Mid-tops, what to do....

Hello... I'm trying to work out what direction to do regarding mid-tops for my system and I keep going round and round in circles so I'm going to describe a few options I have to try and bounce ideas off the rest of you! (Basically, I'm after some free R&D help!!!)

I mainly do live music in venues up to 5-600 capacity. Anything from nightclubs to theatres. I currently use a system of 2or3 reflex 18's per side with a single twin 12"+1.4" on top. I love the sound of it, works really well for live music but I'm reaching the limits of what I can do with one box per side in terms of SPL and horizontal coverage (one box is 60deg wide).

So, options:

Build another pair of the twin 12" boxes.
Simplest solution in some ways but the biggest issue is powering them because being a 4Ohm cab, I'd need another amplifier for the midrange. Don't really want to run down to 2Ohms.

Move to a 3 way cab:
I really like the idea of a dedicated midrange, probably either an 8" or 10". Because I'm doing live music, I want to stick with a larger format compression driver and slightly lower crossover than designs like the Xtro. Given I run out of headroom on the compression driver on my twin 12" boxes, crossing over at 1.4kHz, even a really meaty 1" driver might not give me enough output. Ideas are maybe a FK1 style folded 12" up to an 8/10" or a single 15" with the same mid-high. One driver in each range makes powering multiple boxes easier. I'm considering using my current 12" drivers (which are superb at midrange), and sticking a 15" under them to do the low mids.

Vertically arrayable cabs:
What would be really nice is to design a box with say 90deg dispersion horizontally but a narrow vertical dispersion (don't need much for flat standing venues) which I could use one for small gigs and just stack more vertically if I need more SPL or to cover a wider vertical area. Inspiration for this would be D&B Q series and L'Acoustics dVDosc. Would solve the problem that with a lot of point source solutions, if you need more SPL, you have to increase the horizontal dispersion too.

One big FO box:
Not a scaleable solution but I could just build one stupidly loud box with the dispersion and SPL I need. Something like a twin 15", 10", 1.4". Like an Xtro. No good for gigs I do on my own tho....

I'd be interested to hear your thoughts/ideas. I'm not sure it would work to try and do an FSP design by committee but I would be happy to collaborate with other interested parties and possibly share the design with the community in the future.

Chris

Yes, you are completely right, another cab would be easiest.

And FSP-design by community does end up to be design by interested parties who happen to be FSP members.

You know, that 15+12+1 idea reminds me of that selenium hornloaded box...

But anyway.
I am assuming that your drivers are both 8 ohms.

You know, chris, there are actually non-LA cabs that are vertically stacked. I believe community made one such box. I think.

Personally (well, completely personally, if i had your subs...), I would go for 2 90x90 cabinets, loaded with a coaxial (or 1.4") compression driver loaded on diy round WGs with correct mouth termination (which in my case, the expansion of choice would be the OS). There would be a 15" woofer on these cabinets (or clamshell double 12"), and the crossover frequency would be 500-900hz, dependant on the driver. The woofers would be ported to around 60-70hz to enable use alone. As a finishing but crucial touch, I would fashion a foam plug for the horn, bung it in, EQ the highs up a bit, and marvel at how my speaker disappears and sounds like a lovely paper cone driver going up to 20K.

On option two, I would go for a ported horn / bph approach unlike the F1 cabs (which require bolt-through phase plugs for those folded horns, which presumably you don't want to manufacture). Then the same mid highs. This would be like the H3/TMS. But you already knew that.

As nice as it would be, I don't have the time to design and build custom waveguides. I've been considering using Mykeys XT8 horn designed for the Xtro as it's a nice compact design.

Twin 12" low mids would be nice but again I'm down to the amplification problem.

Building 4 15" + 12" + 1.4" boxes would be easy and not too expensive as I have drivers to do at least two prototypes already.

I meant 2 15" ones. But it was my 'no barriers' choice anyway, what with making waveguides (though the design part is the much easier bit (excel spreadsheet lol), unless you have a cnc it's pretty unfeasible). [img]smileys/smiley36.gif[/img]

I think the 18sound XT120/1496 might interest you (90 degree horizontal dispersion)
But even more suitable for the dispersion you were describing might be these:
www.ddshorns.com/catalog.php?page=products

So then the 15+12+1.4 cab comes in. If you're going all hornloaded, I stick with my idea for the 15" woofer, you would end up with an oversized TMS/H3/FK1 type thing. If we go along with this, then off to hornresp (or Mykey if he has anything).

Ah, I'm mainly talking about direct radiating boxes rather than fully horn-loaded. I need one man lifts! If you haven't seen any pics of them, my current mid-tops are:



Which for two direct radiating 12's are silly loud. Each 12" is about 101dB/1W/1m. Not surprising one compression driver can't keep up!

I've been tempted just to build single 12" versions.

I'd go for the line array approach as you mentioned. There are now plenty of suitable components available, so you can do it all "off the shelf".

If it was me I'd try and do a paraline element based on a single 1.4" coaxialper cabinet(ie the BMS one). This should do from about 500-800ish up to 20K+. Then you just need a pair of 10" or 12" lo-mid drivers to fill down to your subs. If you cross the BMS at 500, you could duct the lo-mid drivers for an extra couple of dB. And if their EBP is high enough, consider porting them.

You'll have to choose the vertical spread for each box then shape the cabinet accordingly and design the paraline for the same curvature in the vertical. I beleive the internal dimensions of the paraline will set vertical curvature from none to as much as you want.

Being so easy to make, I'd leave the paraline element as a removable part (which in turn could give access to the compression driver). Then you could experiement with alternatives and provide swappable options for different vertical coverages.
Edited by: jsg

I've toyed with that idea in my head in fact, a removable aluminium plate mounted with whatever HF option you want (probably what my next cab is going to be...), for when I think a single LA cab won't do (the effects you mentioned and I basically agree with i think only apply to more than one cabinets, an array).

Chris, I am facing exactly the same dilemma at the moment, I am very tempted to build an array that uses twin 8" or 10" drivers with two per box mounted horizontally. These could be used with as little as 2 boxes per side and up to 4 per side i.e. 8 drivers.
This should give me 135 - 136 db continuous and then have a co-axial comp driver mounted in its own enclosure that would do 800 hz up.
The one thing putting me off making a dedicated LA is the cost of suitable high quality waveguides and drivers.
At the moment I am building another set of my twin 12" + comp as the photo I recently put on the forum (for a local DJ).
It will be interesting to see how they perform when used 2 per side + 4 of the 15" subs per side. The 12" drivers should couple perfectly as the comp x-over is at 1000hz.

Tony

Hi chriss,
the horn in the midtop is an 18sound? What cd do you use for drive it?

Yes, the horn is an XT1464. Fantastic sounding horn flare, even but very tight coverage pattern 60x40deg. I'd love to use it in all my mid tops but it's quite large!

I've got a pair of PD C14 compression drivers doing the HF. Sound very good and were a bargain when I got them.