How to test frequency

[TwoCables]

 

I'm sharing this because I hope that I can cause someone else to decouple their subwoofer and hopefully get the same improvement.

I have a set of these, how do you decouple the sub? I have never heard of this.

 

 

Like I said, I used a soft and fluffy bath towel that I folded up into a square about the size of the subwoofer. There are products out there that are specifically designed for this, but I had this bath towel to use so I used it and I wouldn't be a bit surprised if I am getting the exact same results that one would get from a specially-designed product.

 

The whole idea is to find a way to prevent the subwoofer's cabinet from vibrating the floor. The name of the game is "isolation". With the subwoofer sitting directly on the floor, it's coupled with the floor. So, the term most widely used is "decouple".

Edited June 13, 2016 by TwoCables

[RoboKlipsch]

As a rookie I made this discovery also after doing some reading.  I actually used an entry mat, folded over, and have done so for both my subs on the hardwood floor in the main room.  It made a world of difference, no doubt!

[Paducah Home Theater]

My bucket list has a new item on it now:

 

Create a sound system that is capable of vibrating my body so much that I end up feeling nauseous!

160 db in a vehicle will just about do this. That's about what it takes though. Kind of a difficult task in a house.

[Paducah Home Theater]

I have never figured out how you know what exact frequency your sub is playing and where it cuts out.

Like Derrick said, only way to know this is with REW and OmniMic. To be more specific, go buy a UMIK-1 microphone, preferably from Cross Spectrum at the link below, since they calibrate it lower, then download REW. You'll choose to measure, then it will do a sweep. You can do it at a set SPL if you're trying to make the response flat, or you can put it full steam ahead.

http://cross-spectrum.com/measurement/calibrated_umik.html

http://www.roomeqwizard.com/

An example of the result of which for my room is shown below. It's usually much flatter but I cranked it as high as I could on this one and the soft limiters were kicking in down low. This wasn't with the calibrated SPL, I manually matched some levels, most likely it's a little low. On this setup, even if I turn it down, there is a weird null at 12 hz but then it comes back up at like 10 hz but is 3 db down, falls off again maybe at 7 or so. So if I were to say that I'm flat to 12 hz, I'm basing that off of these charts, not a youtube video or anything like that.

Edited June 13, 2016 by MetropolisLakeOutfitters

[derrickdj1]

The bath towels or rugs under a sub don't actually decouple the sub.  They may minimize floor vibration and change the floor bouce from the subwoofer.  You truly can't decouple a subwoofer due to the long wave lengths.  This is why you can hear the car going boom way down the street or piss off neighbors.  The long wave lengths will go thru floor, doors,window and walls.

Edited June 14, 2016 by derrickdj1

[dtr20]

I'm sharing this because I hope that I can cause someone else to decouple their subwoofer and hopefully get the same improvement.

I have a set of these, how do you decouple the sub? I have never heard of this.

Like I said, I used a soft and fluffy bath towel that I folded up into a square about the size of the subwoofer. There are products out there that are specifically designed for this, but I had this bath towel to use so I used it and I wouldn't be a bit surprised if I am getting the exact same results that one would get from a specially-designed product.

The whole idea is to find a way to prevent the subwoofer's cabinet from vibrating the floor. The name of the game is "isolation". With the subwoofer sitting directly on the floor, it's coupled with the floor. So, the term most widely used is "decouple".

Sorry, I didn't realize that was decoupling a subwoofer. It sounded more technical than just that (thought it involved working on the amp or something).

[TwoCables]

As a rookie I made this discovery also after doing some reading.  I actually used an entry mat, folded over, and have done so for both my subs on the hardwood floor in the main room.  It made a world of difference, no doubt!

 

Yep! I don't know how to describe it, but I'm definitely not going to back to having my subwoofer be in direct contact with my floor.

 

 

My bucket list has a new item on it now:

 

Create a sound system that is capable of vibrating my body so much that I end up feeling nauseous!

160 db in a vehicle will just about do this. That's about what it takes though. Kind of a difficult task in a house.

 

 

Oh, then I need to update that to include accomplishing it a house. Or, in an apartment, with an added mega bonus if I don't get thrown out! hehe

 

The bath towels or rugs under a sub don't actually decouple the sub.  They may minimize floor vibration and change the floor bouce from the subwoofer.  You truly can't decouple a subwoofer due to the long wave lengths.  This is why you can hear the car going boom way down the street or piss of neighbors.  The long wave lengths will go thru floor, doors,window and walls.

 

I know it's not technically and actually decoupling it. I mean, I know that that actual decoupling would require levitation or hanging the subwoofer from something that isn't connected to the structure of the house in any way. So, I was just speaking in practical terms, which I think is the way everyone is speaking when they talk about decoupling the sub from the floor.

 

 

 

 

I'm sharing this because I hope that I can cause someone else to decouple their subwoofer and hopefully get the same improvement.

I have a set of these, how do you decouple the sub? I have never heard of this.

Like I said, I used a soft and fluffy bath towel that I folded up into a square about the size of the subwoofer. There are products out there that are specifically designed for this, but I had this bath towel to use so I used it and I wouldn't be a bit surprised if I am getting the exact same results that one would get from a specially-designed product.

The whole idea is to find a way to prevent the subwoofer's cabinet from vibrating the floor. The name of the game is "isolation". With the subwoofer sitting directly on the floor, it's coupled with the floor. So, the term most widely used is "decouple".

Sorry, I didn't realize that was decoupling a subwoofer. It sounded more technical than just that (thought it involved working on the amp or something).

 

 

It's all good. I agree that it sounds technical because I think the word "decoupling" sounds more like a way to describe some sort of work on some kind of an electrical system. Like a Bypass surgery for electronics maybe. lol I think from now on, I'm going to come up with my own way to describe it.

Edited June 13, 2016 by TwoCables

[dtr20]

So question, when you guys use tone generators with computers hooked up to the avr, how do you hook it up? I'm using a laptop, hooked up via 3.5mm to composite cable, and that gets me poor results. The "40hz" comes out of my fronts even though I'm crossing over at 80hz. Should I be trying to hook this up via HDMI or do I need a special DAC to test properly? Thanks

[CECAA850]

How is your composite input configured in your AVR?

[wvu80]

So question, when you guys use tone generators with computers hooked up to the avr, how do you hook it up? I'm using a laptop, hooked up via 3.5mm to composite cable, and that gets me poor results.

 

The "40hz" comes out of my fronts even though I'm crossing over at 80hz.

 

Should I be trying to hook this up via HDMI or do I need a special DAC to test properly? Thanks

 

There are technical people here who can answer better than I can, so please take what I say with a grain of salt.

 

No matter what crossover you choose it is not a hard line that cuts sound off at the 100% level.  Even though you set the XO at 80 Hz it does not surprise me that a 40 Hz tone would come through.  What it won't do is come through "loud."

 

I have a sub with a Yung SD 500 plate amp that has a high-pass filter that is factory set to 30 Hz but with a frequency sweep video I can still hear a 20 Hz note.  It's not loud but I can clearly hear it, assuming the Youtube vid is accurate.

 

I apologize for the lousy explanation but I think what I trying to convey is generally true.

Edited June 22, 2016 by wvu80

[Ski Bum]

So question, when you guys use tone generators with computers hooked up to the avr, how do you hook it up? I'm using a laptop, hooked up via 3.5mm to composite cable, and that gets me poor results.

 

Using your laptop's headphone output as you are involves extraneous DA conversion and gain stages in the signal path.  Use a digital out from the computer directly to the AVR if possible.  If you can't do that, burn the test tones to disc and play via cd/blue ray player, or put them on a usb thumb drive and play through usb input on the AVR.   

 

The "40hz" comes out of my fronts even though I'm crossing over at 80hz.

 

The high pass filter is not a "brick wall" filter (one that completely eliminates output below the hpf setting), but rather produces a gradual roll-off below the hpf setting.  What is the slope of the filter?  Assuming the typical 80 hz hpf with a 24 db/octave slope, the mains would be down 24 db at 40 hz.  If the slope is only 12 db/octave, they would be down 12 db at 40.  Your room will have a large influence down here, so your sweeps may indicate more output than the calculations suggest (room mode at mic's position, or overall cabin gain in the lowest octaves). 

[mustang guy]

Dave and Skibum are right. Even an extreme 24db / octave slope would let a lot of that 40Hz through.

 

You can go from your computer to your sub directly. That's what I do when I am isolating frequencies. You just need a patch cord that goes from headphone to RCA. The only two ways you can isolate a sound to a sub in an AVR that I know of is to master a DVD or video file to Dolby D or DTS and record on the LFE channel. The DAC should send the LFE to the sub only. The other is the speaker test function when you are setting gains manually.

Edited June 23, 2016 by mustang guy

[dtr20]

You can go from your computer to your sub directly. That's what I do when I am isolating frequencies. You just need a patch cord that goes from headphone to RCA.

That's an awesome idea, I never thought of that. Thanks

Sent from my SM-G920V using Tapatalk

[RoboKlipsch]

On ebay i also see test tone discs from Dayton selling for $5 which is a good option if u dont want to make those connections

[dtr20]

So I hooked up my laptop directly to my definitive technology 18 sub. Using the test tone websites, I got movement on the sub all the way down to 8 hz (barely). So I'm not sure if the onboard sound card doesn't work properly, or this is normal. Volume is louder between 15-20 hz.

[TwoCables]

So I hooked up my laptop directly to my definitive technology 18 sub. Using the test tone websites, I got movement on the sub all the way down to 8 hz (barely). So I'm not sure if the onboard sound card doesn't work properly, or this is normal. Volume is louder between 15-20 hz.

 

Then your onboard sound chip (it's not a card - everything is onboard in a laptop) probably has a frequency response that begins at around 15 or 20 Hz. The only way to know for sure is by looking at its specifications. If the specs aren't published, then they probably assumed that no one buying that laptop will care.

Edited June 29, 2016 by TwoCables

[mustang guy]

Sub amps in stand alone subwoofers have built in HPF to protect from over excursion at very low frequencies. For instance, my Promedia 5.1 in front of me barely makes a sound below 25Hz. You can send the signal, but the built in HPF just blocks most of it.

Edited June 29, 2016 by mustang guy

[TwoCables]

Sub amps in stand alone subwoofers have built in HPF to protect from over excursion at very low frequencies. For instance, my Promedia 5.1 in front of me barely makes a sound below 25Hz. You can send the signal, but the built in HPF just blocks most of it.

 

That's because the ProMedia 5.1's frequency response is 25Hz - 20kHz.

 

I own a ProMedia 2.1 system, and its frequency response is 31Hz - 20 kHz. As expected, it doesn't really do much when I set a tone generator below 31 Hz. My sound card is the X-Fi Titanium HD. When using a tone generator, I make sure I am doing the fairest test possible by using Audio Creation Mode with no audio enhancements enabled at all. It's just a pure DAC this way. If I use Entertainment Mode and start adjusting my bass and graphic equalizer, then I can get low-end response below 31 Hz with a tone generator, but it doesn't really have a pretty or pure sound. It's very fake. So, 31 Hz really is about as low as this sub can go, and I would say 25 Hz is really as low as yours can go.

Edited June 29, 2016 by TwoCables

[mustang guy]

 

Sub amps in stand alone subwoofers have built in HPF to protect from over excursion at very low frequencies. For instance, my Promedia 5.1 in front of me barely makes a sound below 25Hz. You can send the signal, but the built in HPF just blocks most of it.

 

That's because the ProMedia 5.1's frequency response is 25Hz-20kHz.

 

Correct, because of the built in HPF.  

[TwoCables]

 

 

 

Sub amps in stand alone subwoofers have built in HPF to protect from over excursion at very low frequencies. For instance, my Promedia 5.1 in front of me barely makes a sound below 25Hz. You can send the signal, but the built in HPF just blocks most of it.

 

That's because the ProMedia 5.1's frequency response is 25Hz-20kHz.

 

Correct, because of the built in HPF.  

 

 

If that's what dictates the frequency response, then ok. I'm just saying "frequency response" because I think that's more universally understandable. That's really the only way I've ever understood it.

Edited June 29, 2016 by TwoCables