Canton Ergo SC-L upgrade

The second pair of Canton speaker systems that visited my workshop.

Construction of Canton Ergo SC-L

3-way speaker systems with a pair of 8-inch woofers, one midrange and one tweeter.
The mid and high frequency drivers are identical to the drivers of the older Canton Ergo 120 DC speaker model
Enclosure has a bass reflex port on the front panel.


The character of the sound is also very similar to the Ergo 120 DC model – the classic U-shaped frequency response tuning.
Characteristics of speakers Canton Ergo SC-L with original crossovers:

Frequency response
Transfer functions of filters

Canton Ergo SC-L factory crossovers:

Crossover boards are quite well made, but in my opinion are a good example of over-engineering. In this case, the number of resistors present in each filter chain is impressive. From the point of view of tuning, this is a convenient way to adjust the characteristics of filters (within certain limits) without the need to change the ratings of capacitors or inductors. But the same transfer characteristics of the filters can be achieved by carefully selecting the ratings of the coils and capacitors without using an excessive number of resistors. And only if absolutely necessary, resistors should be introduced into the circuits when it is impossible to do without them. I personally like the approach without the use of unnecessary elements more. I prefer designing crossovers starting from simple schemes with gradual complication if these complications really improve the objective characteristics of the speaker system and the subjective perception of sound.

Upgrade and new version of crossovers

Characteristics after upgrade:

Frequency response
Transfer functions of filters

With the help of fine tuning of the new filters, a more uniform frequency response is formed, it does not have a dip in the middle frequencies and their negative slope (from the lower middle to the upper). The general uniformity of frequency response is +/- 2 dB in the range of 50 Hz … 16 kHz. With the factory setting of the filters, this figure was more than +/- 5 dB in the same frequency range.

Basic and assembly diagrams of new crossovers

The new crossover scheme is quite simple – it is a 2nd order filter on each of the drivers.
The “MF M” mid-frequency drivers and the “HF T” high-frequency drivers must be connected in opposite polarity to the “LF W” low-frequency drivers.
The presence of an L-pad made of powerful 20 W resistors in the filter circuit of low-frequency drivers “LF W” is due to the fact that the sensitivity of a pair of these drivers is higher than the sensitivity of the medium-frequency driver “MF M”.
The bi-wiring connection option is also preserved: the boards of low-frequency and high-mid-frequency filters are connected separately to the corresponding terminals.
New crossover boards are installed on the same fasteners as factory boards:

Crossover boards are accessed through the woofer openings.
I also recommend reducing the amount of sound-absorbing material inside the woofer box. Leave it located on the inner side and rear walls of the box and remove it in the area where the bass reflex port is located. The sound absorber actually blocks the operation of the port because of too many and close location. This will allow you to slightly expand the reproduction of low frequencies and add a feeling of deeper bass.

Sound after upgrade

Due to precise balancing of the frequency response, the characteristic coloring of the sound is minimized. Subjectively, the sound is perceived as more expressive, integral, emotional and at the same time comfortable for long-term listening.
The owner of these speakers sent me feedback after the upgrade:
“I like the sound! Became soft and enveloping you.”

Additional Information

Canton Ergo SC-L and Canton Ergo 91 DC speaker systems are built on the basis of the same drivers with the same layout in the cabinet and have the same acoustic design.
Marking of drivers according to the Canton catalog:
Bass – 5943/6685
Midrange – 5916
Tweeters – 5990

Crossovers designed for the Canton Ergo SC-L upgrade are suitable without changes for the Canton Ergo 91 DC upgrade

If you are the owner of these speaker systems and want to improve their sound quality, you can make crossovers according to my drawings, strictly following the element ratings and schematic diagrams. But if you don’t have the skills and tools to make crossovers, you can also order ready-made crossover boards and just need to install them instead of the factory ones in your Canton Ergo SC-L or Ergo 91 DC .
To order crossover boards or any questions, please contact me

Comments are closed.