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View Full Version : Is there a way to empirically test the tuning of an enclosure?



jibberjive
04-16-2007, 03:59 PM
As the title says, is there an empirical means of finding the tune of an enclosure other than using the math (or box building program) and the enclosure volume, port area and length?

audioholic
04-16-2007, 04:04 PM
You want a way to find a mathematical answer without using math? I guess you could try praying to God for the correct answer. Im really not following what you think you want here.

jibberjive
04-16-2007, 04:35 PM
You want a way to find a mathematical answer without using math? I guess you could try praying to God for the correct answer. Im really not following what you think you want here.

No, I'm curious if there's another way to test it other than the math (ie. measuring port mach or something).

Twistid
04-16-2007, 04:38 PM
play test tones , where the subwoofer moves the most is the usual tuning

helotaxi
04-16-2007, 04:53 PM
Actually it's where it moves the least. You can test it in the same manner as the T/S parameters are tested, but you need to already know the T/S parameters and then do the math backwards to figure volume. Tuning though is easy, wire a resistor in series and then measure the voltage across the resistor using a series of test tones. Where the voltage drop across the resistor is the least, the impedance of the driver is at its max and that the the resonance point of a ported enclosure. It works exactly the opposite for a sealed box.

Volenti
04-16-2007, 06:43 PM
Actually it's where it moves the least. You can test it in the same manner as the T/S parameters are tested, but you need to already know the T/S parameters and then do the math backwards to figure volume. Tuning though is easy, wire a resistor in series and then measure the voltage across the resistor using a series of test tones. Where the voltage drop across the resistor is the least, the impedance of the driver is at its max and that the the resonance point of a ported enclosure. It works exactly the opposite for a sealed box.

Yes, do this with the enclosure both outside and inside the car, and notice the difference in frequency and impedance value. :graduate:

ngsm13
04-16-2007, 07:52 PM
play test tones , where the subwoofer moves the most is the usual tuning

Completely and utterly incorrect.

:fyi:

nG

Immacomputer
04-16-2007, 11:03 PM
It's very simple to just play some tones about .5hz apart and check for the least amount of cone movement.

I usually do this with a signal generator after I finish an enclosure to see how close the final product turned out.

jibberjive
04-17-2007, 01:12 AM
So the difference in excursion is distinguishable even up to .5 hz I take it then.

play test tones , where the subwoofer moves the most is the usual tuning
No need for me to say it again since it's been said twice;)

Volenti, so the environment outside of the enclosure affects the impedence rise of the enclosure as well? I thought just the enclosure affected it, but idk:scared:

Volenti
04-17-2007, 04:51 AM
Volenti, so the environment outside of the enclosure affects the impedence rise of the enclosure as well? I thought just the enclosure affected it, but idk:scared:

Yes indeed, the last vented enclosure that I did detailed measurements on had a tuning frequency of 47.5hz @ 14.4 ohms impedance (dual 4ohm sub, coils in parallel) in half space (box sitting on the ground) and a tuning frequency of 45hz @ 10.95 ohms rear firing in the boot of my small sedan.

Even bigger changes can be seen in more exotic enclosure designs like transmission lines and horns.

helotaxi
04-17-2007, 09:55 AM
Since the car is a small space, the air in the cabin of the car will affect the movement of the cone since it acts as another part of the enclosure. The cabin will thus affect the tuning of the enclosure and the response of the system.

PV Audio
04-17-2007, 06:38 PM
play test tones , where the subwoofer moves the most is the usual tuning
You're merely boosting your output in that frequency range, not boosting speaker excursion. A frequency much lower than tuned in a large box will move quite more than the Fb.

JohnBlayz142
04-18-2007, 02:09 AM
play test tones , where the subwoofer moves the most is the usual tuning
:suicide: Here for 3 years and you still have this backwards? Just proves post count means nothing around here.

Decipha
04-18-2007, 02:46 AM
post count just determines how much time u spend on the forum

i've seen people here as long as me with over 10k

jibberjive
04-18-2007, 04:03 AM
post count just determines how much time u spend on the forum

i've seen people here as long as me with over 10k
eh, not necessarily. Some people post alot, some don't. I've spent my fair share of time on the forum, yet I don't have an insane high post count.:blush:

PV Audio
04-18-2007, 06:56 AM
He's right, I have 16k posts and haven't learned a **** thing :D