Clarification of boundary loading

[Charles Warwick]

So, I was getting into a discussion and I was curious to make sure my understanding of boundary loading is more or less correct.

So here was my explanation:
Boundary loading isn't something special to horns, it's a principle of physics in which you restrict the radiating planes (i.e. going from half space to quarter space) less is lost to cancellation hence the apparently increase in output. This is why if you EQ a monitor flat in an anechoic or half-space measurement, when you bring it into a room with a corner it'll sound much bassier than it was due to boundary loading.

To extend that explanation, this principle applies to any radiating surface be it horn, direct radiator, or otherwise. You will see the same amount of benefit (in db) from sticking any sub in a corner as any other.

Is this more or less correct?

Thanks

[Bill Fitzmaurice]

Is this more or less correct?

Pretty much. Makes you wonder why everyone doesn't do it.

[doncolga]

Sounded good to me.

[Charles Warwick]

Well, I'll be curious to know what comes of my discussion since they were saying things like this:

our speakers do NOT benefit from wall or boundary loading the way one might use a folded horn.

And when I questioned that they said that:

We are referring to the strategies employed by folded horn users, especially a certain DIY version that provides significant gains in output. In a true imperial sense there is boundary interaction but that was not the question Jeremiah was asking.

Obviously referring to BFM designs, but whatever, physics doesn't bend to marketing.

[Ryan A]

Well, I'll be curious to know what comes of my discussion since they were saying things like this:

our speakers do NOT benefit from wall or boundary loading the way one might use a folded horn.

Even if it were true, is that supposed to be a good thing about their design?

It has been said that horns benefit more from boundary loading than other designs, but this is all the more reason to choose horns imo.

[Charles Warwick]

It has been said that horns benefit more from boundary loading than other designs, but this is all the more reason to choose horns imo.

At least from what I understand, horns really don't benefit more from boundary loading, it's just that BFM users tend to have a better practical understanding of applying it which is why people associate horns with corner loading.

[Bill Fitzmaurice]

Well, I'll be curious to know what comes of my discussion since they were saying things like this:
our speakers do NOT benefit from wall or boundary loading the way one might use a folded horn.

Hogwash. The only thing I can say for sure is that whoever said that hasn't the slightest clue with respect to the science of acoustics or loudspeaker design.
There is one instance where boundary loading has no effect, and that's where the speaker baffle is large enough so that the baffle step as been overcome and the radiation pattern is 180 degrees or less. That requires a baffle/radiating plane dimension of 1 wavelength or more. At 1kHz that's easy enough, one wavelength being only 14 inches. At 100Hz it's a wee bit more difficult, one wavelength being over 11 feet, and those wavelengths keep getting longer as you go lower.

At least from what I understand, horns really don't benefit more from boundary loading, it's just that BFM users tend to have a better practical understanding of applying it which is why people associate horns with corner loading.

True, more or less. The exception is a true corner horn that actually leaves off the final panel of the cabinet, instead using the wall to complete the horn flare and mouth. We don't employ that feature in any of our cabs.

This link gives a pretty good explanation of what happens with wall loading versus free standing:
http://www.fulcrum-acoustic.com/wordpre ... -Space.pdf

The difference between wall loading and corner loading is that a corner reduces the space that the speaker is firing into by half compared to wall loading, giving another 6dB of axial sensitivity. But what also must be accounted for in the final result is all of the other walls, and the ceiling, which all complicate the result.

[Grant Bunter]

IIRC user "Boyd" here from NZ has been employing boundary loading (wall and corner) with the brand name direct radiators the company he worked for (or hired from) since he got here. No doubt since he has completed his builds, he will continue to do the same.

Charles, in this other forum, perhaps you could suggest that the person who says it isn't required try it, and measure the results, which should speak for themselves...