Bill Fitzmaurice

Thicker foam of lower density can be beneficial on particularly soft stages. But too thick can result in the cab rocking. Spikes don't do anything useful from a sound standpoint. Where they can be beneficial is on a carpeted floor, gripping through the carpet to prevent speaker 'dancing' at high power levels, especially long-excursion subs. The quasi-magical properties attributed to them by some are just more audiophile piffle.

Mechanical decoupling is an audiophile myth. What vibrates the stage is the acoustical output of the speaker, not mechanical coupling from the cabinet, which would be the tail wagging the dog. What can occur is that the vibrating stage will cause the cabinet to vibrate. The best way to prevent that is with a piece of yoga mat. More on the subject: https://ethanwiner.com/speaker_isolation.htm

Translation: It has low sensitivity. To put that into context a 3dB sensitivity difference requires twice the power for the same output. 6dB requires four times the power. IMO knowing sensitivity is very useful, as are frequency response and displacement. Without knowing these one cannot make an objective comparison with other products, and that's the point. 😒

There's no replacement for displacement. Well, there is, horn loading, but then you're talking about a much larger cabinet. The displacement of a premium 4" driver is around 30cc. A middle of the road 8" is around 75cc, a middle of the road 10" is around 150cc.

+1. Kick is big bottom, not much low bass or mids, but with an upper midrange for the 'click'. Mids on the kick not only compete with the full mix, yourself included, they compete with the toms and snare.

Keyboard players who lean heavily on the lower keys are the worst. It turns everything to mud. They're supremely guilty of playing what sounds best when they're alone.

That applies to bass players as well. Full lows and moderate mids sounds great, be it at home or when playing alone on stage. But it's not always that way when the full band kicks in, nor when you go out into the room.

With respect to using XSim, it's not a modeled response per se, as it uses the measured response and measured impedance of the drivers to arrive at the result. All it does calculation wise is to plug in the effect of the crossover components, so it's as accurate as the tolerance of the components used. Having used it myself I can attest to it's accuracy, which is also better than a traditional calculator as it can account for the ESR of both the inductors and capacitors.

An alternate driver is the 18 Sound 10NW 650 16 ohm. In the same enclosure it has better than 6dB more maximum SPL through the critical 60-80 Hz range than the Celestion, while the 16 ohm coil gives an 8 ohm cab with two parallel wired. That 6dB translates to one 10NW 650 equaling two BN10-200x. The Pulse xl10-20 is good in the lows, but the mids are a bit spotty due to the lower Fs. I'd use it in a sub.

Four corner ports work best, as they do double duty as braces. The 70 Hz displacement issue doesn't affect frequency response up to 100w. Above that response would no longer be linear. Usually poorly. In any event the 115/410 combination makes no sense. The standard reason for using it is that the 115 improves lows while the 410 improves highs. But 115s don't necessarily go lower than 410s, 410s don't necessarily go higher than 115s, especially off-axis. Most 410s have more driver displacement than most 115s, so where volume is concerned two 410s will usually go louder than a 115/410. The right way to get maximum lows along with the best highs is achieved with different size drivers operating in different passbands. PA and Hi-Fi have used that configuration for 50 odd years. A few electric bass cabs do so, but very few. To say that electric bass cabs are lagging behind the curve is putting it mildly.

'In phase' implies that one needs the phase response of the drivers to be the same. That is pretty much impossible. But it doesn't matter. All that matters is that they're not 180 degrees or close to that apart at or near the crossover frequency, and as such a simple polarity reversal of one driver is the usual fix. As for crossover design, that used to be a seat of the pants job. You'd start with a calculated component value, but to get it perfect required repeated component swapping and testing to dial in the final result. That hasn't been the case for quite some time, thanks to software like XSim, which unlike traditional calculations doesn't rely on the nominal impedance of the drivers for the calculation but instead uses the full frequency response (FRD) and impedance sweep (ZMA) plots to get an exact result. The only issue with that is finding FRD and ZMA files for the drivers, which are only gradually finding their way onto manufacturer driver data sheets, though you can measure those yourself with the necessary gear. Crossover modeling software is to crossovers as speaker modeling software is to speakers.

They model best in a 70 liter box with port area of 200 sq.cm. and length of 25cm. The box volume is net, not including the volume taken up by the port and the drivers. The main limiting factor is the 4mm xmax, which limits input power to only 100w per driver at 70Hz, which is in the middle of the critical 2nd/3rd harmonic region. A driver with 5mm or more would be better. If you have two cabs the xmax should suffice.

What software are you using to come up with the design? And what criteria to choose the drivers? For simple ported or sealed cabs I use WinISD 0.7. I consider not only frequency response but also sensitivity, maximum power (determined by Pe and Xmax, whichever is lower), and port velocity (no more than 20m/s at full power within the nominal passband). I choose drivers based on their cost effectiveness while producing the desired results. Also note that software is only effective within the region of pure pistonic function, which is roughly two octaves above Fs. Above that you must use the driver data sheet SPL chart. And that only gives you the raw numbers. Turning those into a cabinet design relies mainly on experience to know what works best. As for mixing drivers, it's like a box of chocolates: you never know what you're going to get. Sticking with one insures that you will know. I ignore when people say that 'this 115 and that 410 work a treat', because virtually any two speakers together will work better than either on their own. The only way to know if any given pair of mismatched cabs/drivers work better than two of each matched is to try all three combinations side by side. That's fine if you have two of each, but if you don't it's an experiment you can't undertake. Don't sweat tuning for the low B note. While the fundamental is 31 Hz the bulk of the content is in the 2nd and 3rd harmonics, 62 and 93 Hz. No one ever complained about an Ampeg Fridge handling low B, and its F3 is 58 Hz. I never tune bass cabs lower than 45 Hz. I only go lower than that for PA subs.

A bit of semi-interesting stuff is the design of the Altec A-7. The woofer horn had two purposes. One was increased sensitivity in the lower mids, but the other was to time align the acoustic centers of the drivers. The aligning procedure was to wire the HF driver reverse polarity, feed the speaker with a sine wave at the crossover frequency, then slide the HF horn on its sled atop the cab back and forth until the SPL reading was at a minimum. That placed the acoustic centers of the drivers correctly. Swap the polarity on the HF driver back and it was good to go.

The wider the source the narrower the horizontal dispersion. It's why midranges are smaller than woofers, and tweeters are smaller than midranges. Side by side placement reduces the horizontal dispersion by half compared to vertical at the lower end, and raises the potential for combing at the upper end.