Comments on my first measurements?

**elee532** · **05-25-09, 08:38 PM**

Any thoughts on my first measurements. The first graph is sub only (custom built Rythmik set at 20Hz mid dampening), the second is sub+mains, and the third is a waterfall of the sub+mains. Any thoughts on how this looks?

One question that I have as an amateur... why is 10hz to 40Hz so much louder than 40Hz to 200Hz? Is this how it's supposed to be?

**Wayne A. Pflughaupt** · **05-25-09, 09:23 PM**

Quote:

why is 10hz to 40Hz so much louder than 40Hz to 200Hz? Is this how it's supposed to be?

Every sub/room is different.

Impressive extension, for sure. Any other location options that might minimize that 55 Hz null?

Regards,
Wayne

**elee532** · **05-26-09, 12:39 PM**

Thanks for the reply Wayne. I do have some other placement options. I'm mostly trying to confirm that I am using REW correctly.

Is it true that I can put the sub in the primary seating position and then take readings at various spots in the room to see what it would like like if I placed the sub in that location? If so, does it matter which direction I point the sub when I put it in the primary listening position (I have a front-firing sub).

Also, my primary use is for music listenting, with home theater a close second. As a result, I suspect I would prefer to focus more on that 30hz to 80hz region?

Oh, one other question for now... when I originally created my soundcard calibration file, I was connected to my pre-pro via the soundcard's analog outs. I have since switched to the soundcard's SPDIF output. Do I need to create a new soundcard calibration?

Thanks!

**brucek** · **05-26-09, 01:57 PM**

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I have since switched to the soundcard's SPDIF output. Do I need to create a new soundcard calibration?

How do you propose to do that?

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I suspect I would prefer to focus more on that 30hz to 80hz region?

Your bottom end is a bit heavy for music.

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Is it true that I can put the sub in the primary seating position and then take readings at various spots in the room

Yes, read this.

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does it matter which direction I point the sub when I put it in the primary listening position

Not really. Put it on the floor in front of the couch and point it at your system. Once you find a good spot with the RTA, move the sub there and fine tune the position.

brucek

**Wayne A. Pflughaupt** · **05-26-09, 07:06 PM**

elee,

brucek pretty much covered it. I'll just add:

Quote:

Also, my primary use is for music listenting, with home theater a close second. As a result, I suspect I would prefer to focus more on that 30hz to 80hz region?

Yup. Lots going on in that region with bass instruments, and your response there is pretty rough (as you can see).

Regards,
Wayne

**elee532** · **05-26-09, 09:08 PM**

brucek, Wayne,

Thank you for the replies!

To the soundcard calibration question... I guess I hadn't quite thought it through all the way. I guess I MUST use the analog outs on the soundcard to do the calibration.

Any thoughts besides placement as the reason for the lesser performance in the mid-bass region? I've done a fairly thorough job of treating room corners with superchunk bass traps.

Thanks!

**Wayne A. Pflughaupt** · **05-26-09, 09:17 PM**

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Any thoughts besides placement as the reason for the lesser performance in the mid-bass region?

Nope. You'll probably have to consult with the knowledgeable folks at our DIY Subwoofer Forum for that.

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I've done a fairly thorough job of treating room corners with superchunk bass traps.

Although traps can reduce the distance between the worst peaks and valleys, their main function is to reduce low frequency ringing. Your waterfall chart shows yours are doing that quite nicely.

Regards,
Wayne

**weverb** · **05-26-09, 10:20 PM**

Quote:

elee532 wrote:

Any thoughts besides placement as the reason for the lesser performance in the mid-bass region?

Quote:

elee532 wrote:

(custom built Rythmik set at 20Hz mid dampening)

What about playing with the phase and crossover point? Also, can you change or try different settings. Maybe this one is boosting the 20Hz region too much.

There is some eq reference here:

http://www.rythmikaudio.com/faq.html#eq

**Saoof1** · **05-29-09, 12:48 AM**

Make sure you have the crossover adjusted all the way up on the sub itself and adjusted accordingly on the receiver. Seeing your response on the low end try the 28hz mode as well.

**elee532** · **05-29-09, 09:02 AM**

Thanks for the suggestion. The readings above do have the crossover turned all the way up. I'm hoping to make some adjustments this weekend and will try the 28Hz setting.

**elee532** · **05-30-09, 04:30 PM**

Can someone confirm that I am using the RTA feature correctly to position my sub? Here's what I think...

Spectrum Tab
Mode: RTA 1/24 Octave
FFT Length: 65536
Averages: 2
Window: Rectangular
Y Axis: dB

Generator:
Pink Noise
Sub Cal
Set RMS Level to 75dB

Put sub in main listener location
Press play button on Generator
Press record button in Spectrum window
Move SPL meter around the room and look for flattest response

**JohnM** · **05-30-09, 04:34 PM**

Pretty close, but you will get much more stable readings in the low frequency end by using Pink PN (Periodic Noise) rather than Pink Noise, you can get good results with Pink PN even without any averaging. You can also use a shorter FFT length for faster updates of the RTA display, 32768 is a good compromise between update speed and frequency resolution.

**elee532** · **05-31-09, 08:36 PM**

I posted a quick reading of my sub+mains with the sub moved from the front to the back of the room. This looking like some improvement?

Thanks.

**elee532** · **06-07-09, 05:18 PM**

I finally found some time today to play around a bit more. I tried to get my seating as close as possible to 38% from the back wall.

The first graph below shows some readings in the locations that I have available... blue = back corner, brown = front left corner, green = front middle, and red = along side wall right next to seating (kind of like an end table). Unless I am misunderstanding, the side placement (red graph line) looks to be about the smoothest.

The next graph shows the sub gain turned down a bit and the sub tuned to 28Hz Low Dampening. This seemed about as flat as I could get. Any thoughts on how this looks? I can't seem to do anything about that drop between 90 and 100. Is this something that I should worry about?

Thanks!!

**weverb** · **06-07-09, 10:52 PM**

Quote:

elee532 wrote:

The next graph shows the sub gain turned down a bit and the sub tuned to 28Hz Low Dampening. This seemed about as flat as I could get. Any thoughts on how this looks? I can't seem to do anything about that drop between 90 and 100. Is this something that I should worry about?

Looking good. I would do a plot with the mains on and see if the dip goes away. Also, with the side placement, just make sure the bass is not localized when listening to anything. Other than that, that is a good looking graph.

**elee532** · **06-08-09, 08:18 PM**

Thanks for the feedback! Unfortunately, it seems you're one step ahead of me... the bass is definitely localized now. I haven't made any adjustments to phase/distance settings. Maybe this will help? If not, are there other options for dealing with localization?

Thanks!

**weverb** · **06-08-09, 08:41 PM**

Quote:

elee532 wrote:

Thanks for the feedback! Unfortunately, it seems you're one step ahead of me... the bass is definitely localized now. I haven't made any adjustments to phase/distance settings. Maybe this will help? If not, are there other options for dealing with localization?

Usually localization can some what be addressed by crossover points, but usually it is mostly based on location of the sub. What xo setting are you using? Looks like 80Hz. Try something lower like 60Hz. and see if you notice a difference. Can your mains go down to 60Hz.? It may be a good idea to do a graph of just your mains. Try them at different xo points and see what they can do. Since your Rythmik is doing a good job going so low and if your mains can handle it, you can try a xo as low as 40Hz. possibly.

Also try the "blue" location. You may still get "localization" of the bass when the sub is in the rear, but try it any way.

**elee532** · **06-08-09, 10:55 PM**

Thanks. I'll experiment different crossover frequencies and see what I come up with. Can you tell me... when getting a graph of my mains, do I test with both of them connected or just one of them?

Thanks.

**weverb** · **06-09-09, 08:24 AM**

Quote:

elee532 wrote:

Thanks. I'll experiment different crossover frequencies and see what I come up with. Can you tell me... when getting a graph of my mains, do I test with both of them connected or just one of them?

Thanks.

For what you are looking for, you can do both at the same time.

**elee532** · **06-13-09, 09:37 PM**

I took a few more readings today...

The first is a graph of my mains. The red line is with my pre-pro crossed over at 80Hz and the blue is crossed over at 60Hz. There doesn't appear to be a much difference. However, I am surprised at how all over the place this reading is. Is this normal? (BTW, these are Salk SongTowers)

The next one is my sub + mains with my pre-pro crossed over at 60Hz. Looks like the dip around 100Hz from my earlier readings is pretty much gone. However, still a major dip around 167Hz.

Any advice?

**weverb** · **06-13-09, 10:31 PM**

Looks pretty good, but if you still have the localization problem then you might be better off moving the sub. Did you try the rear corner (blue response in previous graph) again?

Also, I am surprised there was no difference between 60 and 80Hz. Maybe brucek can shed more light on this.

The dip at 167 Hz. can probably be fixed with room treatments.

**elee532** · **06-14-09, 12:38 PM**

Thanks weverb. After a brief listen, the localization seems less, but not gone, at 60Hz crossover. I have not tried the rear corner again, but I do plan to.

brucek, any light to shed?

Would I use a 2" or 4" absorption panel or some other type of treatment to address the dip at 167Hz? How would I go about determining the position for the treatment?

FYI, I do currently have many of the room corners treated with superchunk bass traps.

Thanks!

**brucek** · **06-14-09, 02:06 PM**

I think the sub + mains looks fairly good.

At 60Hz, I can't imagine localizing a sub.

To determine if the 167Hz mains dip is a result of cancellation between the two speakers or between one speaker and the room, try measuring each one separately. A small movement of one might make a lot of difference.

brucek

**weverb** · **06-14-09, 02:46 PM**

Quote:

elee532 wrote:

Would I use a 2" or 4" absorption panel or some other type of treatment to address the dip at 167Hz? How would I go about determining the position for the treatment?

Check out this other cool feature REW has. It is call Energy Time plots (ETC). brucek has some good info in this post:

http://www.hometheatershack.com/foru...tml#post170156

It should help show if all your reflection points have been addressed.

**elee532** · **06-18-09, 09:47 PM**

I took a few more readings. Any help understanding them would be most appreciated!

As suggested earlier, the first graph shows readings of each speaker. Red is the sub and mains together, green is the left front speaker, and gold is the right front speaker. Does this offer any insight into the dip around 169Hz?

The next graph shows my sub and mains with my pre-pro crossed over at 60Hz. The red line shows the crossover setting on my sub set at about one-o'clock (scale ranges from 40Hz to 160Hz). The gold line shows the crossover setting on the sub at about eleven-o'clock. The red line looks a bit flatter, but I wonder whether dialing up the crossover setting on the sub is contributing to my localization issue. I'm really confused by how the crossover setting on my sub works with the crossover setting of my pre-pro... and how do I go about finding the best setting for each??

The next graph shows my mains without the sub. Green is pre-pro set to large with no sub, black is 60Hz pre-pro crossover, and blue is 80Hz crossover. Not posting this one for any reason in particular, though it does seem an odd looking graph to me? ...actually, I just realized something, this contradicts my earlier posting showing no difference between 60Hz and 80Hz crossover setting. Guess I must have screwed up something the first time. Why do my mains dip like that between 30Hz and 80Hz?

Finally, I posted my first attempt at an ETC reading. To be honest, I have no idea how to read it.

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