Home theatre cheap subwoofer SQ awesomeness
 

So I have had this subwoofer enclosure for awhile now. It is a 12" dia sonotube cabinet with a 4" port tuned to IIRC around 30 Hz. The enclosure is about 4 ft^3, a decent size. The speaker is a fantastic little MB Quart PWD-254 10" DVC (rated at 300W RMS 750W peak) I bought from Parts Express several years ago. I am powering it with a bridged Peavey CS400 a friend of mine gave me for free.

The sound was good, but a little boomy for my taste. I am more of a sealed enclosure guy in that I like tight clean musical bass, even at the cost of SPL. But for a home theater sub I want both SPL and SQ, since I use the system for movies and music. So I had considered doing something insane like building a huge 15" Shiva sealed enclosure with gobs of power. This would have meant spending more $$ on a new subwoofer, and more amperage (to make up for the non-ported enclosure).

But before I did that, I figured I would give the MB Quart and the Peavey one more try in a different configuration. Inspired by some of the TL projects I had seen on-line, I had been toying with the idea of building a 1/4-wavelength transmission line enclosures using sonotube, so I decided what the hell, time to give it a try. I do not have any pictures to post yet, but really there is not much to it. The enclosure is just a 12" dia sonotube, cut at about 9'6" (about 1/4 wavelength @ 30 Hz), open at one end, with the MB quart mounted on the other end, firing upward, magnet outside the enclosure. It looks a lot like this
http://homepage.mac.com/planet10/TLS...ne_at_home.jpg
More details here...
Steve's Compounded, Super-Duper Shiva/Sonotube(R) T-line Subwoofers
This is about as easy as a transmission line gets.

So I build the whole thing, put some polyfill in the tube (about 4 lbs, all I had) stand it up behind the TV, and give it a listen. The source music is a copy of Dark Side of the Moon on SACD, played on a PS3 connected to a good Yamaha amp via HDMI. DSOTM needs no introduction of course, but if you have not heard it on SACD with a good system, it sounds really, really good.

So the famous heart beat starts up, and begins to rattle the walls and windows, but with no distortion, just a solid, tight, THUMP thump, THUMP thump... So far so good, the SPL was still intact, but the SQ was already sounding better. There was none of the subtle coloration of the thump like the ported enclosure had.

Then Breathe starts...
Holy hell... tight, seamless bass guitar, even sound level and sound quality through all the bass notes. The kick drum is solid and clear. The Great Gig in the Sky, and Us and Them sounded amazing. It is hard to describe this stuff verbally, but basically it is solid, clean, clear strong bass, with enough power to fill my 16'x20' room (with an 11' Cathedral ceiling).

So if you want a cheap, easy DIY subwoofer that sounds great, and you have the room (it is big), and can get past the dreaded SAF (spouse approval factor) then go for it. It does not have to stand up on end from what I hear. I considered going for a lower tuning and laying it on the floor, but this will do nicely for now. I have designed it so I can put a longer tube on it in about 5 minutes.

Just snapped some pictures. Not pretty, but it sounds great.
http://lh6.ggpht.com/_jh2HiMm4nKQ/Sz...0/PC210110.JPG
http://lh4.ggpht.com/_jh2HiMm4nKQ/Sz...2/PC210111.JPG
http://lh6.ggpht.com/_jh2HiMm4nKQ/Sz...2/PC210112.JPG

that is awesome, I need that. Lets get some recommendations on subs.
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That looks ghetto as shit, but if it works who cares. I'm waiting on my budget Polk PSW505 to get in. Should make enough bass for a 15' square room.

If you are thinking about it, DO IT! It is awesome, and really easy to build.

If I bought another sub, I would probably get a Dayton Audio from Parts Express, like this one...
Parts-Express.com:Dayton RSS315HO-4 12" Reference HO Subwoofer 4 Ohm | subwoofer rss315h0-4 12" subwoofer dayton reference rs sub dayton loudspeaker reference-22008
Something like that could shake the crap out of the house with a good, strong amp. It has a Fs of 32 Hz so if you put that on the end of a 10' long tube it should work great. I am assuming it will still have good SQ even though it is a little bigger than the 10"

Here is a legendary Sonotube transmission line project in care you want to go really nuts... This one holds within 3 dB from 17 Hz to 70 Hz. Some good technical info there as well.
http://thecarversite.com/yetanotherf...nstruction.pdf

I'm no audiophile or sub guy, could you explain to me exactly what the sonotube does for the sound? I don't quite understand as it is filled with acoustic foam.

Sonotubes are basically thick wall cardboard pipes that come in a lot of different diameters, from 10" to 36" and up. Their real purpose is to act as a form for pouring concrete columns. Because it is a pipe it has inherent strength and rigidity. Thus one can build a stout subwoofer enclosure without resorting to heavy walls of MDF or the like. Stiff solid walls are very important for speakers, especially subwoofers.

So someone figured out a long time ago that sonotube is a cheap and easy route to building subwoofer cabinets. I bought a 12" dia x 12 foot length for $30 and I can carry it easily. If you build a boxed shaped cabinet from MDF of equivalent volume, it will be MUCH heavier, much more expensive, and a lot more work. Lots of people use sonotube, even high-end speaker builders. Google 'sonotube subwoofer' and you will see what I mean. Sealed enclosures, ported enclosures, band pass enclosures, and transmission lines are all built with it.

Just the reduced weight is nice. Most of the mass on a sonotube sub comes from the speaker itself. with an MDF enclosure it is the other way around. I'll bet mine above weighs around 30 lbs. Build that out of MDF and I am guessing it would weigh well over 100 lbs.

The sonotube I used is not the kind filled with foam. It is just a tube. I did fill it with polyfill (pillow stuffing) but that is ubiquitous practice for any speaker. Polyfill does good things like adding damping (to reduce ringing) plus it makes the enclosure act like it is 'bigger', up to 30% IIRC if it is used correctly.

So the sonotube is really great for a transmission line. Just cut it to the right length, stick a speaker on the end, tune with polyfill, done. One still has to get the right speaker and cut it to the right length of course because they need to be tuned like any other enclosure. Things get more complicated if it is a converging or diverging port transmission line.

I guess I understand that. So a larger enclosure = cleaner and deeper sounds?

I was just looking around for a good cheap project, and happen to have four cabinets worth of speakers I don't mind tearing up.

Not necessarily, but sometimes. It depends on the speaker type. With sealed enclosures usually the bigger the better, at least until it gets ridiculously big. Really though it all comes down to tuning. Whenever I am designing a speaker cabinet I use WinISD (great freeware speaker design software) and try out several kinds of speakers in different types of cabinets.

WinISD does not work for transmission lines, or it is not intended to anyway.

I just spend a couple of hours running a bunch of different kinds of music through it, including Fagen's "The Nightfly" and I am still pleased. It could maybe use a couple of more pounds of polyfill to smooth out some tiny peaks at the very low end, but then again it could just be standing waves in the room. Otherwise I am still really pleased. My wife hates it :giggle:

"But honey, LISTEN TO IT! IT SOUNDS AMAZING"

BTW I know everyone has probably heard Dark Side of the Moon a million times in various states of mind. But if you have not heard it on SACD, and you have a system that will play one, like a PS3, get a copy of the SACD! It is like rediscovering DSOTM all over again. Just hearing how amazingly beautiful "Us and Them" is totally worth the purchase. It is basically a remastered recording, using 5.1 sound, with stunning audio quality.

I have, or had the SACD version of DSOTM, but it got scratched to hell. I also don't have a PS3 anymore and I don't think my Blu-Ray supports SACD. I wonder if you can get SACD quality files onto a computer? Not sure if that would be supported. I could just listen to it through the receiver that way.

OP, that is the worst design for a subwoofer enclosure I have ever seen. You obviously have no clue what you are doing.

>^..^<

Ahhhhh hAHAHAHA! Catman symbol. I get it now. Funny! Catman, what a douche :)
His doucheness is so big, it would not fit in a 24" dia sonotube of any length.
He is such a big douche, that he frequently volunteers at the local zoo to help give female elephants that fresh feeling. I hear he can treat several in the same day.
He once drained an entire fresh water lake while refilling himself. Shipping in the Great Lakes region has not been the same since.

Maybe if I bought a Nak source unit and a McIntosh amp, I would be Catman worthy.

Maybe, but no guarantees lol. Much respect goes to you for actually being able to do this. I have wanted to for quite some time, but never ever would get approval. What you can do is paint it black and allow pictures and decorations to be hung on the tube.

While you are at it, you may want to look into building some bass traps to control your room reverberations for proper tuning (if you get SAF qualified):

Canuck Audio Mart &bull; View topic - DIY: 2d QRD (Skyline) Diffusor Build

Actually, while you're at it, it couldn't hurt to mock up some skyline diffusers as well.

Looks sweet, i might do this style sub for my 20x20 room hehe

If you have extra left over paint from when ever you painted your living room you should paint the sonotube, That is if the looks bother you.

The diffusor effect can also be achieved by bookshelves, plants etc.

I do strongly recommend bass traps. People (other than you :P) spend a lot of money on speakers and components but don't put effort into tuning the room. Bass traps can make a shitty square room sound pretty decent. You have a nice big room though and a cathedral ceiling is superior for acoustics.

One thing about the design-- wouldn't a long port design like that hit 30hz and the harmonics really well but not necessarily the other notes? I'd bet that frequency response would be all over the place.

I have a powered 12" subwoofer, I simply put it where I sit on my couch and crawled around the floor until it sounded best and placed it there....I guess I'm doing it wrong.

Nope. Did I tell you to do that?

Tex, check these guys out. Auralex Acoustics - World-Class acoustic foam sound control products at real-world prices!
You want a subdude under there. Trust me. :)

no, i read it somewhere online when i first setup my shitty home theater setup years back.

Yep I am going to work on the room next. I need some bass traps and the like, as well as some soundproofing. My wife keeps complaining it is too loud :D I plan on hanging some curtains beside and behind the front stage (TV, front speakers, sub) so the TL will end up being hidden from view. The room is a little too live right now so I want to try adding some damping with the curtains. I may build some bass traps too.

Feaflora the response sounds to be really flat. That is a big deal for me since I hate peaky subwoofers. BTDT. I have a buddy that has a nice analyzer I need to borrow to check it out some more but it sounds flat to me. Last night I listened to some jazz recordings with stand up bass playing walking bass lines and did not hear any peakiness. All the notes were the same volume.

my house is too small for that behemoth.

I've got a 15" sub in a tiny box with a linkwitz transform circuit so it plays down into the low 20 Hz anechoic. it's the bomb. and plenty loud for my dinky house. sounds astounding when movies have planes taking off. feels like you're on the plane.

it's so pimp, even the cats hang.

https://www.miataturbo.net/forum/att...1&d=1261495179

I've heard it, it's alright I guess. :)

I have heard of that trick before. Unfortunately my placement options are somewhat limited :)

OK I see what that is, thanks.

So speaking of floor mount treatments, what is the deal with spikes? I see them on subs, and hear how they are a must, but need to read up on them some more.

Very cool. I have seen linkwitz circuits talked about in the better DIY audio forums but have yet to try them out. That lets you use a small box but still have a low-Q response right?
I have not done much crossover tuning. This one is running off of the LPF on the receiver. Right now it is set for 120 Hz but I do not know what the slope is.

If we're whipping them out, I have one of these in 15" in the theater
Velodyne
It's pretty amazing.

And this guy in the living room
RSW-12 Subwoofer - Specifications

And some cheap Jamo subs in the office and the master.

Yah not only do room treatments matter but speaker placement is also critical. It may nto be necessary to cover the whole front in draping-- putting absorption where early reflections are and standing waves can help clean a room up without making it dead. Personally, I prefer to use broadband absorbers that are heavy on the bass absorption.

I recommend zero auralex products. They are overpriced and a foamed up room will sound like shit. Google owens corning 703 or 705 bass traps. You can DIY them or buy them or buy mine :) 703/705 on it's own has superior broadband absorption characteristics to foam. If you want to decouple your speakers, you can also just use styrofoam boards, or my favorites- mousepads. Decoupling does work some of the time but some of the time it can make things sound worse-- you will have to listen.

I've never heard of these linkwitz circuits before but I don't know speakers very well. If anyone local wants to buy some discount bass traps I have a lot of them that I'm not using now. :)

Tex,
Small footprint enclosures have spikes to add stability. That's obviously not what we're talking about here.
Large footprint enclosures use spikes to decouple them from the floor. The surface the speaker enclosure is contacting of becomes part of the enclosure. When you decouple the speaker from the surface, you will reduce the transmissions between the speaker and the surface. Some people will place brass spikes under the speaker enclosure, then rubber or solid discs under the spikes. A friend of mine in pro-audio turned me onto the Aurulex line, and now I use their products all the time. Previously, my least expensive consumer line I was using was Kinetics Noise Control.

fae-I think you need to take a closer look at the auralex line. They sell more than plain foam absorbers and diffusers. DIY wrapped owens corning boards might cost less, but not everyone wants to go that route. Not to mention, styrofoam blocks under your speaker cabs just looks ghetto as shit. MoPads list under $30 and won't offend the ladies.

http://www.auralex.com/sound_absorpt...nosuede/S3.jpghttp://www.bhphotovideo.com/images/i...345/619652.jpghttp://images.digitalmedianet.com/20...ry/mpad250.jpg

the L-T allows you to "pick" your Q and F3 and give any sub those values in any box. It's pretty awesome. I just built the circuit into the back of a plate amp. only drawback is that excursion requirements go up fast for small boxes, so you can't always play really low really loud. but I'd rather have 2 or 3 mini subs that go to 20 Hz than one that wont fit in my living room.

btw, total cost to build mine was like $400 all told. about half and half sub and amp and the rest in wood and spikes.

Their pro panels do have good specs and their partscience products also look good. Their construction products also look good and their u-boats might be easier to install than rubber disc isolators. There are just other products out there that are as good or better for cheaper. IMO they still do most of their business unethicallly- selling very profitable foam as a panacea.

You are right that DIY bass traps are not for everyone. I've made them before and unless you're a good craftsman (not me- see my frame rail for proof) they may not turn out that well.

I recommend

DIY Bass Traps: Complete Do-It-Yourself Kits : Ready Acoustics!, Hear - Sound - Better

and

RealTraps - Home

Real traps are higher quality but they're more $$.

Y8s did you study room acoustics in school or mostly speaker design?

Mousepads FTW :p The mopad speaker angling thing is pretty slick though. In general, you don't want your head to be off axis from your speakers.

I could't bring myself to buy Auralex stuff. They want ridiculous prices for some of their stuff. Especially the MoPad's, anyone could find material at a store like Home Depot for probably 1/10 of the cost and have the same thing. Buy some dense foam, shape it into a wedge, cover it with cloth for a fancier finish if you like... speaker isolation for a few bucks.

I took one grad level acoustics class. after that it was all self-taught. I did get to meet Siegfried Linkwitz though.

http://home.pacbell.net/donwm/Entry-2022.jpg

I like the chameleon panel approach. I built some simple versions of those, albeit with poly fiberfill, and hung them on the walls in my very noisy living room. The reverberation was so bad that someone that was 20 feet away in the kitchen (open floor plan) had unintelligible speech. The panels made a big difference and they look nice.

Some floor standing room divider walls with some of that corning stuff in the center, trimmed with nice wood, and covered with nice fabric would be easy to build and would look nice. I could hang a long, narrow one from the ceiling in front of the sub and kill two birds with one stone so to speak.

Holy hell I keep forgetting how expensive audiophile stuff is. I am in the wrong business.

So what kind of stuff can one get in the insulation section at Lowe's or HD that is 'close enough' to the Corning semirigid panels? Seems like non-backed fiberglass battens for between wall studs would work well too.

Not sure specifically, but I know out of all of that junk they have to have something that would be similar or even better. I would love to build some of those traps with the wood frame, Corning stuff and the fabric, but I don't have any walls large enough. Too many damn doors and windows! One of those at about 4'x6'x6'' on each adjacent wall would probably kick ass, and well as one on the back wall opposite of the TV and front speakers.

I have built systems around the OC 705. Basically, built a box out of trim with a fabric track system on the inside edges of the trim. Cut the fiber panel to fit the inside of the box, and stretch fabric across. Pretty easy. I need to find pics.

I have never tried to apply fabric directly to the OC panels; I've always bought them pre-done from Kinetics, and recently Auralex.

<edit>This is not my work, just a pic I found showing a fabric track system. You don't have to do the whole wall.
http://www.zeronoise.com/sound_contr...AX-THEATER.jpg

from outside to inside layers:

you need a small texture, porous surface to address high frequency reflections and absorption.

you need a soft layer to absorb energy below that.

you need a dense, thin layer to move with the transmitted sound and vibrate it away into heat. ideally something with no "springiness" like lead or tar paper or something.

you need another soft foam layer behind that to allow the movement of the dense layer

you need a firm structure behind it all.

...

you could probably make it out of

grill cloth on top of soft open cell urethane foam (at least two inch thick) followed by some roofing paper/underlayment or even the mcmaster carr sound deadener sheet followed by another inch of open cell urethane foam and attached to some kind of backer.

I suspect you'll need some nails or something to keep it from all sliding down the side of the wood though.

Yes there you go that is what I am thinking. It should be good for a first try anyway. That fabric track system, is that the same sort of thing that is used for screen doors? That is, there is a little piece of tubing that gets pressed in to a channel with a roller that stretches and holds the fabric? That would make finishing really easy.

I am just not sure where I can get the OC 705 locally. I know that is what is considered to be the way to go but it seems like there should be something at the hardware store that would be good enough.

EDIT: Here is someone talking about using 'duct board' instead of 703
http://www.gearslutz.com/board/so-mu...uct-board.html
For non-structural wall treatments and/or bass traps that would be REALLY easy. Just cut to size, stretch some nice looking fabric over the duct board, staple onto the back, hang on the wall, done.

I've never really studied a screen door, but I'd imagine it's similar. Sounds the same.

Here's something from google
http://www.wallmate.net/images/wall1.gif

I've never tried to stretch fabric over the board itself. It's kind of hard to cut to put a super nice edge on it, so I've always purchased that type of stuff pre made. If you found some board that was already cut to the size and shape you wanted, then Matt's idea of using speaker cloth would be great.
When you build the fabric track system, it doesn't matter that the board is cut sloppily because it's all completely hidden.

Well I hung some curtains in the room on the windows on the side walls (dormers) and about 3' in front of the wall that is behind the TV. There was definitely some room coupling (standing wave?) going on before because the sub is even flatter now. I am still really pleased with the setup.

Definitive Technology Promonitor 1000 speakers sound really sweet, especially for the price. I picked up a pair used, but in new condition, and they sound fantastic.

Your curtains won't kill any bass standing waves unless they are made out of plutonium. They aren't dense enough.

They won't kill but they will help.

Sure they will help.

They'll help a teensy bit.

At best they'll clean up some lower mids.

That's better than nothing. I would imagine that is why most every movie theater I have seen has the bunched up curtain walls.

Wrong. I'm being a dick but read up about this stuff. Movie theaters have bunched up curtains for a number of reasons, and probably the primary one is for a traditional look. Movie theaters are evolved play theaters right? They also have curtains and in-wall batting to suck up highs to make the room dead.

Heavy fabric will suck up a lot of highs, some upper mids, a little mids, and almost no low mids or bass.

Adding curtains could make bass playback sound clearer because you can hear upper harmonics, picking/slapping noise etc more clearly, less "wash" from highs overpowering your perception etc but adding curtains won't make a sub appreciably flatter.

the effectiveness of an absorber is often related to the wavelengths of the frequencies it is absorbing.

high frequency waves are short.

low frequency are very long.

that's why you hear thump thump from cars and other theatres, but rarely the highs.

I've got a Shiva (RIP Adire) sonotube in my basement. Has worked well for the last 8 years or so.

I have a bunch of 8-12 sonotubes in my shed taking up space if anyone local is looking for some for a sub project.

Also have an NHT 1259 clone (same motor and voice coil but higher Re) in a 10 inch that I was going to use for a project if anyone wants to build a good cheap sonotube for a small HT setup.

I don't want to ship this shit, so you gotta pick 'em up.

Frank

Well I meant sound in general, not just low frequency.

I got the new Star Trek in Blu-Ray for Christmas and played that yesterday. The LFEs are fantastic. When the ships go into warp they make this fast broad spectrum transient thump-pop sound. The sub hits those hard and fast. The movie is full of good LFEs in general.

I just bought a set of Def Tech BP6B used (in pristine condition) from a local audiophile guy I found online. He had upgraded to some used Martin Logan Quest electrostatic drives and thus was unloading his 'old' speakers. He Played the MLs for me and of course they sound fantastic. The sound stage is pretty spread out (not much location info) but the mid-range sound quality on vocals and piano is really, really good. They are also really, really expensive, much too expensive for my blood.
MartinLogan | Quest

Normally I build speakers myself but used Def Techs in good condition are such a good value it is hard to build anything as good for less money.

I've watched Star Trek probably 4 times since I got my speakers 2 or 3 weeks ago. I don't even have a sub yet, but just with the weak bass provided by my front channels, the sound is still amazing. Some of the best sounds in any movie I have seen.

Yes it is really good sound. Wait till you get the sub connected :bigtu:

I watched public enemies in blu ray the other day, and I gotta say the gun sounds were fantastic, like better than most movies lol.