Initially I was going to do a simple bass reflex box and mount the horn externally to fine tune more easily. Eventually, when all is set up, I wanted to do something with the horn internal like the old altec's (santiago, valencia, etc.). My living room is mid century so I think those would go great with the room. I was looking to do a single driver project until I found the Econowave thread. I was decided on an MLTL to go with a single full range driver but did not look into any MLTL designs for a 2 way, or with a horn. Even the MLTL boxes I saw for 4" Drivers were pretty tall. I would image a 12" driver would be pretty big? some very cool speakers in that linked thread, looked at that when planning the aforementioned single driver build. Didn't see any plans for any drivers over 8" in my research. Tinkered with the idea of making my prototype box out of foam core, would be easy to do a couple of different boxes this way.
So, the only question for the OP is, do you want some sort of stylin'
legs under your Altec clone boxes?
Seriously, if you still have an interest in an MLTL type thingy, say the word and we can kick-out at least these two types. And aiming the center of the pattern at a listening height + jockeying driver offset and cabinet size really does depend on whether or not the thing has legs. Er you have to do it at least twice...
The stuff below the line is less of a direct response to you and more of a tangential ramble in-context.
------------------------
Big, wide-baffle, squatty boxes like the original Altec stuff are great, acoustically.
- Easier to keep center-to-center (CTC) distance small for bigger forward lobe
- Lower baffle step transition freq
- Increased distance from driver to walls allows for thicker lining and avoids early reflections
The tall skinny (MLTL)
1/4-wave pipes are the bugger for 2-ways, particularly if one seeks to outboard the horn. The CTC is just too big if the driver offset position is set to null the
lowest harmonic of the pipe. Prioritizing CTC means the acoustics are rougher and will need resistive damping (and at a loss of efficiency). Big long ports just add a third stubborn resonance to interact with the other two.
These resonances matter in the big 2-ways because every single one is in the passband. Stuff ringing 200-400Hz mucks-up low-mids and you can hear it ringing (and once you hear it, you can't unhear it).
It's not just the
Helmholtz (and ignore internal modes or hammer them with fiberglass), it's both the fundamental
standing wave resonance from the height and the Helmholtz freq that need to be managed together. That's easy in squatty boxes up to maybe <2.5ft tall and it's packing a lunch for heights on-up from that.
Or you stick the horn inside the pipe for short CTC and live with the box mud that radiates out the horn walls. It also "pinches" the volume in the height direction--model that and see what it does and the tighter the cross-section is, the more it matters (esp when you consider adding extra support for heavy compression drivers). That, plus the reflections from walls right next to the drivers make the skinny pipes (seemingly terminally) still in vogue a "less clean" acoustical choice...but it you can't get it "sold" into the living room any other way, then that's what it is. (It's particularly audible in male voices. Things like that are why quick & dirty protos are invaluable).
Round horn fans disagree with prioritizing CTC, but those have issues, too. It's priorities.
Wayne's rationale that 90x50 is a good way to go for most people's ceiling heights and listening distances (so the vertical nulls are ceiling and floor) is pretty rock-solid to me, too.
The other thing is that some of those old Altec things just use the fore/aft position of horn (and trim pieces) to form the "port" (common opening). It's a different (old-school) alignment that pretty much no one does anymore (and current drivers don't often fit the approach, either). It'd be great if someone did one in 2024. The thing is, those implicitly get finished by manually applying fabric and resistive materials to dial-in the damping, so the basic alignment is to boom a a tiny bit and then pull it down with resistive materials. They target ports Ap~0.5<Sd<1.0 and that's the sweet radiation resistance improvement (
impedance match between port and room air) that only big ports can give. Amounts to "better grip" that that port has on the room air. It's the most efficient unassisted alignment there is, but the sims look ugly because the simple tools don't sim all of the problem. You just creep up on critical damping by applying layers of fabric over the port and the rear of the driver. The usual lining and usually a cross-batt of material on a brace to cover the whole cross section works to both reduce mids out the port and the max group delay as well. In the end, it's an efficient, well-damped, big-sounding cabinet approach--it's just not particularly predictable on a computer. Instead of a typically smaller cab with a smaller duct of some length, it's a big hole--an actual "port" with a length of one baffle thickness. The tradeoff, of course, to hit the same Helmholtz freq is that the box gets big...probably closer to 5ft3 than 3ft3.
