I did a little digging on this and while Shure shows a pretty flat graph from 22Hz-20kHz for this amp at 1W 6ohms, I get NOTHING out of my 4 x Aura Pros near 20 Hz and need to configure them up to about 32 Hz to feel them on my rig. I have always assumed that was because of a transducer limitation.
If you watch the following video it shows that the Aura Pros do in fact work well at 20 Hz assuming that the guy really is running a 20Hz signal that he says he is running to the transducers he is testing.
So while I feel like I'm getting good effects out of my transducers running in the 32-70Hz range, it does appear that my DIY amplifier is a weak link.
Good to know.
When I built that amp, I was playing and mostly curious if it would even work. I am happy with the effects I'm getting from it, but I did have to adjust the frequencies higher than I probably would have needed with a different amp.
What I learned from the Tactile thread is that it's important to have different effects use different frequencies when a single transducer is producing multiple effects. Even then a single transducer can be saturated with one signal masking others. So having a wider frequency range available can only help make each signal stand out more. Having dedicated transducers per effect is a more ideal solution.
So the bottom line is that this inexpensive Class D amplifier is not going to give you the full range of a transducer and is not ideal. It may be enough depending on your needs, but it appears that it actually does have low frequency limitations.
Guys, do note that when testing tones it may not be, just what you expect....
Here is a rather detailed example of a 22Hz Tone being generated with low to moderate volume.
The curved line is a 80Hz Crossover using a 36dB drop/curve.
Pay attention to how wide the grid is with different frequencies, that is the felt bandwidth energy. Notice how wide 20Hz is compared to 50Hz.
Now onto the example. So with this test we see that much more than just 22Hz as a center value is being generated. Both lower and higher frequencies are also included. Gain levels are important to consider as is what the output abilities with lower frequencies a unit may have. It is here we find wattage and weight in pistons or the power in the magnets used on the transducers are relevant.
So lets just increase the gain level to see what happens.
80Hz crossover highlighted. As we increase the gain all the Hz are going to become higher in dB. Therefore a transducer that only delivers good felt energy @35Hz or peaks at a common @40Hz. Well we can see it is containing 40Hz energy at just -3dB so will be part of the combined sensation they are feeling.
What this means is on a unit that will not properly generate high enough energy with the lower frequencies the user is going to feel the frequencies that are closer to its (good energy output).
Cranking the volume will not bring much additional increase in the Hz felt regards lower frequencies now being better felt (unit dependent) but it will likely on a lot of budget units just make its peak output frequencies for that units "output character" even more noticeable.
I would speculate while not scientific or accurate, this highlighted in red and in many cases something more like the lime green. This would be more like what a user would feel from a 22Hz tone if the volume was cranked. Lots of people have difficulty in determining different frequencies to feeling the same frequency with higher/lower gain as it's not always that easy to tell based on the unit used and the gain level and tone being tested.
When you look at this also take note in how much is not included in those boxes. This highlights just how much most users of budget tactile are missing from their immersion or indeed even the ability to place and enjoy effects with unique felt sensations in the vibes from the lowest frequencies that cannot be properly replicated or replaced with other frequencies own felt sensations.
Unique Vibes & Immersive Sensations
With capable hardware, did you know that approx 12-15Hz generates vibes that will make your face/cheeks/ears, resonate and shake. This can be used on G-Force based effects or high speed to replicate engine strain shaking the whole cars body/chassis. Its rather awesome if well handled by sufficent hardware and wattage. Also that 19Hz is the resonante frequency of the human eye, with ability to make even your eyelids vibrate move. So we can use these body responses to be contained within our effects creation to offer quite unique (user-defined) felt sensations that we cant come close to bringing to the immersion with the typical or budget/common tactile. Best immersion is not always about having 4,6 or 8 units. It matters greatly what the units used can achieve in the output of all bass frequencies.
True Low Bass Or Additional Harmonics?
The user may think they are feeling 22Hz and yes on a unit that can generate good energy from 5Hz like the large BK units. Then what they feel with a 22Hz tone is going to be VERY different to a small or common unit with limited or little response. As with a large BK unit and a decent amp they will indeed feel all the lower frequencies below the center value 22Hz with good energy as intended. Not feeling some Hz above the fundamental frequency used.
But hold On......
We are not quite done yet as a common thing people will do is crank the crap out of the volume. So what happens when we do this, just that the dB increases and the additional frequencies stay the same?
Well no, as we increase the energy we increase the harmonics also being contained or that will be felt.
Here is an example with the audio cranked with the same tone. Notice the huge difference
Now we see that beyond the crossover point. Assuming a typical user has no crossover in place. Even from 50Hz to beyond 200Hz have high dB. Okay but what the user feels will vary based on what the character output and their units limits are in its highest felt frequencies. If it was an exciter that 22Hz tone would have energy even to its 10th harmonic at 220Hz. On a unit that only can manage 100Hz then the user will feel it as a buzz contained in with the other Hz.
Suitable Created Effects
This is why it is important in building effects to understand that the same effects with tones used on one unit compared to another much more capable unit will vary a lot in what each user feels. Trying to build effects on high-end hardware for someone to then use those effects on budget hardware are not going to get anything like the intended felt sensations.
For budget tactile the user should focus on making effects that work well within that units peak frequency range. Its just that this differs a lot between pro hardware and budget.
Do keep in mind that with the example 80Hz crossover only the frequencies to the left of the crossover would be felt regardless in what is being generated. So using a crossover can vary quite a lot what Hz are felt on a unit to not using one.
Although to be fair it becomes more of a tool to use if you have units that are more audible like Clark Synthesis TST models or if using exciters. With no crossover control they will make much more audible noise due to generated harmonics.
So for big units like large BK we want to focus their output on the low Hz and not muddy the low bass with additional harmonics. This also can bring more control or help reduce clipping and with them using a crossover can be an advantage in limiting bottoming and finding peak performance from them.
Bottom line is that if you have basic tactile then you may just get away with a basic amp but really the users should consider buying hardware that lets them upgrade easily or enjoy the more capable hardware if purchased at a later time. So I think holding off for a better or getting a decent amp is a good start to build on, rather than these budget options that are going to be limited.
Keep in perspective, it's not just about more wattage and power, its the ability to make full use of the 1-200Hz bass range that we can then go about making much, much more immersive effects and for hardware that is capable of producing these...
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