# How can I remove lower frequencies whilst still hearing them

So the title is confusing but its the best way I can sum it up.

In short I’m creating haptic infused sound effects using the subpac which is essentially a subwoofer strapped to your back and converts lower frequencies into vibrations.

What I’m trying to achieve is a sound effect made up of 2 channels, auditory & haptical.

The auditory channel will feature the main sound e.g. explosion noise with both upper & lower frequencies present in the user’s headphones however the lower freqencies will be restricted to a minimum of 200 hertz.
The haptical channel will feature only lower frequencies from 200 hertz & below and won’t be influenced by any audio from the auditory channel.

For example if we represent lower frequenices with the letter L & higher with H

the auditory channel will be represented as LH and the low frequencies for example are equal to 4 bass drum kicks
The haptical channel will be represented as L and the low frequencies are equal to a rolling snare drum

Now the auditory channel will feature both the snare drum and bass drum but the snare drum will less audible through masking of the low audible sound produced from the lower frequency.

However the haptical channel will feature only the snare drum and will not be influenced by the bass drum’s frequencies allow the creating of a custom lower frequency creation in the sound effect that isn’t directly influenced by that of the auditory channel.

If its any more confusion I’ll do a small video showing a visual example to explain what I want to make.

If anyone able to help recommend steps I could take to achieve what I’m asking it would be greatly appreciated.

Is that the wrong way round?
Do you mean that the “haptical channel will feature only the bass drum and will not be influenced by the snare drum’s frequencies”?

No I was using it as a mere example ish. Basically

2 channels

lets say 3 objects of sound

high medium & low

in the auditory channel you can hear all 3 objects plus the low object from the haptical channel
However in the haptical channel you can only hear (feel) the low object but that low object bares no influence from high, medium & low objects used within the auditory channel.

What are you starting with? A stereo audio file that contains high medium and low frequencies all mixed together?

What do you want to end up with? A stereo audio file with high medium and low frequencies all mixed together in one channel, and low frequencies (below 200 Hz) only in the other channel?

The auditory channel will feature the main sound e.g. explosion noise with both upper & lower frequencies present in the user’s headphones however the lower freqencies will be restricted to a minimum of 200 hertz.
The haptical channel will feature only lower frequencies from 200 hertz & below and won’t be influenced by any audio from the auditory channel.

You are describing a [u]crossover[/u]. All 2-way or 3-way speakers have a crossover to send the low frequencies to the woofer and high frequencies to the tweeter, etc. Crossovers can either be active (powered low-level circuits before multiple amplifiers) or passive (simpler, non-powered filters between the amplifier and speakers). Home theater receivers have a special active crossover (optionally) to mix the bass from the 5 or 7 surround channels with the “point one” low-frequency effects channel, sending all of the bass to the subwoofer, while (optionally) filtering the bass out of the surround channels.

If you wanted to send the full frequency range to the headphones, you just need a low-pass filter (half of the crossover) on the “woofer” to filter-out the higher frequencies.

What kind of amplifier(s) are you using? If you are using a car stereo amplifier, you can get automotive active crossover, or you can get amplifiers with high & low pass filters built-in. You can also buy active car stereo crossovers, or a passive crossover, but I don’t think you’ll find a 2-way passive crossover at 200Hz, and I assume you want an active crossover so your “woofer” can use it’s own amplifier,

Note that this is all hardware. You could use filtering in Audacity to make 5.1 (or 2.1) channel files, but you’d need a 5.1 channel player of some kind, and I don’t think you want to carry around a home theater receiver in your backpack.

Yeah, that popped up almost immediately. What kind of amplifiers are you using? Do you want both volumes to go up and down with one knob?

I think much of this post is overkill. Feed wide-band sound everywhere. The woofer strapped to your back won’t respond to the higher frequencies and besides, you won’t hear them anyway because of auditory capture rules.

Koz

If you plan to use two different songs, then the rules change. Then you will need the fancy-pants crossovers, etc.

Koz

The piece of hardware I’m using at the moment to test my theory is the subpac m2 (See attached image below)

What this hardware does in a literal sense is a pure subwoofer. It will let you feel the bass but only on the lower frequencies. It doesn’t detect the higher frequencies. Typically 200 hertz and below works best for it. There is a small box that comes with it. a line in & a headphone port so it works like your home theater pack but of course lighter and you only have to rely on your headphones and wearing that backpack. The box also comes with a small knob which is used for changing the bass intensity should you want to get a stronger sense of force when feeling it.

The idea originally was to use a single song and manipulate it so you can hear the full frequency range in the headphones which could be achieved with a low-pass filter. But to also create an additional channel to that song whereby I could manipulate sine waves into creating a custom low frequency rhythm which wouldn’t necessarily be possible in the single song on its own. So this would mean I’d have to apply a high-pass filter to that channel so I only got to experience the that custom low frequency rhythm rather than the frequencies from the main song.

End product would of resulted in the combining of these channels, so possibly these would be 2 songs then I guess like you mentioned @Kozikowski, 1 using a low-pass filter & the other using a high-pass filter. but then combining the two so that you get the product.

Would you advise anything for me to look into. Or would a high-pass & low-pass filter with crossover suffice?

I’m still very new-ish to learning out Audacity’s features to do this type of stuff.

Why do you need to do anything in Audacity? From your description, it sounds as if the hardware provides all the necessary signal processing. Or am I missing something?