Hello everyone,
I have a subwoofer 15" I made myself and use a BK sub amp, and want to reduce the quite dramatic room mode that is created.
I prefer the high level (signal from power amp) sound and am not that keen on using a DSP. I have an in room measured with REW software and can see a good solution for a high Q [5] notch filter at 32 Hz BUT how do I best make one?
The plots on REW are from a measured in room response and then with a filter added at 31.8 Hz at - 20 dB with a Q of 5.
I found this https://www.ti.com/lit/an/snoa680/s...047&ref_url=https%3A%2F%2Fwww.google.co.uk%2F old article but apart from that I am a bit lost.
Any ideas, I am not an electronics person by training or experience but can solder and am logical and practical. 🙂
Great!
I have a subwoofer 15" I made myself and use a BK sub amp, and want to reduce the quite dramatic room mode that is created.
I prefer the high level (signal from power amp) sound and am not that keen on using a DSP. I have an in room measured with REW software and can see a good solution for a high Q [5] notch filter at 32 Hz BUT how do I best make one?
The plots on REW are from a measured in room response and then with a filter added at 31.8 Hz at - 20 dB with a Q of 5.
I found this https://www.ti.com/lit/an/snoa680/s...047&ref_url=https%3A%2F%2Fwww.google.co.uk%2F old article but apart from that I am a bit lost.
Any ideas, I am not an electronics person by training or experience but can solder and am logical and practical. 🙂
Great!
Attachments
@tonescout
You're right, in order to attenuate the effect of room modes / resonances it is not necessary to go digital/DSP, despite DSP potentially simplifying the implementation.
I do have very well sounding experience with the use of analog parametric equalization (PEQ), in my case with a used Technics SH-9010. The offering of new analog equalizers ist rather narrow, the digital offering is broader.
Implementing a room mode attenuation is well supported by REW, it offers a function that "proposes" PEQ settings. With a digital system you would just dial the offerred values into a user interface, with an analog system the dialing scales do not offer the same accuracy, so measuring the achieved effect is even more advisable than in the digital case.
Hope this helps for a star.
Good luck,
Winfried
You're right, in order to attenuate the effect of room modes / resonances it is not necessary to go digital/DSP, despite DSP potentially simplifying the implementation.
I do have very well sounding experience with the use of analog parametric equalization (PEQ), in my case with a used Technics SH-9010. The offering of new analog equalizers ist rather narrow, the digital offering is broader.
Implementing a room mode attenuation is well supported by REW, it offers a function that "proposes" PEQ settings. With a digital system you would just dial the offerred values into a user interface, with an analog system the dialing scales do not offer the same accuracy, so measuring the achieved effect is even more advisable than in the digital case.
Hope this helps for a star.
Good luck,
Winfried
Here you'll find a Rod Elliot design that is quite flexible and adaptable to three frequencies. It's not fully parametric (Q can't be adapted) but it should serve you well enough.
Apart from that: room modes can and will ruin your low frequency reproduction, certainly when you use only one sub. Allen suggested the right thing, move the sub around if you mainly want to get the response straight at your listening chair. You will also have to deal with the suckout at 70+something Hz...
Apart from that: room modes can and will ruin your low frequency reproduction, certainly when you use only one sub. Allen suggested the right thing, move the sub around if you mainly want to get the response straight at your listening chair. You will also have to deal with the suckout at 70+something Hz...
@ tonescout:
Just to avoid potential surprise or disappointment: Having fixed Q (= Filterwidth) is a significant limitation from my experience, as it may lead to over- or undercompensation (i.e. uneven Frequency response) in the mode frequency's vincinity. "...good enough for your case...", with all due respect, is questionable advice in my view, as we don't know your room mode really and we do not know your objective and subjective expectation nor your own perception of "good enough".
Greetings,
Winfried
Just to avoid potential surprise or disappointment: Having fixed Q (= Filterwidth) is a significant limitation from my experience, as it may lead to over- or undercompensation (i.e. uneven Frequency response) in the mode frequency's vincinity. "...good enough for your case...", with all due respect, is questionable advice in my view, as we don't know your room mode really and we do not know your objective and subjective expectation nor your own perception of "good enough".
Greetings,
Winfried
Well I guess the only thinking I have which is biased and not based upon knowledge or direct empirical experience is that I would prefer NOT to have a DSP managing the equalisation.
However I have now deduced that I can internally in the sub amp take the output from the Sub-pre to a DSP and then feed the the sub-power and this would allow digital control of the equalisation. But I suspect loose something in the process. My brother is convinced that dsp on the sub is not detrimental but I prefer to keep processing to a minimum.
Thoughts?
That was kind of my hope. I have plenty of power in the sub amp (500W) and the 15" driver has a sensitivity of 96.6 dB/w
You could build this filter.
I have used it very succesfully in my system to suppress a few room modes.
Active Filters
I have used it very succesfully in my system to suppress a few room modes.
Active Filters
Fab, this is the model I have calculated the notes attached. That would work to get rid of the room mode mostly. I will keep noodling 🙂
Attachments
What I would do is the following, if you have the capability to use a DSP:
First I would use a DSP to find what are the proper values for frequency, Q and attenuation that give the best room response.
Then I would replace the DSP with an analog notch.
First I would use a DSP to find what are the proper values for frequency, Q and attenuation that give the best room response.
Then I would replace the DSP with an analog notch.
Yeah, I can do that I just don't know how to iterate to the right values without pure trial and error - guess I need to rewrite my equations from the frequency as a known etc.
Ok - so starting to make more sense when I play - R1 gives me the dB cut so I can play with that value in situ.
A question of ignorance what is the Op Amp in the diagram, how do I select this?
A question of ignorance what is the Op Amp in the diagram, how do I select this?
As ever, everybody is fixing with meticulous deep thought a problem that isn't defined.
The FR plot makes no sense to me. Something is wacky and it isn't just a room mode causing the bump.
B.
The FR plot makes no sense to me. Something is wacky and it isn't just a room mode causing the bump.
B.
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The room is 5.39m wide, 5.58m deep, and 2.95m tall and if you estimate the room mode in REW simulation it's pretty much at just over 31Hz ?
Near square rooms are of course worse for room modes.
Could this be something else, the 31 Hz is still a peak without the sub?