Why? it's true that looser suspension makes the driver impulse response worse and increases the Q factor, but that's not as bad for subwoofer as it is for a mid-range driver.
That was when the driver was pushed to the max. You are right, it was a little bit out of control but not as much as seen in the video. You may consider the interactions between the camera shooting freq. and the driver freq.
So you strongly recommend not to make any changes to the driver? If so, the only option left in order to prevent the driver from making such noises is to put it in a smaller box, which will decrease its efficiency and low end response. Is there a better Idea? What about a T-line box?
The cavity resonance in the hole causes colouration i do not like.
I wouldn't. The pleated surround is there to give it better HF performance than a 10 with a rolled surround. I would not try to use it as a sub. It would make a decent woofer for a FAST, but if you need a sub, you should get a sub.
Box size does not really effect efficiency, but it could impact the low frequency extension (do keep in mind that F3 is a useless number from the POV of human hearing, you should be looking at F10 (or F6), althou too big a box will often degrade the quality of the bass.
An ML-TL is likely going to give max LF extension, do you have useful T/S parameters?
dave
OK I got it! I'll never do it.
What about making holes in the cone somewhere under the dust cap? I've seen it in several woofers.
I will get a sub when I have the money for it. A pair of 15's maybe.
I'll measure them. by my multi meter. I think it's accurate enough for this project.
Thanks for the info.
Tedious but probably produces more useful numbers than a lot of the software used to measure T/S. Keep in mind that T/S are curves not scalars and the numbers you get depend on where they are pulled off the curve.
The Subwoofer DIY Page - Measurements
dave
Doesn't resonances in the sealed space under the dust cap bother you? I find that much more annoying. It causes ringings in the mids. I treated the problem in several woofers by making holes in the cone under the dust cap. the results were pretty acceptable- and there were no pole piece "tube" resonances. The only problem this strategy will face is cone weakness towards mid-basses if digging too many holes.
They can. Being a smaller space they will be higher in frequency.
We deal with it either by taking the dustcap off and installing phase plugs or by making the dustcap more opaque to stuff behind the dust cap. At least some of the drivers we use also have vented voice coils.
dave
Thank you all for replies. Now I know which way to go with my new pair of vintage woofers. There's only one question not answered, and that's whether making holes in cone or spider any advantageous. I guess no one has much experience with this kind of thing. Any ideas on it is appreciated, because I use this technique a lot.
Could you please be more specific?
The side effects are dust and small iron particles get into the gap. and the cone and spider weakness.
On the other hand, you get extra ventilation, lower Fs, extra efficiency and more low freq linearity especially in bigger boxes like car trunk (where I use this technique to push stock car speakers to their limits).
I have seen pictures of an example of someone successfully drilling a hole thru the pole piece (BOFU), but the purpose was to allow mounting of a coax tweeter, not to ventilate the driver (althou taking the dustcap off did that).
dave
dave
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