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Subwoofer testing in the center of the room. What orientation?


yoha

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Hi folks,

I browsed the topics some of you posted on how to test the most appropriate placement for your sub. I noticed that you experts out there suggested placing the subwoofer on the sweet spot, crawled around the room while music is playing to find the best spot to put the sub at. My question is

1) how should the orientation of the sub be at the sweet spot during testing, should the sub's front circular shape thing be facing the front, left, right, back? i have a rw-12.

2) Also, on my current config(you can take a look here: http://members.cox.net/zer0sn0nes/system1.jpg), my sub is placed on the corner of the room. Standing/sitting on 3 corners of the room, i can feel the bass output very much, whereas if i sit on the center of the room(the sweetspot), i dont feel it alot. is this normal? or more importantly, the current placement of the sub is not ideal, that's why i hear the bass this way?

3) btw, what is a port? i read that some of you refer to the port, the driver. isnt the driver the circular shape thing that vibrates when the bass is output? how about the port?

4) lastly, for the sub placement testing, how one should decide the most optimal sound? is it not too much bass, etc?

Thank you for your insights.

Best Regards,

Yohannes

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On 12/8/2004 6:55:37 PM yoha wrote:

Hi folks,

I browsed the topics some of you posted on how to test the most appropriate placement for your sub. I noticed that you experts out there suggested placing the subwoofer on the sweet spot, crawled around the room while music is playing to find the best spot to put the sub at. My question is

1) how should the orientation of the sub be at the sweet spot during testing, should the sub's front circular shape thing be facing the front, left, right, back? i have a rw-12.

2) Also, on my current config(you can take a look here:
), my sub is placed on the corner of the room. Standing/sitting on 3 corners of the room, i can feel the bass output very much, whereas if i sit on the center of the room(the sweetspot), i dont feel it alot. is this normal? or more importantly, the current placement of the sub is not ideal, that's why i hear the bass this way?

3) btw, what is a port? i read that some of you refer to the port, the driver. isnt the driver the circular shape thing that vibrates when the bass is output? how about the port?

4) lastly, for the sub placement testing, how one should decide the most optimal sound? is it not too much bass, etc?

Thank you for your insights.

Best Regards,

Yohannes

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Answers...

1) The fastest way would be to position the subwoofer where you will sit,play material with deep bass and crawl(like a dog)around the room (alongside the walls)to find the spot with the ebst sounding TO YOU bass.

2)This tells me your sub is nNOT in the optimal position for YOUR sitting position.Go to number one and find the best spot.Correct a better spot must be found

3)A port is a form of a vent,be it a Tube(cylinder of air moving in and out) or a Passive Radiator(looks like the woofer,has a piston and NO MOTOR STRUCTURE).The Passive Radiator or PR is set in motion by the pressure created inside the box by the woofer(active driver)and PR's as are the tube ports can be tuned to whatever frequency the designer choses for optimal performance.

4)Optimal sound should be as linear as possible with TEST TONES,ideal to YOU can be what type of sound YOU prefer.Too much bass or any frequency is called a PEAK and degraed what can be viewed as IDEAL SOUND.Gaps in frequency response and dips are also anomalies.

Try to cross over the sub around where your main speakers(fronts)start to cut out.For a serious setup you need a frequency generator or test CD.And if you can a SPL meter.Can be done by ear also.

This better help 7.gif2.gif

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TheEar,

Thank you for your response to my questions. However on the 1st question, you miss to mention the orientation of the sub on the sweetspot. where should i position the front woofer(circular shape thing) during testing on the listening position? should it be facing the front of the room, the sides of the room, or the back of the room.

Thanks for your insights.

Best Regards,

Yohannes

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TheEAR,

One more thing. you mentioned that i should try to crossover my sub around where my mains start to cut. My fronts' frequency response is @ 75-20kHz ±3dB and my sub is @ 21-120Hz ±3dB, therefore following your suggestion, it will be justified to set the crossover at either my receiver or sub at 75Hz?

Thanks for your inputs.

Best Regards,

Yohannes

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On 12/8/2004 9:11:15 PM yoha wrote:

TheEAR,

One more thing. you mentioned that i should try to crossover my sub around where my mains start to cut. My fronts' frequency response is @ 75-20kHz ±3dB and my sub is @ 21-120Hz ±3dB, therefore following your suggestion, it will be justified to set the crossover at either my receiver or sub at 75Hz?

Thanks for your inputs.

Best Regards,

Yohannes

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Well 80Hz is the frequency below which you can't tell the direction of the sounds coming at you. It's for this reason that the typically sub crossover point is set to 80Hz. That said, 75Hz would be just fine.

In regards to your original questions:

1) The orientation of the sub really doesn't matter, but if I were doing the test I'd just point the sub forward.

2) The reason you hear the bass in the corners and not in the middle is due to destructive interference caused by the acoustics of your room. What happens is the bass signal bounces off the wall and then cancels itself out (usually in the middle). The best way to get rid of this is to purchase bass traps and put them in the corners. Adjusting placement of the sub however will help to reduce these problems, but they will always be there.

3) A port is a mass of air (or in the case of a passive radiator, a mass of an unpowered woofer) that resonates at a certain frequency. A port is generally tuned to resonate at a frequency just as the driver's response starts to cut out. A port just extends the LF response of a speaker.

4) The optimum location of the sub is a location such that you have the flattest low frequency response possible. If you don't have any measuring equipment, then the best location is where it's the loudest, but not boomy. Boomy would be a location that is amplifying a narrow frequency band (think of the car subs that blast down the street...this is a bad sound). A good bass sound will sound powerful and full (and of course loud). The best way to do this is to play very bass heavy music when adjusting the location of the sub...listen for a bit and tweak the location. You'll know when you've found a good spot.

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· Given your main speakers are 3db at 75Hz as well as most movies are mixed for 80Hz and THX specifies 80Hz as well... I'd recommend the 80Hz. Not that 75Hz is incorrect as I'm sure it would not be audibly different.

· The reason drWHO mentioned that the orientation of the driver is insignificant... comes from the fact the bass wavelengths are long and probably won't be affected by it's orientation in the middle of the room.

· Without going into any complex analysis... pink noise (often built in the receiver) and a SPL meter (radioshack has an inexpensive one) will allow you to alternate through each channel and adjust each volume to the same loudness. As THEear mentionned, you can do this by ear... the SPL meter just makes it quicker, and easier.

Later...

Rob

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On 12/8/2004 9:11:15 PM yoha wrote:

TheEAR,

One more thing. you mentioned that i should try to crossover my sub around where my mains start to cut. My fronts' frequency response is @ 75-20kHz ±3dB and my sub is @ 21-120Hz ±3dB, therefore following your suggestion, it will be justified to set the crossover at either my receiver or sub at 75Hz?

Thanks for your inputs.

Best Regards,

Yohannes

----------------

The classic 80Hz cutoff would be great,as at 75Hz the speakers are 3dB down.

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