Port changes with amp inputs level change


2012-03-31 12:34 am
This will sound like another "noob" question. A few months ago I built my first 3-way with Peerless India 5.25'' mid and 8" woofer with a Dynavox tweeter. At the time I had spent very little time in this forum and used a "generic" formula for the cabinet (62 litres woofer lined cab, 3.6l sealed/stuffed for the mid) and an off-the-shelf crossover, with, corrected for the Peerless 12Ohm mid/woof, crossovers at 865 and 3350Hz. I think:)

After many hours of playing my CD collection I'm still happy with the sound (if anything, it has improved a lot) but tonight I noticed a very curious phenomenon. Both this speaker pair, and its predecessor, Wharfedale 510, retired now due to their 4Ohm status (blew the tweeters), have significant... what I assume to be "chuffing" from the port. Never minded it thought, thought it pleasant. Tonight, I turned my amplifier's "Input Levels" (Right and Left channels) up to about 80% (having turned them down ages ago to protect amp and Wharfedales) and played my most "chuffy" track being "The Birds" by Elbow. The chuffing disappeared!

Amp is an old (but powerful) NEC A1300-E 4-channel rated for 8-16Ohms (I discovered after 23 years of ownership, but then I didn't know what speaker impedance was until a little over a year ago), CD player is an unmodified PS1.

Having looked at different "simulations" or "recipes" since building these I've probably gotten heaps wrong- but I'm too old and with too many other hobbies/interests to tackle too much scientific info (my head spins sometimes after a session reading posts here:)). The woodworking part of the speaker build part alone was a huge challenge for a guy who can hardly drive a nail.

Can anyone tell me in simple, kindergarten terms what is happening with my speakers? I've felt somewhat inadequate about the build after reading seriously in here- but then, I'm happy with the sound and that's the object of the exercise I assume (plus the mental and physical challenge of the build, of course). Port size/length is most obvious candidate to me- but the mystery is how amplifier input levels would change stuff at the speaker.
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