Bass Guitar Drivers

Sealed, vented, bandpass, etc.

Bass Guitar Drivers

Postby dlhughes001 » Wed Jan 26, 2011 5:43 pm

I'm puzzled by something...
Bass guitar cabinets are expected to reproduce frequencies down to 42 Hz, in the case of four-string basses, and well below that for 5 and 6-string basses. Yet when I look up the specs on, for instance, Eminence bass guitar drivers, their F3 is generally well above that, and the suggested vented cabinet designs begin to exhibit a system rolloff often even higher than the F3 of the driver. I was just looking at one particular Eminence driver whose F3 was at 66 Hz, yet this is a popular bass guitar driver. The suggested vented cabinet design for this driver exhibits a frequency response curve that's about -18 dB at 40 Hz., and the -3 dB point is above 60 Hz.
I'm having a difficult time figuring out how this can sound good as a bass guitar speaker system. Is there something 'psychoacoustic' involved here....or what? Shouldn't I shoot for a response curve that's down no more than 3 dB at the lowest frequency I want to produce thru my cabinet?
I have a combo bass amp which I've 'reverse-engineered' to find the cabinet's port tuning, and come up with about 55 Hz, and this with a 15" driver in it. Yet, it sounds very solid right on down to the low 'E' (42 Hz). How is this possible?
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Re: Bass Guitar Drivers

Postby clist » Thu Jan 27, 2011 4:19 pm

For stage gear it all comes down to efficiency, size and cost.

In the real rock & Roll world it is often a war over loudness.
Electric guitar and drums have a distinct advantage for getting loud with little input.
Typical lead electric guitar can take 30 watts to 100watts and over power the rest of the stage volume down to 100Hz after which it is no longer audible.
To get to the same level at 40Hz will require a van load of power amps and very large full range and sub woofers.

If you get 60Hz (flat) out of a bass guitar rig it will cost a fortune and will not fit on a night club stage.

A friend had a “HartkeTransporter”
http://www.americanmusical.com/Item--i-HAR-410TP-LIST

They claim it is good from 40Hz to 4kHz.
I measured it.
The lowest you could hear it was 80Hz and it never went above 2kHz.

All he cared about was the weight and cost and if he could figure out what key he was in.

In the end you need to be ZZ Top to afford a bass stage rig that goes down to 40Hz.
:(
Too Tall
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Re: Bass Guitar Drivers

Postby dlhughes001 » Thu Jan 27, 2011 7:44 pm

Oh, I'm not talking about BUYING such a rig...I'm just trying to figure out how a bass cab that is port-tuned only down to about 60 Hz can seem to crank out that 42 Hz low 'E'. I mean, you can hear it very well, but according to the tuning of the cabinet, it ain't supposed to be there.
As an experiment, I built a 1x12" cabinet. 1.5 cu. ft.. with a 3" port tuning it at the (hi-fi) driver's F3 of 40 Hz. It does indeed work big-time at 42 Hz, without a doubt...but somehow it lacks any real 'punch' that you get at 60-80 Hz in the usual bass cab. I'm just wondering if there's not something psychoacoustic going on with these 60-Hz-tuned cabinets that only makes you THINK you can hear that 42 Hz fundamental. Maybe I should just get hold of one of those drivers and build a box tuned to its F3 and see how that sounds to my ears.
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Re: Bass Guitar Drivers

Postby clist » Thu Jan 27, 2011 9:45 pm

I'm just wondering if there's not something psychoacoustic going on with these 60-Hz-tuned cabinets that only makes you THINK you can hear that 42 Hz fundamental.

The feeling of punch where you feel it in your chest only happens in the 80Hz to 60Hz region.
Below that it is more like an earth quake.

If you feed a speaker a tone below tuning it may make a tone double the frequency of the tone you played.
This is called "Doubling". It can easily fool you because your brain fills in the lower tone.

Use an RTA analyzer. There are several free programs around. What you will need is an analyzer mic (Behringer ECM8000 for about $40)
Too Tall
Curtis H. List
Bridgeport, Mich.
I.A.T.S.E. Local # 274 (Gold Card)
Lansing, Mich. local

Independent Live Sound Engineer (and I'm Tall Too!)
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Re: Bass Guitar Drivers

Postby audioaficionado » Tue Jan 31, 2017 5:06 am

Even if they can't produce the fundamental note, humans can reconstruct the fundamental note in their brains even though they didn't really hear it. Voice recognition on a telephone is a good example of this ability.
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