Wiring up speakers

Discussion in 'The Projects Forum' started by MagicMatt, Sep 30, 2013.

  1. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    I have an issue with vibration in a project I've made - quite simply, the speakers I have (2 x 5"x9" oval speakers, rated 50W RMS) are more than happy with the amp power (40W RMS per channel) but they can't handle the low frequencies very well (lots of vibrating from the cones rather than tone). Initially I thought it was construction of the cabinet, but it is actually the speakers themselves.

    I don't have room in the project for two larger cones, so I thought it may be possible to use one larger cone speaker as a kind of sub-woofer, and maybe make a cross-over to take the low frequencies from the existing speakers and combine them into the one large speaker.

    Problem is I don't even know if it's possible, much less where to start!

    I would really appreciate any help on this - if it's possible, I suspect it may be a dead easy passive circuit, but it's an area of electronics I've never even looked at.

    Many thanks for any suggestions,
    Matt,
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Some subwoofers will do it for you. You run the lines into it and it strips out the bass for itself and puts the filtered audio back to the output.
     
  3. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    No, I need to wire the speaker directly, as I will be mounting the cone inside the existing enclosure. The amp only has two speaker outputs (L+R).
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Oops, yes, I was referring to line-level signals.

    You need a crossover circuit. Not my area.
     
  5. mcgyvr

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    Oct 15, 2009
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  6. MrChips

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    Oct 2, 2009
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    Experiment.

    Put two 470μF/63V electrolytic capacitors in series with the oval speakers.
    Connect the capacitors -ve to -ve.
    Connect the woofer in parallel with the output of the amp.

    You will need two woofers, one for each channel.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    For the subwoofer you want a speaker specifically designed for that purpose, such as here.
     
  8. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    I hadn't thought about looking at it from a car audio perspective - it's obvious now you mention those kind of speakers.

    I've found this site, which shows a "6dB/octave High and Low Pass Tri-mode Crossover" configuration...
    http://www.bcae1.com/passxovr.htm
    ...is there any reason I couldn't use that, to end up with two speakers handling from low-mid to high, and one handling low to low-mid?
     
  9. MrChips

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    You cannot wire a single woofer directly to the 2-channel amp outputs.
    You will need some kind of active circuit and amplifier.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    So... do you need more "bass" or would you be happy with just removing the "bass" from the current 2 speakers to eliminate the low freq vibration.

    2 choices.. pick one
    One is less than a $15 dollar solution (capacitors to remove low freq)...
    One is more than a $100+ solution (subwoofer plus amplifier,etc...)
     
  11. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    I don't want more or less bass, I want the same amount of bass I have, but for it to manage higher volumes before the cones start farting.

    I've concluded that the speakers I have, whilst great at lower volumes and rated at 50W RMS, don't really handle much bass when being pushed over around what is probably half power of the amp (20W RMS).

    I want to avoid buying another amp. I'm happy to lose some volume - the amp and speaker combo is louder than I need, and since I can't push it to half way anyway, it's a moot point.

    I realise I'll have to obtain a woofer. I may be able to salvage something suitable from an old HiFi speaker or similar if I kind find something that matches impedance wise (4 ohm). If I can find out how to wire it in, I'll experiment with what I have until it sounds how I want.

    The amp itself says it can drive between 2 ohm and 8 ohm, so I don't see that as a problem, although I'd still like to know how I work out the impedance if I used the 3 speaker config on that page.
     
  12. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    I can't afford to buy twin-coil dedicated subwoofers and start installing them in the enclosure. I do, however, have access to plenty of broken A/V equipment from where I can get bits to expermient with.
     
  13. MagicMatt

    Thread Starter Member

    Sep 30, 2013
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    I'm not saying you're wrong, but I'm struggling to understand why, when that's exactly what is shown on this page:
    http://www.bcae1.com/passxovr.htm
    See "6dB/octave High and Low Pass Tri-mode Crossover"

    Why would that not work?
     
  14. crutschow

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    Why do you say that? :confused: A woofer can be connected directly to an amp with sufficient power using a proper crossover circuit such as one of these.
     
  15. MrChips

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    Oct 2, 2009
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    You can wire one woofer to one channel only, with or without crossover.
    Or you can use two woofers, one for each channel.
    Using the line input signal, you can sum the two signals and feed it into a power amp to drive one or many woofers.
     
  16. crutschow

    Expert

    Mar 14, 2008
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    Of course. I didn't read your post carefully enough. :p
     
  17. mcgyvr

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    then you don't really need subs.. just install "bass blockers" (or make your own) or get a proper crossover and set it above the rated freq response of the speakers.. (80 or 100 hz maybe more depending on the speakers should be good)
    That will filter out the low freq stuff that your current speakers can't handle.. It will still sound just fine if you set it just high enough to stop the distortion.
    All done for a couple bucks or less.
     
  18. tubeguy

    Well-Known Member

    Nov 3, 2012
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    To avoid buying an extra amp you do need two woofers. Or, another option is a single DVC - (Dual voice coil) sub woofer. Some are shown on the link provide by crutschow in post #7.
     
  19. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Another way to support a flabby cone and prevent over-excursion with low freq notes is to enclose the speaker in a smaller box and make it air tight. The compression pressure will support the cone and prevent over excursion 'splat' sounds. It could be that you have a speaker that actually requires this kind of enclosure. Some speakers are designed for ported or open back cabinets. They are much stiffer and hard to move. Other types are not designed to be installed in ported enclosures, they REQUIRE a closed box, for the added support this provides the speaker cone.
     
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