Hi folks,
I like to start a discussion about what Canton calls "Displacement Control".
As far as I understand, this is basically just a passive high pass filter suppressing infra-sonic material.
The alleged benefit is clearer bass since the driver has less excursion in the infra-sonic range.
Canton's passive Reference speakers come with this feature for example.
I wonder how exactly the DC feature is implemented.
My guess is that this is just a first order high pass filter, i.e. a series capacitor.
According to some basic simulation in LT Spice, ~3300uF in series with the bass drivers could do the job.
Some decades ago, removing the output capacitor from solid state amplifiers was a major leap so adding back the (DC blocking) capacitor seems somewhat retrogressive.
On the other hand side, a loudspeaker would be more robust with such a DC capacitor added since DC from the amplifier can no longer destroy the bass drivers coil.
Looking at a (unfortunately low resolution) photo of the crossover, I can see an array of six capacitors on one of the PCBs.
Could be that those are for the DC feature?
Does anybody know something about the Canton implementation (since I'm only guessing)?
Do other manufacturers also use infra-sonic filters?
Does it make any sense in you opinion?
What are possible draw-backs?
I like to start a discussion about what Canton calls "Displacement Control".
As far as I understand, this is basically just a passive high pass filter suppressing infra-sonic material.
The alleged benefit is clearer bass since the driver has less excursion in the infra-sonic range.
Canton's passive Reference speakers come with this feature for example.
I wonder how exactly the DC feature is implemented.
My guess is that this is just a first order high pass filter, i.e. a series capacitor.
According to some basic simulation in LT Spice, ~3300uF in series with the bass drivers could do the job.
Some decades ago, removing the output capacitor from solid state amplifiers was a major leap so adding back the (DC blocking) capacitor seems somewhat retrogressive.
On the other hand side, a loudspeaker would be more robust with such a DC capacitor added since DC from the amplifier can no longer destroy the bass drivers coil.
Looking at a (unfortunately low resolution) photo of the crossover, I can see an array of six capacitors on one of the PCBs.
Could be that those are for the DC feature?
Does anybody know something about the Canton implementation (since I'm only guessing)?
Do other manufacturers also use infra-sonic filters?
Does it make any sense in you opinion?
What are possible draw-backs?
Attachments
Not really.
I'd just fab a 2nd order PLLXO for the input of the power amp if adding another active filtered buffer stage was an anathema. Having added HPFs to every ported build and many sealed, especially with an LT, the improvement in SQ from the reduction of unnecessary excursion from unwanted ULF greatly outweighs a filtered buffer.
Thanks for your input and confirming that a high pass filter is a good idea.
Did you implement PLLXOs or passive high pass filters into the speakers cross-over?
Active infra-sonic filters are common especially in PA equipment. I just was not sure whether this is also a good idea for domestic HiFi.
Is there a rule of thumb for the high pass cross-over frequency?
Is a first order high pass filter the right approach for the bass speaker cross-overs?
A second order filter for the speakers cross-over does not seem feasible due to the size of the inductor…
Having the option to bi-wire my speakers, should I add the high pass to the bass input only?
Sorry for dumb questions; I know little about loudspeakers and appreciate everything explained for dummies.
Did you implement PLLXOs or passive high pass filters into the speakers cross-over?
Active infra-sonic filters are common especially in PA equipment. I just was not sure whether this is also a good idea for domestic HiFi.
Is there a rule of thumb for the high pass cross-over frequency?
Is a first order high pass filter the right approach for the bass speaker cross-overs?
A second order filter for the speakers cross-over does not seem feasible due to the size of the inductor…
Having the option to bi-wire my speakers, should I add the high pass to the bass input only?
Sorry for dumb questions; I know little about loudspeakers and appreciate everything explained for dummies.
A P(assive) L(ine) L(evel) X (=cross) O(ver) is a solution that filters between the source and the power amp, not between the power amp and the speakers. More about it at this excellent site. Alternatively one could pick an active solution with just one opamp in the signal circuit. Considering the signal has passed hundreds of them before it reaches your speakers, no worries about sound degradation.
Either way, a highpass filter has to be adjusted to the highpass function of the speaker involved to work best. Allen mentioned the L(inkwitz) T(ransform) already, other and quite easy implementations are the B4 (closed) or B6 (ported) alignments. Very effective and in it's best with quite some low extension.
Either way, a highpass filter has to be adjusted to the highpass function of the speaker involved to work best. Allen mentioned the L(inkwitz) T(ransform) already, other and quite easy implementations are the B4 (closed) or B6 (ported) alignments. Very effective and in it's best with quite some low extension.
I ripped a flex wire loose in a 10" woofer by walking across the floor with the tonearm on the record. So yes, There is a use for high pass filter in home hifi. 1961 AR turntable didn't have enough suspension to eliminate wood floor bounce. I'd say 20 hz 3 db/octave is much better than nothing. PA use, some microphones pick up floor bounce, or hand held rumble (not SM58).
As my older amps have no transformer winding for op amp voltages, nor room to stuff extra boards in, I put 47 uf series the 8 ohm woofer. dynaco ST70, ST120, allen S100, Would be much more expensive for 4 ohm drivers. Home hifi won't put out over 22 vac so no need for 200 vac polyprophylene caps. 63 vdc is adequate. Historic preamps like the dynaco PAS2 cut bass much higher than 20 hz, too. Turning the "bass" control down on a 2 pot preamp is annoying on music .
Last edited:
PLLXO is done at line level.
Yes, they are an excellent idea and every ported system should have one.
I've been using active xovers for decades so I implement the HPF in DSP, but there are various active opamp or discret buffer options if you have DSP-phobia.
ROT is just below tune.
2nd order minimum.
Biwiring is a complete waste of time, effort and money.
Or don't bribe apple+google $30 a month to maintain a smart phone. Plus the $600 payment to a certain threatening supplier. Sole source of smart phones as far as I can determine.
Thanks everybody for your input, highly appreciated!
Seems like adding a high pass filter is not only a good idea, but also pretty common and best implemented on line level where it is also easy to design a steep high order filter. In the digital domain, this would also be very flexible in terms of frequency and filter order.
The main benefit of a passive speaker level high pass would be a fool proof protection of the bass speaker regardless of any filters in the signal chain. Furthermore, the loudspeaker would survive an amplifier failure putting direct current at the speaker.
With a passive first order high pass filter at loudspeaker level, the trade off would be between rather low attenuation of the unwanted infra-sonic frequencies or unwanted attenuation of the lower bass region. Canton apparently found this a worthwhile addition to their more expensive speakers nonetheless.
My initial plan was to buy Canton Reference speakers, but they were out of stock so I got pretty similar ones (Vento 90) without the high pass (Displacement Control) feature.
The most appealing aspect of the high pass filter at loudspeaker level for me is immunity against amplifier failure. I build my own amplifiers (usually you find me in the solid state forum) and of course I also implement direct current protection, but in case both the amplifier and the direct current protection fail, my super expensive speakers would be toast.
I seriously consider the addition of a series capacitor as HPF as belt and braces approach to protect my speakers and like to make sure this does not have unforeseen side effects.
I don't know much about the Canton Vento 90 other than the cross-over to the mid-bass is around 200Hz.
From other (probably similar) Canton speakers impedance curve, I would guess that the impedance below port resonance could be around 3 Ohm maybe.
Thus with 3300uF as HPF, cross-over would be at 16Hz roughly.
At 200Hz, where the transition to the mid bass driver happens, there is still significant phase shift so probably I should put the capacitor in series with the whole speaker instead of just the bass drivers in order to avoid phase anomalies around the crossover frequency?
Does this make any sense to you?
Seems like adding a high pass filter is not only a good idea, but also pretty common and best implemented on line level where it is also easy to design a steep high order filter. In the digital domain, this would also be very flexible in terms of frequency and filter order.
The main benefit of a passive speaker level high pass would be a fool proof protection of the bass speaker regardless of any filters in the signal chain. Furthermore, the loudspeaker would survive an amplifier failure putting direct current at the speaker.
With a passive first order high pass filter at loudspeaker level, the trade off would be between rather low attenuation of the unwanted infra-sonic frequencies or unwanted attenuation of the lower bass region. Canton apparently found this a worthwhile addition to their more expensive speakers nonetheless.
My initial plan was to buy Canton Reference speakers, but they were out of stock so I got pretty similar ones (Vento 90) without the high pass (Displacement Control) feature.
The most appealing aspect of the high pass filter at loudspeaker level for me is immunity against amplifier failure. I build my own amplifiers (usually you find me in the solid state forum) and of course I also implement direct current protection, but in case both the amplifier and the direct current protection fail, my super expensive speakers would be toast.
I seriously consider the addition of a series capacitor as HPF as belt and braces approach to protect my speakers and like to make sure this does not have unforeseen side effects.
I don't know much about the Canton Vento 90 other than the cross-over to the mid-bass is around 200Hz.
From other (probably similar) Canton speakers impedance curve, I would guess that the impedance below port resonance could be around 3 Ohm maybe.
Thus with 3300uF as HPF, cross-over would be at 16Hz roughly.
At 200Hz, where the transition to the mid bass driver happens, there is still significant phase shift so probably I should put the capacitor in series with the whole speaker instead of just the bass drivers in order to avoid phase anomalies around the crossover frequency?
Does this make any sense to you?
Attachments
Using a capacitor in conjunction with a proprietary box alignment is fairly common actually. Called a QB3-alignment, KEF amongst others used this massively a few decades ago. The QB3 enables the same f-3dB in a smaller enclosur, compared to a normal closed box.
