Room Response- SPL- Manual

**tonybradley** · **05-12-09, 09:33 PM**

I just don't seem to have the time to learn REW right now, so I want to start with the manual method and download the SPL Calibration Spreadsheet on the download page of this forum, along with the Test Tones.

I have a few questions on this manual method.

1) My system is calibrated for 75dB (when master volume is set to 0). However, how do I know how loud to turn my master volume to begin doing the manual tests? Do I play a 1000Hz or a 4000Hz signal and adjust the Master until my SPL meter reads 75dB, then use this Master Volume level for the remainder of the Test Tones?

2) I assume the Spreadsheet in the download section automatically changes the calculations based on the corrections for the Radio Shack SPL meter? So, I put in the EXACT number that my SPL meter reads, and the spreadsheet will adjust accordingly? Or, do I need to do some sort of calculation before I enter it into the spreadsheet?

3) Where on the spreadsheet do I enter my SPL readings.....the Light Blue (RAW SPL) column or the Orange (RAW SPL BFD) column? I plan on purchasing a BFD at some point to EQ my sub based on the curve from this spreadsheet.

Thanks, and if I put this on the wrong thread, please let know.

**brucek** · **05-13-09, 08:02 AM**

Quote:

1) My system is calibrated for 75dB (when master volume is set to 0). However, how do I know how loud to turn my master volume to begin doing the manual tests? Do I play a 1000Hz or a 4000Hz signal and adjust the Master until my SPL meter reads 75dB, then use this Master Volume level for the remainder of the Test Tones?

Since your subwoofer may be producing peaks and dips, it is difficult to know what level to begin the test at. Trial and error is the best method. Take a few readings at various frequencies (below the crossover frequency) so that you can be confident that the overall plot will be around 75dB. It isn't important to be accurate about this, other than to pick a volume control position and leave it alone over the test.

Quote:

2) I assume the Spreadsheet in the download section automatically changes the calculations based on the corrections for the Radio Shack SPL meter? So, I put in the EXACT number that my SPL meter reads, and the spreadsheet will adjust accordingly? Or, do I need to do some sort of calculation before I enter it into the spreadsheet?

Yep, just put the reading from the meter into the spreadsheet. The calibration value for that frequency will be added and then plotted.

Quote:

3) Where on the spreadsheet do I enter my SPL readings.....the Light Blue (RAW SPL) column or the Orange (RAW SPL BFD) column? I plan on purchasing a BFD at some point to EQ my sub based on the curve from this spreadsheet.

The RAW SPL and RAW SPL BFD are there to allow someone to enter two sets of readings to compare a before and after graph when they are equalizing with a BFD. Both entry columns are the same.

brucek

**tonybradley** · **05-13-09, 11:18 AM**

Quote:

brucek wrote:

Since your subwoofer may be producing peaks and dips, it is difficult to know what level to begin the test at. Trial and error is the best method. Take a few readings at various readings so that you can be confident that the overall plot will be around 75dB. It isn't important to be accurate about this, other than to pick a volume control position and leave it alone over the test.

Yep, just put the reading from the meter into the spreadsheet. The calibration value for that frequency will be added and then plotted.

The RAW SPL and RAW SPL BFD are there to allow someone to enter two sets of readings to compare a before and after graph when they are equalizing with a BFD. Both entry columns are the same.

brucek

As always, thank you for the valuable information.

**tonybradley** · **05-22-09, 08:58 PM**

Here are my first attempts at the manual sub measurement method. I used the Spreadsheet and Frequency files located on the Download section and the newer analog SPL meter from Radio Shack.

One thing I noticed, is that once the lower frequencies were playing, I could not hear, nor really feel anything, but the SPL meter was reading in the 70 and 80s. Is this normal?

Here is my first measurement. I placed my SVS PB12-NSD in the front right corner with the speaker and port facing the listening position (as recommended by SVS). As a Standard, I played the 100Hz signal and adjusted the Master Volume on my Receiver until that signal was around 75dB and left the Master Volume alone for the remainder of the tests. As you can see, I have some bad dips between 56 and 89Hz. As mentioned above, when the test tones were in the 20s (Hz), I could not really hear nor feel anything, but the SPL measured quite high. Everything below 16Hz did not register.

I then decided to leave the sub in the same corner, but I turned it so that the Speaker and Port were facing the front wall. My friend stopped by while I was beginning this test, and he used to be into Car Audio and competitions. He said for the Car world, they used 63Hz as the standard. So, this time, I adjusted the Master Volume so that 63Hz read around 75dB. Again, same as above, the Low Frequencies were registering on the Meter, but I didn't hear nor really feel anything. This graph appears to me to be much better, but I still have a dip 63 and 89Hz. The dip isn't as large as the dip in the first graph. We tested some DVDs, and it sounded a lot better, but still not great. My sub is REALLY HITTING THE LOWS. During some of the Dark Knight scenes, the lows were amazing. I could feel the chair vibrating and I could just feel it. However, when I played scenes with any gun shots or explosions, it just LACKED A PUNCH. I am thinking that a Shotgun being shot (like in Bourne Identity when Bourne goes outside of his Lady friend's friend's house.) would possibly be in the frequency range where I have the Dip. The Lows are amazing and quite cool, but I really want that tight UMPH in the upper range of the LFE. Will one of the BFDs help me at all with this dip? My buddy said I should be able to EQ the 16Hz to 56Hz down quite a bit to get close to the dip between 63Hz and 89Hz. I'm new to this, so not sure if the BFD can boost the dip upwards, or if it will decrease the others. Any help would be appreciated.

**brucek** · **05-23-09, 08:48 AM**

Quote:

once the lower frequencies were playing, I could not hear, nor really feel anything, but the SPL meter was reading in the 70 and 80s. Is this normal?

Yes.

Quote:

He said for the Car world, they used 63Hz as the standard

This matters not. Any frequency you use to set the initial volume level is only to position the graph on the plot at approximately 75dBSPL. Obviously if you chose a frequency where there was a huge dip it wouldn't be good, so once you've gone through the routine once and can see what your plot looks like, you can choose an appropriate frequency. In your case 40hz would be good, and 80Hz would be bad..

Quote:

dip between 63Hz and 89Hz

Adjusting the phase control on the sub will help with the dips in this area. Play a tone at ~80Hz and adjust the subs phase control for the loudest measured level with your SPL meter and then redo your measurement and see if the dip looks better. (Once you start re-measuring several times you'll begin to realize how nice it would be to have REW to do the job).

Quote:

Will one of the BFDs help me at all with this dip? My buddy said I should be able to EQ the 16Hz to 56Hz down quite a bit to get close to the dip between 63Hz and 89Hz.

No, Equalizers should be used to reduce peaks and not boost dips. Boosting dips is generally a waste of headroom and won't correct the problem. You also have to be careful in massive cutting filters to bring the signal down to the level of the dips - you can end up without any signal.

Begin with positioning of sub, and also testing with the phase control to remove the dips. EQ is for finishing touches. It can take a lot of measuring to get it right. You really should consider switching to REW. The manual method lets you get an idea of where your system is at, but for multiple measuring (which is required to get the sub correct) is painful with the manual method.

brucek

**tonybradley** · **05-27-09, 03:23 PM**

Quote:

brucek wrote:

....
Adjusting the phase control on the sub will help with the dips in this area. Play a tone at ~80Hz and adjust the subs phase control for the loudest measured level with your SPL meter and then redo your measurement and see if the dip looks better. (Once you start re-measuring several times you'll begin to realize how nice it would be to have REW to do the job).
Begin with positioning of sub, and also testing with the phase control to remove the dips. EQ is for finishing touches. It can take a lot of measuring to get it right. You really should consider switching to REW. The manual method lets you get an idea of where your system is at, but for multiple measuring (which is required to get the sub correct) is painful with the manual method.

brucek

Thanks for the response, and sorry for my delay as I've been taking in what you wrote. One thing I wanted to ask. These measurements are "Sub Only". I have my Mains set to Small and Crossover at 80Hz. Since I'm not running a second sub or my Mains with my sub at 80Hz, would adjusting the Phase actually do anything? I was under the impression that the Phase was used when using multiple subs or the Mains and Sub when trying to smooth out the dips. If it will still help me with Sub alone, I'll definitely try it.

**brucek** · **05-27-09, 04:01 PM**

Quote:

These measurements are "Sub Only".

I assumed this graph was sub + mains. Generally, if you're measuring and graphing a sub only, you will see the standard rolloff of the crossover. I don't see that with your measurement. Why?

Quote:

Since I'm not running a second sub or my Mains with my sub at 80Hz, would adjusting the Phase actually do anything?

Nope, adjusting phase on a sub by itself is like clapping with one hand - no effect is seen.
If you're getting dips with a sub only, then it's an interaction (cancellation) with the room. Movement is the option available.

brucek

**tonybradley** · **05-27-09, 08:07 PM**

Quote:

brucek wrote:

I assumed this graph was sub + mains. Generally, if you're measuring and graphing a sub only, you will see the standard rolloff of the crossover. I don't see that with your measurement. Why?brucek

That may be because I didn't know what I was doing. Since I had the Crossover set to 80Hz, I tested up to 100Hz and that was it. So, there would have been a rolloff had I tested those frequencies, but I didn't touch the defaults on the spreadsheet after 100Hz. I've been on the bowflex strengthening my back to prepare myself for moving my sub to different locations in my room LOL

**robbo266317** · **05-27-09, 08:20 PM**

I started doing the graphs manually too.

After using REW just once I was sold - it takes about 30 seconds instead of 30 minutes.

**tonybradley** · **05-28-09, 07:23 AM**

Quote:

robbo266317 wrote:

I started doing the graphs manually too.

After using REW just once I was sold - it takes about 30 seconds instead of 30 minutes.

Ok....you sold me. I will try it this weekend. I've read over the help files several times, I just need to put it into action.

**robbo266317** · **05-28-09, 08:54 AM**

Rest assured Tony, you will not look back.
I built my current speakers about 20 years ago and designed the crossovers from the manufacturers data and have been happy with them.
However, if REW had been available back then the job would have been a lot easier.

**tonybradley** · **05-29-09, 02:13 PM**

Quote:

robbo266317 wrote:

Rest assured Tony, you will not look back.
I built my current speakers about 20 years ago and designed the crossovers from the manufacturers data and have been happy with them.
However, if REW had been available back then the job would have been a lot easier.

About 6 months ago, I purchased the RCA adapters for the PC to run REW, but never had time to sit down and try it out. So, I calibrated my sound card last night. I then went to get the adapters so I could sit down and begin learning REW today and tomorrow, and Murphey must have been here for a visit. I cannot find those adapters ANYWHERE!!!!. I've been all over my house three times and cannot find them. I actually had a couple days where I had time to do this, but now, I'll have to order new ones and hard to tell when I'll get this time again. So, for this weekend, looks like I'll be moving my sub in different spots and measuring the Manual method.

**brucek** · **05-29-09, 02:23 PM**

Quote:

I'll have to order new ones

Pick up a couple at Radio Shack....

brucek

**tonybradley** · **05-29-09, 02:48 PM**

Quote:

brucek wrote:

Pick up a couple at Radio Shack....

brucek

Have you seen their prices?????? I got two from Parts Express for half of what one costs at RS....LOL

**tonybradley** · **05-29-09, 09:28 PM**

For now, I'm still doing some manual tests until I go to RS and buy some adapters. I moved my Subwoofer to the Front Left Corner and ran the frequency tests. The Blue graph is the newest placement vs. the Pink Graph showing the last graph. Does the Blue Graph look better? My dip isn't as bad, but is this still not too good?

**brucek** · **05-29-09, 10:20 PM**

Quote:

Does the Blue Graph look better?

Yeah, I'd say it looked better (up to 80Hz).

Why does the measurement rise and then fall off a cliff at 100Hz?

brucek

**tonybradley** · **05-31-09, 11:13 AM**

Quote:

brucek wrote:

Yeah, I'd say it looked better (up to 80Hz).

Why does the measurement rise and then fall off a cliff at 100Hz?

brucek

My crossover is set to 80Hz, and I was only worried (at this time) about the Sub placement, so I only downloaded up to 100Hz. When I get time, I'll be looking at the higher frequencies as well to see how my room is responding to those as well.

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