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Thread: Horrible idea? Round to square adapter for woofer...

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    Constant Bitrate Lincolnman's Avatar
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    Horrible idea? Round to square adapter for woofer...

    THIS IS NOT A BOX - ONLY AN ADAPTER!
    Okay, so here's my (theoretical) situation - I want to put woofers into my package tray.

    I have a finite amount of space in which to place them and they are too large for the given space. Add to this the irregular (not round) mounting shape. (It's not fair to really call it square or rectangular, but that's the idea.) Also, before anyone suggests it, rule out any strange speakers like this one.

    The woofers are already chosen, purchased, whatever. The package tray allows for 8" on one side from seat top back to window base, and 10" on the other. Width is obviously not an issue, nor is space for the basket, magnet, etcetera. The problem is cone side. Now we'll figure that the woofers in question for this space are 12". Since there is so much extra space in the trunk that is unused, the thought that occurs is to simply move it further into the trunk. This could be done with an adapter from fiberglass that goes from the round woofer pattern to the rear package pattern, like an HVAC duct.

    The obvious distinction here being that the "rectangular" side would be of less area than the sub's face, or even equal but the shape changed. Think of a trumpet's end with the woofer mounted facing into it. It would be something like this

    but with the woofer facing what would otherwise be in.
    Okay, so now that you understand the concept, how would this affect the sound? I would think that the coloration from reflecting off of the surfaces would be less problematic for lower tones than for a mid range or higher driver. So, assuming that there are no issues with port velocity from too small an opening what would happen?
    Electronics work on magic smoke - don't let it out.

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    MySQL Error soundman98's Avatar
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    reflections are always the biggest problem in car audio--no matter what freq.

    with the immediate sound wave reflecting off the back window, there is always a chance that it could result in a easier-locatable sub(if you're going for sq, it's a bad idea)..

    the other thing to keep in mind is the distortion of the sub. if you put a sub in front of you, and crank it up until it audibly distorts, or sounds bad, and then do the same thing, but turn the sub so it is reflecting off a wall, so you are hearing the reflectiong sound wave, it will sound cleaner, because the reflection will cove up some of the nasty stuff.

    while the 2 paragraphs seem to contradict each other a little, they are both true..


    because the glass is so smooth, pointing the sub at a 45deg angle to it, means that EVERY sound that the sub makes gets reflected directly towards you.. when you point the sub mostly at a carpeted surface, some of those nasty effects get absorbed, so when the sound gets to you those nasty artifacts are removed-- too a extent..


    this is why so many setups have the subs pointed at the back of the trunk instead of the front..



    anyways, i don't believe the baffle should be a huge deal-- as long as you use large, rounded edges, the baffle it-self, should not affect sound quality..

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    In Australia, we have a car called the Ford Falcon, been a stalwart of the Aussie car industry for many a decade.

    But, the premium car audio systems that Ford offered with those, fit 2 6.5" round speakers on the outside of the parcel shelf, and an 8" sub in the middle, just mounted straight to the parcel shelf.

    From the few that I listened to, the sound quality on it was great. No ear splitting bass, but a high enough level to make the sound of it nice and smooth across the frequency range.

    I'm not sure how well it would work using larger 12" subs, as I think the 8" are more to provide mid-bass, rather than the thumping low end bass (Correct me if I'm wrong?).

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    Constant Bitrate Lincolnman's Avatar
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    Quote Originally Posted by soundman98 View Post
    reflections are always the biggest problem in car audio--no matter what freq.
    I understand that reflections are always a huge problem in vehicles, which is why although I would never try this at home I thought it might be less of a problem in a car. Thank you for answering the frequency question, though.

    Quote Originally Posted by soundman98 View Post
    with the immediate sound wave reflecting off the back window, there is always a chance that it could result in a easier-locatable sub(if you're going for sq, it's a bad idea)..
    Any suggestions for SQ on where to put it otherwise?

    Quote Originally Posted by soundman98 View Post
    anyways, i don't believe the baffle should be a huge deal-- as long as you use large, rounded edges, the baffle it-self, should not affect sound quality..
    You understood that it will be a changed (and smaller in some dimensions) shape for the baffle opening, yes? So since it will be forced to reflect at least a portion of the sound off the walls of the baffle there are multiple reflections happening.
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    Constant Bitrate Lincolnman's Avatar
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    Quote Originally Posted by Chester View Post
    But, the premium car audio systems that Ford offered with those, fit 2 6.5" round speakers on the outside of the parcel shelf, and an 8" sub in the middle, just mounted straight to the parcel shelf.
    Same idea, except my inspiration was a classic Mustang rather than an Aussie Falcon (and not factory, it was a JL).
    Electronics work on magic smoke - don't let it out.

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    Constant Bitrate Lincolnman's Avatar
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    Oh, to clarify, I had initially meant TWO woofers on either side, not one in the center.
    Electronics work on magic smoke - don't let it out.

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    Quote Originally Posted by Lincolnman View Post
    ...You understood that it will be a changed (and smaller in some dimensions) shape for the baffle opening, yes? So since it will be forced to reflect at least a portion of the sound off the walls of the baffle there are multiple reflections happening.
    yup.. i think it should be ok-- as long as the edges are properly rounded..

    the main problem area with baffles, or ports is the edges-- or the airflow.

    back to basics: you might know it, but i'll say it anyways..

    a speaker makes good music by moving air molecules-- it does this by coupling-- meaning that when the sub moves, it moves all of the air molecules..

    same thing for sub ports-- when the air in the port couples well with the air outside the port, there is no noise, and it works normaly.

    in either case, when the speaker, or port-air moves faster then the outside air-- referred to as decoupling, you start to hear nasty noise-- because the air around the speaker/ port cannot keep up..


    a smaller opening baffle should use many of the same concepts as a bandpass enclosure..

    the idea behind making sure that the openings of the baffles are rounded good is so that the air can correctly couple with the subs, to prevent noise..



    i should also point out that while i am familiar with the concepts, i am not very good with making it a reality, so you might need to ask a similar question on a audio forum to get specific answers to what kind of round-over would be acceptable, or minimum opening sizes to prevent other problems..

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    Constant Bitrate Lincolnman's Avatar
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    Quote Originally Posted by soundman98 View Post
    i should also point out that while i am familiar with the concepts, i am not very good with making it a reality, so you might need to ask a similar question on a audio forum to get specific answers to what kind of round-over would be acceptable, or minimum opening sizes to prevent other problems..
    It would seem logical that if a person matched the Sd of the driver to the square inches of the opening, everything should come out. I'm no sound engineer, though. On the subject of the radius of the curves, I would think that if a person just followed the general rules of head porting shape for the adapter it would work out. Again though, not an engineer.
    Thoughts?
    Electronics work on magic smoke - don't let it out.

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    makes sense to me..

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