My twin ten inch sub does not work.

Status
Not open for further replies.
Jump to Latest
T

tade

Member
Joined 2005
www4.ncsu.edu/~tkwolick
#1
Specifications:*Power handling: 110 watts RMS/220 watts max *Voice coil diameter: 1-1/2" *Le: .5 mH *Re: 7.1 ohms *Frequency response: 40-2,200 Hz *Magnet weight: 20 oz. *Fs: 41 Hz *SPL: 86.4 dB 1W/1m *Vas: 2.19 cu. ft. *Qms: 4.46 *Qes: 1.60 *Qts: 1.19 *Xmax: 3.5mm

There is some specs. I put these two in a 40 liter box with a port of dimentions .5 inch by eleven inch by 22 inches, and had planned on a port tuning of twenty hz. i used WinISD to help me but other than that, just dove in.
I expected there to be much air movement out of the port at its load frequency, but there i very little. And very little at any other frequency. The port end is about two inches off of the back wall.

Please ask me any other questions so that i may be more specific, my H baffles have more bass!

Many thanks
 
#3
These drivers are not designed to play 20 Hz efficiently.

Try tuning them higher by shortening the port.
Try 11 inches long, then 5.5 inches long if not enough bass again.

It will be less than good, but you'll have more bass that 100% sure.
 
#4
excellent, this is just the advice i was hoping for. The port is another piece of wood close to the bottom. I suppose i will just drill some holes in it.
As to how much air? hmm, I figured more than a bit because of the large surface area.
thanks

Let me do a little epxperimenting and ill come back with results.
 
#5
Would be better to remove the piece of wood, cut to the required length and replace. But do what you have to do hehe!

You could also put a bigger port or a second one, that would do the same effect as using a shorter port.
 
#9
Yes, the ratio I was referring to is height and width. Your surface area would not change by keeping within the 7:1 geometry. It would though if you used multiple ports to get a desired total area. I'm still waiting for further opinion on the ratio issue in non-circular ports. Anyone...?
 
#10
Guys, i did some drilling and it is now tuned to about 27 hz, up from 18. Now it works and it sounds about as great as a fourty dollar sub should! i am quite happy, and not at all worried about blowing out the thirty dollars worth of drivers. Ill post pics, but only for a laugh, I really shouldnt be proud about this project...

Thanks for the help guys!
Thaddeus
 
#11
As has already been said, the Qts of this driver is far too high to fit in a bass-reflex box. Furthermore, a box of 40 litres is far too small for two drivers with a Vas of 62 litres. And finally, 18 or even 28 Hz tuning is far too low for this driver with an fs of 40 Hz.

The simulated response of your two designs are shown in the figure below, black being the original design, blue has the changed tuning of 28 Hz. If you keep th 40 litre box and do isobaric mounting, put a great deal of stuffing in the box (not too near the vent, though) and tune the vent to 40 Hz, you get the red curve, and if you manage to lower the Qts value to 0.5 you get the green curve (with not too much stuffing).

If you do not want the isobaric mounting, you can get the same result with a 160 litre box and the drivers mounted side by side. In this case you will get a 6 dB increased sensitivity and maximum output level.

The Qts value can be lowered either by using a special amplifier with negative output resistance, or by fitting a basket filled with damping material on the back of the driver. The air from the driver should be forced through the damping material.

An externally hosted image should be here but it was not working when we last tested it.
 
#12
RE:
The Qts value can be lowered either by using a special amplifier with negative output resistance, or by fitting a basket filled with damping material on the back of the driver. The air from the driver should be forced through the damping material.

Crazy didn't know you could change the qts that easy I thought youd have to physically change the parts like the spider.



I like pictures so feel free to post. I just got a pair of 10" off ebay for $13 cdn (local pickup so no shipping either) They look like out of like mid 80's floor standers. Will be trying them as a computer sub at hopefully ~33Hz ported but I need to do measurements first.
 
Status
Not open for further replies.
Top Bottom