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cturner
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288 posts since 7 Dec, 2009, from GWB

Postby cturner; Fri May 18, 2018 5:24 am Frequency Response of Bass Impulses?

Greetings-

I hope folks don't mind my posting a general question here, but I'm a great fan of Kazrog stuff, and respect the contributions of many that post here. And I must remind everyone that I'm not a guitarist.

I was working on bass tone for a project and it had me looking at the frequency response of the various bass impulses I had. The thing I found mysterious was that they almost universally featured a huge difference in response between the lowest and highest notes: E1 through G2, or the 41.20-98hz region. You can see this is the screenshots I've attached below.

I would have thought one would want flat response, or even an inverse curve a la Fletcher-Munson, it generally seems the cabinet impulses have the highest note on a 4-string bass about 10-12dB higher than the lowest. Can anyone explain the rationale for this?

Thanks!

Kazrog Neo 410.png

Redwirez SVT810.png

3Sigma Acoust 810.png
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Kazrog
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754 posts since 24 Oct, 2009

Postby Kazrog; Fri May 18, 2018 7:12 am Re: Frequency Response of Bass Impulses?

It's probably easiest to assess the frequency response with pink noise as your test signal.

As for the philosophy behind putting a microphone on a speaker cabinet in general, or even the rationale behind guitar and bass speaker design, for the most part it's a lot of tradition and mysticism, and it has absolutely nothing to do with a flat response or high fidelity. Quite the opposite, actually!

So much of what we do in the context of electric guitar and bass is anti-fidelity. It's really about sculpting the tone of the source, carving a spot for it in the mix.
Shane McFee
CEO/CTO - Kazrog LLC
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cturner
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288 posts since 7 Dec, 2009, from GWB

Postby cturner; Sat May 19, 2018 10:04 am Re: Frequency Response of Bass Impulses?

Thanks for your response, Kazrog, that's most certainly true, although I would good so far as to say the observation applies to almost everything we practice in the electronic craft that underlies musical art.

I think I've found the answer to my question, but first, I should provide a bit of backstory. I had been driving subs into the Thermionik power amps to hear what kind of saturation they might give, and completing that, decided to use my sub with a complete Thermionik bass amp and cabinet. This resulted in a hugely diminished low-end, with an easy 10dB difference between E1 and G2; not the kind of thing that's easily compensated for with a change of MIDI velocity, compression or what-have-you.

I believe my trouble is in running what amounts to an "harmonically-starved" sine wave through your amp sims, where on the other hand, guitars produce an abundance of harmonics. More specifically, I think that the 2nd and 3rd harmonics of an electric bass are stronger than (or at least as strong as) the fundamental, and so for the most part, the strength of the bass note is above the loudspeaker roll-off that seems to occur around 100hz.

Here are two admittedly limited examples of E1 played on IK's MODO Bass, and from the Wilkinson Zombass samples:

Papen vs MODO.png

Papen vs Zombass.png

They're not exactly amplitude matched, but it's plain in these two cases at least that the 2nd and 3rd harmonics are very important for delivery bass sound through the roll-off of a loudspeaker. It's perhaps also an example of the "missing fundamental" phenomenon that the Waves MaxxBass/RenBass plugs make use of.

There's probably more to be said here, especially WRT to this thread: https://www.kvraudio.com/forum/viewtopic.php?f=267&t=483458 which could be read as being guitar-centric, omitting the specifics of where an ampsim/cabinet might best be placed in the chain, or mentioning sub-synthesis as a component of recorded bass sound. Certainly I'm no expert on these topics.

I also tried pink noise (thanks for the tip!) and there is a difference between it and impulse response, but it didn't make my observation go away:

Kazrog AG 412 pink.png

All the best, Charles
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Kazrog
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754 posts since 24 Oct, 2009

Postby Kazrog; Sat May 19, 2018 10:11 am Re: Frequency Response of Bass Impulses?

Your best bet with bass is always to use a combination of a dry compressed DI signal with your processed signal through whatever amp/cabinet simulation you're using. You should never rely on the tone you get through the cabinet IR 100% if you want any clarity at all.
Shane McFee
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cturner
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288 posts since 7 Dec, 2009, from GWB

Postby cturner; Sun May 20, 2018 2:31 am Re: Frequency Response of Bass Impulses?

Thanks Kazrog. I found this bit of an interview with Bob Gallien of interest:

"One of the biggest keys to making a great bass amp is the manner in which you roll off the low end because you really have to pay attention to the roll off rate and the way it fades. Nowadays, speaker systems can handle really deep bass sounds, but back in the day, they couldn't. At the time, everyone was playing 4-string basses so the demand for producing lots of really deep bass was not there. For example, the 800RB doesn't produce a lot of low end response, but it has just enough to accommodate the frequency range of a 4-string bass. That amplifier is not going to work all that well with the B-string of a 5-string bass due to the bass frequency roll off that begins gradually at around 100 Hz and then really falls off quickly at 40 Hz.

The 5/4 string voicing button is something that has been added to our amps in order to extend the roll off of the bass frequencies produced by 5-string basses. This is not just simply a bass boost button which works like a graphic equalizer, and it isn't a feature that was conceived by a sales department which decided it would be a good idea to add for marketing purposes. Our button doesn't boost anything. It extends the roll off of the low bass frequencies which don't begin falling rapidly until around 30 Hz. If you are playing a 4-string bass and trying to replicate the classic sound of the 800RB, you will want to have this button out because the 800RB doesn't produce a lot of deep bass. If you are playing a 5-string bass, you will want to have that button pushed in. Some 4-string bassists will actually leave the button pushed in at all times because they want as much low end as they can get. This button solves a particular issue regarding the extended frequencies of 5-string basses, and at the same time, it permits us to bring our heritage with us as we move into the new era of amplification."

http://www.cliffengel.com/interviews/gallien_krueger/
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Kazrog
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754 posts since 24 Oct, 2009

Postby Kazrog; Sun May 20, 2018 8:31 am Re: Frequency Response of Bass Impulses?

Good stuff!
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