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How to tell if low cut filter on dr60dmkii is working

edited September 2022 in Other

Hi,

I recently got a tascam dr60-d mkii recorder. I’m testing everything to make sure it’s working properly before my return period is up. This is a new product.

Everything seems to be working perfectly except for the low cut settings on the unit.

You can set the low cut for 40/80/120hz

My air conditioner return unit hums louder than it probably should, so I’m using that as a test. The low cut filter on the dr60 isn’t having any effect on cutting down the air conditioning hum. I can switch to all the various low cut settings while monitoring and I don’t hear much difference between any of the settings and no impact on the air conditioning hum.

What I can’t tell is if the hum is just too loud and possible over 120hz so the low cut isn’t having an effect? Or if it’s not working.

I’d hate to have to send this back for a replacement just for this one menu-driven feature that doesn’t appear to be working… when I’m not certain that it’s not.

Is there an easy test to confirm whether this low cut 40/80/120hz filter is working or not?

Comments

  • Record with and without the filter and the open the audio in an app that has a spectrum analyzer. If there is audio content in the range below the cutoff, you should see an obvious difference. It may well be that the bothersome noise is higher frequency than you realize.

  • edited September 2022

    @espiegel123 said:
    Record with and without the filter and the open the audio in an app that has a spectrum analyzer. If there is audio content in the range below the cutoff, you should see an obvious difference. It may well be that the bothersome noise is higher frequency than you realize.

    This is what I’m thinking. I don’t think I have a spectrum analyzer app. Are there any free ones? I did try that route but realized I didn’t have anything that monitors frequency like that on my devices

  • Auditor, the fabfilter eqs, there might by a TB spectrum analyzer, the blue mango oscilloscope has one, maybe the tb eqs also?

  • I think TB Spectrogram is free, and it has both spectrogram and analyser views.

  • if its in the electricity then it will be 60hz. But if its ambient noise coming from the actual unit then most likely it is almost all white noise which is balanced perfectly across the entire spectrum

    Cheers

  • Thanks!

    I tried loading a tone generator app on my iPhone. I set it for a sine wave at 40hz and held it to the mic until audible. Then tried the low cut settings. It very subtly reduced the sound when set at 120hz.

    So, I’m starting to think it’s working but it’s not as effective as I was expecting.

  • edited September 2022

    The slope of the filter is also worth to take in consideration, especially if it's an electronic circuit.
    See if you can get an app that does a frequency sweep from low to high, or record some sinus tones for all the filter settings
    Play it back with a spectrum analyser.
    Maybe a white noise signal could be used to see the behaviour of the filter.

  • edited September 2022

    @skiphunt said:
    So, I’m starting to think it’s working but it’s not as effective as I was expecting.

    You overestimate your ears ;)
    The filter slope isn‘t mentioned in the Tascam‘s spec sheet, but 6 or 12dB per octave are common values.
    For the 120 Hz setting this means a tone of 60Hz is attenuated to half or one quarter of it‘s original volume.
    120Hz is the cutoff point where the filter starts, it doesn‘t attenuate yet at this point.
    60Hz is one octave (half the frequency) lower.
    The human ear has fairly low sensitivity in this range.

  • @Telefunky said:

    @skiphunt said:
    So, I’m starting to think it’s working but it’s not as effective as I was expecting.

    You overestimate your ears ;)
    The filter slope isn‘t mentioned in the Tascam‘s spec sheet, but 6 or 12dB per octave are common values.
    For the 120 Hz setting this means a tone of 60Hz is attenuated to half or one quarter of it‘s original volume.
    120Hz is the cutoff point where the filter starts, it doesn‘t attenuate yet at this point.
    60Hz is one octave (half the frequency) lower.
    The human ear has fairly low sensitivity in this range.

    This is what I was mentioning to my wife last night, ie. that the filtering may be taking place, but that I may not be hearing it in that range.

    It seems like I should be able to hear some difference in average test recordings by turning the filter on and changing it's setting from 40 to 80 to 120hz. Yet, I hear almost no difference at all whether it's on or not.

    So, if it's not working... I'd return the unit for a replacement. However, I can't tell for sure if it's not working? Or, it's working but I'm simply not hearing what it's doing. I'm using Sony 7506 headphones and an AKG Perception 220 condenser mic.

    Is there a simple test I could do to verify whether or not the filter is actually working or not? That's my only goal at the moment, ie. to make sure everything is working correctly while it's still easy to return/exchange the unit.

  • edited September 2022

    It should be easy to check: the filter‘s main purpose is to reduce proximity effect, plosive noises and rumble from floor/mic stand.
    In an extreme close addressing you should hear the difference clearly, without a pop filter or tipping the mount by a pencil, stamp on the floor or similar stuff.
    Btw it‘s very (!) unlikely the filter itself is damaged. The only suspect part is the switch.

  • @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

  • edited September 2022

    @Telefunky said:
    It should be easy to check: the filter‘s main purpose is to reduce proximity effect, plosive noises and rumble from floor/mic stand.
    In an extreme close addressing you should hear the difference clearly, without a pop filter or tipping the mount by a pencil, stamp on the floor or similar stuff.
    Btw it‘s very (!) unlikely the filter itself is damaged. The only suspect part is the switch.

    There’s no switch. It’s menu activated. That’s why I’m doubtful that it’s not working. Yet, I hear no difference at all when it’s activated.

  • @espiegel123 said:
    @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

    Yes, I was just asking since I don’t honestly know how to identify by ear source content that has those frequencies in particular.

    Since it’s intended primarily to reduce hum of a fridge or wind noise, I may hook up a shotgun mic and take it out in the wind to see if I hear any difference with that particular use.

    Sorry if my asking if there’s any other test annoys you.

  • @skiphunt said:

    @espiegel123 said:
    @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

    Yes, I was just asking since I don’t honestly know how to identify by ear source content that has those frequencies in particular.

    Since it’s intended primarily to reduce hum of a fridge or wind noise, I may hook up a shotgun mic and take it out in the wind to see if I hear any difference with that particular use.

    Sorry if my asking if there’s any other test annoys you.

    No need to be defensive. It sounded like you were asking the same question as if the earlier answers weren’t good ones.

    It sounds like your question now is “what would be a good test sound”.

    What did the spectrum analysis of your recordings of the room without the filter look like ? Was there much frequency content below the cutoff?

    If there was content in your target range, that should be sufficient.

    You could generate sine waves at a few frequencies below the cutoff. As one possibility.

    As another, you could use a white noise generator.

    Check your sources by running them through a spectrum analyzer.

    My guess is that some of noise you want to filter out is higher frequency than you think.

    You can use a good eq to figure out what aspect of the noise is associated with what frequencies.

  • @espiegel123 said:

    @skiphunt said:

    @espiegel123 said:
    @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

    Yes, I was just asking since I don’t honestly know how to identify by ear source content that has those frequencies in particular.

    Since it’s intended primarily to reduce hum of a fridge or wind noise, I may hook up a shotgun mic and take it out in the wind to see if I hear any difference with that particular use.

    Sorry if my asking if there’s any other test annoys you.

    No need to be defensive. It sounded like you were asking the same question as if the earlier answers weren’t good ones.

    It sounds like your question now is “what would be a good test sound”.

    What did the spectrum analysis of your recordings of the room without the filter look like ? Was there much frequency content below the cutoff?

    If there was content in your target range, that should be sufficient.

    You could generate sine waves at a few frequencies below the cutoff. As one possibility.

    As another, you could use a white noise generator.

    Check your sources by running them through a spectrum analyzer.

    My guess is that some of noise you want to filter out is higher frequency than you think.

    You can use a good eq to figure out what aspect of the noise is associated with what frequencies.

    No, I wasn't asking the question again as if the previous ones weren't good ones.

    I had to wrap up my testing yesterday because my wife had other plans for us. Also, we have two cats. They are not declawed and they LOVE little wires, adapters, etc. - if they grab something and take a swipe at me trying to get it back... those claws are freaking sharp! I have to do the test very quickly while I have the cats corralled in another room.

    I was only asking about an easy-peasy quick way to tell if the filter is working without having to get everything out, connect the wires, make a recording, transfer recording to iOS device, then run through a spectrogram app.

    I was hoping for something like... turn on your bathroom fan and that should be in the right freq range... flip the filter a few times and you should be able to tell an obvious difference... or something like that. I wasn't dismissing your suggestion.

  • @skiphunt said:

    @espiegel123 said:

    @skiphunt said:

    @espiegel123 said:
    @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

    Yes, I was just asking since I don’t honestly know how to identify by ear source content that has those frequencies in particular.

    Since it’s intended primarily to reduce hum of a fridge or wind noise, I may hook up a shotgun mic and take it out in the wind to see if I hear any difference with that particular use.

    Sorry if my asking if there’s any other test annoys you.

    No need to be defensive. It sounded like you were asking the same question as if the earlier answers weren’t good ones.

    It sounds like your question now is “what would be a good test sound”.

    What did the spectrum analysis of your recordings of the room without the filter look like ? Was there much frequency content below the cutoff?

    If there was content in your target range, that should be sufficient.

    You could generate sine waves at a few frequencies below the cutoff. As one possibility.

    As another, you could use a white noise generator.

    Check your sources by running them through a spectrum analyzer.

    My guess is that some of noise you want to filter out is higher frequency than you think.

    You can use a good eq to figure out what aspect of the noise is associated with what frequencies.

    No, I wasn't asking the question again as if the previous ones weren't good ones.

    I had to wrap up my testing yesterday because my wife had other plans for us. Also, we have two cats. They are not declawed and they LOVE little wires, adapters, etc. - if they grab something and take a swipe at me trying to get it back... those claws are freaking sharp! I have to do the test very quickly while I have the cats corralled in another room.

    I was only asking about an easy-peasy quick way to tell if the filter is working without having to get everything out, connect the wires, make a recording, transfer recording to iOS device, then run through a spectrogram app.

    I was hoping for something like... turn on your bathroom fan and that should be in the right freq range... flip the filter a few times and you should be able to tell an obvious difference... or something like that. I wasn't dismissing your suggestion.

    I have suggested a few options. Perhaps, not clearly enough. Use your iPad (or computer) to generate some sine waves below the cutoff or some noise. Record that into your new recorded with and without the filter. Open the created files on your iPad or desktop and run them through a spectrum analyzer or in an audio app that has a spectrum view. It should be immediately apparent from looking at the two files whether the low cut is doing anything.

    Make sure that the unfiltered signal that you will use has content in the frequency range of interest.

  • No need for spectrum analysis, you can tell by level if the filter worked or not.
    Just mumble some words 1“ from the capsule ;)

  • edited September 2022

    @espiegel123 said:

    @skiphunt said:

    @espiegel123 said:

    @skiphunt said:

    @espiegel123 said:
    @skiphunt : we’ve already told you a test . Find a source signal with content in the frequency range of interest. Record it with and without the low cut filter. Examine the recordings with a spectrum analyzer.

    Yes, I was just asking since I don’t honestly know how to identify by ear source content that has those frequencies in particular.

    Since it’s intended primarily to reduce hum of a fridge or wind noise, I may hook up a shotgun mic and take it out in the wind to see if I hear any difference with that particular use.

    Sorry if my asking if there’s any other test annoys you.

    No need to be defensive. It sounded like you were asking the same question as if the earlier answers weren’t good ones.

    It sounds like your question now is “what would be a good test sound”.

    What did the spectrum analysis of your recordings of the room without the filter look like ? Was there much frequency content below the cutoff?

    If there was content in your target range, that should be sufficient.

    You could generate sine waves at a few frequencies below the cutoff. As one possibility.

    As another, you could use a white noise generator.

    Check your sources by running them through a spectrum analyzer.

    My guess is that some of noise you want to filter out is higher frequency than you think.

    You can use a good eq to figure out what aspect of the noise is associated with what frequencies.

    No, I wasn't asking the question again as if the previous ones weren't good ones.

    I had to wrap up my testing yesterday because my wife had other plans for us. Also, we have two cats. They are not declawed and they LOVE little wires, adapters, etc. - if they grab something and take a swipe at me trying to get it back... those claws are freaking sharp! I have to do the test very quickly while I have the cats corralled in another room.

    I was only asking about an easy-peasy quick way to tell if the filter is working without having to get everything out, connect the wires, make a recording, transfer recording to iOS device, then run through a spectrogram app.

    I was hoping for something like... turn on your bathroom fan and that should be in the right freq range... flip the filter a few times and you should be able to tell an obvious difference... or something like that. I wasn't dismissing your suggestion.

    I have suggested a few options. Perhaps, not clearly enough. Use your iPad (or computer) to generate some sine waves below the cutoff or some noise. Record that into your new recorded with and without the filter. Open the created files on your iPad or desktop and run them through a spectrum analyzer or in an audio app that has a spectrum view. It should be immediately apparent from looking at the two files whether the low cut is doing anything.

    Make sure that the unfiltered signal that you will use has content in the frequency range of interest.

    Well, I figured it out. The low cut filter is working perfectly.

    The quick and easy method I came up with confirmed it without any recording files, having to transfer, then run through any analyzer.

    Since the stated purpose of this low cut filter in the manual is to cut down on noises like wind noise, a fridge hum, etc. I simply blew air consistently into the attached condenser mic until I could monitor a low wind-noise hum. While doing this I turned on the low cut filter and tried all the settings. It cut the wind hum I was making completely out to obviously to confirm it was indeed working.

    I decided to try the more techy method too. The DR60DMKII has line out. I set up a small fan on the mic so that it had consistent wind noise hum. Then I ran the line out of the DR60D into my iPad and selected it as source in AUM. I loaded up TB Spectogram into the fx slot and then turned on the DR60D's low cut filter settings. I could clearly see within the TB Spectrogram display that those frequencies were being cut.

    Thanks to all who offered suggestions and details of how I could confirm this. I verified it's all working like it's supposed to.

    Cheers

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