CurtPalme.com Home Theater Forum

ecrabb · Posted: Tue Apr 28, 2009 8:21 am Post subject: Wanna help me design some subs?

OK, I was at Cliffy's house for his "triple stack meet", and while the triplet G90's were a site to behold, his bass really gave me a serious case of upgrade-itis (DAMMIT!!!). I've wanted new subs since last fall, but this really put me over the edge. The rest of my system plays cleanly just about right up to reference level, but the subs run out of steam way before that, and don't have much low-end extension at any volume. They're great music subs, but just not up to HT duty. Since I can't afford a new Seaton, SVS or similar sub, and even the couple of eD subs I was looking at is a lot of coin, I thought I might still be able to get some wicked subs for a lot less money by building.

OK, so 5 or 6 years ago, I bid on some MB Quart 12" drivers on UBid - four of them, in fact - and won them. I don't think I paid even $200 including shipping for all 4 of them. So, under $50/ea.

According to this fall 2001 review, they originally retailed for $329/ea. Cool. They're really well built drivers - Heavy cast baskets, big heavy motors...
http://www.carsound.com/review_archive/subs/MBQuart_RWC_304.html

Looks like later they were $199, and now this place still has them at $99/ea.:
http://www.dealercostcaraudio.com/rwc304.aspx

So, since I have four of these bad boys, it would be cool if I could use them. I'm not sure if they're well-suited for HT duty or not. That's where I could use some help.

Now, I love lots of deep bass, but I like it really clean and not distorted. I'd rather have nice accurate bass, and less of it, than boomy, rumbly, uncompliant bass. I'd say I gravitate toward a sealed design, but I've also been very impressed with a few ported subs I've listed to. I'd love to try IB sometime, but I'm going to nip that discussion in the bud. I'm not interested in compromising my decent isolation.

So, here are the TS parameters for the MB Quart RWC304:
Z: 2x4ohm
Re: 2x3.2ohm
Fs: 27hz
Qms: 5.4
Qes: .41
Qts: .38
Vas: 70L
Mms: 147g
Sd: 531cm^2

Frequency response is spec'ed as 18-300, and power handling is 300w. I can't find an Xmax spec anywhere, but I could probably measure it.

So, would anybody want to help me work through a few designs? I downloaded AJ Vented and Sealed Designer apps, and plugged the numbers in, and... Not sure what to think. I could use some input. I'll attach the screen shots of the graphs. Anyway, if any of you guys that are up on sub building could take a look, give me some input, and maybe bat around a few ideas with me... I'd appreciate it!

SC

ecrabb · Posted: Tue Apr 28, 2009 8:24 am Post subject:

Ported

ecrabb · Posted: Tue Apr 28, 2009 8:25 am Post subject:

Sealed

ecrabb · Posted: Tue Apr 28, 2009 8:32 am Post subject:

The sealed looks pretty good to me... 95L, which is just under 3.5 cuft. Looks like an amp with about a 3dB boost would give me usable output down to the 18-20hz ballpark, yes?

Last time I was designing sub enclosures, it was for my and friends' cars in probably 1990. I'm amazed at how much I can't remember!

Thanks for whatever help anybody would like to provide.

Cheers!!!

SC

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Nice speaker site.

http://www.audioasylum.com/cgi/etv.mpl?forum=speakers

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

ecrabb · Posted: Tue Apr 28, 2009 5:47 pm Post subject:

I think you're right, Gary. -3dB is up around 50hz. I was looking at the power response curve, and it makes it look much better than it really was. It was 3:30am when I was doing that and I shouldn't have been trying to do anything that required any focus or logic. I think I was on auto pilot.

I played around with the numbers a few more minutes in Unibox and I can't seem to get much better low-end response than about -4dB @ 40hz. I do have great output using two drivers and 300w... 117dB up at @ 50hz. Sweet! Here's a question, though: If you look at the response, I'm getting almost 105db @ 22hz, and the -3dB point from there is about 18-19hz... That's not counting room gain, of course... Could/would Audyssey EQ apply a slope to to the 20-80 hz range to give me nearly flat response from 18-80? If so, one of these two-driver subs would be able to keep up with my mains to nearly reference level... Which, is exactly what I'm looking for. This is a 105L (3.7 ft^3) box, with a Qtc of .707 and Fb of 51hz.

If Audyssey can apply a negative slope to cut the upper frequencies, then a second identical sub should give me flat response to below 18hz. Of course, at nearly 4 cuft, each one would be the size of an under-counter dorm fridge... But, what do I care? It's a dedicated theater! It's all about the experience!

Might I be getting close to something usable, here or am I off base?

SC

ecrabb · Posted: Tue Apr 28, 2009 5:52 pm Post subject:

Oh, and I didn't notice this last night, either...
http://www.carsound.com/review_archive/subs/MBQuart_RWC_304_chts.html

Looks like my suspicion was correct... In a ~1cuft box, the driver works perfectly in a car with cabin gain applied - it's damn near flat from 10-60hz. So, the question is, can I make them work in the HT or should I ebay them and buy something different... Maybe build a known a good design with known results.

You should these bad boys... They're damn nice drivers. I hope I can use them. It would be fun to do something custom if I could make it work.

SC

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

MB Quarts are nice...

These are better(imho)
http://mobile.jlaudio.com/products_subs_pages.php?page_id=3

Couple of those in a sealed enclosure....

But wouldnt it be cheaper to buy a nice sub like a sunfire...?

ecrabb · Posted: Tue Apr 28, 2009 7:25 pm Post subject:

John, those JL W's are awesome... I'd love to do something like that... But, the 12W7-3's are almost $500/ea. With an amp and cabinet and materials, I'd probably be pushing $1500. That's not bad, but I'm trying to do something inexpensive so I can do it sooner than later.

I'm really not interested in a Sunfire. In spite of how well-regarded they are, I just hate the idea of the tiny cabinet, then using massive amounts of power and EQ to overcome the disadvantages of the tiny cabinet...

For the same $800 or so for a Sunfire HRS-12, I could get an Elemental Designs A5-350. I could actually get a discount and pick it up from the manufacturer in person... It's huge, but I have a dedicated room, and I get 500w, 15", and -3dB @ 18hz - not counting room gain.

http://www.edesignaudio.com/product_info.php?t=2&products_id=618

My long-term plan is to buy TWO A5-350's, actually. Headroom, baby!!! I can get two for $1500, and a nice discount for picking them up. I'd have plenty of headroom - even when the rest of the system was at reference, and would be flat to well below 18hz in-room. Now, that would be awesome, but it's just not an option right now, money-wise.

So, since I can't spend $1500 or even $800 right now, but could justify $300 worth of plate amp, MDF, and accessories and already have drivers sitting around... I thought it might be a fun project to try building something. I'm not set on the idea, but I have these drivers sitting around... Might as well use them... if I can... Or not. Wink

Just kicking it around right now and trying to design something to see if its even feasible.

SC

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

What about a Sonotube sub???

I've heard a couple that sounded pretty good.

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

Like these:

http://www.passdiy.com/pdf/el-pipe-o.pdf

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

Here's some horns to go with them: http://www.passdiy.com/pdf/KleinHorn.pdf Laughing

ecrabb · Posted: Tue Apr 28, 2009 10:12 pm Post subject:

Thanks for that, Joel! Wink

Those would be perfect if, for instance, I was single (or wanted to be). Wink

Actually, they would work perfectly in my living room with 14-foot ceilings... Wouldn't work worth a damn in my HT where the ceilings aren't even 8 feet, though. Heck, I don't think I could even get them into the basement, let alone the HT - never mind actually standing them up!

I wouldn't mind normal Sonotubes, but they won't work. My room is already tight... The L and R mains are already tight with the walls - the tweeters are probably less than two feet away from the sides already. So, I really need something that can slide into the 30" or so under the screen - right between the center channel and mains. That's about the only floor space I have in the whole room.

Thanks for the entertainment value, though. Smile

SC

greg_mitch · Joined: 03 May 2006 Posts: 5320

Just get an ED sub and be done with it.

I hear that you can get the cabinets unfinished to save some money too...then you just need a can of spray paint. Laughing

I got my AV123 MFW15 for $500 shipped...but that is a long story.

If you really want to build I would talk to the guys at eD and they will sell you some subs and then you could probably mimic the design of the a5-350 or the A7s if you really must have sealed.

For an entirely HT sub use I am always partial to ported but I have yet to hear a good sealed HT sub.

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

SC-

I am just starting to look into subs, I found that sight doing research. If I had the time and money, I would love to mess around with that crazy stuff! But right now, I just need to figure where to begin. I'll be watching this thread to see what you end up doing. I have to put my sub under the stairs so I am limited in space also.

Joel

stgdz · Joined: 07 Dec 2008 Posts: 107

Ecrab have you worked with MDF before? Its a pain in the ass and it gets every where when you cut it, hope you have a good filter system.

If you have I would suggest a sealed Maelstorm-X or a Ported Easy Butt Max power by an EP2500 and either a velodyne SMS 1 or behringers 2496 EQ.

http://www.avsforum.com/avs-vb/showthread.php?t=1051665 sealed
http://www.avsforum.com/avs-vb/showthread.php?t=1093893 ported

Maelx is about 400, Ep2500 is about 300, 2496 is around 200.

ecrabb · Posted: Wed Apr 29, 2009 9:21 pm Post subject:

Thanks for the input, guys... Much appreciated!

Greg, I really like the eD products (and the guys, too!)... I think their stuff is very good stuff for the money. But I just can't get over what, to me, still sounds like "fluffy" and/or "boomy" bass from the eD ported subs like the A5-350. The pair of them in their demo room produced massive amounts of bass... But, it still sounded "boomy" to me - there had to be a big old hump in the response. Now, whether that was a room-mode or a hump in the actual cabinet response, I don't know. Either way, it bugged me. Worse, the lowest octaves of the LFE sounded "loose" or "fluffy". Those two things are the two things I've always hated about bass reflex. Plus, if I'm going to spend $800, I want to LOVE it. Now, I'm not saying I'm ruling out the A5-350 and that still leaves the A7S-450... I haven't ruled eD out or anything - I'm just exploring my options, here. Maybe I can build something for $350 that I'll be as happy with as if I spend $800 with eD, you know?

stgdz... Yes, I've worked with MDF. My equipment rack is built from it. I either work in a wide-open garage outside, or I use a shop vac to collect as much dust as possible. If I decide to proceed, I may eve just have eD or somebody else with a CNC router cut all my pieces for me. I've seen the Maelstrom X and that build thread, before... Looks pretty sweet. That's definitely a consideration... Two would be cool, too! Twisted Evil

Given the cost, I'm not sure if it's enough better than an eD A7S-450 to warrant spending a couple of weekends in the garage when I could just go pick up something completely finished...

I need to do a little more research on the subject, but I believe the Audyssey MultEQ FIR filters in my prepro will negate the need for the external EQ - at least in the current system. That just leaves more money to put into the subs themselves! Wink

Plus, I already have these great 12" MB Quart drivers... Two 12" drivers are almost the piston area of one 18" driver, and should have much better impulse response... And they're "free" because I already have them! Wink

I'm gonna keep reading and figure out which way I want to go. Buy or build. New or used. Wait or not. Yay! A new research project! Just what I needed! NOT!

SC

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

Since you have multiple drivers available, have you considered an Isobarik configuration?
Sometimes it helps, sometimes not. Try it in the software.

**AnalogRocks** · Posted: Thu Apr 30, 2009 12:22 am Post subject:

I use to build speaker boxes back in 1990 or so. We did a whole bunch of push/pull configurations. Including one in my friends Bronco II. It was tight, deep and ported. (insert pun here)

I don't recall it getting too boomy either.