Bad SDA box design?
nhhiep
Posts: 877
Anyone know why Polk designed to have ALL drivers in SDA speakers share the same internal volume instead of isolate them? For example in the Left speaker, drivers with the right signal will also move air inside the SAME box? would it better if they're in their own box inside the tower?
Post edited by nhhiep on
Comments
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That's an interesting question. Although I would like to know if separating the dimensional array from the stereo array would make the PR perform better.design is where science and art break even.
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Since the dimensional drivers operate in phase with the strereo drivers below about 100 hz ish all their back waves couple to the same box volume and PR.Isolating the dimensional drivers into their own enclosed volume would result in their bass extension not being assisted by the PR.
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what about 100hz and up? to me, it sounds like the Dimensional drivers are fighting with the stereo.
I just don't understand why even my Rti12 speakers(not Polk's top of the line) have separate enclosures within. -
Not really since above 100hz the dimensional drivers are only reproducing the R-L L-R difference signal,not the same signal as the stereo drivers.what about 100hz and up? to me, it sounds like the Dimensional drivers are fighting with the stereo. -
I'm not familiar with it's internal construction but I assume since it appears to have dedicated midrange drivers they have been placed in separate enclosure to isolate them from the woofers back wave.In the SDA all the drivers are reproducing bass,thus no dedicated midrange's.
I just don't understand why even my Rti12 speakers(not Polk's top of the line) have separate enclosures within. -
yeah, that is my question. all drivers are making bass in the same box; mixing bass from opposite signal.In the SDA all the drivers are reproducing bass.
I know why the Rti12s have separate box. I just use it as an example why Polk went extra way to do it on the Rti, but not in the SDA. it is not like $ was an issue. -
To clarify below 100hz the dim drivers are in phase with and share the same stereo bass signal as the stereo drivers.Above that point they are handling different signals.yeah, that is my question. all drivers are making bass in the same box; mixing bass from opposite signal. -
Bass reasons aside, by separating the drivers and giving each set their own PR, it may add to coherence. As long as bass tuning was the same, the low end shouldn't be affected."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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Agreed but I assume the added complexity vs any performance gain was considered cost prohibitive?Bass reasons aside, by separating the drivers and giving each set their own PR, it may add to coherence. As long as bass tuning was the same, the low end shouldn't be affected. -
A little off the subject but I put a little BlackHole5 behind the tweeters and have had great results, I assume it is due to eliminating some of the internal waves against the back of the tweeters.
I also added three cross braces in the cabinet made of 1-1/4 oak round also with great results. I know some say it is tampering with the design that Polk intended but I have no regrets in doing it.. -
The back panel behind the tweeter or on it's magnet assembly?Flame suit on :evil:IMO there is a lot of unbraced panel area in SDA's that could benifit from the addition of some well placed bracing.
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several high end brands use this style of cabinet. The OP is making this more complicated than it actually is from a speaker design standpoint. There are always gives and takes in any design and all things must be considered when making those decisions. Consider an open baffle design. All drivers then share the same space. However the space does not load the drivers. If the cabinet in the SDA's were small enough to actually load the drivers in the frequency range in question it may cause issues that would be strong enough to consider. However, consider thew size of the cabinets as compared to the actual driver displacement in the frequency range in question (above 100hz). The amount of air displaced is negligible, even at relatively high volume levels. Long excursions only occur in the range that all drivers operate in and therefore only then are the drivers loaded by the cabinet. However, separating the drivers and therefore giving them separate passives would create a subtle issue with phasing of the passives along with the extra detail of tuning the additional passives. Think of the Monitor 10 and 12 mid phasing issue (due to the side by side spacing of the mids) on a bass level. Not as noticeable but still an issue. Also for the frequencies that the drivers are operating in; the higher the frequency, the more easily its back wave is absorbed or slowed by stuffing inside the cabinet.
I see the point the OP is making and though it is valid, I see it as negligible in this situation. I have posted before, i am not a huge fan of the cabinets construction of these speakers and believe the construction quality could have been better. But that is a different reasoning all together. from a design standpoint the SRS versions progressed as the models progressed. Still sacrifices were made in some areas to gain in others. This is why some owners make some mods to their cabinets as described by Toolfan.If con is the opposite of pro, is Congress the opposite of Progress?!
Monitor 5Jr, Monitor 5, RTA12, RTA 15TL, SDA 2A, 1c, SRS 2, 1.2TL, CRS, Atrium. -
I agree.Agreed but I assume the added complexity vs any performance gain was considered cost prohibitive?
I believe he means on the inner back wall of the cabinet...I hope.The back panel behind the tweeter or on it's magnet assembly?Flame suit on :evil:IMO there is a lot of unbraced panel area in SDA's that could benifit from the addition of some well placed bracing.
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
I forgot to mention that the principals discussed here are exactly the reason some find the smaller simpler versions more to their liking. I myself prefer the 2A's i have over the other models I own and have heard. I have not heard all SDA version however.If con is the opposite of pro, is Congress the opposite of Progress?!
Monitor 5Jr, Monitor 5, RTA12, RTA 15TL, SDA 2A, 1c, SRS 2, 1.2TL, CRS, Atrium. -
Yes on the inner back wall of the cabinet!!! Give me some credit fellas..:cheesygrin:
I wouldn't stick anything on the magnet... -
Sorry it's my lack of comprehension skills.However since the tweeeter is completely sealed I would'nt expect it be affected by back waves assuming it properly affixed to the front baffle,or am I still missing your point?:cheesygrin:.Yes on the inner back wall of the cabinet!!! Give me some credit fellas..:cheesygrin:
I wouldn't stick anything on the magnet... -
yeah, that is my question. all drivers are making bass in the same box; mixing bass from opposite signal..
I think you figured out how SDA works.>
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>This message has been scanned by the NSA and found to be free of harmful intent.< -
Sorry it's my lack of comprehension skills.However since the tweeeter is completely sealed I would'nt expect it be affected by back waves assuming it properly affixed to the front baffle.
Maybe it's just from a combination with the BlackHole 5 on the back wall as well?? They sound very well tuned... -
A little off the subject but I put a little BlackHole5 behind the tweeters and have had great results, I assume it is due to eliminating some of the internal waves against the back of the tweeters.
I also added three cross braces in the cabinet made of 1-1/4 oak round also with great results. I know some say it is tampering with the design that Polk intended but I have no regrets in doing it..The back panel behind the tweeter or on it's magnet assembly?Flame suit on :evil:IMO there is a lot of unbraced panel area in SDA's that could benifit from the addition of some well placed bracing.
Both quotes above describe some of my personal dislike for these cabinets (SRS, 1.2, 1.2TL). For best operation of the passive, the cabinet should be completely open on the inside so the standing waves can effect the passive to a greater extenet. Naturally the cabinet must be designed to achieve the standing waves that are desired for proper effectiveness. By the same token, the cabinet must be extremely rigid so as not to introduce any resonance waves of it's own. The original SRS's were very rigid due to the internal bracing but were not open internally and the passives suffer somewhat as compared to the 1.2's and 1.2TL's. But the latter versions though open, are not nearly as rigid, allowing additional resonances from the cabinet. This was addressed somewhat by the grooving of the cabinet panels internally to break up waves in the panels themselves, but his only made the cabinets less rigid. This design would be closer to optimal with much thicker cabinet walls and a completely open internal volume (except for absorbent damping material behind the drivers). But imagine how heavy these would have been and the cost to have shipped them even during production years. It all goes back to the give and take.If con is the opposite of pro, is Congress the opposite of Progress?!
Monitor 5Jr, Monitor 5, RTA12, RTA 15TL, SDA 2A, 1c, SRS 2, 1.2TL, CRS, Atrium. -
yeah, that is my question. all drivers are making bass in the same box; mixing bass from opposite signal.
They aren't mixing bass from the opposite channel because from about 100Hz to a certain cutoff (very narrow band) they are out of phase and play at a much lower level. I suggest if you want answers to your questions from the horses mouth find and read the ORIGINAL SDA white paper published in audio magazine or check our archives as both Matt Polk and Stu Lumsden have addressed this topic before in detail in a thread or two.
H9"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
I would certainly expect some improvements in the midband with the black holes reduction of internal reflections.Maybe it's just from a combination with the BlackHole 5 on the back wall as well?? They sound very well tuned... -
One of the reasons I went with a round was to not introduce any more flat surfaces in the cabinet my thought was the air could move over a rounded surface better then a flat surface, you get the picture...
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I would certainly expect some improvements in the midband with the black holes reduction of internal reflections.
It's night and day but you have to watch how much you put in, too much and you kill it!! trust me on this as I did just that when I first used it and swore I would never try it again. Less is more sometimes and this is one of those times, but I am glad I gave it another shot as the mids are fantastic and the bass is superb!! -
Mr. Bubbles wrote: »Both quotes above describe some of my personal dislike for these cabinets (SRS, 1.2, 1.2TL). For best operation of the passive, the cabinet should be completely open on the inside so the standing waves can effect the passive to a greater extenet. Naturally the cabinet must be designed to achieve the standing waves that are desired for proper effectiveness. By the same token, the cabinet must be extremely rigid so as not to introduce any resonance waves of it's own. The original SRS's were very rigid due to the internal bracing but were not open internally and the passives suffer somewhat as compared to the 1.2's and 1.2TL's. But the latter versions though open, are not nearly as rigid, allowing additional resonances from the cabinet. This was addressed somewhat by the grooving of the cabinet panels internally to break up waves in the panels themselves, but his only made the cabinets less rigid. This design would be closer to optimal with much thicker cabinet walls and a completely open internal volume (except for absorbent damping material behind the drivers). But imagine how heavy these would have been and the cost to have shipped them even during production years. It all goes back to the give and take.
That's not correct. The SRS cabinet is not as rigid as the 1.2/1.2TL and the bass repsonse from the SRS is sloppy by comparison.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
My SDA 1's don't share the same internal volume for all the driver's? The tweeter & midrange and SDA tweet & SDA mid have their own ported enclosures.Sony Tport>Illuminati D-60>Audio Alchemy DTI-Pro>Prophecy Cryo-Silver Reference i2s>Audio Alchemy DDE 3.0 w/remote wand>Kimber Select 1030>Decware Zen Select Amp (SE84CS)>Kimber Select 3033> SDA 1/in Stereo only
Sony Tport>IllumD-60>AA DTI Pro 32>AudMagicMysticRef i2s>AA DDE 3.0> Kimber Hero Int>Rotel RA-1062>Kimber Timbre>EmotivaXPA2>Kimber 8TC Speaker Cable>SDA SRS 1.2/use SDA always>Kimber 9033 to/hi Pass jumpers> Kimber PK10 Palladian Power Cord to Rotel -
stone of tone wrote: »My SDA 1's don't share the same internal volume for all the driver's? The tweeter & midrange and SDA tweet & SDA mid have their own ported enclosures.
A design that Polk quickly dropped.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
I completely disagree with this. I own both the SRS and the 1.2TL and the latter version does NOT have a more rigid cabinet. In fact it has less bracing than the SRS. It does have grooves cut into the panel boards internally to break up panel resonance. It is the more open cabinet in the latter version that helps the bass response.That's not correct. The SRS cabinet is not as rigid as the 1.2/1.2TL and the bass repsonse from the SRS is sloppy by comparison.If con is the opposite of pro, is Congress the opposite of Progress?!
Monitor 5Jr, Monitor 5, RTA12, RTA 15TL, SDA 2A, 1c, SRS 2, 1.2TL, CRS, Atrium. -
The 3.1 is big favorite around here and has a lot of internal bracing compared to most..
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I would love to try one of the smaller versions as I mentioned earlier. I am a big proponent of simplicity and the fewer drivers/ crossover components would seemingly make a much more pleasurable speaker. This is just my personal opinion and taste. I have not heard these models however, and can only guess this would be the case with them. The bracing however is primarily going to effect the bottom end (though it does have some diminishing effect as freq rises). Once again I find the overall tonal quality of the 2A's the best of the models i have heard. One of the smallest and simplest SDA's. I would love to hear a nice pair of CRS/+ as well, as I have not had that pleasure either.If con is the opposite of pro, is Congress the opposite of Progress?!
Monitor 5Jr, Monitor 5, RTA12, RTA 15TL, SDA 2A, 1c, SRS 2, 1.2TL, CRS, Atrium. -
It's night and day but you have to watch how much you put in, too much and you kill it!! trust me on this as I did just that when I first used it and swore I would never try it again. Less is more sometimes and this is one of those times, but I am glad I gave it another shot as the mids are fantastic and the bass is superb!!
+1 on this. I added BH5 in 4" wide strips (not too much - not too little) on only the back wall opposite the drivers. The change in sound quality was easy to hear and all positive: smoother, clearer midrange, tighter bass.
The changes were most obvious on vocals and complex passages, but also on the tone of instruments. Much smoother, more realistic sounding. Better decay on instruments. Sounded like I had gotten a more powerful amp."Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
