Thinking about a bass guitar amp, in particular using a bass reflex cabinet. We all know that the driver becomes more and more unloaded the further you go below the box and port tuning frequency. Seeing the lowest intentional frequency of a bass guitar is 41.2Hz, would it make sense to tune the box at or maybe just a little above this frequency and have a fairly sharp filter to cut everything below this? I imagine the guitar strings being randomly struck while playing would produce subsonic signals that would possibly overload the amplifier and in particular push the speaker unnecessarily seeing it would be nearly unloaded at subsonic.
Would the high pass filter affect the sound much seeing it allows the lowest musical pitch through.
Are bass reflex cabinets considered a good idea for bass guitar or not?
Would the high pass filter affect the sound much seeing it allows the lowest musical pitch through.
Are bass reflex cabinets considered a good idea for bass guitar or not?
Makes perfect sense, for the exact reason you describe.
Some bass (pre)amps have adjustable highpass filters. Bass guitar amp can often be highpassed higher than 41Hz as much of the energy is in the harmonics rather than in the fundamentals, at least in rock music (Standard 2*10" or 4*10" BR cabs for bass guitar amps are often tuned quite a bit higher than 41Hz).
Double basses seem to rely more on the fundamentals, I usually use a 2*10" BR cab for bass guitar and two 1*15" when I play the "bull fiddle".
There's an old thread on some bass forum somewhere about a DIY bass preamp with a fixed 35Hz 12dB HPF followed by an adjustable 35-140Hz HPF, aimed to help acoustic bass players fight feedback and bad acoustic environments at live gigs.
In short: High pass filters are definitely useful in bass amps.
Some bass (pre)amps have adjustable highpass filters. Bass guitar amp can often be highpassed higher than 41Hz as much of the energy is in the harmonics rather than in the fundamentals, at least in rock music (Standard 2*10" or 4*10" BR cabs for bass guitar amps are often tuned quite a bit higher than 41Hz).
Double basses seem to rely more on the fundamentals, I usually use a 2*10" BR cab for bass guitar and two 1*15" when I play the "bull fiddle".
There's an old thread on some bass forum somewhere about a DIY bass preamp with a fixed 35Hz 12dB HPF followed by an adjustable 35-140Hz HPF, aimed to help acoustic bass players fight feedback and bad acoustic environments at live gigs.
In short: High pass filters are definitely useful in bass amps.
A HP filter just below the cabinet Fb (tuning frequency) will improve the low frequency sound of the cabinet, though will reduce the harmonic distortion of the speaker, which may be part of the "sound" preferred by some players.
Slapped strings do have high amplitudes down well below 10Hz, as this example of a 4 string Yamaha bass shows- took me several attempts to catch it:
The driver suspension used in most bass guitar cabinets won't allow much excursion past Xmax (linear excursion), otherwise the cone would launch through the grill
They have been since Dave Nordschow changed the focus of Eden Electronics from PA to bass guitar products back in the 1970's.
As an old friend of Dave's (he built the bass and low mid mold masters for my 1979 all horn PA) it was fun to see Eden bass systems showing up on top group's equipment riders as first choice over Ampeg and SWR, who he also provided bass reflex cabinet designs for.
After selling Eden, Dave continued making improvements, starting "DNA", (David Nordschow Amplification).
Some of the DNA cabinets are using flared ports to reduce turbulence noise, one above and below the tweeter on the right side:
Dave provided a variety of speakers to satisfy most bass players choice, but ported speakers have been a mainstay for decades for those wanting to hear the fundamental notes as well as the harmonics.
Anyway, DIY bass guitar cabinets can be made to fit your exact needs or desires.
Art
Amp Manufacturers do exactly that for the same reason you described. They Just don't advertise their amps as having a HPF in it because some people with the mentality of more is better will be saying "ARE YOU CUTTING BASS FROM MY BASS?!!!!!" old SWR amp are like that, and that is why they are known to blown speakers, there is a reason the PAS speaker were called POS speakers, they blamed the incapability of the speaker to go 300W below 35hz without dying. That is why a moded my Redhead to add a HPF after the master vol control. This is a 4th order Sallen-Key High Pass Butterworth.
For that application TL072 is fine. The SWR redhead bass amp, use the same IC for the tone control circuit.Nice Work
Yes. TL072 is fine there. Many well loved desks of, say the 90s, are full of them with bipolar input NE5534/2 in more noise critical positions. It's the classic fet input audio opamp of its day.
But better is better. And the OPA134 series is better. fwiw I had some of the first samples of these on my desk when searching for a balance between the expensive OPA627 and performance in an ADC front end.
There are arguably better options now but 134 series is a safe bet wrt not being critical wrt layout / stability esp on a two layer PCB.
But I wouldn't suggest dumping TL072 if you have a tube of them in stock.
But better is better. And the OPA134 series is better. fwiw I had some of the first samples of these on my desk when searching for a balance between the expensive OPA627 and performance in an ADC front end.
There are arguably better options now but 134 series is a safe bet wrt not being critical wrt layout / stability esp on a two layer PCB.
But I wouldn't suggest dumping TL072 if you have a tube of them in stock.
"Some op amps have been judged in the wrong applications. The Cmoy headphone amp is just such an example. Typical op amps are made to drive loads of several thousand ohms or higher. Even the more powerful ones are often only rated down to 600 ohms. But that didn’t stop anyone from using these same op amps to drive headphones in the 16 – 300 ohm range. And, not surprisingly, some of them audibly complain at their mistreatment. They simply weren’t designed for such a low impedance load. If you compare overloaded op amp A against overloaded op amp B you may hear some differences in their highly distorted performance. But that’s only because you’re stepping on their tails and making them screech in pain."
-nwavguy - Op Amps: Myths & Facts
http://nwavguy.blogspot.com/2011/08/op-amps-myths-facts.html
The next stage is another TL072 with JFET input and High impedance. Both (2134 and 072) driving that load are happy and performing optimal and so similar that the improvements are negligible and costly.
Not sure of your point here. Obvs don't try to drive too low an impedance from a typical opamp. Let's say limit it to 1K0 including feedback impedance. You generally need a higher current output stage arrangement. But in like for like situation then better than TL07x
(Or eg LF351) is generally available looking at SNR / THD / IMD. But yes - 072 etc will be okay.
Although tbh if driving that from a low impedance source eg OpAmp output, then a lowered voltage nose bipolar input might be better.
(Or eg LF351) is generally available looking at SNR / THD / IMD. But yes - 072 etc will be okay.
Although tbh if driving that from a low impedance source eg OpAmp output, then a lowered voltage nose bipolar input might be better.
I roll my eyes, big time, at the CMoy "design" : wrong part wrong design wrong supply.
Yet it became incredibly popular.
Guess simplicity beats any other consideration 🙄
Oh well.
would want to tune below 40 hz
to reduce unloading.
higher tuning just makes system unload that much faster.
Rarely achievable with pro sound drivers.
45 to 55 Hz typical for 15"
But possible if low Fs driver is found.
Assuming the reflex is usually 3 to 5 Hz
above/below driver Fs.
Fs in the 30 's get close to 18"
why as mentioned over excursion filter or steep 4th order highpass
to reduce unloading.
to reduce unloading.
higher tuning just makes system unload that much faster.
Rarely achievable with pro sound drivers.
45 to 55 Hz typical for 15"
But possible if low Fs driver is found.
Assuming the reflex is usually 3 to 5 Hz
above/below driver Fs.
Fs in the 30 's get close to 18"
why as mentioned over excursion filter or steep 4th order highpass
to reduce unloading.
use a socket. I think any dual opamp will be fine. Use high quality if you desire, make it boutique.
funny how the CMOY fans hate the opamp made for headphones the JRC4556, The current is double than opa2134. I think that what they like is that laid back coloration produced by making the opamp cry.
I have looked at HPFs for bass and as said earlier, most of the round of a bass guitar is from the second harmonic and some of the best bass cabs made tune much higher than a Low E. Even so it is wise to tame the mush below the fundamental. You will not hear the effect of a 4th order (24dB/octave) filter at 35HZ, and I tend to use 40 Hz. Of course, as also said, almost every bass amp maker builds in an HPF. It will usually be much lower than 35Hz.
F Deck, probably makes the most well known HPF designer, uses 35Hz as his starting point on a tuneable HPF
F Deck, probably makes the most well known HPF designer, uses 35Hz as his starting point on a tuneable HPF