My design goals are: 

1. Trapezoidal, easy to array 2 boxes per side

2. Manageable weight, <50kg hopefully 

3. Sensible size, front dimensions of ~550mm*800mm and about 600mm-700mm deep  

4. Comfortably meet any sub that plays up to ~90hz, eg. Punisher, BG horn 

5. Minimal cost with out compromising sound

6. Have a decent kick, I like techno, don't judge 

7. Drivers integrate well

8. Components are easy to source 

The compression driver is up to personal preference and would be hung in the mouth of the 15 inch horn, similar to the Xtro. I would use a light weight neo like the DE400 on a TD164.

The 15 inch section is tricky, I want it to play low enough to meet most subs, about 90hz but high enough to meet the MR8XTN at about 400hz, this is >2 octaves which is a lot for a 15 inch folded horn. The PM90/60 manages more with 2x12 inch drivers so I think it is doable. I have found such a design is VERY picky with drivers, after reading the specs of literally every 12, 14 and 15 inch neo from every major manufacturer I have narrowed it down to the RCF MB15N351. 

The total driver/hornflare cost is 554 pounds on Blue Aran, I would consider this a significant saving relative to the previously mentioned designs. 

Anyway here is where I am up to with the design for the kick section, the fold would be 1/4 wavelength of the highest frequency I plan to produce. 1/4 wavelength at 400hz is about 200mm. 

My kick - Black 8ohm @ 2.83v , Xtro - Grey 4 ohm @ 2v

My horn

Xtro - Inputted as one horn then simmed as two parallel speakers 

Displacement with 650 watt, 72.11v @ 8ohm 

This sounds interesting, I have thought about designing and building a scaled down homage to the tms2, based around the same mid-horn you are suggesting but using a 12" to better suit the width of the mid horn and limiting the downward extension to ~130Hz to keep the dimensions down overall, like the tm2 however, my thinking is to keep the footprint rectangular.

But this is not what you are doing and this is your thread and topic, I just wanted to relate a bit that's all.

A couple of reflections on your proposal:

If intended for the greater DIY community, and by that I'm thinking worldwide, perhaps the mid horn is a limitation as far as availability is concerned, but there are few options, the limmer 8" mid horn springs to mind, not sure if this improves availabillity though, or to resolve it completely design it to be built by the diy'er, but it is difficult to design.

Keep the design and build as simple as possible, a tricky balancing act concerning performance compromises, keeping the build simple makes a very big difference with regards to the reception an number of builds, which in turn correlates to the amount of feedback on the design.

Making the 15" flh section reach 500hz is perhaps doable if limiting the lower extension as per your proposal, but will it sound good, honest question, perhaps it will sound just fine, but my experience is a bit limited as to that application.

Just a few thoughts of mine on the topic, best of luck, keep us poted andstay healthy, br / Martinsson

I was originally planning on designing and making my own mid-horn using the 10NSM76, I went as far as to learn how to use ABEC/AKABAK for BEM modelling. I drafted up a design and modelled it, the directivity wasnt even close to acceptable and I had no idea how to improve on it so I just gave up. I was a little disappointed as I working with fibreglass is no problem for me, I use it a lot at uni.

The MR8XTN is by far the most accessible mid horn in my opinion, it is very affordable for what you get and Blue Aran ship worldwide. I have ordered stuff from them to Australia, they were happy for me to organise postage but they can organise it for you if you don't want to worry about that. 

Being plastic also means it is very light weight, if you have ever picked up an XT8 you will know how heavy they are. 

martinsson wrote: Making the 15" flh section reach 500hz is perhaps doable if limiting the lower extension as per your proposal, but will it sound good, honest question,

fat_brstd wrote: My worry with your box is the 15" section, whilst it sims up to 400hz will it sound any good that high or will be the classic boxy sound you get. I have never really liked the way band pass boxes play up that high and if you are going for a front loaded horn with at 180 degree bend in it rather than a band pass assisted style that will also affect how high the box can play.

This is NOT a bandpass horn, you can tell by the very small front and rear chambers in the hornresp window posted above. I think that boxy sound is what you get when you try make a bandpass horn play over a large bandwidth. If i'm not mistaken, the point of a bandpass enclosure is to narrow bandwidth and increase efficiency with in that narrowed bandwidth so trying to get one to play over a wide bandwidth seems like a stretch. 

There are already designs that have no problem playing higher than 400hz with folded FLHs, including the MKH230. The PM60/90 plays up to ~750hz, that's almost a full octave higher, this cab has glowing reviews. I am aware this is a ported horn but 750hz isn't coming out of the ports, its passing through the horn, around the fold. 

The secret appears to be correct driver selection and putting the fold as close to the throat as possible, 1/4 wavelength at the highest frequency produced at a minimum. This isn't limited to bass horns, there are Danley products that use this principle with compression drivers up to 16khz. 

fat_brstd wrote: Have you thought about using a ported straight short horn instead of bandpass? If the intention is for this box to always be used with a sub then the extra extension gained from a band pass arrangement is unnecessary, and using a short horn that loads down to say 100hz with a port tuned to 75/80hz to get a boost at low end of the boxes frequency response and deliver the required kick sound for techno. Using a high efficiency, small voice coil driver with a sensible power handling (4-600 watts rather than a 1200 watt monster bass driver) will mean you get a lot of kick for not a lot of money.

I don't really have any experience with ported horns, I don't think I have ever heard one, I do have a lot of experience with FLHs and I love the way they sound. 

As far as driver selection goes, I pay no attention to things like power rating or VC size. I only look at T/S parameters. I have a spreadsheet based on the Leache paper that finds optimal T/S parameters based on the type of system you are trying to build. I am aware the voice coil diameter affects BL and Mmd which affect Qes, Fs, Vas etc. but I wont make a decision based on voice coil diameter. If a suitable driver happens to have a large power rating and a large VC then great, it will take more power and exhibit less power compression. 

fat_brstd wrote: Looking at other similar boxes the classic selenium mid top (as used by many reggae sounds in JA) is a 15" on a short horn, 12" on a short horn and then a 2" and bullets, normally located in the middle with the 15" at the bottom and 12" at the top. The issue with a box like this is the size, they are massive compared to something as compact as an xtro.

I have only just started experimenting with layouts and have one that is 20L smaller than an Xtro, I expect to make some improvement on that as it has a lot of wasted space. 



The major issue i'm having is packaging. I think a trap cab is ruled out, a 15 inch driver is quite wide and getting it close to the fold is physically impossible if the cab tapers in at the back. 

Another issue is that the rear chamber of a FLH is quite small, my current iteration is 18.5L which is tiny compared to a BPH, this may sound like a space saving but it makes it impossible to package it in such a way that includes the back of the mid horn in the same chamber. 

The last issue is that the MR8XTN is actually quite small and a 15 inch driver doesnt fit through the baffle cutout... i'm still figuring out how to give access to the driver. 

isn't that rcf 90x90 dispersion? Might not be ideal for 2 aside.

i know this is preliminary design stage and all that but 3000cm2 mouth is like 60x50cm, which a huge aperture to fit into any kind of box. considering the path length is 80cm too you might struggle to fit that into a single fold.

As others have said it may not play well up so high but all that depends on how you intend on folding the horn and how sharp the bends are.

Im interested in seeing what you come up with in any case. Good luck with the project!

What about the bottom end like the RCF 4pro 6001?

Twin 12, may help keep dimensions compact, whilst going high enough to reach mid horn, enough spl and potential for it going low enough to meet bass box.

Single 15 has merits, perhaps as a bass reflex, but a lot of draw backs, when horn loaded, mostly size and horn length related?

Given price of watts to get spl, and bandwidth, is cheap, BR 15 could work?

I'm thinking that the wavelength of even 100Hz is 3.4m, so unless your stack will be arranged in such a was as to keep this box within 0.85m of the ground, it won't really be in half space. That would result in an awfully low position for your upper mid and HF, so I'm assuming your stack would end up higher?

FWIW,

David.

Making the cab narrower and shallower while maintaining height means the mouths can be closer together when splayed, it will take up less floor space in transit and the mids and highs can be as high in the air as possible. 

By my calculations it should weigh 40-45kg all up, inc drivers, horn flares, paint, screws etc. I would consider this a very manageable weight for a 3-way hornloaded mid top. 

F3 is about 84hz, so it should meet most subs no problem. 

I have designed this to fit the B&C de360 on an XR1064 as it is a very light weight, low profile driver. The 35 watt power rating might scare some people but with 110dB @ 2.83v sensitivity it should have no problem keeping up. Being a ring radiator it should have good HF response and suffer very little breakup. The DE250, a driver I am very familiar with and know has no problem keeping up with an Xtro. The de250 is only 0.8dB louder at rated power. 

The 15inch driver is the MB15N351

PM me if the link goes dead

It reminds me a bit of Funktion One res 5. 

Altough your cabinets dont look  trap.

Maybe a good idea to implement some wheelboards for transporting and stacking.