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In the Forum: Audio Discussions
In the Thread: Macondo’s MiniMe or about Pilot Acoustic Systems
Post Subject: MiniMe or Fat BastardPosted by Lbjefferies7 on: 9/20/2008
Okay, here's a graph that shows theoretically what will happen when the volume is doubled and a few other circumstances. It should give you an idea of what's going on.
It is important to note that when the Vb is doubled, the port lenght will be roughly half if you want to maintain the origional Fb. If the port is left the same length, the Fb will be much less...and as you can see from the yellow line, this may be a useful situation. How two enclosures with different volumes and different port tunings will interact is anybody's guess; but with a lot of careful tuning, you might just get a deeply extended bass. It will at some point become just a fight with physics, which never seems to end well whenever tried. I would not expect much under 40-50 hz, which is pretty impressive.
"What you feel would be a difference between those 3 cases?"
Hmm, this is a difficult thing to say. I would expect there to be literally no difference between the first and second speakers. In the third speaker, the port tuning would be definitely screwed up. It could be tuned, just not by mathematics. It is possible that the port could 'ring' with the vibrations picked up from the enclosure. I've never experimented with such a method. Also, I am not absolutely sure where the Fb changes from being in the "Sound-Range" and the "Air-Pumping-Range." In my low frequency channels, the ports are tuned to about 22 hz. With the ports open, the speaker becomes an air pump and I would preferably low-pass them at 60-80 Hz...just a guess. Until I have my mid-upper-bass channels built (coming soon hopefully), I have them sealed and run them up to about 125 Hz...definitely in the Sound-Range. If I understand correctly, your smaller enclosure part of MiniMe may be tuned in the Sound-Range at which point, the port will become more critical, and less desirable.
Either way, I would not anticipate very many higher-frequency sounds comming from the port.
Hope this helps, and feel free to ask more questions; I haven't had the luxury of thinking this much about tangible things in a while
Regs
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