8 inch woofer test, BMS vs 18Sound

The 8/9.5" Mid-woofer

We will test several 8/9.5" Mid-woofer in this article:

We will measure distortion with and without a 1.2mH air core inductor, to reduce the driver breakup impact on distortions when possible, as seen in speaker breakup article.

In essence: We use Back Electromotive Force principle with an air core inductor that will increase gradually the impedance (affecting the voice coil) and linearize the woofer in the same time, it works very well if the woofer is already rising up in his final box and need linearisation.

It will reduce a lot H3 and H5 distortion related to breakup.

Distortion measurements are done at 25cm 98dB, all drivers are EQ flat to be compared.

Discalified Woofers

There is too many woofers to have readable charts in overlay so severals has been disqualified, there is the reason why:

loosers H3

Top 4 Distortion without inductor


8 inch woofer H2


8 inch woofer H3


8 inch woofer H5

All performs extremely well, the WO24P is the better when the STX is extremely good and costs literally 10 times less.

The Wavecore WF223 is good for a high crossover.

It’s not shown here as all are EQ but the SB23 is naturally flat, an advantage in passive filtering but not mandatory in active one when we use the air core inductor as we will see it.

Top 4 Distortion with inductor

Inductor doesn’t impact H2 so there is no change on it.


8 inch woofer H3


8 inch woofer H5

We see here that with the air core inductor there is a top 2 almost ex-aequo between two drivers, the WO24P and the STX W22.200.8.MCX_V2.

The SB23NBAC remain on charts even if he don’t have and cannot have an air coil (has it not rise up in box)

Temporal measurement on woofer

When we do it with a compression driver and a horn we measure in fact the couple, for the woofer we don’t want to have the box and the way the woofer is integrated with it.

If we measure CSD or Burst Decay at 25/32cm we measure the woofer with his very close environment (even if we gate the measurement).

If we measure the woofer at 2cm we will only have the woofer alone, and we will see that at breakup his temporal measurement is not good. The rest will be perfect, for all.

So avoid being close to breakup, anyway distortion will dissuade you to go near to it.


Without the little rise up on H3 at 200/300hz the STX will be ex-aequo on distortion with the WO24P, STX just have released a V3 of this driver (here it’s the V2).

The self transform both WO24P and STX in willer woofer for a 2 way usage cut at 1250/1300 hz with an X-Shape 25.

The best compression drivers usable with them are tested here: 1" compression driver test.

There is a huge difference in chassis between the WO24P and this STX that is an stamped sheet metal making the STX harder to integrate, but well, we have seen that it doesn’t impact performances.