CurtPalme.com Home Theater Forum

tri_joel · Joined: 03 Jul 2007 Posts: 646 Location: Northern Virginia

ecrabb · Posted: Fri Mar 18, 2011 3:50 pm Post subject:

**AnalogRocks** · Posted: Fri Mar 18, 2011 4:44 pm Post subject:

I like this one:

http://www.avsforum.com/avs-vb/showthread.php?p=11887670#post11887670

ecrabb · Posted: Fri Mar 18, 2011 4:48 pm Post subject:

Yeah, that one's friggin' awesome if you have the right space for it. Another guy used the same design and did one with a different color scheme that was also pretty kick-ass.

SC

ecrabb · Posted: Fri Mar 18, 2011 4:52 pm Post subject:

Oh and in case anybody is wondering how big these really are, my daughter Kaylee is a little over 48" (122cm) tall.

SC

ecrabb · Posted: Fri Mar 18, 2011 4:57 pm Post subject:

Oh, and I got the bracing finished last night!!!

So, I still have to drill the holes for the grille mounts, I have to do a little more filling and sanding, and I'll be ready to prime and paint!

Thinking about some kind of simple 2x4 frame I can whack together in five minutes to screw onto the saw horse to hold the subs while I paint them... Thinking about one long 2x4, with two small "uprights" (like a football goal-post), but with two posts on the bottom instead of one... Something like that, anyway.

SC

tri_joel · Joined: 03 Jul 2007 Posts: 646 Location: Northern Virginia

Looking good Steve.

Are those braces screwed in addition to the glue and finish nails?

For painting, I drive 3" screws 1" deep into the top of my saw horses and then set what ever I'm painting on the screw heads. If you're spraying then it's pretty easy to get full coverage on the bottom without moving them. Just touch-up the small point where the screw heads contact the cabinet.

ecrabb · Posted: Fri Mar 18, 2011 5:25 pm Post subject:

No, no screws anywhere in the cabinets, Joel... Think I'll regret that? I tested a scrap piece that was nailed and glued and it seemed strong as hell. Each of the braces is glued (very liberally - you can see all the glue), and I shot two 1" brads through each (so about half an inch of brad in both brace and cabinet MDF. Each of the angled braces have a glued contact patch that's about 1.5 x 2.125 or over 3 sq inches of glued surface on each end. I'm not exaggerating when I say I think I could hang the entire cabinet by one of those braces. It sure feels solid!!!

Good idea on the screws in the saw horses... Duh! I'm even putting feet on them, so if I locate and mark the feet locations and put the screws in the same places on the saw horses, I shouldn't even have anything to touch up! Total duh! Might have to pick up a fourth saw horse so I can do two at a time, though. I've always wanted another one. Off to Menard's after lunch... Wink

SC

tri_joel · Joined: 03 Jul 2007 Posts: 646 Location: Northern Virginia

Standard wood glue does not bond to the paper face of MDF or end grain of SPF. I would run a screw in each one if it were mine. Since you are not done filling and sanding, just run a screw from the outside, counterbore for the screw head, and fill it with bondo. I over engineer everything though, my concern would be the constant vibration eventually breaking a glue joint loose.

If you're going to locate the painting screws where the foot screws will be - just drive your painting screws into the cabinet where the feet will go and put the whole enchilada on the saw horses.

dturco · Posted: Fri Mar 18, 2011 7:34 pm Post subject:

If you going to spray them make a pinata. Get a 2x4 slightly larger then the speaker opening place it into the speaker opening turn it then use a chain to hang it from the rafters if you can, or around the garage door tracks near the end where the struts bolt to the ceiling. If your spraying. If using a roller or brush the screw idea is the way to go.

OK even if spraying, the screws are a really good idea too.

jcmccorm · Joined: 15 Jan 2008 Posts: 21

Thanks for all the info guys! Plenty to keep me busy!

ecrabb, after poking around a bit and seeing some of the more "esoteric" DIY speaker projects, I see what your saying about your own project, but you're still being modest and selling yourself short. You're building your own speaker man! That takes skill, and cajones.

Cary

-Pjackso · Joined: 31 Mar 2006 Posts: 791 Location: Oklahoma

Did you use a speaker building software to design the box? (box size based on T/S values)
If so, which one?

greg_mitch · Joined: 03 May 2006 Posts: 5320

ecrabb · Posted: Sat Mar 19, 2011 5:51 pm Post subject:

ecrabb · Posted: Sat Mar 19, 2011 6:05 pm Post subject:

-Pjackso · Joined: 31 Mar 2006 Posts: 791 Location: Oklahoma

Edit: Post removed. Edit-Edit: Post re-posted.

SC,
You might have an issue with Cone Excursion...

If I entered the info correctly into WinISD:
Inputs:
1) Dayton Audio RSS390HF-4 Driver T/S info:
http://www.daytonaudio.com/lspeakers/reference_rss390hf-4.html
...Or you can download a WinISD file for your driver here:
http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/14410-downloadable-winisd-pro-files.html

2) Box info: 1 Driver per box, sealed configuration (closed, not ported):
Your box internal dimension is 20.33" cube, for a total internal volume of 8402 cubic inches (in^3).
Your bracing is 2x2 lumber, so (actual) is 1.5" x 1.5" x length. The length is (2) runs at 20.33", and then (8) diagonal braces at 8"? I estimated total bracing volume at 235 in^3.
Therefore total actual box volume (after bracing) is 8167 in^3.

3) You're using a 500W amp (each driver).

---------

WinISD shows frequency response: -3dB point is 30hz, and down -6dB by 23hz. (just like you said)
Using 500W, SPL has a high of 114db, 111db @ 30 hz, and drops below 105db @ 20hz.
!!!! You might have a problem with cone excursion.
Using 500W, the cone excursion exceeds Xmax at 36hz (and below) - you may have severe driver clipping (and possible damage).
I didn't use any "EQ or Filter" functions.

...Again, I'm not sure I input everything you did - but you might want to verify your software.

-Pjackso · Joined: 31 Mar 2006 Posts: 791 Location: Oklahoma

Edit: Post removed. Edit-Edit: Post re-posted.

Note: I am not an expert at speaker building

I've been playing with the WinISD model a little more:
If you reduce the actual box volume down to 4000 in^3 (after bracing): the smaller box significantly limits cone excursion.
Even at 500W, the cone excursion stays within factory limits over the entire frequency range (even down to 10 hz).
The smaller box volume does not effect SPL (stays same) and the -3db point moves up to 35 hz.
You may have a +1db gain at 66 hz.

...Again, that's providing my WinISD model is correct. Your model may be more refined, or have other features included.
My only point is to raise the concern.

So far, it's looking good!

ecrabb · Posted: Mon Mar 21, 2011 4:38 am Post subject:

OK, finally getting around to responding to Paul's posts... Spent damn near all day in the garage finishing the damn boxes. I'm hoping to start installing feet, drivers, amp, etc. a couple of evenings this week.

Paul, I'm a total amateur too, sir!!! If you have questions or concerns, feel free to express them!

You're absolutely correct... The box is oversized... So much so that the driver will start to exceed Xmax in the 35hz ballpark if driven at anywhere near full-power. Here's the thing, though... My design goal wasn't output, but flattest frequency response I could get with most the extension I could get without spending a fortune. In fact, I designed the enclosure originally with the 300w amp in mind, but decided to buy the 500w amp because the price difference was relatively small. Read on for more about how I arrived where I did...

My system is clean to about 102dB, but I never listen at that volume. I typically watch more in the 90dB plus or minus ballpark. Now, "film reference" is supposed to be 105dB for the main/surround and 115dB for LFE, right? IMHO, that's way too loud in a small room the way most movies are mixed. So, if I typically listen at around 90dB, and the LFE is supposed to be +10dB, then the sub needs to be able to run about 100dB or so.

Now, back to the sub design... You might have noticed if you just let WinISD pick a box volume for maximum flat response, it comes up with a box in the 5.7 cuft ballpark. Obviously, you're sacrificing power-handling for flattest frequency response with that cabinet. By the same token, your ~2.3 cuft box would indeed prevent the driver from exceeding Xmax and give you more output in the upper frequency range, but as you pointed out, at the cost of about 3dB of extension down in the 20-30hz ballpark... In fact, the -3dB point moved up to 35hz from 30.

Based on my guidance, Darren (that was helping me design the sub) and I chose a compromise between maximum output/power handling (2.5cuft) and maximum extension/flattest FR (5.7cuft) at around 4.8 cuft after bracing, stuffing, amp, etc.

So, with a little bump from the parametric EQ on the O-Audio amp around 20hz, with the 12hz boost/LPF, and judicious use of the gain control, I think I can get flat in-room response down to around 18-20hz at around 101-102dB - something that wouldn't be possible with the smaller enclosure.

I'm getting long-winded... To wrap up, these were the main reasons I went with the larger enclosure...

1) I don't need to use all of the amp... I can calibrate the subs with the rest of the system so they're not hitting Xmax even when I have the system cranked. Headroom is good, even if I'm not using it all.

2) I wanted a larger cabinet to be able to accommodate a larger, higher-performance, higher-displacement driver later if I wanted.

3) The Xmax-limiting output is the main reason I'm building two subs instead of just one. Gives me another 6dB of output.. So, if one sub is good for 101dB at 20hz, then the two should be good for 107dB.

4) I can always use some pieces of filler MDF and/or pine to make the enclosure volume a little smaller... Doing the opposite is significantly more difficult. Wink

So, that's pretty much it, I think. Discuss. Wink

SC

greg_mitch · Joined: 03 May 2006 Posts: 5320

Seems logical to me...do you have in room measuring capabilities once they get finished?

ecrabb · Posted: Mon Mar 21, 2011 5:09 am Post subject:

A few new pics...

Clamping the grille on the front baffle to drill for the grile clips

Front baffle drilled

High-tech depth-stop

Finished hole in the baffle

SC