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Powering subwoofer - need some clarification.

Discussion in 'General Hardware' started by selway89, Aug 17, 2009.

  1. selway89

    selway89

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    Hi all, just posting to pick some of your brains :)

    I currently have a fairly nice sound system for my pc:
    Creative X-Fi XtremeMusic into a Mission Cyrus One amp, driving some Mission M30i speakers.

    However I want to add a bit more low end uumff. My old amp (Teac CR-H100) did power a Bose accoustimass subwoofer of my dads but thats back in its box ready for eBay :(

    My query is will my Teac amp which is 20W per channel and can drive 6 to 16ohm speakers be ok to power a mono 3ohm sub? Thinking of this cheap sub: http://cgi.ebay.co.uk/ws/eBayISAPI....71859&ssPageName=STRK:MEWAX:IT#ht_1392wt_1165 or this one http://cgi.ebay.co.uk/ws/eBayISAPI....gory=14996&ssPageName=WDVW&rd=1#ht_1281wt_907

    Obviously I'd like to make sure that audio from both Left and Right channels go to the sub so I were thinking if I wire the Left and Right outputs into the single input be ok?

    [​IMG]

    The Teac amp will be fed from the headphone out on the Cyrus and this works fine and allows me the option to control the sub volume or to turn it off completely, worked great with the Bose.

    Any info and help will be greatly appreciated. :)
  2. Frederik S Staff

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    It might work, but it will most likely either sound like crap since the amp is made for a normal load or blow a fuse in the TEAC since it isn't made for extremely low impedance loads like a real sub.

    And the BOSE Acoustimass wasn't I believe a real sub but just a bass driver put in a sub like cabinet. Normal impedance made for systems with no pre sub or sub out.
  3. selway89

    selway89

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  4. pantherx12

    pantherx12 New Member

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    I'd say go for a better amp and sub anyways.

    100 watts of bass is so much sweeter to the ears :p
  5. dr emulator (madmax)

    dr emulator (madmax)

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    yikes no it doesn't work like that i'll see if i can find a small but easy to do/understand diagram for you (may take some time to root one out) [​IMG]
    :edit:
    oh and i'd have to agree with pantherx12 it'd be better if you did get something proper
    selway89 says thanks.
  6. selway89

    selway89

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  7. Wile E

    Wile E Power User

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    Wiring a 3ohm sub into both channels in parallel like that will result in a 1.5ohm load. Much too low for that amp. You would need a single sub of 12ohm to wire it like that, or 2 3ohm subs wired in series per channel would also give you 6ohms per channel.
  8. MKmods Case Mod Guru

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    I dont have any time now to explain properly but here is a simple guide
    http://www.diyaudioandvideo.com/FAQ/Wiring/

    If you try to run a home amp thats made for 6-16ohm less (like 3ohm) it will overdrive the amp and overheat possibly fry it...
    dr emulator (madmax) and selway89 say thanks.
  9. Wile E

    Wile E Power User

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    Overall, I'd say you're better off with a powered sub that has speaker level inputs.
    selway89 says thanks.
  10. selway89

    selway89

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    Cheers all, thinking about it, it now seems like a daft idea. My brain isn't functioning too well tonight :p

    Think something like those eltax ones might be more than enough for my needs. That eltax one I'v linked is the kinda price I want to pay. Using the headphone out will be ok for the sub line in shouldn't it?
  11. Wile E

    Wile E Power User

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    Only if the sub has it's own crossover built in.
  12. selway89

    selway89

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  13. Steevo

    Steevo

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    I built some great boxes based on Bose technology, just get a good transformer out of a old stereo and a couple caps and use a car amp. Wire it up and you have a kicking sub for less than $50
    10 Million points folded for TPU
  14. selway89

    selway89

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    Like the idea! Unfortunately my dad won't let me use the bose sub. Think I'll go with that eltax or something similar. Give it line out from headphone on Cyrus amp and set the crossover and volume. Hopefully give me a bit more bottom end than the tiny M30i's which is surprising for their size. Always nice to have a bit more to annoy the flat mates with when I go back to uni in sept :p
  15. pantherx12

    pantherx12 New Member

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    You could buy a speaker : ]

    You can get a 150 watt speaker for about 30 quid if you look in the right places

    ( places that I can't remember at the moment but I'll look for you in the morning)

    And you can get 180 watt amps for 15 quid of ebay ( the blue ones, they work really well actually)

    All they need is a 12v power supply ( and above 1 amp, 2-5 amps ideally, but they will run of 12 1 amp, they just won't go as loud)


    Then its just a case of finding some MDF, cutting holes sticking together etc, its not to much harder then building a pc to be honest, if you have the right tools.
  16. dr emulator (madmax)

    dr emulator (madmax)

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    if you are still planning doing it yourself here's a simple circuit that i came across on my cd/tape player

    [​IMG]
  17. dr emulator (madmax)

    dr emulator (madmax)

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    hm here's how it should look [​IMG]
    hey what did you expect a picasso it's 1.28am;)

    oh yes that circuit would maybe need slightly refining on a powerfuller output and would also require a powered subwoofer
  18. selway89

    selway89

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    Cheers for that, interested to see what panther comes up with for me. If it can be driven by my Teac amp then all the better to lower cost.
  19. pantherx12

    pantherx12 New Member

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    Found the website sooner then I thought!

    Heres a couple that may interest you

    http://www.terralec.co.uk/loudspeaker_parts/high_power_bass_woofer_10_25cm/25864_p.html

    http://www.terralec.co.uk/loudspeaker_parts/12__200_watt_loudspeaker/18854_p.html

    There's loads on the site though ( those two are probably a bit over kill actually but hey, there cheap! ha ha can always upgrade amp later)

    you may also find this interesting http://www.loudspeakerdesign.co.uk/ : ]

    If you do decide to build your own speaker good luck and I hope you find it fun :D

    The best thing is if you do a okay job, it will outperform a retail speaker of about 3-4 times the price.

    Enjoy :p
  20. strick94u

    strick94u New Member

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    a speaker with 2.6k ohm damn! thats almost 3000 ohms what are we trying to do here
    if the guy is trying to build his own system they do make amps that work on 2ohms speakers
    you can buy them at the guitar store id go for a set of black widows fired buy a nice glass tube amp. or save some money and buy a set of computer speakers with a decent sub:slap:
  21. temp02 New Member

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    I'm not an expert in electronics but since the output already comes from an amplifier, to avoid loosing power/dBs wouldn't it be better if you use this setup:
    [​IMG]
    This way you will only (mostly) play the common sounds on the left and right speakers, ruling out (almost) sounds that are common to just one speaker (aka stereo to mono passive crossover).

    EDIT: Found some info to back up my theory at this page.
    Also on this page there is an extra circuit that with the help of some coils and capacitors try to reduce the noise generated by the extra speaker (sub) on the remaining speakers.

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    Last edited: Aug 18, 2009
  22. KH0UJ

    KH0UJ New Member

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    I think it can still power your sub speaker assuming its a double voice coil sub speaker, it can make the power amp. circuit a little hotter though, add some fans on the power amp. heatsinks then you`ll be alright;) lower resistance speaker coils can emit higher inductive feedback on the amps, that`s why it gets hotter fast, but great low freaquency bass response :rockout: I also used sub on my PC 8 inch 300 Watts 4 ohm DVC powered by 1 400 watts RMS mono amp that ived assembled myself (1 ohm stable circuit) and tuned the speaker box to 30 HZ, im happy with it:rockout:



    edit: oopps! im looking at your picture drawn:eek: you cant put together the left output and right output together bro:( assuming its a line-to-line amp, even the negative terminals cannot be put together because of the split supply (+ ground -) system, unless its a common ground power supply circuit:ohwell:
    you can just install the two outputs if your speaker is a double voice coil, in that way they are isolated to each other (left & right speaker terminals)
    Last edited: Aug 18, 2009
  23. Wile E

    Wile E Power User

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    That's only if the amp supports bridging. I doubt a run of the mill stereo receiver is capable of that.

    Regardless, with a 3ohm speaker, he's still going to be looking at a 1.5ohm impedance per channel with that setup. The receiver is only rated for 6ohms per channel. His amp will fry with that kind of load. I would attempt 4 ohms/channel happily on that receiver, but not 1.5.
  24. temp02 New Member

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    Yes you are right Wile E, I just assumed that the extra impedance needed was easy to cope with (at least to me it is, like adding an extra speaker in serial to each channel).
  25. KH0UJ

    KH0UJ New Member

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    [​IMG]

    If you really wanna utilize your existing amp. and sub, buy a matching transformer which is rated 60 Watts, that would bridge your 2 amps together without compromising the stereo amplifier, same like processors:laugh: X2 is more powerful than X1:roll:

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