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Discussion Starter #1
My last thread turned out to be a feeler and was instrumental in getting me back into the "know". But I've got some actual specs now and need to narrow down my driver choice.

My previous thread:
http://www.hometheatershack.com/forums/diy-subwoofers/15810-10-small-enclosure-hmmm.html

My project almost exactly mimics this on a smaller scale:
http://www.hometheatershack.com/forums/diy-subwoofers-sealed-ported/6303-diy-subwoofer-would-like-some-feedback.html

So, check out the rough drawing I made. The top will be 22"x16"x16" to keep the math simple. It'll be 20" high and top-firing with whatever port recommendation y'all think is best. The numbers put it at about 1cuft all said and done calculating for the volume of the materials and ports. WinISD calls for a 3"x14" to get me 30hz for most of the 8" subs. The pic below shows 2x2" ports, but I'm thinking a single 3" wins.

So, back to driver and amp selection.
It'd be easy to go with the Dayton RefHF 8" and the 240watt plate amp and call it a day. At under $250 shipped for the amp/driver/terminals... it's a frontrunner. For an extra $100, Soundsplinter sells an 8" driver, but not sure it's $100 better. Any other 8" drivers I should consider in the $100 pricerange that might be a better deal than the Dayton?

Thanks for the help!

Pics are of initial design, space behind TV, front of TV.
 

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The Soundsplinter doesn't model well in 1 cu.ft. from what I can remember, plus it's out of stock. CSS has a new 8 inch sub, the TRIO8, it has a lower Fs then the Dayton, has a Xmax of 14mm, and is $95 shipped. I'm at work and can't model it at the moment. Try modeling it and see how it does.

http://www.creativesound.ca/pdf/CSS_TRIO8.pdf
 

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I did some modeling of the subs. The problem with the 240watt plate amp is it has a rumble filter at 18 hz and both subs will bottom out below 22 hz. If you were to use the Bash 300 amp, the rumble filter can be changed to 25 hz and both subs would be protected. The Dayton is a 4 ohm sub and the CSS is a 8 ohm sub. The Dayton will take 80 watts to reach Xmax. The TRIO 8 will take 150 watts to reach Xmax and has much more output.

TRIO 8.JPG
 

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Discussion Starter #4
Mike, you are the man. I guess that settles it. The Trio+300watt Bash.

I did some playing around with different ports... it looks like a single 3" will need to be 19" long, and 2x2" will be 17". For simplicity, I'd like not to have to engineer any curved ports, so just a straight piece is necessary.

If I made the box just a couple inches taller and got the box size up to about 1.2cuft, then the port length goes down to where the end of it isn't resting on the bottom of the box... plus a little more volume can't hurt, right? If I absolutely must keep the box small, and must use an elbow to get the port length, will I have velocity problems with 2x2" ports... or is a 1x3" port recommended in this design?
 

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The following is only if you want to build a 'premium' level of subwoofer with outstanding performance.

If you really want the most output from a tiny sub, are willing to spend more, will use a little bit bigger box(to accommodate the slot port) and want another level of performance, it will be difficult to impossible to beat the JL W7 8". In 1 cubic foot + appropriate folded slot port of 7" wide x 2" high x 44" long. Combine with O Audio 500 Watt BASH amplifier. A weaker amp is not recommend for this driver. Also, the subsonic filter is important on the O Audio for the safety of any ported sub used for HT purposes. You will achieve ground plane 2 M output, realistically, around 105dB at 28Hz, 107db by 40Hz. This is accounting for some thermal compression and port compression. The modeled SPL is actually quite a bit more, but I try to give more realistic performance numbers based on real world factors. Realize, the W7 will have less thermal compression and more linear excursion when compared to most anything else. I tried to select the smallest possible port for compact size, and some compression is occurring as a result.

BTW, the factory specs for 8W7 are way off on VAS. I have tested 2 different pairs from two different production runs and they are consistent, both with VAS nearly 1/2 of what factory spec indicates.

The 8W7 is about $250 from online discount sellers. The only comparable 8" I know of is the now unavailable TC Sounds built one sold by Sound Splinter. However, as was said earlier, it may not be suited to such a small volume. The driver can safely operate at high SPL to about 20Hz in a 1.5 volume ported cabinet! It is a rather amazing 8" driver with extreme thermal capability and incredible linear excursion. I can say that in my use in sealed applications, the one way 19mm xmax is a conservative rating I suspect. Photo of 8W7 from rear.

Here are the actual T/S parameters measured from an 8W7 for modeling purposes:
Qms: 7.765
Qes: 0.734
VAS: 0.326 ft^3
Re: 2.78
Le: 1.34 mH
BL: 10.39
Xmax: 19 mm
Pe: 500 W
 

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I'm getting different port lengths then you are. A 3 inch port would be 22 inches long and two 2 inch ports would be 20 inches long. Both WinISD and the P.S.P. port length calculator say the same thing.

http://www.psp-inc.com/

Also, changing the high pass filter to 25 hz involves changing 2 resistors on the amp board.(R26 and R25) If you're not comfortable doing this you'll have to find someone who is.

Bash 300.JPG
 

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elemental designs has a 8 incher that meets your requirements. i've alway liked their subs. i'm running a 16kv.2 for my sub right now. the new 8 is $95 gives a 14mm xmax. its the same series as my 15, only new cone. i can't posts links yet so you'll have to look it up.
 

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Discussion Starter #8
WmAx, thanks for the thought, but your idea doubles my price point, and I'll need that for decent set of small bookshelfs. It might be a future idea if funds are plentiful and space is still limited.

And now I'm back and forth about making the triangle 1/2" longer on each side and squeezing a 10" in there. I keep telling myself it's just for a 2.1 system to impress my friends with... but you know how that goes.

Mike, thanks for the link to the port calculator... I'll go back and see what I was doing wrong.

Thanks,
Sam
 

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And now I'm back and forth about making the triangle 1/2" longer on each side and squeezing a 10" in there. I keep telling myself it's just for a 2.1 system to impress my friends with... but you know how that goes.
What about moving the TV a little to the front so you can have more space in the back??? :hide:
 

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Discussion Starter #10
What about moving the TV a little to the front so you can have more space in the back??? :hide:
That is absolutely an option... but one I was saving as a last resort. I'd really like the edges of the TV stand to mate with the wall, but to get the size of enclosure I'm looking at, it seems I'll have to move it forward a bit, leaving a gap. I think I can go a little taller on the enclosure to get a little more volume in the box, but that doesn't help me with overall size of the top of the box I have to mount the driver in. I think I can max (absolutely the biggest I can go) and squeeze a 10" driver onto the top of the nox... but that'll necessitate a larger box, bigger port, larger amp... and I'm back where I started with the wife mad at me for yet another "project that dominates the room".

Any of the hi-Xmax 10" drivers out there and the 300watt BASH amp will do more than I need, so I was hoping to just do an 8" driver... but it looks like there's no reason not to do a 10" considering I have the space, but just don't to use it.

Decisions... decisions... decisions....
 

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Discussion Starter #12
Mike I've been examining the space behing my TV and running some dimension calculations... and the overall dimensions of the wedge are pretty fixed since I can only pull the TV stand out so far from the wall. If I pulled the stand out from the wall as far as could be considered aesthetic, and jammed the sub up against the wall, it would be about 26" inches on the face... which (assuming a 90* right triangle) mean the sides are in the 18" range. That would allow me the room for a 10" driver on top and result in a maximim of 1.5cuft.

That definitely gets me into the realm of 10" drivers... but I honestly don't need to shake the whole house just to watch Seinfeld re-runs. Running an 8" driver makes way more sense and fits the overall bill nicely. Of course I'll run a 10" driver if there's a way to make it fit in a super-small encolusure... but I just don't think it's required here (then again... I'm as bass hungry as the next guy).

-Sam
 

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You could always consider a low displacement 12 like the Fosgate P3 Shallow for caraudio. It takes up very little space and its fairly musical
 

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Update... like all good ideas, success lies in the execution. After spending much time modeling and researching, it made zero financial sense to make myself a sub. I searched Craigslist and eBay for a few weeks and ended up buying an entire Energy Take-5 Classic 5.1 w/brackets for $100 a used 8" Mirage sub for $40 and tried out both subs in the space behind the TV. Both fit perfectly, and I could get the TV stand as far back as I needed it to go and the subs both fit like gloves.

I couldn't be happier with the results... and although I don't have the talking points I would with a 10" custom sitting back there all stealth and rocking the whole house, I have no regrets. My next house (Navy moves me every 2-3 years) will have a dedicated HTR so I can get back into the hobby and I WILL GO ******** HUGE! I'm set for now though.

The picture is of the original test fitting... that mess of wires no longer exists (yup, just my ego reassuring you guys I'm no slob).
 

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Have you considered an isobaric design? When working with small spaces I have had really good success with iso loading two woofers.

Matt
 
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