SDA bass. How is it done?

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ROHfan
ROHfan Posts: 1,014
in Vintage Speakers
While I'm awaiting my crossover mods and upgrades from Trey I did some poking around the web to see, exactly, how the bottom end can be so strong on the SDAs when the woofer is just a passive radiator. These things have very good bass even without the IC which leads me to ponder how one 6.5" driver can produce such low end. I know it must be due to the tuning of the cabinet and such, but how is that the small driver can have that much of an effect on the radiator.
TV: 65" Samsung QLED 4K
Fronts: Energy RC70 --- Center: Energy RC-LCR
Front Heights: Polk RC65i --- Rears: Polk RC85i --- Sub: Power Sound Audio XS15
Pioneer VSX-1120K --- Parasound HCA-1000A --- Oppo BDP-103
Vincent Audio SA31 preamp --- Teac UD301 DAC
AIYIMA Tube T7 preamp --- Nobsound 12AX7 tube preamplifier
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  • boston1450
    boston1450 Posts: 7,472
    edited January 2015
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    Because they are well made Polk SDA's & Mr Polk knows his speaker :smile:
    Too many drinks
    ..
    ..
    ..
    Randy/Maine
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  • Moose68Bash
    Moose68Bash Posts: 3,842
    edited January 2015
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    It may be only a passive radiator, but it is a big, honking passive radiator! B)
    Family Room, Innuos Statement streamer (Roon Core) with Morrow Audio USB cable to McIntosh MC 2700 pre with DC2 Digital Audio Module; AQ Sky XLRs to CAT 600.2 dualmono amp, Morrow Elite Speaker Cables to NOLA Baby Grand Reference Gold 3 speakers. Power source for all components: Silver Circle Audio Pure Power One with dedicated 20 amp circuit to main panel.

    Exercise Room, Innuos Streamer via Cat 6 cable connection to PS Audio PerfectWave MkII DAC w/Bridge II, AQ King Cobra RCAs to Perreaux PMF3150 amp (fully restored and upgraded by Jeffrey Jackson, Precision Audio Labs), Supra Rondo 4x2.5 Speaker Cables to SDA 1Cs (Vr3 Mods Xovers and other mods.), Dreadnaught with Supra Rondo 4x2.5 interconnect cables by Vr3 Mods. Power for each component from dedicated 20 amp circuit to main panel, except Innuos Statement powered from Silver Circle Audio Pure Power One.

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  • Schurkey
    Schurkey Posts: 2,100
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    ROHfan wrote: »
    These things have very good bass even without the IC
    Does the interconnect cable--on ANY generation of SDA--actually affect the deep bass?

    I'm thinking that the SDA connection is rolled-off starting at 100Hz, so bass due to the cable isn't really part of the SDA driver's job. Bass due to the SDA driver of the newest three generations of SDA being driven by the stereo signal at low frequency would affect bass, but that's not the same as when powered by the SDA interconnect.

    In short, an SDA 2A or 2B, or the newer SDA-CRS may only have one stereo driver, but they still have two bass drivers because the SDA driver is doing double-duty.
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  • SCompRacer
    SCompRacer Posts: 8,352
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    Basically, bass drivers will roll off early in a sealed cabinet. You could add ports, but then you can get port noise, or chuffing. To prevent chuffing, you can use large diameter ports. To maintain cabinet tuning, the length of the ports can be quite long. Folding a long port can add to an even larger cabinet size.

    Enter the passive radiator. Passives work like a port with no noise and complicated port folding. My speakers with dual 8" woofers have one 12" passive radiator on each side.

    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
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  • westmassguy
    westmassguy Posts: 6,850
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    I'll add to what SCompRacer spoke about. From what I've read, Polk's design goal was a loudspeaker that produced deep bass, with low distortion, and was very fast and accurate (tight). Large woofers have higher mass. When given the same signal, a small woofer will react faster. The cone will start to move and cease to move faster than a larger heavier cone will. I'm over-simplifying here, as there are many other factors in play.
    When combining multiple small woofers in a common cabinet, they become acoustically coupled. In other words, when multiple smaller woofers are receiving the same signal, their combined cone area is equivalent to a much larger woofer.
    With the 3rd through 5th generation SDAs, the Stereo and Dimensional woofers are fed the same signal below 150Hz. They are acoustically coupled with each other, and fluid coupled (air being the fluid) to the Passive Radiators. The Passive Radiators kick in at around 50Hz, and their output increases as the frequency drops.
    That's why the big SRSs, with their large passive radiators, can produce frequencies down to 20Hz and below.
    Polk's woofers are also very unique. Their published T/S Parameters are amazing compared to most 6.5" drivers. Their cones are very light, suspensions very relaxed, cone travel is high, resonance frequencies very low, and VAS or how much air the drivers are able to move is also very high. Lastly, the frequency range covered by the drivers is also very wide.
    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/
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  • ROHfan
    ROHfan Posts: 1,014
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    Very interesting. Thanks for the replies.

    I've not seen any other speaker brands employing the passive radiator, although I'm sure they must exist. I'm wondering how the accuracy of lower frequencies compare to the SDAs.
    TV: 65" Samsung QLED 4K
    Fronts: Energy RC70 --- Center: Energy RC-LCR
    Front Heights: Polk RC65i --- Rears: Polk RC85i --- Sub: Power Sound Audio XS15
    Pioneer VSX-1120K --- Parasound HCA-1000A --- Oppo BDP-103
    Vincent Audio SA31 preamp --- Teac UD301 DAC
    AIYIMA Tube T7 preamp --- Nobsound 12AX7 tube preamplifier
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  • westmassguy
    westmassguy Posts: 6,850
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    ESS comes to mind
    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/
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  • Mystery
    Mystery Posts: 2,546
    edited January 2015
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    Many use pr.
    Infinity rs series, epi, harms labs etc... and lot of subwoofers.

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
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  • westmassguy
    westmassguy Posts: 6,850
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    DSkip, Passive Radiator Designs are considered Bass Reflex, not Acoustic Suspension.
    AS designs are sealed, and the air acts as a spring damping the cone. PR Designs are similar to Bass Reflex. They must be tuned, because the Mass of the PR acts the same as the Mass of the air in a Port. The benefit, is zero port noise.
    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/
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  • Conradicles
    Conradicles Posts: 6,041
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    Brian Cheney of VMPS was also a master with passive radiator designs.
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  • Conradicles
    Conradicles Posts: 6,041
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    Zero port noise rules!
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  • SCompRacer
    SCompRacer Posts: 8,352
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    ROHfan wrote: »
    Very interesting. Thanks for the replies.

    I've not seen any other speaker brands employing the passive radiator, although I'm sure they must exist. I'm wondering how the accuracy of lower frequencies compare to the SDAs.

    Salk uses them. The SoundScape 12's use two 15" PR's. He explained that without them, he would have needed a 9 foot long port of a specific size to prevent chuffing. The SS12's play to an F3 of 18Hz. The SS10's like these (10" woofer) have an F3 of 20 Hz.

    4562.jpg

    My SS8's with dual 8" woofers, an F3 of 25Hz.

    ss8-blacklimba.jpg



    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ * Signature Series Sonore Music Server w/Deux PS * Roon * Gustard R26 DAC / Singxer SU-6 DDC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *
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  • Conradicles
    Conradicles Posts: 6,041
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    Those are beautiful.
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  • Mystery
    Mystery Posts: 2,546
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    Conradicles wrote: »
    Those are beautiful.

    And pricey... Some day...

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
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  • Mr. Sharpe
    Mr. Sharpe Posts: 1,354
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    ROHfan wrote: »
    Very interesting. Thanks for the replies.

    I've not seen any other speaker brands employing the passive radiator, although I'm sure they must exist. I'm wondering how the accuracy of lower frequencies compare to the SDAs.

    Definitive Technology and Legacy audio. didn't the designer for the vintage polk speakers start designing Definitive speakers? or am I just crazy?

    Home theater:
    43” Westinghouse Displayer
    Marantz UD-7007 Player
    Emotiva MC-700 Processor
    Adcom GFA-5006 Amplifier
    Parasound Zamp Amplifier
    Ethereal ESO-1 Power Conditioner
    Klipsch RC-10 Center
    Klipsch R34c Fronts
    Klipsch RB-41 Surrounds
    Polk audio PSW-505

    Stereo:
    Polk audio RTA-12c’s fully upgraded crossovers
    DIY 12tc braided speaker cables
    Denon DVD-5910ci Spinner
    Parasound P6 Preamplifer
    Parasound HCA -1500a Amplifier
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  • Mystery
    Mystery Posts: 2,546
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    How did I forgot to mention this.
    All my Klipsch kg2, kg4, forte have passive radiator on the back.
    The best passive bass I've heard so far is Sonus Faber. I always think it's active because of the grunt and forceful bass instead of bouncy bass from most other brand pr's.

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
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  • ROHfan
    ROHfan Posts: 1,014
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    Man, those Salks are gorgeous!
    TV: 65" Samsung QLED 4K
    Fronts: Energy RC70 --- Center: Energy RC-LCR
    Front Heights: Polk RC65i --- Rears: Polk RC85i --- Sub: Power Sound Audio XS15
    Pioneer VSX-1120K --- Parasound HCA-1000A --- Oppo BDP-103
    Vincent Audio SA31 preamp --- Teac UD301 DAC
    AIYIMA Tube T7 preamp --- Nobsound 12AX7 tube preamplifier
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  • leftwinger57
    leftwinger57 Posts: 2,917
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    Westmassguy, is right again.One of my favorite speakers of the mid 70's and in direct competition to the Bose 901s at the time. Yes a huge foot print but those Heil tweeters and the combo of 12'' speakers in front 12'' passives in the rear were awesome. ESS Heil is still in business out in California. No affiliation....

    http://www.audioreview.com/cat/speakers/floorstanding-speakers/ess/amt-1b/prd_119461_1594crx.aspx
    2chl- Adcom GFA- 555-Onkyo P-3150v pre/amp- JVC-QL-A200 tt- Denon 1940 ci cdp- Adcom GFS-6 -Modded '87 SDA 2Bs - Dynamat Ext.- BH-5- X-Overs VR-3, RDO-194 tweeters, Larry's Rings, Speakon/Neutrik I/C- Cherry stain tops Advent Maestros,Ohm model E

    H/T- Toshiba au40" flat- Yamaha RX- V665 avr- YSD-11 Dock- I-Pod- Klipsch #400HD Speaker set-

    Bdrm- Nikko 6065 receiver- JBL -G-200s--Pioneer 305 headphones--Sony CE375-5 disc
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