phase shifts

[dimmie]

hey,

Can somebody tell me what happens exactly when phase shift occurs. and what I can do to remedy it.

Because I get the feeling that the more filters I create, the bigger these differences become, or are certain frequencies more sensitive to changing phase?.

Because after listening to several movies, the bass can sometimes be a bit annoying still, even though I have a relatively flat response. can this be a phase issue?. It sometimes sounds like there is still slight boomyness going on.

Dimitri

[brucek]

Because after listening to several movies, the bass can sometimes be a bit annoying still, even though I have a relatively flat response. can this be a phase issue?. Because after listening to several movies, the bass can sometimes be a bit annoying still, even though I have a relatively flat response. can this be a phase issue?.

You have a very flat response. The person sitting where this reading was taken will not likely experience any boominess in the bass. In fact, they might think it needs a bit more bass.

This is not a phase issue. With a single sub, phase issues are a problem around the crossover region caused by an interaction with the mains speakers that are producing those same frequencies.. It can cause a dip or a peak at those frequencies. You don't have that problem.

What the problem might be is the differences between different seating positions.

To establish this, take response checks at various seats and see if there is a peak that causes the boom. Many people adjust their filters to average a good response over a wide area, rather than optimizing a single area at the expense of all other positions..

brucek

[dimmie]

Do you feel that determening phase with one speaker in rew, is accurate?. because i switched between left and right and got completely different readings. Probably because of the imbalance acousticly between my left and right soundstage though.

[brucek]

Do you feel that determening phase with one speaker in rew, is accurate?.

Well, I know REW is a mono signal where soundstage isn't an issue, but I tend to think it makes more sense to use both the left and right mains when testing interaction. Either way, your complain is boominess. That isn't the result of a crossover problem...

brucek

[dimmie]

use both the left and right mains when testing interaction.

Is that possible using rew?, because I get either left or right main depending on which input I use(white or red) on the amp.

One more: when determening distance of the sub, do I meassure from the center of the driver, or the center between the driver and port?. I've got the monolith downfiring.

Dimitri

[brucek]

Is that possible using rew?, because I get either left or right main depending on which input I use(white or red) on the amp.

Simply use a Y-splitter and feed both left and right input...

when determening distance of the sub, do I meassure from the center of the driver, or the center between the driver and port?

Not enough difference to really matter....

brucek

[dimmie]

ok, thanks.

I'm gonna change my setup and positioning next week, and put my monolith out in the open, which should give me better results. especially in the lower region. maybe I can get better results.

dimitri

[Wayne A. Pflughaupt]

Because I get the feeling that the more filters I create, the bigger these differences become, or are certain frequencies more sensitive to changing phase?

It’s commonly said that equalizer filters do add phase issues, obviously at the frequencies they’re affecting, but it generally isn’t anything audible.

In any event, it won’t have anything to do with the boominess problem you’re having. That might be because your sub is too flat. Typically that leads to the upper bass sounding hot, and the ultra-lows sounding weak.

Do you feel that determening phase with one speaker in rew, is accurate?. because i switched between left and right and got completely different readings. Probably because of the imbalance acousticly between my left and right soundstage though

The measurement difference is a function of the physical distance between the sub/main speaker combo and your ears. Obviously it’s going to be different measurements, because the sub is closer to one speaker than the other. There isn’t really anything you can do about it. Typically the best remedy is what brucek advised - deal with combined response.

I'm gonna change my setup and positioning next week, and put my monolith out in the open

If by “out in the open” you mean closer to the middle of the room, that seldom gets anything but bad results.

Regards,
Wayne

[dimmie]

I've placed the sub in a different corner. and the response has changed quite a bit compared to my previous setup. I expected a better response, but this one isn't very good either. but the bfd will probably fix it.

I've also found that you can have room resonances even when the response is at 75 db. at that particulair frequency. Because when I take manual readings, some frequencies still sound a bit harsh and need to be adressed.

My unfiltered response

[dimmie]

This is what I came up with last night after some experimenting. although it doesn't look very good, it sounds pretty ok. I checked this response manually and smoothed out some those resonances that were still there in the background.

[Josuah]

Well, the biggest thing seems to be that you fixed that major null, but in doing so you lost some low-end extension. Can you find a better placement point and get both?

[dimmie]

I can probably boost it, should I?.

[Josuah]

Sorry, I meant by placement. I'm guessing the first graph was closer to a wall or corner, while the second graph was somewhere not as close, but a different distance from your seating position or positioned at a length from the walls that prevents the null.

So maybe you can find a corner or near-wall location that will boost your low frequencies again, while still having a position that prevents the null at your seat.

You probably don't want to boost it using EQ, because then you might overdrive your sub.