My BFD subwoofer EQ thread

**ThomasW** · 09 March 2006, 15:51 Thursday

To start off I'd forget about the midi connection. Use a standard analog output to the pre-pro until you get all the measurement stuff operational. Adding midi into the mix at this time brings an addtional set of problems we don't want to deal with....yet.

Here's a little tip, download and install the freeware version of TrueRTA. Now it's 1 octave measurement function is worthless. But the program itself is easier to get up and running compared to REQW. Once you have TrueRTA fully operational, you can migrate over to basics in REQW, then onto midi dumps....

Now on to REQW........

REQW should have tabs for you to change the input/output. It auto detects the soundcard. The input should be a wav setting.

I don't have a Creative card so I'll wing it. You need to get at the options that allow you to change/manage all the mixer functions. In generic XP you can use the Windows mixer to access these functions. You want to enable the wav function in the mixer.

When doing loudspeaker measurements there are Windowing parameters. Nothing to do with the OS (or the cosmos..:wink: ), this is referring to a window in-time, usually a few msec, when the test tone is sent to the speakers. There are many different kinds of measurement 'windows', most are named after the guy that invented them. Hanning, Blackman, Harris are all kinds of audio measurement windows. This isn't really anything you need to get involved in to run REQW.

1. In the same stack window for "Set Measurement Level", the button is pre-selected for "Sub Cal", which drives the low cut Hz to 30 and the high cut Hz to 80

Yes just use the custom setting. You can uncheck the high and low cut filters and set the bandwidth you want swept.

**Chris D** · 09 March 2006, 23:25 Thursday

Thanks, Thomas. I like your new "location" description in your bio, BTW. The.. uh... "school" I went to used to say that we were "5,258' above sea level...".

I triple checked the physical wire connections for the RS SPL meter to my Audigy soundcard, and everything seems okay. I tried various settings with the Soundblaster control panel, Windows settings, and sound volume panels, finding that my original setting seemed to be most accurate -- on the REQ Wizard, choosing the "Audigy 2 ZS" as the soundcard and "Line In" as the input, on the Soundblaster control panel and volume settings choosing "Line In" as the input and "Wave" as the source, all other inputs and sources muted. (note that the REQ Wizard automatically drives the volume for Wave and Line In to full)

I tried other variations, like choosing Wave for the input, but this (a) still didn't make the "set input volume" work on the REQ Wizard, and (b) didn't seem accurate. If you choose Wave, doesn't that mean that the Wizard is inputting the same Wave signal that it is outputting to the pre/pro, not inputting the actual SPL meter reading?

Some other info:

- If I select 80db on my RS SPL meter, when I play the REQ wizard generation tone, the box on the center left of the screen averages readings of -18db for "Peak" and -28db for "RMS". Both values jump around with variations of +/-3 db or so. If I turn down the SPL meter to the 70db setting and play the generation tone, the same screen averages about -10db for "Peak" and -18db for "RMS."

So, further questions:

- If I leave the SPL meter at 80db, are those readings good enough to continue? (I realize that the instructions suggest at least -24db RMS)

- With the readings that I'm getting with the SPL meter at 70db, why is the Room EQ Wizard not accepting the "set input volume"?

- So what exactly does this "RMS" reading mean, anyway?

On a slightly different topic, I also used some .wav file frequency test tones to test out if I should use a house curve. From what I understand, the way to generate a house curve is to play frequency test tones from about 20 to 80 Hz and see what volume setting at each frequency makes the tone SUBJECTIVELY SOUND EQUAL in volume to your ear.

Maybe it's just me, but if anything it seemed that my lower frequencies were actually equal or even slightly LOUDER at the same volume setting in comparison to the upper bass frequencies. If I built a house curve on this, wouldn't it be OPPOSITE of a typical bass house curve people use? i.e. the bass house curves I've seen are usually higher in the lower frequencies to compensate and then slightly taper off toward the upper frequencies. This seems to me that I don't want to use a house curve, then, and should just try to calibrate the subwoofer flat.

Question:

- Is this accurate? Or am I jumping the gun and should check for a house curve need AFTER the sub has been calibrated as flat as I can get it?

**ThomasW** · 10 March 2006, 00:50 Friday

Use whatever settings are effective getting a signal to the soundcard. Mine works with the wav mixer settings.

I can get REQW set up and running using just a empty soundcard in the PC. This means no mic plugged in, no output signal. This means it's using the ambient noise generated by the operation of the soundcard. That's why I suggested you troubleshoot your setup using TrueRTA to debug.....

I've never owned a RS SPL meter, but I doubt that meter's level setting has any effect on the output signal level going to the soundcard. In the mode you're using it, the output is like a microphone pre-amp, so it's level is controlled by the mixer. This means that using the dial to change the metering level on the meter has no impact on the output going to the soundcard.

RMS = Root Mean Squared, a measurement of output.

Calibration is setting the relative output levels of the various multi-channel speakers. It has nothing to do with EQing a sub or creating a house curve.

The best way to set a house curve is first get a reasonably flat plot, then dial in some boost or cut to your taste.

There are problematic test tone files on the net (we won't say what very popular site is hosting them) that don't have the same output levels for each frequency. That's why it's best to use tone generator software and your PC for these types of tests.

**Chris D** · 10 March 2006, 05:54 Friday

Well, it seems like the original settings I had, including "Line In" on the soundcard, does properly input the reading from the RS meter to the soundcard. However, it seems that the Room EQ Wizard is saying that the readings are not strong enough to give a good input range during equalization.

Note that if I turn down the SPL meter to 60db and try the auto "set input volume" it DOES work and finish the process, with an average of about -1db for "Peak" and -10db for "RMS". The auto setting chooses .961 for the input volume. The actual RS meter is pegged at maximum for the whole time. (which would make sense, as it's reading a 75 db calibration tone from my subwoofers)

So, further questions:

- If I leave the SPL meter at 80db, are those readings good enough to continue? (I realize that the instructions suggest at least -24db RMS)

- If not, should I go with the 70db setting, or the 60db? As I mentioned, I thought that the 60db setting would not be wanted--wouldn't it prevent calibrating to the THX 75 db reference level?

**Nick M** · 10 March 2006, 08:32 Friday

I'm reading and following along, but I didn't use software for my readings... I used pen and paper so I can't be of much help.

Hope you get it all worked out! :T

**ThomasW** · 10 March 2006, 12:28 Friday

Ok you're confusing me.

Forget about the readings from the RS meter. Set the dial to 100 or something then ignore it. The only SPL readings you're concerned with are the ones seen in REQW box.

Yes the goal is to get a output level that REQW is happy using, so something closer to -24dB RMS. To do that raise the output level in the mixer or turn up the volume control in your prepro

The RS meter readings or the SPL readings seen in REQW window, have nothing to do with THX or any other form of 'calibration' So forget everything regarding calibration when using REQW. And forget about REQW when your setting the calibrations levels in your processor.

Finally you don't want to use the 'Sine Wave' output setting , use one of the 'Swept' output settings. Meas is the one I use most often

**Azeke** · 10 March 2006, 12:34 Friday

I'll guess I'll wait for the final Reader's Digest version. I am certainly awaiting your final results, to determine if I should add this equipment to my rack.

Good luck and keep us posted Chris.

Peace and blessings,

Azeke

**ThomasW** · 10 March 2006, 12:45 Friday

Azeke,

This is taking more than the usual mount of time since Chris is using a PCMCIA soundcard. A USB card is much easier. Also if anyone is considering this, it's a lot easier and much more accurate to use the $50 Behringer ECM8000 or $40 Nady CM100 microphones instead of the RS SPL meter.

OR one can get the Behringer DEQ2496 and have a stand-alone device that has a built-in 61 band Real-Time Analyzer and has incredible EQing functions....:wink:

**Chris D** · 10 March 2006, 15:40 Friday

Thomas - sorry, you're right of course, I keep incorrectly using the term "calibration" when I mean "equalization". My sub levels are already calibrated to THX reference levels in my pre/pro using the Parasound auto-calibration process as well as the old tried-and-true Radio Shack SPL readings and test tones. What I'm trying to do now is EQ my sub so it gives a flat response over the subwoofer frequency spectrum.

I've been also E-mailing the designer of the Room EQ Wizard, John Mulcahey, who has been VERY nice and helpful. Here's his latest response to the same things I've been posting here:

You're going to an input on your pre/pro, correct? If so, try setting the input level with a speaker cal signal rather than sub cal (so the cal signal will play out of the speaker on whichever side you connected up to), leaving the RS meter on the 80dB setting.

I have made some changes to the averaging used in the input level setting on the current dev build as I suspect it is not averaged enough for the inherent lumpiness of the sub cal signal, using speaker cal should give more consistent results. You could go down to the 70dB meter setting if necessary (if you still end up at input volume = 1.0 on 80dB) but don't go lower than that.

I might try the speaker cal signal, but based on the readings that I'm getting when I set my SPL meter to the 70 db setting, I think I'll just accept and go with that.

(averages about -10db for "Peak" and -18db for "RMS")

I should have a rest of a fun day.

**Chris D** · 12 March 2006, 00:02 Sunday

Okay, I installed the latest driver for my Audigy 2 ZS notebook sound card, which seemed to improve things a little bit. Still couldn't get the input volume to work at the SPL meter setting of 80db, but I got it to work at 70db and decided to go with that.

Here's some screen captures--

The measured soundcard response of my Audigy 2 ZS notebook card: (note that the new Radio Shack calibration file is underlayed)

Following the REQ Wizard instructions, it suggests testing the soundcard calibration by running an EQ sweep on the left channel while the soundcard is still looped to itself. Here's what I got--it's not exactly what the help file says it should look like, but it's purely flat except the extremes. My concern here is that there's a steady downward curve all through the bass frequencies, which is entirely where I'm trying to EQ. The REQ help file indicates that it should be flat all through there, and then actually taper off downward.

Alright, DEEP BREATH! Let's try the first sweep. Drum roll, and...

Just to try for precision, I ran another auto calibration at 1Hz increments from 10Hz to 200Hz. And we get...

Holy crap, does my bass response really look like that? No, that can't be right. (can it?) That is SCARY. So if I try to rescale the same graph to something more standard (15 to 200 Hz, 45 to 105 db, logarithmic scale) we get a much different appearance. My crossover is set at 80Hz in my Parasound C1 pre/pro, BTW.

Looks like I have some work to do. Comments from people? Is this even salvageable? I'll start trying filters here shortly.

**Chris D** · 12 March 2006, 05:03 Sunday

And now the fun part begins, which I did tonight. I took the 1Hz auto measurement sweep I did last night, and then had REQ identify peaks (it picked three) and then assign filters. It assigned 3 filters, one for each peak. As I had two distinct dips, (especially after applying the first 3 filters) I chose to also add two manual filters that are BOOSTS. Yes, I understand that you want to be careful with boosts and not add them if you don't have to, but in this case, I don't know what else I could do. (see above for my big dip at 34 Hz) So these are the filters the REQ added:

# Freq Gain BW Oct
1 47.98 -7.5 0.143
2 26.98 -3.0 0.143
3 29.92 -3.5 0.143

and here's the manual boosts I added:

4 33.96 7.5 0.250
5 23.77 2.5 0.125

Look at the numbers at the top of this graph to see where the filters were added and the response that REQ ***PREDICTED*** the filters would give. (note that Special is greyed out because I had played around with another filter to see possible affects but didn't like it so I unchecked it so it was not implemented. I don't know how to DELETE filter #6)

So I try the upload for the first time... works like a champ. I'm liking my M-audio USB-MIDI cable MUCH more than the Voyetra model I previously tried and returned. I assume that when you have two subwoofers like me and are tuning both simultaneously, that you upload whatever filters you add to BOTH the left and right channels of the BFD. (if anybody knows of a better way to do two subs, I'm all ears) The filters go right into the BFD with no hassle, and I'm done with the first iteration.

To be safe, I start over at this point and recheck the "set measurement" and "set input volume" levels. Maybe it's just me, but it seems now that my SPL meter readings are more stable, still jumping around by a couple db's with every reading, but less pronounced.

I do another 1Hz frequency sweep now to see what the filters REALLY did to the subs, and here's what I get, again as a raw graph of 10 Hz to 220 Hz.

Well, it looks better, but man, that upper end is still ugly as the sub rolls off around the crossover range. Again, here's the exact same graph, rescaled and logarithmic as is standard...

Note that this is actually pretty close to what REQ predicted my filters would do. So, guys that have EQ'd their subs, would you do these filters different? Or at this point, what would you do? Accept the new graph as made, or add more filters for better? Can anything be done with my crappy response from 70 Hz on up? (or should I even worry about it?)

**Paul H** · 12 March 2006, 06:35 Sunday

Chris,

Your measured un-equalized response looks typical for the few rooms I've measured and ones I've seen posted on the net.

I'm assuming that the blue line is the 'perfect' frequency response for your crossover. I EQ'ed mine by running the sub without a crossover and aiming for flat response.

It looks like you have everything in good shape, except for that 'hole' just under 90 Hz. You may be able to reduce that by minor movement of your subs, and you probably should try to deal with that as it will will impact your overall frequency response. I'd be trying to EQ the response up to twice your sub crossover frequency (ie 160Hz if your sub xover is 80Hz).

Paul

**ThomasW** · 12 March 2006, 10:30 Sunday

Most people find a flat plot (straight line) a bit dull. So they create their house curve. Mine has a rising response as the frequencies go down. Now I can get away with that because my IB has so much headroom.

With your ported subs you do not want to boost below the tuning frequency of the port. Doing so will cause the drivers to 'unload' and that's a very bad thing......

**Chris D** · 12 March 2006, 11:48 Sunday

Ah, good stuff.

The blue line is what automatically came up in the Room EQ Wizard for a desired response, without me loading a house curve. I assumed it looked like that not because of a house curve per se, but because of a very gentle roll-off to a crossover frequency.

Thomas, can you help me understand more what you're talking about with boosting? For those who didn't read above, my subs are TWO SVS cylinder PC-Ultras.

After talking to the SVS bubbas a while back, I have the foam tuning inserts plugged into one port on each of the subwoofers, which is supposed to tune the sub down to 16 Hz. Here's a performance graph from the SVS website of the PC Ultra sub untuned (blue) and one port blocked (green).

Attached Files

**Chris D** · 12 March 2006, 11:56 Sunday

Heck, while I'm doing this, I might as well post a picture of where I have my subs placed, as that goes directly into the tuning part. Here's where the subs are, on my front proscenium stage behind the false screen wall, slightly non-symmetric on purpose to attempt to avoid nodes. The picture was taken before painting and covering with fabric and the screen.

It doesn't matter for this discussion, but here's a dark finished picture of my theater and screen wall:

Pics of my theater can be found in these discussion threads here:

Pictures of my Equipment Rack in Progress - HTGuide Forum

https://www.htguide.com/forum/showthread.php?t=13046

Some sample pictures to whet your appetite of my current equipment rack. Theater project is nearing the end. The actual rack, current as of today. Not fully complete, but pretty much so. I chose to go with a horizontal rack to allow the large window above it to remain unobstructed to allow light and airiness into the room when

New theater pictures to tease your appetite - HTGuide Forum

https://www.htguide.com/forum/showthread.php?t=18352

Here's a few samples of the latest Chris D Globe Theater to tease your appetite. Enjoy. From my Home favorite DVD of all time. Kudos to anyone who can name it. Extra special points to anyone who can name the CHAPTER (or scene title) that this comes from. It's actually quite famous. Unfortunately, it's just so

I can move the subs anywhere necessary as long as they stay BEHIND THE SCREEN WALL, which of course does somewhat limit movement. Would anybody put them somewhere different than where they already are?

On a related topic, I'm not sure how to properly set the phase on the subwoofers, given that I have two of them. My setting is fairly arbitrary right now. Both PC-Ultras have a continuously variable phase knob, so I can set it anywhere.

**Paul H** · 12 March 2006, 14:38 Sunday

Originally posted by ThomasW

Most people find a flat plot (straight line) a bit dull. So they create their house curve. ...

You're correct of course Thomas - my post was too short. I EQ'ed flat and then added one more filter for an upward slope at the bottom end for my 'house curve'.

Paul

**ThomasW** · 12 March 2006, 14:51 Sunday

Thomas, can you help me understand more what you're talking about with boosting?

https://home.comcast.net/~thomasw_2/...ndEQpage5.html

What can I say it's increasing the output over a particular passband using EQ. Your subs are tuned to 20Hz I assume? Regardless you don't use boost (+ gain) below the tuning frequency of a ported sub. Other than that you're free to experiment with increasing the output at any frequency or group of frequencies you want.

Lets's say you want everything to sound like Reggae' music or Rap....:wink: So set a filter around 60Hz, with a 1/3 octave bandwidth, then dial in 20dB of boost (+ gain). Now everything you play will sound like it was mixed in a Reggae' studio..... :B

**dyazdani** · 12 March 2006, 22:00 Sunday

I just hooked up my BFD tonight! Going through some testing and played around with Room EQ Wizard using my computer speakers. I seem to be able to get a good signal and measure so far.

I don't have a laptop except for my work issued PC, I'm not sure if I can install it or not, about to try. I'm also a little nervous about the sound card on the laptop.

Chris, perfect timing on this thread!

**wkhanna** · 12 March 2006, 22:16 Sunday

I just wanted to say that, as I have been watching this thread form its beginning, this is one of the most informative and interesting threads I have seen yet!

And as a word of encouragement, “Way to Go Chris!”

**ThomasW** · 12 March 2006, 23:15 Sunday

Danish

Most laptops only have mic inputs and 1/2 duplex soundcards those don't work for test mics or the RS meter.
If you're using the RS meter then grab a Sound Blaster MP3+ external USB soundcard $32

Here's more info about all this ....

https://home.comcast.net/~thomasw_2/SubwooferSetupandEQpage8.html

**dyazdani** · 13 March 2006, 00:00 Monday

Originally posted by ThomasW

Danish

Most laptops only have mic inputs and 1/2 duplex soundcards those don't work for test mics or the RS meter.
If you're using the RS meter then grab a Sound Blaster MP3+ external USB soundcard $32

Here's more info about all this ....
https://home.comcast.net/~thomasw_2/...ndEQpage8.html

Yep, I knew that, but I was hoping to get lucky. Our Wal-mart has those MP3+ on closeout. I may just move my desktop out there temporarily since I already set up REW.

I got the BFD installed and the proper input level set. I need to build a long (like 20ft) cable to hook up the RS meter and reach my listening position.

**Chris D** · 13 March 2006, 00:35 Monday

Oh, well, okay, THANKS! Mostly, I was just trying to get some help with my EQ process and confirm whether I was doing things right, but I'm really glad to help, too!

Thomas, actually, as I mentioned above, both of my subs are tuned to 16 Hz. Since my lowest freq boost is 2.5 db at 23.77 Hz, BW Oct of .125, that's not a problem, is it?

I think I'm going to try boosting the two HUGE dips I have around 75 and 100 db, too.

**Chris D** · 13 March 2006, 00:38 Monday

Dan, that's the way to do it--if you have to choose one cable to be long, put the computer by the BFD and pre/pro equipment stack, and all you need is a long single audio RCA cable from the meter/mic to the soundcard.

I'm sure Doug would be willing to make you one out of solid silver!

**ThomasW** · 13 March 2006, 00:52 Monday

Since my lowest freq boost is 2.5 db at 23.77 Hz, BW Oct of .125, that's not a problem, is it?

I though you had a FBQ2496? It's lowest filter is 20Hz and it has an amazing selection of BW's

I think I'm going to try boosting the two HUGE dips I have around 75 and 100 db, too.

What crossover frequency are you using?

**Chris D** · 13 March 2006, 01:26 Monday

Yup, a FBQ2496. Am I missing something with the filter? I'm trying to understand if you're saying I shouldn't use that boost filter at 23.77 Hz. My crossover is currently set at 80 Hz in my Parasound C1 pre/pro--I'm trying to consider what others have said here about EQ-ing up to 1.5 or 2 times the crossover freq.

**dyazdani** · 13 March 2006, 09:48 Monday

Originally posted by Chris D

I'm sure Doug would be willing to make you one out of solid silver!

Yeah, I'm sure he would. I don't think I could even pay for it given the new kitchen purchases plus my sub repair.

I'm going to RS this afternoon to get some RCA connectors to build my cable. I'll post the results when I get everything going.

**dyazdani** · 13 March 2006, 10:02 Monday

I've been doing some further reading and have a dumb question.

Some places (like the REW help file) suggest that to set up the BFD, you want to hook your soundcard output directly to the BFD rather than to your pre/pro.

Why wouldn't you use the pre/pro (like Chris did) and then run the pre/pro LFE to the BFD and test/setup under the same conditions as normal operation? Don't you want to take into account the bass management to truly set the EQ up properly?

See this quote from the REW help file...

Measurements may be made by connecting directly to an equaliser or by connecting to an AV processor input. If your aim is solely to configure an equaliser (such as BFD Pro DSP1124P or FBQ2496) to optimise your subwoofer's response, connect one of the soundcard's line outputs directly to the equaliser input in place of the Sub connection from your AV processor.

**ThomasW** · 13 March 2006, 10:40 Monday

I'm trying to consider what others have said here about EQ-ing up to 1.5 or 2 times the crossover freq.

Depends on what you're trying to accomplish.....and yes for certain tasks using filters well above the XO point has interesting results.

REQW makes it extremely easy to 'play' with filters in the abstract. Pop open a filter window. Choose the frequency then experiment by looking at the results when you increase/decrease the bandwidth and the amount of boost or cut.

Generally speaking is best to use wide (broad) filters whenever possible. Narrow filters can have a negative effect on the SQ because they can change the Qtc of the sub alignment. So use them only when absolutely necessary.

Danish,

It doesn't matter whether you run the software through the pre-pro or straight to the equalizer. Starting off it's usually a good idea to see what the sub is doing all by itself, (how the top-end rolls off) then add in the mains near the XO point..

**dyazdani** · 13 March 2006, 11:10 Monday

Originally posted by ThomasW

It doesn't matter whether you run the software through the pre-pro or straight to the equalizer. Starting off it's usually a good idea to see what the sub is doing all by itself, (how the top-end rolls off) then add in the mains near the XO point..

Gotcha. I can't adjust the XO, but I guess I can take a look and see if there are any top-end anomalies that need to be corrected. Then check the integration and overall EQ setup after...

I don't have a MIDI connection to the BFD so I guess it's the old fashioned way for me!

**Chris D** · 13 March 2006, 16:44 Monday

Dan, as the REQW doesn't have the capability yet of READING settings in the BFD, the only thing the MIDI cable is good for is purely uploading the filters. It does make it lightning-quick easy, but not necessary. FWIW, my USB to MIDI cable was only $40, so it's not like you have to buy another uber-expensive piece of equipment.

**dyazdani** · 13 March 2006, 16:50 Monday

Originally posted by Chris D

Dan, as the REQW doesn't have the capability yet of READING settings in the BFD, the only thing the MIDI cable is good for is purely uploading the filters. It does make it lightning-quick easy, but not necessary. FWIW, my USB to MIDI cable was only $40, so it's not like you have to buy another uber-expensive piece of equipment.

Yeah, I meant I'd just have to "upload" the filter settings to the BFD with elbow grease.

It's not that ONE piece of equipment that matters. It's $40 for the MIDI, $50 for the Behringer mic I want, $20 for a stand, $40 for a USB sound card...

**PiDD** · 13 March 2006, 18:12 Monday

Hey Chris,

I started doing my calibrations around the same time you started ... and what a surprise our graphs look very simular. So I am interested in your results.

One suggestion .. get rid of the RS meter and get a Behringer 8000 (ebay Item number: 7396590213) and a mic amp. You will get much better results.

**dyazdani** · 13 March 2006, 22:09 Monday

Here's a start... it took me a while since I had to move my desktop out to the living room. I also had a few issues setting the input volume - REQW wouldn't move it on its own and gave me an error (to low level), it took me a while to figure that out.

Anyway, the rest went smoothly although I didn't have as much time to fine tune as I wanted.

Here are 3 captures: unfiltered, the proposed filters, and the final (for today) result. I didn't worry to much about the absolute level, I made a change midway and didn't reset the target level. Just focused on flattening out the curve.

Image not available

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After I got the sub lined out - I re-measured with the mains. All looked good except for a deep, narrow null at 80Hz (XO freq, coincidence?). I dialed in another small boost and packed up. I didn't save that graph as I was sick of messing around (haven't eaten, wife is sick, etc)

The wide BW cut around 20Hz didn't do as much as I thought it would. Oh well, save it for another day.

**Chris D** · 13 March 2006, 22:34 Monday

PiDD, that's funny... I'll check that specific Ebay auction. (EDIT: just checked, and the auction closed without any bids. Is that you? I'd be willing to talk) I've considered upgrading to a better calibration tool than the RS SPL meter, but as of yet haven't been able to justify the cost. Paying all that money for new equipment when I've already got a decent solution doesn't make me very confident that I'll get significant changes that would make it worthwhile.

I've made some progress in my sub EQ. Posting more tonight.

**PiDD** · 14 March 2006, 00:03 Tuesday

The auction isnt mine... but here is another 7397474898. You need an amp with it. I used the Eurorack UB802 (7397552377). So for under $100 you have a pretty good measurement tool.

These have worked well for me. I just didnt trust the RS meter knowing that the lows just arent captured properly.

**ThomasW** · 14 March 2006, 01:45 Tuesday

One can buy the Nady CM-100 for $40 everyday at retail. It is the same mic as the ECM-8000

Google Search

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2004-07,GGLD:en&q=Nady+CM%2D100

**Chris D** · 14 March 2006, 03:51 Tuesday

Well, after posting my last graph, I went back to add some additional filters last night for the purpose of trying to boost out the huge dips I've got above 70 Hz. I fired up my laptop, turned on my equipment, let everything warm up, and then again set my measurement and volume levels. Nothing had really changed, all levels were the same. I then decided to do another frequency sweep before I added the filters, and the graph looked funny, like all readings were at a bit higher level. I rechecked all connections and settings, and yes, everything was the same. I hadn't even moved the SPL meter on the microphone stand, they had stayed in the same spot over these days. Set the target level again, same thing. I decided to start over, deleted all filters from the BFD, and did a fresh sweep with no filters. Here's what I got:

Note how high the response goes above the target level of 74-75 db at 15-30 Hz and then again at 48 Hz.

So I tried a totally different set of filters this time, including a MASSIVE and wide cut right at 20 Hz (the REQW won't allow you to set a filter any lower then 20 Hz) and three different boosts from 88 to 122 Hz to raise some of those ugly dips I have in the upper range. Here's the result:

I'm not sure why the readings are still higher than before, but they do seem accurate. For now, I took the EQ as acceptable, and stopped this round of EQ adjustment.

Turned on the rest of the theater, sat down, and started playing some material. Sounded about the same or even better, but I wasn't playing any bass-intensive stuff.

I decided to recheck my pre/pro speaker distance and level calibrations now that I had EQ'd the sub, so I re-ran the auto calibration programs of my Parasound C1 pre/pro, using the Parasound calibration microphone in the microphone stand. Wow, an interesting result. Previously, I had the subwoofer set at -6 db in the pre/pro to equal the mains and other speakers. With the new calibration, all speaker level and distances remained exactly the same (as pretty much expected) except the sub level now came up all the way to -2.5 db! I'd have to attribute this to the big cut I made at 20Hz as well as cutting down the big peak I had at 48 Hz.

So now I started doing some critical listening on material. I wanted to watch something bass-intensive that I hadn't seen for a while so I'd also enjoy a movie, and put in LOTR: Fellowship of the Rings. Played the DTS-ES soundtrack, and WOW. The LOTR trilogy has always been impressive for bass, or even maybe overly hot, but now I was hearing more details in the LFE. Sounds became apparent that I think were overpowered by the peaks before. Much more clean sound, and full of power. My SVS subs can really shake your body and literally blow the hairs on your skin in intense scenes.

Cool. I'm pretty happy. If I could figure out how to do it better, though, I'd be willing to do it again.

**dyazdani** · 14 March 2006, 08:42 Tuesday

Originally posted by Chris D

So I tried a totally different set of filters this time, including a MASSIVE and wide cut right at 20 Hz (the REQW won't allow you to set a filter any lower then 20 Hz) and three different boosts from 88 to 122 Hz to raise some of those ugly dips I have in the upper range. Here's the result:

I had the exact same hump in my response and tried the same sort of filter. It's kind of fun experimenting with the filters, some of the sharp dips are hard to get rid of without comprimising something else.

After going through the trouble setting everything up (moving computer, etc) that $35 for the USB soundcard doesn't seem so bad! Inputting the filters by hand into the BFD isn't so bad, especially now that I've memorized the conversion between REQW and the BFD for bandwidth.

**ThomasW** · 14 March 2006, 10:20 Tuesday

After going through the trouble setting everything up (moving computer, etc) that $35 for the USB soundcard doesn't seem so bad

Having a portable measuring system is a great thing...... :B

**Chris D** · 14 March 2006, 12:10 Tuesday

Nowadays, I consider a computer to be an essential part of a proper upper-end theater. So far, I use my computer to upload firmware updates to my Parasound C1 pre/pro, create custom settings on the C1, program my MX-700 remote control, do parametric EQ on my subs with the Room EQ Wizard and BFD, and create CD-ROMs for firmware updates on my Denon DVD-3910 player.

And that's just the work it does, with current equipment! Imagine how much more future equipment is going to need computer control and adjustment, as well as internet interface. I also have the computer integrated into the theater so I can surf the web or play games on the big screen in surround sound while sitting in my loungers. :T Hidden USB wires extend a mouse, keyboard, gaming equipment, etc to the seating area.

I chose to use a laptop, which works great, because I can take it with me on my trips and move it around the theater if I want. The only downsides are that laptops aren't always as high-powered as desktops (although mine is, a 3.2GHz P4) and I have to disconnect all the cabling ever time I take it out of the equipment stack.

**dyazdani** · 14 March 2006, 12:51 Tuesday

I can't justify buying a whole new laptop just for my EQing, but I don't mind a USB sound card to go with my work-issued model

I'll probably get a laptop my next time around. I can upgrade my desktop fairly easily (aka cheap) as I built it myself and can reuse most things.

**dyazdani** · 14 March 2006, 14:14 Tuesday

Originally posted by ThomasW

Having a portable measuring system is a great thing...... :B

I bought the SB MP3+ at lunch today. You guys are evil :evil:

**ThomasW** · 14 March 2006, 14:36 Tuesday

I bought the SB MP3+ at lunch today. You guys are evil

And proud of it....... :roflmao:

**ToddAnisman** · 22 March 2006, 19:42 Wednesday

Hi Guys- I came in kinda late but I wanted to toss my .02.

OK when tuning a room there are a couple things to take into consid.

A) When Dolby tunes, they position 4 mics in the room. They take reading from all 4 and average them together. the positions are as follows Left, Right, Slightly Off Center Left, and slightly off Center Right Back (2-3ft). No mic should getting "beamed".

B) The Dolby curve is NOT flat 20Hz-20kHz. It is +/- 3dB to 3k then down 3dB/Octave from there. I am looking at some of the curves that I *think* are base-line, and they are much closer to Flat. Your sub should be working with your Mains- It is useless to measure the Freq response of the Sub (Unless you are measureing the LFE channel) without the rest of the measurement.

C) There is a great piece of gear called Syncheck.
http://www.syncheck.com/

It will allow you to perfectly time out your room so that picture and audio are gnats ass in sync. *This is absolutely Crucial for proper freq response in a room*.

D) A theater should be leveld at the following SPL:
L-C-R @ 85dB C weighted slow.
Ls-Rs@ 82dB C weighted slow. When Combined should be 85.
LFE- 89

Tuning your room at 75 (sorry Chris..) isn't optimum because your RT60 (reverberation time) will change a bit. or become more pronounced and the Fletcher-Muson curve dictates how you will hear the audio.

There is a neat tool made by Phonic that can measure RTA, RT60, SPL etc. It is very effective, and can do almost everything that a Full Dolby Laptop can do Phonic PAA-3. This is what I use to tune, and I have found it to be pretty darn close to Dolby.

Also, Chris, Your L-R aren't supposed to be canted in!!!!!! he hehe.

Hope this helps....

-Todd A.

My BFD subwoofer EQ thread

My BFD subwoofer EQ thread

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