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Woofer vs Subwoofer; whats the difference? (Dayton DC2508 vs SD270A88)

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  • Woofer vs Subwoofer; whats the difference? (Dayton DC2508 vs SD270A88)

    Hello,

    I am pretty new to DIY speaker build and having a tough time understanding what is difference between 10" woofer vs subwoofer from same company with similar specs. How does one choose one or the other? I understand that subwoofer is meant for lower frequencies than woofer. If you see the parameters and frequency response both look pretty same. What parameter or property sets the subwoofer apart from the woofer?

    Table below is a comparison of the parameters. I am surprised that woofer has lower Fs than subwoofer. If so, why use a subwoofer? The rated power is also quite similar.
    Apart from Le and Xmax the parameters are pretty same. I expected subwoofer to have more of Xmax but it is only 1.5mm greater than woofer. which is 33% greater. Is that the only significant difference between subwoofer and woofer? In layman terms subwoofer can handle more power output at lowest frequencies than woofer.

    Then why not just use subwoofer in place of woofer (frequency response up to 1KHz seems to be same)?

    What am I missing? I assume there is some tradeoff/optimization being made, I just want to understand what that is. Thanks in advance.

    Subwoofer Woofer
    SD270A88 10" DC2508 10"
    Impedance 4 ohms 8 ohms
    Re 3.16 ohms 6.6 ohms
    Le 1.12 mH 2.63 mH @ 1 kHz
    Fs 26.2 Hz 24.9 Hz
    Qms 3.23 3.16
    Qes 0.5 0.44
    Qts 0.43 0.38
    Mms 57.70 g 67.5g
    Cms 0.64 mm/N 0.61 mm/N
    Sd 346.4 cm² 343.1 cm²
    Vd 207.8 cm³ 154.4 cm³
    BL 7.80 Tm 12.64 Tm
    Vas 107.5 liters 104 liters
    Xmax 6.0 mm 4.5 mm
    VC Diameter 38.5 mm 35 mm
    SPL 87.8 dB @ 1W/1m 88.4 dB @ 2.83V/1m
    RMS Power Handling 80 watts 70 watts
    Usable Frequency Range (Hz) 26 2,000 Hz 25 2,500 Hz

  • #2
    A subwoofer's maximum travel without damage should be much higher than it's xmax, for a woofer not so much.

    A subwoofer's breakup is often much greater in magnitude than a woofer's, so we usually go active, as active filters can be much steeper and the separate amp gives us level control, so we needn't pad down the upper range section, and can reach higher max spls.

    However, you have hit upon a really good woofer being sold as a subwoofer, I like it a lot but would not choose it for a sub, rather as a woofer with which you do not need a separate sub.

    Comment


    • #3
      The only real diff is that subs are crossed low enough to not be locatable sonically. But that is kind of a gray area. Sub drivers tend to only be good to a few hundred hertz at best, but even that isn't a fixed rule. I use my RSS390HF-4s crossed with a shallow LR2 at 150Hz for example, and they work very well.
      Francis

      Comment


      • #4
        Originally posted by davidB View Post
        However, you have hit upon a really good woofer being sold as a subwoofer, I like it a lot but would not choose it for a sub, rather as a woofer with which you do not need a separate sub.
        Adding to davidB's comment...the RSS 10" SUBwoofer handles 350 watts RMS and has an xmax of 14mm.
        In GENERAL a sub is going to go lower and have more xmax, but with the variety of drivers out there there will always be exceptions.

        Comment


        • #5
          The "sub" title doesn't really mean as much as: 1) the Xmax actually limits how much power a driver can take down low - the RMS limit is nearly useless.
          2) A 6.5" "woofer" might be expected to play midtones cleanly up to 2000 Hz or more (like for use in a 2-way). I THINK TandBand's W6-1139 "sub" naturally drops off below 1k, maybe even 500Hz.

          How low a driver(+box) can reach is not determined by Fs (solely), but by Fs and Qts. W/out running a sim (didn't you?) I'm guessin' that the SD270 could do 24Hz in 4.5cf; the DC250 maybe 27Hz in about 3cf. They COULD be comparable in the same sized vented box, but box size is determined by Vas AND Qts.
          In the same box (4cf vented) w/the same 20wRMS, THOSE 2 woofers do have nearly identical performance. The one w/more Xmax can take 67% more power though (good for about +2dB, AEBE).

          There have been many 3-ways (here) designed w/a "sub" for the bottom end; as well as "subs" built using just "woofers".

          BTW - Dayton must have very recently updated the DC250's T/S parms: in the past yr. they were listed as: Fs = 29Hz, Qms = 4.0, Qes = 0.50 (Qts = 0.45), Sd = 323, BL=10, Vas = 108.5 liters, and 89dB SPL.
          Do I think (in the last yr. or 2) that Dayton changed the strength of their magnets (BL)? Possibly (but I doubt it).
          Do I think they changed the size of their cone and surround (Sd)? No I don't. The NEW parm might have been more carefully measured than in the past (the last time) though.

          Comment


          • #6
            Has anyone compared the old DATS to the new? They may test at different levels.

            Comment


            • #7
              The original definition of a subwoofer was a speaker intended for use in the range below where woofers worked, ie., below 40Hz. That definition has eroded over the years, to the point now that even four inch drivers that won't do much below 50Hz are given the subwoofer tag. If it works it works, ignore what it's called. For that matter if it doesn't work it doesn't work, so in that case also ignore what it's called.
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

              Comment


              • #8
                Thanks everyone for your responses. It clears up my confusion. I have a follow up question.

                Which one of these would one use if one is looking for "clean bass', "tight bass", "fast bass"..for music application. .Not looking window rattling bass. In this case would low value of Le be the parameter to look for?

                Comment


                • #9
                  Either driver can do mid 20s in a ported box. Sealed, they'd only do about 50Hz (w/out "room gain"). Nearly any "modern sub" will use a "plate amp" to blend the sub w/your mains (L/Rs). They do this by giving your variable phase (prob. not too critical - your could always swap the driver leads if you HAD to), adj. volume (pretty important), and adj. freq. range (also very important). Personally, I probably wouldn't bother with them if they only did 50Hz.

                  That means that you'd either go ported w/an "un-boosted" plate amp, OR... you COULD hit 50Hz in a closed box IF you used an amp w/"boost". Neither of these drivers is probably "hefty" enough to handle that. The "quality" of bass you'd end up getting will be mostly determined by your (vented) box design (i.e. - not "boomy") AND your room placement (which can be very critical, depending). One option w/a ported box if you don't like the sound (and want something "leaner") is to stuff the port with something (like socks or a nerf football). My experience w/the DVC subs ("SD" series) is that the 12" basically takes the same size box as the 10" (and box size is often a large factor). I'd probably go w/the 12" SD (DVC) and probably 100w amp.

                  Comment


                  • #10
                    Originally posted by Brij View Post
                    Which one of these would one use if one is looking for "clean bass', "tight bass", "fast bass"..for music application.
                    None of those terms have any meaning in an engineering sense. They're used by those who don't know what the engineering term is for what they're trying to describe, which could be just about anything. As for Le, it affects the upper end of the driver response, not the lows.
                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

                    Comment


                    • #11
                      Originally posted by Brij View Post
                      Thanks everyone for your responses. It clears up my confusion. I have a follow up question.

                      Which one of these would one use if one is looking for "clean bass', "tight bass", "fast bass"..for music application. .Not looking window rattling bass. In this case would low value of Le be the parameter to look for?
                      Like Bill said, those are terms thrown around on the internet that have little meaning. The room will probably be the biggest contributor to the sound of the bass. Even the best sub will sound boomy and "loose" in a highly resonant and reverberant room.
                      Francis

                      Comment


                      • #12
                        I've never used the DC250, but I can report that the SD270 is a very good sounding budget 10" woofer. I used it sealed in my Indium 7 design crossed to a 2"dome mid at around 700 Hz. I chose the SD270 based on a few factors. The frame doesn't have the cardboard trim ring like the DC250. Both have pretty good frequency response into the lower mids - but the SD270 has lower inductance. The SD270 has a sealed F3 in the upper 40's in the box I used. A lot of people who have heard the Indium 7's have been pleasantly surprised at the quality and quantity of the bass. I think sealed SD270 is a great option for a music application.
                        Keep an open mind, but don't let your brain fall out.

                        Sehlin Sound Solutions

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                        • #13
                          Thanks for your input Scott. Looks like SD270 is a good option for music and that is my main application as well.

                          Comment


                          • #14
                            The plate amp can extend the f3 by virtue of the low-pass filter. The "normal" f3 of this driver in a sealed box is about 61hz. Now it's at 25hz!


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