First Butchered Graph

[dem1an]

Here is my first really butchered freq graph. For some reason my measurements are way down below -160. I've tried to follow all the calibration steps and I made sure that rew was calilbrated to the SPL meter. I'm using an analog shack spl meter and SB Live USB.

I also noticed that I get hum through my speakers if I have my laptop plugged in. The odd thing is that my receiver is not on the same circuit as the plug for my laptop. What's up with that? FYI, I just unplugged my laptop for these tests.

[brucek]

I also noticed that I get hum through my speakers if I have my laptop plugged in. The odd thing is that my receiver is not on the same circuit as the plug for my laptop. What's up with that? FYI, I just unplugged my laptop for these tests.

That's fairly common with the cheap power supplies used for laptops. Most people use the batteries when running REW. If you need to use the power supply, it's best to plug it into the same oiutlet as the system uses.

I made sure that rew was calilbrated to the SPL meter

I suspect that isn't the case. You have an enormous offset. If the real SPL meter reads 75dB and you run the REW SPL meter routine and set it to 75dB and then run the Set target routine and it returns ~75dB, then the results will be at 75dB and not -200dB.

Do a sweep to 200Hz and set your vertical axis to 45dB to 105dB and your horizontal from 15Hz to 200Hz.....

brucek

[dem1an]

Well, I started over today with a clear head and got new results. Imagine that. I think I'm getting closer, but I'm seeing some nasty room effects. =)

[brucek]

Please use the standard vertical axis that is the standard used here at HTS for ease of comparisons.. Vertical = 45dB-105dB.

When plotting larger than a subwoofer standard of horizontal = 15hz-200Hz, turn on smoothing. Smoothing is used for full range measurements, where reflections can cause comb filtering that makes it difficult to see the underlying trend of the response. It is rarely used for low frequency measurements as it would obscure the true shape of the response and so not allow accurate correction filters to be determined.

brucek

[dem1an]

Thanks Brucek. That's excatly the feedback I ws looking for. Here is an improved graph. I ordered my treatments today. Does this graph look like a real room?

[Ayreonaut]

Yes, it looks like a real room, but you still need to set the upper frequency of the graph to 200 Hz.

[brucek]

Does this graph look like a real room?

Yep, a room that probably could use some treatment for the area above 80Hz and definitely a parametric equalizer is needed for the subwoofer. (As naut points out, when you show the subwoofer put an upper axis of 200Hz - but the 20K is fine for full room, or maybe cut full room off at 10K which will resolve the full range graph a bit better to show how effective your treatments are).

Can we see a plot of 15Hz -200Hz to get a better look at your sub and crossover (where we see a huge correctable peak)?

brucek

[dem1an]

brucek wrote:

Yep, a room that probably could use some treatment for the area above 80Hz and definitely a parametric equalizer is needed for the subwoofer. (As naut points out, when you show the subwoofer put an upper axis of 200Hz - but the 20K is fine for full room, or maybe cut full room off at 10K which will resolve the full range graph a bit better to show how effective your treatments are).

Can we see a plot of 15Hz -200Hz to get a better look at your sub and crossover (where we see a huge correctable peak)?

brucek

Thanks again. I'm really just going for a baseline here and make sure I have my technique right. I only have a small 8" sub and I'm getting the new receiver, new PB13-Ultra and new GIK treatments. I'd like to post each step of the way and see how everything is being affected.

[brucek]

I'm getting the new receiver, new PB13-Ultra and new GIK treatments

When will you be getting an FBQ2496 parametric equalizer to flatten that very bumpy subwoofer response? It's a must.

brucek

[Wayne A. Pflughaupt]

I'm really just going for a baseline here and make sure I have my technique right.

For the subwoofer graphs, turn off the smoothing, or use no greater than 1/12-octave.

Looks like pretty decent extension for an 8-inch sub. What is it?

Regards,
Wayne

[dem1an]

brucek wrote:

When will you be getting an FBQ2496 parametric equalizer to flatten that very bumpy subwoofer response? It's a must.

brucek

I was told to take it one step at a time and see how it goes. I suppose it is 100% guaranteed I need the FBQ, even after treatments and more careful sub placement?

Wayne A. Pflughaupt wrote:

For the subwoofer graphs, turn off the smoothing, or use no greater than 1/12-octave.

Looks like pretty decent extension for an 8-inch sub. What is it?

Regards,
Wayne

It's just a little JBL sub I've had for quite a few years. I can get the model if you're interested when I get back home. I did forget to turn back off the smoothing. Sorry.

[brucek]

I suppose it is 100% guaranteed I need the FBQ, even after treatments and more careful sub placement?

I's say so - yes... You could try moving it around, but with the look of the plot, I would think you'll require equalization.

I did forget to turn back off the smoothing. Sorry.

You've also switched to Linear plot rather than the proper Logarithmic plot....

brucek

[dem1an]

brucek wrote:

I's say so - yes... You could try moving it around, but with the look of the plot, I would think you'll require equalization.


You've also switched to Linear plot rather than the proper Logarithmic plot....

brucek

I figured I'd probably need something. Everyone has said my room will likely be problematic. What about Audessy? My new reciever will have this feature. Can they work together or are BFD and Audessy mutually exclusive? Does it do the same thing as a BFD -- just automatically and is just not quite as reliable? I also understand the U13 comes with PEQ. It seems like there may be a lot of opportunity for these things to overlap.

What's the skinny on the DSP1124P vs. FBQ2496? I like your idea about the presets. Was wondering if presets could be controlled with a remote. I'm guessing not, since I couldn't find anything about one. Also, Midi cable is not required or particularly useful?

Is there any reason to use Audessy once I decide to EQ with a BFD?

Hopefully, this post will be the last one for a baseline. Thanks for your patience with me.

[brucek]

What about Audessy? My new reciever will have this feature. Can they work together or are BFD and Audessy mutually exclusive? Does it do the same thing as a BFD -- just automatically and is just not quite as reliable?

We've had people who report success with the room eq systems built into receivers, but they also required the BFD to clean up the bottom end. The receiver systems work more on the full range I believe. The method of use is to first run the receivers eq system and then apply REW and the BFD to that. Just don't push the receiver eq button once the BFD is setup and enabled, or you'll have to start over.

What's the skinny on the DSP1124P vs. FBQ2496?

Both good. The 1124 has more program slots (the FBQ has only one), but the FBQ's specs are slightly better. No remotes........

brucek

[dem1an]

I added room treatments to my room and here are the new graphs. I did move the sub and tried it more towards a corner. I also have 1 more treatment to hang on the back wall. I ran out of wire. The room certainly sounds less echoey, but I don't think I'm seeing it reflected in the new measurements. You can see the treatments at the end of the thread (page 2).
http://www.avsforum.com/avs-vb/showthread.php?t=866660

Top is the pre-treament and the bottom is the post-treatment.

[dem1an]

Full rang picture...Top pre and bottom post....I don't know. I'm not sure I see any real difference. I see some changes in the sub, but that is due to me trying the sub closer to a corner. Do you think there is something wrong with my procedure or do you think treatments had a small impact? Thoughts?

[brucek]

I'm not sure I see any real difference. ........................Thoughts?

I sure do. You generally don't look at response graphs after you treat a room. You look at waterfall to see the change in decay. They extend out to about 800Hz. Look for less ringing out at various frequencies.
Also, when you want to compare anything, use the ALL MEASURED tab and you can overlay any measurements you've taken. Makes comparisons a lot easier that switching between two graphs.

brucek

[Wayne A. Pflughaupt]

dem1an wrote:

The room certainly sounds less echoey, but I don't think I'm seeing it reflected in the new measurements.
I see some changes in the sub, but that is due to me trying the sub closer to a corner. Thoughts?

I guess you know that panels aren’t going to do anything for your sub, right?

As far as being able to tell from measurements, if the treatments are going any good, there may be a way. Try comparing unsmoothed response before and after.

For instance, here is an unsmoothed full-range graph from a somewhat live room, and you can see there’s lots of “comb filtering” present above 1 kHz.

full range graph.jpg

The person who took the measurements told me he wasn’t seeing any of that in his room, which is well treated, using the very same speakers.

So – if you say the room is less echoey now, you might be able to see a before vs. after difference using no smoothing.

Regards,
Wayne