# Now what? Please give comments



## angryht (Nov 23, 2006)

The attached files are my room layout and the center speaker REW plot. BFD or no BFD. The location of the sub is between the left speaker and the center speaker. That is what seemed to give me the best response. I put in a house curve of +5 at 30 Hz and 0 at 80 Hz. My crossover is at 100Hz and I am running bass management with an Outlaw Audio ICBM. Please give comments and be brutal.

Thanks - hope I did this right.


----------



## brucek (Apr 11, 2006)

> center speaker REW plot


Can you explain what you mean by this?

brucek


----------



## angryht (Nov 23, 2006)

brucek said:


> Can you explain what you mean by this?
> 
> brucek





angryht said:


> center speaker REW plot



The graph is the frequency response of the center speaker using Room Eq. Wizard. This includes the subwoofer and the center speaker.


----------



## Otto (May 18, 2006)

Hi Greg,

Well, we normally measure our sub response by itself -- turn off all other speakers either by cutting power to their amp, or by simply removing the speaker cables from the speakers (or at the amp). 

Also, the fact that you were able to measure the center response tells me that you were using some type of audio processing mode -- perhaps DPLII or "multi channel stereo" mode. Either way, disable any of those modes and just measure the sub in a stereo mode with crossovers engaged. REW is a mono signal that's meant to be handled in a simple fashion.

What sub are you using? You're getting a very solid response to 30 Hz, and then it drops like a rock. Is that expected or is the ICBM somehow imposing that? 

If you're asking whether or not you should get a BFD, I would answer that I could go either way on that. Your response looks very good in general, and most of us would be happy to have a natural response like that. On the other hand, I love the BFD, and would not be without it or its equivalent.

In general, you're on the right track. It looks like you have REW set up properly, and you're able to take measurements. Keep going!


----------



## angryht (Nov 23, 2006)

Thanks, Otto. I have a seperate preamp, an Outlaw Audio ICBM (I just use it for bass management because I have an older preamp/pro: http://www.outlawaudio.com/products/icbm.html, and a 5 channel amp. All of the channels from the preamp go into the ICBM then to the amplifier (and the sub) and out to the speakers. Here is the setup for the signal from the computer (output). I ran the output cable from the computer to the left channel of the inputs of the preamp. Then I ran the left output from the preamp to the channel that I am testing (input for the ICBM) For the graph I show in the first post, it is the center channel which includes the sub.

I have a Def Tech Super Cube II subwoofer. When I did the sub alone (as you suggest by just unplugging the speaker wires) I get a pretty big hump from about 30to 50 Hz (at least I think it's from about 30to 50 Hz - my files are on my home computer). I will go ahead and post that later today. When I connect the speaker it settles down like my graph that I have posted.

Is the drop from 30 Hz unusually steep?? When I tried adjusting the phase the dip from 50 to 60 Hz just got deeper.


----------



## brucek (Apr 11, 2006)

> Is the drop from 30 Hz unusually steep?? When I tried adjusting the phase the dip from 50 to 60 Hz just got deeper.


The phase will only affect areas that are shared by two speakers. So, the frequencies near a crossover, would enjoy the largest effect.

The quick drop below 30Hz is a bit sharper than a natural rolloff, so it's likely cause by the room.

brucek


----------



## angryht (Nov 23, 2006)

brucek said:


> The quick drop below 30Hz is a bit sharper than a natural rolloff, so it's likely cause by the room.
> 
> brucek


Maybe if I move the sub around I could get a better response below 30 Hz??


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

> Maybe if I move the sub around I could get a better response below 30 Hz??
> 
> The location of the sub is between the left speaker and the center speaker.


I certainly would! I tried dead-center-between-two-walls one time, and the response was abysmal. Maybe give it a try in a corner that doesn't have any nearby openings.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

Thanks for the suggestions, Wayne. I will try the corner placement to see if I get a better response from the low end. I also noticed that when I adjust the xover on my ICBM, I don't seem to get much change - I will have to explore that. 

I suppose it would be better to use just the signal to the sub only for placement then get it tuned in with the front speakers, right?

I will try to post more graphs when I get time.

Thanks again for your help.


----------



## angryht (Nov 23, 2006)

I did some more testing over the weekend. I moved the sub to a number of locations and still did not get much of a response from below 30 Hz. I also looked at the room modes. I got the following using the room mode calc located here: http://www.hometheatershack.com/forums/bfd-rew-forum/336-room-mode-calculator-converter.html 

I used dimensions of: 7 FT height, 8'10" width, and 12'8" length. I had to take some averages of the width and height.

Maybe I'm not reading this right, but if the room affects my response below 30 hz, wouldn't that mean there should be a mode around that frequency and that I would be in a null??

There is probably more going on in the room - tangential modes???

I will post more graphs later tonight with just the sub.


I was also curious about the sub itself (Def Tech Super Cube 2). Would the fact that it has one active woofer and 2 passive woofers cause some sort of cancelation? Does anybody else have any experience with the Def Tech subs and REW?


----------



## angryht (Nov 23, 2006)

*This seems a bit weird*

Forgive me for breaking the suggested graph limits but I had to show you guys this. Here is my sub only. I did not think I was getting any response below about 30 Hz. It looks like a huge dip. Is this normal below 20 hz???

Can this be fixed with a BFD?

Incidently, my crossover has two settings - 12 dB/Octave (normal) or 36 dB /Octave (special for THX subs). I have it set to normal or 12dB/octave.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

I dunno – typically a “real” null is pretty narrow. That thing’s more than 2-1/2 octaves wide.



> Can this be fixed with a BFD?


I have my doubts, unless you have something like 30 miles of headroom. If not, it’s impossibly deep - 30 dB!!! Aside from that, the lowest filter setting the BFD can be set at is 20 Hz. Sure, you could affect lower with a really wide filter, and then EQ down everything above 30 Hz, but as noted, you would have to have a sub system – both amp(s) and driver(s) - that’s totally loafing right now, using maybe only 5-10% of their capability.

I’m can’t help but think there’s something we’re missing. I can’t say I’ve ever seen anything quite like this. Not in a corner, anyway... Are there any gaping holes in the wall - bar pass-through, doorway, etc. – near the sub?

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

Wayne A. Pflughaupt said:


> I dunno – typically a “real” null is pretty narrow. That thing’s more than 2-1/2 octaves wide.
> 
> 
> I have my doubts, unless you have something like 30 miles of headroom. If not, it’s impossibly deep - 30 dB!!! Aside from that, the lowest filter setting the BFD can be set at is 20 Hz. Sure, you could affect lower with a really wide filter, and then EQ down everything above 30 Hz, but as noted, you would have to have a sub system – both amp(s) and driver(s) - that’s totally loafing right now, using maybe only 5-10% of their capability.
> ...


Well I do have a lot of headroom left. My sub is at about 15 to 20 percent of capacity. I bet I could easily boost it up to get the 15 Hz to 75 dB. But wouldn't that blow out every thing else?


----------



## angryht (Nov 23, 2006)

Wayne A. Pflughaupt said:


> I’m can’t help but think there’s something we’re missing. I can’t say I’ve ever seen anything quite like this. Not in a corner, anyway... Are there any gaping holes in the wall - bar pass-through, doorway, etc. – near the sub?
> 
> Regards,
> Wayne



No gaping holes. I do have a basement window that is in the room, but it is small (typical basement window). The window is closed, and I have linacoustic lining the walls. The position of the sub is fairly close to the corner - just the right side of the left speaker. When I move the sub around the room I get, in general, the same response.


----------



## angryht (Nov 23, 2006)

Wayne,

Here are 50 percent, 75 percent and 90 percent in that order:


----------



## brucek (Apr 11, 2006)

The information below 20hz is not actual output from the sub. As the response drops into the noise, the meter calibration file compensates (as it also drops) and applies its opposite compensation.

See in your graph where the cal file drops past 10Hz and carries lower (because C-Weight is incorrectly turned on). This offers increasing compensation, and as the actual signal enters the noise, the meter file creates the strange rising signal.

Your usable response goes a little below 20Hz.

Below I show a couple graphs of a small sub I own.

You can see from the impulse response where the signal enters the noise about ~45dB down.

Then see the associated frequency response plot (with the exaggerated vertical scale) that is created from that impulse response, and you can see where the signal is down about ~45dB, but then begins to rise. This isn't signal - it's noise. 

Generally you determine where your sub signal enters the noise and set your bottom horizontal axis to that...... For most people, that horizontal scale is about 15Hz.... The LLT guys use about 10Hz....

















brucek


----------



## angryht (Nov 23, 2006)

brucek said:


> The information below 20hz is not actual output from the sub. As the response drops into the noise, the meter calibration file compensates (as it also drops) and applies its opposite compensation.
> 
> See in your graph where the cal file drops past 10Hz and carries lower (because C-Weight is incorrectly turned on). This offers increasing compensation, and as the actual signal enters the noise, the meter file creates the strange rising signal.
> 
> ...


Thanks, Bruce. So based on that I should set my lower limit of frequency back to 15 and try to equalize that. You mentioned that C-weighting is incorrectly turned on - do you mean below 15 Hz? I assume I should have it on for measurements and that it is not relavant below the limit of my small sub.

Who are th LLT guys? I did not understand the reference. 

From my graphs of 50, 75 and 90 percent, would a BFD help to tame things with my sub?

Thanks again for the help.


----------



## brucek (Apr 11, 2006)

> So based on that I should set my lower limit of frequency back to 15 and try to equalize that


You should set the axis on your graphs to horizontal of 15Hz-200Hz and the vertical to 45dB-105dB. The third (blue) plot you show is quite good. The natural low end extension is a bit below 20hz. That's good. You can't equalize below 20Hz with a BFD. Either way, there's no upside to trying to boost below a subwoofers rolloff at the bottom end.



> You mentioned that C-weighting is incorrectly turned on


The C-weight check box in REW is only active _outside_ the limits of the meter calibration file. It should be turned off.



> Who are th LLT guys? I did not understand the reference


Many members here have built LLT's. See the DIY subwoofer and Soundsplinter sections in the forum..
LLT explained



> From my graphs of 50, 75 and 90 percent, would a BFD help to tame things with my sub?


You have a very good response. I wouldn't try and equalize it.

brucek


----------



## angryht (Nov 23, 2006)

brucek said:


> You should set the axis on your graphs to horizontal of 15Hz-200Hz and the vertical to 45dB-105dB. The third (blue) plot you show is quite good. The natural low end extension is a bit below 20hz. That's good. You can't equalize below 20Hz with a BFD. Either way, there's no upside to trying to boost below a subwoofers rolloff at the bottom end.


ok. I will reset the graph limits. That last graph (blue) is just a result of me turning up the gain on the sube to about 90 percent of the total. I did not _set_ the levels before I took the reading. I just did a quick _check levels_ before the test and it said ok. Maybe that's all I need to do?


brucek said:


> The C-weight check box in REW is only active _outside_ the limits of the meter calibration file. It should be turned off..


I don't understand. I am using the radio shack analog meter, aren't I supposed to have the C-weight box checked? Is it different for just measuring the sub? I think I am missing something. Could you please explain?


brucek said:


> Many members here have built LLT's. See the DIY subwoofer and Soundsplinter sections in the forum..
> LLT explained.


I will check this stuff out. Thanks for the clarification.




brucek said:


> You have a very good response. I wouldn't try and equalize it.
> 
> brucek


That's good news. I just need to get it dialed in with my mains.


----------



## angryht (Nov 23, 2006)

One more question. I am running everything through my ICBM for bass management. I did those readings (green red and blue graphs) with my crossover set to 60 Hz. It looks like it is not working correctly. Shouldn't I have a drop off just before 60 Hz? From the graphs, it looks like it's set at about 120 Hz.


----------



## brucek (Apr 11, 2006)

> I just did a quick check levels before the test and it said ok. Maybe that's all I need to do?


Yep, if it says OK, that's fine.



> I don't understand. I am using the radio shack analog meter, aren't I supposed to have the C-weight box checked? Is it different for just measuring the sub? I think I am missing something. Could you please explain?


The C-weight check box only affects the calibration outside the limits of the meter calibration file.

So, if I don't enter a meter calibration file and check the C-weight box, then REW will use all C-weight calibration values for the entire frequency band from 0Hz to 30Khz. Meters unfortunately don't track a C-weight curve exactly, so we need a calibration file instead.

If I enter a meter calibration file that starts at 10Hz and ends at 200Hz, and I have the C-weight box checked, then C-weight calibration values are used below 10hz and above 200Hz. But, it would be meaningless to use a meter outside the meter calibration files outer limits, (since it wouldn't be accurate), so there is no reason to check the C-weight box..



> Shouldn't I have a drop off just before 60 Hz?


It should theoretically track the target line set in REW. Be sure to set the desired target frequency and slope in REW that you want to use.

brucek


----------



## angryht (Nov 23, 2006)

> Yep, if it says OK, that's fine.
> 
> 
> The C-weight check box only affects the calibration outside the limits of the meter calibration file.
> ...


Now I think I get it. Since I am measuring from ~10 hz to 200 hz and I have loaded the calibration file for my SPL meter (from this site), REW is not using the C-weight because there is nothing being measured outside the limits .cal file. So, if I wanted to use the meter _above _200 hz, I should use the c-weight, right? Otherwise it isn't doing anything except under 10 hz which doesn't matter anyway.


----------



## brucek (Apr 11, 2006)

> REW is not using the C-weight because there is nothing being measured outside the limits .cal file. So, if I wanted to use the meter above 200 hz, I should use the c-weight, right? Otherwise it isn't doing anything except under 10 hz which doesn't matter anyway.


Yeah, if you wanted to measure above 200Hz, you would turn on the C-weight. The C-weight compensation at and around 200hz is about nil anyway in this case, but you've got the idea.....

brucek


----------



## angryht (Nov 23, 2006)

Well I did some more testing last night and all I have is questions. The 4 results (sub only) are below.
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? Or is the sound greater than the meter can read, hence the red Check Level values (maybe top end is being cut off and just being shown flat???). If I am trying to get a flat response, I should just turn up the sub but then I am exceeding the Settings Procedure? Then when I try to turn up the sub alone to blend with the mains it is overwelming to my ears but the response graph out flat around 90 dB?? Am I missing something in the Set up?


----------



## brucek (Apr 11, 2006)

> Am I missing something in the Set up?


You need to do the setup procedure in REW and then leave the volume levels alone. If you change them significantly as you have, then you should really redo the procedure. There's really no reason to modify the levels once REW is setup. Reasons to re-setup REW would be a change in BFD filters (which alters the overall level from the sub), or adding in the mains with the sub (which again alters the overall level). Turning up the levels can clip the meter or the input of the soundcard...

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


----------



## angryht (Nov 23, 2006)

> To go through these steps only takes a second......
> 
> 1. Ensure the soundcard and meter calibration files are loaded.
> 
> ...


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 (Apr 11, 2006)

> 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 (Nov 23, 2006)

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:



> *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 (Apr 13, 2006)

> 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. :laugh:

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 (Nov 23, 2006)

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 (May 18, 2006)

angryht said:


> 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:



> 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.
> ...


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 (Apr 11, 2006)

> 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.



> 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 (Nov 23, 2006)

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:


> 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:


> 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.



> 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 (Apr 11, 2006)

> 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 (Nov 23, 2006)

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 (Nov 23, 2006)

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


> 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.
> 
> ...


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 (Apr 11, 2006)

> 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 (Nov 23, 2006)

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


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


> 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 (Apr 11, 2006)

> 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.



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


yeah..

brucek


----------



## angryht (Nov 23, 2006)

Well in the immortal words of Homer Simpson...


----------



## angryht (Nov 23, 2006)

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 (Apr 11, 2006)

> 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 (Nov 23, 2006)

> 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 (Apr 11, 2006)

> 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 (Nov 23, 2006)

Thanks, I'll try that.


----------



## angryht (Nov 23, 2006)

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:


> 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 (Apr 13, 2006)

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 (Nov 23, 2006)

Hi Wayne. Thanks again for your input.



> 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??



> 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.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

angryht said:


> 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 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?


Sorry that peak slipped past me earlier. Yes, you obviously don’t want to adjust for a house curve based on a response peak. So - 70 Hz it is. However...



> 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.


The house curve needs to have the lower frequency perceptively louder than the higher one. Obviously that’s not going to happen in your case, since 30 Hz and 70 Hz are at the same level, and you have no way to adjust the former up (or the latter down, as the case may be).

In lieu of equalization, about all you can do for a house curve is adjust the overall sub level up or down in relation to the mains. Based on your graph, it shouldn’t sound too bad, but eliminating that 40 Hz peak via equalization would make an audible improvement.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

> In lieu of equalization, about all you can do for a house curve is adjust the overall sub level up or down in relation to the mains.


Well that was what I was wondering. I was thinking of just increasing the overall sub level to see what kind of house curve I can get. I am not sure how to do your method by ear. I've always thought that my ears are not very accurate in terms of sound level between two frequencies. Is there a way to measure it? It looks like it varies in terms of how many dB above the reference (70 or 80 hz), looking at other house curves.


> Based on your graph, it shouldn’t sound too bad, but eliminating that 40 Hz peak via equalization would make an audible improvement.


I am still trying to decide if the BFD is worth it. Do you think it would be based on my current response?


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

> I've always thought that my ears are not very accurate in terms of sound level between two frequencies. Is there a way to measure it?


Yup. Go to Sonnie’s BFD Guide (see sticky thread on this Forum’s index page) and download some sine wave test tones. Burn to a disc and play back on your system. You’ll be able to easily discern volume differences between the various tones, especially where you currently have peaks vs. where you don’t.



> I am still trying to decide if the BFD is worth it. Do you think it would be based on my current response?


Not sure I’m qualified to answer that, seeing as your curve isn’t all that bad. I’d say it depends on how picky you are about your sound. I am, but I’m also cheap.  So you might eBay one, like I did. Typically they sell for $50-65. Hard to go wrong at that price, and you can always flip it if you aren’t duly impressed.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

> Yup. Go to Sonnie’s BFD Guide (see sticky thread on this Forum’s index page) and download some sine wave test tones.


Can't I just use the signal generator in REW?


> but I’m also cheap


Me too.


> So you might eBay one, like I did.


I will definately take a look. Thanks again.


----------



## brucek (Apr 11, 2006)

> Can't I just use the signal generator in REW?


Of course.......... 

brucek


----------



## angryht (Nov 23, 2006)

Thanks.


----------



## angryht (Nov 23, 2006)

ok. Here are my results (trying for a house curve without an EQ). The first graph is the sub turned up so 30 hz and 70 hz matched (I think) by ear. The second graph is the sub as flat as I could get it and the third graph is a compromise between the two. I took a few other measurements between but I liked the way the third graph looked so I stuck with it. Does it look better than the flat response? I will do some listening and let you know.


----------



## angryht (Nov 23, 2006)

Well, I've watched (listened to) a few movies with the low end boosted (my last graph in the previous post). I am not sure I could tell the difference, most likely because the movies I've watched have been heavy on the dialog. I guess in my mind I am still struggling with the 'house curve concept'. I always thought the goal was to get as flat a response as possible. However, the idea that my ears don't 'listen' that way is quite interesting. Are there any other resources to go through to get a better handle on this?


----------



## angryht (Nov 23, 2006)

I went back and read the house curve sticky at the beginning of the this area. The x-curve explained here: http://www.hometheatershack.com/forums/1307-post3.html is -5 dB at 20 hz and 0 at 63 hz. Wouldn't the goal be to invert that with my response in my home theater? Shouldn't I just dial in a house curve of 0 dB at 63 hz and +5 dB at 20 hz, draw a straight line from point to point via the house curve funtion in REW and try to match that? Are movie theaters speakers responses set up to invert the x-curve so it 'sounds like' a flat response?


----------



## angryht (Nov 23, 2006)

Here is the sub turned down a little bit more to try to match the house curve of 0dB at 63hz and +5dB at 20 hz. I would think this would be better to match the x-curve????? I suppose the big problem is still the big hump at 40 hz.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

> I always thought the goal was to get as flat a response as possible. However, the idea that my ears don't 'listen' that way is quite interesting. Are there any other resources to go through to get a better handle on this?


Probably not. I’ve found that Googling “house curve” doesn’t get you much. Haven’t tried any other search engine, though.



> I went back and read the house curve sticky at the beginning of the this area. The x-curve explained here: http://www.hometheatershack.com/forums/1307-post3.html is -5 dB at 20 hz and 0 at 63 hz. Wouldn't the goal be to invert that with my response in my home theater? Shouldn't I just dial in a house curve of 0 dB at 63 hz and +5 dB at 20 hz, draw a straight line from point to point via the house curve funtion in REW and try to match that? Are movie theaters speakers responses set up to invert the x-curve so it 'sounds like' a flat response?


The X-curve discussion was merely to show that movie industry uses a “house curve” for production as well as playback – i.e., in theaters. You don’t want that curve for your home theater. Movie theaters use the x-curve – not an inverted version of it.



> Shouldn't I just dial in a house curve of 0 dB at 63 hz and +5 dB at 20 hz, draw a straight line from point to point via the house curve funtion in REW and try to match that? I would think this would be better to match the x-curve????? I suppose the big problem is still the big hump at 40 hz.


You can certainly try it, although many people prefer shelving at about 30 Hz, not a continuously-rising curve. See Part 1 of the house curve article.

This is all academic, until you get an equalizer. I lieu of that, I suggest setting your curve (which in your case means adjusting the sub up or down) with music as a starting point. That’s a good reference point, because it’s easy to tell when it sounds right because the bass blends with the rest of the signal. Get a good blend there, then try some action movies, not “dialog” fare. You may find you need to then turn it up the sub a little, but that should be about it.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

Thanks again, Wayne, for helping me wrap my mind around this stuff. 



Wayne A. Pflughaupt said:


> Movie theaters use the x-curve – not an inverted version of it.


I'm not sure I understand. If that's the case wouldn't you want to try to match the response of the movie theater which would be just the opposite of putting in a house curve.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

For one, a movie theater, even a small one, is many times larger than your room. Remember, different sized rooms require different curves.

That said, not sure how you arrived at the conclusion that the x-curve is the opposite of a house curve.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

Wayne A. Pflughaupt said:


> That said, not sure how you arrived at the conclusion that the x-curve is the opposite of a house curve.


I mean at the low end. The typical house curve is _*higher *_below the crossover point (~80 hz) and the x-curve cited in the house curve thread (shown below) *drops *below 63 hz.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

The movie industry has their own version of what a house curve should be, that suits their purposes. 

For instance, they may be reducing below 63 Hz to minimize low frequency bleed-through to adjoining theaters.

Again, the X-curve discussion was only meant to show that house curves are necessary both in production and playback. The X-curve itself is of no use in a home theater, unless one happens to prefer sagging lows and highs.

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

> The X-curve itself is of no use in a home theater, unless one happens to prefer sagging lows and highs.


I guess that is where I get a little confused. I figured since the movies are mixed to the x-curve, that trying to match would be a good idea. Then I thought that since a house curve is boosted in the low end that it was trying to compensate for that drop.

Still a little confused but I think I am getting it.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

> Then I thought that since a house curve is boosted in the low end that it was trying to compensate for that drop.


Nope – the house curve is merely a compensation for _your_ particular room – has nothing specifically to do with movies, actually, because you probably need one even if you only listen to music. 

Regards,
Wayne


----------



## angryht (Nov 23, 2006)

Thanks again, Wayne. 

So, does that mean if a person listened to a speaker (and the speaker measured flat) in an anechoic chamber, it would sound good? And the only reason for the house curve is to compensate for the room acoustics?


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

> So, does that mean if a person listened to a speaker (and the speaker measured flat) in an anechoic chamber, it would sound good?


Couldn’t say – I’ve never heard a speaker in an anechoic chamber. 



> And the only reason for the house curve is to compensate for the room acoustics?


 Well, now you’re getting into areas I really don’t know much about. Acoustics has more to do with a room’s reverberation, or lack thereof, and perhaps treating to minimize the same, if needed. A house curve seems to be related primarily to the size of room, and when you include the mids and highs, your physical distance from the speakers. As I noted in Part 2 of the house curve article, I’m more familiar with the “how” than the “why.” 

Regards,
Wayne


----------

