Double Bass AER Dual Parametric EQ

[Ric Vice]

Hey All,
I was just looking at Django Books, who carry lots of high end pickups and pre amps. I saw a Dual Parametric EQ that's being built by AER. Here's the pick from the Django website.

Ric

 

[Eric Hochberg]

Looks like it only goes down to 90Hz.

 

[DoubleMIDI]

There is no shelving high pass filter, both are parametric with variable bandwidth (I hope it is misprinted and it is Q factor which is freqency dependant bandwidth).

I'm rather sure for anything lower than 90 Hz you would prefer a shelving filter.

But indeed for bass it would have been better to have a low high pass filter too.

 

[Ric Vice]

There is no shelving high pass filter, both are parametric with variable bandwidth (I hope it is misprinted and it is Q factor which is freqency dependant bandwidth).

I'm rather sure for anything lower than 90 Hz you would prefer a shelving filter.

But indeed for bass it would have been better to have a low high pass filter too.

Double M,
I just thought that I'd through it out for comments as I didn't have time this afternoon to check the AER users guide for the unit. I was hoping it would work, but obviously it won't. The Fishman Dual Parametric DI still wins the contest, unfortunately it's no longer in production.

Ric

 

[drurb]

There is no shelving high pass filter, both are parametric with variable bandwidth (I hope it is misprinted and it is Q factor which is freqency dependant bandwidth).

I'm rather sure for anything lower than 90 Hz you would prefer a shelving filter.

But indeed for bass it would have been better to have a low high pass filter too.

If you're referring to the labeling, the term "bandwidth" would not be a misprint at all. There are no numbers on the knob and Q is, after all, a metric of bandwidth once the center-frequency (CF) is chosen. Q=CF/BW. So if you pick a CF and rotate the knob (which affects Q), then you are changing the bandwidth of the filter directly. Now, if they labeled the knob "relative bandwidth," you'd probably be really happy.

 

[DoubleMIDI]

Thanks for correcting me, drurb.

What I wanted to say is that bandwidth does not make sense musically, because if you adjust the center frequency the musical interval of the filter will change. And I got some devices in my hand some time where the bandwidth varies with center frequency and is not fixed for a varying center frequency. But they printed bandwidth on it. At best it is a misguiding labeling, for someone more picky this is simply wrong. But better if it would behave as a fixed bandwidth for the varying center frequency.

And the main thing I wanted to express was that this device has no shelving filter which Eric might have been missing if I look at his 90 Hz comment.

 

[drurb]

What I wanted to say is that bandwidth does not make sense musically, because if you adjust the center frequency the musical interval of the filter will change.

When doing tone-shaping it is really not about musical intervals. Furthermore, because the knob is not labelled numerically in any fashion, it doesn't preclude that you're changing bandwidth in log space which is likely what's going on.

And I got some devices in my hand some time where the bandwidth varies with center frequency and is not fixed for a varying center frequency.

That's actually the norm for these devices. They are typically constant log filters not constant linear.

But they printed bandwidth on it. At best it is a misguiding labeling, for someone more picky this is simply wrong. But better if it would behave as a fixed bandwidth for the varying center frequency.

Yes, it would be better labelled "relative bandwidth" or "log-bandwidth re CF," or, perhaps, "bandwidth" with the knob marked in fractions of an octave. The designer might say, "When the knob is set here, the bandwidth is a constant 0.5 octave." Really now, for a consumer device, bandwidth, IMO, is just fine. After all, most people don't object to knobs that say "volume." Those should say "gain" because that's what's being directly varied and because "volume" is a psychological quantity that may not vary one-to-one with the knob and is certainly not constant with a fixed position of the knob. Seems like much ado about very little but you are absolutely correct that labeling the knob "Q" would be appropriate. Can you imagine all of the users who would be confused if it were labeled that way? The manufacturer would probably get all kinds of complaints and average user would walk up to the device and have no intuition about what the knob does. I'm willing to give them a pass.

Actually, it would be a less useful device if it were fixed bandwidth for varying CF. I won't go into all the reasons here but a device that maintains a constant fraction of an octave as CF is changes would be most useful. I'm quite confident that's what it actually does.

And the main thing I wanted to express was that this device has no shelving filter which Eric might have been missing if I look at his 90 Hz comment.

Indeed, no high-pass filter.