What about a coffee table sub?

Discussion in 'Home Theater Projects' started by Aaron_Morris, May 9, 2003.

  1. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    I was kicking around ideas of the enclosure shape for the sub I am planning on adding. Has anyone tried, or have opinions on, a coffee table enclosure? It would kill two birds with one stone, so to speak. Not exactly sure how big it would be just yet, but it seems like a neat idea. Anyone think that it would be too directional, being right there in front of the main seating position?
     
  2. Jeremy Wadian

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    Interesting idea that is. Although, I'd worry my drink would rattle to the floor whenever I watched The Haunting. [​IMG]
     
  3. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    heh, I thought about it. More or less just worried about directionality, rather than shaking the carbonation out of my drink. [​IMG]

    Also, I mistakenly posted this in Speakers and Subs... might I ask a mod to move me to DIY. Thanks...
     
  4. Tim_Stonesifer

    Tim_Stonesifer Stunt Coordinator

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    You could check out this link: http://www.geocities.com/manurescape...l?981609316640

    It's just a basic sonosub design but flipped on its side. It seems like you could easily modify it to work like an end table. Keep us posted if this works for you, because I've been thinking about this idea too.
     
  5. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    hmm... that looks doable. What I am really concerned with is making sure that it is tuned low enough that it isn't obviously right in front of mewhen watching movies. I'd like some help designing this thing though. I have access to a good workshop (my roommates father is a carpenter). I guess I should wait until I move into the new apartment before I finalize anything though.

    But as a table, it would seem that I'd have pleanty of space to use, and I could have the sub firing down and mount the plate amp on the side. Guess I will start drawing up possible designs.
     
  6. more so than being able to locate it is room interactions. normally "we" place a sub in a location that lets the room enforce the sound while maintaining a "relatively" smooth responce. When you build this into a coffee table, you have very little placement options. you might have to leave your sub in the worst possible location.

    If you are trying to beat the SAF/WAF, you may also want to consider an end table. atleast this way, you may have 1 or more placement options than with the coffee table

    if your room is not too odd shaped, you can get an idea of how the room will interact with your sub with this freeware program:
    http://www.pvconsultants.com/audio/reflection/rrc.htm

    good luck!
     
  7. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    Thanks Anthony for the software link. Opened it up and not exactly sure ow to use it. But I will keep playing with it and figure it out.

    SAF is not a huge issue at the moment. I am in college and do have a g/f who makes me dress nicer than I'd like to, but she is understanding when it comes to my audio addiction. Since she doesn't live wiht me, she knows that she can't bust me up too bad. Clothing on the other hand, she has to been seen in public with me, so she wins there. [​IMG]

    I was playing with some numbers, and with the dimensions of a coffee table at my parents house, I'd have about 5.4 cuft before displacement of the plate amp and sub. Would this figure be more condusive for a shiva, or would a tempest fit in this size enclosure? I think I'd like to port it and an EBS like responce would be a goal.
     
  8. Dave Milne

    Dave Milne Supporting Actor

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    The coffee-table sub should work... although Tony makes a good point about limiting your placement options. You might want to consider using a symmetrical dual-driver, dual-port design (firing out each end of the table) to cancel the mechanical forces and minimize the "drink spilling" factor. This might also tend to smooth our the room interactions by exciting two locations instead of one.
    One other minor problem, of course it getting the wire to it. The RA probably doesn't want holes/slots cut in the floor. Do I hear "duct tape" [​IMG]
     
  9. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    Well, I don't live in the dorms, so no RA here. I do however live in an apartment. Wires on the floor are not a huge problem for me. If anything, I will get a rug to cover them in high traffic spots.

    Apart from room interactions, does anyone think that it will be directional due to the frequencies involved, or is it possible to limit this effect with a low enough xover, flat responce, and low tuning?
     
  10. RichardHOS

    RichardHOS Second Unit

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    In my apartment I've run wire under the carpet to the surround speakers. Just a clean slit in two places with a razer blade, and some painstaking and clever snaking of flat wire with a stiff piece of copper tubing... The slits are barely noticeable, and after a little superglue, some carpet fuzz sprinkling, and gentle use of a vaccuum cleaner I think it will be well after my deposit has been refunded after I move out before they notice anything odd. [​IMG]

    Better than my last apartment at least... I ripped all the carpet up in the room so I could run wires along walls and across a hallway. Re-stretching was a pain, but the landlord never knew the difference.

    I'm rough on apartments. In addition to the carpet slitting, the first thing I did was drill a big hole through the living room wall for satellite cable. I'll just patch it and paint it before I move out... no harm done. And my old boss was worse still... he cut a "V" channel in the drywall in his apartment to run speaker wire up the walls to surround speakers, and just mudded and painted over the gaping gashes in the walls. When he moved, he simply cut the wire off a bit below the drywall surface and patched and painted the last remaining hole... again, landlord never knew the difference. [​IMG]
     
  11. Rob Formica

    Rob Formica Stunt Coordinator

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    I agree that your biggest problem would be "room interactions" and the lack of placement flexability.

    I don't think it would be very accoustically "directional" with the low x-over point, flat responce and a downward facing driver BUT it might be visually directional. Seeing you will know the table is a sub and will be facing at all times, it'll probably play mind games with you.

    Kinda like those really EXPENSIVE wires... [​IMG]

    later...
    Rob
     
  12. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    Hahaha, Rob, nice jab at the high end wire guys... very subtle.[​IMG]

    As far as room interactions, what do you mean by that? I am a smart guy, so I figure it means just that, things rattling due to the sound waves interacting with things in the room. Am I correct?

    If that is the case, there really isn't a whole lot going in the room. ( TV, stand it is on, rolling rack with equipment, speakers on stands, lazy-boy, large fish tank at other end of room) Other than that, there really isn't much. Remember I am a poor college student, and so wall treatments are a luxry disregarded for things like books and engineering paper. My beloved Snatch movie release poster could be relocated to my room if it shakes.

    I'd think that things like lamps and tables and stuff like that would be most likely to have rattles and what not. Is this logical? I do some caraudio intallation stuff as a side job, so I think I have some viscoelastic material laying around. I could use it to fix some rattles. [​IMG]
     
  13. ColinM

    ColinM Cinematographer

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  14. Rob Formica

    Rob Formica Stunt Coordinator

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    It's exactly as Colin said... Long wave lengths (bass) are very room dependant due to every room's resonant frequencies. It does follow some basic physics formulae, but with the multitude of factors in a standard room (dimensions - furniture - placement), it can get quite complex to calculate. The idea is to place the sub and you so that there aren't any enormous peaks or valleys (as large as 15db) in the critical frequency response.

    That is why you'll hear so many discussions experimenting with "placement"... in this case it's fact rather than fiction... [​IMG]
     
  15. TimForman

    TimForman Supporting Actor

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    Been there, done that. From a decor standpoint it's great. If you're planning on sitting right next to it and actually using it as a table you may be disappointed. You'll get your pant leg blown around and maybe a nice foot massage but you'll miss many of the frequencies. I moved mine to the corner.
     
  16. Aaron_Morris

    Aaron_Morris Stunt Coordinator

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    Why do you say I'll miss many of the frequencies? Cancellation issues or what? I had also considered pointing the sub towards the screen (ie away from the sitting positions) so that the air movement (wind) wouldn't be an issue. I was thinking I could build the box and have the sub mounted on one side and try and see which direction worked better, down or forward, and then attaching the legs and doing finish work.
     
  17. TimForman

    TimForman Supporting Actor

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    In my experience, sitting that close to the sub I felt vibrations and heard it but it sure sounds better 12-14 feet away in the corner. For one, the corner reinforces the bass. Secondly, I think that lower frequency waves can be quite long. A 20 Hz wave is about 56 feet long if I remember correctly which makes a quarter wave 14 feet. My room being the size that it is there is no room gain when the sub is right next to me. Every room is different but I can't imagine a sub sounding it's best a foot or two away from you.
     
  18. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I know the bass waves are long, but you can still hear them even when only a meter away.

    I say consider a piece of furniture that can be placed against a wall. [​IMG]

    Right now I'm finishing up a functional drawer, 194L, 18.4hz Tempest. It was built from scratch out of hardwood and laminate maple and will be installed this Sat so I'll be sure to post some pictures by this weekend. The way we did it, was build a seperate subwoofer box made of 3/4" braced MDF. We then used pocket screws and glue to attach the main panels to the subwoofer. You can see the first phase of the job here. After some insight and autocad renderings, we finally pleased the client's wife. What's funny is she could not settle for something that looked like an end table because it was just too small.

    What's nice is a dresser can be placed along any wall and looks pretty good. The way I've decided to tune the location, is by just basic trial and error in a few spots that the dresser looks best in the room. Another way, (Especially if you have a box room) is to predict the standing waves by cranking some calculations. If you know where the listener is going to be, and where the speaker is, you can then calculate the standing waves for that room.

    I didn't calculate the standing waves, but I did bring a tempest there and ran some tests before designing the sub. My main concern with my evaluation was that her room was riddled with rattles that I'll have to try and fix. [​IMG]
     
  19. TimForman

    TimForman Supporting Actor

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  20. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Too right I intend to do it most certainly.

    BTW, Thanks for pointing out my colorful use of an Alliteration. Not every poster on this forum can recognize the discrete poetry used in my writings. [​IMG] jk
     

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