The 'Big Fun' horn (build pictures)

The original drawings (design from the article):

This was obviously before CAD software became affordable and readily available.

The first ever BigFun horn

Built by me in 1995. Admittedly a little crude handywork (but a learning experience)

What a professional build looks like

These next 4 photos are nicked from Stewart Speaker Systems, a professional speaker builder located in Canada. They build bespoke loudspeaker systems, and have made a lot of full range driver cabinets, including horns and designs for Lowther drivers.

The cabinets are built 24 years later, in 2019. Magnificent craftsmanship, and for me personally, a truly gratifying experience that this design (and idea) still is appreciated. The original publication of these pictures are from Stewart's Facebook

This is more or less exactly what I thought they should look like!

A modern Lowther driver (an EX4?) is put where it deserves to go.

Notice the additional bracing toward the mouth. Internal preassure is low at the mouth, so I did not deem this necessary in the original build. But, it looks just right, it will not have any adverse effects, and will defintely add some rigidity to the cab. All in all, probably a good idea.

Both cabinets finished. I have to say, these loudspeakers are just magnificent. Good job, Stewart!

A really striking DIY(?) build

The only pair I have seen that is painted instead of veneered and laquered. All edges are rounded, which is a generally a good idea, and also lends a bit of subtlety and elegance to the cabs. Possibly built by Larry D. Moore (otherwise known for high-end hand-built SET amplifiers), but I have noot been able to confirm this. I think they are pretty striking, and the design seems to say "Look at me, I am big! Play me, I will impress you!"

The photo appeared in an online ad way back when, and I found the description interesting: Selling a pair of Big Fun Back Loaded Horn Speakers [...] Originally they were intended for Lowther PM-6s; but, after try everything from Lowthers to Fostex to Feastrex, the Dayton Audio PS220-8 sounded best.

I only ever tested Lowthers for this horn, ranging all the way gram PM6 up to EX4. As a fruitless excersize I also tested some really cheap full ranges, and in fact a pair of Coral Flat 6 drivers. I never got around to trying out Fostex, Seas, or any other high-end alternatives. The conclusion that Dayton Audio PS220-8 Drivers worked better than Lowthers for these horns is interesting, for the following reasons:

• They are still readily available, which should indicate that they are indeed very good drivers
• They are considerably cheaper than Lowthers (and most Fostex drivers, I guess), and dirt cheap compared to Feastrex drivers.
• The TS parameters for this driver should, by traditional conventions, be less ideal for back-loaded horns, compared to amost all of the other drivers mentioned.

There is of course the matter of personal taste. My experience was that the EX4 was exceptionally well suited for these speakers, but the above just goes to show that one should have an open mind, and embrace some experimentation. In short, I wish I had a way to listen to this configuration!

Curiously, a very thorough paper on front loaded horns back in 2008 ("Section 6.0 : Design of a Front Loaded Exponential Horn By Martin J. King, 7/01/08"), found that some of the accepted conventions on TS parameters for applicable drivers were largely without merit. I find this extremely intriguing, and it would be surprising if this didn't hold up (at least to an extent) for backloaded bass horns.

Could some established truths actually be myths? Or, maybe the case is that the current (modern) driver technology affects the relationships between given TS parameters. Maybe the relative values of Qts, Xmax, VAS, T, and other parameters does not affect a particular outcome the same way as it did in the 40s and 50s. Maybe other parameters are more important now than they were "way back then"? It would at the very least be worth looking in to. Quote from the mentioned paper: In fact, other then the loss of horn system efficiency, the higher Qtd drivers extended lower in frequency and produced a smoother SPL response.