Candy
Figure 1. Original aluminum plates. This was too much bling for the Mysterious Monoliths.
Figure 2. Front side of black anodized tweeters.
Figure 3. Rear side of black anodized tweeters.
Figure 4. Completed tweeter assemblies for the right 1.2TL. The anodized (aluminum oxide) surface is not electrically conductive. However, I covered the tweeter leads with electrical tape anyway. I did not see any jagged-edge solder joints, or anything else that would scratch the surface...but one should not tempt fate.
I was going to use the same anodizing shop that @Toolfan66 used, but he suggested a shop that was a one hour drive from me. It turned out to be a great choice. They did a great job, were very pleasant to deal with, and I received a 24 hour turn around time and a 40% discount because they ran my small job with a larger job.
Figure 5. The backs of the metal bezels are so smooth and so flat that I decided to reuse the original gaskets...which are still in very good shape after 33 years. I initially planned to make new gaskets out of Armacell tape. I might make some new tweeter gaskets in the future...when I am more dedicated to audio than I am now.
Figure 6. Up close.
Figure 7. Angle view.
Figure 8. Full length view. The crossover plate is not purple, nor is it faded on the right side. That's just glare and shadow. The plate is silky black, as shown in figure 6.
The Sound
Listening evaluations were done pre-modification, then with just the right speaker modified, then with both speakers modified. Both of my home's air conditioning units were turned off during the listening evaluations and measurement exercises.
Four music selections were used. The Rollins selection was ripped to a DSD64 dsf digital file from the SACD. The other three selections were ripped to 44.1 FLAC files from the CDs and converted to DSD64 dsf files.
1. "You Don't Know What Love Is", Sonny Rollins, "Saxophone Colossus" SACD (Mono recording):
2. "Last Night In Los Feliz", Niia Bertino, "Niia I" CD:
3. "Healing Song", Gregg Karukas, "Heatwave" CD:
4. "Isunova Pi", E.S. Posthumus, "Cartographer" CD:
After comparing sound stage maps and listening notes from previous evaluations using these recordings, there were no apparent changes in the placement and size of images. There were big changes in definition, clarity, detail, image weight and dynamics. I particularly liked the increased definition and silkiness of saxophone reed sounds and the enhanced growl of electric and acoustic bass instruments.
With the metal tweeter plates installed on just the right speaker, there was a shift in the center image to the right. The right side also sounded louder and images had more weight and detail. This was true whether listening with the preamplifier set in mono or stereo mode.
I found that clarity, detail, image weight, and tactile sensation improved for two days after installation. Similar results were realized with previous vibration abatement devices and treatments in my stereo system.
Measurements
Room response, harmonic distortion, and bass decay measurements were taken with the Dayton Audio Omni-Mic system. Thiele/Small parameter measurements and frequency response measurements for the RD0198 tweeters were taken with the Dayton Audio DATS VS system. The Omni-Mic microphone was placed at the listening position at ear height.
The differences in the room response plots are subtle. They are more discernible if the plots are saved and viewed sequentially. Larger versions of all plots can be viewed if they are opened in a separate tab.
Figure 9. Room response with plastic tweeter bezels.
Figure 10. Room response with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 11. Room response with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
In the harmonic distortion plots, the color coded lines represent the following:
Black - Room response
Red - 2nd harmonic distortion level
Purple - 3rd harmonic distortion level
Green - 4th harmonic distortion level
Light Blue - 5th harmonic distortion level
Dark Blue - Total of the 2nd through 5th harmonic distortion levels
Figure 12. Harmonic distortion with plastic tweeter bezels.
Figure 13. Harmonic distortion with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 14. Harmonic distortion with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Bass decay plots - When a bass note is stopped within music, the sound in the room at some frequencies may still continue for some time. That is because the sound reflects back and forth between walls, resonating and forming "modes" before eventually dying down. This is not altogether bad and some reinforcement is normally desirable for natural sounding playback. However, if this is not kept under control, muddy or smeared bass can result.
The bass decay plots show how long it takes the sound to decay at each frequency. As shown on the legend to the right of the decay graph, the white area extends upward to indicate when the level drops no more than 5 decibels (dB). The light blue indicates when the level has dropped between 5dB and 10dB, The medium blue indicates when the level has dropped between 10dB and 15dB. The dark blue indicates when the level has dropped between 15dB and 20dB.
Figure 15. Bass decay with plastic tweeter bezels.
Figure 16. Bass decay with right speaker's plastic tweeter bezels replaced with metal tweeter bezels.
Figure 17. Bass decay with both speaker's plastic tweeter bezels replaced with metal tweeter bezels.
The Thiele/Small parameters and frequency response of the top two tweeters in the right speaker were measured with plastic and with metal bezels. The RD0198 tweeters are able to make Such Good Sound because all that plastic is no longer singing along with the tweeter.
Table 1. Right tweeter #1 T/S parameters with plastic bezel.
Table 2. Right tweeter #1 T/S parameters with metal bezel.
Table 3. Right tweeter #2 T/S parameters with plastic bezel.
Table 4. Right tweeter #2 T/S parameters with metal bezel.
The following tweeter frequency response plots correspond to trial five in each of the T/S parameter tables 1 - 4.
Figure 18. Right tweeter #1 frequency response with plastic bezel.
Figure 19. Right tweeter #1 frequency response with metal bezel.
Figure 20. Right tweeter #2 frequency response with plastic bezel.
Figure 21. Right tweeter #2 frequency response with metal bezel.
Conclusion
One of the frustrations of the engineering profession is design constraints. Excellent engineering designs are often compromised by implementation constraints due to limitations of time, money, human resources, materials, and manufacturing methods.
I concur with JayCee's idea that the metal tweeter plates are reinforcing the stabilizing effect of increased rigidity brought by @Toolfan66's rings and brackets. This modification is another that has moved the original SDA design closer to its full implementation and performance potential. Other examples are cabinet rings and brackets, the Dreadnought non-common ground interface, the TL tweeter modification for the SDA CRS+ and SDA 2B, and low DCR SDA inductors. Of course, the "gold standard", primo modification is replacing the crossovers with modern, high performance parts.
References
JayCee's Aluminum Tweeter Face Plate Review
Attachment - DarqueKnight's Audio System Equipment List
Proud and loyal citizen of the Digital Domain and Solid State Country!
Comments
-
Great analysis.
Makes me want to change mine over in my SDA-SRS2s.
Maybe in some others as well.Most people just listen to music and watch movies. I EXPERIENCE them. -
Seems like lower harmonic distortion below 100 Hz, in the 4th and 5th harmonics. I also see much faster bass decay below 30 Hz. I think a lot of the audible and measureable differences are due to the stiffening of the baffle.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 -
"There were big changes in definition, clarity, detail, image weight and dynamics. I particularly liked the increased definition and silkiness of saxophone reed sounds and the enhanced growl of electric and acoustic bass instruments."
Is there anything else that matters?
Tom~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~ -
Thanks, Ray. As per usual, well done. Nice to see you confirmed my thoughts/impressions and presented way more data than I have the ability to provide.
Looked back at my post and it was just over a year ago that I did this. Since then, I've purchased several more sets from Rob (@xschop). He and I pm'd at the time and I expressed my hope that you'd try them, as your Good Housekeeping DK seal of approval gets folks to take notice.
Kudos, again, to Rob for his outstanding workmanship and thinking outside the box. It's amazing the talent/skills so many CP members bring to the forum, both past and present mods included.
New challenge, I'd be very interested if you'd take this one step further by getting a set of ring and tweeter felts from Trey (@vr3). Documented, elsewhere, I added them around the same time as the bezels and found them another positive refinement.➀Speakers: Polk1.2tl's (Uber Mods) ➁Pre/Amp/DAC: PS Audio BHK Signature & 250, DirectStream ➂Cables/IC's: MIT S1Bi-Wire/S1 Balanced +Avel Lindberg 1000VA "Dreadnought" ➃Power Conditioner: PS Audio P15 Power Plant ➄Power Cords: Core Power Technologies Gold, DH Labs Power Plus DIY w/Neotech NC-P301 & P311ends ➅Streaming: Roon ROCK on wifi'd NUC, TP-Link WAP, & Uptone EtherREGEN, AfterDark, Emperor Double Crown Clock, Black Modernize LPS, PS Audio AirLens⟿Ω☯☥☮⟿🔊♩♪♫♬♩♪♫♬♩♪♫♬ -
My experience? Get the tweeter bezels.
Tom~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~ -
New challenge, I'd be very interested if you'd take this one step further by getting a set of ring and tweeter felts from Trey (@vr3). Documented, elsewhere, I added them around the same time as the bezels and found them another positive refinement.
I experimented with tweeter felts in July of 2021. I liked the improvement and kept them on until I peeled them off before doing this evaluation. I plan to revisit.
Proud and loyal citizen of the Digital Domain and Solid State Country! -
Not those man. He has improved upon what you have. FWIW.
Tom~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~ -
Awe heck man....I was distracted. Sorry bro'.
Get a hold of Trey. Have him make you a bezel covering the tweeters....and if $$$ permit? The mids as well. Your ears will thank you.
Tom~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~ -
Case in point....
Tom~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~ -
Not those man. He has improved upon what you have. FWIW.
Tom
The felts shown in my photos are for prototype/proof of concept. I discussed with Trey making me some felts in black, but he said that wasn't a color option. I haven't gotten around to searching for a company that can do the precision cutting in the color option I want.
I'm glad you are enjoying what you have.
Proud and loyal citizen of the Digital Domain and Solid State Country! -
I wanted black, too, so hit them w/a light coat of spray paint. The elusive black came out rather nice.DarqueKnight wrote: »I discussed with Trey making me some felts in black, but he said that wasn't a color option.
MW's, are worth it, too.➀Speakers: Polk1.2tl's (Uber Mods) ➁Pre/Amp/DAC: PS Audio BHK Signature & 250, DirectStream ➂Cables/IC's: MIT S1Bi-Wire/S1 Balanced +Avel Lindberg 1000VA "Dreadnought" ➃Power Conditioner: PS Audio P15 Power Plant ➄Power Cords: Core Power Technologies Gold, DH Labs Power Plus DIY w/Neotech NC-P301 & P311ends ➅Streaming: Roon ROCK on wifi'd NUC, TP-Link WAP, & Uptone EtherREGEN, AfterDark, Emperor Double Crown Clock, Black Modernize LPS, PS Audio AirLens⟿Ω☯☥☮⟿🔊♩♪♫♬♩♪♫♬♩♪♫♬ -
You had me at silky saxaphone. Beautiful 1.2's you have, RayDon't take experimental gene therapies from known eugenicists.
-
Great write up Ray, my first thought while listening to Dire Straits was ‘I think Rob is on to something here’. I’m not even going to attempt to get all technical here, but you can hear a cleaner/detailed sound.
I think a lot of us were hoping you would get a set of these, and review them..
Thanks for taking the time to do this, I’m sure the interest just jumped on these.. -
My interest definitely jumped. I have pre-ordered enough plates to do the rest of my SDAs.Proud and loyal citizen of the Digital Domain and Solid State Country!
