DIY Sub Recommendation for beginner - AVS Forum
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post #1 of 11 Old 04-11-2013, 11:19 AM - Thread Starter
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I am looking for a summer project in the sub DIY area. I basically have no woodworking skills so was looking into the flat packs. Can anyone point me into the right direction as far as where to go for my very first build? I am looking to build at least a 15'' sub. I currently own a PSA XS30 (dual opposing 15") and would like to build a new sub to compliment my current sub. It doesn't have to be dual opposing as I am sure that is more difficult to build or find a kit for. I am not opposed to going up to an 18". Any suggestions would be greatly appreciated. I was looking in the $500 range but could adjust either way (within reason).

Thanks and look forward to your advice!

Room is 21L X14W X 8H. It is a living room, with a large opening to the kitchen, as well as opening to the upstairs.

DW
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post #2 of 11 Old 04-11-2013, 03:31 PM
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Well depends if your really hard set on that price point. The easiest way to get started would be getting any of these http://www.diysoundgroup.com/subwoofer-kits-1.html . All you have to do is assemble. If you wanted a little more customization (and more work) you can get http://www.diysoundgroup.com/subwoofer-flatpacks-2.html with an appropriate sub and an ep2k (ep2500 if you can find it) or ep4k. An SI HT 18", EP2k, and the 4cuft flatpack would hit ~$550 plus shipping and possible tax. I dont know if the flatpack's baffle is compatible with the SI but Im sure someone does.
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post #3 of 11 Old 04-11-2013, 04:16 PM
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if you build sealed, you will need some sort of eq, either stand alone or in the amp, to bring up the bottom end.

if you go dual opposed, watch your impedance. most drivers are 4 ohm and most plate amps are maxed at 4 ohm, so 2 drivers creates a less than ideal situation.

if you are looking to diy something like the xs30, you will probably end up spending around $350 for drivers, $125 for a flat pack, not sure where you can find a 750 watt amp with the proper eq, and then finishing. so probably around $8-900. with the xs30 at $1149, i'm not sure it is worth it to diy because who knows what you might miss in the process.

Listen. It's All Good.
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post #4 of 11 Old 04-11-2013, 07:43 PM - Thread Starter
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Thanks for both responses! Definitely not looking to go the dual opposed route...just something that goes down to about 20hz so I can play around with the second sub and placement. The reason I wanted to do a simple DIY is to see how everything works and if I can swing it, move up in the DIY world. If not, just stick to ID wink.gif. I would most likely try sealed to stay on par with the XS30 but not sure how I would EQ it.
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post #5 of 11 Old 04-12-2013, 02:23 PM
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Driver
http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-514
Amp
http://www.parts-express.com/cat/subwoofer-plate-amplifiers/332?sort=pasc
or if you really want DSP
http://www.madisoundspeakerstore.com/hypex-amplifiers/
Box
http://www.diysoundgroup.com/subwoofer-flatpacks-2.html

With a 500W non-DSP amp, parts prices range from $460 to $550 depending on amp and box size. A big sealed box results in a predicted freqeuncy response very similar to your current sub (they post measurements) and may reach low enough that room gain is all the boost you need. Conversely, the PE BASH amp allows you to select from a wide range of boost options, but it requires changing resistors on a PWBA.

I can vouch for the quality of the flat packs; I built their Anarchy tapped horn.

BTW, comparing Umax 15 and RSS460 in 4 cu ft. sealed at 400W...
- 460 is 2dB louder, but pushing Xmax to do it.
- Umax 15 digs about 2 Hz lower, 31 vs 34Hz F3, 18 vs 20Hz F10, with excursion to spare...

Lots of other, good quality DIY sub options out there at this price point. This one fits what you're looking for (and I love these Umax drivers!) but there may be others that fit well, too.

HAve fun,
Frank
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post #6 of 11 Old 04-12-2013, 05:30 PM - Thread Starter
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Quote:
Originally Posted by fbov View Post

Driver
http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-514
Amp
http://www.parts-express.com/cat/subwoofer-plate-amplifiers/332?sort=pasc
or if you really want DSP
http://www.madisoundspeakerstore.com/hypex-amplifiers/
Box
http://www.diysoundgroup.com/subwoofer-flatpacks-2.html

With a 500W non-DSP amp, parts prices range from $460 to $550 depending on amp and box size. A big sealed box results in a predicted freqeuncy response very similar to your current sub (they post measurements) and may reach low enough that room gain is all the boost you need. Conversely, the PE BASH amp allows you to select from a wide range of boost options, but it requires changing resistors on a PWBA.

I can vouch for the quality of the flat packs; I built their Anarchy tapped horn.

BTW, comparing Umax 15 and RSS460 in 4 cu ft. sealed at 400W...
- 460 is 2dB louder, but pushing Xmax to do it.
- Umax 15 digs about 2 Hz lower, 31 vs 34Hz F3, 18 vs 20Hz F10, with excursion to spare...

Lots of other, good quality DIY sub options out there at this price point. This one fits what you're looking for (and I love these Umax drivers!) but there may be others that fit well, too.

HAve fun,
Frank
Thanks Frank, that's exactly the kind of information I was looking for to get started. Now with some questions if you don't mind wink.gif. There was a 3 cubic foot flat pack for the 15 inch UMax. The 4 cubic foot was for the 18 inch driver. Would I still be okay with the 3 cubic foot flat pack or do I need to look at something else.
Also, as for the amps. Can you explain a little further why I would or wouldn't need DSP? I know these are basic question but I am a noob and have to learn some how....thanks again for your reply and assistance.
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post #7 of 11 Old 04-14-2013, 09:07 AM
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"460 is 2dB louder, but pushing Xmax to do it...."

the 460 has usable excursion to about 20mm or so. that gives about 3db advantage over the um at its 19mm, but who knows, that might be low too.

Listen. It's All Good.
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post #8 of 11 Old 04-15-2013, 09:56 AM
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Specs vs reality... both drivers are conservatively rated in this regard. PE's telling folks that Ultimax rating of 19mm is purely mechianical - gap and coil geometry. Klippel testing gives -15% BL points around 22mm and Xmech is 30mm, as I recall. I was trying to show a Hoffman's Iron Law trade-off, so I may have given the Umax extra leaway...

To OP,
DIYSound's flatpacks are "for" the driver cutout size. There's no reason the 4 cu ft box can't have a 15" driver cut-out, but he may not have it pre-cut. Erich's (best I can tell) a landscaper with an interest in audio who's been willing to act as an intermediary between a CNC shop and us audio nuts (and doing the same for horn/waveguide parts). You can always ask...

The reason has to do with "alignment," a fancy term for what kind of response the driver has, and power-vs-excursion.

"Alignment" of a sealed box depends on "Qtc" of the box-driver system. Q values relate to frequency response:
- Q=0.5 has great LF extension at the price of poor xmax control at the low end
- Q=0.7 has a very flat response and good Xmax control - our goal.
- Q=1.0 has a peaked response and reduced LF extension

Qtc depends on 1) the driver (specifically Qts - s for speaker), 2) the box size, through driver compliance (Vas), and 3) the density of fill or stuffing inside the box.

The Umax 15 driver sees a Qtc of ~0.7 when mounted in a sealed box ...
at 7.5 cu ft and no fill
at 4.5 cu ft and heavy fill

As we go smaller than 4.5 cu ft,
... at 4 cu ft and heavy fill, Qtc is 0.715 and F10 is 18Hz., and excursion at 400W is 19mm.
... at 3 cu ft and heavy fill, Qtc is 0.767 and F10 is 20Hz, and excursion at 400W is only 15.5mm, and the "peak" in frequency response is 0.1dB.
... at 1.25 cu ft and heavy fill, Qtc is 0.99, F10 is 26Hz, and there's a 1.25dB peak at 70Hz.

As you can see, it's a continuum; no sudden changes as Qtc moves, just regions that have differing response. The difference between 3 and 4 cu ft is peanuts compared with this driver's overall performance in either box. One just fits a little better...

HAve fun,
Frank
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post #9 of 11 Old 04-15-2013, 07:43 PM - Thread Starter
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Quote:
Originally Posted by fbov View Post

Specs vs reality... both drivers are conservatively rated in this regard. PE's telling folks that Ultimax rating of 19mm is purely mechianical - gap and coil geometry. Klippel testing gives -15% BL points around 22mm and Xmech is 30mm, as I recall. I was trying to show a Hoffman's Iron Law trade-off, so I may have given the Umax extra leaway...

To OP,
DIYSound's flatpacks are "for" the driver cutout size. There's no reason the 4 cu ft box can't have a 15" driver cut-out, but he may not have it pre-cut. Erich's (best I can tell) a landscaper with an interest in audio who's been willing to act as an intermediary between a CNC shop and us audio nuts (and doing the same for horn/waveguide parts). You can always ask...

The reason has to do with "alignment," a fancy term for what kind of response the driver has, and power-vs-excursion.

"Alignment" of a sealed box depends on "Qtc" of the box-driver system. Q values relate to frequency response:
- Q=0.5 has great LF extension at the price of poor xmax control at the low end
- Q=0.7 has a very flat response and good Xmax control - our goal.
- Q=1.0 has a peaked response and reduced LF extension

Qtc depends on 1) the driver (specifically Qts - s for speaker), 2) the box size, through driver compliance (Vas), and 3) the density of fill or stuffing inside the box.

The Umax 15 driver sees a Qtc of ~0.7 when mounted in a sealed box ...
at 7.5 cu ft and no fill
at 4.5 cu ft and heavy fill

As we go smaller than 4.5 cu ft,
... at 4 cu ft and heavy fill, Qtc is 0.715 and F10 is 18Hz., and excursion at 400W is 19mm.
... at 3 cu ft and heavy fill, Qtc is 0.767 and F10 is 20Hz, and excursion at 400W is only 15.5mm, and the "peak" in frequency response is 0.1dB.
... at 1.25 cu ft and heavy fill, Qtc is 0.99, F10 is 26Hz, and there's a 1.25dB peak at 70Hz.

As you can see, it's a continuum; no sudden changes as Qtc moves, just regions that have differing response. The difference between 3 and 4 cu ft is peanuts compared with this driver's overall performance in either box. One just fits a little better...

HAve fun,
Frank
Thanks for all the information Frank. I really appreciate you taking the time to school me on the basics! How do you come up with those QTC numbers? If you say the difference is peanuts then I may just stick with the 3 cubic foot box to start my first build.

I am still uncertain on the DSP and what that entails and whether to get a plate amplifier with DSP or a separate amp...
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post #10 of 11 Old 04-17-2013, 11:24 AM
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I'm using Unibox simulator, similar to WinISD and others. The difference is peanuts, but some people can't understand why they don't get to use all the excursion...

Some parametric EQ capability is useful in subwoofer optimization, once you've taken care of as many room mode issues as possible. The latter is important as you can't EQ out localized issues, only global ones (or for one seat).

MiniDSP is a multi-channel, line level parametric EQ and filter unit, plus other stuff (not real familiar). It allows you to set multiple filters, and it's ideal for subwoofers since you typically have a separate amp for each sub. You will also find some subwoofer amps have a PEQ feature, but only 1 filter compared with 4 or 8 in MiniDSP. In fact, that's the disadvantage; it may have far more capability than you need, yielding poor bang for the buck compared with even a single filter on an amp.

Have fun,
Frank
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post #11 of 11 Old 04-17-2013, 06:19 PM - Thread Starter
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Thanks Frank, again I truly appreciate you taking the time to help me to understand some of this information.
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