Now what? Please give comments

**angryht** · **08-08-07, 10:01 AM**

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To go through these steps only takes a second......

1. Ensure the soundcard and meter calibration files are loaded.

2. Run the Check Levels routine with the SPL meter at the listening position and the dial of the meter at 80dB position. This gives the meter lots of headroom from the 75dB target you'll be setting in REW.

3. Run the Calibrate SPL routine in the meter tab to match REW and the SPL meter to ~75dBSPL.

4. Run the Set Target Level routine, which will set the target to ~75dB.

5. Run the Measure routine and set the End Frequency to 200Hz.

6. Measure....................

brucek

That's what I thought. That means my sub response is the first graph in my previous post. See below. Based on that response it appears that I have a significant hump between 25 hz and 50 hz (about 8 to 10 dB). Also, a pretty good dip below 25 hz. Based on what I've read, I could get a BFD and bring down the hump. And from what you wrote a few posts back, I may be able to boost a little down to about 20 hz? Would it be worth a BFD?

**brucek** · **08-08-07, 10:12 AM**

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Would it be worth a BFD?

Yeah, I think so. That's a fair size peak that would easily come down with EQ.

brucek

**angryht** · **08-08-07, 12:46 PM**

Will the BFD allow me to increase the overall sub volume so I can get closer to the 20 hz at the low end and allow me to cut the output from about 25 hz to ~ 90 hz?

Based on this quote from the BFD guide it looks like I could:

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What is the BFD used for?

Originally the BFD was designed for the performance/entertainment industry. Think about its name “feedback destroyer”. It is used in recording studios and concerts. The unit is wired into the system, set on auto-pilot, and then it searches out feedback and kills it. However, its functionality and design allows it to be used in the home theater as one of the most flexible parametric subwoofer equalizers available... and the least expensive by far. With the BFD you can pick up to 24 frequencies (1 combined channel X 24 or 2 separate channels X 12), adjust the bandwidth as narrow or wide as you wish (from 1/60 of an octave to 120/60 or 2 full octaves), and either boost them as much as 16db or cut them by as much as a whopping 48db. How many parametric eq's do know of that can do that for 100 bucks or less? Pretty impressive if you ask me.

The BFD looks a little complex - but there sure seems to be a lot of info on how to use it on this site. I just need to read it!!

**Wayne A. Pflughaupt** · **08-08-07, 04:11 PM**

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Will the BFD allow me to increase the overall sub volume so I can get closer to the 20 hz at the low end and allow me to cut the output from about 25 hz to ~ 90 hz?

I realize I probably don’t have much credibility here after missing that whole weighting thing, but maybe I can redeem myself.

Hitting 20 Hz is not going to happen with this sub, because response is rolling out too fast below 30 Hz. I mean, it’s dropping well over 30 dB in less than 2/3 of an octave. If that rate were applied to a crossover filter, if could be classified virtually as a “brick wall!” Your plan to reduce output across the board will not work because by the time you EQ everything down to the level 20 Hz is, you will have reduced your overall signal by nearly 30 dB. There probably won't be enough signal left to drive the sub, even with it turned up all the way.

Even if there were, there's no free lunch. As far as the SuperCube is concerned, the result will be the same as if you has tried to apply a massive boost to get 20 Hz up - i.e., you'll be working it to death and run the risk of blowing the driver.

Def Tech’s 14 Hz extension rating for the SuperCube II I’m confident is fairly optimistic. I don’t think you’re going to find any $800 sub that will realistically get that low, especially one with an 8” driver. With a little boost from the BFD down there you might be able to squeeze 25 Hz out of it, since your sub appears to be fairly capable and you indicated you have plenty of headroom. But that’s about it. Even then, proceed with caution – if you start hearing rude noises from it afterwards, eliminate the below-30 Hz filtering.

Regards,
Wayne

**angryht** · **08-08-07, 11:53 PM**

Well here is the mains plus the sub. It looks pretty good to me, but the level is higher than the 75 dB target. I am wondering if that is because I split the signal from the computer to the left and right channels. Anyway take a look. It seems I got the smoothest response with a 90 degree phase setting and a crossover of 60 hz. Please comment I appreciate it. Still wondering about getting a BFD.

**Otto** · **08-09-07, 08:02 AM**

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angryht wrote:

Well here is the mains plus the sub. It looks pretty good to me, but the level is higher than the 75 dB target.

Would you say that this is at a very loud level if you were playing music through it?

I'm wondering if the sub flatness (especially around 25 Hz) is experiencing the effects you described in this post, which is partially quoted here:

Quote:

Graph 1: Set up using the Settings procedure
Graph 2: Increased master volume (pre/pro) about 9 dB from the first reading. Did a quick Check Levels prior to running measurement and got green -12.7dB
Graph 3: Increased master volume 10 dB from #2. Check Levels showed -9.7dB in red.
Graph 4: Increased master volume 10 dB from #3. Check levels showed -8.2dB in red.

It seems that if I simply increase the volume on the sub the response flattens out. Isn't that strange?

Here you describe a 20 dB increase at the preamp level that yields a 4.5 dB increase in measured SPL from the sub. You still appear to have 8.2 dB of headroom, so you're not clipping the input to the PC. Where was your SPL meter range set?

I wonder if your sub isn't compressing at the low end, thereby flattening out with the more signal you give it... That's what it looks like to me -- as you increase power, the signal gets flatter, but not louder. I'd be interested to see more plots, displayed on one set of axes, with increasing preamp levels, while the SPL meter is in an appropriate range.

**brucek** · **08-09-07, 08:51 AM**

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I am wondering if that is because I split the signal from the computer to the left and right channels

Splitting a line-level signal has no effect on its level.

Quote:

I wonder if your sub isn't compressing at the low end, thereby flattening out with the more signal you give it... That's what it looks like to me -- as you increase power, the signal gets flatter, but not louder. I'd be interested to see more plots, displayed on one set of axes, with increasing preamp levels, while the SPL meter is in an appropriate range.

I thought of that myself when he first displayed the graphs, but decided that it doesn't seem likely at this low level (~75dBSPL). Compression shouldn't occur until the sub is up to ~> 90dB.

But it certainly is worth a try.

Greg, if you're going to take a set of readings at 75dB, 80dB, 85dB, 90dB, 95dB etc, then before each test you would do a complete setup (as I described in detail earlier in the post), except set all the 75dB targets to a new value each test. Also be sure to increase the SPL selector wheel on the RS SPL meter when needed (i.e. for 75dB and 80dB use 80dB position, then move up to 90dB position etc...)

Post all the graphs on a single All Measured display for comparison...

brucek

**angryht** · **08-09-07, 12:29 PM**

Thanks again, you guys are fantastic. OK. I took a deep breath and went through your responses again.

I went through the setup process after your post but I didn't do this:

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2. Run the Check Levels routine with the SPL meter at the listening position and the dial of the meter at 80dB position. This gives the meter lots of headroom from the 75dB target you'll be setting in REW.

and I did not do this:

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4. Run the Set Target Level routine, which will set the target to ~75dB.

I'm no sure what the Set Target Level routine is but I assume it is the bottom of that menu as shown below.

On my previous post where I showed the increases in volume, I did not adjust the SPL meter (using the selector wheel), I just increased the volume.

On my last post, I did adjust the volume in the settings window using the speaker level pink noise, but I had not run through the Set Target Level routine and I had the selector wheel on the SPL meter set to 70. I did calibrate the SPL and it was consistent with the 75 dB I was getting on the meter but as you (brucek) has mentioned, I may have run out of headroom on the meter. I'll do more measuring tonight.

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Would you say that this is at a very loud level if you were playing music through it?

I watched the first half of movie Ray last night and it sounds pretty good to me.

I'll post more after the testing tonight. If I haven't mentioned it yet, man this software is cool!

**brucek** · **08-09-07, 12:46 PM**

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I'm not sure what the Set Target Level routine is but I assume it is the bottom of that menu as shown below.

Yeah, that's correct.

I think we'll ask John to change that to a 'button' in the next revision. A lot of people miss that.......

brucek

**angryht** · **08-09-07, 12:58 PM**

I saw it before.....I just did not know what it did. I guess I thought by setting target level to 75 dB (in the blue lettering) I would be done. Thanks again.

On a different subject, I've been reading about house curves - very interesting stuff.

**angryht** · **08-10-07, 10:52 AM**

So last night I started from scratch and went through these steps:

Quote:

1. Ensure the soundcard and meter calibration files are loaded.

2. Run the Check Levels routine with the SPL meter at the listening position and the dial of the meter at 80dB position. This gives the meter lots of headroom from the 75dB target you'll be setting in REW.

3. Run the Calibrate SPL routine in the meter tab to match REW and the SPL meter to ~75dBSPL.

4. Run the Set Target Level routine, which will set the target to ~75dB.

5. Run the Measure routine and set the End Frequency to 200Hz.

6. Measure....................

When I ran the Set Target Level routine for the first reading I got the first result below. I am pretty sure that that is my accurate response. The target value set was set to 75.0 dB in the routine. See my first graph below.

The weird thing is that I had noticed that when I set the target value, via the routine, I had not switched it to full range. So the routine was set using a tone that was supposed to be for the sub only. Then I redid everything for the full range speaker tone and it set the target to 70.2 dB. See second graph. Any thoughts about what is going on? It is pretty much the same response just the target is kind of screwy.

**brucek** · **08-10-07, 11:14 AM**

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The weird thing is that I had noticed that when I set the target value, via the routine, I had not switched it to full range.

Why would you set it to full range when you are testing a sub?

Only use subwoofer setting, even when you add the mains.

When you add the mains, simply go through the setup routine again, because the overall level will be different and so REW requires recalibration..

brucek

**angryht** · **08-10-07, 11:31 AM**

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Why would you set it to full range when you are testing a sub?

I was trying to blend the mains with the sub......

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Only use subwoofer setting, even when you add the mains.

.....I did not know that. Is that also true in the settings menu.....should I always use the sub tone? That's what my problem has been. So, I guess you would use the full range if you were looking all the way up to 20 kHz? And that info is probably not accurate or really relavant for a guy with only a Rat Shack SPL and no EQ. I think I'm catching on....maybe?

**brucek** · **08-10-07, 11:41 AM**

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should I always use the sub tone?

Absolutely. Adding the mains will affect the level received back from the sub pink noise test, so you do have to go through and run the setup , but everything remains the same as if you were just testing a sub alone to 200Hz.

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So, I guess you would use the full range if you were looking all the way up to 20 kHz?

yeah..

brucek

**angryht** · **08-10-07, 11:51 AM**

Well in the immortal words of Homer Simpson...

**angryht** · **08-10-07, 12:19 PM**

So, if that's the case, this is my response for the sub + mains. My crossover is at 80 hz and the sub is at about 15% of max output (turned down very low). If I get a BFD I should be able to bring down the peaks at 40 hz and 90 hz, right? Any other suggestions?

Thanks again, brucek, for your help in getting my mind right.

I have the ability to control the crossover for the center channel seperately, so I will post that graph later.

**brucek** · **08-10-07, 01:28 PM**

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If I get a BFD I should be able to bring down the peaks at 40 hz and 90 hz, right?

Well, you can eliminate the 40Hz completely with a BFD, but the 90Hz may not be as simple.

The 90Hz is more a function of your mains than the sub (which you're able to EQ). See the level of the target curve at 90Hz? That's the level (and the lesser influence) that the sub is offering to the mix at 90Hz. The mains contibute the most to 90Hz.

Often though, you can adjust the phase control of the sub (and somethimes the distance control of the receiver) and get the crossover area to flatten out.

Simply take repeated mesaurements while adjusting the phase and then the distance control of the sub and watch the 90Hz area and see if it doesn't respond.

Yes, you can also try and put a small negative filter at 90Hz and you may pull the hump down also...

Overall your response is quite good though.

brucek

**angryht** · **08-10-07, 01:57 PM**

Quote:

Often though, you can adjust the phase control of the sub (and somethimes the distance control of the receiver) and get the crossover area to flatten out.

Simply take repeated mesaurements while adjusting the phase and then the distance control of the sub and watch the 90Hz area and see if it doesn't respond.

I will try the phase adjustment (on the sub) but the pre/pro that I have is pretty old (Proton/Legacy luminance). It has a delay function, in milliseconds, for each channel, I am just not sure if it has delay for the sub. Delay is the same as a distance function, right? Also, since I am running bass management through my ICBM, I am not sure if that will work, but I will try it.

**brucek** · **08-10-07, 03:46 PM**

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I will try the phase adjustment (on the sub)

I only mentioned the delay adjustment in case you didn't have phase adjust on the sub...

brucek

**angryht** · **08-10-07, 05:24 PM**

Thanks, I'll try that.

**angryht** · **08-13-07, 01:22 PM**

That last curve is the best I can do. I tried some different phases and crossovers, but that seems to be the flattest I can get.

One more question. Has anybody just used the sub to get a house curve? I don't have a BFD (for now anyway) but I was wondering if I could use this method described by Wayne:

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After your sub’s response is reasonably smooth, play a couple of sine wave test tones, one at 100 Hz (or whatever your sub’s crossover frequency is), the other at about 32 Hz. (Naturally, you don’t want either of these to be in a null - shift your test tone up or down if you have to.) With measured flat response (or a less-than-optimal house curve), the 100 Hz tone will sound louder than the 32 Hz tone. If that’s what you find, your sub’s response needs to be adjusted so that both test tones sound like they’re the same volume level. Yes, that’s a highly subjective evaluation, but remember a house curve is perceived flat response – that is, it sounds flat, not measures flat. Thus it has to be subjective.

Based on my current response, I would target about 70 hz and 30 hz.

**Wayne A. Pflughaupt** · **08-13-07, 03:04 PM**

If 70 Hz is your crossover frequency, then yes 70 and 30 Hz is a good place to start. Typically people generate their house curve with the sub, since it’s the only thing receiving precise equalization. At that point, if the mid-to-upper bass sounds thin (or bloated) that would be from the mains, and addressed by placement and/or receiver tone controls.

Regards,
Wayne

**angryht** · **08-13-07, 03:36 PM**

Hi Wayne. Thanks again for your input.

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If 70 Hz is your crossover frequency, then yes 70 and 30 Hz is a good place to start.

Actually, my crossover is set at 80 hz. If you look at my last graph (shown below), it shows a hump between about 75 hz and 105 hz, with a peak at about 90 hz. I think that peak is a room mode, I have tried adjusting the phase and the crossover and I can't get rid of it. If you look at my first post, you'll see the length of my room is 12'-8". When I do the math I get 1130/(2x12.67) = 44.59 hz. The 2nd order is 2x44.59 = 89.2 hz. I am thinking that's what's showing up in my graph.
I thought that since my response is flat (and on target) at 70 hz, that was where I should shoot for. Would it be better to shoot for 80hz since it is the crossover??

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Typically people generate their house curve with the sub, since it’s the only thing receiving precise equalization.

But I don't have an EQ. I was just wondering, based on my last graph of the mains + sub, if turning up the sub to match the two sine waves (at 70 hz or 80 hz and 30 hz) would give me a good result.

Thanks.

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