Do you prefer rear ported, front ported cabs or sealed bass cabs?

[Akiyama]

Don’t believe everything AI tells you… a well designed passive radiator cabinet CAN sound very good, but in general it won’t have any more low frequency extension than a well designed ported cabinet. It’s another way of doing the same thing as a ported cabinet.

I came across this article today. (No offense meant to anyone who uses AI).

AI generated list of summer reading is full of fake books

 

[tubedude]

Perception is a powerful mechanism.

That's why it's called psychoacoustics. If it's perceived as good, it is good.

 

[agedhorse]

That's why it's called psychoacoustics. If it's perceived as good, it is good.

Even if inaccurate.

 

[Akiyama]

I bow to your expertise in these matters. Your statements and graphs are no doubt accurate. We all have harmonics present, after all that's what delineates tone, the harmonic structure. All i can say is the low B on both my basses rings out loud and low. Very much lower than the octave above. It may be mainly harmonics generated by the amp and speaker, but i can't tell. It certainly gigs just fine with a 6er.
With my sine wave generator at 31 Hz, it still pumps out with no sense of loss. Perhaps room reinforcement and vibration (and there is a fair amount in my shop) are carrying the day. As in most anything involving the senses, test equipment can measure much greater differences than the ear can readily hear.
Few songs really use the low B. The 6th. string is more valuable in avoiding stretches that require much hand repositioning.

Have you tried measuring an open B in your room using a dB meter? That might be clue if there are room acoustic effects.

Also, the low frequencies are picked up by mechanoreceptors in the body, notably augmenting the lower sensitivity that the ears have for sub-100Hz. Accounting for energy differences, mechanoreceptors are approximately 40–60 dB more sensitive to low-frequency vibrations (sub-100 Hz) than the auditory system, especially at lower frequencies like 20 Hz, where auditory sensitivity declines sharply. The mechanoreceptors input from sound/music is processed in different areas of the brain (more "primitive" and fight/flight areas) than how sounds/music is processed through the auditory system. Though there is some overlap with the ossicles vibrating and resonance in the skull (picked up by mechanoreceptors). The mechanoreceptors are processed at a sub/pre-conscious level, at least initially. The sensations can be brought to the attention of the conscious mind. For example, you may not hear an earthquake but your body senses it (mechanoreceptors) and reacts quickly, usually prompting a mild squat to prepare for escape from a sub/pre-consciously perceived danger, an evolutionary defense mechanism. Shortly thereafter, you then understand that you experienced an earthquake. Mechanoreceptors are not easily fooled or inaccurate. That may be what you are experiencing with your set up and your perception of the lower frequencies that fall outside of the theoretical range of the frequency response rating of the cabinet.

 

[agedhorse]

Have you tried measuring an open B in your room using a dB meter? That might be clue if there are room acoustic effects.

Also, the low frequencies are picked up by mechanoreceptors in the body, notably augmenting the lower sensitivity that the ears have for sub-100Hz. Accounting for energy differences, mechanoreceptors are approximately 40–60 dB more sensitive to low-frequency vibrations (sub-100 Hz) than the auditory system, especially at lower frequencies like 20 Hz, where auditory sensitivity declines sharply. The mechanoreceptors input from sound/music is processed in different areas of the brain (more "primitive" and fight/flight areas) than how sounds/music is processed through the auditory system. Though there is some overlap with the ossicles vibrating and resonance in the skull (picked up by mechanoreceptors). The mechanoreceptors are processed at a sub/pre-conscious level, at least initially. The sensations can be brought to the attention of the conscious mind. For example, you may not hear an earthquake but your body senses it (mechanoreceptors) and reacts quickly, usually prompting a mild squat to prepare for escape from a sub/pre-consciously perceived danger, an evolutionary defense mechanism. Shortly thereafter, you then understand that you experienced an earthquake. Mechanoreceptors are not easily fooled or inaccurate. That may be what you are experiencing with your set up and your perception of the lower frequencies that fall outside of the theoretical range of the frequency response rating of the cabinet.

Nicely said!

This is exactly WHY perception is so important to understand as an amp/cabinet designer. I want to be sure that I do what I can to enhance the perception beyond what is acoustically/auditorily possible at every opportunity.

 

[Akiyama]

Nicely said!

This is exactly WHY perception is so important to understand as an amp/cabinet designer. I want to be sure that I do what I can to enhance the perception beyond what is acoustically/auditorily possible at every opportunity.

Thanks for the compliment!

Are you familiar with Sean Olive's research regarding speakers and headphones and listening preferences? Granted, his research is not directly related to cabinet design, especially in the context of bass cabinets but it has some interesting findings.

Sean Olive blog

It is also interesting, at least to me, how differently-trained musicians (and non-musicians) hear/perceive. Here is another article that I found interesting:

Auditory Profiles of Classical, Jazz, and Rock Musicians: Genre-Specific Sensitivity to Musical Sound Features

I hope you don't mind me post-bombing you with articles regarding this area of science. Please let me know if I should back off.

 

[agedhorse]

Thanks for the compliment!

Are you familiar with Sean Olive's research regarding speakers and headphones and listening preferences? Granted, his research is not directly related to cabinet design, especially in the context of bass cabinets but it has some interesting findings.

View attachment 7234332

Sean Olive blog

It is also interesting, at least to me, how differently-trained musicians (and non-musicians) hear/perceive. Here is another article that I found interesting:

Auditory Profiles of Classical, Jazz, and Rock Musicians: Genre-Specific Sensitivity to Musical Sound Features

I hope you don't mind me post-bombing you with articles regarding this area of science. Please let me know if I should back off.

Not specifically, but I have extensive first hand experience with audience perceptions of sound quality as it relates to mixes. There are certain elements that are common to most people with regard to levels and tonal balance, of course all of this is subjective but it can be used to gain the impression of "better performance".

 

[seamonkey]

Thanks for the compliment!

Are you familiar with Sean Olive's research regarding speakers and headphones and listening preferences? Granted, his research is not directly related to cabinet design, especially in the context of bass cabinets but it has some interesting findings.

View attachment 7234332

Sean Olive blog

It is also interesting, at least to me, how differently-trained musicians (and non-musicians) hear/perceive. Here is another article that I found interesting:

Auditory Profiles of Classical, Jazz, and Rock Musicians: Genre-Specific Sensitivity to Musical Sound Features

I hope you don't mind me post-bombing you with articles regarding this area of science. Please let me know if I should back off.

Sean Olive is a legend at Harman

Check out https://patents.google.com/patent/US8311232B2/en
Used by Harman in their product development methodologies for their high end pro audio.
Harman often publishes Spinorama measurements.

 

[Ol Sparky]

I favor Chianti over port.

 

[Akiyama]

Sean Olive is a legend at Harman

Check out https://patents.google.com/patent/US8311232B2/en
Used by Harman in their product development methodologies for their high end pro audio.
Harman often publishes Spinorama measurements.

“Finally, there is evidence that equalizing the loudspeaker's sound power response to be flat results in lower preference ratings if the loudspeaker does not have constant (flat) directivity and the listener is not in a reverberant room. Most consumer loudspeakers do not have constant directivity. Typically, the directivity rises with increasing frequency. Equalizing the sound power of these loudspeakers to be flat will be done at the expense of the on-axis response, which will be too bright from the resulting upward spectral tilt at higher frequencies. This can lead to lower preference ratings. Finally, typical domestic listening rooms are not reverberant. On average, they have RT60 values of around 0.4 second.“

Interesting. Great find. This also gives context to the flat vs baked-in eq of amps/cabs. Neither is right or wrong. This confirms that environmental acoustics play a significant role and theoretical flat is not usually flat. EQ the room first then set controls for flat, if that is one’s purpose. I am pretty much a baked-in tone and signal chain synergy (bass/pedals/amp all together) person. I have no cares if my output is “flat” or giving the “true sound” of my bass. Different strokes…

 

[JimiLL]

So what are the generalities of different port designs? Why are some chosen vs others? How is a shelf port different from a “normal” port?

 

[fdeck]

So what are the generalities of different port designs? Why are some chosen vs others? How is a shelf port different from a “normal” port?

I'm not a pro designer, but have studied the physics a bit. A lot boils down to practicality. The generality is that all of the port types function in the same way. At very low signal levels, the most important design parameter is the tuning frequency. This in turn is a function of the volume of air in the port, the overall frontal area, and the volume of the box. Two designs with the same tuning frequency will behave the same in the small-signal regime. The response curves shown by the popular modeling software are based on the small-signal model as well

This is what I refer to as the "small signal approximation." Everything is approximate, and one way of thinking about design is to take care of the simplest approximations first, then figure out how those approximations break down in real life, and refine the design accordingly. Keep doing that until you're satisfied or run out of plywood.

Where the small-signal approximation breaks down is with... drum roll... big signals. At higher signal levels, the air moving in and out in the port interacts with the edges of the openings, and can produce turbulence, which is an audible form of distortion. Making the port physically larger reduces the average air speed in the port, which reduces turbulence. Other measures help, such as smoothing the edges, which is why many ports are flared.

At very high signals and low frequencies, I've read about the air motion at the throat of the port imposing asymmetrical forces on the driver, causing cone damage. Designers have talked about symmetrical designs that avoid this.

But larger ports are also longer, for a giving tuning frequency, and end up exceeding the available space in the box. This is where the designer has to make tradeoffs, and may even scrap a design idea if they can't find the right compromise.

As for the shape and number of ports, because all ports function the same way, the main consideration is practicality. In my DIY designs, shelf ports are a way to use the off-cuts that inevitably pile up during the project, avoiding the expense of yet one more component. On the other hand, a molded tube port might reduce assembly costs in a commercial speaker. This is an example where a DIY'er might have different constraints than a commercial maker. I try to avoid building speakers with a $95 driver and $195 worth of hardware, when my gigging conditions don't require it.

 

[agedhorse]

Very much for practical considerations regarding location and shape.