About the M80's: According to an audioholics review:
"Let's talk ports for a moment. The M80ti(s) have three each, one on front and two on the back. The midrange drivers are completely isolated from the rest of the speakers via the internal chamber construction. The triple vortex ports are tuned solely for the dual 6.5" low frequency woofers, which contributes to them attaining such good frequency response."
And about the M60's:
The 5.25” woofer is actually encased in a sealed cylindrical enclosure. This ensures the proper box volume for the midrange to operate and isolation from the rest of the enclosure for optimal performance.
