A speaker box optimized for SB Acoustic SB20FRPC30-8 requires al least 27 Liters for a sealed enclosure (between 27 and 45 Liters) and if ported requires a more volumed box than a sealed box. Either enclosure will work. However, if you want to go for bass reflex you need around 100 liters of volume. As a result, if you prefer smaller enclosures go for sealed. You can also fill it up with damping material to improve the sound.
Hey I am looking into making something similar with a 25L sealed enclosure I have laying around. What kind of sound deadening material would you recommend to line the inside of the enclosure with?
The website I intend to buy the speakers from also sells MDM panels, so that's certainly an option. I also have glass fibre house isolation wool laying around that I could nail to the inner walls and / or stuff inside the cabinet.
I would love to hear your -and/or anyone else's- thoughts on this.
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Heres a updated photo with the correct stands...
Hmmm pretty simple design.
But the overall shape of the base and beveled edges.
All come together for a more sophisticated look.
Purchased or built? Wood metal ?
Easy to calculate in modern times with a Spread sheet / Simulator.
Since equations are already included.
Sealed, Max flat response is Q or Qtc of = .707 which is 45.6 liters (yellow)
Max flat delay is Qtc = .577 which is 114 liters ( orange)
The response matches transfer function of lower Q Butterworth or Bessel filter.
So if you want more punch or bass you can add that with normal EQ with different music.
If Q is higher which some use, ( smaller box ) Any speaker can be likely to get boomy or sound like EQ already added but cannot be turned down.
Like .6 to 8 Qtc or to small box makes peaks in lower response.
For ported. Driver Total Quality or ( Qts ) is not really high. but is high at .45 for this driver so it will want a bigger box. To also not be too boomy, flat response. So EQ can be added depending on music. High Qts usually use 4th order filter to align the response. So use .577 Qtc volume = 114 liters. Expect leakage with port is expected
100 liters more reasonable.
No guessing with port tuning, Driver Fs is answer. No more than 3 to 5 Hz below or above. 3rd order tunes above , 4th order tunes below or same as Fs
We want 4th order. Fs is 39 Hz so tune below 3 to 5 Hz or 34 to 36 Hz
100 liters 35 Hz port tune
Assume driver has typical 6mm front plate Xmax likely not more than 3 or 4mm, power wont be too high so port really doesnt have to be too large.
Normal 2" to 2.5" inch size is fine. In 100 liters wont be much longer than 1 to 2 inches for 35 Hz need to calculate yourself when you buy port based on size.
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By my quick calculations, the SB20FRPC30-8 asks for a BIB of about 420 liters. But his design would also be acceptable.
I highly recommend the BIB style of design. It allows very deep extension and very open, realistic bass sound. If you can live with it's height.
don highend squeezed with a sophisticated filtering maximim linearity from the driver, design called "grand petit"
https://www.donhighend.de/?page_id=10899
https://www.donhighend.de/?page_id=10899
2 more filters
https://www-hifi--forum-de.translat...&_x_tr_hl=en-US&_x_tr_pto=wapp&_x_tr_sch=http
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https://www-hifi--forum-de.translat...&_x_tr_hl=en-US&_x_tr_pto=wapp&_x_tr_sch=http
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SB Acoustics SB20FRPC30-8 (8" Fullrange Cheap Monster II)
post#591
Hi @Stanislav
Very nice compact enclosure.
Could you share how you made your enclosure an aperiodic enclosure. Looks like a cooling fan protective plastic screen with a dust filter but I could be wrong.
My pair of SB20 is being delivered this afternoon.
Thanks,
Eric
Hi Eric,
It's very simple to turn a sealed box into an aperiodic one, just cut a hole, either at the back or at the front, stuff that hole with some felt or foam and start measuring the impedance of the speaker. Aim for a flat impedance at the resonance. But then listen to some material you are familiar with as if you stuff the aperiodic vent too much you are back at a sealed enclosure. The idea is to restrict the air flow, but not to block it completely.
I've been using aperiodic boxes for a very long time as I found they, like open baffles, have excellent transient response and produce the most natural mids and bass.
The vent itself is indeed a fan protective cover with a layer of felt inside.
Dynaudio had some variovents long time ago which had relatively soft foam in them.
Cheers
Stan
It's very simple to turn a sealed box into an aperiodic one, just cut a hole, either at the back or at the front, stuff that hole with some felt or foam and start measuring the impedance of the speaker. Aim for a flat impedance at the resonance. But then listen to some material you are familiar with as if you stuff the aperiodic vent too much you are back at a sealed enclosure. The idea is to restrict the air flow, but not to block it completely.
I've been using aperiodic boxes for a very long time as I found they, like open baffles, have excellent transient response and produce the most natural mids and bass.
The vent itself is indeed a fan protective cover with a layer of felt inside.
Dynaudio had some variovents long time ago which had relatively soft foam in them.
Cheers
Stan
