828/525 horn mounting height

[Phil-G]

Some HF sleds have the horn 6-8" above the cabinets. At home, i just for all intent set them right on top of cab. With the bottom of the horn flanges nearly hanging in front of the bass horns. being as i have a limited distance in my living room i figurered the closer the better. baring mounting them directly in the basshorn like my 9864s are.
so anyway, in the case of the 828/525s is there such a thing as too close?

[GM]

In theory; a horn, vent, etc., has an end correction, i.e. its air mass plug hangs out a bit, which in freespace is ~0.613*radius to find the terminus [mouth] acoustic radius and space up the horn however amount this new radius 'touches' the nearest reflective boundary. This assumes a round horn of course, but until the terminus becomes a high aspect ratio this 'rule-of-thumb' is close enough and ensures an adequate space for horizontally opposed layouts, but if used vertically to increase horizontal dispersion, then you have to convert the radius to the terminus shape to find the spacing, though folks normally just use the regular spacing.

When XO'd to another horn though, ideally both horn's acoustic radius needs to be accounted for, so you want the spacing such that their output overlaps at the XO point and since the bigger horn has a larger radius it's going to jack up the HF horn a bit more than just its radius.

Normally, this is all done from measurements, but doing a scale drawing of frequency circles or rectangles is plenty good enough. All that's left then is to empirically find the best HF tilt angle if a HIFI/HT app, otherwise measurements made at various seating positions to find an acceptable compromise.

If there's 'wings', then the end correction is 0.732.

GM

[Phil-G]

This is the first time I've understood what you wrote.

[GM]

Bummer! Never been very good at explaining complex stuff.

GM

[Phil-G]

Not drinking has helped.
I was thinking that if you drew a picture it would help, then I read down to where you mentioned a scale drawing. Then it made sense after I visualized it.

[GM]

Yeah, been there, done that! I found out early on that when I realized that sound waves move like soap bubbles in a kid's plastic ring, all of a sudden I understood the basics of most everything about sound propagation in air that folks had been trying unsuccessfully to explain to me from their physics textbooks, which led to viewing room acoustics like watching water sloshing around in box since the [sub] bass air bubbles are so large they simply wash over objects.

A grossly simple way to view all this, but it works pretty well for me, so I make scale drawings to figure out most things and over time ever more accurate simming, measuring software has proven it works plenty well enough.

GM

[gdmoore28]

This is the first time I've understood what you wrote.

Ha! Me, too, Phil!!!!!!!!!!!!

But I must say that the soap bubble analogy worked best for me.

GeeDeeEmm