Sub position/phase graphs

[RonS1958]

Hello again to all,
I have spent the last week on and off positioning my subwoofer and trying different things. I had previously only tried two positions in the past for the sub as I did not think I had another option. But after realizing that I could not get rid of the undesirable peak at 30Hz with either, I tried another position behind the front door in a little entrance area into the room. (I had thought it was impractical, but after putting it there, well.)

It was a very pronounced improvement. At this point I changed the crossover from 80Hz to 120Hz. Once again the improvement was exceptional. My center channel (which has to be "tamed" to not dominate) goes down to 110 Hz, so I figure that's where that improvement came from...? The improvements I noticed was that bass is much tighter,smoother and vocals are clearer with small inflections more noticeable, just all around much improved. I am very pleased. While trying to flatten the sub response more, I did notice that while increasing gain improved the measurement, it made the bass too boomy. Is that normal? Is that a thing that room treatments could address?
I will leave well enough alone in regards to these two settings for now.
(I need to mention that I will not be equalizing as I have no preamp jacks.)
I have moved onto trying to integrate the mains and the sub and I don't know if normal or reverse sounds better or not by ear. It appears that reverse is better in the measurement but what do you think? Red is normal phase, other is reverse.

I only understand a minimal of what this whole REW thing is, but I know that my sound is already much improved by doing what I have so far. Any advice on what to pursue next, (or go back to again) would be appreciated.
Thanks,
Ron

[brucek]

Red is normal phase, other is reverse.

The reverse appears to smooth the dip at 85Hz, so I would leave it there.

Overall, the response is quite good, but you're measuring quite high. Take your measurements at 75dBSPL.

brucek

[RonS1958]

I have been trying to measure at a lower level, but I keep running into levels low message and it seems that the only way I can get it okay and have the RSmeter actually register a reading is to put it at the 80db range and raise the volume on the receiver. I do not know why this would be. I can start off with roughly correct levels but as I try different settings( sub gain, crossover settings) the REW test signal drops in volume and then I run into struggles. Should I be recalibrating each time I change a setting that affects the output level?
Thanks,
Ron

[brucek]

Should I be recalibrating each time I change a setting that affects the output level?

Yes.

Also remember to run the Calibrate routine directly after you run Check Levels, so that the REW SPL meter and the real SPL meter are the same.

brucek

[Wayne A. Pflughaupt]

I did notice that while increasing gain improved the measurement, it made the bass too boomy. Is that normal? Is that a thing that room treatments could address?

It should naturally be expected that increasing the sub's level, by any means, can make it sound boomy if it is too loud compared to the mains. No need to employ room treatments to solve a problem that can be addressed by merely turning down the sub's volume control...

Regards,
Wayne

[brucek]

I did notice that while increasing gain improved the measurement, it made the bass too boomy.

Well, the EQ curve of your hearing changes with level. The louder the sound, the flatter your frequency response. That's why we have different EQ filters for SPL meters (i.e. A, B and C weighting filters). In the case of REW, we apply calibration files to render all meters and mics flat. Then, if you want a more pronounced bass, you can add a house curve. It's important to do your measurements at a 75dBSPL target.....

brucek

[RonS1958]

Hello again to all,
I have been at it again, trying to get the measuring levels down. I went through the setup again and everything goes fine until I actually go to measure. When I calibrate the meter, REW reads the same as the RS meter. When I go into the actual measurement, REW says the level is too low but I notice that the input reading is the same db as what it is on the receiver and the RS meter gets a good reading in the 80 db range. I believe that I read in another post that that can actually be okay as long as you still get a good measurement. Is that correct? When I actually measure the signal, the RSmeter reads fine but the REW meter reads about 8 db lower,at this point but the graph's numbers come out to the RS meter's readings.
I feel that I am getting good measurements though, because as I move the sub around, change crossover, etc., the readings change in relation to what I did, and when I put it back to where it was the graphs are repeatable. Does it seem that I am indeed getting good measurements?
Here is my latest best sub response graph that I feel that I can get for now. After I looked at this I finally see what it is that I am trying to accomplish! (I think...) This is a Klipsch Synergy sub 10,with gain control set at 15 (scale of 0-40), crossover at 200HZ.

In regards to my question about bass being too boomy and room treatments, I did not word my question very well. I meant to ask: If tweaking settings won't improve the frequency response and I can't get rid of undesirable peaks or dips, is this where I need to look into treating the room? I have not mentioned the fact that the back of the listening position is on a wall. I have read how this can be problematic. Any way, any more suggestions or advice would be greatly appreciated, because I feel that I can make my little system sound even better. By the way, your system makes me feel like all I have is a boombox!
Thanks again,
Ron

[Wayne A. Pflughaupt]

If tweaking settings won't improve the frequency response and I can't get rid of undesirable peaks or dips, is this where I need to look into treating the room?

Your best bet is a parametric EQ like the BFD. It takes lots and lots of expensive bass traps to smooth response. Once you get them all in the room you might have to watch TV from the kitchen.

Regards,
Wayne

[RonS1958]

I do not have any preamp jacks, I am assuming that would be needed for the BFD?

[brucek]

I read in another post that that can actually be okay as long as you still get a good measurement. Is that correct?

Yes. You can often get a low level warning in the Measure routine, since the initial Check Levels routine uses different limits on its pink noise than the Measure routine. Just carry on and do the Measure without concern.

I do not have any preamp jacks, I am assuming that would be needed for the BFD?

A BFD is installed between the receivers sub-out jack and the sub.

brucek

[RonS1958]

Ohhhh. I did not realize that. I will probably have to get it then. Will have to put it on hold for a while. Recent purchases: Subwoofer, HD video camcorder(have not even messed with it much yet), Laptop(pawn shop deal!), usb soundcard. I may drive my wife and boy off the edge with all this stuff! I do remember seeing that the price looked like a very reasonable upgrade for my system.
So for now, I guess I have a better response from my system. I am pretty sure 200 crossover sounds best and graph tests I have run confirm it. Sub floor position is set now. I will use gain control on sub depending on source. Directv XM needs a boost in bass whereas my DVD/CD player needs less. Reverse on sub phase seems best also. Is there anything else I can tinker with? Is there anything else I can do to integrate the mains with the sub? Because now I can PROVE to myself that it is better. I do believe that a lot of times a change in a setting is not necessarily better, but all we really notice is the change and perceive it as better. By ear is not right if you don't hear something that is supposed to be there!
Thanks,
Ron

[brucek]

Reverse on sub phase seems best also. Is there anything else I can tinker with? Is there anything else I can do to integrate the mains with the sub?

Yes. Since you only have a 0/180 phase switch, you don't have full control over the subs timing. Use the receivers sub distance adjustment to act as a proxy for a fully variable phase switch and see if you can get a better integration around the crossover region between main and sub.

brucek

[RonS1958]

Bruce,
I don't follow all the way through on what I am supposed to try. I have the sub's distance at measured distance of 16 ft from ears to middle of unit. Are you saying to adjust the distance up/down and see if I get a better response? What would I need to see in the graph to determine if any fiddling improves the crossover region?
Thanks for being patient with this rookie,
Ron

[brucek]

I don't follow all the way through on what I am supposed to try. I have the sub's distance at measured distance of 16 ft

Use your distance setting for the sub just as you would use the phase control.

You're attempting to get the smoothest transition at the crossover when measuring the mains and sub together.

The 16 feet is the perfect world setting, not the sloppy acoustic world setting. The best setting could easily be several feet either way.

The easiest method is to use the RTA feature of REW to set it.

brucek

[RonS1958]

Have tried different distances for sub. I measured with mains on and used speaker signal. Tried 16 ft(actual distance) 12 ft, and 20 ft. I will attach 12 vs 16 graph. Don't know how to interpret, but I think the 12 ft setting sounds much better. Tighter, truer bass sounds with better punch, and bass guitar notes better. Does the graph bear me out? Don't know if I have even done this right.
Red bar is 16 ft.
Ron

[brucek]

Does the graph bear me out?

No, that's an RT60 graph. It doesn't apply to what we're discussing.

Let's start over.

When we play the sub and mains together, there is good chance that the area where they both produce the same frequencies (at the crossover of 80Hz) that there will be some cancellation or addition that will cause dips and peaks in the the response at that area.

To solve this problem we use the phase control of the sub. A 0/180 switch may solve the problem, but not usually, so in lieu of fully variable phase control, we use the distance control of the sub (in the receiver).

The manual method to carry out this setup would be to set the mathematical distance of the sub from the listening position, then try both positions of the 0/180 switch to get the smoothest response. We have to look at a response graph to do this, which means taking a measure after each change in the variable phase dial or distance setting.

We are looking for a smooth transition at the crossover area. See the diagram below of an overlay of a perfect sub response and a perfect mains response. Where they mix, the result will be the red line as shown to produce an overall perfect flat line.

The diagram below is if we lived in a perfect world. In the real world we do our best and attempt to get the smoothest transition over the area the graph below shows in red. This can take trial and error, by adjusting the distance a bit and then taking a measurement and see if it's any better or worse.




At this point it would be nice if we didn't have to take all those measures. It would be nice if the measurement was in real time and we could dynamically adjust the phase or distance or sub position and watch the graph move at the same time......

For that we use the Real Time Analyzer (RTA) of REW.

To use this, you first set up your levels and meter, etc., as if you were going to take a standard frequency response measure.
In fact, take a standard response measurement, then when we switch to using the RTA graph you will have an example that you can look at of how the response was originally before you change the phase or distance setting.

Once that's done, select the Spectrum tab in REW and then select the Signal Generator icon at the top of the REW page and pull down and turn on PINK PN noise. Be sure to hit play to start it. You will hear it now out your speakers. Sounds annoying.

Then set all the other variable settings on the Spectrum page I have indicated on the example below. (actually no-bars is an option you uncheck in the Settings page under the View tab). Be sure to also set the axis as show.

Then press the RED button to start the RTA.

Now you will see the static measure you initially took (see the gold line below), and you will also see a black line that is dynamic. Now any changes you make will reflect in real time in the black line. It makes things a lot easier.

The plot below was of my office sub alone without mains, and then without moving anything I turned on the RTA. You can see the static plot and the real time plot are the same. If I change anything the black line dynamically changes.

Get it?




brucek

[RonS1958]

It's a good thing REW isn't a bomb or I would have blown the house up!
I believe I got the RTA going properly. TOTALLY AWESOME! With these test signals the REW meter RSMeter were reading identical. Comparing phases, I believe reverse has been confirmed as better. I believe that by ear also now. Trying different things didn't seem to make much difference and most attempts only deepened the dip at about 160-180 HZ. However, it appears that setting the distance to 40 ft flattened the dip, albeit slight. But I swear it appears to have helped in the vocals range. It sounds as if my system is starting to sound more like a studio. (Not that I have ever been in one)
Is it likely that I am actually perceiving that or am I just falling into a psychoacoustical web?
I have been listening to some music. I will probably sit on this setting a while and see if it is indeed a keeper.
Here is the graph. I hope I got it right.


Also, do any retail stores carry the BFD or is it pretty much an online thing?
I really am getting a kick out of this.
Thanks,
Ron

[brucek]

I believe I got the RTA going properly.

Yep, good job. The RTA is also useful for other things, such as moving the mic around to see what the other seating positions are like, or moving speakers around, etc.

Trying different things didn't seem to make much difference and most attempts only deepened the dip at about 160-180 HZ

The phase would have almost no effect at that frequency (an octave above the crossover). Moving a main(s) around would affect the 160Hz area.

it appears that setting the distance to 40 ft flattened the dip, albeit slight.

That's excessive. I would think that the most you would move from the actual distance wouldn't go over 50%. As I said, it isn't a slam dunk that phase will fix the crossover area. Sometimes, it is what it is.....

do any retail stores carry the BFD or is it pretty much an online thing?

Music/guitar instrument stores have them - that's where I got both mine. They sell guitars, etc. The BFD and most Behringer stuff is used by bands and for inexpensive studios. Look in the Yellow Pages.

brucek

[RonS1958]

Hello again,
Been busy with work and boy's baseball. I went "nuts" and upgraded my center channel to the Klipsch C-2 and my mains to the Klipsch F3. Much improved sound from what I had.
I have only adjusted by ear so far, but I know that it really needs some REW.
I went to a music store and looked at the BFD. They had both, the 1124 and the Pro. I chickened out and came home to read some more about them. I think I have decided I would want the 1124 so I can I have different settings for CD, Satellite and movies. The more I read though, the more I have become intimidated by it.
However, as I have read this stuff on the BFD, I have doubts whether I have enough understanding of all that is required. I also have some questions about some things.
First of all, is the 1124's problem with the firmware version of 1.3 to 1.4 and eprom updates still relevant? I definitely don't want to deal with that.
Also, I have Vista and no experience with MIDI. I have looked into the vista/midi problem and I don't understand that at all. As I get into setting the BFD up, will this be of concern? I mean, it seems that the MIDI is much needed to simplify things. (even though I don't understand yet what it pertains to!).
Even if I can only figure out a little bit of this BFD setup, I am inclined to believe that it could improve my sound quite a bit. Would doing just a few basic things with BFD help the sound?
I hope all this doesn't sound too dingy, but I don't want to buy something if I won't be able to use enough of it or do it properly.
Ron S

[brucek]

First of all, is the 1124's problem with the firmware version of 1.3 to 1.4 and eprom updates still relevant?

Not too likely that any 1.3 versions still around, but maybe the store has old stock. Plug it in at the store and check it before buying.

I have looked into the vista/midi problem and I don't understand that at all

What vista/midi problem are you referring to?

it seems that the MIDI is much needed to simplify things. (even though I don't understand yet what it pertains to

The midi is used to load filter settings from REW into the BFD with a midi cable. You can also load them from the front panel of the BFD if you like.

Would doing just a few basic things with BFD help the sound?

There isn't really a basic and advanced use of a BFD. You measure with REW, enter the filters into the BFD, and that's it.

brucek

[Wayne A. Pflughaupt]

I went "nuts" and upgraded my center channel to the Klipsch C-2 and my mains to the Klipsch F3. Much improved sound from what I had. I have only adjusted by ear so far, but I know that it really needs some REW.

Would doing just a few basic things with BFD help the sound?

Hopefully you know that the BFD will only be used on the sub, not the mains?

Regards,
Wayne

[Andysu]

brucek wrote:

The reverse appears to smooth the dip at 85Hz, so I would leave it there.

Overall, the response is quite good, but you're measuring quite high. Take your measurements at 75dBSPL.

brucek

Also you could also achieve flatter response with that 85Hz dip with time alignment if each sub had Behreinger DCX2496.

[RonS1958]

Back again,
Yes, I do know it is for the sub only. I went for a sonic match throughout my speaker system. I emailed klipsch and he recommended either the F2 or F3 for what I have with my sub and satellites. But he said if I went with F3 that I should get the C2 center. I found a closeout price online on both models. I was going to get the F2 but ended up getting the F3 when the seller only had one F2 in stock. I was going to get the C2 from the same place but went to HH Gregg too see it first and they matched the price so I had it setup before the F3's. Much improved overall sound from what I had.
I have read more of the BFD guide and I believe that I will be able to do it but it will take me a long time. But I am searching for that "over the top" sound that I am convinced is there, waiting to be found!
I did find a music store with the BFD 1124 but all he had was the floor model for $99. It had a couple of scatches and all my HT gear is in perfect condition, so, well...... I will look at some other local music stores or order online. Also, would any local retail stores have the USB/MIDI cable?
In regards to MIDI/Vista question: I thought that getting the settings from REW to BFD involved some program in Vista. but I am now guessing that it goes from REW to BFD directly via the USB/MIDI cable and that I don't need anything else in that regard. Is that correct?
As for the DCX2496, is that in addition to the BFD? How does that hook up to the system?I have never seen or heard of it until now. I see it runs about $300. I had better just lay low on any more additions for now! But I might add that later if investments go well over the next year.
Thanks to all for your help,
Ron
Ron

[brucek]

I am now guessing that it goes from REW to BFD directly via the USB/MIDI cable and that I don't need anything else in that regard. Is that correct?

Yes, that correct. Have you read the REW HELP files.......

As for the DCX2496, is that in addition to the BFD? How does that hook up to the system?

The DCX2496 is a loudspeaker management system. I can't imagine why you would need one. A BFD is perfectly suitable to EQ a sub.

Also, would any local retail stores have the USB/MIDI cable?

I think most people just order it on-line. It's not needed to use REW and a BFD. It's only a convenience for automatically loading the filters as opposed to loading them from the BFD's front panel.

brucek