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Does this make sense: sub1 50-80Hz, sub2 10-50Hz

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  • Does this make sense: sub1 50-80Hz, sub2 10-50Hz

    Just wondering, does this make sense? Does it exist?

    I'm picturing a quality 8" or 10" driver that is tuned for 40-100Hz and intended to be crossed over to cover 50-80Hz (even up to 100Hz, to make bookshelves for fronts great).

    Then you have a second unit with a 15" or 18" driver that is only meant for <50Hz.

    In such a setup would either, both or neither be best as sealed/ported?

    Does an 8" speaker with single sub-in connector and a crossover to provide sub-out exist? Could it be a TCA product?

    Just wondering.....:scratchchin:

    EDIT: I guess this is pretty much what the HSU MBM-12 is :blockhead:

    And I guess their patent pending would discourage anyone (like TCA) from pursuing one.

  • #2
    I would shoot for a cross inthe 25-35 us range. My thinking on that is based on the fact the most musical instruments live above the low E at around 41.5 hz.

    Other than that a two sub solution could give excellent results I think.

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    • #3
      To answer the Hsu thing, IMHO thehy got it backwards. The product missing from the market is the affordable 10-40 hz sub, not the mid bass.

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      • #4
        Originally posted by m-fine
        To answer the Hsu thing, IMHO thehy got it backwards. The product missing from the market is the affordable 10-40 hz sub, not the mid bass.
        Is that because sub designer who shoot for 10-40Hz are also trying to be flat up to 100Hz?

        What else is out there that is good between 40-100Hz but has a really sharp roll-off at 40 (so it wouldn't interfere with the low sub)? Or would you have circuitry so that it only received 40-80Hz?

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        • #5
          You could use a sub with a natural rolloff between 25 and 35 hz of which there are a good number, or you could use a crossover. I think a LOT of people out there have a sub that is decent in the music range but could use some support for the deep stuff in HT, and crossing many of them over at 35 hz would free them up to perform better in the 40-80 range.

          To answer your first question, how many commercially available subs do you know of that can do 10 hz for less than $2k? If you could build one affordably, that could deliver the deep stuff well, but perhaps sacrifice the upper bass capability it could be a cool product as a sub-sub.

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          • #6
            This post got me thinking that the HSU would actually be great for the rear surrounds to pick up the directional bass that is getting redirected to the sub from bookshelf surrounds. Of course, you would need another external crossover to handle it unless you wanted to send full range to the rear surrounds.

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            • #7
              The idea does make sense, and i have experienced this with good results, but you have to consider that 40-100hz is still pretty low frequencies, an 8" is a tiny woofer by sub standards and the only benefit of a smaller cone is really the polar response. An 18" cone size is going to start having issues at around 300 or 400 Hz. So unless you plan to use it up there, you might want to consider a really large woofer unless space is a problem. Even so, a 15" can nearly take you to 1000Hz without a problem if its designed right. So my point is, its not the size of the cone, but the type of the driver. The two-way sub i used had two 18's, but they had very different parameters.

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              • #8
                I'm starting to think that a Rythmik F12 for the 40-80 (or 100) range with a nice 15" (Epik Calibre or Castle, MFW-15, etc) for the 15-40 would be nice (not affordable for me today, but nice).

                Just wondering two things though:

                - does anyone build a nice sealed 10" sub

                - at what frequency does audio become localized (sorry if that isn't the term)

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                • #9
                  In my experience you have to be a good bit above 100 hz to localize a clean signal, especially if the sub is on the front wall with the mains. If you have distortion that shows up in the higher frequencies or port chuffind and other noises they can reveal where the sub is.

                  If the sub is behind you I think it can be a little easier to localize (still over 80-100 hz.) but that could be phase or other setup issues.

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                  • #10
                    Mark Seaton mentioned to me that he was toying around with this type of idea. Using multiple smaller subs scattered throughout the room for the higher "sub" frequencies and using a large corner loaded monster for the low end.
                    With a shovel...

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                    • #11
                      Hi all. I've been visiting this site since it began, but haven't registered until now.

                      I have 4 of the Tumult MKI 15" subs in dual opposed sealed configuration. The MKI has a rather steep inductance drop off above 40-50Hz, which I was able to deal with using EQ, but was never satisfied with. The only answer is to lower the crossover point with the mains, which limits transient response and burdens the mains.

                      Here is Ilkka's GP FR of a Tumult MKI with my own close mic response of the MKI and a Brahma 15 based sub done 2 years prior to Ilkka's measurement. You can see the roll off and that they are very similar results.


                      Here's a pic of the 2X15" MKI sub:


                      I decided to buy 20-6.5" drivers from Parts Express that I had looked at back when I measured the MKI. They're cheap Pyramid drivers that I got for under $11 each. It was under $250 for the lot shipped.

                      I put the drivers in 5 cubes in a sealed push/pull alignment. Here's a photo of the finished sub followed by a photo of the back side, showing the pull side.

                      Of course, you could simply build a 12" X 12" X 40" or so high narrow tower or some other simpler box, but I wanted to utilize the corner for boundary gain and I like subs that look different.



                      Here is a close mic response of the mid sub and the MKI sub. The MKI sub has a 60Hz LP filter and the mid sub is rolling off naturally with no HP filter,


                      One great advantage to multiple smaller drivers is increased sensitivity. The drivers specs claim 96dB sensitivity, but Ilkka calculated more like 87-88dB and I agree at least that the real number is south of 96dB.

                      Still, taking the worst case scenario of 87dB, with 20 drivers you're doubling the number of drivers 4+ times, which puts the system sensitivity at over 100dB. I was able to use a 500W amplifier to get very good and clean output above 60Hz.

                      Being that the small drivers have very little wire in the VC, they are flat to well above 200Hz, so I was able to cross with the mains at 100Hz or higher. Some nay sayers claimed localization, but I've never subscribed to the idea. IMO, EVERY sub is localizable if it's calibrated hot or other than flat.

                      Here's the final in-room response with mains/mid/sub/sub-sub:


                      Those familiar with my system in it's various forms all commented on the difference the mid sub adds. I agree. I'll be building a 32 driver version as soon as I finish the 3 subs I'm building now (which are nearing completion.

                      Proof is in the puddin'.

                      Bosso

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                      • #12
                        Bosso - Very nice job on the mid woofer ! You would probably see much closer to 96 dB at 1000 Hz, but in the 60-120 Hz range, 87/88 would be about right. Even 96 is going to be somewhat exagerrated.

                        The mid woofer has to be about the coolest one ever made.

                        Welcome aboard, old friend !! :thumbsup:

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                        • #13
                          Bosso....

                          .....that is just SICK....:huge::biglaugh:

                          And here I am, wondering if 2 SCAMPS are gonna be tooooo much...:neener:

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                          • #14
                            And another thing....

                            ...regarding the OPs question....

                            I asked a similar question some time ago (not here / likely AV123...but who knows...) Except I was thinking sub for music/sub for HT...

                            Would there be that much difference in what the OP is trying to accomplish and what I was thinking???:poke:

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                            • #15
                              Originally posted by rumonkey2
                              ...regarding the OPs question....

                              I asked a similar question some time ago (not here / likely AV123...but who knows...) Except I was thinking sub for music/sub for HT...

                              Would there be that much difference in what the OP is trying to accomplish and what I was thinking???:poke:
                              No. In fact, there are advantages to what you suggest.

                              Back in '02 I developed a low freqs preamp with Phil Marchand that he built for me and that I still use,

                              I call the system Rebase Routing. I take the LFE analog out of the player directly into my RR preamps LFE channel and the redirected bass from the AV preamp directly into the RR preamps redirected bass channel.

                              That keeps the LFE and RB discrete. The music track is discrete from the low frequency effects track.

                              As it relates to the OPs question though, you still need the RB sub to be able to handle the mid bass.

                              It's a better routing scheme, period. The reason I had to abandon any further product development is that Dolby encourages mixing of the LFE into the LCR channels so that Dolby Digital can be backward compatible with Dolby Pro Logic, which did not have a discrete .1 LFE channel.

                              IOW, if LFE is mixed only in the .1 channel (as it technically should be), then Pro Logic users (does anyone actually believe there are still Pro Logic receivers in use, and if they are, who cares about them??) would not get any of the low end effects in their system.

                              Bosso

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