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  • low budget sub with passive radiator need help with mass , box size and stuffing

    so i just build a 17x17x17 cube with .625 mdf and i ordered

    1 269-519 Bravox PXW10D-2 10" DVC Subwoofer 2 Ohm Per Coil $49.80 4 ohm series
    1 261-610 Black Ash Vinyl Laminate 2 ft. x 18 ft $18.00
    1 295-496 Dayton Audio SD315-PR 12" Passive Radiator $34.25

    1 bash 300s on sale for 99$ and i have some questions, because honestly, ive gotten like 6 different answers from the tech guys at parts express that are so radically different its actually scary.

    i realize this is a low budge sub mostly just for the fun of building something new, ( i have my own awesome HSU research sub )

    its going in my gfs apt for low end fill in mostly.

    internal volume 2.26099 and i have 20 ounces of poly fill to add if needed so im assuming i can increase the size by 1.4x if need be, internal displacement around .12, bash amp in seperate enclosure.

    A. can i place the sub in front and the passive in the rear, with the passive facing us, any idea on if i should add mass to the PR or try it standard, i was going for a tuning freq between 24-29 hz , would a bigger box or smaller box be better, i have 2 pairs of tower speakers with triple 5.25s in each so the base to 45hz hits nicely, any thoughts on this design? im taking a gamble, instead of going with the standard sealed or ported box. any thoughts would be appreciated, but please be gentle if you think it will suck lol, im hoping the bravox will turn out to be halfway decent, especially for the price tag. this is a budget sub mostly to try and play low bass and not loud. thank you sirsClick image for larger version

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    jason

  • #2
    Re: low budget sub with passive radiator need help with mass , box size and stuffing

    This is going to be 1 of those 'it depends' answers.

    Depending on if you have Excel available to you, you could download Unibox and be able to model different alignments for yourself. http://audio.claub.net/software/kougaard/ubdwnld.html

    Otherwise, your design as you have it actually looks fairly good.
    With no extra mass, the response is flat with your f3 at about 31Hz, capable of about 98dB if content stays above about 18Hz.

    However, if you wanted more LF extension, going vented in a bigger box (~3.5cuft), f3 is about 25Hz. Max SPL about the same.

    You could also load the PR up with about 300g of mass to extend the LF, but now, instead of being flat, the response starts falling at about 100Hz but it falls more slowly so your f10 is now down to about 20Hz. This version however loses maybe 5 or 6 dB in terms of max SPL.

    At least, this is what Unibox suggests. Hope that helps.

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    • #3
      Re: low budget sub with passive radiator need help with mass , box size and stuffing

      I would add 100g mass. It will tune you to 25hz with that being the -6 db point. The bash amp has some boost in the 30hz range which should work pretty well with this setup.

      300 watts is WAY to much power for this setup by the way...
      http://jaysspeakerpage.weebly.com/

      Comment


      • #4
        Re: low budget sub with passive radiator need help with mass , box size and stuffing

        I like what you did with the Bash....is that a standard 6x9 box? If it's not too late I would let PE keep the Bravox and get the Infinity 1260W from Amazon.
        Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
        Howard H

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        • #5
          Re: low budget sub with passive radiator need help with mass , box size and stuffing

          it turns out the box ended up being 17x17x18 which is 2.404, multiple that by 1.4 with the poly fill =3.36. id love to have a f3 of around 25-27 from the winisd program i ran, if i can add mass to the PR and get it even lower, thats even better. as for the bash amp being too much power, it was on sale for 99$ and i couldnt pass that up, the dayton audio plate was 59$ for the 70 watt or 89$ for the 100 watt or 36$ for the 25 watt, it was just too good of a deal to turn down, so ill run the gain way low, the bravox has a 87 sensitivity and is rated for 200 rms 400 peak. that and i might take this bash amp in a year or so and put my old jl audio 12w6 in a 12x40 sonotube with a 4 inch port, 2 feet long flared at both ends. better to prepair for the future right? i remember my old orion 12 in highschool had an xmax of like 6 in a 2 foot cubic foor sealed box with 2 pounds of poly fill and could hit 120db at 20hz, that was a sweet sub. the guys at PE actually told me not to make the box any bigger or the sub would flop around, of course i talked to about 6 different techs each of them giving me a different answer proving to me that none of them have a clue what they are talking about when it comes to building speakers if their box programs dont work, and keep in mind, this is just an learning experiment for fun, the total cost is about 180$, i do have some andrew jones pioneer towers speakers with 3 5.25s in each and a yamaha rec, and they actually hit hard, so i just want some bottom fill. cross your fingers, at least the box looks nice lol, and i finally get to try a 12pr. i could always return the 10 and get a better one if its not strong enough, 45 day policy, thanks for the feed back. i cant wait to test it.

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          • #6
            Re: low budget sub with passive radiator need help with mass , box size and stuffing

            yeah, ive had those boxes for like 15 years in the closet, i had to cut the hole out a bit for it to fit, but now i can use it to test out other subs i build. ive got 45 days to return the bravox sub, infact the new one and PR havent even shipped yet, how much is the infinity from amazon? and im not going for spl, just decent sound for cheap to fill in low end. i have an awesome HSU research sub in my apt that im not using because its too loud, this is for my gfs apt , and she wont let me bring my " real " stereo over lmao

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            • #7
              Re: low budget sub with passive radiator need help with mass , box size and stuffing

              Originally posted by Jay36sub View Post
              it turns out the box ended up being 17x17x18 which is 2.404, multiple that by 1.4 with the poly fill =3.36.
              i think 1.4x is a pretty generous figure for a little over 1 lb of polyfill in a 2.4 ft3 box. you might want to reconsider that assumption. but 2.4 ft3 is a good starting point anyhow.
              TM (RS125/TB25-302), TM RS150S / Vifa BC25SC06, RS150-4 / Vifa ML-TL, 3CR-AL Ultra Budget: Electric Blue TM, TMM, MTM, Dragonflies , Mounties: Mini HT Satellite,sub for minions

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              • #8
                Re: low budget sub with passive radiator need help with mass , box size and stuffing

                20 ounces plus, i could even add more if need be, man im sitting here thinking, would i have been better off keeping the 29$ bravox 10 buying a second one , running them isobarick for added mass, with the PR, instead of getting the 59$ higher end one....... the main reason i did was higher xmax, and a qts of .40 the low end bravox had a qts of .66 and was more for spl. the originals were dual 4 ohms, so i could have ran a series , than parallel for a 4 ohm load, good news is, that bash confirmed to me in an email that the 300s is 3 ohm mono stable, so will work in the future with my brand new 12w6 old school still in the box.

                http://www.soundsolutionsaudio.com/f...g-of-polyfill/


                1. If the enclosure is less than 2.5 - 3.0 cubic feet in size, you should use no more than one and a half pound of polyfill per cubic foot available in your enclosure.
                2. If the enclosure is greater than 2.5 - 3.0 cubic feet in size, you should use no more than one pound of polyfill per cubic foot available in your enclosure.

                Specific examples of polyfill's effects on various enclosure sizes (with varying amounts of polyfill in each size) can be found in The Loudspeaker Cookbook by Vance Dickason or in an article written by Tom Nousaine for the March/April 1995 edition of "Car Stereo Review".

                Stuffing a box with polyfill makes it seem larger and it all relates to thermodynamics. When polyfill is added to an enclosure, it changes the behaviour of the airspring in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" implies that there is no heat transfer occurring. An isothermal process occurs once the polyfill has been added. As the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the airspring to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Being that sound passes easier through a denser medium, the speaker interacts with your enclosure as if it is larger than it actually is. The effective increase in enclosure size can be as much as 40%!

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                • #9
                  Re: low budget sub with passive radiator need help with mass , box size and stuffing

                  Originally posted by Jay36sub View Post
                  .... how much is the infinity from amazon? ....
                  $60 free shipping, and it would embarass the Bravox.

                  http://www.amazon.com/Infinity-Refer...infinity+1260w
                  Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
                  Howard H

                  Comment


                  • #10
                    Re: low budget sub with passive radiator need help with mass , box size and stuffing

                    Has anyone told you that with unbraced 5/8" panels that size, you're bound to have box resonance issues? It throw at LEAST one 3/4" to 1" dowel brace in their on each axis (side to side, top to bot, etc.) Two (staggered) would be even better.

                    Comment


                    • #11
                      Re: low budget sub with passive radiator need help with mass , box size and stuffing

                      ok specs wise the infinity looks like it would crush the bravox, xmax, is almost double, lower fs, and qts, im not sure what box size it needs though, and what about my passive radiator then, a 12 inch woofer with xmax 13 and PR thats a 12 with xmax of 10mm, im not sure if the infinity would like a 2.4 sealed box, then add in the displacement, and a brace, i was thinking i could get away with out that since i dont plan on driving this set up very hard, personally ive never used inifinity, i know at one point many many years ago they were good, but i dont have a high opinion of them as a sub, ie i would never choose that for a car subwoofer. so far PE hasnt shipped any of my new order, i might be able to cancel it cept then im paying 38$ pr, 18$ covering, 16$ shipping and handling, it almost seems like its not worth it , and its a 12, wouldnt i need an an entirely different PR for use with this 12? or even something like 2 tens? which just raises the cost of this more and more. hmmm decisions, decisions. if it vibrates, ill add a brace, ive built a bunch of subs before and never had that be an issue.

                      i dont think the bash amp will be able to drive the infinity to the point of using the extra xmax over the bravox, remember im only working with 300 watts rms here, i could put a 500$ sub in the box and would it sound better with the same small amp? i do noticed the efficiency rating though being much better.

                      Comment


                      • #12
                        Re: low budget sub with passive radiator need help with mass , box size and stuffing

                        ok so i broke down and ordered the infinity sub for 59.99 had 25 cash back on my dsc card which made it even cheaper, i just couldnt ignore the specs, 93 db, 13 mm xmax, and the freq response, not to mention the non stop 5 star reviews on amazon about this sub and how awesome it is for the money, so thank you who ever brought that to my attention. so i ups the first 29$ bravox back to PE and it cost 17$ lol, i know i could have shipped it from work for like 8 bucks, great job office depot, and now i have to ups return the second bravox 49$ sub back to them as well, argh this started out as a simple cheap sub but it just keeps spiraling out of control, although the infinity tier 2 tech support guy was awesome and totally knew what he was talking about and thought my idea of using the inifinity sub (12) with the dayton 12 PR was an awesome design, given that i have to play around a little with the poly fill and the weight on the dayton, cant wait for all this to get here. still though, im not sure about the box, its 2.4 without taking into consideration the driver displacement ( amp is in separate box ) and a possible cross brace since someone in here got me worried the box will either rattle or flex do to pressure. how much poly fill should i add, i have 20 ounces right now, should i go for 36 ounces ( 2 pounds ) in the 2.4 box, im shooting for a tuning freq from 23-29 and its kinda hit or miss how i achieve that. also, i have some left over dynamat from my trunk that was never used ( enough to cover about half the panels in the box) any one think that would do any good on the inside of the box or hurt it?

                        Comment


                        • #13
                          Re: low budget sub with passive radiator need help with mass , box size and stuffing

                          1 12 inch driver with 13mm of Xmax should be paired with 2 12 inch PRs with 16 to 20 mm of Xmax each. ROT for PRs is to have 2 to 3 times the Vd of the driver. This is usually in a somewhat smaller than normal SEALED enclosure for the driver.

                          I think you will be hitting Xmax of the PR with a LOT Less than your 300w amp can deliver. tuning is accomplished by adding weight to the PR.

                          Comment


                          • #14
                            Re: low budget sub with passive radiator need help with mass , box size and stuffing

                            300 watts will drive the infinity 1260w to xmax.


                            Originally posted by Jay36sub View Post
                            ok specs wise the infinity looks like it would crush the bravox, xmax, is almost double, lower fs, and qts, im not sure what box size it needs though, and what about my passive radiator then, a 12 inch woofer with xmax 13 and PR thats a 12 with xmax of 10mm, im not sure if the infinity would like a 2.4 sealed box, then add in the displacement, and a brace, i was thinking i could get away with out that since i dont plan on driving this set up very hard, personally ive never used inifinity, i know at one point many many years ago they were good, but i dont have a high opinion of them as a sub, ie i would never choose that for a car subwoofer. so far PE hasnt shipped any of my new order, i might be able to cancel it cept then im paying 38$ pr, 18$ covering, 16$ shipping and handling, it almost seems like its not worth it , and its a 12, wouldnt i need an an entirely different PR for use with this 12? or even something like 2 tens? which just raises the cost of this more and more. hmmm decisions, decisions. if it vibrates, ill add a brace, ive built a bunch of subs before and never had that be an issue.

                            i dont think the bash amp will be able to drive the infinity to the point of using the extra xmax over the bravox, remember im only working with 300 watts rms here, i could put a 500$ sub in the box and would it sound better with the same small amp? i do noticed the efficiency rating though being much better.
                            I was so much older then, I'm younger than that now.
                            OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                            Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                            Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                            Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                            LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                            Comment


                            • #15
                              Re: low budget sub with passive radiator need help with mass , box size and stuffing

                              Happily with Woofer Box and Circuit Designer, you don't need ROT, you can actually model the driver and the PR(s) and figure out if it will work. Might even find out that the ROT isn't so ruley.

                              Originally posted by MGrant1957 View Post
                              1 12 inch driver with 13mm of Xmax should be paired with 2 12 inch PRs with 16 to 20 mm of Xmax each. ROT for PRs is to have 2 to 3 times the Vd of the driver. This is usually in a somewhat smaller than normal SEALED enclosure for the driver.

                              I think you will be hitting Xmax of the PR with a LOT Less than your 300w amp can deliver. tuning is accomplished by adding weight to the PR.
                              I was so much older then, I'm younger than that now.
                              OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                              Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                              Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                              Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                              LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                              Comment

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