SB Acoustic 3″ SB10PGC21-4 Sealed 3rd order Butterworth Plan

[WibuSquire]

Got this little speaker here from discount. Since I need it to be portable for my office, I planned to make it small. (probably around 1.9 ~ 2 liters, sealed with QTC around 1.15~1.16, probably a bit less with additional stuffings). I don't expect bass from this because I planned to get a woofer/subwoofer in the future & probably build 2.1 or WAW system (but that's another topic)

I do need to tame the bump around 140-150 hz after some testing with WinISD. so I will put a capacitor in series for a bit of highpass.

Now at my place, the BP capacitor available here r only 100uf, 220uf, 330uf & 470uf. although not ideal. which one should I buy?

Also SB acoustic did have the formula to decide the capacitor value.....but I only know basic math, tried to search & learn it from google with no avail.

Thank you in advance.

 

[stv]

Hi WibuSquire,
here is a quick Hornresp Simulation with 3 litres and a 800 uF series cap (by paralleling 470 and 330 uF).

even higher cap values will give a more rounded (lower Q) resonance peak.

If you make the enclosure smaller and / or reduce the capacitance there will be a stronger peak at the resonance, just above lower rolloff.
here is 2 litres with 470 uF:



EDIT 1: By the way you can also make a bipolar cap by connecting two polarized electrolytics in series with the positive leads connected. The resulting capacitance is half the value of one single ploarized electrolytics. Thus connecting two 1500 uF caps gives 750 uF.

EDIT 2: just for fun, here is a bass reflex tuning with high pass series cap:

I know, you don't need that, but it's still interesting.
group delay is high at resonance (35 ms) and Xmax limit is already exceeded with half a watt at 40 Hz.

 

[WibuSquire]

Thank you very much STV. also the included graph r really helpful

noted. then that means I can just combine the capacitors. in paralel.

Also ah yess, the 5th order bass reflex LoL

I'm starting to order the material for the box . so now I'm gonna decide the volume as well (Ideal size would be 2 liter, but I can crammed 3 liter as well)

so 3 liters with 800uf capacitor should do I think

 

[stv]

Ideal size would be 2 liter

It should not make that much difference, also considering there will probably be an active 2.1 filter, with crossover frequency probably above 100 Hz.

 

[WibuSquire]

I think I manage to found how to decide the capacitor value. CMIIW, if I Input that SB Acoustic formula on online calculator + Farad to microfarad conversion I got 967.76uf. I guess its doable (hopefully)

if I just go buy some couple of 470uf bp Capacitor & parallels it, I should able to get about 940uf which is close enough

 

[WibuSquire]

necro the thread because I need to reconfirm

the site basically said that the Power handling for this speaker is 20* watt RMS (*you have to use 2nd order high pass filter at 200 hz for the speaker to be able to handle that without over excursion)

now if I don't use 200hz highpass filter, 20 watt is too much for the driver (2 watt is probably more tolerable)

Does that means this speaker is strictly for FAST/WAW setup with common sealed box?

 

[cowanaudio]

A line array would be my first choice for a driver like this.