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  1. #1
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    Basement Subwoofer Performance

    Hey Guys,

    Great to be back after way too long a time away. Been busy with school taking courses in chemistry, physics and calculus. These courses (actually, the work required to get good grades) has kept me away from the listening room.

    I have a question for anyone that can anwer. In a basement listening enviroment, that is, carpet on top of concrete, painted drywall, vaulted ceiling, is there much absorption of the 'slam' frequencies from subwoofers?

    Here's what I've noticed: my Mirage SS1500 (active 10 inch driver, passive 10 inch driver, and a 1 square foot enclosure) has better punch in a 9000 ft^3 space on the main floor and my 2 Servo 15s in a 4000 ft^3 basement. It doesn't make sense to me.

    I did a SPL reading in the summer. I got readings of +30 db in the range of 30 hz to 37 hz. I had the subs running from the SUB out of the receiver. Now I run the MAIN PREOUT of the receiver to the X30 crossover which one signal to the Anthem amp and another to the subs. Haven't taken any readings since.

    The house literally shook when watched Gothika, probably a result of the peak mentioned above. When I play some Dr. Dre, or Madonna, the music is kind of lifeless. The truly deep deep bass is there, but no punch or energy.

    Is this a result of the absorption rate of the basement? a phase issue?

    I'm in the process of finding a good rate for the Rane PE17 parametric EQ. Would one suffice, or would I get better performance from the subs by tuning each one separately?

    Thanks for reading this folks, I always appreciate your input.

    THOB

  2. #2
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    The problems you are experiancing are mainly related to sub placement. If your sub is placed at the culmination point of a room mode it is going to further accentuate the peaks and nulls (lotsa bass at peak and negative bass relative to the rest of the music in the null). Get yourself a 10 meter interconnect and spend a couple of hours moving the sub around. Adding a processor to the mix can give the technical aspect of the sound a flatter room response but will give the subjective aspect nothing but problems. With your technical background you may benefit greatly from checking out the Master Handbook of Acustics from your local library. It will lift a vail from much of the advertising voodoo that the industry has bombarded you with since you were an embryo.

    Also check out the highly useful 25Hz level control on the Martin Logan subwoofers. It gives you 12db of cut/gain centered at 25Hz without affecting the critical midbass region.

    Good luck.

  3. #3
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by the hand of boredom
    Hey Guys,

    Great to be back after way too long a time away. Been busy with school taking courses in chemistry, physics and calculus. These courses (actually, the work required to get good grades) has kept me away from the listening room.
    Welcome back, looks like the hand wasn't all that bored!!! LOL

    I have a question for anyone that can anwer. In a basement listening enviroment, that is, carpet on top of concrete, painted drywall, vaulted ceiling, is there much absorption of the 'slam' frequencies from subwoofers?
    The drywall usually will resonate a bit, and that usually provides for some absorption. If the ceiling is pretty high, it will lower the tone of the room resonance(floor to ceiling reflections). Providing the deminisions of the room would help alot.

    Here's what I've noticed: my Mirage SS1500 (active 10 inch driver, passive 10 inch driver, and a 1 square foot enclosure) has better punch in a 9000 ft^3 space on the main floor and my 2 Servo 15s in a 4000 ft^3 basement. It doesn't make sense to me.

    I did a SPL reading in the summer. I got readings of +30 db in the range of 30 hz to 37 hz. I had the subs running from the SUB out of the receiver. Now I run the MAIN PREOUT of the receiver to the X30 crossover which one signal to the Anthem amp and another to the subs. Haven't taken any readings since.

    The house literally shook when watched Gothika, probably a result of the peak mentioned above. When I play some Dr. Dre, or Madonna, the music is kind of lifeless. The truly deep deep bass is there, but no punch or energy.

    Is this a result of the absorption rate of the basement? a phase issue?
    I think you have answered you own question. If you have a very elevated deep bass response, it will make it seem like the mid and upper bass has the life sucked out of it. The slam in drum kick's is in the 60-100hz region.


    I'm in the process of finding a good rate for the Rane PE17 parametric EQ. Would one suffice, or would I get better performance from the subs by tuning each one separately?
    Thanks for reading this folks, I always appreciate your input.

    THOB
    Unless they are going to be side by side, or on top of each other, I would eq them seperately. If you placed two subs in opposite corners, they are very likely going to have a different frequency response. That is because each loads the room differently because of their different location. The object is to get them both to sound and measure VERY closely, if not indentically.
    Sir Terrence

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  4. #4
    Forum Regular Woochifer's Avatar
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    T-man nailed it. A peak that huge in the lower bass range will lead you to set the bass according to that level, which will make all of the other bass sounds seem lifeless or nonexistent. By removing that peak with the EQ, placement, and/or room treatments, it allows you to actually the raise the overall subwoofer level without that one extremely loud peak dictating what you hear (if you have that one note that shakes your room, you're going to set the level so that one note doesn't pound your skull into submission; but, in doing so you make everything else too low). With a flatter in-room frequency response, the bass sounds fuller and more balanced.

    Absorption is more beneficial in the higher frequencies. With the bass range, it's more about the placement, room dimensions, and equalization. Bass traps in the corner are more effective than other room treatments.

  5. #5
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    Merci pour L'information...

    The hand is quite bored, but that is because a young female has entered my life.

    The dimensions of the room: left wall 16 ft, back wall 14 ft, right wall 10 ft and then opens into the hallway, the front wall is 20 ft across. The ceiling is 8 ft high.

    The centre of the left subbie 3 ft from the left wall and along the front wall, the centre of the subs are 7 ft apart.

    Lifeless. That would be the one word I would use to describe the impact from music. I'm very limited to placement options. The mains are sitting directly atop the subs. The rack is in the left corner, and the TV is between the speakers.

    Sir, you would recommend two channels of eq? One per sub, is what you are saying. I've got a connection at a local retailer that can bring in the PE17 at just above cost. The dollar is booming right now so I can get a good rate on the exchange (actually, your dollar is taking a dump at the moment). I'm likely looking at just over $900 CDN including the taxes for two.

    When I'm ready to do the final tuning, do I begin by sending sine waves through the mains only to see where the roll-off begins? Adjust the crossover, take SPLs of each sub, and then tune each sub? Do I have it right?

    I'll keep you updated. The holidays are just around the corner, the folks said they might reward me if I can keep the grades up.

    THoB

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