Hi everyone .
I have read the web page below
https://www.caninialtoparlanti.it/nocrossover_.htm
it is written in Italian but if you use the translator you can understand it quite well.
I don't know if the metal basket has a function or if it only serves as a container for the glass wool.
I am interested in creating something else , a mechanical band - pass filter for a fairly limited portion of frequencies , for example , from 100 Hz to 300 Hz . what I would like to do however is not the complete elimination of the remaining frequencies but only a slight attenuation with respect to the frequency range that I want to pass.
in my case it would not be used to make a crossover but to modify the frequency response of the cabinet. could it work?
bye thank you
I have read the web page below
https://www.caninialtoparlanti.it/nocrossover_.htm
it is written in Italian but if you use the translator you can understand it quite well.
I don't know if the metal basket has a function or if it only serves as a container for the glass wool.
I am interested in creating something else , a mechanical band - pass filter for a fairly limited portion of frequencies , for example , from 100 Hz to 300 Hz . what I would like to do however is not the complete elimination of the remaining frequencies but only a slight attenuation with respect to the frequency range that I want to pass.
in my case it would not be used to make a crossover but to modify the frequency response of the cabinet. could it work?
bye thank you
I looked at the figures from the link, and I am very, very skeptical. For example, Figure 6 seems to be "doctored" frequency response, not an actual measurement. It is impossible forsuch a simple sound absorber (glass wool in a wire-mesh cylinder) to has no absorption at all at 3 kHz, and immediately after that - huge absorption at 3.5 kHz!
You are asking for a "mechanical band-pass filter", but you want "slight attenuation" (BTW, how many dB is that?) outside of the 100-300 Hz band, so in that case it looks more like PEQ equalizer, than "band-pass" filter, isn't it?
Because sound absorbers can do the attenuation only, your mechanical filter must attenuate all frequencies above 300 Hz (which can be done - sort of) and below 100 Hz - which is impossible!
Maybe I can give better advice if you clearly describe the problem, with more details.
You are asking for a "mechanical band-pass filter", but you want "slight attenuation" (BTW, how many dB is that?) outside of the 100-300 Hz band, so in that case it looks more like PEQ equalizer, than "band-pass" filter, isn't it?
Because sound absorbers can do the attenuation only, your mechanical filter must attenuate all frequencies above 300 Hz (which can be done - sort of) and below 100 Hz - which is impossible!
Maybe I can give better advice if you clearly describe the problem, with more details.
I've successfully used discs of wool and other dampening material in front of cone drivers to dampen or absorb resonances from specific parts of the cone and/or dust cap. It can be very effective and easy to implement, placing the material on the grill surface or suspending it by means of a metal or wood bridge.
The main MF and HF breakup offenders I see on larger cone drivers is the dust cap. The smaller it is, the better IMHO. Some people believe a good midrange driver uses a larger dustcap, which supposedly helps with MF dispersion, but the tradeoff with these dustcaps tends to be earlier midrange breakup. Its sort of like dealing with a large midrange dome with no cavity dampening (not good). This is why many pro sound drivers tend to be rough in the mids when the LP filter is pushed higher up. The lower Mms is, the worse the breakup tends to be, but the paper (diaphragm) composition can make a significant difference if its internal losses are optimized. A small disc may be all thats needed to reduce HF beaming or on axis peaks.
Cone edge resonance modes can also be treated with rings of dampening mounted in front of the cone edge. Experimentation is needed to obtain the best results. Sometimes a combination of discs and rings are needed.
The main MF and HF breakup offenders I see on larger cone drivers is the dust cap. The smaller it is, the better IMHO. Some people believe a good midrange driver uses a larger dustcap, which supposedly helps with MF dispersion, but the tradeoff with these dustcaps tends to be earlier midrange breakup. Its sort of like dealing with a large midrange dome with no cavity dampening (not good). This is why many pro sound drivers tend to be rough in the mids when the LP filter is pushed higher up. The lower Mms is, the worse the breakup tends to be, but the paper (diaphragm) composition can make a significant difference if its internal losses are optimized. A small disc may be all thats needed to reduce HF beaming or on axis peaks.
Cone edge resonance modes can also be treated with rings of dampening mounted in front of the cone edge. Experimentation is needed to obtain the best results. Sometimes a combination of discs and rings are needed.
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OK. Mechanical filter is not possible here below 100 Hz, but above 300 Hz you can try with a layer of damping material applied at back side of the front baffle, while keeping the opening clear.
If you want a mechanical bandpass filter from 100-300Hz there are these things called "bandpass" alignments. Very common and there is mechanical filtering for some types due to how the driver is used inside a box, playing into another box, that is then vented. Some basic info here:
https://www.diysubwoofers.org/bnd/
The downside of BR systems is worse transient response and some ringing compared to sealed or vented direct radiator systems.
https://www.diysubwoofers.org/bnd/
The downside of BR systems is worse transient response and some ringing compared to sealed or vented direct radiator systems.
I wonder what backs that claim up. Band pass alignments are acoustic filters. A good acoustics text book will tell you. Any acoustic filter, the versions with absorption material too, shows characteristics of (linear) filter topologies, including phase shift. It’s quite natural for any filter function to show effects on ‘transient response’ and ‘ringing’ or whatever. These are laws of nature, acoustic and electronic.
Sorry, to clarify I was thinking of BR systems compared to unfiltered vented or close box systems. The former has worse TR compared to the two latter ones. You are correct in that any mechanical filtering will also impact the transient response.
I've done the same unsuccessfully. 🙁 But maybe I wasn't going big enough. Sergio Canini is using a 12x8 cm fiberglass wool cylinder in front of an 8" driver.
Its a very fiddly process and time consuming to get it right. I'd rather describe it as more of a bandaid approach to taming a less than optimal driver that you're stuck with.
The dust cap area is the area on most drivers that behaves poorly higher up and its the component that gets the least amount of attention by designers. I have used thinned silicone to coat with some success but its a cautious process that can end up going backwards if you add too much mass. Sometimes it helps to replace the dust cap altogether and add some dampening behind it. Hard plastic dust caps are awful and point towards a poorly designed driver. Many fullrange drivers suffer from resonances behind the dust cap area. I used discs and rings of F10 felt to fix problems in this area.
Wizzer cones are bad news in most cases. They add fuzz up top and show many brand band breakup modes. Sometimes a ring of thinned RTV around the outside edge will tame them to a listenable point. Sometimes it helps to trim them shorter. Again a highly experimental and unpredictable process.
The dust cap area is the area on most drivers that behaves poorly higher up and its the component that gets the least amount of attention by designers. I have used thinned silicone to coat with some success but its a cautious process that can end up going backwards if you add too much mass. Sometimes it helps to replace the dust cap altogether and add some dampening behind it. Hard plastic dust caps are awful and point towards a poorly designed driver. Many fullrange drivers suffer from resonances behind the dust cap area. I used discs and rings of F10 felt to fix problems in this area.
Wizzer cones are bad news in most cases. They add fuzz up top and show many brand band breakup modes. Sometimes a ring of thinned RTV around the outside edge will tame them to a listenable point. Sometimes it helps to trim them shorter. Again a highly experimental and unpredictable process.
thank you all .
the article mentions three researchers who have published the results of their research in a famous magazine.
I'd like to know the theory behind how it works.
does anyone know anything about this? .
the article mentions three researchers who have published the results of their research in a famous magazine.
I'd like to know the theory behind how it works.
does anyone know anything about this? .
There has been much discussion of filter resonance in isolation without considering there are two ways in a crossover that bring you back to flat.
The article mentions several issues, which one are you asking about?
The article mentions several issues, which one are you asking about?
is there no relationship between basket shape and mesh size with roll-off frequency?. this thing reminds me of an aperiodic gate.