deep output from very small drivers and enclosure?

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#21
Yes no point heading for subterranean cutoff frequencies unless you have good acoustic efficiency to generate enough sound pressure for it to be useful.... or even audible (No 3" driver in any kind of enclosure will give you that).

Have a look at what's sensible to aim for:

Equal-loudness_contours

You are up against the laws of physics, and the laws of physics will win 😉
 
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#28
botnet said:
winforce, I was thinking home theatre; was looking to get something great out of this little driver and was hoping that the 3d-printer would give me some construction advantage by unlocking any complex shape.
Click to expand...

When thinking of geometric gymnastics for a driver enclosure, it's always good to think in wavelengths. Things much less in path length or wall dimension aren't going to do much (beyond the limitations of air volumes and cone excursion) at less than about 1/4 wavelength. At 20Hz, that's 14ft. That's not going to be small, compared to a 3" driver.
 
#29
bwaslo said:
When thinking of geometric gymnastics for a driver enclosure, it's always good to think in wavelengths. Things much less in path length or wall dimension aren't going to do much (beyond the limitations of air volumes and cone excursion) at less than about 1/4 wavelength. At 20Hz, that's 14ft. That's not going to be small, compared to a 3" driver.
Click to expand...

am I understanding correctly that both front and rear horns must be at least 14ft to get some 20hz gain?
 
#30
I have similar projects going here atm. Just got 4x Tangband w4-992s, trying to get satisfying results = lots of bass from small drivers, reasonable lower cut limit, while keeping enclosure size tolerable.
So I made a dual bass reflex: 12 litres, tuned to 50Hz. This gave pretty nice results, flat response and hmm, nice spl levels too. I also tested 60Hz tuning but it was too one noteish (peaky response around 60-70Hz), actually it was horrible.
I also simulated 6th bandpass giving very good spl beetween 45-80Hz but 15 litres of volume for single 4" driver is just too much for my taste. Tapped horn would be even larger.. maybe I will give it a try anyway.

Looks like passive radiator is the way to go, if small size + big sound is the main criteria.
Most bluetooth speakers (jbl xtreme etc) are using this method.

3" drivers are even more interesting.. 🙂
How about smallest sub/biggest SPL contest?
You get 5 extra points for every inch the driver is smaller than another. 10 extra point for response flatness of 10Hz (flat beetween 50-70Hz = 20 points, +/-2dB tolerance). 10extra points / 0.5 litres of enclosure volume (smaller the better).
 
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#31
12 liters in kinda small, but the TB 6,5" subwoofer + passive radiators will work in 10 liter enclosure with good results. I pushed the low end with miniDSP and sounds quite good.

The 5" from TB might be the smallest I could imagine as a subwoofer. When going smaller you need to have some gimmicks to get the low notes. In those bt speakers DSP and psychoacoustics are the secret ingredient.
 
#33
GM said:
Actually, to get gain down to 20 Hz you have to design to ~16.2 Hz, ~14 ft only gets you ~ -3 dB/20 Hz. If you look at the TH I simmed, its path-length is tuned a 1/2 octave below 20 Hz to get full gain.

GM
Click to expand...

@GM thanks for the simulation, i’m trying to interpret the text file - which parameter is horn length? or is the intent to plug the values into hornresp to understand the dimensions?
 
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