Vertical spacing in stepped baffles

[NickA1976]

Before I ask my questions about building "stepped baffles", keep in mind I'm only interested in help on the design aspects of it. (I'm not interested in debating/opinions how affective they may or may not be, nor how they look ugly or nice lol).

In regard to driver vertical spacing, it seems it's best to have drivers (eg. A tweeter and mid) as close to eachother as possible. But most stepped baffles I see, its harder to keep the spacing like you can do on a fully flat baffle. I was thinking of using a truncated tweeter and a truncated mid to allow for tighter vertical spacing in a stepped baffle. (I'm not bothered by flushmounting truncated frames).

Would this help? Or do stepped baffle designs need further apart vertical spacing?

Also, is replacing the Dayton RS tweeters round face plate with the truncated face plate PE sells, simply a matter of removing the 4 screws and swapping? Or is there soldering involved, too?

[JRT]

...is replacing the Dayton RS tweeters round face plate with the truncated face plate PE sells, simply a matter of removing the 4 screws and swapping? Or is there soldering involved, too?

I have not taken one of those apart, but David Ralph has, and he has some very good pictures on his website, as well as good info on use of wool felt. I do not want to deep-link resources from his website here. Please follow the link directly below this line.

https://www.speakerdesign.net/

Moderator, that is a link to tech info, is not selling anything, so please do not delete the link.

[DeZZar]

As close as possible is the general consensus so the real question is whats the limit to the separation? In that regard you can rely on the general C-t-C spacing rule which is subject to your crossover point. That is the space between driver centres should not exceed one wavelength at the crossover point.

So if the C-t-C spacing ends up at say 150mm - your maximum (highest) point of crossover should not exceed 2.2Khz. Of course the rules are broken to some extent all the time with successful designs. I think its best to fly within these general rules but if you have to break them, fly as close to them as possible.

What you risk in separating the drivers too far apart, beyond the above rule, is coherence of the sound. In a successful two-way design for instance, at the listening distance you really shouldn't be able to tell if the sound is coming from the tweeter or midrange - they should present as one cohesive source of sound (point source).

[jhollander]

A stepped baffle/ recessed tweeter is intended to move the acoustic centers closer together to help time align the drivers. Potentially there are fewer crossover parts to reach the desired phase alignment. What you mentioned is true, that the offset will create a diffraction signature that may need to be delt with. Driver spacing is another component of driver phase alignment. Some prefer a closer driver spacing so phase alignment alignment occurs at a closer listening distance.

Lots of trade offs but I'd rank driver spacing as the least of my concerns, then diffraction as second, and then phase alignment as most important. Another way of saying this is I think I could create a crossover to time align the drivers without using an offset. Low order crossover slopes could benefit from an offset.

[a4eaudio]

As DeZZar states, "As close as possible is the general consensus...That is the space between driver centres should not exceed one wavelength at the crossover point".

However, this has been questioned some recently, as the developer of VituixCAD (and some others) have suggested a C-t-C of 1.2x teh wavelength at the crossover point sounds best in tests that they have done (which includes the listener being a reasonalbe distance from teh speakers, i.e., not desktop speakers.) I do think it would be universally accepted though that at some distance it is too far and the sound waves are not able to integrate accurately.

I think this supports JohnH's concern that driver spacing is low on the priority list, just don't go crazy.

[Billet]

Ideally, I like to position the center of the tweeter an even multiple of 1 wavelength of the crossover frequency from the center of the next driver.

C-C distance = 13500 / crossover freq x N. Let N=1,2,3...

[DeZZar]

I think this supports JohnH's concern that driver spacing is low on the priority list, just don't go crazy.

I agree in as much that usual design is working with a reasonably sized midrange/mid-woofer and tweeter and they are always grouped together so not a lot of attention is or needs to be given to the spacing and even aesthetically pleasing spacing isn't going to do horrendous damage to the soundstage. The last two-way I designed were specifically 'monitors' so I went to a lot of effort to even cut a recess in the tweeter faceplate to get the modest sized mid-woofer as close as possible. But the two-ways before that I didn't even check the spacing (its fine of course).

I think we need to be clear that this lower priority consideration is not to say that sticking them any old distance apart on the baffle is ok either.

[NickA1976]

Thanks, the driver spacing info helps. It seems my idea of wanting to use truncated framed drivers to get closer spacing won't hurt then. I understand how the step physically helps position the accoustic centers. The articles I've read qbout using stepped baffles never really mentioned vertical spacing so I was curious.

From the pictures on that link shared regarding RS tweeters, it looks like the faceplate simply lies off. Thanks

[andy19191]

It seems my idea of wanting to use truncated framed drivers to get closer spacing won't hurt then.

It hurts in that it increases the strength of the negative effect of diffusion off the edge but is this outweighed by the positive effect of closer driver centres?