My second attempt at measurements

**thewire** · **03-25-08, 05:38 AM**

Here are a couple more using the method of placing the subwoofer on the center seat and moving the mic.

Mic sitting behind my equipment rack (blue) in the back center of the room and the mic sitting on the floor of the front center of the room (purple).

behind equipment rack and bellow screen.jpg

Mic sitting on the right wall after adjustments (green) and mic sitting between the right tower and center channel (black).

right wall front and between right and center.jpg

**Wayne A. Pflughaupt** · **03-25-08, 09:03 AM**

Looks like either of the front locations will be the ticket. Get the crossover happening and a little EQ and you’ll be in business.

Regards,
Wayne

**thewire** · **03-25-08, 09:51 AM**

Thank you again Wayne. This has been a great learning experience. THX Tech Level 1 training is only a couple months away now but I feel like it has already began.

I will order the BFD then now.

What happens to a waterfall like this when a larger subwoofer is introduced? Do you you know where I could find a nice example?

waterfall.jpg

**Wayne A. Pflughaupt** · **03-25-08, 10:20 AM**

Quote:

thewire wrote:

What happens to a waterfall like this when a larger subwoofer is introduced?

It will show an increase in signal level, and ringing, below 30 Hz. The signal level will be due to the bigger sub’s better extension; the ringing will be due to the fact that it’s next to impossible to treat ringing that low.

Regards,
Wayne

**thewire** · **03-28-08, 01:44 PM**

When I use the set target level button, REW sets it to a 83.3 target and then suggest a 0.250 BW versus with the 75 target at 0.143 BW. It sets both filters at the same peak at 49.66 and suggest the same level of -8.8 gain for each. I did this without adjusting the input volume of the mic this time which seemed to have been incorrectly having to think I was getting further extension with the higher target. This was the difference between setting the level on the back of the subwoofer, versus the THX switch setting.

When I assign the filters later after measuring through the BFD, do I use the 75 target or the suggested 83.3. Should I raise the volume to 85 if it still suggest the 83.3? The help area says that the target is important for setting the correct gains and width, and I keep getting all kinds of error messages with the 75.

Also..I am supposed to set the input level of the mic using the 75 target and let REW determine the appropriate target by that setting? My input volume is rather low with the 83.3 target but I presume this is to prevent my mic from clipping?

**JohnM** · **03-28-08, 03:25 PM**

The target level figure that REW determines is its best estimate of the level that the response would show if the peaks and dips of the room were not present. It has no bearing on the mic level, you only need to set the mic level once when you do the input level calibration and not adjust it afterwards. The input level setting allows some headroom during measurements to provide for the effects of room resonances and avoid clipping, as you presumed.

After you have allowed REW to set the target level leave it there when finding peaks, assigning filters and optimising peak gain and Q.

**thewire** · **03-28-08, 04:38 PM**

Thanks John. That makes perfect since to me now. The BFD just arrived and so did the accessories also.

**thewire** · **03-30-08, 05:31 PM**

I gave it a try with the filters with the measurements then did some listening. It didn't sound right to me the way I was doing it. I went and took meaurements using a macro while I was holding the mic in front of me. I then took filters and applied those to that result. I did all this after setting up the inputs, and then changing it to the 85 target. I uploaded my filters boosting slightly around the 55Hz area, and making a few adjustments here or there with the peaks. This is a look at measured and predicted response.

filters.jpg

Measured

measured.jpg

**JohnM** · **03-31-08, 06:19 AM**

As you are measuring without a crossover your target should be flat rather than a sub crossover curve (change the shape in the Target Settings). That would reduce some of the cuts.

**thewire** · **03-31-08, 12:21 PM**

I will give it another try. Should I try and add the boost again? It looks close to where REW wants to remove a peak.

crossover adjust.jpg

Should I be doing this in the 83.3 target? Is my crossover wrong? My room is causing problems?

This is the mains again with a 75dB target, subwoofer with the 85dB target.

mains and subwoofer.jpg

mains waterfall.jpg

**thewire** · **03-31-08, 02:03 PM**

I will do more searching of how to setup my subwoofer after equalizing with the BFD.

**JohnM** · **03-31-08, 05:56 PM**

Sub still looks high compared to the mains

**thewire** · **04-01-08, 05:35 PM**

Maybe I could fix that problem with the 4ohm mains from Crystal Audio.

center channel.jpg

left and right.jpg

2008-03-27_083434.jpg

For entertainment value... these were my calculations for the room modes and my..

.. Hellmholtz Resonator (or whatever it may be) done without any Exel or person with Exel to do the calculations.

It is that large peak that can be seen on the waterfall above. I think that REW is quite cabable of seeing a resonance in a room. It isn't completely filled with insualtion yet... Thought it might be interesting to note that here since I saw a thread about finding a room resonance. I would not know the difference however if I had not done the calculations etc, but REW does see it.

Edit: Not sure about the damping factor. My amp specs say 200 at 8ohm. EIA dynamic power is 270W at 4ohm.

**JohnM** · **04-01-08, 05:50 PM**

Quote:

thewire wrote:

Maybe I could fix that problem with the 4ohm mains from Crystal Audio.

Why wouldn't you just fix it by turning the volume down on the sub a little?

**thewire** · **04-01-08, 06:58 PM**

I tried setting everything in DVE on the limited bandwidth pink noise to 65dB in effect turning down the sub from 71dB reference to the 65dB area, close to where the THX setting is at 64dB, whatever that might be indicating. The problem I have is that turning up the subwoofer makes all kinds of new sounds that would otherwise not be obvious, and makes those with the mains that are obvious less obtrusive, more clean. I choose not to turn up the volume last night becauase with the movie I was watching "the island" it was just to loud! Turning up the volume on the subwoofer isn't going to hurt anything that I am aware of. In fact, before my AVR quite working, it wanted me to turn up the volume on the back to around 85% before the auto-setup would even give me the time of day. Isn't that some kind of indication that maybe the room needs the subwoofer turned up? The max SPL I got playing around the other night with the subwoofer turned up was 99dB. I didn't watch the movie like that but I did some quick testing with a movie.

Are you suggesting that I should not get new speakers for the theater, another kind perhaps, or just turn down the subwoofer volume?

**thewire** · **04-01-08, 07:28 PM**

I'm sorry I'm kind of getting confussed about the setting of the target. Yes I turn down the subwoofer.

**thewire** · **04-01-08, 07:44 PM**

I did also look at the Polk line of surrounds and other center channels. I even asked about adding some to my current speakers for a set of 3 HT systems in a thread.

I asked about crossovers, matching the speakers I have with new ones etc. Nobody has ever offered me any advise for speakers before, with the exception of subwoofers. I might call Polk and see what the would recommend. It has been on my list of things to do actually.

**thewire** · **04-02-08, 09:41 PM**

I bridged my front left and right speakers with my other mono amps. That is 360W on a 250W speaker but I have done this before without problems. I used the same matching cables and wire to do so as I use for the other channels with the exception that I am running a longer one for the center channel. The speakers are still set to small. I aimed my left and right forward as Polk recommends and I tilted the center channel upwards more. I moved my rear speakers to the corners so that the bass traps are behind them.

Regarding the power on the left and right speakers, is it safe to take measurements in REW with them like this? Is there any risk?

**thewire** · **04-13-08, 10:19 PM**

The new pre/pro I think I will be getting has a left and right subwoofer output. The manufactor of the subwoofer recommends I place it beside the couch. I mentioned before that I had the smoothest response there. Here are some meaurements I have with the subwoofer on the right side of the room and the left. The driver is facing the rear wall. I would be interested in doing this because I could place my other two tower speakers on the subwoofers and they would be near the same height as the ones in the rear. I don't have much use for the other two tower speakers because my television doesn't sound very good with the other amplifier and music does not sound that great in the other room. Tell me what you think about adding a second subwoofer like this.

Right side filter

Left side same filter

right side waterfall

left side waterfall

measured and predicted right side

P.S. I have a better paying job now than last summer.

Advertisement