When I started getting in diy audio, especially in car diy audio. I was thinking why my powerful subwoofer cand give me a chest kick at all but those very cheap subs from sony, pioneers etc can??
I believe is because of mms! Even if the motor force is high, if the mms is over or at 200gr of a 12" driver, you can't feel the midbass! the cone will not accelerate fast enough because of inertia! A high bl force will reach a high speed cone but won't accelerate fast enough.
I come with this calculation (Bl÷mss) the = needs to be higher than 0.1 for midbass kick feel.(Don't ask me where i found this 😂) 20bl÷200mm=0.1 but even if the equal is 0.1, the mms is too high for a 12, this more calculates if the bl is high enough.
The mms needs to be under 200 for a 12" (150) above 200 for 15" and under 100 for 10" and so on.
If you look at the specs of pa drivers and those cheap *** subs, you can see exactly this(not all of them of course) makes sense.
Basically you need midbass mms with high enough vas to reach 30hz.
Mms is the king.
I believe is because of mms! Even if the motor force is high, if the mms is over or at 200gr of a 12" driver, you can't feel the midbass! the cone will not accelerate fast enough because of inertia! A high bl force will reach a high speed cone but won't accelerate fast enough.
I come with this calculation (Bl÷mss) the = needs to be higher than 0.1 for midbass kick feel.(Don't ask me where i found this 😂) 20bl÷200mm=0.1 but even if the equal is 0.1, the mms is too high for a 12, this more calculates if the bl is high enough.
The mms needs to be under 200 for a 12" (150) above 200 for 15" and under 100 for 10" and so on.
If you look at the specs of pa drivers and those cheap *** subs, you can see exactly this(not all of them of course) makes sense.
Basically you need midbass mms with high enough vas to reach 30hz.
Mms is the king.
You don't need high Vas to reach 30 Hz. If all else equal, higher Vas means you need larger box to reach low (without EQ).
But of course if all else are equal, higher Vas means lower Mms.
But of course if all else are equal, higher Vas means lower Mms.
Last edited:
IF this is true then this will be reflected in GD. The acceleration to peak spl is not an unfamiliar aspect.
It is an interesting question that almost inevitably leads to the "fast bass" rabbit-hole. Most things I've read place chest kick around 60-80 Hz, which aligns with a likely strong response peak in a cheap sub to give the impression of strong bass using a cheap driver in a ported box. That cheap sub may also be run higher up in frequency giving additional power in the 100-200 Hz range that is a crucial range for drums.
When comparing drivers for ability to accelerate the cone, you need to also consider Re. A motor with more BL might also have higher Re and thus draw less current for a given voltage input.
The acceleration of the cone for 1W of input power works out to BL / (Re^0.5 * Mms) . Equivalently, many folks use BL^2 / (Re * Mms) as a way to compare drivers in this way. It is an academic argument since it doesn't consider impedance, which varies with enclosure design and frequency.
When comparing drivers for ability to accelerate the cone, you need to also consider Re. A motor with more BL might also have higher Re and thus draw less current for a given voltage input.
The acceleration of the cone for 1W of input power works out to BL / (Re^0.5 * Mms) . Equivalently, many folks use BL^2 / (Re * Mms) as a way to compare drivers in this way. It is an academic argument since it doesn't consider impedance, which varies with enclosure design and frequency.
It also doesn't include driver radiating area. Of course a larger cone works better, but it has more mass obviously.
Just for curiosity, the worst sub driver that I heard in regards of chest slam was a Scan-Speak 26W/4558T00. It's sound had an irritating soft attack with an almost non-existent slam/jump factor. At least in an 50 l vented box that was tuned to about driver Fs. No matter how it was EQ-ed.
For me looks like a subwoofer, the fs is very low and the vas is 90L. The motor force seems kinda week for the xmax, i think is a small diameter coil and thats why has more xmax in comparation with bl and qts. Use a 90 l box tunned lower.
Heck a 6.5" driver with xmax of 5mm can have a bl of 7
A speaker only needs to be able to 'accelerate' fast enough to reproduce the frequency at the spl for which it is used. Full stop.
Mms could be 10g or 1000g; Bl could be 1 or 30; acceleration is not a term often used to describe drive units.
A 21" driver has a cone mass of about 400g but the response is typically only a few dB down at 1kHz - way above midbass...
The only thing which really matters for a tactile response to sound is spl (at some magic frequency perhaps), no matter how it is achieved.
Without measuring the frequency responses of the drivers which do or do not have 'kick', your suppositions might lead you down an incorrect path.
Mms could be 10g or 1000g; Bl could be 1 or 30; acceleration is not a term often used to describe drive units.
A 21" driver has a cone mass of about 400g but the response is typically only a few dB down at 1kHz - way above midbass...
The only thing which really matters for a tactile response to sound is spl (at some magic frequency perhaps), no matter how it is achieved.
Without measuring the frequency responses of the drivers which do or do not have 'kick', your suppositions might lead you down an incorrect path.
Last edited:
Low frequencies in abundance make mud. The balance of the surrounding spectrum shouldn't be underestimated.
I don't know what to say, i believe that you need instant fast acceleration to "slap" the air that makes you feel the midbass, you can get that easy with low inertia, light cone.
I also believe that if you want kick from a heavy cone subwoofer you need a substantial more bl than it is possible, like a logarithmic increase.
I had some powerful multiple, subwoofers in my car, it can get so loud that makes your vision blurred! Literally (At midass frequencies)
But, no, or just little midbass kick.
Sports cars are built like that isn't it? 🙂 a heavy car needs a lot more power to be as fast as a light car
Google 'Fourier analysis' and read up on it until you genuinely understand it's implications compared with your beliefs.
It might also be helpful if you could explain exactly what 'kick' or 'slap are to your ears/body, and where in the frequency spectrum you believe it occurs.
You do realise that it's the midrange and tweeter that gives a waveform a steep rise time, right? (Back to Fourier...).
What do you mean by this in terms of the speaker's output and/or frequency response? What is actually missing with this driver where others succeed?
Same SPL and frequency response like with a driver that can kick but the 26W/4558 can't kick. If you hear it, it's pretty obvious on all SPL. What is missing is the realistic "transient attack" (the feel in your chest), you hear the bass but can't feel it. Imagine a live drum sound that can't be felt just heard, pretty irritating IMO. But probably there are many similar drivers out there.
This increases the output level where everything needs to try harder to keep up. Just trying to say that this isn't the key to the issue.
"you hear the bass but can't feel it" - I could argue that the less Sd or Terminus Csa there is, the less tactile the bass is... I've read material that suggest such a thing. I wouldn't be able to explain why though
One of my (and for many) favourite small woofer, the Faital Pro 5FE120 can kick hard (but of course limited in max SPL), the 26W is like nailing with a pillow in your hand instead of a hammer.
5FE120 EBP = 127
26W/4558 EBP = 64
Last edited: