Bill Fitzmaurice

That's the case with my Superfly. The manual is specific on that fact. Of course that does little good if one doesn't bother to read it.

You may, but they're designed to operate into a fixed driver impedance. Drivers don't have a fixed impedance, for instance a typical 8 ohm woofer may have an actual impedance of 20 ohms or more at the crossover frequency, so the results will be far less than optimal. Designing a crossover is just as involved as designing the rest of the speaker. Both. That's part of why you can't build a speaker like ordering Chinese food, with a woofer from Column A, a tweeter from Column B and a crossover from Column C. But you'd be surprised how many manufacturers do just that. A few years back I designed an award winning 112/6 speaker for a manufacturer. The driver/box design process took a matter of weeks. Getting the crossover exactly right, which included seemingly endless Beta testing by at least a dozen users, took months.

No acoustical engineer would say that. Maybe an EE, but they tend not to be familiar with speakers. They are, and that's not a good thing. There's only one reason to use a 1st order highpass with no low pass, that being it's the least expensive option. You cannot use a rheostat, as it does not present a constant impedance load. One must use an LPad.

That's not a crossover, it's a high pass filter, and a very poor one at that. It only attenuates below its corner frequency at a 6dB/octave rate. Worse, as the power density of a signal increases by 3dB with each octave drop in frequency the net attenuation is only 3dB/octave, which is barely enough to provide any protection for the tweeter. With no low pass filter on the woofer it will still produce enough high frequency content to destructively interfere with the tweeter output. A good crossover will at the very least consist of a 12dB/octave low pass filter on the woofer and an 18dB/octave high pass filter on the tweeter. This is commonly referred to as a 2nd order low pass/3rd order high pass crossover.

You must use a crossover to send the lows to the woofer and the highs to the tweeter. This keeps the impedance correct and prevents the tweeter from being blown. Even piezo tweeters, which are advertised as being able to be run without a crossover, really need one. One reason why they get a bad rap is that they're almost never used with a crossover.

When you add a second identical cab in parallel you get a 6dB increase in both sensitivity and maximum output. That's the equivalent of quadrupling the power into a single cab, so it is most definitely a big change. That would only happen if the two cords weren't of like polarity. The reason why they say not to do so is because it won't add to output, and you might have two cords that aren't of like polarity.

Thermal switches are cheap, being so common on computers, so I don't see any reason to not have one, and they do extend fan life.

If you only leave it on it may not get hot enough to turn the fan on. You probably have to play through it to generate much heat.

What you're dealing with there is the amp gain structure. Time was that some manufacturers would intentionally tailor the gain structure to give more volume at the lower end of the dial, so that when trying different amps in the store their amps would seem louder. That difference would disappear once the volume knob was turned up to halfway, but doing that tended to get you thrown out of the store. With most gear today being bought on line there's nothing to 'gain' from that scheme anymore.

It has nothing to do with Trace. Valves are subjectively louder than SS due to their natural compression, which you can more or less duplicate with SS using a compressor, but not quite. That's because if you use a compressor with SS the compression takes place early in the signal chain, while most of the compression with valves is in the output valves and output transformer.

It will go about 3dB louder with the same amp settings, but maximum volume is no more than an 8 ohm cab, since the cone displacement of the two is the same.

Do that calc again, using the cone radius, not the frame radius. The 4x7 is going to be closer to 100 Sq in. A typical 12 is 80, a typical 15 is 130. Not that this is at all definitive, because excursion is just as important as area, and smaller drivers tend to have less excursion than larger drivers. You can find 12s with 8mm or more of excursion, 7s with that much would be quite rare.

Use this: http://www.loudspeakerdatabase.com/

Because.

That's possible, and you can't assume that any design was arrived at by scientific means. Marketing departments have a habit of specifying target dimensions, driver sizes and wattage ratings with little regard to how well it works, because they're interested in how it will sell. For instance, at one time the Kappa Pro Ten was a popular driver in 'boutique' cabs, mainly as its 500 watt rating could be advertised as a step up from the usual. However, it was designed for PA midbass/midrange, so with electric bass it worked no better than a 250w rated Beta 10 that cost and weighed half as much.

Ideally, but it's not as critical as using the same drivers in very close to the same box volume per driver. That way you avoid the most common mish-mash mess, as typified by the 410/115. That combination by and large doesn't work as intended, as the 410 will usually have higher thermal and mechanical power capacity than the 115, when it needs to be the other way around.

IME WinISD isn't buggy. It has some idiosyncrasies, but they're mainly related to user experience with the program. HornResp is considerably more sophisticated, but it gives the same results. As for the cab volume, remember to deduct for the space taken up by the port. Using two non-identical cabs is always a crap shoot, no matter what their configuration.

True, but if he makes the cab smaller and tunes it to 62Hz, as opposed to leaving it as is tuned to 50-54Hz, he'd lose 4 to 5dB of sensitivity from 35 to 55Hz. I wouldn't want that myself.

'Best' is a relative term. It has maximally flat response in that size cabinet, but with weak low end. It won't be as flat in a larger box, but it will go lower. A smaller box with higher tuning would be appropriate for a PA top that's used along with subs, but not for an electric bass cab. There are none. For that matter in reflex boxes I don't use panel mounted ports, I use corner ports in all four corners. They work better than panel mounted ports, and they brace the cabinet baffle, top, bottom and sides as well.

Put it on the back, or if that doesn't allow the necessary length put it on a side. It will sound the same no matter where you place it.

0.33 is too low for a sealed cab, but that alone isn't why it lacks bottom end. The high Fs along with being sealed is. Sealed cabs don't go low unless you load them with low Fs drivers, and then you trade off sensitivity. If I had to use it I'd use a 45 liter net cab tuned to 50Hz.

They made it sealed because it had to be when that small. When using a driver that has specs suitable for either sealed or ported the ported will always be larger, not only to allow the port to fit inside, but also to allow tuning low enough to make porting worthwhile. That's the trade off to realize the lower extension and higher mechanical power handing that ported gives. While on the subject of mechanical power handling, check the excursion chart. There's no point in using a larger port area to keep port velocity down with more power than the driver can take before exceeding xmax. I won't say I'd be shocked if the SICA can take more than 50 watts, but I'd be surprised.

Buy a set of plans and you can hire anyone you wish to do the build for you. Just don't let them do things their own way. Some of the worst results have come from contracted builders who should have stuck with making furniture, while some of the best have come from first time builders.

The dip is where the distance from the rear of the cone to the front of the cone is 1/2 wavelength. To calculate that frequency divide the speed of sound by that distance, then divide by two. The speed of sound is 13,500 inches per second. It is unavoidable, and why the most popular iteration, the JBL 'Scoop', went away. About the only example of rear loaded folded horns still around are the Danley Sound Labs tapped horn subwoofers. They have the dip, but it occurs above their nominal 100Hz maximum pass band. When they first came out Danley published SPL charts, and the dip, between 120Hz and 180Hz depending on the model, was very obvious at around 12dB deep. Even though that was above the pass band it garnered lots of criticism from the usual wags. When that happened Danley fixed the problem...by cutting off the charts at 100Hz.

I remember Arjank from the days when I still did talkbass. He was always pushing Oberton, as if they were something special. They're OK, but no better than a dozen other brands. The LaVoce WAF 153.00, for instance, is almost Identical, and sells for $160 with shipping. https://www.parts-express.com/LaVoce-WAF153.00-15-Woofer-8-Ohm-293-720 I wouldn't do a rear loaded folded horn. They have an unavoidable response dip where the front and rear waves meet with reverse polarity. That's one reason why they disappeared from the scene thirty years ago.