Fortura "Turtorial"
Whoa! Dude! After 30 years of meeting
zero people who'd ever heard of, much less owned these speakers, I join AudioKarma and find a whole nest of Fortura-ites. What are the odds?
I've had mine apart, repaired them, stuffed them, sealed them, coated them, biamped them, sold them and had them given back to me, and finally, they were my son's speakers for several years. For those of you who are used to modern speakers (which, trust me, are generally much, much better than the average affordable Seventies speaker) and thus find the Forturas lacking, or who've just picked up a battered pair and wonder whether they're garbage, a few home truths:
1) ESS made these speakers but didn't put their name on them. I suspect they were yet another "private label" job for stereo shop chains, made to sell at an attractively low price. This cheapness is reflected in the construction.
The complete Pedestal (ie, floorstanding) Fortura line was models 8, 10, and 12, and as you've guessed the model number is the woofer size. There was a corresponding Bookshelf series but examples are very rare. They all crossed over to the Heil at 1500 Hz, which was pushing it, but that was ESS all over. The 12's crossover network actually had compensation built into it for the honkiness resulting from such a large woofer being forced to reproduce what amounts to treble frequencies.
2) The Fortura tweeter may be the best ESS ever made, at least potentially. That's an outrageous statement, but consider this: This is the only inexpensive Heil that's the equal of the big Heil on the most expensive ESS lines-- first, it's a dipole, just like its big bruder, and it crosses over only an octave higher: 1500 Hz versus 800 Hz. Due to its small size it has much better vertical dispersion than the big Heil and fewer problems caused by diffraction. It also has to work much harder, which explains the lousy circuit breakers ESS figured would be needed-- but they aren't, and I'll explain that momentarily.
4) The cabinet was obviously designed for looks rather than low diffraction, which wasn't seen as a big virtue back then. It would be best to saw off the decorative side panels until they're flush with the faces of the cabinet on the top and front, but ouch, even I've never been able to bring myself to do that.
A bigger problem is that the Fortura cabinets, sturdy as they are, were designed before Thiele-Small. They're not tuned properly for their woofers. The biggest and quickest improvement any Fortura owner can make is to plug the port. This assumes you're using the original woofers, which by now won't have their original surrounds. We'll get back to that in a moment too.
5) The best sounding Fortura, at least theoretically, is the Fortura 8, because it doesn't make a big cheap woofer try to operate well out of its "safe" area-- it only tries to make a
small cheap woofer operate outside its safe area, and since a smaller cone is a stiffer cone, that's an improvement. Today, no speaker designer would dare try to market a two-way that crossed a 12" woofer over at 1500 Hz. By that point, even the Fortura 8's woofer is starting to beam and enter cone breakup. These weren't horrible woofers, and they had Alnico magnets (at least the 12 inchers did), but they were simple, cheap straight-sided fiber cone CTS woofers, and they weren't up to the tricks ESS was trying to make them perform. A 6" woofer would have been just right, but nobody would've bought a Fortura 6.
By the way, this criticism holds true of the AMT series of speakers as well, but at least those had Bextrene and polypropylene cones.
6) By now, there are zero Fortura woofers with intact surrounds-- any intact ones you see either have replacement surrounds or are replacement woofers. Seventies Foam Rot is also why you don't see any Fortura grilles-- by 1990 all had disintegrated into crumbly sticky awfulness. Too bad-- the original waterfall-style grille with its vertical ribs was quite handsome, even unique.
Considering all that, the best course of action would be to measure the cabinet and port and find a good modern woofer that fits that tuning. If you re-surround a Fortura woofer, you'll have to remove it, which leads us to
7) The woofers are glued in. Badly. A bottle opener helps to pry them loose. T-nuts and bolts are a good idea to replace the puny wood screws. Use silicone to seal the woofer airtight.
8) Back to the tweeter and that @#&$! circuit breaker: If you have a powerful amp and can hear when an amp has run out of oomph, you won't blow the Heils. Go inside and bypass the breakers, which stick, go intermittent, blow partially (
that always sounds good!) and cause far more trouble than they're worth.
So why did ESS install the little #$%@ers? Back in the day when there were no powered subs and receivers had only 20 or 30 watts per channel and were regularly driven into clipping (which couldn't be heard by our primitive ears), you could easily blow a tweeter when you overdrove an amp that wasn't powerful enough. These days ears are more educated, better speakers make clipping more clearly audible and average amps have a bit more power anyway.
Sounds like a replacement L-pad for the tweeter would be a good idea for some folks. Mine are noisy but serviceable, but others might not be so fortunate.
9) The back of the tweeter was originally damped with the same cotton used for the cabinet, but by the time the speaker reaches you, it may be gone, but this is easy to fix. Cotton balls (preferably compressed by ironing them or some other way-- dryer lint may work even better) stuffed in the Heil's rear slots can really help. The 1st-gen Heil is subject to twisting and other nonideal motions when it's driven hard (which explains the damping/restraining net you see from the AMT-1A onward), and you get rattling and buzzing at certain frequencies. The mini-Heil has to work very hard, and the Fortura crossovers were good for their day but hopeless by today's standards, which doesn't make a mini-Heil's job easy. Here's where experimentation with damping methods can pay off.
10) The speaker may or may not sound better with the tweeter's leads reversed. Try it both ways.
Even unmodded, the Forturas blew away Advents and other super-popular speakers of the day-- on the top end. The underdamped (ie, mistuned) low end, however, was something else. Still, with a Dyna 400 amp, they could blow you out of a room without trouble. That's what we did in the '70s-- blow ourselves out of places. That's what it's all about, isn't it?
Here's a shot of one of my Fortura 12s, the one whose woofer I was too late to fix with silicone (probably the wrong method, but hey). That's an inexpensive Eclipse polypropylene replacement which luckily worked reasonably well:
You can see the putty on the pole pieces to try to round some of the sharp edges. What you can't see are the damping wads shoved into the tweeter's slots on the back.
