Adding a Subwoofer

[TEWhite1]

Hello,

I am going to build a speaker box for a single subwoofer. The subwoofer is 12". The speaker box is going to be 16x16x16. Is this is good size for the box? I was also planning on filling the box with insulation, is this a good idea? Thanks in advanced for your response!

[TEWhite1]

I was also wondering (if ya haven't already noticed, i'm pretty new to this stuff) how much better it will make the sub sound if I put it in a box.

Thanks

[Mudcat]

If you have the subs parameters (Vas, Qms, Fs, Qes, Qts, Xmax, SPL, God, Dam, Syz, Doz, Mat, Ter) you can find a couple of free calculations on the web. They will give you a correct size of the enclouser whether you are using an acoustic suspension or ported design

[Mudcat]

Some of those parameters I made up :rolleyes:

[b727guru]

To piggyback on this question....
Can I install a stand-alone powered subwoofer into a wall cut-out?

Are there any downsides to this that I should consider?

I lack the space on the floor for the sub, but I have room behind a wall to make a cut-out and install a sub from the back of a wall into the family room. :confused:

[annunaki]

TEWhite1, email me your subwoofer driver's parameters. I have an enclosure program on my computer. I can give you a few different enclosure options that your sub would do well in.

b727guru, what you are thinking of doing is fine, IF, you have already done some testing to be sure that the place for the cutout is the optimal placement for the room. Have you done any type of subwoofer place ment testing in the room? If not, I would be sceptical about pinning yourself down to one location.

[TEWhite1]

Annunaki, I do not have the speaker parameters. All i know is that the sub is 12 inches wide; I do not even know who the manufacturer is. The sub was here when we bought the house. If ya want some pictures of the sub, just ask, and i'll post them.

[annunaki]

That may help some. (pictures that is) However, it is difficult to get predictable response from a subwoofer without knowing its parameters. Since a sealed enclosure has the best allowance for errors, I would suggest starting with that. Start with an enclosure of about 2.25-2.5ft^3. Listen with familiar material, as well as testing frequency response levels with a handheld spl meter. Make sure to take notes and record spl levels at reference level (with pink noise). Use 20hz, 30hz, 40hz, 50hz, 60hz ect. up to your crossover point for levl testing at each frequency. If performance is less than desired, simply add blocks of wood, or of a similar material (making sure to secure them insinde the enclosure), equal to about .25ft^3 in .25ft^3 increments repeating your listening and level testing each time. Once you find the "sweet spot" or should I say size, rebuild a nice well braced enclosure at that size.

Note: Make sure to find proper placement of the sub in room before any listening and enclosure tests.

[b727guru]

Well no, I haven't made a test to make sure this is the best place for it.

Unfortunately, this is the only wall I have that I can do a "cutout" to and install the sub. Maybe I can move the sub back and forth along the wall and decide where on this wall to cut the hole.

On the other hand, I thought that sub placement was inmaterial since low frequencies are non-directional. Maybe I'm missing something, this is all new to me.

What should I look for in sub placement?

Thanks in advance,
Guru :confused:

[TEWhite1]

http://www.freepgs.com/tewhite1/speaker/s1.jpg
http://www.freepgs.com/tewhite1/speaker/s2.jpg
http://www.freepgs.com/tewhite1/speaker/s3.jpg

Found no markings except the numbers that you can see on the last picture. If the numbers means something, tell me, and i'll take a closer pic of them.

[Clint DeBoer]

That just might be an FP sub... They make lots of other things. Here's a link (http://www.fisher-price.com/us/default.asp?donotpup=1).



:D

[TEWhite1]

lol :D :D

[Unregistered]

hahahahaha fp...
buddy, that is one discusting sub, you would be better spending 150 bucks on a crappy caraudio sub boxed and an amp. it maybe as boomy as a mother trucker but atleast it will work.

pS. test that thing to see if it even works!

[TEWhite1]

LOL, i did, and i have to say, it works pretty good and definatly responds to the really low stuff, you cant really hear it, I'm guessing because it's not in a box. But if you put your ear close to it when it plays the low stuff, then you can hear it, and it doesn't really sound that bad. But I know what you mean by ugly.

[annunaki]

b727guru,
Subwoofers would only be totally non-directional if one could use a brickwall type crossover. Since all crossovers use some type of slope, we can detect upper order harmonics coming from the subwoofer making it somewhat directional at 80 hz or so. I typically rcommend crossover points around 60 hz or so if the rest of the speaker system allows. Room placement is typically used to try to acheive a flatter room response at the listening position.

TEWhite1,
If you can afford it, I would suggest purchasing a different woofer for your diy project. To acheive serious low end (20 hz range) at or near reference levels, a subwoofer needs either a lot of linear excursion (sealed enclosure), a ported enclosure or a bandpass enclosure. Since we do not have the parameters, a ported and/or bandpass enclosure is not in the cards. That would leave you with doing a sealed enclosure and a sub with little linear excursion. Check out adire audio at http://www.adireaudio.com and look at their Shiva subwoofers. Also, look into the Dayton Titanic II subs at http://patsexpress.com . Either of those drivers would do nicely. They are great diy subs. I would also reccomend a 12 inch driver, space permitting of course.

[TEWhite1]

Annunaki, Thank you so much for your help (especially the links! :D ). At this point, I have the materials for the box, but I think I'm gonna wait to build the box, because I may purchase one of the subs from one of those sites. Any suggestions on an amp, cuz i think i'm gonna need a new one. I am currently running a very old Technics FM/AM Stereo Reciever SA-101. Most likely will have to replace that, as with the sub, it came with the house, so i don't know it's output, but it powers 2 speakers with 8 inch subs/midrange fairly well. The speakers i currently have don't seem to play low notes very clearly, is this due to crappy speakers, or crappy reciever, or both. The 8 inch subs/midrange seem to be made out of some sort of cardboard/paper?!?!? (reason for wanting to have a real sub)

[b727guru]

Annunaki,
Thanks for the response back to my question. Since I'm new to this, I'll ask a very (I think) basic question. How do I adjust a crossover? Is this done at the receiver setup stage?
A lot of terms sometimes become sort of relative to other people's ears. By a "flatter room respose", what do you mean?

Also, since I have only 1 wall to work with where I can place the sub, should I place the sub on the floor along the wall and move it around until I hear this flatter response? Then I cut a hole in the wall?

Guru.

[annunaki]

TEWhite1,
I believe both of those sites also have "plate amplifiers" that can be purchased to drive the subwoofer. They are basically amps that would mount right into the enclosure for the sub on the back side. I would suggest an amplifier capable of producing wattage equal to the sub's continuous power handling at the subwoofer's impedence (ohms).

B727guru,

Flat response would be when all frequencies are reproduced to the same level or within 3 db of each other. This is something that is dificult to "listen" for. A simple radio shack spl meter and a cd with sine waves on it will work quite well in setting up the subwoofer system. Depending upon you receiver, the crossover can be set on it (the receiver) or the sub. If you are using the receiver's crossover, turn the sub's crossover up to the highest frequency. If using the sub's crossover (depending on the receiver) just send the LFE output to the sub with the crossover off. The receiver's crossover typically will yield better results depending upon how expansive it is.

In terms of determining best placement for the sub, here are a few details.
1) Place the subwoofer at the listening position
2) Play fullrange pink noise through the sub only
3) Using the rat shack meter, slowly move down the wall (at the sub's position level, yes you may have to get on your hands and knees) the sub will be placed
4) Note the position with the highest amount of output. Also note other high points
5) After finding this position, test at various frequencies i.e. 20hz, 30hz, 40hz, 50hz, 60hz, up to 80 or so.
6) Note the levels (in db) at each frequency. use the placement that will give you no more that 3db of difference at each frequency. If you cannot get a position that allows this simply get as close as you can.

[Mudcat]

I am currently running a very old Technics FM/AM Stereo Reciever SA-101. Most likely will have to replace that, as with the sub, it came with the house, so i don't know it's output, but it powers 2 speakers with 8 inch subs/midrange fairly well.


I bought one brand new in 1981 for $70 form a place in Manhatten jsut before I gradiated graddut graduato ummm left college with a degree in onglish/mechanical enginerding. Worked great sounded great as long as the room was only 2x2x7 feet. It is 15 or 20 watts/channel (I forget which). Still have the case (used the guts for all sorts of DIY projects that go boom. You will need to replace it. You cannot use it for your intended purpose.

[TEWhite1]

ok, kinda off topic, but if I decide to bridge the left and right channel, will the power output double since I am connecting the left and right channel, or will it be the same. Eg, if I have 20 watts per channel, will I have 40 watts on the mono bridged channel, or will I only have 20 watts on the mono bridged channel? Also, how do you bridge 2 channels together, what do I have to buy? or do I just connect the 2 channels together.

[annunaki]

Chances are, if you bridge the receiver, and it does not specifiy that can be done, you may smell some burn electronics.

[TEWhite1]

Ok, well, I don't think I got the manual for it, and it's really old, so I don't think it would support that very well, lol.

[smith101]

Throw that speaker away! The relationships of a driver and it's enclosure are complex, and you're better off buying a sub in an enclosure where the engineering has been done for you.

First of all, speakers, especially at low frequencies, have to be in a box otherwise the sound pressure they make on a forward excursion rushes around to fill the vacuum created in back, and no sound is radiated. A driver in free air will produce no bass.

Putting them into a box keeps the backwave energy from causing cancellation, but also "stiffens" the movement of the cone since movement in now produces pressure and out produces suction--that limits the long excursions needed for deep bass. A woofer in a small box can go very deep, but only if its cone is small enough that excursion is not limited by the suction/pressure effect. For loud bass, you need a bigger woofer, and a bigger box is a must or the deep bass will be missing. To my ears, the deepest bass is the nicest part.

Some manufacturers use "servo feedback" that monitors the cone position and causes the amplifier to correct movement errors caused by enclosure characteristics. Velodyne (high end) and Yamaha (low end) and others make these. For quality rather than quantity, its the best way to go. It's clear your level of expertise is going to require a freak accident for you to get optimum results with that undefined speaker that you have.

Servo control also ensures that your sub will be well damped--that is, that quick bass sounds (transients) will end quickly like they are supposed to. Poor damping will result in muddy, ringy bass that will destroy the clarity of the sound.

Also, about placement. Rooms resonate at the frequencies of their dimensions. A cubic room is the worst possible case since L W H will all have the same resonance frequency. Hopefully you have an irregular room with angled surfaces. Resonances can be reduced by not placing the sub near intersection surfaces--never in a corner. When you have resonances, you will also have uneven bass--you'll hear it in one place and not the next, because the reflections will be additive at one point and cancelling each other at the next. Much experimentation is required, but stay away from corners and avoid any intersections if you can. :D

[TEWhite1]

wow, wow, wow, wow, wow, and wow again. Alright, well, say I did put that speaker in a box, not knowing anything about it, other than it's 12", would a 16x16x16 inch box make it sound louder no matter what? I will probably need a new amp too, if I follow through with this. This was just suppose to be an inexpensive summer project (spent $20 :D ) that will make this sub sound a bit better/louder. This sub works pretty well, and i'd hate to throw it away, even though it looks pretty ugly.

[annunaki]

TEWhite1,

It would not actually make the subwoofer louder. If the sub were say designed more for ported enclosures (higher qts) it may have very poor performance in sealed enclosures and vice versa. To make a proper enclosure for that sub you NEED the Theile-Small parameters. Guessing only goes so far in building enclosures. Say you needed to build five different enclosures till you found one that worked O.K. The average enclosure, including MDF, screws, glue, and finishing materials, ends up costing about $40-$60, not to mention a few hours of your time. 5 x $50 = $250. For that price you would be much better served to purchase a good subwoofer, build an enclosure and probably buy a plate amplifier.

Smith101,

Servo subwoofers are very nice, great low distortion output with little to no overhang. I have the Velodyne HGS-10, it is an excellent performer. However, subwoofer motor design topology is changing. Great very low distortion output can be had from regular non servo designs as well. Basically rather than make a fix of the problem these companies went to the root of the problem to cure it! Companies are acheiving this through flat or linear BL motor designs. The two best examples of this are the DMA designed motor from JL Audio, and XBL^2 from Adire Audio. http://www.jlaudio.com (look into the W7 and W6v2 subwoofers and check under technologies) http://www.adireaudio.com/Files/XBL2TechPaper.pdf (there is a XBL^2 tutorial on this site and is very informative) JL Audio will be entering the home audio subwoofer market later this year at the Cedia show. Yes, I know, they both do car audio products, but they are on the right track.

[smith101]

Thanks for the links. That's great news that there is new technology. I will check it out, both adire and JL. Hey, I've got nothing against car audio companies, anyone who can make audio better and cheaper is OK. I have heard way too many subs that sacrifice damping for output, and they give me headaches.

[chopan]

I have a SA-101 and i connected a altec lansing (XA-3001) subwoofer with built-in amplifier of about 15 watts and now it´s a powerful stereo attached to my pc.



Annunaki, Thank you so much for your help (especially the links! :D ). At this point, I have the materials for the box, but I think I'm gonna wait to build the box, because I may purchase one of the subs from one of those sites. Any suggestions on an amp, cuz i think i'm gonna need a new one. I am currently running a very old Technics FM/AM Stereo Reciever SA-101. Most likely will have to replace that, as with the sub, it came with the house, so i don't know it's output, but it powers 2 speakers with 8 inch subs/midrange fairly well. The speakers i currently have don't seem to play low notes very clearly, is this due to crappy speakers, or crappy reciever, or both. The 8 inch subs/midrange seem to be made out of some sort of cardboard/paper?!?!? (reason for wanting to have a real sub)