Finally done with my sub, and it is awesome!!

Discussion in 'Home Theater Projects' started by Antony, Jul 8, 2003.

  1. Antony

    Antony Agent

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    Hello Everyone,

    Thought I'd share some pix of my sub! I gathered the parts back in November, but had to put the project on hold to get the house ready for sale. Now that it's on the market, I got my wife's approval to work on MY stuff.

    It's a Dayton 12DVC with the PE 250W plate amp and 4" flared port. The enclosure is 0.75" MDF built to Adire's SBB4 alignment, with 0.25" Oak plywood laminated to the exterior sides and 0.75" solid oak top. The trim is solid 0.25" oak that is sold in 4' strips at Home Depot.

    The only way that my wife would allow something like this into our living room is if it matched our growing collection of Mission-style furniture. I was inspired by another person's pictures (sorry, cannot find/remember your name).

    It hits hard, and sounds great. My only question is how do you set the phase control on the amp? I understand about setting the volume control to about half way, then letting my receiver do the controlling, and also setting the crossover to max, then using the receiver for cutting the freqs. So is it just trial and error?

    Thanks for any suggestions. And thanks to Ryan Schnake who gave me advise back in November.

    Take care,
    Antony

    [​IMG] [​IMG]
     
  2. Antony

    Antony Agent

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    OK, looks like I don't know how to post pix. Sorry. Will try again this evening from home. Can anyone tell me how to do it?
     
  3. Charles J P

    Charles J P Cinematographer

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    You cannot reference to pictures on your hard drive. You need to have the pictures on a webserver (a machine connected to the internet that is configured to respond to http requests) which your PC is likely not. There are some free services available that offer this, but I dont know any specifics. Try doing a google search on free image hosting or something.
     
  4. Allen Ross

    Allen Ross Supporting Actor

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    drop me an email with the pics and i can hook you up with as much room as you could need (well under 50mb [​IMG])
     
  5. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Glad you're enjoying it, Antony. Mine's just about the exact same alignment and I love it. Of course mine's just a big sonotube painted black, while yours looks like high quality furniture. But at least it matches the SVS on the other side of my living room [​IMG]

    With a single subwoofer and all speakers set to small you should really just concentrate on the effects of the phase at the crossover frequency. Phase only matters when you have multiple sound sources playing the same frequency. In your case it will be when the sub and the main speakers are trying to play the same note. And this will be most noticeable at the crossover frequency.

    Above the crossover point the sub is rolling off and any cancellation is reduced. Below the crossover point the mains are rolling off so again, any cancellation is reduced and the sub takes over bass duties.

    If you've got an SPL meter then there is a fairly easy (if not quick) way to set the phase just right to get no cancellation at the crossover point. Here's how:

    1)Use a free, downloadable waveform generator (like NCH tone) to generate a pure tone that is exactly the crossover frequency.
    2)Save it as a .wav file and burn it to a CD.
    3)Turn your subwoofer off.
    4)Play the tone at a moderate level and record the SPL at your listening position.
    5)Turn your sub on and disconnect your main speakers from the receiver.
    6)Play the tone again. Adjust the subwoofer level until you get the exact same SPL level at your listening position as you got from your speakers
    7)Hook your main speakers back up
    8)Play the tone through both the mains and the sub. This time adjust the phase until you get maximum SPL output. You should be able to get exactly 6dB more than before when you're in phase since adding two equal sources gains you 6dB.

    Note that the phase knob only gets you 180 degrees of variability. To try the other 180 degrees, reverse the polarity of the connection to the woofer. If you can't get to the speaker leads because the plate amp is mounted to the enclosure then I wouldn't worry about it too much.

    But also consider this - turning the phase knob adds delay in the signal path. Delay is obviously a bad thing or we wouldn't worry about such things as "transient response" and "group delay". 0 degrees adds virtually zero delay whereas 180 adds the most delay. If you find that a setting near 180 degrees gives you the best phase response then consider switching the polarity of the speaker leads since this will give you 180 degrees of phase shift with no additional delay.
     

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