2 subs or 1?

Discussion in 'Speakers & Subwoofers' started by ChrisLazarko, Aug 27, 2003.

  1. ChrisLazarko

    ChrisLazarko Supporting Actor

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    I was wondering if I should purchase another sub for my system. It currently consists of:

    Harman/Kardon AVR-325 reciever
    Klipsch Quintet 5 piece speaker
    Polk Audio PSW250 subwoofer.

    The sub doesn't get the REAL deep frequency but does a good job for movies still.

    Now they say bass is not directional but I can tell the bass is coming from the front of the room. Now if I add something like a Klipsch RW-10 into the picture and put that in the front, then take the Polk Audio PSW250 and put that in the back would a see a big performance increase.

    Currently the tv is in the front of the room, couches in the middle of the room and then in the back I just have my two surrounds along with 2 cabinets.

    I have room to add the sub and I was wondering if it would make the room sound "more alive" in a way or not by adding the stronger bass in the front and then a little weaker bass in the back.

    Thank you for any input.
     
  2. Wayne A. Pflughaupt

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    Chris,

    You’ll probably get as many different opinions on this topic as you do responses. Here’s mine.

    First, it is not a good idea to have non-matching subs (if you use two). Especially subs that are drastically dissimilar, like the 8” vs. 10” you’re considering.

    For instance, for the sake of argument let’s say that maximum output of both subs is the same. We can assume that the 10” sub will have better extension; let’s say it easily gets down to 25Hz, but the 8” only goes to 40. Assuming again that both subs are in the same corner, adding the 8” sub will increase overall output by about 6dB between 100 and 40Hz. But below 40Hz the small subs rolls out, so that means response of everything below 40Hz is down a substantial 6dB. By contrast, if only the single 10” sub was being used, response would not start to drop off until 25Hz.

    Thus the addition of the smaller sub will increase overall output, but at the same time it will “drag up” extension, because only one sub will be reproducing the lowest frequencies.

    If they do happen to have similar extension, but the smaller sub has less output than the larger, the larger sub will effectively “mask” the smaller, and the latter will contribute virtually nothing to overall output.

    Second, in most rooms there is only one location that delivers the best sub response. So why add a second sub to a location that will insure its poor performance?

    Third, when you separate two subs you end up with phase and cancellation issues that will make overall bass response rougher. So measured performance is typically worse than with the single, optimally placed sub.

     
  3. Jaime B

    Jaime B Stunt Coordinator

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    Chris:

    I was going to post a reply, but Wayne stole the show!
    Bass notes are "non-directional" to about (rule of thumb) 100 hz. Not in every room will this hold true, but your Polk, as Wayne very well explained, is probably covering frequencies way above the 100hz. range. I agree 24 db slopes are best to filter unwanted output above a given cut-off freq. in a sub.

    JaimeB
     
  4. ChrisLazarko

    ChrisLazarko Supporting Actor

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    Well I never figured all that and I have to say Wayne you do a very good job of explaining. You could sell an audio product easy to me i'll give you that.

    Well my speakers are satellites and there mid-ranges are only 3 1/2 inches so it wouldn't suprise me they don't cover anything lower than say 120Hz or so even though they are rated for 100Hz.

    Also, the subwoofers crossover I think is a little high as well myself as when I will adjust the setting on my EQ the sub doesn't really stop responding until I adjust the 250Hz so I figure it probably ends somewhere a little before 200Hz.

    I'e been thinking about the Klipsch RW series and have been looking at it very much. Great price and of course I love Klipsch myself. I haven't heard there RW line but there RSW was a decent subwoofer. Of course SVS would be a better choice but in the front of the room I don't have room and a round cylinder would look out of place, as well as the price.

    Wayne, what do you mean by the subs cancelling each other out. I would just figure the front would have more bass output while the back would have a little less. So basically it would sound like the room is enveloped in the low freq. but the front would be stronger than the back. Correct me if I am wrong but I thought that was all it would do.

    Also, I don't know if you guys are familiar with HK recievers, but on the 225 is there anyway to adjust the crossover for the sub or for that matter even my main speakers?
     
  5. Wayne A. Pflughaupt

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  6. ChrisLazarko

    ChrisLazarko Supporting Actor

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    Well I wouldn't say it is bad, for the price I think it is actually pretty good but your right in an all-around prespective for a little bit more you can get much better performance.

    I think I will go for that Klipsch RW series sometime soon, you sold me Wayne.
     

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