2 Way Speaker System

Whitesunds National Park, NM USA Photo by Yuichi

This 2 way system consists of three major components. Those are a 17cm woofer, a tweeter and a 6dB/oct passive filter on top of a bass-reflex enclosure.

One of advantages of this kind of smaller system has flexible positioning capability of the tweeter. This page introduces the linear phase approach to generates clear and sharp sound.

The factors to be considered are as follows.

-Physical locations of two diaphragms
-Group delay/phase shift of both diaphragms
-Passive filter effects

(note: Since there are three sound sources in the system. A tweeter, a woofer and a enclosure vent. However, the vent output is out of consideration in this story.)



Specifications and TS parameters for Speakers

- Woofer: Alpine DLX-Z17W (17cm DDLinear magnetic circuit)
(Impedance: 6Ohms, Music power: 200W p-p, Frequency range: Fs to 10KHz, SPL: 89dB/w(m), Fs=67Hz, Qts=0.73, Vas=0.95, Sd=129cm^2, Le=0.18mH)

- Tweeter: Alpine DLX-Z30T (3cm Concentric dual emission)
(Impedance: 4Ohms, Music power: 120W p-p, SPL: 89dB/W(m), Frequency range: 3.5-60KHz)


System crossover frequency is set as 4KHz in the system, this is relatively low comparing to the manufacturer recommendation. However, the result looks good to me.

Advantage of this system is adjustability of the tweeter position. Also, the crossover frequency is high. This means that we can easily remove the mismatch problem of two sound sources by simply sliding the tweeter location.

This system utilizes 6dB/oct LC filter. Concept is to make everything simple. A capacitors and a series registers are to have flat impedance curve.

The woofer and the tweeter gain curves with each filter are shown below. Red line represents the woofer. The impulse waveform of the original system is as follows. The tweeter wave comes faster than the the woofer impulse. This delay consists of physical difference of diaphragm locations plus the group delay of individual speaker driver plus some contribution of the filter.
In this configuration, the Wavelet shows as below. Tweeter and woofer sound pressure level well match at the crossover point. However, arrival timings from both sound sources do not match. Then, I moved the tweeter location to match the timing of the woofer. Below is the perfect match of both timing. But phase does not match.
Finally, reversal of speaker cable connection matches both timing and phase. This property is almost ideal to the linear phase To observe the impulse response again. Leading edge of both the tweeter and the woofer match perfectly.
The frequency response is the most sensitive property to human ears. I put the property in the right fig.

Red line indicates "before" adjustment of the tweeter location is made, and black line indicates "after".

However, the frequency response curve does not include timing factor. So, it is important to have a flat frequency response curve with having arrival timing to the listener matched.

It is recommended that the speaker cable connection with the power amplifier is positive or negative depending upon the filter slope property such as 6db/oct or 12db/oct as a conventional way. However, this concept assumes that the diaphragm locations matched and no group delay exist. In reality, those factors disturb the phase and delay of sound sources.

.... Return to System Adjustment Page
Whitesunds National Park NM, USA Photo by Yuichi