[vwinter]

I read those quotes, wasn't entirely sure if the Tenore's setup was the same as the Sony as for the Tenore the vent is mention and the foam is covering the vent.  And this statement.


If you look at Rin's sony.  He's just changing the back area. Not sure where foam comes into play.

Gotcha.

What's actually interesting to me about all this is you have about three variables, a back vent (if any), volume of the rear cavity (maybe shape too but I don't know how much effect that would have), and dampening material.

Say you accurately vary the vent size and the dampening material to create a net zero change in airflow behind the driver, while amplitude of the low end might (probably will) stay the same, how would that change the perceived response of the low end?

 

[SilverEars]

Gotcha.

What's actually interesting to me about all this is you have about three variables, a back vent (if any), volume of the rear cavity (maybe shape too but I don't know how much effect that would have), and dampening material.

Say you accurately vary the vent size and the dampening material to create a net zero change in airflow behind the driver, while amplitude of the low end might (probably will) stay the same, how would that change the perceived response of the low end?

Good way to find out how much an affect the foam has is take it out, and measure before and after, or less reliable method of listening.  Anybody?  
 

 

[luisdent]

 

I read those quotes, wasn't entirely sure if the Tenore's setup was the same as the Sony as for the Tenore the vent is mention and the foam is covering the vent.  And this statement.


If you look at Rin's sony.  He's just changing the back area. Not sure where foam comes into play.

Gotcha.

What's actually interesting to me about all this is you have about three variables, a back vent (if any), volume of the rear cavity (maybe shape too but I don't know how much effect that would have), and dampening material.

Say you accurately vary the vent size and the dampening material to create a net zero change in airflow behind the driver, while amplitude of the low end might (probably will) stay the same, how would that change the perceived response of the low end?

 
There must be a proportional relativity to the size of the chamber (amount of air), the venting (amount of air allowed to easily exit) and damping material (also controlling airflow).
 
I would guess that a fully sealed chamber would equal the lowest amount of bass, if it is at a size where air can't easily move. In other words, even a fully sealed chamber would allow all the bass response possible if the chamber were the size of a water bottle or something, because the air would be able to leave the driver easily. But as it decreases in size it must reach a point where it prevents adequate airflow, almost creating a vacuum when the driver attempts to move away from the chamber. Thus the vent allows some airflow to allow the driver to move away from the chamber but requiring more pull from the driver resulting in low bass. With a bigger vent the drive can more easily pull away and push into the chamber allowing more bass response. The foam would be like a mini airflow control that isn't at drastic as a vent perhaps?
 
These are just theories, but it makes sense that it comes down to the driver being able to push air enough to generate bass.

 

[SilverEars]

Foam would restrict the amount of air in the back chamber, and also let the air in through the driver vent.  The material of the foam would take up space in the chamber which means less space for air in the chamber.  Even less with denser materials.  So, it's controlling how much air is available for driver to pull in through the middle vent.

 

[james444]

Without opening up a less bassy set, it's hard to make this statement, but it appears that a bassy set has what could be a small amount of foam behind the driver. This makes sense, and may bode well for the varying foam theory... no?

 
A smaller amount of foam, or a less carefully placed piece of foam, possibly leaving part of the vent uncovered. Honestly, seeing this small piece of foam just tucked in there between the cables and secured with a few drops of hot glue, I wouldn't be surprised at all if it turned out being the main cause for the observed bass variations.
 

  Back vent plate and front vent plate.  It's like a chastity belt to prevent dynamic driver mods.

 
<insert screwing joke here>

 

How did you open these? Are they permanantely damaged or can you put them back together?

 
Click here and here. They're still ok.
 

  Foam would restrict the amount of air in the back chamber, and also let the air in through the driver vent.  The material of the foam would take up space in the chamber which means less space for air in the chamber.  Even less with denser materials.  So, it's controlling how much air is available for driver to pull in through the middle vent.

The size of the foam piece is negligible compared to the size of the back chamber. But overall I agree with your post, it may well be there to restrict the back vent's air flow.

 

[MuZo2]

If bass can be fixed, more scary part is TTS. I guess thats not from cables but driver itself.

 

[SkiesOfAzel]

   
A smaller amount of foam, or a less carefully placed piece of foam, possibly leaving part of the vent uncovered. Honestly, seeing this small piece of foam just tucked in there between the cables and secured with a few drops of hot glue, I wouldn't be surprised at all if it turned out being the main cause for the observed bass variations.

 
Don't keep us in suspense, just put another material there and report the results. I am searching for different foam types as we speak 

.

 

[vwinter]

Don't keep us in suspense, just put another material there and report the results. I am searching for different foam types as we speak  .

I don't remember where I read this but if iirc they make specific foams for audio applications with different impedances, so maybe look into that route?

 

[SkiesOfAzel]

I don't remember where I read this but if iirc they make specific foams for audio applications with different impedances, so maybe look into that route?

 
Nah, that makes too much sense. This is like testing cpu thermal pastes. You know that toothpaste will probably underperform but you still have to try, you just can't help yourself.

 

[MuZo2]

I don't remember where I read this but if iirc they make specific foams for audio applications with different impedances, so maybe look into that route?

Do you mean acoustic filters used in CIEM ,they are used in front of BA drivers.

 

[SilverEars]

I don't remember where I read this but if iirc they make specific foams for audio applications with different impedances, so maybe look into that route?

You're referring to mechanical impedance used for filtering that is added to damp the high frequency output.  Shure 836 has such filters to affect highs like the ER4 does electrically with the resistor and also acoustic filters.  The foam on the backend is for airflow and not acoustic flow.

 

[zest]

   
There must be a proportional relativity to the size of the chamber (amount of air), the venting (amount of air allowed to easily exit) and damping material (also controlling airflow).
 
I would guess that a fully sealed chamber would equal the lowest amount of bass, if it is at a size where air can't easily move. In other words, even a fully sealed chamber would allow all the bass response possible if the chamber were the size of a water bottle or something, because the air would be able to leave the driver easily. But as it decreases in size it must reach a point where it prevents adequate airflow, almost creating a vacuum when the driver attempts to move away from the chamber. Thus the vent allows some airflow to allow the driver to move away from the chamber but requiring more pull from the driver resulting in low bass. With a bigger vent the drive can more easily pull away and push into the chamber allowing more bass response. The foam would be like a mini airflow control that isn't at drastic as a vent perhaps?
 
These are just theories, but it makes sense that it comes down to the driver being able to push air enough to generate bass.

When you look at the chart of the MH1 mod, no rear volume means a cut-off frequency around 1.5 KHz, -2 dB at 500 Hz and -4 dB at around 300 Hz. When the chamber is totally open, bass is close to 0 dB, and sub-bass increase above 0 dB at 40 Hz.
 

 

[gnarlsagan]

So just to summarize: if I open my bass-light pair there should be more foam than on James' pair. I'd like to have a solid hypothesis before I go for it. Anyone care to add anything?

 

[vwinter]

Nah, that makes too much sense. This is like testing cpu thermal pastes. You know that toothpaste will probably underperform but you still have to try, you just can't help yourself.

LOL

Do you mean acoustic filters used in CIEM ,they are used in front of BA drivers.

You're referring to mechanical impedance used for filtering that is added to damp the high frequency output.  Shure 836 has such filters to affect highs like the ER4 does electrically with the resistor.  The foam on the backend is for airflow and not acoustic flow.

maybe I was combining things I'd read, but I know I read somewhere that speaker manufacturers use specific dampening materials specifically made for audio applications. Unless they wanna try something crazy lol, which is also awesome.

 

[MuZo2]

Yes, either more foam or more glue fix it.Which prevents the driver breathing more air.