Axiom Home Page Forums General Discussion Home Theater Port chuff from the EP350

I'm running an Onkyo DS797 receiver and no, it doesn't have the sub option you mentioned.
The sub is calibrated and the SPL didn't matter. I mentioned in the first post that i even turned down the gain to 10-15% and still heard chuff although a lesser amount. The only way to rid the chuff i've found is to turn down the settings below 0dB in the Onkyo bass management.
LOTR is one heck of a bass pumped movie.

Sorry to hear about your wife's crystal.

Thanx, the crystal will survive but I may not
LOTR certainly is pumped. As a matter of interest where is the volume setting on your sub at once you have calibrated the system?

Oddly enough the sub volume is set much higher than i thought i would ever have it, around the 40% mark (approx. 11 oclock on the dial). I've turned it down a touch since then.

I had a look at the settings on mine, they are about the same perhaps a little lower. I took the sub limit off last night and tried it again. An interesting thing happens, I can get the 350 to as you say give some port chuff, but the 175's do not, turning back on the sub limiting eliminated this. the best part is what happened next;
We then went over to my friends house; he has the B&W Nautilus 801's (they have 15" down firing subs in the base of the speaker tower), these are being fed by Krell 700CX amplifiers. At Reference level (0db) the 801's subs clipped. You know I don't feel so bad now that I see a pair of $12,000.00 speakers doing the same thing. i think that this DVD will push a lot of peoples sytems harder then they ever thought possible.

Thanks for the info.
I don't have any local friends with big systems for comparison (just one stereophile friend who lives only for stereo sound...subwoofers are apparently blasphemy).

I knew the LOTR would push the system based on everyone's descriptions but i never expected that much chuff. I will just have to manage it for now.

At least i have a new reference DVD for testing heavy bass when looking into newer components!
I can't wait for the next release!!

Sorry to revive this old thread but I was hoping to read some comments from Axiom. Do they intend to revisit their subwoofer design/specs to address this port chuff or have they determined that their EP series are optimally configured to meet almost all subwoofer needs. This of course will not include demands from "extraordinarily out of whack" DVD's like Lord of the Rings, etc. Or maybe the problem is not the subwoofer but something else.

Comments please

I spent the last 10 minutes trying to find a definition of "port chuff" on google to no avail. Can someone educate my ignorant self?

It's port noise complaint. At certain extremely bassy moments, the air flow from the port creates an audible "chuffing" noise.

Hello JohnK,

LOL on your play on words on the Philip Roth novel. Your workmanship in the photos of your installation is excellent. I note that you have one or two mega-CD changers. My CD collection is overflowing its racks so I'm contemplating a 300-disc changer. Have you found them reliable? Did you get one with a PC keyboard input so you can name the discs as you feed them into the beast? Do you find you can access a particular disc quickly enough?

thanks,

Well, i finally have an update on the EP350 port chuffing issue.
Although there are several reports of other subs and speakers making the chuffing noise during the LOTR goblin drum scene, i was still convinced that a solid speaker should be able to handle the bass.

The general setup:
System
Axiom M60s
Axiom VP150
Axiom QS8s
Axiom EP350
Second sub (see below)
Onkyo DS797 receiver
Panasonic CV52 dvd
12awg speaker cable (Ultralink 50cents/ft)
AR interconnects (mostly)

1. I played the Lord of the Rings (LOTR) -Balin's tomb scene where the goblin drums start banging
   
2. at the usual listening volume levels as before (Onkyo at 75 on the 0-100 scale)
3. EP350 gain at 10oclock mark and 55Hz frequency crossover
4. all speakers set to "large" (yes that's right, not all set to small, and no, there was no difference when speakers were set to small))
5. I double checked all my LFE settings on the dvd player and receiver to be sure nothing was being enhanced.
6. I calibrated the sound levels for all speakers and subs were hooked up via the R/L line-in tested with and without a line y-splitter (single rca or double rca line-in configurations were tested).
   

There were two things that i did.
First, i borrowed a friend's subwoofer for comparison to the EP350. It was necessary to see how much of the source material and system settings were involved in making the chuff noise as opposed to the specific design of the Axiom subwoofers. The borrowed sub was a Klipsch KSW200.
The KSW sub also produced port chuff, although less audible, during the LOTR drum test even though it had a substantially larger box and port size.



I then changed my receiver (Onkyo DS797) settings such that the bass limiter was in use, similar to what John Henderson had mentioned previously in this thread. The bass limiter certainly kept both subs from creating the port noise but it also reduced the amount of rumble throughout the room. I increased the bass limiter to a higher level and again, the chuff started to become more clear but still reduced.

Secondly, i added some speaker baffle material over the ends of the insides of the EP350 ports with elastic bands (a suggestion from the good folks at Axiom). You can see the port ends in the following image but without the added baffle (you can see the baffle normally used inside the EP350):



The new baffle coverings also helped to decrease the port chuff. I estimate about 80-85% of the chuffing was reduced and this is WITHOUT using the bass limiter of the receiver.

I ended up coming to these general conclusions:

1. the predominant cause of the heavy bass creating the chuff is still most likely source based (bass is mixed heavy on the LOTR dvd which is not anything new) however, BOTH subwoofers cannot completely handle this heavy bass output (on my system), and i still believe they should
2. the bonded terylene (baffle) has cut down the chuff output on the EP350 by at huge amount (maybe 80-85%) making the heavy bass scenes far more enjoyable to hear/watch than before.
3. the bass limiter settings are useful in controlling the port chuff but can diminish the subwoofer output to less than satisfactory levels
   

The terylene port covers have certainly made the EP350 better in its attempts to manage the heavy bass and now has the edge over the Klipsch with the terylene in place, but I have yet to try the same with the Klipsch for an equal comparison.

Do i still think this port chuff is a speaker design flaw?
To some extent, but certainly not limited to Axiom subs and seems to be a disadvantage of the ported design which i have not come across before.

I am happier knowing that the chuff is not specific to the Axiom sub itself though, so short of having auditioned many other subwoofers before buying and having tested them with this LOTR scene, i would never have known which sub brand could have caused the same problem anyway.
I don't really have many suggestions as to how this chuff could be fixed but to reduce the effect, the added port baffle covers certainly helped and the bass limiter settings in the receiver can also be used in controlling the noise although with more widespread limiation on the overall sub sound output.
My present choice is to leave the bass limiter at a higher setting and use the added baffle port covers, but up the subwoofer gain to the 11 oclock mark. So far the port chuff has been severely minimized while my basement drop ceiling still shakes and shivers nearly the same as before.
My dogs have certainly not noticed the difference. They go running to the front window everytime the goblins start up their banging.