Help with fireplace rattle

[miked053]

Hello,
The biggest issue I have with my living room HT is my fireplace rattle with bass notes. It is a natural gas insert that has a flew running up and out the wall. It appears that the rattling is coming from the flew and top of the unit and I cannot prevent its rattle. Will making a bass trap that fits directly in front of the fireplace help block the bass or am I barking up the wrong tree? ANY suggestions welcome as I am out of ideas.
Thank you

 

[TLS Guy]

Hello,
The biggest issue I have with my living room HT is my fireplace rattle with bass notes. It is a natural gas insert that has a flew running up and out the wall. It appears that the rattling is coming from the flew and top of the unit and I cannot prevent its rattle. Will making a bass trap that fits directly in front of the fireplace help block the bass or am I barking up the wrong tree? ANY suggestions welcome as I am out of ideas.
Thank you

Resonance is a funny thing, and it is impossible to predict at long range where the problem lies.

Try moving the sub to see if you can alter standing wave resonances that are the route cause of the problem. Also Eq to the sub to control bass peaks will likely help.

I doubt tinkering with the fireplace will help, but you could put a sheet of plywood in front the the fireplace, before you use expensive brass to see if that could be a solution.

The other thing you could try is extending the flue pipe to change the resonant frequency of the flue pipe.

 

[miked053]

Resonance is a funny thing, and it is impossible to predict at long range where the problem lies.

Try moving the sub to see if you can alter standing wave resonances that are the route cause of the problem. Also Eq to the sub to control bass peaks will likely help.

I doubt tinkering with the fireplace will help, but you could put a sheet of plywood in front the the fireplace, before you use expensive brass to see if that could be a solution.

The other thing you could try is extending the flue pipe to change the resonant frequency of the flue pipe.

The sub is really in the only place it can be. After doing the "sub crawl" it is in the only place that gets full bass range to the seating area well and even still that's behind the av/tv stand cabinet.
Is there an easy way to eq the sub? I don't have room eq or anything else like that.
The fireplace is built into the wall with the flew behind it and through the brick so there is no way of modifying that at all
I did put the dogs 4" thick foam be in front of the fireplace and that seemed to really help but I think that muffled the rattle coming out rather than blocking the sub freq from getting in. That's were I got the idea of placing a sub trap in front of the fireplace.

 

[TLS Guy]

The sub is really in the only place it can be. After doing the "sub crawl" it is in the only place that gets full bass range to the seating area well and even still that's behind the av/tv stand cabinet.
Is there an easy way to eq the sub? I don't have room eq or anything else like that.
The fireplace is built into the wall with the flew behind it and through the brick so there is no way of modifying that at all
I did put the dogs 4" thick foam be in front of the fireplace and that seemed to really help but I think that muffled the rattle coming out rather than blocking the sub freq from getting in. That's were I got the idea of placing a sub trap in front of the fireplace.

The problem is you really don't know how the resonance is getting excited.

What receiver do you have? There is auto and manual Eq on most receivers.

 

[miked053]

The problem is you really don't know how the resonance is getting excited.

What receiver do you have? There is auto and manual Eq on most receivers.

I have an Onkyo TX-NR646 and a BIC pl-200 sub

 

[mtrycrafts]

...
I did put the dogs 4" thick foam be in front of the fireplace and that seemed to really help but I think that muffled the rattle coming out rather than blocking the sub freq from getting in. That's were I got the idea of placing a sub trap in front of the fireplace.

Not sure what that is you put in front of the fire place. Did it cover the whole fire place or just partially?
And, perhaps the foam lets the low frequencies go through, up the chimney and you hear the dampened effects.
One reason to try TLS Guys suggestion of plywood in front or even behind that foam blocking the fireplace. That should block most low frequency leaks and that is what you have to do, block it from getting into the fireplace.
A bass trap will allow low freq penetration of the material but when it comes out the back and into the fireplace, you will still have rattling.
The ply experiment is cheap.

 

[andyblackcat]

Thump the flue pipe, you might alter the angle or how its fitted its only got a little mm gab between pipe and what its resting against that is making the rattle sound, try thumping it may cure the issue.

Also heat expands and cold makes items shrink inwards so weather is gonna be a factor all year with changing things such as windows or doors that can even rattle with low sub bass tones.

One way check for resonance is using a sine wave frequency sweep ether a quick sweep or manual sweep one Hz at a time and at various volume fader levels SPL db of each and all speakers to see if you can detect an resonate noises in or around the home.

Don't play it at levels where its gonna do damage to the speakers care should be taken when doing this that you don't harm your hearing as some frequencies in your room will peak high and lesser in other areas of the room.

Free sine wave generator is level 1 It has basic 1/1 octave RTA/sound generator and oscilloscope ( use the 1/3 octave version that you have to pay for)
https://www.trueaudio.com/rta_down.htm

Also there is free REW that even comes with a kitchen sink fitted and the sound generator on its what I must use.
http://www.roomeqwizard.com/

 

[fuzz092888]

 

[andyblackcat]

A bit of flat plastic or cardboard stuffed in-between a gap or even some blu-tack works. I used blu-tack on the letterbox to prevent one side rattling due to a certain low frequency wavelength I think around 60 or 70Hz its been few years since I fixed it with blu-tack.

 

[miked053]

upon further testing it looks like there is a space on top of the insert that a blower fan could have been installed as an option but wasn't. What is there now is a series of metal baffles that do not appear to be screwed together and rattle like hell. I'm not even sure how to get the front face off of the unit to see how to remedy this so I'm thinking that a piece of plywood in front of the fireplace with some foam attached to the back end might shield the fireplace or block the rattling noise from coming into the room.

 

[andyblackcat]

upon further testing it looks like there is a space on top of the insert that a blower fan could have been installed as an option but wasn't. What is there now is a series of metal baffles that do not appear to be screwed together and rattle like hell. I'm not even sure how to get the front face off of the unit to see how to remedy this so I'm thinking that a piece of plywood in front of the fireplace with some foam attached to the back end might shield the fireplace or block the rattling noise from coming into the room.

Pictures of all this show pictures maybe one of us can find you a way of sorting it, but need pictures.