my subwoofer is chuffing- how do I fix it

clarkyb

Active Member
I wrote a post about this yesterday but it seems to have vanished

but google cache to the rescue and here is the post again:


Ok so after building myself a modest home cinema I was extremely happy with it, until I watched a movie and realized there was some serious chuffing going on

I use a macbook pro as a HTPC, and my amp is a denon 1910, speakers are some quite large technics speakers for the fronts, tibo edge mini for the rears, and an eltax centre, subwoofer is a powered yamaha from a home theatre package.

I tested this sub at my parents house with their yamaha 775 and it sounded great, no chuffing.
But when I took it over to my house and set it up I get chuffing- my dad's speakers are floor standers though so they can produce the bass without the sub needed, so perhaps i'm just asking too much from my subwoofer in my own set up, with smaller front speakers?

the subwoofer is on the front wall between the 2 speakers, 1/3 from the right wall and 2/3 from the left- it's front ported and facing into the room.

I set everything up with the audyysey mic, and the strange thing is that i only get chuffing when audyysey eq, and dynamic eq are enabled- turn those off and the chuffing goes away, although so does the bass- which leads me to believe the bass is just set too high for the subwoofer to handle (and that when the EQ is on, that's how it should sound- corrected for the room). But I can't live with the chuffing, nor can I live with turning down the bass. I guess a solution would be to:

A) buy a bigger/better subwoofer that can handle those low frequencies without chuffing
I was looking at a cheap paradigm model

B) move it into the corner to get more bass output, but I like where it is now aesthetically, and it sounds really good for music, not boomy at all- in fact it sounds fantastic! Moving the subwoofer would mean i'd have to buy a much longer sub cable though, and if the right solution was to buy a better sub in the same position, i'd rather save my money


It only happens with frequencies under 40hz, I used some test tones and between 20 and 28hz it chuffs a lot, and a little bit between 30 and 40, after 40 it's ok. In music it never goes this low, and in films it's rare but annoying, so I was thinking until I get a better/bigger sub I could just cut out the low frequencies. There's no filter options on the sub, but I figured out how to route the audio from my mac through a software EQ to take out all frequencies below 40hz- chuffing problem solved but unfortunately the DTS/DD coding gets screwed up when going through the EQ so it comes out as stereo. If there was a way to apply eq to the coded signal that would be perfect, but I suspect not and i'm not looking for a mac solution anymore as i'm building a windows based HTPC, but i'm still going to look for a software solution on windows, unless there is a pretty cheap external filter I could either make, or buy? But it would have to be very cheap as i'd rather save up for a better subwoofer. I tried stuffing with socks, but it still chuffs, just muffled...and it sounds even worse to be honest

after running it through the software EQ I honestly couldn't hear much difference in music or films between the normal, and the filtered signal (except that the chuffing vanished), so clearly my sub can't play those frequencies anyway and i'm way better off just removing them totally. I guess a bigger/better sub, that didn't chuff at those low frequencies would be noticeably better?

If I do get another sub though, I am quite concerned for how it will work with music, the yamaha does music so well, i'm concerned if I got a more 'cinema' style subwoofer, where the bass was much stronger, much deeper, that might be too much for music- so I could run 2 subwoofers, and have the new sub next to the sofa at the back of the room, turn it off for music, turn it on for extra bass in games and films? Or maybe a better sub would be much improved for music too, and I should forget/get rid of my old sub?
 

noiseboy72

Distinguished Member
Chuffing is normally the sound or too much air going through a port that is to small diameter - leading to the air turbulence you are hearing. The EQ is probably compensating for some roll off built into the sub to protect it from just this problem.

If you are DIY minded, you could try fitting a larger, longer port, but on budget box, this might be tricky and may just lead to further problems. Your best bet is to get a more powerful sub, but you could try putting the sib into a corner - thus gaining the corner loading effect, which will make it louder.

I have acoustic transducers - thumpers, built into my sofa, so even at moderate levels, the bass can quite literally be felt!! Not for music though, as this just feels odd, but for big action scenes, it is hard to beat. They are paired to a homemade 10" 1500W sub, tuned to 25 Hz, so no shortage of bass here :)
 

clarkyb

Active Member
thank you

i'm not sure I really want to be cutting into the sub, I think it would do more harm than good

good call about the eq compensating for the sub's internal high pass filter, that's 100% the issue. I wish there was a way of tweaking the odyssey EQ, seems silly that it's either off or on, with no controls...


so what I will try is corner loading it, but I don't want to hear a one note, boomy bass- especially as it's working so well for music at the moment

another idea i'm going to try is putting a hardware eq in line between the amp and sub, with a 50hz cut that i'll adjust until the chuffing is minimized. Maybe that will work out until

I found out that there is no way to apply EQ to a digital coded (DTS/DD) signal without decoding it first, which in my set up (mac) means stereo output over spdif- but, in my new HTPC (windows) there's an EQ built into the output but I guess it still wouldn't be able to decode, eq, and then re-encode to DTS on the fly, so as i'm building it has HDMI output I could decode in software, EQ and then send a decoded, EQ'd audio stream as 6 channel LPCM to the amp- which would have the same effect right?

Hardware setup would be easier though, as all my inputs would now be properly EQ'd.


accoustic transducers sound fun!
 

clarkyb

Active Member
ok I moved the subwoofer into the corner and re ran odyssey, the chuffing is reduced but it's still a problem, much reduced though

the solution to this problem is a 3db cut at 31.5hz, software EQ does this fine but only in stereo. I think a hardware EQ between the amp and sub is the solution, and to be honest a hardware EQ is probably a useful piece to have for the future.
 

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