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Why so few acoustic suspension woofers?

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  • Why so few acoustic suspension woofers?

    Look at these specs for the ADS L730:
    http://stereonomono.blogspot.com/2012/12/ads-l730.html

    That is an acoustic suspension design. 92 db SPL w/ 1-watt, hitting an F3 of 30-Hz in a 1.77 cubic foot box.

    That seems real impressive to me. 92 db and 30-Hz.

    There are plenty of other ADS models that are acoustic suspension designs and which (IMHO) outperform similarly sized units w/ ported enclosures.

    Conventional wisdom for several decades now has been that ported systems have an advantage.

    And it would seem woofers intended for AC use would be less expensive to manufacture (smaller magnets)?

    Thoughts?

  • #2
    Re: Why so few acoustic suspension woofers?

    Originally posted by philthien View Post
    Look at these specs for the ADS L730:
    Has anyone verified these specs?

    Let's take a real-world woofer - the Vifa NE315.
    In a ~1.7 cubic foot box, you're looking at a f3 of 40hz and an efficiency of 85dB - before baffle step compensation.

    The F3 spec might be in-room (if your room is a broom closet), and the efficiency spec is just wildly optimistic.

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    • #3
      Re: Why so few acoustic suspension woofers?

      I can think of a couple reasons. All things being equal, ported will almost always give a lower F3, which helps sales. The cone excursion of a ported driver is much less near the port tuning, which helps distortion performance. That's especially important when bass is demanded of a small woofer.

      Francis
      Francis

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      • #4
        Re: Why so few acoustic suspension woofers?

        Originally posted by spasticteapot View Post
        Has anyone verified these specs?

        Let's take a real-world woofer - the Vifa NE315.
        In a ~1.7 cubic foot box, you're looking at a f3 of 40hz and an efficiency of 85dB - before baffle step compensation.

        The F3 spec might be in-room (if your room is a broom closet), and the efficiency spec is just wildly optimistic.
        I haven't been able to find any reviews, I do imagine that they'd have been reviewed in Stereo Review or Audio, I just wish I had access to that old stuff.

        I have used various ADS speakers and have been impressed with the simultaneous LF extension and pretty high sensitivity.

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        • #5
          Re: Why so few acoustic suspension woofers?

          Originally posted by fpitas View Post
          The cone excursion of a ported driver is much less near the port tuning, which helps distortion performance.
          This is a large part of the cost equation. Going from a 2-way to a 3-way doubles your crossover part count, and those big caps and coils can quadruple the cost of the crossover. A ported 2-way is cost effective.

          You can build a nice pair of ~1.7 cu ft speakers using the Vifa woofers in question - they have the Xmax and low distortion required to give the output of a 8" or 10" speaker in a smaller box. They do cost a bit, though...

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          • #6
            Re: Why so few acoustic suspension woofers?

            My friend has a pair of the ADS L810, I absolutely love them for some reason. They are not super efficient, those numbers are definitely bloated, but they are very well built and the bass is greta for their size imo. The woofers are in independent sealed chambers, those cabs are bulletproof. I'd really like to get my hands on a pair of them.

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            • #7
              Re: Why so few acoustic suspension woofers?

              Originally posted by philthien View Post
              Driver Complement:
              One acoustic suspension soft-dome tweeter...
              One acoustic suspension soft-dome midrange driver....
              Thoughts?
              I think that was written by a clueless marketing department. Tweeters and midranges aren't acoustic suspension. Chances are the woofer isn't either. All acoustic suspension boxes are sealed, but by no means are all sealed boxes acoustic suspension. True acoustic suspension means an Fs no more than 1/2 the F3, which requires a high Mms and therefore low sensitivity. The benchmark AR woofer had a 19Hz Fs for a 41Hz f3. The likelihood of any ten going to 30Hz F3 with 92dB sensitivity in a sealed cab is nil.
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                Re: Why so few acoustic suspension woofers?

                Originally posted by Adam_G View Post
                My friend has a pair of the ADS L810, I absolutely love them for some reason. They are not super efficient, those numbers are definitely bloated, but they are very well built and the bass is greta for their size imo. The woofers are in independent sealed chambers, those cabs are bulletproof. I'd really like to get my hands on a pair of them.
                Link to an interesting review of the L810's:

                http://sportsbil.com/ads/l-810-review-2.pdf

                It says the L810 system measured the claimed 93db/1watt.

                But the review also dings the L810 for lower bass response. But the manufacturer responds that they made a revision and the resulting lower bass is better. But maybe the change was swapping woofers? And maybe the replacements are less sensitive, and maybe your friend has those?

                That is a lot of if's, sorry.

                I will say I built my "sub" from a woofer from an 810 and a Logitech Z-2300 amplifier, and my in-room bass is incredible.

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                • #9
                  Re: Why so few acoustic suspension woofers?

                  Originally posted by billfitzmaurice View Post
                  I think that was written by a clueless marketing department. Tweeters and midranges aren't acoustic suspension. Chances are the woofer isn't either. All acoustic suspension boxes are sealed, but by no means are all sealed boxes acoustic suspension. True acoustic suspension means an Fs no more than 1/2 the F3, which requires a high Mms and therefore low sensitivity. The benchmark AR woofer had a 19Hz Fs for a 41Hz f3. The likelihood of any ten going to 30Hz F3 with 92dB sensitivity in a sealed cab is nil.
                  Hoffman wins again

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                  • #10
                    Re: Why so few acoustic suspension woofers?

                    Originally posted by cooper View Post
                    Hoffman wins again
                    +1. For bonus points tell us who Tony Hoffman worked for, and how that all ties neatly together with the OP's question.
                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

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                    • #11
                      Re: Why so few acoustic suspension woofers?

                      A typical acoustic suspension woofer has low compliance (large Vas) high magnet strength (low Qes) and low fs. Some Altecs fit that bill. 70s Pioneer with the "FB" cones can fall into that range and can be bought fairly cheap but need twice the cab size that they produced and are nice devices for DIY. Another good fine are the early 80 Yamaha NS5, and 8 systems which are surprisingly nice sounding and 90-92db but only 40s f3. These are the sane series as the yellow cone monitors but different designs all together.

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                      • #12
                        Re: Why so few acoustic suspension woofers?

                        To backup what the OP is saying here minus "acoustic suspension", I spent a night recently looking at all 10" woofers from several retailers online (PE, Madi, Mensicus). Looking at the more 'HiFi" drivers, I found almost none that modeled well in sealed enclosures. BY well I mean: realistic volumes, F3 40 or lower. It is a shame, I'd like to see more drivers optimized for sealed enclosures personally.
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                        • #13
                          Re: Why so few acoustic suspension woofers?

                          Not sure if I'm understanding the question.

                          Why so few acoustic suspension (sealed) speakers in DIY or commercial market? NHT comes to mind.
                          Or... Why so few woofers suitable for acoustic suspension cabinets?

                          Mostly, on both counts, because we (generally) want to squeeze the last drop of bass out of the smallest possible drivers. Kind of silly in these days of subwoofers.

                          Comment


                          • #14
                            Re: Why so few acoustic suspension woofers?

                            Originally posted by billfitzmaurice View Post
                            I think that was written by a clueless marketing department. Tweeters and midranges aren't acoustic suspension. Chances are the woofer isn't either. All acoustic suspension boxes are sealed, but by no means are all sealed boxes acoustic suspension. True acoustic suspension means an Fs no more than 1/2 the F3, which requires a high Mms and therefore low sensitivity. The benchmark AR woofer had a 19Hz Fs for a 41Hz f3. The likelihood of any ten going to 30Hz F3 with 92dB sensitivity in a sealed cab is nil.
                            I've seen you bring this up before (in terms of not all sealed enclosures being acoustic suspension).

                            So I infer from what you write that a specific set of parameters is required for a design to be considered acoustic suspension.

                            BUT, the drivers in ADS speakers are extremely compliant, without a sealed enclosure they would certainly overshoot their excursion limits fairly easily.

                            I'm aware of larger (older) sealed designs where the woofers were pretty stiff, they didn't rely on the enclosure for an air spring as much as they were controlling cancellation from the rear of the cone, right?

                            I mean, these ADS designs may not hit the exact definition of acoustic suspension but they sure are nothing like the old-school sealed boxes I've seen, either.

                            I guess what I'm driving at is, you seem to want a distinction drawn between true acoustic suspension designs, and designs that are merely sealed, but these ADS designs (and many others) rely on the core aspect of the acoustic suspension principle, which is relying on the enclosure as an air spring due to their extremely compliant nature.

                            So I don't know what I'm missing here.

                            Enlighten me, please.

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                            • #15
                              Re: Why so few acoustic suspension woofers?

                              Originally posted by scholl View Post
                              A typical acoustic suspension woofer has low compliance (large Vas) high magnet strength (low Qes) and low fs. Some Altecs fit that bill. 70s Pioneer with the "FB" cones can fall into that range and can be bought fairly cheap but need twice the cab size that they produced and are nice devices for DIY. Another good fine are the early 80 Yamaha NS5, and 8 systems which are surprisingly nice sounding and 90-92db but only 40s f3. These are the sane series as the yellow cone monitors but different designs all together.
                              Woofers employed in acoustic suspension designs like that Advent had tiny magnets. How does that equate to high magnet strength, are the magnets extra-powerful or something?

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