Can a BFD flatten this? (1 Viewer)

[brucek]

I hope Gregg will display his response curve again. It's hard to remember what it looks like.

Wayne, I think we're all saying the same thing in a slightly different way. Each situation is unique, but I do agree with your post. I would prefer to enter as few filters as possible.

The equalizer is a voltage device that alters the flat response at its input to create an output that matches the filters we have selected. If this altered response voltage eats up your available amplifier headroom either because you boosted too much at a particular frequency or reduced a large area and subsequently increased the wholesale gain of the sub amp, it ends in the same bad result. You called this "circular equalizing" - good term.

I suppose I took the same tact that Richard did, and decided that the 70Hz area was a black hole, and if Gregg wasn't going to move his sub or seating positions, then there wasn't a lot he could do, because he already threw 16dB at it and nothing happened. That, and the fact that he has an extended peak that reaches way out past his crossover that I didn't like, I felt he might want to reduce this area and at the same time reduce the lower frequencies below 28Hz a bit. But, as you've said - if he reduces it too much and then wholesale increases his sub gain he could be right back to where he started.

In that case it would indeed be better to give the 40Hz to 80Hz boost a try while accepting the 70Hz dip...

I would take Richards advice about the remeasure at a slightly lower SPL level and see if the response has changed as a result.

I would also takes Sonnies advice of a few small location changes for the sub, moved out a bit from the corner perhaps... He should try this first, then he can decide better what to do next.....

brucek

 

[Gregg Petrarca]

Thanks everyone for all your suggestions. I've experimented with most and it's as fustrating as it's educational.
While I was contemplating my next move I glanced over at my Klipsch SW200 that the SV replaced. It was towards the left rear corner to the left of my listening position. It's about 5' from the corner as my wife has a "decorative" woodstove in the corner. Seeing I never made a raw response curve in the 5+ yrs I had it (shame on me) I figured what the heck. Just for the fun of it I placed the 16-46PCi there and graphed it as well. Here's what I got.
http://link.freepichosting.com/image...pg?x=600&y=400
I can't get over how flat it is and how the dip at 71Hz is gone. The Klipsch (pink line) is rated down to 25Hz. The
SV down to 16Hz.
What would you folks suggest I strive for for a House Curve? All I know now is the woodstove is history.
Thanks
Gregg

 

[Sonnie Parker]

Gregg,

Nevermind...I see you are working on the image as I was typing.

 

[Gregg Petrarca]

Bruce, here is the original curve with the 16-46PCi in the front left corner. I think Richard may be correct in that some room noise may have affected the lower frequencies. I may place the sub there again just to confirm.
http://link.freepichosting.com/image...pg?x=600&y=400
Gregg

 

[Wayne A. Pflughaupt]

Gregg,
I wouldn’t loose much sleep over room noises. I recently took some readings while my son was rattling dishes in the kitchen sink less than 10 ft. away. The readings were only coming up in the 70s. As soon as I fired up the first sine wave, the reading jumped a full 10dB.
Remember, anytime a low frequency tone sounds like it’s the same level as higher frequency sounds, the low tone will always be at a higher SPL level. By the time you hit frequencies low enough to induce room noises like rattling pictures, etc. the SPL of the low frequencies is so high the other noises (by comparison) won’t even register.

To test my theory, I would recommend that these measurements be done again at about 80dB, rather than

I wouldn’t recommend this in your case, Gregg, as long as you’re using the location where you took your first readings. There is a extreme 30+dB discrepancy between the highest and lowest signals. If you shift the volume down so that the highest level is only 80dB, that will put your lowest readings at 50dB. You simply cannot get accurate readings below about 65dB without the risk of the room’s ambient noise floor polluting the readings.
Regards,
Wayne A. Pflughaupt

 

[Wayne A. Pflughaupt]

Gregg,
I wouldn’t loose any sleep over room noises. I recently took some readings while my son was rattling dishes in the kitchen sink less than 10 ft. away. The readings were only coming up in the 70s. As soon as I fired up the first sine wave, the reading jumped a full 10dB.
Remember, anytime a low frequency tone sounds like it’s the same level as higher frequency sounds, the low tone will always be at a higher SPL level. By the time you hit frequencies low enough to induce room noises like rattling pictures, etc. the SPL of the low frequencies is so high the other noises by comparison won’t even register.
Richard wrote:

To test my theory, I would recommend that these measurements be done again at about 80dB, rather than 100dB...

I wouldn’t recommend this in your case, Gregg, as long as you’re using the location where you took your first readings. There is a extreme 30+dB discrepancy between the highest and lowest signals. If you shift the volume down so that the highest level is only 80dB, that will put your lowest readings at 50dB. You simply cannot get accurate readings below about 65dB without the risk of the room’s ambient noise floor polluting the readings.
At the first location you really won’t be able to reduce your scale more than about 5dB.
Regards,
Wayne A. Pflughaupt

 

[Richard Greene]

I wouldn’t loose any sleep over room noises. I recently took some readings while my son was rattling dishes in the kitchen sink less than 10 ft. away.

**********RG***********

The only room noises likely to make a difference would be walls next to the subwoofer resonating loudly or a window near the sound meter resonately loudly -- either one could add several dBs to SPL readings. In my room walls near my subwoofer rattle loudly at 18-20Hz. (the walls sound louder than the test tone!) unless I lean some heavy concrete slabs against those walls. Playing a slow sine wave sweep for a few minutes will reveal all room noises from walls, floors, windows, etc. At some frequencies the "home noises" may sound louder than the bass from the subwoofer.

1/6 octave tones are less likely to excite room noises than a frequency sweep ... but a 20Hz. test tone rattles my walls just as much as a frequency sweep passing through 20Hz. does .

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"Given the high SPL (100dB) used to measure these very low frequencies, I would expect that a portion of the SPL measurement is doubling (harmonic distortion) primarily one octave higher ... and possibly some room noises too."

**********RG***********

I forgot to mention port noises affect some ported subs

played at high SPLs. ...

With some subwoofers playing a 20Hz. tone at 100dB,

much of the sound energy measured (and heard) is

harmonic distortion at 40Hz. and other frequencies.

The sound meter doesn't tell you this, so you may believe your sub has great output at 20Hz.

But if you actually listen to music/movies at 80dB., where the harmonic distortion is much lower, you may not be able to hear/feel anything at all when there is 20Hz. content because the 20Hz. output is below the level of audibility (about 75dB).

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"If this were correct I would expect the lower frequency and its one-octave “twin” to measure at about the same SPL figure. Any thoughts, Richard?"

**********RG***********

I'm not smart enough to figure out what you mean

... so my answer may have nothing to do with your question:

Measurements below 30Hz. can be boosted by room noises at specific frequencies, port noises, harmonic distortion, the wife hollering: "turn down the volume" and neighbors banging on your walls.

The harmonic distortion increases with SPL and can be quite high at 100dB. Measurements should be done at approximately the SPL you prefer for listening to music/movies (probably 80-85dB for most people).

Looking back, I think the best advice for anyone whose

bass deviations are more than +/- 10dB using 1/6 octave tones is this:

Try other subwoofer positions -- you should be able to do better than the current sub position.

In my own listening room, where the bass sounds terrible without equalization, the 1/6 octave bass deviations are

+/-9dB before equalization (+/- 4.5dB with two bands of equalization). So +/- 15dB bass must sound pretty bad.

 

[Wayne A. Pflughaupt]

Richard,

Sorry for the delayed response, but it took some extended rumination to sort all this out.

With some subwoofers playing a 20Hz. tone at 100dB, much of the sound energy measured (and heard) is harmonic distortion at 40Hz. and other frequencies. The sound meter doesn't tell you this, so you may believe your sub has great output at 20Hz.

I have to wonder about this, too. A mic (i.e., the sensing element in the SPL meter) reacts to air pressure. It does not react to distortion per se. The meter only “sees” the air pressure from a speaker; it doesn’t “know” if the sound waves generated are “clean” or “distorted.” Distortion is typically recognized and measured by line-level testing equipment like oscilloscopes.

True, there might be a lot of distortion in that 20Hz signal, but if the mic measures so many dB of SPL, then the air movement is there.

Hope this makes sense.

Regards,

Wayne A. Pflughaupt