Help with Filters and FBQ 2496

[Nick]

Hello Everyone, I am hoping for some coaching on how to use the FBQ 2496. Please disregard the second graph, I couldn't figure out how to remove it once I started the post.

The first graph shows what REW recommends for filtering and how the new curve will look. I've been reading Wayne's house curve information, but I wanted to try adjusting the BFD first to see if I can do the settings properly. I am inputting the measurements manually into the FBQ. The green lights on the FBQ are peaking on the third notch, so that could be part of the problem.

The measurement is for full-range speakers without a sub. Upon reading Wayne's write-ups on house curves and the manuals, I am unclear on how to set band-width properly on the FBQ. It appears that I need to set it on '1' (.167) for two of the settings and '2' (.20) on the middle peak. Though I think Wayne may have said it is better to set them for something close to a 1/24 octave -- I'm curious what bandwidth setting that is on the FBQ?

Also, should I be trying to increase the null at 56hz, or just leave it alone? I can't do anything about the suckout at 180hz because I have the FBQ only attached to the subwoofers on my speakers that cross over around 92hz.

I tried doing the settings and then ran another measurement. The curve was exactly the same, so I don't think I had the FBQ operating properly. The light on the PEG button is off (it seems it should only be on when making adjustments). Can someone please tell me how the FBQ should 'look' when it is operating?

Thank you in advance,
Nick

[brucek]

When taking measurements and displaying graphs for setting low frequency filters it is best to measure from 0-200Hz and use a horizontal axis in your graphs of 15Hz-200Hz.

Before getting into setting your desired filters with your FBQ, play with it a bit to get a feel for entering filters. Play a (low level) single sine wave with the REW signal generator and enter a single 60Hz filter with -15dB cut (for example) and ensure the signal is attenuated. This type of play where you know what the result should be will help you get use to the front panel.

Once you know how it works, then enter your filters with confidence.

The manual can also help.

brucek

[Nick]

Brucek, thank you for your help. I have re-read the manual and picked up a lot more helpful information. I did the 60hz sine test at -15dbs and the filter measured exactly 15db less on the RS meter. However, when I input filters and then re-measure I get measurements that are exactly the same.

I tried to adjust the input levels in bypass mode on the BFD, but wasn't able to figure out how to adjust the level. I am confused how about how to raise the input level.

By the way, my speakers cross over at 90hz. Should I be trying to increase the levels between 20-40hz?

Thank you,
Nick
Attachment 17077

[brucek]

I did the 60hz sine test at -15dbs and the filter measured exactly 15db less on the RS meter. However, when I input filters and then re-measure I get measurements that are exactly the same.

Can you explain this further. I'm afraid I don't understand.

I am confused how about how to raise the input level.

Turn up the subwoofer trim level in your receiver.

brucek

[Nick]

Brucek,

Thank you for your response. What I meant was that when I tested the FBQ with a 60hz test tone it attenuates when I use a filter at 60hz. However, when I input filters that are recommended by REW and measure with and without the filters I get the same reading for each measurement (as shown two posts above).

I don't have a receiver, just a preamp and an amps and full range speakers. My preamps have two outputs designed to adjust the levels when two amps are being used to match the gain. If I raise it a lot to increase the bass, the m/h frequencies will be much lower than the low frequencies (I do have them passively biamped - meaning no outboard crossover).

Nick

[brucek]

What I meant was that when I tested the FBQ with a 60hz test tone it attenuates when I use a filter at 60hz. However, when I input filters that are recommended by REW and measure with and without the filters I get the same reading for each measurement (as shown two posts above).

I guess there can't be much argument that those filters you're entering from REW simply aren't being saved in the FBQ. Are you entering them by hand the same way you entered your test 60Hz filter?

I don't have a receiver, just a preamp and an amps and full range speakers. My preamps have two outputs designed to adjust the levels when two amps are being used to match the gain. If I raise it a lot to increase the bass, the m/h frequencies will be much lower than the low frequencies (I do have them passively biamped - meaning no outboard crossover).

That's fine then, don't mess up your levels to your amps. The reason for adjusting the input level to the FBQ is just to take as much advantage as many bits as possible, but it's not important enough to mess with your gain balance of your amps.

How are you feeding the FBQ - with splitters from the preamp?

brucek

[Nick]

As far as I can tell I am doing the same process for the filters I'm entering into the FBQ as I did with the 60hz test tone. The readout says 'run' and the lights for the three filters (18-20) are lit. The single shot lights are coming on also when I play music - sometimes one and sometimes up to four.

As you suggest, it could be my connection to the preamp. I do not have a splitter from the preamp to the FBQ (I have one from the soundcard to the preamp in the AUX input). From the preamp to the FBQ I have a pair of RCAs with 1/4 inch connectors leading into the right and left inputs of the FBQ and then another pair of RCAs with 1/4" connectors going out to the amps from the FBQ.

Thank you for your help, Brucek.

Nick

[rickp]

What I meant was that when I tested the FBQ with a 60hz test tone it attenuates when I use a filter at 60hz. However, when I input filters that are recommended by REW and measure with and without the filters I get the same reading for each measurement (as shown two posts above).

I had the same problem loading filters on my unit. I ended up having to turn the FBQ off after making a setting and then turning it back on again before it would lock in. Someone has suggested you have to push and hold the PEQ button to lock in, but I havent tried that yet. Also once the settings are locked to a channel you can change them without having to cycle the unit off and on again. Hope this helps.

Rick

[Nick]

Thank you for the suggestion Rick. I'd like to clarify -- I think you mean turn off the power to the unit, versus having the readout say 'off' (as when it is in the bypass mode)?

Also, should the single shot filters be operational on their own? I am listening right now and #s 1-2 are lit.

Regards,
Nick

[brucek]

With the BFD and the FBQ, the first thing you do when you purchase it is to place all the filters in the banks to 'OFF' mode. Then when a filter is added, change it to 'PA' mode. You don't want it to act as a feedback destroyer.......

[Nick]

I have put all 20 of the filters into PEG mode and verified that the gain is set to zero on all of them. I have not been able to find something in the manual that says how to put each filter into 'off' mode. I still get no change in my measurement with filters 19 and 20 set to attenuate the peaks.

The manual does state that the filters that are activated should blink periodically. They are staying lit with no blinking after they are set.

I am also unable to find something that explains how to put it into 'PA' mode. Is there an explanation somewhere?

I did shut off the power and turn it back on with no change in measurement.

Thank you again,
Nick