1st attempt at roomeq for sub advice needed.

[shawn]

Well here goes, either my sub sucks bigtime, or I'm doing something wrong. I have my sub crossover in windows set to 250hz, as that is as high as the sub itself will go anyhow.

I am using a sennheizer mic through mackie soundboard as my input.

I purchased the fbq2496 today, they didn't have the other model, and only after getting back home, 100 mile round trip drive, did I find that this model only has 1 preset....grrrrr.

Anyhow, here is my graph
http://mydreamhost.net/images/sub-a.jpg

I took multiple measurements and they all looked almost the same, so I'll use that one as a reference.

I have the fbq plugged into a midi usb adaptor on my computer, and the sub is routed through the left channel on it. I held the reset button on the fbq for 10 secs or so but the 'filter lift' button still blinks. Not sure if it's really reset. the digital display says 10.

Are there directions for using the fbq somewhere? only found dirs for the other model, and got confused almost immediately as they seem quite different. Like (no in/out button to press and hold) but if I understood correctly the left meter is always set to input anyhow so I did set my sub vol to the orange,with no red clips, guessing that is correct.

Now what do I do? (Not sure this sub is even worth dealing with after seeing my graph, I placed it up front where the bass sounds 'best' in my seating position)
Can't even get past step #1 as I don't have a 'filter' button on my unit.... guessing there is a link for directions on this model somewhere else on this site.

Or if it's an easy thing to do could someone give me step by step directions on how to fix 1 frequency on my graph, and then i can just keep doing that over n over until I get them all fixed?

[Julien43]

Hey Shawn

I am new to this whole measurement and fix thing too. I did notice some things in your post that you might make a difference in your results

"I have my sub crossover in windows set to 250hz"

You might want to try a lower crossover point. You should be able to increase the output level with little or no localization

"I am using a sennheizer mic through mackie soundboard as my input"

I'm sure the Sennheizer is an great mic but. unless you have a plotted response that cal file can be generated from, you can't be sure if your measurements are accurate. (especially in the neither regions)

I'm sure more experienced member will have thoughts on your setup. I hope that helps

[shawn]

Thank you.
I will run out and buy an adaptor for my ratshack meter and try that out with the correction file. I'll also drop it to around 120hz instead of 250 to see if that helps my graphs. I'm shocked that I have nothing below 45hz at all....

One thing I can't figure out, is what to do with the midi part of the fbq. I'm guessing there is some kind of file that I can export from roomeq and then import that into the fbq and it will adjust everything for me. Just can't find even the vaguest instructions on if that is possible and if so how to do that with my unit. I so wish the store had the other 'lower end' unit in stock.....

I 'kinda' figured out how to make a change on the fbq, meaning
1. assigning a channel for parametric
2. assigning a frequency
3. bandwidth----I have ZERO idea what this part means, I know it's how 'wide' to notch, but the numbers don't equate to anything I understand.
4. gain makes sense

I'd hate to have to do this manually, but will if it's the only way. Either way I'm gonna have to figure out how to read my graph and figure out how much 'bandwidth' that comes to for each filter I apply. Hope someone can chime in on that.

[Otto]

Hey Shawn,

I'll try to help with a couple of the questions.

First, I've never used the 2496, so I don't know anything in particular about it. I know it's different...

The MIDI cable that you have hooked up to the unit from your PC should allow REW to download the filters directly to the unit. There's no file to import or export. Under the "Equaliser" menu, you should find the ability to select your unit, and also an option to "send filters to eq".

The bandwitdh value is octaves divided into 60 parts. That is x/60 will determine your bandwidth that's applied, and x is the value that you're wondering about. So, if you use x = 60, you will affect one octave. x=30, half an octave. For the 1124, the max is 120, which would be two octaves.

That's it for now. A small child is smashing my keyboard!

[Otto]

What sub are you using?

Yeah, it kinda sucks about the one preset, but I get away with it most of the time. You could always return that one and pick an 1124 up on eBay or whatever.

[shawn]

Still trying to figure out this bandwidth thing.
take my first graph for example
http://mydreamhost.net/images/sub-a.jpg

Say I was wanting to deal with the 80hz peak there. It looks like the problem starts going up at 75 and flattens out again at about 85 before it dips below. Pretending I wanted to flatten the area between 75 and 85 to get rid of the 5db increase what settings would I use for the bandwidth? My best guess would be '10' as there is 10 between 75 and 85, but that somehow doesn't seem right.....
Obviously I don't understand octives, and how they relate to the hz/khz on the graph bottom.

I'm going to try and redo the graphs with the rs meter instead of my mic. Should give me a more accurate starting point. Just trying to learn the bandwidth settings while 'help' is still online tonight

Is there anything I need to set on the fbq to 'accept' the graphs? Or does it just kinda happen auto?
tried sending but it says 'generic equaliser settings does not support sending filters to a unit'..... ??lol

[Otto]

Hey there,

To send filters to your device, select "BFD Pro FBQ2496" under the "Equaliser" pull down menu. That should take it away from the "generic" device and start to interact with yours. You may have to do some setup on your machine, and hopefully that will be listed in REW. The 2496 is a little different, so you may have to experiment to get the right means for it to accept communication from REW. If you find that absolutely nothing is going on after all that, try swapping the MIDI connections. Mine are labeled "in" and "out", which, in my case, is from the point of view of the PC, not the BFD.

I started to describe octaves and BW for the BFD, but I found that I'm not 100% sure of how all those relate. I thought I did, but doing a little math and looking at the filter outputs in REW left me unsure. However, if you go into REW and play with those numbers, and look at the resulting "corrected" sub output, it will give you a very good feel for how it will affect the original curve.

My apologies for not having a better answer for the bandwidth thing. I'm sure brucek will know. And I'm sure it's in the manual/setup guide for the BFD. I believe the BW stuff will apply to the 2496 the same as it does to the 1124.

[Otto]

Here's some discussion from brucek on bandwidth. I didn't read the whole thing, but I think this will help.

http://www.hometheatershack.com/foru...dwidthinfo.htm

[terry j]

hi shawn

IIRC the formula is rather simple

it is the f3 point above minus the f3 point below divided by the centre point

so in your example

center point approx 80 hz at 95 db (you can put the cursor on the point and read the values below)

upper f3 point (ie 92 db) is approx 84hz.

lower f3 point, again 93 is approx 75 hz

84 - 75 = 9, divided by 80 =.1125. That is the Q of the curve.

If your unit does not accept Q, then as you say you need to convert it to bandwidth.

Hope I didn't get the formula wrong!!

Under the equalizer tab, try clicking the various options, TMREQ, BFD, generic etc. You will at some point find a format that will give the result in bandwidth rather than Q.

Don't worry about the link to the unit, it takes very little effort to enter the results manually. All the better if it works, but don't let it not working hold you up.

Now, as invariably happens, more knowledgable people will pop on and correct everything I just said and you will be away!! ha ha

An alternative to mathematically working it out, especially if I was wrong, is to change the filters from auto to manual, change type to PK and then play with the parameters whilst watching the graphic results. Hope that made sense

[brucek]

Read the REW HELP FILES. They will help a lot.

Read here about how to easily post graphs.

Download the BEHRINGER FBQ 2496 MANUAL and learn how to use the front panel. It's not difficult really.

Post your graphs using a Graph Axis Limit in REW with vertical scale of (45dB to 105dB) and horizontal from (15Hz to 200Hz).

Use the Radio Shack meter and not a microphone without a calibration file.

Select the FBQ 2496 equalizer in REW as the unit you're using. It is selected under the Equalizer pull-down.



brucek

[Otto]

Yeah, don't listen to my simplified answer about it being octaves/60 or whatever. That's a poor answer... I'll have to read up on the whole BW thing.

Sorry...

[shawn]

arrrggghhhh
I gave up....
Used the rs meter instead of mic, and everytime I would drop the volume to get it tuned to 75db, and then try and measure, levels were always way to low and the charts made zero sense anyhow.

I did it the manual way per instructions on this site and ended up with the following graph


I couldn't do the initial at 16hz as I get nothing out of the sub below 21hz at all, so I started there.

Now comes the huge request
Could someone use my graph and come up with the filters I need for my fbq?
Math is hands down my worst subject, failed math80 3x before giving up

[shawn]

tons of trial n error later, still not sure what i was doing and here is the new graph with 8 filters applied.


I think that's the best I'm going to get out of this sub.
The dip at 160 I can't get rid of. It's so bad that when the frequency plays I hear it for about a second in the beginning and end but the middle is almost gone with no sound. Kinda strange....

Now off to listen and see if I like it any better, fingers crossed.

[shawn]

Well I must have done something wrong because it sounds like crap. My bass is gone now. I suppose next step is to try the room graphs, or figure out how to do this via the software instead of manual mode like I ended up doing.

.....If only there was a way to plug the mic in, press a button, have it play, and auto setup my eq for me...

In 'auto' mode I can't even get past the first step, as when I calibrate the sub to 75db, and try to measure, it always says level is to low. Which I can def understand, as I can barely hear the bass at that low a level. Now with the main speakers at 75db I can hear it just fine and the levels work.

How do you guys set it up with the rs meter trying to calibrate at 75db?
How do you get past the 'level to low' error in the measure tab 'check levels' part when testing the sub?

also:
I read a number of posts over at avs about how the volume for subs makes a HUGE difference when measuring as to the actual frequency graphs. How when you graph at a low level and change nothing then graph at 'listening' levels the graph will totally change. Is this correct info, or just blowing smoke?
Can provide link if needed.

[brucek]

If only there was a way to plug the mic in, press a button, have it play, and auto setup my eq for me

There is

as when I calibrate the sub to 75db, and try to measure, it always says level is to low.

Are you checking that level with the Check/Set levels with subwoofer set as the source in the pulldown beside the Check Levels button?
When you press Check Levels in the Measurement routine do you have the End Frequency set to 200Hz?

or just blowing smoke?

you said it.....blowing smoke..

If your sub is truely set to 75 db using the REW band limited pink noise for a subwoofer, then it's plently loud enough.

brucek

[Wayne A. Pflughaupt]

tons of trial n error later, still not sure what i was doing and here is the new graph with 8 filters applied.

Actually, that’s not bad for a newbie, doing that with only 8 filters. Congrats!

Well I must have done something wrong because it sounds like crap. My bass is gone now. I suppose next step is to try the room graphs, or figure out how to do this via the software instead of manual mode like I ended up doing.

Yup – typical problem. Check out our House Curve article for the solution.

Regards,
Wayne.

[Wayne A. Pflughaupt]

tons of trial n error later, still not sure what i was doing and here is the new graph with 8 filters applied.

Actually, that’s not bad for a newbie, doing that with only 8 filters. Congrats!

Well I must have done something wrong because it sounds like crap. My bass is gone now. I suppose next step is to try the room graphs, or figure out how to do this via the software instead of manual mode like I ended up doing.

Yup – typical problem. Check out our sticky House Curve article for the solution.

Is this correct info, or just blowing smoke?

There’s a lot of “smoke” over there... The only truth to it is that you have to have the signal level up high enough so that ambient room noise isn’t polluting the readings, and not so high that you smoke your sub before you get it equalized.

Regards,
Wayne.

[shawn]

brucek wrote:

There is


Are you checking that level with the Check/Set levels with subwoofer set as the source in the pulldown beside the Check Levels button?
When you press Check Levels in the Measurement routine do you have the End Frequency set to 200Hz?


you said it.....blowing smoke..

If your sub is truely set to 75 db using the REW band limited pink noise for a subwoofer, then it's plently loud enough.

brucek

thnks, I've seen the velodyne system before. Shoulda said pc software that does what I was trying.

Yes chec/set levels with subwoofer is my choice in the levels dropdown.
I had the end frequency at 200hz

I'm guessing I was at 75db, as I used the rs meter in my listening position. Seemed VERY quiet though compared to 75db of pink noise from the main front speakers. Sub just kinda 'rumbles' around at that low a level, hard to hear.

[Wayne A. Pflughaupt]

shawn wrote:

I'm guessing I was at 75db, as I used the rs meter in my listening position. Seemed VERY quiet though compared to 75db of pink noise from the main front speakers. Sub just kinda 'rumbles' around at that low a level, hard to hear.

No “seemed” to it – it is very quiet compared to the mains. Typically the sub is supposed to be hotter than the mains. Did I mention the house curve article?

Regards,
Wayne

[logan00]

Is it a good thing or a bad thing that I only need one filter? After running REW and setting a house curve, only one frequency needed to be cut between 20Hz and 90Hz.

[Otto]

logan00 wrote:

Is it a good thing or a bad thing that I only need one filter? After running REW and setting a house curve, only one frequency needed to be cut between 20Hz and 90Hz.

Hi logan00,

I guess it depends on your initial response. Some frequency responses need no correction.

Post your frequency response graphs in new thread and let's see how they look!