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How do you tell the difference between port noise and bottoming out?

jhbodle

Standard Member
Hi,

Just testing my new BK Monolith DF with some test tones to see how to calibrate it. It's a bit of a baptism of fire for me as the only other sub i've ever owned was a tiny Monitor Audio ASW100 which had way less bass. Now when I play a movie the bass sounds immense but I don't know how loud I can push it because I don't know the sub's limits.

Playing a 20Hz test tone through the sub at over 80dB on my Arcam AVR250 amp generates distortion, but I think it may be coming from the port on the sub. The noise doesn't occur at 15Hz. Trouble is I don't know the difference in sound between bottoming the woofer and port noise. I could always tell when my ASW100 was being overdriven as it sounded like it was clipping, but this is a different kind of noise. I have the gain set at around 2 'o' clock on the BK.

Am I damaging the sub by running it this hard? The reason I have turned the gain up so much is that I want more bass in music at normal listening levels, but then when I play movies at higher levels I am worried this will now damage the woofer.
 

Badger0-0

Distinguished Member
You'll know if it's bottoming, trust me.
It'll sound like a thwack, literally like two solid objects are hitting each other.
I likened my monolith bottoming to two large stones being smacked together.

2 o'clock sound a bit high unless you have a very large room.
 

Member 639844

Former Advertiser
With ports you'll get either chuffing or resonances. Chuffing just sounds like wind noise puffing, like a steam train does but obviously a lighter sound from the sub. Resonances can be a couple of things. It can be a kind of ringy sound from the ports itself resonating, or it can be sounds created inside the sub resonating down the port. If the driver does bottom out, it's likey you'll be able to hear it quite loudly from the port itself, but this isnt a port issue, its just that the other end of the ports inside, is going to be near the back of the driver, where the bottoming out occurs.

Like Badger says, you'll know the difference!
 

jhbodle

Standard Member
Well it's definitely not 'thwacking', it does sound more of a chuffing sound as you describe. I hear that new Monoliths have a special filter so I can't really do much damage to it if I feed too much gain into it (ie overdrive it), is that correct?
 

Badger0-0

Distinguished Member
Yes, they do have a protection circuit now, I believe, so you should be ok :smashin:
 

jhbodle

Standard Member
Excellent, cheers guys!

I keep pushing this thing and it just keeps giving me more and more it's got so much more headroom than my old ASW100!
 

Member 639844

Former Advertiser
Lol, sounds like your just testing its limits then :devil:. I cant help it with new kit either. Once you get used to having it around you'll probably calm down a bit. I dare say any port issues will likely be a thing of the past then, or at least incredibly rare.

Always a pleasure to see another happy owner :smashin:
 

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