Bill Fitzmaurice

Impossible to qualify? Maybe. Impossible to quantify? Hardly. Watt, unit of power in the International System of Units (SI) equal to one joule of work performed per second, or to 1/746 horsepower. An equivalent is the power dissipated in an electrical conductor carrying one ampere current between points at one volt potential difference. Source: Encyclopaedia Britannica

A perusal of the history of Behringer's shenanigans gives said claims plenty of credence. But if you must, look at the power consumption of the amp. It's 880 watts. That means if the Bugera/Behringer claim is true it puts out more than twice what it draws from the wall socket. That either means they're deliberately lying or they failed to pass grammar school level physics.

What about valve amps? I fully understand how the use of compression can give the subjective impression of one amp being louder than another of the same rated power. That's what valves do. That's not the point. False advertising is.

They only get away with what we let them. Reference the TC watts controversy, when TC was caught red handed flat out lying about their power specs. You'd think that universal condemnation would have followed, yet a substantial percentage of TC owners defended TC, saying in essence that they didn't care if they were lied to, so long as the amps sounded good.

With a properly tuned port cone excursion will be less, not more.

That depends. Adding 8dB increases power delivery by a factor of 6.3, and cone excursion by a factor of 2.5. However, your bass doesn't create equal output at all frequencies. At 40 Hz it's probably at least 8dB lower than at the 2nd harmonic at 80Hz and the third harmonic at 120Hz, so all that 8dB boost might be doing is making the 40Hz, 80Hz and 120Hz content more equal, thus the source of the term 'equalizer'. If boosting the lows causes distortion don't boost them. If it doesn't you're probably OK.

Higher xmax is only a benefit if you have enough power to make use of it. The frequency plots you're looking at on data sheets are with the drivers mounted in a wall, not an enclosure. In your 17L enclosure with 85Hz tuning the 18Sound has only slightly higher maximum output, a bit less sensitivity, and similar response in the lows. The 2510 is considerably better in the mids. As for getting lower response, in short, not with that cabinet.

You won't lose any bottom end, and if anything boom will be reduced. You might lose some low end with am open stand that high, but the solid front of the case acts as an extension to the baffle to prevent it.

IMO never mix cabs. Find one cab that has the sound you like. If it's not loud enough use two.

The difference in sensitivity with 4 ohms versus 8 ohms is only 2dB. The difference in maximum output between the two is 0dB. There are a lot of factors that determine how well a cab will work. Impedance isn't one of them.

If we go back to 1965 that scenario was more or less the case. Fender, for instance, used the Jensen C10, C12 and C15, similar in all aspects save cone size and Fs, so the fifteen went lower than the twelve, which went lower than the ten. By 1975 driver options had expanded to the point that one could no longer make any judgement on potential response based on driver size.

+1, and where low frequency response goes it doesn't matter very much. This charts three speakers, one loaded with a ten, one a twelve, one a fifteen: If you were to believe the size matters crowd you'd have to think that the red line is a fifteen, the blue line a twelve, and the green line a ten. You'd be 33% correct. The blue line is a twelve, but the red line is a ten, the green line a fifteen.

Insufficient data. Only by seeing a measured SPL chart can you know what's really going on. If only manufacturers posted them, but none do.

The combination might work fine. It might not. There's no way anyone can tell you what the result will be. The only valid method of comparison would be to have the 210 plus 15/6 and the 2x210 side by side. Otherwise it's all pure speculation.

Since we're still on this subject, no, you shouldn't presume that. For every manufacturer that does the required research another just tosses drivers into a box. The only factor determined by cone size in and of itself is the dispersion angle. It goes smaller as frequency goes higher, based on the size of the cone relative to the wavelength produced. To keep dispersion as uniform as possible as the wavelengths get shorter the cone size must get smaller. That, and that alone, is why midrange drivers are smaller than woofers, and tweeters are smaller than midranges. Of course the driver T/S specs and other pertinent features are optimized for the driver pass band, but those are secondary concerns, as no matter how well optimized they're of no use if the cone size is too large for the pass band to be heard other than directly in front of the driver.

I wouldn't be too concerned, the stand would have to be closer to 60cm to have a major effect.

That's correct. A single 12cm diameter round port is usually sufficient for a 15 inch driver. Split into four 6cm ports you might get some chuffing. The added area of four 10cm ports prevents it.

This calculates the effect of lifting the cab: http://www.tonestack.net/software/floor-reflection-simulator.html The higher it's lifted the lower the frequency of the floor bounce induced cancellation.

If you lift the cab more than 20cm or so off the floor you'll introduce floor bounce phase sourced cancellation in the mid bass. That can be beneficial on a boomy stage, so in that instance it's a good idea. But otherwise it's best to leave the cab on the floor, tilted back to aim the drivers at your head, the better for you to hear your mids and highs.

Assuming the total area of the four ports was the same as the area of one port that result is to be expected. There is an area of high friction close to a port wall. That can cause chuffing noise with multiple small ports or narrow slot ports, which put the center of the port closer to port walls. It's easy enough to cure, by making the port area larger when those configurations are used.

You'll want to play around with the tuning frequency some more, trying at 55 and 60Hz as well. Keep in mind to calculate the volume taken up by the ports, which gos down as they're made shorter for higher tuning. That adds to to box volume, which changes the overall result. It takes a while, but it's worth it to find out what the various tuning options will result in.

The program models the port, you just enter the desired resonant frequency.

50Hz tuning would be better, but you can't change the driver specs with tuning, and that's why I would not use any of those drivers, other than the B&C I posted, in a stand alone bass cab. I'd only use them in a PA system where they don't operate below 100Hz, that range being handled by sub woofers.

No chart required. When you change the signal level or EQ by 1dB at any point in the signal chain, be it the bass itself, a pedal, in the amp pre or amp EQ or anything plugged into an effects loop, the change at the amp output will also be 1dB. A 2dB change in the signal chain is a 2dB change at the output, a 3dB change in the signal chain is a 3dB change at the output, and so forth. Turn up the mids. That's because the configuration of the JBass pickup give less low end than the PBass pickup, which translates into more mids compared to lows with the JBass.

That's mostly correct. Doubling the impedance load reduces the maximum power delivery by about 40%, not 50%, with a reduction in maximum output of perhaps 2dB, a negligible amount, assuming no change in speaker sensitivity and/or frequency response. That last bit is the key factor. What you're experiencing indicates that the sensitivity and/or frequency response of the 210 is not equal to that of the 115. It's all about sensitivity and frequency response.