CurtPalme.com Home Theater Forum

ecrabb · Last edited by ecrabb on Tue Mar 15, 2011 4:58 am; edited 1 time in total

Well, I'm sick of all the political threads... News is a downer, there's Japan... Lots to worry and think about... But, I'm building new subs, so I thought I'd start a thread and share the experience like Greg did with his speakers.

A Little Background
LFE has always been a major weak point in my system. I've been using some nice 12" M&K's (V-75 Mk II's to be exact) for the last few years. These are late-90's/early-2000's-vintage subs. They were about $650 apiece new, but I bought them for less than half that on ebay 4-5 years ago.

The M&k's are very musical and blended with my M&K mains very nicely. But a year or so after I built my theater, I added Crown prosound amps and really took the mains up a notch, and the subs just couldn't keep up. They also just didn't have the extension for HT. 30hz was decent, but by 20hz, they were nearly nonexistent. So, I've been wanting more.

Given how expensive good commercial subs are, and given that I don't have a lot of disposable income, I've been thinking about DIY practically since I built my theater. We're doing a home theater meet in central Iowa next month, so I decided now was a good time to knock this project out. A fellow AVS member who is also local is an avid speaker builder and offered to help with design, so I took him up on it.

Sealed or Reflex? Which Driver?
I've always liked the sound of sealed designs; a nice gradual roll-off, good power-handling, and clean sound. They're also very easy to build, and hard to screw up design-wise. I'm also not too restricted on enclosure size (within reason), so I decided to stay with a sealed design. My goal is LOTS of extension. I want DEEP bass.

I modeled a a whole slew of drivers from many different sources and finally settled on the Dayton Audio RSS390HF-4 15" Reference HF. It was on sale from Parts Express for $159. It doesn't have a huge Xmax (14mm), so no giant power-handling/output numbers like some subs, but for the price, I couldn't find anything that came remotely close to the LF extension.

Design
So, with a little help from Darren, I settled on a box a little smaller than five cu ft. That's huge, right? It works out to a 20.33 in internal volume, not including amp, driver, or bracing. But, I've got a dedicated room, no WAF issues, so after considering all the issues and using 3/4" MDF, the box worked out to about 22.5" on a side.

For an amp, I wanted a plate amp. I don't have anything but line-level wiring to the front of the room, and I didn't want another amp with a fan. To that end, I chose to use the O-Audio 500w BASH amp from O-Audio for $239 shipped. I considered the PE 500w BASH amp for about $50 less, but I did some reading and the PE amp has a 30hz HP filter that requires modification for use in a sealed cabinet. Conversely, the O-Audio amp has a selectable HP filter, but also has a single-band parametric EQ for adding LF boost.

So, according to the modeling, the sub will be down 3dB at around 25hz… Doesn't sound great, but with the driver, enclosure and amp, and a target output of only around 105dB to integrate with my mains with plenty of headroom on all but the most wicked demo sessions ( Twisted Evil

), I should be able to EQ the pair of them flat to about 15hz in-room. THAT is what I'm going for. Oh yeah, I'm building two of these. Headroom, baby!

To recap, I'm going from:
- Two 12" drivers to two 15" drivers
- About 6 cu ft of enclosure to almost 10
- From 150w to 1000w
- From 276 square inches of driver area to 452

How Much?
Here's the best part: Cost. I sold my old subs for $400. That nearly pays for one entire sub, so all-in I'll be spending about $500 I had set aside for HT upgrades to do this. Anybody should be able to build one of these for around $450 or so considering Parts Express runs sales pretty consistently.

To give you an idea what you can do with DIY if you're willing to go to the hassle and effort, this sub should compare reasonably well to an HSU ULS-15... Which will run you a cool $1300 - or $2600 if you get two of them.

With that, here's a few photos. I'll add more as I make progress. Planning to be finished in the next couple of weekends.

Cheers!

SC

ecrabb · Posted: Tue Mar 15, 2011 4:26 am Post subject:

Oh, and before the cult comes out... I have no interest in IB. Maybe in some other house, but I doubt it. I like acoustic isolation and a good insulation envelope around the house (I live in a cold winter/hot-humid summer climate). Anyway...

Here's the rough design in SketchUp...

SC

ecrabb · Posted: Tue Mar 15, 2011 4:33 am Post subject:

Trunk fulla subs...

For scale...

Stack 'o MDF from Home Depot...

My buddy Chad getting ready to feed the first sheet through his cabinet saw...

Gluing the front double-thick baffle...

Jasper Jig circle cutter on the router...

Cutting the baffle...

Baffle cut with the Jasper Jig...

ecrabb · Posted: Tue Mar 15, 2011 4:39 am Post subject:

There's one mostly built...

Awwwwww yeeeeaaaah....

What happens when you use a router with a cutting bit and no dust collection. Yikes!

Gluing up #2...

Routed the grille frame with a 1/2" roundover...

Trailer park dust collection system... Worked!!!

Stack 'o subs!!!

Routed corner detail before any sanding or filling!!!

ecrabb · Posted: Tue Mar 15, 2011 4:42 am Post subject:

That's it for now. I think I've got about 12 hours into them now, not including design time... About 6 hours Saturday, and 6 hours Sunday. I hoping for one more big push this weekend to fill/sand, and finish, then a little here and there next week for final assembly.

SC

greg_mitch · Joined: 03 May 2006 Posts: 5320

Great work! Nice drivers! They look familiar... Wink

Same driver in my Tuba HT Sub.

I am curious as to what the proposed response curve you are shooting for looks like. I was always under the impression that you would need a lot more power for sealed subs to get that low. Of course...500W IS quite a bit...and the box IS pretty damn large.

Hopefully you can have these setup for a little HT get together and the stars align and I can come listen to them.

Wouldn't a sweet cabinet table saw be nice?! I have a 30 Sears table saw without adequate table space but I make due.

I bet those boxes are damn heavy.

This makes me want to finish up my surround speakers in hurry.

ecrabb · Posted: Tue Mar 15, 2011 5:36 am Post subject:

Thanks, Greg! Yeah, you're right... Ideally, I'd have something more like 1000w to dig really deep... But, yes - the box is large, and I'm accepting that the power limitation at the low-end will limit overall system output. That's the main reason for the second sub, actually...

Obviously it's not ideal, and clearly a couple of big prosound amps bridged to 1000 watts and the drivers in slightly smaller enclosures, along with a BFD would have been closer to ideal... But, considering how good my little M&K's sounded, I think I'll be pretty happy with these beasts. Wink

Chad's saw is amazing. Holy crap that thing was accurate... Every piece was EXACTLY square, clean, and smooth. You could almost cut your finger on the edges of those cuts! In fact, the saw cuts were almost as smooth as the router cuts I made. And man that thing was quiet!

Yes, they're heavy... Most of a 4x8 sheet of MDF, so probably 65 or 70 pounds so far.. Empty. Wink

I hope you can make it on the 10th! The subs WILL be done by then - that's the reason I'm working so hard right now.. Well, that and my wife gave me a bunch of crap... You should have heard her after I sold the second sub... "Now that you sold both subs, how the hell are we supposed to watch movies without them?!?!" My wife is awesome. Wink

SC

**kal** · Posted: Wed Mar 16, 2011 1:41 am Post subject:

Wow - nice work Steve! I'm impressed! You know your tools! Smile

Keep it coming!

Kal

rabies_70 · Posted: Wed Mar 16, 2011 1:55 am Post subject:

Dayton subs are really nice. I've used them for several years now with no complaints. Nice enclosures Mr Crabb.

MikeEby · Joined: 24 Jun 2007 Posts: 5237 Location: Osceola, Indiana

Nice work...Tell us more about that saw? I googled the "Biesemeyer" but didn't get much other than a rip fence or something.

Also in the wire frame of your design I see gussets inside the box...Are those still in the plan?

Mike

greg_mitch · Joined: 03 May 2006 Posts: 5320

**Curt Palme** · Posted: Wed Mar 16, 2011 2:27 am Post subject:

NO question that DIY speaker building is a lost art, and you're reviving it nicely! Well done so far!

WanMan · Joined: 19 Mar 2006 Posts: 10270

FYI, in the bad economy that has been with us these past couple of years ... hundreds of finish carpentry and cabinet makers have folded and their equipment has slammed many auction houses. You can get really, really good deals of commercial wood working equipment and not pay thousands of dollars on new.

My problem is I have no room for it, with all the theaters and media rooms in my home.

dturco

ecrabb · Posted: Wed Mar 16, 2011 2:35 pm Post subject:

Thanks, guys!!!

ecrabb · Posted: Wed Mar 16, 2011 2:37 pm Post subject:

ecrabb · Posted: Wed Mar 16, 2011 2:39 pm Post subject:

ecrabb · Posted: Wed Mar 16, 2011 2:46 pm Post subject:

Zebu Fellenz · Joined: 21 Dec 2006 Posts: 2567

jcmccorm · Joined: 15 Jan 2008 Posts: 21

Wow, this is really impressive. I am intriqued by the idea of DIY speakers. I guess being a CRT guy for the last 10 years means that I am a DIY-guy at heart, but I've never really thought of building a speaker.

Can you explain the finishing process when you get there? I love working with wood but have never done anything but paint it, or stain/sand/poly. I have no idea how to get a *real* finish on something like a speaker (or guitar, which I imagine would be similar).

Also, where's a good place to start to learn about the design process? I know that when (not if) I give a DIY speaker a shot, I'd be going with a design that's been proven before, but it would be nice to know the design process to be able to evaluate the strengths and trade-offs associated with different designs. ANy books or online material to start out with? Thanks, and keep those pictures coming!

Cary