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It is said that it takes about 250ms signal to get those room modes ringing. RG: That's much too long! The correct time for a front wall to back wall standing wave to start would be the time it takes sound to go from your speaker to the back wall, bounce off the back wall, and then...

The white paper appears to be based on scientific principles but the science is faulty and the conclusions almost worthless to the average home theater owner. The paper should be deleted from the Harman website because it detracts from the excellent Floyd Toole papers at that website. The...

A 24dB/octave filter is nothing more than two 12dB/octave filters cascaded. A 12dB/octave low pass filter in the receiver cascaded with a 12dB/octave low pass filter in the subwoofer is the cheapskate's 24dB/octave low pass filter. Two common subwoofer problems: (1) Too much output over...

I'm not sure why you would not be able to reduce the peak at 111Hz. unless your bandwidth is too narrow and the center frequency is wrong. Most peaks are addressed with 1/6 octave (10/60) to 1/4 octave (15/60) bandwidths. Once in a while there are two adjacent peaks that need 1/3...

The goal with a BFD should be bass in a +/-5dB range. Sometimes the best you can do is +/-6dB You seem to be close to +/-5dB. The major problem getting to +/-5dB is not the peaks (the BFD can handle them) -- it's one or two nulls. You can't affect standing wave nulls with an equalizer...

The article you referenced is misleading because its goal is not the smoothest possible bass frequency response for a single listener, which most of us want. The goal of the experiment was the most consistent (not smooth) bass frequency response from seat-to-seat within a fairly large area of...

In a rectangular room (and most common room shapes) using two subs on opposite sides of the room will prevent odd-order standing waves from forming between two opposing surfaces. The common left-right subwoofer set-up places the two subwoofers out-of-polarity for the first-order axial room...

Wayne is correct that one can't EQ nulls. However you don't have nulls, you have what I like to call "partial nulls" ... and in addition, it's very likely your ears are not located at the deepest portion (weakest bass) of any of these partial nulls. A true null would have no output at all...

"I have used my subwoofers in "stereo" for years." RG I used "stereo" subwoofers from 1980 to 1994, and a mono subwoofer since 1994. If one sharply limits output above 70-80Hz. a subwoofer becomes sonically invisible almost 100% of the time while listening to music. When a subwoofer is...

What signals were used and where were you measuring from? The measurements are so good they suggest you were using pink noise or warble tones, measuring outdoors where there are no standing waves, or you placed the microphone a few inches from the subwoofer to eliminate room effects rather...

I noticed the usual misunderstanding of clipping distortion and the misconceptions about square waves / DC (there are no square waves and there is no DC current caused by amplifier clipping). Clipping distortion has only a very small effect on drivers (related to too much power going to the...

If you excite the wall's resonant frequency long enough and hard enough you may get some "nail pops". When I had my Tempest tube sub in a room corner a 20Hz. sine wave at about 100dB caused some nail pops near the subwoofer. The wall was rattling very loudly at that frequency ... but a sine...

Cabin Gain is an approximately 12dB/octave bass ramp up starting below the lowest frequency room mode whose center frequency in Hz. for a rectangular room would be approximately: 565/room length (largest room dimension) in feet. Cabin Gain will be less than 12db/octave if there are open...

Subwoofer position is an interesting topic because everyone seems to have a strong opinion, seems to believe there is one right answer for every room, and almost nobody makes measurements to collect data that would lead to at least a Rule-of-Thumb for rectangular rooms. The first goal should...

I originally designed a low Qtc (6.5 cubic foot tube filled with 8 lbs. polyester stuffing) sealed Tempest subwoofer for a 13' x 12' bedroom. It sounded fine although that use was a waste of displacement. I later moved the subwoofer to an 800 square foot living room where it gets some exercise...

Tom Nousaine usually defines a corner as having at least six feet of solid walls on both sides (no open doorways or open windows ... and even closed doors and closed windows are not so great -- potential rattle problems). I've done hundreds of measurements since I started to use corners for...

If you enjoy your music at 85dB, for an example, no matter how many subwoofers you use, you'll adjust the volume so it's about 85dB. That means adding one or more subwoofers will have no effect on the SPL you prefer. But maximum possible bass output will increase 6dB by adding a second...

Metal spikes don't "decouple" anything or absorb any energy. People read marketing hype and believe it whether it's based on real science or wishful thinking. Any energy coming out of the speaker enclosure will travel through the spikes into whatever surface they are touching. This is basic...

Bob wrote a few sentences in an otherwise good post that I'd like to correct: Bob wrote: "Remember something: the SPL meter only shows you the LOUDEST frequency." *******MY CORRECTION******** The SPL meter shows you the AVERAGE loudness of whatever sound frequencies hit the diaphragm of...

Since my last post, I installed padding under our carpet, which helps minimally, . . . *******RG: Carpet and padding absorb almost no bass . . . and have been reading about DIY and premade bass traps. You are right, though, Richard: the WAF is extremely low for these monstrosities . ...

I feel sorry for you. My dorm room at the Rochester Institute of Technology about 30 years ago was all concrete and the sound was terrible. Standing waves cause a very uneven distribution of bass frequencies in a listening room. Peaks and nulls. Or "Hot Spots" and "Cold Spots". The...

Sealed enclosures need less bracing than ported enclosures because the stuffing inside the enclosure absorbs some energy. A fully stuffed sealed enclosure requires 1.25 to 1.75lbs. polyester stuffing per cubic foot (or 1lb. fiberglass per cubic foot). 0.5lbs. polyester stuffing per cubic foot is...

In answer to the original question: The driver inside the enclosure vibrates, which "vibrates" the air in your listening room, which vibrates your eardrums. Sometimes there is also a vibrating column of air (port) in the loop. The smaller the room, the louder the deep bass due to room...

Cement surfaces cause very irregulat bass response due to standing waves. This plasterboard is more flexible so the standing waves between opposing surfaces are less extreme. Parametric EQ: You can reduce bass peaks at one seating position...

I skimmed through this long thread and didn't notice these thoughts: It's not fair to compare subwoofers heard in a car with subwoofers in a home listening room. The car is a much better environment for bass under 80Hz.: (1) There's lot's of "free" cabin gain to boost bass at the very...

Good post Shawn The BFD is used to reduce the SPL of bass peaks at one specific listening position for a smoother bass frequency response. Typical subwoofer frequency response at one listening position measured using a slow sine wave sweep is +/- 10dB or more .... but after one, two or...

Using a very slow sine wave sweep, the frequency response in a typical room measured from the listening position is roughly +/- 10 to 20dB. Your listening room is typical. (Using 1/6 octave sine waves for measurements will tend to reduce the measured deviations by few dB). You're lucky if the...

Carpet / padding is just about sonically invisible to bass frequencies under 80Hz. There are some premium pads made with closed cell foam that will absorb a little upper bass frequencies -- but I wonder whether this would be audible. Assuming your subwoofer is heavy enough to compress the...

In general, for rectangular rooms: Best integration with front speakers: = place subwoofer halfway between the speakers . . . . . . Highest output and "smoothest possible" frequency response at a variety of listening positions: ("smoothest possible" = not really smooth in most...

what did you expect for $120 (no turn on delay circuit)