How much does an amp add or take away from a duy sub?

Discussion in 'Archived Threads 2001-2004' started by Adam O, Aug 15, 2002.

  1. Adam O

    Adam O Stunt Coordinator

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    Im currently running my 15" Dayton DVC sub with an old 100w RMS plate amp I had on my old powered sub. I felt the sub was doing just fine, until I stopped by Soundsaround today. They had a fairly reasonable system set up, with 2 small towers and 1 powered sub. The sub was tiny and was just playing fm-radio but had put out more clean crisp base then by sub puts out at alot lower volume. The price on this sub was 750CND I cant recall the brand.
    To say the least I was dissapointed with my diy sub, Im wondering If I go get a 250w RMS + amp I will notice an improvement, or should I redesign my sub altogether? BTW here are the specs on the sub I built:
    24" Sonotube X 32" high = 237L when empty
    6" wide Port, 21" Long = tunning freq of 19.5
    This leaves be with about 210L internally, Correct?
    I Have stuffed it to the brim with fibre glass insalation, is this right?
    Im thinking that if this is all correct and should work Im going to need a new amp: What would be a good amp for under $325CND?....Damnit guys i need more ears bleeding and currently they arnt even soar[​IMG]
    Thanks for all your advice and your suggestions in advance,
    Adam
     
  2. Brian Bunge

    Brian Bunge Producer

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    Adam,

    I don't understand why you've stuffed it so full of polyfil. I'd think that lining the walls would be more than sufficient. It's possible that you could be impeding airflow out of the port, which could affect performance. Also, is the current amp stable to 4 ohms? I don't really think 100W is much for this particular sub.

    Brian
     
  3. Craig Woodhall

    Craig Woodhall Supporting Actor

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    Adam,

    you are way underpowering it.. When I had my 15" tempests, I went from 200w to 500w and the difference was night and day.. I had a Dayton DVC before and you need to send it as much clean power as you can afford.. I also agree with Brian, check the airflow, too my fill.

    Craig
     
  4. Adam O

    Adam O Stunt Coordinator

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    oh wow thats good to here me engineering of the sub isnt at fault [​IMG]. What amp would u recommend then?? I think 250w would be the minimum.
    Would the 250w PE plate amp be good enough? or should I look into something with 300-400watts?
    Thanks for the quick replies guys.
    Adam
     
  5. Robin Smith

    Robin Smith Stunt Coordinator

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    Is your tuning frequency calculated with the amount of stuffing taken into account? If not, you have dropped the tuning freq way down by stuffing it so much. I am not the technical god at this, but the stuffing increases the perceived volume which means that the port length is essentially

    FYI, I have a 15" Dayton DVC, 214L net internal volume, tuned to 15.4 Hz. I power it with the MCM Electronics 250W plate amp that I got on sale. I lined my sub with one layer of batting and that's it. No stuffing whatsoever. I am more than happy with the performance of my sub.

    I woud start by removeing as much fill as possible and see (since it a free change you can try).

    Then make the investment in a good 250W sub. My sub was ~$270CAN shipped to my door, so it meets your budget. I waited and bought it when they went on sale.

    Further, many retail subs have artificial bass boost in the 25 - 35 Hz range. Often this is the pounding bass frequency that people initially lust after. Your DIY sub (dependent on the amp of course) may have a different boost or no boost which would affect your impression of this sound.

    If you are going for faithful reproduction, you want no boost. If you want punch in the guts, shit-eating grin boomy bass, a boost might be your bag.

    I opted for the more accurate reproduction route and removed the bass boost on my amp. I am happy with the result. If you can find info on your amp, try to see if it has a boost and if so can it be modified. This may also give you the results you need for free/cheap.

    Hope this helps


    Robin Smith
     
  6. Adam O

    Adam O Stunt Coordinator

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    When building I thought the amp im using might have a bass boost but it does not, according to the maker who I contacted.
    On another, unintelligent note, NO I did not take into consideration the amount of fill in the sub [​IMG] Does this mean if I add any fill into the tube I have to shorten the port proportionally or risk my tuning freq to drop? How exactly would I calculate the amount of polyfill I need then and how long should the port be?
    Thanks alot for the info.
    ADam
     
  7. Joe Tilley

    Joe Tilley Supporting Actor

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    Adam the PE 250 watt plate amp will do fine. I have the same sub & amp in a 270 liter sono tuned to 17hz & it sounds awsom. I too think you are underpowering it. A better amp & removeing some of that fill would probley clean it up quite a bit.
     
  8. Bryan Michael

    Bryan Michael Supporting Actor

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    the thing with boost is that if you play your sub loud you will get a peak with it and that frequency might distroy your sub if the bost is too much i would rather use a eq to bost than a stock bost you can custommise the bass to your taste
     

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