"blending" the subwoofer with the mains.

[ArkiStan]

I was at Audioreview.com looking at reviews for some home SUBWOOFERS and read what one of the reviewers had wrote:

"I highly suggest obtaing a test CD with 1/3 octave pink noise bands and a $35 Radio Shack sound pressure meter to use as a set up aid to blend the sub in with mains smoothly."

wow..I didn't know this was necessary.

[ArkiStan]

Also, someone wrote this as one of the cons about one of the subwoofers I was looking at. What does it mean??

"Mad woofer bump from Sub Out on A/V Receiver. Scary. Much better using Spkr Lvl outs w/built-in crossover. Bit more wiring though."

[Leon]

Originally posted by ucbstan
I was at Audioreview.com looking at reviews for some home SUBWOOFERS and read what one of the reviewers had wrote:

"I highly suggest obtaing a test CD with 1/3 octave pink noise bands and a $35 Radio Shack sound pressure meter to use as a set up aid to blend the sub in with mains smoothly."

wow..I didn't know this was necessary.

You'll fine that audiophiles are very extreme. But they are correct. You want the sub to "blend" with your other speakers. This is more important for music, and less important for movies. You want the sub to sound clean and tight without any boominess or chestiness. Some of it can be adjusted through the phase setting.

You probably won't need the SPL to adjust the sub. Just pop in a good music CD and go by ear. Have a friend adjust the crossover frequency and phase while you are closing your eyes and sitting on the couch.

Also, subwoofer placement matters too. Here's what Polk Audio say about that:

PLACEMENT

Room acoustics have an enormous impact on the sound of speakers, including subwoofers. A phenomenon called "standing waves" makes bass response uneven from place to place in your room. To experience this for yourself, put on a CD with a strong, consistent bass line. Notice how the volume of the bass goes up and down as you move around the room. Stand in one place and then squat down-you will probably notice that the bass changes in the vertical plane as well!

Because the subwoofer's location affects how standing waves are created, the first step to getting accurate bass response is finding the right spots for your subwoofer and your listening position. We'll share a few guidelines that may be helpful, but in the long run nothing beats trial, error and your own two ears.

Stick It In The Corner-
This is the advice most often given and it certainly will yield loud bass. But corner mounting may make the woofer sound "one note-ey," and boomy on music. If lack of bass volume is your biggest subwoofer problem, this may be the answer for you.

Avoid Sitting Up Against the Wall-
Bass waves build up and "hang out" at room boundaries (walls). Your system will sound thick and heavy when your listening chair is up against a wall. If you must sit against the wall because of furniture layout, place your subwoofer away from walls and corners.

Avoid Symmetrical Placement-
"Avoid putting the subwoofer the same distance from two walls. For example, if you have a 20' wide room, don't put the subwoofer 10' from each wall. Similarly, don't put the subwoofer near a corner and equidistant from the side and rear walls. Instead, stagger the distances to each wall."1

Put The Subwoofer As Close To The Main Speakers As Possible-
Even though bass sounds are non-localizable, cabinet resonance and other factors conspire to make this less true in practice than in theory. It'll be much easier to get seamless blending between sub and main speakers if they are on the same side of the room. If possible, put the subwoofer behind the plane of the main speakers. At very least, keep the subwoofer in the front half of the room.

Here's An Old Trick-
Put your woofer in the same spot as your listening position. It's best to raise the subwoofer off the ground to seated ear height (use a sturdy, non-resonant platform). "Play a piece of music with an ascending and descending bass line such as a 'walking' bass in straight-ahead jazz [see recording suggestions]. Crawl around the floor on your hands and knees…until you find the spot where the bass sounds smoothest, and where each bass note has about the same volume and clarity. Avoid positions where some notes 'hang' longer and/or sound slower or thicker than others. When you've determined where the bass sounds best, put the subwoofer there."1

Use Two Subwoofers-
Using two asymmetrically placed subs will minimize the effects of standing waves in your room, yielding smoother bass response (as well as better dynamic range). But don't run out and buy another sub just yet. Get the sub you have now to sound its best before spending more money. You may be perfectly happy with just one sub once you've tried our suggestions.


ADJUSTMENTS:


Setting Level-
"Get a suitable test CD [or DVD, see list below] with sine wave signals or warble tones covering the range of 20Hz to 200Hz or so…Using a sound level meter [analog model available at Radio Shack, catalog #33-2050], match the output at the listening position at 50Hz and 150Hz [using 'C' weighting and 'slow' meter response] by adjusting the volume control of the subwoofer. Make sure the volume control on your preamp [or receiver] remains at the exact same volume."2

If you don't have a meter or test discs, use a CD with vocals and a consistent acoustic bass line and set level to the point where the upper and lower ranges of the bass sound well balanced.

Setting Low Pass Filter (Crossover)-
If your main speakers are full size with good bass response, set the low pass filter to 60Hz - 80Hz to start. If your main speakers are bookshelf designs, set the low pass filter in the 80Hz - 100Hz range. If you have compact satellites, set the low pass filter to 150Hz to start. Put on a test CD or DVD with test tones. "With a fixed input level, carefully measure the output level at the listening position for each…interval between 30 and 200Hz and write it down or make a line plot on a sheet of graph paper…Listen while you measure. You hear differently than the sound level meter does…trust your ears, not the meter."2 Raise or lower the low-pass filter setting on the subwoofer to achieve the smoothest response. Turn the low pass filter down if there's an excess of output around the crossover point, turn it up if there's a response dip.

Do not be alarmed if you have response variations of several dB from test tone to test tone. You are seeing normal variations in response caused by the speaker's interaction with the room. Absolute flat response is a worthy but somewhat unrealistic expectation in most systems and rooms.

If you don't have a meter and test disc, use your ear to make this setting. Put on a CD with male voice and a consistent bass line. Adjust the low-pass filter until the male voice sounds "full" and natural but not thick and heavy.

Setting Phase (Polarity)-
"Using a [test] signal at the nominal crossover frequency [you set in the step above], set the phase of the subwoofer(s) to deliver the highest output at the listening position."2 It helps to have a friend on hand to change the polarity setting on the sub while you measure and listen.

Some subwoofers do not have phase adjustment switches or knobs. With these subs it's even more important to position the sub as close to the main speakers as possible.


Here's the site:
http://www.polkaudio.com/home/faqad/

[Leon]

Originally posted by ucbstan
Also, someone wrote this as one of the cons about one of the subwoofers I was looking at. What does it mean??

"Mad woofer bump from Sub Out on A/V Receiver. Scary. Much better using Spkr Lvl outs w/built-in crossover. Bit more wiring though."



I think this is refering to the fact that a lot of the lower-end receivers have internal crossovers that aren't set correctly. The crossovers in a powered sub are usually much better since they are adjustable.

Basically, your receiver has a crossover and your powered sub has a crossover. When these two filters combine, it cause some irregularities in the frequency response.

Here's the page with more info:
http://www.polkaudio.com/home/faqad/advice.php?article=bassmanage

[ArkiStan]

awesome dude!! thanks for the info. now get some freakin sleep!

by the way, could you explain what a "crossover" is? I always guessed it means something like the "volume" of the bass.

Also, people always talk about "setting their woofers to [certain frequencies like 20hz-200hz]" is that the same thing as teh crossover business?

But not quite sure...I've always wondered.

[Edited by ucbstan on 05-09-2001 at 02:09 AM]

[Leon]

Oh... A crossover is just the electronics in the sub or receiver that separates out the lower frequencies. That way only the lows get passed out to the sub. That's putting it in simple terms.

[ArkiStan]

Aha~! I see....

so by turning the crossover dial on the subwoofer you would amplify or reduce the level of bass you're getting? I get it.

It wasn't that complicated after all. thanks again.

[Leon]

haha.. not quite. You don't amplify the bass with the dial. You change the frequency.

[ArkiStan]

HAHA, YES!! :D I just realized that as I was reading through the Polk Bass Management page. Wow, this page is REALLY informative. But one final question: Ok, so here's the deal w/ my setup. (After this I probably won't have to bug you anymore Leon, hehe)

I (plan to) have:
Energy Take 5's
a separate powered sub (soon)
Yamaha HTR-5240 (soon)

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

so I found the following instructions for my setup:

Bookshelf Speaker With Single 6" or Smaller Woofer (Such As RT35i's) With A Separate Powered Subwoofer
Select front as "Small." If the sub out jack is unfiltered, connect one of the line inputs of the subwoofer to the sub out jack of your electronics and set the subs low pass filter to taste. If the sub out jack is filtered, either use an unfiltered input on the sub (if it has one) or use a line input and turn the sub's variable low-pass filter all the way up.

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

right? Ok, let's see if I can explain all this without burning my brains out:

My Yamaha HTR-5240 receiver's sub output is filtered. And according to the manual, my sub has "both line input and speaker-level inputs, so it can be connected to any receiver or amplifier." (I assume that means the sub has an unfiltered input)

So conclusion is that the best thing I can do is to
set the speakers to "small" and then connect the receiver's sub out to the sub's "Speaker Level inputs" so that only the receiver's crossover is in effect....

Please tell me I'm right... :splat:

[Leon]

It depends on your subwoofer. Your receiver probably has a built-in crossover, so Polk Audio recommends that you use this method:

http://www.polkaudio.com/images/global/spkrconect.jpg


However, I don't like using the sub's amp to power speakers. That's just an extra load on it. I know what using the sub line input will get you a "double filter", but I think I would rather have that than push the sub's amp too far.

I think... It's too late now.. I'm not thinking clearly.