We develop not only our own models of speakers, but also upgrade speakers from other manufacturers

Upgrade of crossovers to ASW Varius Mod.1 speakers

The design is traditional: 2-way shelf speakers in the bass-reflex cabinet.
Manufacturer’s specifications

Review, test listening and measurement of characteristics.

The nature of the sound is immediately dominated by low and high frequencies.
In combination with the weakened mid-frequency range, the sound is somewhat synthetic.

What will the measurements of the characteristics of these speakers show?

Amplitude frequency response

The frequency response fully confirms the subjective impressions of the sound. Medium frequencies in the range of 300 Hz – 6 kHz are underestimated by 6 dB compared to low and high frequencies. This is 2 times the difference in sound pressure between these frequency ranges.

From my own experience of listening to many systems, I want to note that this type of sound with a predominance of low and high frequencies with attenuated mid frequencies is a fairly common feature of many speakers.
Such a presentation may give the false impression of a larger and more detailed sound, but at the same time it makes it rather indistinct. The basis of music – instruments and vocals are played in the background, not in the foreground as it should be. Different music recordings with different nature of sound are transmitted monotonously. The intonations and emotions of performers living in the mid-frequency range are veiled among the dominance of bass and sibilants. Prolonged listening is not interesting and causes discomfort over time.

In most cases (and these speakers are no exception) the nature of the sound of multi-band speakers form the characteristics of distribution filters. ІOther factors, such as unsatisfactory speaker performance or a poorly designed cabinet, are much less common.
In the case of these speakers, the graphs of the characteristics of the filters fully confirm this:

Frequency characteristics of filters and impedance

Original filters of the 2nd order from the MF and from the HF speakers, the distribution frequency is about 4 kHz. The low-pass filter reduces the signal level for the woofer from 300 Hz and above, and the high-pass filter generates too high a signal level for the tweeter. These factors fully explain the nature of the frequency response and the sound in general.

Structurally, the crossovers are made quite well, using inductors with an air core, Philips MKT capacitors and wirewound resistors with 5% nominal tolerance.

Original filters ASW Varius Mod. 1

Measurements of the characteristics of the low-frequency speaker and its operation in the original box with the bass reflex port show that the acoustic design is set correctly, as evidenced by a fairly uniform frequency response at low frequencies.
The impedance graph shows that the bass reflex port is tuned to 53 Hz. The minimum resistance is 4.1 ohms at 254 Hz, the maximum is 25.3 ohms at 1.64 kHz. There are no local impedance dips, which can be an undesirable load for the amplifier.

Upgrade. Configuring new crossovers.

As I have already mentioned, the acoustic design is done correctly, so we will only upgrade the crossovers. The only thing that had to be adjusted in the acoustic design – is to reduce the amount of sound-absorbing material that was in the box in excess. That allowed to remove a small slope of the frequency response +2 dB from 60 to 200 Hz.

Characteristics of speakers with new filters:

Frequency response
Frequency characteristics of filters and impedance

The final version of the crossovers is configured as follows: the low-pass low-pass filter of the 2nd order, the high-pass high-pass filter of the 3rd order. The distribution frequency is 2.6 kHz.
Several variants of filters with different orders and frequencies were tested. According to subjective estimates, the version with the lowest possible split frequency and the 3rd order filter for the high-frequency driver won.
The low-pass filter has characteristic inclinations: -1.5 dB around 1 kHz and +1 dB around 2.2 kHz. This characteristic of the filter is not accidentally made, it “mirrors” the behavior of the frequency response of the speaker, which together gives an equal frequency response at medium frequencies. The HF filter has a similar character (with a slope of +1 dB at the cutoff frequency), which together provides a seamless transition of characteristics from the MF to the HF speaker and a uniform and wide distribution of sound.
Other lower-order filters with a higher distribution frequency provided a uniform frequency response along the acoustic axis, but a worse pattern of sound propagation with a tilt from the speaker in the vertical plane, which was somewhat uncomfortable.
The final version of the filters has a smooth diagram of sound distribution and almost the same tonal balance for the sitting position of the listener and for the standing position. What is important for comfortable listening and placement of speakers in the room.

New version of crossovers for ASW Varius Mod. 1

The new crossovers use Vajd Audio inductors (made to order), JB jfx and Monacor MKT capacitors, low-inductance wirewound resistors.
Structurally, the crossover boards are divided into HF and LF sections and are located in 2 tiers to fit in the intended mounting locations of the original filters. The option of separate connection of speakers according to the bi-wiring or bi-amping scheme is left.

The overall sound of these speakers with the new filters is definitely more complete thanks to a more uniform frequency response and a restored mid-frequency range that has been “suppressed” by standard filters.

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