Slap echo

[ChrisH]

Before I begin the process of building a couple of subs, I would really like to sort out the slap echo that exists in my room. Can this be tackled easily with more absorption? Or is there another way to tackle this? Right now I have 8 GIK Soffit bass traps, 4 of them have bass limiters on them.

The echo presents itself a little above normal conversational tone. It makes it very difficult to take measurements, and in my listening only seems to screw with me when I'm listening to opera. I do have measurements if that would help just let me know what you'd want to see.

 

[Thomas savage]

Some pictures of you room might be helpful..I had slap echo for years, it's a royal pain in the arse

 

[amirm]

Slap echo occurs due to parallel surfaces bouncing the sound back and forth. Its frequency is fairly high so even rather thin absorption gets rid of it. You only need it on one surface by the way, not both parallel ones. For this reason, standard practice for wall treatment is to alternate the material on each wall. So a blank surface then absorber and the opposite on the other wall. That way you don't over absorb the room.

 

[ChrisH]

Here are some pics of my room. The room itself measures 16'x26'x8'. There is also a support post that is directly behind my main spot. My head is about 10"-12" away. I also have some measurements as well if that would be helpful.

http://imgur.com/a/CKpq5

 

[ChrisH]

Slap echo occurs due to parallel surfaces bouncing the sound back and forth. Its frequency is fairly high so even rather thin absorption gets rid of it. You only need it on one surface by the way, not both parallel ones. For this reason, standard practice for wall treatment is to alternate the material on each wall. So a blank surface then absorber and the opposite on the other wall. That way you don't over absorb the room.

That's kind of what I have now. I think my bulkhead is causing this echo and I do have absorption opposite it. You can actually get two different echos going at the same time in the room on either side of the bulkhead.

 

[amirm]

Here are some pics of my room. The room itself measures 16'x26'x8'. There is also a support post that is directly behind my main spot. My head is about 10"-12" away. I also have some measurements as well if that would be helpful.

http://imgur.com/a/CKpq5

Nice comfortable room! Measurements don't show slap echo easily but they would be good to know if your room is too dead to add more absorption.

Right now it looks like you have bookshelves on the back wall which is good enough to eliminate slap echo in that direction. I don't think you are getting slap echo from side walls (that is more of an issue for multi-channel).

 

[Thomas savage]

I just went round clapping my hands like a lunatic to diagnose the areas of my room that returned a unwanted echo or resonance.

It's most likely that beam is the main culprit as you already know, you could do with covering it worth something temporary and inexpensive to a. find out for sure and b. To inform the choice as to whether it's worth going native on it with room treatments or not.


It's a matter I'm guessing of finding a solution that's not going to give your better half grounds to divorce you sighting unreasonable behaviour .

I know there is noise cancelling plasterboard we use in communal areas on ceilings that might look ok and help you out..

http://www.british-gypsum.com/products/gyptone-quattro-41

Amir would know better than me if that would work tbh..

 

[ChrisH]

Nice comfortable room! Measurements don't show slap echo easily but they would be good to know if your room is too dead to add more absorption.

Right now it looks like you have bookshelves on the back wall which is good enough to eliminate slap echo in that direction. I don't think you are getting slap echo from side walls (that is more of an issue for multi-channel).

What kind of measurement would you like to see? Waterfall plot?

 

[ChrisH]

I just went round clapping my hands like a lunatic to diagnose the areas of my room that returned a unwanted echo or resonance.

It's most likely that beam is the main culprit as you already know, you could do with covering it worth something temporary and inexpensive to a. find out for sure and b. To inform the choice as to whether it's worth going native on it with room treatments or not.


It's a matter I'm guessing of finding a solution that's not going to give your better half grounds to divorce you sighting unreasonable behaviour .

I know there is noise cancelling plasterboard we use in communal areas on ceilings that might look ok and help you out..

http://www.british-gypsum.com/products/gyptone-quattro-41
View attachment 4040
Amir would know better than me if that would work tbh..

I'm quite sure it's the damned bulkhead. Actually, I can do whatever I wish in this room. The wife has the upper two floors, I get the basement. Perhaps some OC705 could do the trick too.

 

[Thomas savage]

Fair plan, looking at your room I can't see that making it dead..

 

[amirm]

What kind of measurement would you like to see? Waterfall plot?

RT60 or reverberation time. If you are using REW, please select Topt graph.

 

[ChrisH]

RT60 or reverberation time. If you are using REW, please select Topt graph.

 

[amirm]

Thanks. The common convention is to look at the amount at 500 Hz. Here yours is 0.3 seconds. The acceptable range is 0.2 to 0.5 with the latter range preferred for music and former for home theater/surround systems.

So while you can put some more absorption in there you will be making the room sound more dry and dead.

I never like to say this but maybe do as Thomas says and put a temporary towel or two on the walls and see how you like it before committing to commercial products.

 

[Thomas savage]

Thanks. The common convention is to look at the amount at 500 Hz. Here yours is 0.3 seconds. The acceptable range is 0.2 to 0.5 with the latter range preferred for music and former for home theater/surround systems.

So while you can put some more absorption in there you will be making the room sound more dry and dead.

I never like to say this but maybe do as Thomas says and put a temporary towel or two on the walls and see how you like it before committing to commercial products.

Could diffusion be used to combat this issue? Or rounding the surface of the beams?

Both possibly effective without dampening the room any further...

 

[amirm]

Yes, diffusion can be helpful in not making the room too dead but they cost more.

One thing about clapping test: you can't do the clapping yourself. You need to sit in your seat and have someone clap where the speakers are. If you clap yourself it means the speakers are sitting in your arm which is not the situation you want to simulate. Slap echo if it exists has a "zing" sound like you hear in empty staircases.

 

[Thomas savage]

Yes, diffusion can be helpful in not making the room too dead but they cost more.

One thing about clapping test: you can't do the clapping yourself. You need to sit in your seat and have someone clap where the speakers are. If you clap yourself it means the speakers are sitting in your arm which is not the situation you want to simulate. Slap echo if it exists has a "zing" sound like you hear in empty staircases.

Hey I wanted to make sure I had no slap echo anywhere in my room

If you do have a freind helping you with the clap test make sure they have known you for a good long time, else they will just think your totally bonkers and you will be excommunicated by the local community.

 

[dallasjustice]

Maybe there's a clap recording for lonely audiophiles with no friends?

Hey I wanted to make sure I had no slap echo anywhere in my room

If you do have a freind helping you with the clap test make sure they have known you for a good long time, else they will just think your totally bonkers and you will be excommunicated by the local community.

 

[ChrisH]

I'll just leave this here. Remember, before you start clapping with friends, make sure they have been tested!

 

[ChrisH]

Could diffusion be used to combat this issue? Or rounding the surface of the beams?

Both possibly effective without dampening the room any further...

This is what I was rolling around my head a bit. Diffusion as opposed to absorption. Perhaps I could fabricate something....

 

[ChrisH]

Yes, diffusion can be helpful in not making the room too dead but they cost more.

One thing about clapping test: you can't do the clapping yourself. You need to sit in your seat and have someone clap where the speakers are. If you clap yourself it means the speakers are sitting in your arm which is not the situation you want to simulate. Slap echo if it exists has a "zing" sound like you hear in empty staircases.

DIY is something I like, so I can build, or have something built.

I will have my Daughter come down and do some clapping for me later this evening.