Olive Tuning

This Section Last Updated: 10-10-2005

Now for the fun part. Testing and tuning the speaker.

Here are the measured T/S params for the Tang Band W3-881SD:
Fs 112.7
Qms 4.161
Vas 1.04 liters
Xmax .5mm
Qes .83
Re 6.6 Ohms
Z 8 Ohms
Pe 15 Watts
Qts .692
Sens 83.08 dB

I used Bass Box Pro to develop the 4.75" ID cube sealed box.
Vb .062 Cu. Ft.
Qtc .698
F3 139.7 Hz

Once assembled i measured the Qtc and F3 of the box with heavy stuffing and got a Qtc of .81 and F3 of 130Hz.

Not bad. Once i reduce the volume a bit with crossover parts i should get a Qtc closer to .7

Here is the initial response of the driver at 1 meter. Not bad. It looks like i just need to tackle some baffle step and a peak at 10K.

This picture is of a near and far field measurment merged with diffraction included.

And this is going to be the first crossover that i try. L1 and R2 are there to bring down the baffle step, and L4 R5 C3 are there to knock the 10K bump down.

I do want to stress that L4 is VERY sensitive! When i say use a .07 mH inductor i really mean it. I am going to purchase a .10mH inductor and un-wind it to acheive .07mH. I will be using Soundeasy's LCR meter to measure the inductor and verify it is .07mH

I made a simple animation of different L4 values to illustrate how much the response changes with different values.

The animation goes from .05mH to .10mH.

Crossover Parts
255-232 .56 18GA inductor
255-202 .10 18GA inductor
004-25 25 Ohm resistor
027-542 3.0uF cap
004-8 8 Ohm resistor

I got the crossover parts in the mail and unwound the .10mH inductor to .07mH. I ended up taking 8 turns off of the inductor to get .07mH.

Start = .0976 mH
-2 Turns = .0879 mH
-3 Turns = .0831 mH
-5 Turns = .0778 mH
-7 Turns = .0715 mH
-8 Turns = .0694 mH

The picture shows a comparison of the Soundeasy predicted response with crossover (Black Line) and the actual measured response with built crossover (Red Line).

The 8K-20K region creaps up a little high, but i dont think it will hurt the sound much. We will see.

Project Sections:
The Olives
1. Turn Baby Turn
2. Olive Tuning
3. Listening and Crossover Tweaking
4. Square vs. Round
5. Subwoofer
6. Olive Painting
7. Finished Project

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