Do the "rules for subwoofer placement and stacking" apply to T45

[Pabloaguas]

Hi Bill,

I have been using my pair of T45s several times a month for Djed dance events. I have been wall loading them perpendicular to the wall with the mouths facing the wall, about a foot away, side by side.

So I just took a look at the post https://billfitzmaurice.info/forum/viewtopic.php?t=398
This post got me wondering if there is a better day to do this. Obviously much of what is on that guide is for the t39, t48, t30 etc. and I understand the rules are a bit different for the t45 (and t60). Wondering if I am at the optimal distance from the wall?

Also wondering, that if I experiment with corner loading, what the optimal distance would be? Can i try corner loading with the these square to the walls with the mouths facing one wall, and the sides facing the other? Or am i limited to the 45-degree angle setup? And what distances to try with these.

My Tuba 45s are 18" wide.

Thanks for answering. I get continuous compliments that I have the best bass out of all the of all the similar events in town.

[Pabloaguas]

Also wondering if i should try the angled wall loading as seen in the second photo of that guide?

[Bill Fitzmaurice]

A sub is a sub, the same rules apply to all.

[Pabloaguas]

A sub is a sub, the same rules apply to all.

So the majority of the photos in the guide show V-coupling. So, you are saying that I can V-couple the t45's?

[Bill Fitzmaurice]

You may, but the added horn length isn't sufficient to make it worthwhile. That's why the T45 plans don't show V coupling as an option.

[Seth]

Hey Pablo, it's been a while. Welcome back

The placement in any given room is always different and obtaining the best results is always a matter of testing... trial and error.. Use "the rules" as a starting point and foundation to your placement choices. Corners are almost always the best spot for coverage in the room as well as maximum output. It shouldn't matter if you're against one wall firing into the corner or 45º firing into the corner, but it could matter depending on the unique properties of the room. Try one configuration or location, walk the room, try another configuration or location, walk the room, choose the configuration that has the smoothest response throughout the room with the fewest dead spots unless there are other factors.

[Bill Fitzmaurice]

In room response is significantly altered any time a speaker is moved by a quarter wavelength or more. At 10kHz a quarter wavelength is less than a half inch, so where tweeters are concerned minor placement changes can make a big difference.
At 100Hz a quarter wavelength is 2.8 feet, so unless it involves the distance to a wall or corner moving a sub by less than 2.8 feet isn't going to have an effect.

[Pabloaguas]

Very good.

My last curiosity is regarding this concept of the wall or corner somehow 'extending' the mouth of the horn. Seems somewhere i read that wall or corner loading kind of makes the mouth bigger- maybe similar to the v-plating? This is why I was asking about distance to the wall. It seems that if we are parabolically expanding the bell or mouth of the horn, that there would be some magic distance in which the sound pressure has something to push against as it exits the tuba's mouth. Like maybe the distance would be optimal to make the area of the three sides that the sound escape from perpendicular to the mouth somewhat equal or slightly greater than the area of the mouth itself. I'm not sure if I explained that correctly, and if I did explain it in an understandable way, is my thinking valid or am I just overthinking it?

[Bill Fitzmaurice]

It doesn't make the mouth larger, it changes the radiation pattern. Going from free space to half space gets 6dB, going from half space to quarter space gets another 6dB, going from quarter space to eighth space another 6dB. You get spatial loading where the distance to a boundary is more than 1/4 wavelength.