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Discussion Starter #1
Hi All,

I used the members' expertise in my HTR selection and appreciated the knowledge and can't afford anything in the way of equipment to improve my system further for a while, but I'd like to improve the sound, especially for home theater, from my DIY sub if at all possible.

I built a 20x20x19.5 down-firing, sealed external dimension box from 3/4" mdf some time ago for a Cerwin Vega HED-D1502 and it is powered by a bridged NAD 7150 Receiver (supposedly 160W) using the LFE out from my AV, mostly for home theater. I used nearly full-length 1.5"x1.5" wood strips glued and screwed at all edges, but no bracing. It seems quite solid (at least to me) and only has slight vibration imo. The CV specs are as follows:

4ohm dual vc
92 dB sens.
300rms power handling, 750 peak
0.15 ft3 spkr displacement
19hz Fs
0.60 Qts
11.18 Qms
0.63 Qes
17.3 ft3 Vas
+-0.67" Xmax

manu. suggested 1.9 ft3 sealed & dacron filled, 3.0 ft3 sealed (unfilled) (yea, I got that a bit wrong:no:)

Any help would be appreciated, especially in the way of inexpensive/non-labor intensive ideas.
 

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If the specs you posted are correct then there is nothing you can do to improve what you already have. Modeling show a sealed cabinet size of 49 cu.ft. for a Q of 7. :blink: Even in 20 cu.ft. the sub will exceed Xmax at 20 hz with 25 watts input power. Ported is not an option either. Your only hope is that the specs are wrong. You can contact Cerwin Vega Support and ask for the parameters. Hopefully they'll give them to you and they'll be a lot different from what you posted.
 

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Cannot find any specs for it except:
15" Dual Voice Coil Subwoofer
Titanium plated co-polymer cone
High energy strontium ferrite magnet
High temperature voice coil
RMS Power: 300 watts
Peak Power: 750 watts
Frequency Response: 20-500Hz
Sensitivity: 92dB
4 ohm impedance
V-Flex long throw suspension

Is the X-Max figure correct?
 

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Discussion Starter #6
Thanks guys for the quick responses. It's evident I need to brush up on my understanding of specs badly as I've forgotten the meaning of some. The speaker is a few years old with little use (and was inexpensive), but do you think I could salvage the box by cutting it down to size, and either close it up or place a port? I would like to get down toward 20hz for HT, and the SVS is looking far away right now, but if I could just improve it for the time being I'd be much better off as it is poor sounding in the current state.

Any suggestions?
 

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The Xmax is listed as peak to peak, it'll be 8.5 mm one way. The box you have now is about 3.5 cu.ft. internal. Here's some modeling of this sub.

Yellow is what you have now. It reaches Xmax with 150 watts.
Orange is 20 cu.ft. sealed. It reaches Xmax with 20 watts.
Pink is 15 cu.ft. tuned to 16 hz. It reaches Xmax with 40 watts.

Building a 15 cu.ft. box for a sub with 8.5 mm Xmax and low power handling is not something I would do. Some subs work well in home and auto applications. This one doesn't. It was meant for automotive use only.

HED.JPG
 

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Discussion Starter #10
Thanks Mike!

So is what you're saying (and the model's graph represents) is that this speaker doesn't really have the characteristics to play down low? I should probably just put it in a small tight box for my auto instead, eh?

Guess I better start saving...:spend:

I like building things, but I really don't need a new project anytime soon, and looking at the combined prices of a plate amp, speaker, and materials, it appears to me that building may be more for personal interest rather than savings or increased performance, perhaps I'm wrong on that. I read outstanding reviews on the SVS PB-10-NSD which gives up only 25W on the amp vs the 12" version, but would you recommend waiting longer for the 12" version in order to not miss impact or really low performance?

Thanks for all of your help.
 

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It will go fairly low in a large ported box but it won't get loud due to it's limited Xmax and power handling in that environment.
I should probably just put it in a small tight box for my auto instead, eh?
Or sell it if you have no use for it. Put the money towards something that will provide what you're looking for.

As for building your own sub, for the same price you can usually exceed the performance of a commercial sub. As for the SVS subs, the 12 inch version will have greater performance, at a higher price.
 

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Discussion Starter #13 (Edited)
Hey,

I've been looking at all of my small bookshelf speakers and receivers around the house and while looking at cylinder speakers began wondering if they really are inexpensive and simple to build. I only found this size locally online (12" dia x48")
http://www.lowes.com/lowes/lkn?action=productDetail&productId=10150-286-692203&detail=&lpage=none
(only about $12 in case the link doesn't work)

*Correction: local supplier sells 18" and 24" dia tubing in 1 ft increments for $4-6 /ft, so I could use a 12" driver and orient it vertically. Came across this guy's old project: http://www.hometheaterhifi.com/volume_6_3/diy-11-sonotube-subwoofer-september-99.html#end-caps
Perhaps someone could suggest a different 12" driver, as the Hsu is no longer available...


I would be interested in placing it horizontally on the floor if possible, behind the couch where it would be unseen. Not sure how it would sound oriented this way, but it could fire into a corner. I would use the same aforementioned NAD bridged amp with it.

Could a reasonably priced hard-hitting 10" driver be placed in one of these with good results? Price of driver would need to be <$200 to my door, something like the Parts Express 10" Titanic perhaps?http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-414&ctab=1#Tabs

If anyone has build such a speaker, please leave a link!:bigsmile:
 

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Discussion Starter #15
The NAD will supposedly provide 160W bridged, which I expect to be clean power into 4 ohms though it is an old unit. Don't know how SVS tooled a plate amp into the side of a tube, but that would be a consideration later, if possible, as I'd like the auto on feature.

My other option for power would be using my old pioneer vsx-d508 receiver (100W/Ch 8 ohms ea) to drive one, or even two of these built cylinder subs, but the manual states to use 6-16 ohm speakers.

My primary goal is to hear what I've been missing, with accuracy prized secondly, and then volume (who wouldn't like to feel the impact?). I played a couple dvd's on the HTS site and...my system is currently really poor:hissyfit:
 

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I have a pair of Cerwin Vega VMAX 15.2's that I plan to integrate into my home theater at some point. The spec sheet I pulled from CV's site drives WinISD a little crazy. So I'm not sure the specs are accurate. I'm a little worried about this since it will be hard to accurately spec and build a box with incorrect numbers.

Brad
 
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