What simulation software are you using? A 3" vent is way overkill in your case. I think the software is giving you unrealistic predictions for vent air velocity.
If you are using WinISD, get the alpha pro version. When modeling your speaker keep in mind that WinISD assumes your driver never runs out of xmax when calculating vent air velocity.
Assuming a 9L enclosure tuned to 42hz, the air velocity in a 10" long 1.75" round vent would reach 10% the speed at the tuning frequency with 55 watts of power.
If you have a 10" cube, using .5" thick building materials, you should have 10-11L volume after port and driver displacement. Using a 9.5" long & 2" diameter port would get you a tuning frequency between 41 and 43hz. Having the end of the port only 1" away from the back wall extends the acoustical length of the port. At 55 watts peak vent air velocity would be around 8% the speed of sound, which is good.
If you have the choice of getting a PR, go for it. No more worring about fitting the port, and it increases the wow factor of the speaker.
Dan
How lo to go?
I feel compelled to point out that the fundemental of the lowest note is almost never the lowest frequency needed to accurately reproduce that instrument. This is because any struck or plucked instrument has an attack on the front of its envelope. The attack usually runs down below 20 hz even if the note being plucked is in the hundreds of hz.
The spectrogram in the attached link is me plucking a bass guitar string (low E), letting it sustain, and then the A string. power is color, and y axis is frequency. Note the attack on the front end. Note also (bass players) the fact that the fundemental is 20 db less than the first harmonic on the low E coming out of the guitar itself. Bass guitar spectrum
(The link points to a big image, may load slowly on a dial up line. )
I feel compelled to point out that the fundemental of the lowest note is almost never the lowest frequency needed to accurately reproduce that instrument. This is because any struck or plucked instrument has an attack on the front of its envelope. The attack usually runs down below 20 hz even if the note being plucked is in the hundreds of hz.
The spectrogram in the attached link is me plucking a bass guitar string (low E), letting it sustain, and then the A string. power is color, and y axis is frequency. Note the attack on the front end. Note also (bass players) the fact that the fundemental is 20 db less than the first harmonic on the low E coming out of the guitar itself. Bass guitar spectrum
(The link points to a big image, may load slowly on a dial up line. )
Thats a very important point,the fact that alot of musical instruments have 2nd harmonics much higher in amplitude than the fundamental.
Ideally ofcourse we would have systems extending to 0hz - infinity..
Practically, I find an F3 of 40hz is fine for most music,with F3 33hz is much more fuller,and fun - I listen to electronic type music alot so once ive heard the lower sub, ofcourse i always prefer it.
Ideally ofcourse we would have systems extending to 0hz - infinity..
Practically, I find an F3 of 40hz is fine for most music,with F3 33hz is much more fuller,and fun - I listen to electronic type music alot so once ive heard the lower sub, ofcourse i always prefer it.
rjon17469 said:
Too small. You break 5% the speed of sound at only 6 watts. If you need to keep this box small, go with passive radiators.
Can you change the dimensions of the box so you can fit a longer port? Maybe go with 9"x10"x11"? Then you could fit this, and still get a low 40's tuning.
Dan
owdi said:
I realized that. I played around with the port dimensions, and I found that if I indeed use three one inch ports then I would hit about 10% the speed of sound max at 70 watts, which is what my amp rating is.
The reason why I'm going for smaller ports is actually a combination of two things. One, they tend to be shorter, making it more flexible for me. Two, I want to have everything on the front baffle, the ports under the driver, and 1" ports, side by side, allow me to keep the overall case relatively short. (And three ports side by side looks cool too, IMO)
I think three 1" ports, at 9.5 inches each, tuned at 42 hz into a 10 liter enclosure will be my design.
Sound ok you think?
Reece
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