I have a Audiobahn 8" sub that I"m thinking about putting in the C4.
The attached page shows the specs of the "AW800X" in a sealed
enclosure as Min 0.1 and Max 0.25. That just seems too small for
a sub to me. Can someone look at the chart and tell me if I'm reading it right?
http://www.audionmore.com/audiobahn/...fers_specs.htm


[Modified by 92corvette, 8:32 PM 3/4/2002]

 

I think you are reading it right, but I think its to small. I would build the box bigger and then "tune" the box after it is built. I can help you with that if you need. Black1

 

If you are looking where it says "displacement", I believe it is talking about how much room the actual sub takes up in the box (basket, magnet, etc.). An 8" woofer should require about .5 cu. ft., depending on all of it's parameters (which, sorry to say, I cannot do anything with at this time). :D :cheers:

 

After reading a few other posts, I realized that I can build the box too big and if I dont' like the way it sounds, I can just add something solid in the box (maybe a brick or 2 :-), to tune it on the fly. I have sealed up the storage compartment airtight and I'm going to go ahead and install it on top of the storage area, then see how it does.

 

I think you're gonna be hating life if you know good bass, and try and put that sub, which is designed for vented enclosures, in a sealed box.

The T/S for that sub show an EBP of 94.5 which is WAYYYYY to far into vented territory to get it to sound good sealed.

Just running some quick numbers;

Ported (vented) box
.35 cu ft
Tuning frequency 40Hz (F3)
Port 2"x13.35"

Sealed box
(gets worse as the box size increases, and a little better, but not much, as the box size decreases)
.35 cu ft
F3 = 80.5Hz

.5 cu ft
F3 = 82.96Hz

.25 cu ft
F3 = 77.7Hz

Here's a plot of both vented and sealed.


JMO, but it will probably sound like azz sealed... :D




[Modified by Anguish, 12:22 PM 3/8/2002]

 

OK, now I was hoping someone that understood enclosure design would look at this. My problem is I still don't know what T/S and EBP means. But I gather from your info that tuning frequency should be at 40hz? And the best would be a box .35 cu ft with a port 2" wide by 13.35" long? Should the port be located any particular distance from the speaker?
I just happen to pick up this sub for a few bucks. Maybe I should look for a sub to match the airspace of the storage area instead of trying to design an enclosure around this sub?

 

Don't get me wrong, that speaker is quite good. It, as most things, just needs to be used as it was intended.

T/S are the Thiele-Small parameters of the speaker.

EBP is the Efficiency Bandwidth Product. It is just a guide used to determine whether a speaker is better suited for sealed or ported/vented enclosures. It is defined by Fs/Qes. (Fs is a T/S parameter defined as the Frequency in free air, not boxed, that the impedance of the speaker increases dramatically. Qes, another T/S parameter is electrial Q of the speaker.) The guide most enclosure builders I know use is;
EBP < 50, the speaker should be used in a sealed box.
EBP > 90, the speaker should be used in a ported/vented box.
EBP is between 51 and 89, the speaker may be used in either box.

Assuming you built everything exactly correct, .35 internal volume a 2" ID port that is 13.35" long the tuned frequency of the box would be approximately 40Hz. Now, that being said, you can see how building a vented box is MUCH more exacting than a sealed box.

When building a vented box, be SURE to have taken into account the driver displacement (how much airspace the back of the speaker itself is taking up) and the displacement of all internal bracing, or the tuned frequency will change slightly. For example, if internal volume should be .35 cu. ft., the driver displaces .15 cu ft, and internal bracing of the box takes up another .1 cu. ft., the total internal volume of the box would need to be .6 cu. ft.

More info if you need it... :cheers:


[Modified by Anguish, 3:24 PM 3/9/2002]

 

THis is good info. I'm learning a little. I guess my problem now is if I want to port, I don't have 13.35 inches depth for a port. I wonder if the dimensions of the port can be changed. Maybe wider and shorter? I only have about 12" deep for the port tube. Maybe that's close enough?

Actually, now that I think about it, I don't see how a .35 cu ft box can be made with 13" depth with an 8" speaker. Seems to me that 8x8x13 would add up to about .7 cu ft. Maybe I'm doing the math wrong.

Thanks for the help. I do want to try to do this right as I appreciate a good sound.

 

The port doesn't have to be straight :D

Down a few inches, 90 degree, then a few more inches, etc..

The biggest problem I have with this sub is the differing specs I'm finding on it over the web.:rolleyes:


[Modified by Anguish, 4:11 PM 3/9/2002]