Audio reproduction lesson #3

Discussion in 'OT Technology' started by 04, Nov 27, 2002.

  1. 04

    04 Guest

    Yesterday we covered Car audio subwoofer enclosures. Today we will talk about home audio!

    Home audio is quite a different market than car audio as far as subwoofers are concerned. Almost everyone who buys a subwoofer for their house buys it as an all in one package. Meaning that the actual speaker driver, amplifier and enclosure all come together, and you cant mix and match like in car audio. This makes it rather easy to pick a subwoofer out. Go to the store, and see which one is the loudest, and sounds the best to you!

    There are a few DIY'ers like Loudsystem and myself who build our own subwoofer boxes, pick out the drivers ourselves, and buy an amplifier that works accordingly. This offers a few benifits. First is cost. To get the level of performance from a DIY subwoofer, you almost always have to spend 2 to 10 times as much from a retail unit, depending on several factors. Second is you get to pick the enclosure size, type and asthetics. This is handy because you can match the subwoofer to your decor, you can build a large enclosure for more output, and pick the type of enclosure that is best for your listening tastes and room.

    Since hardly anyone actually builds their own, this tutorial will cover setting up premade subwoofers properly, and knowing what subwoofer is best to buy for you.

    First, evaluate your listening habits. Do you listen to rap with thundering bass, or classical and want to feel the pipe organ fundamentals throughout your body? Or maybe you listen to rock, which might need a little of both?

    One thing to note is that any subwoofer will sound different depending on the room you place it in. It will also sound different in regards to where you place it in the room, and where your listening position is. So keep this in mind when purchasing.

    Knowing your habits, it is now time to go audition the subwoofer. Subwoofers are a bit easier to compare from one another, because they cover such a narrow frequency band. Most people also purchase based on loudness too, and it is pretty easy to tell if one unit is louder than another.

    Also note what size subwoofer you can have. The larger the enclosure, generally the more bass. I for instance have a 8 cubic foot enclosure. It takes up an entire corner of my room. Most people don't have this kind of space available.

    I can only think of one commercially available subwoofer that is a sealed box design, the adire rava. So unless you pick that one, you are most likely going to go with vented.

    So, how do you know what subwoofer size to get? One with a 8" speaker, a 12" speaker, even a 15" one? The answer to this is that it depends on how much output you want. A 15" will have the same sound quality of an 8" if designed correctly. But the 8" would have to be extremely hard core to be able to displace more air, and in turn be louder than a 15". So keep these things in mind.

    So you have bought your new subwoofer and it is time to put it in your room. Where do you put it??? The best place to put it is almost always the corner. And there is a very good reason for this. If you read yesterday's post, I touched on the subject of boundry reinforcement. Well it works in the home too! With every boundry you add, you gain 3dB. For instance, lets say you had the subwoofer in the middle of a footballl field. You would get 3dB of boundry reinforcement from the ground. If you put it against the wall you would gain 6dB. And if you put it in the corner, you now have 9dB!!! so, by putting the woofer in a corner rather than the wall, you gain 3dB! This is a considerable amount. The downside of putting the woofer in the corner is that there can be peaks and valleys in the response of the subwoofer, making it not sound as "accurate". So you will have to experiment on your own to find what place in the room offers the best sound for you.

    Feel free to ask any more questions in this thread!
     
    Last edited by a moderator: Oct 13, 2003
  2. TenSteel

    TenSteel Ted Cruz suicide hotline OT Supporter

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    Yeah, I plan on building my own sub as well in the next month or two along with the speakers I posted about eariler. More than likely, I'm going to go with a 12" that can be used in a sealed application (I think it will offer plenty of bass for my 10' x 10' room). The drivers I'm considering are:

    1. Dayton Titanic 12" MkII
    2. Blueprint 1203
    -- Speaking of the Blueprint, do you have any more info on the 1203 than the site has to offer? Or have you only worked with the 1803?

    I'll probably pair the driver up with a 250w plate amp from Parts Express and build the cabinet with 3/4" MDF. It won't be anything very pretty, probably just painted black. :)
     
  3. 04

    04 Guest

    Well if you are going to use any of the Blueprint 03 series, I would highly reccomend using some type of active equilization, because they have quite a peak at 60hz, due to the motor design.

    In that kind of box, you are going to want to use equilization anyways to boost the output at low freququencies, because the mkII will probably have an f3 of around 40hz, and the 1203 will have a f3 of around 50hz. Basically in that kind of enclosure, equilization is mandatory with the 1203.

    Oh, and if you do go with the 1203, do yourself a favor and get a more powerful amplifier. I have that 250w amplifier on my 1803, and it is not adequate. I would reccomend an amplifier that can do a true 1kW of power into 4ohms for the 03 series of drivers. The mkII series is supposed to be ok with 250w, however. I cannot at any frequency above 15hz get the driver to its linear excursion limits. In a sealed box, you are going to need quite a bit of power to get the driver to its excursion limits.
     
  4. TenSteel

    TenSteel Ted Cruz suicide hotline OT Supporter

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    Well, looks like it'll be the Dayton then. The 1203 seems to have a lot more potential as far as SPLs go, but I don't want a sub that's going to be quite that fussy in a sealed enclosure. Truth be told, I don't wanna spend the money or time with active eq for a sub. :sad2:
     
  5. terminator1010

    terminator1010 Eld

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    I plan on building my own home audio subwoofer. I already purchased a 15" Jl15W0 8-ohm sub. What type of box would you recommend? How powerful of an amp should I buy? Where should I mount the amp? Is inside the box okay? Thanks.
     
  6. 04

    04 Guest

    Well, I put the numbers into my box modeling program and it said a box of around 7 cubic foot sealed would be probably be best. That is enormous, however....

    I do have a question though, why did you pick that speaker anyways, it really wasnt designed for home use....

    But, in a 7cuft box, it should still sound pretty damn good and go pretty damn deep too.

    As for the amplifier, I would get something like this: http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=300-794 Plus it has free shipping, so the total cost would only be 120 dollars.

    With that combo you should have a fairly loud, well performing, albeit huge, subwoofer.
     
  7. terminator1010

    terminator1010 Eld

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    That is a big box....I bought this sub because it was for auction at a local police auction and got it for $80 Canadian = $50 US wich is a good deal. I could sell it on ebay and buy another one though. Which box program are you using? What sub would you recommend and how much is it? I don't have alot to spend.




     
  8. 04

    04 Guest

    I use Winisd. As for the woofer, you can use it, but I wouldnt put it in a box less than 5cuft sealed though. 7cuft would be better imho.

    If you really want to sell it, let me know, we can find some replacement woofers then.
     
  9. terminator1010

    terminator1010 Eld

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    Could I get a better sounding woofer for the price I could sell this one for? I could get around $100 on ebay for it. Its brand new.
     
  10. 04

    04 Guest

    Yeah, you could probably get a woofer that would work in a smaller box for 100 dollars.

    Do you want it to be loud for movies, or more for music?
     
  11. terminator1010

    terminator1010 Eld

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    I already have a 2.937 cu. ft. sealed 15" box. Why did you say a 7 cu ft box would be better? I'm using winISD too and the only difference changing the volume from 2.937 to 7 is it changes the "gain" curve a bit. Will this make a big difference when listening to it? I want it mainly for movies.
     
  12. 04

    04 Guest

    7cuft would be better because it would extend lower in frequency, and also be less "boomy". The difference in sound would depend on your room, how accurate the parameters of the speaker are, and how attune you are to picking out changes. But with that much of a difference, I would expect it to be rather easily audible between the 3cuft and 7cuft boxes.

    Since you already have the 3cuft box, just use it. I mean if it sounds really bad, then come back and tell me about it.

    I bet it will be fine. :)
     
  13. terminator1010

    terminator1010 Eld

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    Thanks for all the help. Now I just need an amp....
     
  14. bob-dc2

    bob-dc2 Expanse

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    when you build your own sub, how do you take into the account of the variances in production from the different cross over compenents and the driver?

    do you tune it to a given reference?

    you forgot about martin logan subs. they are both sealed. some of rel's q series is sealed as well.

    putting the sub in the corner in a bad position does not necessarily make it sound better. it might be louder.
    people should not be looking for just loudness.

    i can easily setup a sub in the middle of the room, and have it sound better than just putting the sub at a random spot in the corner.

    you can change the sound of a sub dramaticaly by changing sub roll of points, direction into room, and location from the walls.

    if you are going to make the effort of an informative post, then make it usefull so that people can learn from and be able to apply what they read in your post to their own system.
     
  15. poisonfist

    poisonfist Guest

    Yeah, most high-end manufacturer's subwoofers are acoustic suspensions. Carvers, Velodines, B&Ws, JM labs, etc., etc., etc... Also, boundary reinforcement really depends on the surface material as well, a glass will have far more reinforcement than a book shelf, it is probably wise to discuss room treatment in this manner too. I had played around with my setup and am in a never ending quest of room optimization, me and my tripod mounted SPL level meter with the sinewave generator and still can't get (my) desired results, blah.
     
  16. 04

    04 Guest

    I don't know why you would ask a question like that. It would be rather foolish to use passive components at that low of a frequency anyways. Not to mention the driver's resonance, which will invariably mess up the filter's target corner frequency anyways.

    As for the driver, you can either measure with a woofer tester, or something similar, you could even use a multimeter to find the theile small parameters. But usually if you are buying a quality driver, you don't have to worry too much about radical swings in the driver's parameters.

    What are you talking about tuning it to a given reference? The tuning is somewhat dependant on the enclosure size.

    As for the Martin Logan, I am sorry I forgot to list that one, like I said, I was only listing the ones I knew about. Also, if you are going to read a guide like this, you probably arent going to drop several thousand dollars on a subwoofer, and in the lower price ranges, vented is the way most of the subwoofers are designed.

    As for not putting it in the corner, well I am sorry, but a subwoofer as large as mine would not fit anywhere else in the corner. And who are you to tell everyone that sound quality is more important than loud boomy bass? I prefer sound quality, but don't tell people who want a big loud sub that they are wrong.... And I did not say that putting it in the corner would make it sound better, I said that it would offer more reinforcement. Also, I have yet to see any OT'ers stereo set up with the subwoofer not in the corner, or near the corner. Yes, moving the subwoofer around the room will change its sound dramatically, but if all you want is output, put it in the corner, it will most likely put out the most bass.

    Im sorry my post didnt meet your exquisite standards. I will try better in the future to do better. :rolleyes:
     
  17. terminator1010

    terminator1010 Eld

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    I bought the 250watt amp from parts express. It will do 180watts at 8-ohms which is the impedance of my 15" JL. I used the ~3 cu. ft box and I think it sounds very good. Plenty loud for my liking. Shakes the whole house!
     
  18. 04

    04 Guest

    :cool: Im glad u like it!
     
  19. fatmoocow

    fatmoocow bored OT Supporter

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    It's hard to go wrong with building your own. I bought a 250 watt plate amp from parts express and a 12 inch woofer from madisound. It's in a fairly large sealed box.

    I had a nice tv stand with doors that I wasn't using, so I built my box to fit inside it. Picked a speaker to match the size of the box. I removed all the shelves and slid in the sub (with a ton of glue). Now I have a bad ass sub that looks like it was built by martha stewart. Doors open up for access to the amp. Since the stand was already mdf The whole thing is like 1 1/2 inches thick or more.
     
  20. 04

    04 Guest

    Do you have any problems with the color messing up on your tv screen?
     

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