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"2,000" watt woofer in a 50 watt system

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  • "2,000" watt woofer in a 50 watt system

    Hello everyone.

    My project is keeping the wife happy and to do that I need some speaker advice. I built the wife a studio above the garage, a place where she can draw and paint or just get away from me. I had some extra equipment laying around so about 15 years ago I installed a Denon receiver, a DBX SW15 woofer and a pair of small Polk speakers. For those that don't know the DBX SW15 it was nothing to write home about even when new 30+ years ago. It takes the L+R speaker inputs sends the bass to the 15" woofer and the higher freqs to the satellite speakers.

    One day the wife said the radio sounded "funny" which could mean anything but in this case it meant that the paper surround on the woofer had mostly turned to dust. The cabinet is 3.25 Cuft an takes a dual voice coil speaker of maybe 8 ohms. (one coil measures 5,6 ohms and the speaker label on the box says 6.3 ohms). The problem I'm having is finding a dual coil "home" speaker. I've found some for automotive use such as the Lanzar MAXP154D sold here at PE. It doesn't show a recommended sealed box but WinISD comes up with a pretty good looking graph. Now I only got WinISD 4 days ago so I could graph the different speakers and the cabinet but I'm pretty sure I've got it figured out.

    So my question is do I really need hundreds of watts to make this Lanzar sub work or will it actually supply some bass when hooked into a 50wpc system which is playing at conversational volume?
    Any and all ideas welcome short of buying a new system.. I thank you and my wife thanks you.

  • #2
    Al, the dual voice coil has me wondering if the speaker takes inputs from a stereo setup. In other words, each coil is being driven by one channel. If not, why not just get a single voice coil woofer? The problem then becomes matching the efficiency to the old one which will be difficult without the original in working order. 50 watts will be fine if you get a efficient woofer and don't expect earth shattering low frequency output. Sounds like a older speaker. I would look at some of the pro woofers which are more efficient.

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    • #3
      Yes I missed saying that each channel goes to a separate voice coil. Now supposedly, according to the spec sheet the Lanzar is 89db/watt. The Polks I'm using for satellite speakers say they are 88db/watt. Even with some crossover loss that should be close enough don't you think?

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      • #4
        The Lanzar is a 4 + 4 ohm voice coil woofer. It's made to mount in a trunk given it's recommended sealed volume size of 13+ ft3. I doubt a car sub will be a good match for you.

        Your sub takes in the L-R channel outputs from the receiver, has twin passive 2nd order LP filters to extract the low frequency content and drive the sub-woofer's twin voice coils. Then passes the receiver's signal to the Polks.

        It may be difficult to find a suitable sub woofer that has dual voice coils, will work in the DBX's box size (I believe it's sealed) and has a sensitivity to will match with the Polks for a even transition, volume wise, between the sub and the Polk. Especially given the shift of sub woofer operating characteristics since the DBX was designed.

        A couple of suggestions:

        One: Find a 15" sub that fits your box volume and add a plate amp that accepts high level speaker inputs. That opens up a range of drivers and the plate amp will allow you to dial in the LP cut-off freq. and match the sub's output to the Polks.

        Two: The Goldwood GW4120 12" woofer or perhaps the Dayton Audio SD270 10" woofer may be a decent match. You could make an adapter ring (MDF, Plywood) that allows a 10" or 12" driver to mate with the DBX's 15" opening. Model those drivers in a sealed box using WinISD. If the model requires significantly less volume than the DBX box provides, you can glue in some wood to take away volume in the box.

        Also, make sure your DBX volume calculation is using the inside measurements, not the outside. And the driver actually takes away some space from the total available volume.

        Lastly, you say the paper surround has disintegrated. There are replacement surround repair kits available for the DBX 15" woofer and many here have restored old woofers using them.

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        • #5
          Replacing a deteriorated surround with a repair kit is not that hard.

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          • #6
            There's one on Ebay for 80 dollars. Tell the seller all you want shipped is the driver. Worth a try.

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            • #7
              Originally posted by djg View Post
              There's one on Ebay for 80 dollars. Tell the seller all you want shipped is the driver. Worth a try.
              80 miles away so about $15 in gas and time to smoke a good cigar. That could be it. Thanks! Another option is there is a pair of JBL speakers for sale locally with 8" woofers which certainly beats the 4" in the Polks and still would fit on the shelf they are on.. I'm going to see those tonight after the seller gets home. Thanks for the help everybody!

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              • #8
                I’d consider this https://www.parts-express.com/dayton...4-ohm--295-470 with a cheap 100-200 watt plate amp with boost, like the Yungs. (This is assuming your box is sealed)

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                • #9

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                  • #10
                    I bought the JBL's and she likes them which is the important part.

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                    • #11
                      Originally posted by Al_B View Post
                      I bought the JBL's and she likes them which is the important part.


                      Francis

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