Hello,
I'm a total noob trying to put together a diy active subwoofer. A really cheap one. I have spent the better part of today scouring the internet and learning about all the different paramaters and characteritics of amplifiers, speakers and enclosures, but in the end I can't manage to determine a reasonable volume for the enclosure and I need some help.
I found these speaker:
Tiefton-Chassis MHB-12 TSP – #360customs
Yes, I know it's really cheap and probbably not very good (read "lousy"), but I thought it'll do for starters. There is a data file for the speaker for WinISD on this site also.
I plan to use this amp and build it into the enclosure:
Ethics Sound SubWoofer Audio Plate + DIY Platform to Customized your Active Home-made Subwoofer | Lazada Malaysia
Did I already mention I'm going for cheap 🙂?
I tried to use WinISD and this online calculator Speaker Box Enclosure Designer / Calculator to determine the needed box volume,
but I'm unsure what qtc I should aim for. A lot of posts talk about a qtc of 0,707 as optimal, but that is obviously not possible with the chosen speaker. Is that because it is shitty? Or is it not meant to be used in an enclosure by design?
I tried experimenting a bit and with a qtc of 1,5 for example (I don't know what that would mean in practice, it's just a number I put in) the required volume would be around 150l. That's a calculation for a selaed box, since another tool on that site suggested a sealed box for the choosen speaker, not a ported box.
When I import the data file of the speaker into WinISD, the volume required for a sealed box is displayed at around 738 with a qtc of 1,182. And that's quite a big box.
Can anybody give any suggestions? And preferrably not get a better speaker and/or amp 🙂. What size of box would fit? Or to put it another way - what qtc would still be acceptable?
I'm a total noob trying to put together a diy active subwoofer. A really cheap one. I have spent the better part of today scouring the internet and learning about all the different paramaters and characteritics of amplifiers, speakers and enclosures, but in the end I can't manage to determine a reasonable volume for the enclosure and I need some help.
I found these speaker:
Tiefton-Chassis MHB-12 TSP – #360customs
Yes, I know it's really cheap and probbably not very good (read "lousy"), but I thought it'll do for starters. There is a data file for the speaker for WinISD on this site also.
I plan to use this amp and build it into the enclosure:
Ethics Sound SubWoofer Audio Plate + DIY Platform to Customized your Active Home-made Subwoofer | Lazada Malaysia
Did I already mention I'm going for cheap 🙂?
I tried to use WinISD and this online calculator Speaker Box Enclosure Designer / Calculator to determine the needed box volume,
but I'm unsure what qtc I should aim for. A lot of posts talk about a qtc of 0,707 as optimal, but that is obviously not possible with the chosen speaker. Is that because it is shitty? Or is it not meant to be used in an enclosure by design?
I tried experimenting a bit and with a qtc of 1,5 for example (I don't know what that would mean in practice, it's just a number I put in) the required volume would be around 150l. That's a calculation for a selaed box, since another tool on that site suggested a sealed box for the choosen speaker, not a ported box.
When I import the data file of the speaker into WinISD, the volume required for a sealed box is displayed at around 738 with a qtc of 1,182. And that's quite a big box.
Can anybody give any suggestions? And preferrably not get a better speaker and/or amp 🙂. What size of box would fit? Or to put it another way - what qtc would still be acceptable?
I've got a similar driver I'd happily send you for free, but the postage would be a killer.
It was in a ported box, and the high Q gave a pronounced M-shaped frequency response. It still sounded OK when set up right and crossed low enough.
1) what about salvage - see if you can rebuild or pull parts from a damaged / cheap speaker.
2) buy something European. I doubt the amp will still be good value after you pay for shipping from Malaysia.
Maybe a little of both. A car or leaky enclosure might be ~ideal. If you could mount it in an window, doorway or similar (LOTS of duct tape), you'd have an infinite baffle, and you'd be hitting the cheapness target.
It was in a ported box, and the high Q gave a pronounced M-shaped frequency response. It still sounded OK when set up right and crossed low enough.
1) what about salvage - see if you can rebuild or pull parts from a damaged / cheap speaker.
2) buy something European. I doubt the amp will still be good value after you pay for shipping from Malaysia.
Maybe a little of both. A car or leaky enclosure might be ~ideal. If you could mount it in an window, doorway or similar (LOTS of duct tape), you'd have an infinite baffle, and you'd be hitting the cheapness target.
Scroll down to fig. 7 to see a Qtc chart that shows how it describes the speaker cab's roll-off frequency response, i.e. 0.707 = max flat [widest] bandwidth [BW] with < 0.707 = over-damped ['tight', 'fast', rolled off response] and > 0.707 = under-damped ['loose', 'flabby', 'ringing' response]: http://www.readresearch.co.uk/thiele-small_papers/smalls_closed_box_article_1.pdf
As already noticed/noted, the lowest Qtc = Qts and the largest cab, so the driver's high 'Q-ness' requires a lossy/leaky cab to 'bleed' it off with the smaller it is the more damping [stuffing] will be required to knock down its mid-bass 'hump' in the response. You may recall that old radio, stereo consoles normally were either open back or had a pegboard or other means of both venting the electronics as well as the high Qt [weak motor] drivers.
Otherwise, the noted 'infinite' baffle [IB = Qtc = Qts] or the popular large flat baffle open in the back [OB = 0.5 Qtc].
Another very popular option often used by manufacturers and DIYers with severe size restrictions is the Linkwitz-Riley Transform ckt. [LRT] that electronically EQs [reshapes] the output of a too small sealed box by trading [a lot of] efficiency for a wider, flatter BW. No clue about cost to buy or DIY.
Well, all things considered and assuming you don't want to mess with a LRT, then the smallest practical cab I would use is around Vas/1.44 = ~92.16 L net and [heavily] damp to 'taste'. 😉
GM
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Thanks for the respones guys!
I have second thoughts now about investing my time into building something that really isn't all that useful in the long run.
Maybe I'll just wait a year and buy a reasonable driver and than build the matching enclosure for it.
I actually do have an old unused passive subwoofer from a home cinema, but it is a really cheap one. My initial plan was getting a cheap amp of some kind to power the old subwoofer for a while, until I can get a better one. And than I thought I'll just buy the amp backplate I linked above and attach it somehow to the old subwoofer. And than I thought if I go that far, why not build a completely new subwoofer. And than I spent a day researching all of this, and found out a day is not nearly enough to understand it. 🙂
Well, thanks for the responses, I'll think a little bit more about what to do.
I have second thoughts now about investing my time into building something that really isn't all that useful in the long run.
Maybe I'll just wait a year and buy a reasonable driver and than build the matching enclosure for it.
I actually do have an old unused passive subwoofer from a home cinema, but it is a really cheap one. My initial plan was getting a cheap amp of some kind to power the old subwoofer for a while, until I can get a better one. And than I thought I'll just buy the amp backplate I linked above and attach it somehow to the old subwoofer. And than I thought if I go that far, why not build a completely new subwoofer. And than I spent a day researching all of this, and found out a day is not nearly enough to understand it. 🙂
Well, thanks for the responses, I'll think a little bit more about what to do.
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