Question for box volume

kpero

Member
2005-04-21 10:37 pm
Croatia
Ok!
I'm new on this forum, and have question about woofer design.
I have one speaker bought from my friend. Nothing fancy, just good for my first project.

Bigest problem is in driver volume. For vented design WinISd calculate 130 l, but that is too big for my house (green line in diagram ).

For smaller box it has - 3 dB on 50 Hz which is still high for me.

Is there a way to drop frequency below that or just with biger volume i can get lover frequency.
 

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You have to understand that the room will lift up the frequency response in the low end. You gain about 4 dB at 20 Hz and 2 dB at 40 Hz.

You can tune your box lower than that.

To have a lower tuning point, you can have a larger box, a box with two drivers in a isobaric enclosure so the box is 2 times smaller for the same tuning frequency, or use electronic correction.

You can't use electronic correction much because you have only 5 mm of Xmax to work with. I suggest isobaric if you have another driver like this one.

Final solution is to use the largest box you can tolerate, if it's 60 liters, try tuning it to 25-30 Hz...
 
My bad,

Anyway your T/S-parameters don't go along.

Qts:0,36 / Qes: 0,7 / Qms: 6,33 Now what's wrong here??

Your Qes doesn't look exactly right but your Qts just looks plain wrong.

Woofer has much more cone excursion than that
How do you know? (Your not talking about Xmech right?)

Xmax going to be enough or not largely depends on the place your going to put the cab and your desired output.

Remember you can increase the internal volume by (about) 20% if you stuff it correct.

BTW: You're using WinISD 0.44 Don't do that!! Use WinISD Pro a7 (or a6) to see some of the more important things (like cone-excursion and applying filters).

Mvg Johan
 

kpero

Member
2005-04-21 10:37 pm
Croatia
Will that room gain also have impact on cone movement?

By the way this woofer is peace of junk :)). That t/s parameter are all but true.
Tomorow i'll buy some other speaker. Hope it will be better than this one.

Here are some t/s parameter of that driver.
Qts= 0.370
Qms=1.75
Qes=0.47
Prms=150 W
d=250 mm
Spl= 92 dB

Can't find it's Xmax. How can I measure that parameter?

I think that box of 50 liters will do good for this one. Vented of course
 
Mikey p said:
Room gain is alot more than that. From the graphs I've seen from Adire Audio, typical room gain is 10db at 20hz and 7db at 40hz.

Yes, but that room gain curve account for placement in a corner, which lift up every frequency from 300 Hz and down with an even 6 dB.

Adire Audio curve is at +12 dB at 10 Hz, +10 dB at 20 Hz and +6 dB at 40 Hz, if you remove the 6 dB boost from corner placement from that, you get +6 dB at 10 Hz, +4 dB at 20 Hz and +2 dB at 40 Hz.

Corner placement = +6 dB
Wall placement = +3 dB
Center of the room = 0 dB
 
I want to correct my last statement...

Adire room gain curve without corner loading is :

+6 dB at 10 Hz
+4.5 dB at 20 Hz
+3 dB at 40 Hz
+1.5 dB at 80 Hz
+0 dB at 160 Hz

As you can see, placing a subwoofer in the center of the room exhibit about 1.5 dB of gain per octave starting at 160 Hz in a room where the longest dimension is under 5.5m (18 ft).

Then, add 3 dB to the curve if near a wall or 6 dB if in a corner.