Hey

The reason is to mimic a guitar speaker, you can see earlier posts comaring the response of a creamback driver and my filter

Oddly once implemented the fre isn't the same with v poor bass, will have to do some fiddling!

Two things to bear in mind:
1. The response plot on the datasheet is the response in an anechoic chamber. In a cabinet, and because the Qts value is high, there will be a peak in the 70-100Hz region. Thiele-Small parameters are rarely specified on lead-guitar speakers.
2. A guitar pickup has a rising response in the lowest half-octave. Output from the pickup is proportion to the size of the moving magnetic material and its velocity.

 

Two things to bear in mind:
1. The response plot on the datasheet is the response in an anechoic chamber. In a cabinet, and because the Qts value is high, there will be a peak in the 70-100Hz region. Thiele-Small parameters are rarely specified on lead-guitar speakers.
2. A guitar pickup has a rising response in the lowest half-octave. Output from the pickup is proportion to the size of the moving magnetic material and its velocity.

Ooo, thanks Ian, so i might not want an exact copy of the cream back frq response, but rather a bit more low end?

Would be smart of me to get a good ref mic and doa sweep on my actual cabinet I guess

 

Make the low end a 2nd order high-pass Chebyshev with a peak of about 3dB. A speaker in a closed box produces a 2nd order roll off. (4th order for a bass reflex cabinet)

 

Old speaker systems that produced "one-note-bass" usually resonated with a peak between 70Hz to 100Hz.
The old vacuum tube amplifiers for electric guitars did not have the extremely low output impedance of a modern solid state amplifier that damps speaker resonances.

 

Old speaker systems that produced "one-note-bass" usually resonated with a peak between 70Hz to 100Hz.
The old vacuum tube amplifiers for electric guitars did not have the extremely low output impedance of a modern solid state amplifier that damps speaker resonances.

No shortage of new speaker systems that produce "one-note bass"! Just listen as they drive past!

 

Make the low end a 2nd order high-pass Chebyshev with a peak of about 3dB. A speaker in a closed box produces a 2nd order roll off. (4th order for a bass reflex cabinet)

Hey Ian,

So, did as suggested and in LT spice looked great:



Into KiCad (just the high end bit shown):

]

So for some reason that side of the opamp is oscillating rail to rail at around 3.7kHz which is about that high-end peak on the freq response. An un-damped resonance I'm guessing?

Wondering if my component placement is to blame? traces too long?

P

 

Try it without C20

 

Try it without C20

Yeah, tried that no luck. Does slightly alter the oscillation freq though.

 

What is driving R24? It need to be a low impedance, such as an op-amp output.
It could also be coupling through the power supply, check your divider that forms the half-supply reference.

 

so R24 comes straight from Pin 1 of the other half of the opamp. The power supply is a +/-17V,

the whole section of the circuit is:

 

well solved it by adding 22k resistor to ground from the junction of r26, r24 and c19

i was think to try and bleed a little signal to ground before going into the non inverting input.....not sure that makes sense technically

 

hi pd,
You have reduced the HF 'hump' with 22k
E

Note: the loss of Gain. ~+3db down to ~-3dB.