About eight years ago, I was built a 2-way speaker system using SB Acoustic drivers. The driver for woofer is SB16PFC25-08 and for tweeter is SB19ST-C000-4. You can visit the post here.
Although this speaker is sound good, but it is not perfect. This is because working on multi driver is challenging. The crossover is the components module to split the frequency range between woofer for low pass and tweeter for high pass. The crossover should make the sound from each of the drivers well blending with the correct phase, so the sound will be coherent. This is not an easy task since the crossover calculation should be made correctly. I made many changes since the day this speaker finished and the last update is on last August here. The goal for those changes is to make the sound enjoyable to listen, less dip and peak especially on the cross-over point, and make the sound fuller and wider.
So, in this post, I made other changes in this speaker system by using the detail parameter on each driver, then I calculate for the correct crossover point and components related to it. The damping materials inside also changed.
Let's take a look.
First, the crossover point is based on the Fs which for the woofer is at 4000 Hz and for the tweeter is at 1000 Hz. We should avoid the driver to work beyond the Fs point and those Fs difference between woofer and tweeter is a crossover point that I can choose. So, I take the middle point on each driver Fs, at 2000 Hz crossover point.
The impedance is very critical. As we are all know that impedance is the resistance that changes all time depends on the signal come into the driver. So, flattening the impedance will help the frequency response more accurate. The parameter for this calculation is using the resistance on each driver, normally indicate by Rdc. Previously I never calculate this method, so the major changes now is using this impedance flattener.
The result for the calculation is like this:
For the woofer crossover, I using 0,68 mH inductor and then the series of 6,8 ohm resistor and 16,5 uF capacitor to ground for the impedance flattener.
For the tweeter, I using 10 uF capacitor and 0,58 mH inductor to ground. The impedance flattener is only using 12 ohm resistor, it parallel with the inductor.
The sensitivity for the tweeter is 89 dB and the woofer is 88 dB. So, I need to reduce the tweeter sensitivity by using 1 ohm resistor in series before going to the first 10 uF capacitor as explained above.
The crossover components I am using here is standard quality. Especially for capacitors, I am using Bennic PMT capacitor which is very affordable and sound good. The value when measured are not exactly like my initial calculation, so I put a small capacitor in parallel to rise the capacitance value. The small capacitors using high quality Jentzen cross-cap.
The inductors are all hand winding using 0,5 mm enameled copper wire.
The resistors are the most expensive components of all. They are Jentzen MOX 10 watt type resistor. I prefer to use this resistor in the crossover module because the sound not become muffled.
The previous damping material is using wool. Some of speaker design stick to this material, but for me, I prefer using thick carpet material. This is one of my favorite damping materials, especially to make the bass sound deeper and cleaner.
The carpet is cut based on the surface dimension, they are glued and attach to the enclosure. Working on this carpet material will spending more time compare to the simple wool damping material.
The crossover module is sitting above it with the plastic spacer attach on the bottom of the enclosure. I make this crossover placement secure and tidy, just like high quality commercial speaker.
The speaker cable use here is high quality and covered with cloth-tape. This treatment helps to reduce the vibration when the cable hanging around inside the enclosure.
With all set, how does it sound?
I think overall sound signature is similar to before, but now, the sound is more fuller and detail. Especially on the crossover point, the gap between woofer and tweeter is now blending well, just like one full-range sound. The mid-range sound also smoother and pronounce.
The overall frequency response doesn't show any sign of peak or dip, it more enjoyable to listen with full of detail and smoother sound.
The new damping material is as expected, contribute to better bass. The bass is tight and more control.
So, today changes is lead to better sound result.
Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.
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