... really just an overgrown kid, who thinks designing and building speakers is way more fun than any real job. I count myself extremely lucky that what I can do lines up with what some bass players are looking for.
Have you considered using a series speaker cable or box for a combined 12-ohm load? This would lower your amps max output level, but the rig should still be fairly loud with the addition of the second cab. It's not an Ideal solution, but would be safe for your amp.
I've seen posts warning of possible crossover issues when connecting 2 cabs together in series like this, I have no idea If this might be an issue with Dukes designs or not.
Running identical cabs in series should be no problem. Running different cabs in series can give rise to a frequency response problem if the impedance curves are very different. Let me 'splain:
Suppose one cab has a huge impedance peak at 1.5 kHz and the other does not. When connected in series, that impedance peak will reduce the output of the other cab in that region because less wattage makes it through. Not the end of the world, but maybe something to consider.
Also, suppose we put 600 watts into a 4-ohm and an 8-ohm cab wired in series. The 4-ohm cab will see 200 watts, and the 8-ohm cab will see 400 watts. This is because the 4-ohm cab essentially has an 8-ohm resistor in front of it, but the 8-ohm cab only has a 4-ohm resistor in front of it (oversimplification). So we need to keep an eye out for uneven power distribution.
What DOES NOT HAPPEN is, the amplifier damping factor is not degraded such that either speaker now sounds boomy. Our intuition would tell us that this is a problem, and JBL even wrote an incorrect paper years ago that has perpetuated this myth, but here is why it's a myth: It's not really a resistor that's going in series, it's a fully powered voice coil. And while the control that the woofers have over their voice coils does decrease as the series resistance increases, it also increases as motor strength increases. So when we connect woofers in series, the series resistance goes up but so does the motor strength, so it's a wash. The effective woofer parameters do not change with identical woofers in series, and only shift a little with different but generally similar woofers in series, but the net effect is still a wash.
Question: I seem to recall Duke once saying that using port plugs in an "unbalanced configuration" (for example, a TC112 with only 1 plug) could, at loud volumes, make the driver rock or something bad. Is that no longer true, or was he just being cautious?
I had that problem with the prototype for the Thunderchild 112, but the ports were in a different location, way off-center, up behind the horn, so the air-load was asymmetrical. I tend to warn people that it might happen because I don't know for sure that it won't when you plug like one port in the TC112. That being said, I have never heard back from anyone that the problem occurred, which would have been a clicking sound as the voice coil tapped against the side of the magnetic gap inside the motor. Actually it was SpankyPants... ahem, make that Mister SpankyPants... who was the first to detect it, as I recall. I didn't find out what it was until later, when I talked with the great woofer designer Jerry McNutt of Eminence, and he suggested the port configuration that I now use.
Hi Duke,
Will the 1553 cab be available without the rear firing 3"?
Looking for a 4 ohm 15 with a paper cone mid driver.
Any idea of weight, dimensions and price?
If I get feedback from my beta tester(s) telling me that the rear-firing 3" is unwelcome sometime, then I'll consider either puT a switch on it or offer a version without altogether. But by way of example, to the best of my knowledge no one has found the rear-firing tweeter in the Acoustic Friendly versions of the Thunderchild cabs to be detrimental. It can get buried in a loud mix, but far as I know it never outright sucks.
Now the rear-firing 3" mid inevitably contributes to the price I will charge, and I can see that being an issue. It is possible that I might do a lower cost 115 cab that would forego the open-format mid chamber thing entirely, and just have a conventional sealed-sub-enclosure for the 5" mid. In that case, the only thing "special" about the cab would be the voicing of my custom 15" woofer, and maybe that's enough to make it competitive, I don't know.
Dimensions are 27" tall x 18" wide x 14" deep, the width being 18" instead of the minimalist 17" so that a Hathor 1203 can recline on top. Not sure of the weight or price yet, and I can't post the price here anyway.
If you contact Chad directly at The Bass Shop, just let him know you're a TB member for $100 off. I just sent him an email advising him of this.
