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Building a Subwoofer on a budget

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  • Building a Subwoofer on a budget

    I have an old RH Labs passive sub. I want to turn it into a powered sub to be used with a pair of older Magnaplanar MG1's. I plan on refurbishing those as well and gifting the speaker system to my nephew as he has shown a really healthy interest in music. Of course he is going to help me by doing all the grunt work.

    I just gutted the xrossover and the driver. The box appears that it will be useable to DIY a powered sub. It is made of 3/4 MDF. Looks solid and well put together. There was a 10 inch driver in the box with the following inner dimensions- 20in (W) 14.5in (D) 16in (H). The driver looks really cheesy. HA! The speaker surround is gone. My initial thought are to continue the sub as a sealed system with music in mind. I hope I can upgrade to a new 12 inch driver with the above dimensions with a nip here and a cut there on the driver mounting surface. There is plenty of room for that.

    The original design was down firing onto a foam landing pad glued to a flat surfaced elevated about 2.5 inches from the driver and attached to the box. I plan on eliminating the landing pad and just adding new feet/spikes.

    My budget for the sub and plate amp is $200. I've seen a plate amp at Parts Express for $129. There are subwoofers there as well within the budget. That may not be the best place to start.

    What would be the best plate amp and woofer to match my box?
    Is my box big enough to do a sealed 12 in powered sub?
    Is this possible on this budget. My nephews mom is kicking in $150. I thought $100 from me would be enough. I'll get some pictures here when my wife returns on friday as she has the camera with her.

    I know I could spend more and build a really kick ass sub for him. However the Magnapan refurbish will involve new socks and silver solder. It will run about $200 as well.

  • #2
    Budget is $250. My bad.


    • #3
      The internal box volume that you posted would be very close to 2.7cubic feet.

      Have you looked at the GR-Research passive sub, the SW-12B 12" driver? It calls for a 2.3cuft cabinet with a port. Would not be hard to remove 0.4cuft of volume by adding some objects inside the cabinet. Did not see if the original box was ported or sealed.

      Might want to talk to Danny about this if you are interested. His website is:
      Better living through Audio Nirvana!


      • #4

        Thanks for the input. The unit is sealed. Perhaps I should be looking at 15 inch woofers?


        • #5
          Guess not the one internal measurement is 14.5 in.


          • #6
            I am mostly a 'lurker' around these parts, but I could not resist adding my 2 cents on this thread (I am waiting to see if I can participate in Craig's beta testing). I have built a few subs myself. For the budget you have for both amp and driver, I would say Parts Express might be the best place for both. I have used their 240 watt plate amp and their HSS315HF-4 (4 ohm) and both work very well. The HF is a 12" driver designed for very low distortion and has a 150 oz. magnet - it's kind of a beast. And it is currently on sale for 119 and free shipping. The 12" Titanic driver is better, but you would go $20 over budget with that. The Dayton SA240 240W Subwoofer Amplifier is also currently on sale for 109, so you would be under budget with that and the HSS! You can also call the tech assistance line at PE to see what they might suggest. They will even run numbers for you (design software) to suggest designs or compatibility of drivers with your cabinet. I have also used other sources that I have liked, but for the budget I imagine PE might be easiest and cheapest.


            • #7
              Not to highjack the thread, but just wondering if anyone thinks it'd be worth it to try to build an 8 or 10 inch sub for $100 or less, rather than buying the cheap Dayton or used Energy ESW-8?


              • #8
                For the low budget builds, it is the amp that concerns me. I would definitely want to get recommendations from someone that has experience using the amp in question.


                • #9
                  I contacted GR Research and got some great advice from Danny.

                  Thanks HAL that was great advice.

                  He suggested to build out the inside of the box with strips on MDF glued to the inside. Easy way to decrease the inner size. Easy because I have the woodworking skills of a mosquito. He also advocated some bracing as well.

                  He indicated that he has a plate amp coming soon specifically designed for Sealed Boxes that fits my budget when used with his woofer. I'm not sure if It would be appropriate to share the technical stuff with out his permission. But it all looked good to me. I am looking to support an audio system. I want a sealed audiophile sub. Uh for $250.

                  I looked at the PE gear. It does look really well built. I wonder where I could get some reveiws on this gear. Thanks for your endorsement Shabda. Any thoughts?

                  Blackzarg, just what are you trying to say? Buy used? Or are you thinking of building a $100 sub yourself? I'm confused.


                  • #10
                    That is great info, thanks for sharing. :thumbsup:


                    • #11
                      A little more from Danny came in today.

                      He suggested that I router an 11 in hole in sheets of MDF that fit into the box. Then cut them in half to make it easier to fit them inside and glue them up.

                      He indicated that if I can get the inner demensions to 1.5 cu ft I'm in the safe zone for the system. Thanks HAL for the Q calcutator.

                      I can use the Fiberglass like stuff from the older woofer as fill.


                      • #12
                        I haven't really seen much in the way of reviews of individual drivers that are sold at places like PE or Madisound. The only type of review available that I am aware of would be personal experiences from folks like me that can also be found in the reviews at PE. These often include professionals who have used the component in various applications. As for me, I have used the 12" I mentioned in a subwoofer with a passive radiator that I also bought at PE. The cabinet is 3.2 cu ft and with the passive is tuned to about 18 hz. The 240 Dayton amp is mounted on the rear of the cabinet, which is made of two layers of MDF totaling 1 1/4 in. thickness, so the sub weight 118 pounds. So with the thick walls and internal bracing, the thing is very inert. It goes deep, is very tight, and has serious slam. An audiophile friend of mine has told me that he thinks this sub is the best bass he has heard (though, admittedly, he has not heard a lot of high end subs). In a sealed enclosure it would not be as extended but I'm sure it would sound very tight and adequately deep. Recommended sealed enclosure for this PE 12" driver is about 3 cu. ft, but would be fine between 2.5 and 3.5, with only slight variations in Q resulting. The passive radiator design is probably also doable in your enclosure and would come out nearly on budget, but you would have to cut a hole for the active driver in the front of the cabinet and put the passive facing the floor. But using it without the passive in sealed enclosure would still yield in room response solid into the 20s, so that should be fine.

                        I also am using the same Dayton amp with a VMPS sub with a 12" woven carbon fiber driver (cabinet built by me). This driver is also available from VMPS but is more expensive than your budget. It is very accurate, fast and deep and in many subtle ways out performs the PE driver.

                        The driver Danny sells 'looks' descent, but I have never heard it. He apparently also used to sell a passive radiator that could be paired with it. It is nice of him to be offering the assistance he is, and if you used that driver I am sure it would be a very fine sub. I wonder how long it will be until the amp he is talking about will be available? I like the look of the amps he sells, and I wonder how the new amp for sealed subs is different from what he sells now? Maybe it offers some EQing to compensate for the roll off of sealed subs compared to ported or passive radiators?


                        • #13
                          Curious about that amp as well... I use the 600w version on my dual servo sandbox :)


                          • #14
                            Still liking that sandbox?
                            Originally posted by madpoet
                            Curious about that amp as well... I use the 600w version on my dual servo sandbox :)


                            • #15
                              Yep! Only thing is I want another one :) Once I got it tuned in with my SVS EQ1 it really changed how I think about bass. But I do on occasion miss the visceral punch to the gut.