Min. port clearance to side walls?

[ro9397]

High quality (over $200ea USD) 160mm mid bass, f3 45 Hz range ported in estimate .4cf box. Normally I employ subs and the monitors are high-passed around 125 Hz; the port allows the option to run the monitors full range.

Plastic port 1.5" I.D. x 3" length.
Clearance from edge of internal port opening to internal rear enclosure panel 7-3/4".

I desire to site the port on the front baffle just above and to either side of the tweeter (tweeter atop mid bass, drivers horizontally centered on baffle). Clearance from port circumference O.D. to...
Internal horizontal (top) panel: 1/8"
Adjoining internal vertical (side) panel: 1/8"

Q: Potential (or definite) negative audible effects from the 1/8" clearance as described above? If 1/8" is too tight, what is estimated (or definite) minimum clearance?

Notes for the curious: Each channel has two monitors separated by a stand. The primary/upper box drivers fire forward, w/ port on the rear panel. No drivers fire directly forward on the ambiance/lower box. I desire the port on a panel different from the upper box to stagger the port locations to minimize the room's bass mode effects.

[ro9397]

Potential or definite negative effects from the port-tweeter proximity may be mitigated by the 60-degree firing angle toward the side walls.

[Brett]

I'd put the port somewhere else myself as Dan's measurements of the B2030 speakers showed clear diffraction effects with them located beside the tweets.

My general rule of thumb is a min 1 port diameter away from any other surface. More is good.

[ro9397]

Thanks Brett.

This monitor is a clone of the best stand mount I've heard, a $6k/pr USD French ASA Pro Monitor. One of the few changes between the ASA and my clone is the ASA has the port on the front next to the tweeter and mine has the port on the rear. It could well be that relocating the port contributed to slightly improved treble performance on the clone, for the reasons you mention above (though the cap and series resistor on the clone tweeter are also different, as is the enclosure panel material).

Am I the only one to question why ports are never located on a side or top panel? Or staggered locations (L ch on panel A, R ch on panel not A), toward staggering the room modes? I suppose aesthetic impact may prevent such port locations. The entire issue of staggering room modes needs tremendously more discussion. The "conservative" tendency among hobbyists/scientists of all sort (not just audio) I find to unnecessarily slow the march of progress.