Bill Fitzmaurice

There's no point. Power and decibels output are only indirectly related. It's called a power soak. Using one is akin to driving with your parking brake engaged so that you can get all the horsepower out of your engine. 🙄

Is that a reference to the women? Or the livestock? 😁 On our side of the pond they had to remove the grass and install artificial turf on the University of Vermont football field, to stop the cheerleaders from grazing during halftime. 🙄

I managed to get a decent level from my Bassman, when I played it through eight twelves. 😳 This was the 60s, when the average twelve had only 1mm xmax. Today it's not hard to find a 212 that has 450cc displacement. The 212 Bassman/Bandmaster/Twin Reverb loaded with Jensen C12s had 80cc. They also had Fs of 112Hz, so going low wasn't in their wheelhouse.

It's the same cab as the 50w Bassman, so it's marginal. The drivers aren't bass specific, they're generic musical instrument drivers. They sound OK at low levels, but that's about it. A Twin is OK for recording, again at low levels. Carol Kaye, possibly the most recorded bassist of all time, mainly used a Fender Concert 410 in the 60s-70s. . If you've heard the Beach Boys you've heard that amp.

True. I mentioned the concept to Alex way back before he started his company, it's called a 1.5 alignment, and he eventually employed it. It's not just to prevent comb filtering in the highs, it also improves horizontal dispersion in the mids. But a pair of 2x10 vertically stacked also has the advantage of getting drivers up higher so you can hear the mids better when close to the cab.

Not that I recommend it, but if you connect the terminals of a 9V battery, the small type, with a screw driver you'll get a small spark. Do so with a 12v car battery and the screw driver will suffer serious damage. It can even get arc welded to the terminals. The difference is due to the ampere capacity of the two. Consider a taser. They run at 30 to 50k volts. They tend to be non-lethal because they have very low ampere capacity. A static shock you receive on a dry winter day can be an upwards of 75,000 volts, but the current is so small that all you might feel is a slight annoying zap. Like most electricians I seldom bothered to turn off the breaker to swap out an outlet or switch, and as a result got zapped dozens of times over the years. Smart? Maybe not, but that's what we do. I once stuck my finger in the wrong place in a Fender Bassman and got the full 470v. Unpleasant, but not injurious. Still, that experience educated me to the value of using a bleeder resistor to drain the caps before messing around. 😳

Leave it on the road case. Whether you go with a second Midget or some other cab with multiple drivers you want them vertical, not horizontal. It sounds better that way, to you and to the audience.

Not necessarily lethal, and it's not the voltage that kills, it's the amperes. Still, getting zapped with even 450v isn't a pleasant experience. One thing to do is to turn the power and standby switches on, with the amp unplugged, before removing the chassis from the case, especially the standby. When the standby switch is off the power supply caps will hold their voltage for a long time. With it on they'll discharge, albeit slowly.

Clean everything with contact cleaner, including the pots, tube sockets and tube pins.

Don't do anything until you get the cab and at the very least post the pictures. The Delta 12LFA is a subwoofer driver, best for electric bass when mated to midrange drivers. The BN12-300 is unsuitable for electric bass, at only 2.5mm the xmax is far too short. As for OEM versus Eminence branded, when Eminence creates a new driver they test a number of variations. The ones that test the best are the ones that end up being sold under the Eminence brand name. I've seem some OEM Eminence that were pretty good, but I've seen some that were pretty bad. That includes one relatively well known manufacturer's version of the Delta Lite II 2512. 🙄

Post a picture of a driver. Also post the exact dimensions of the cab. The only way to know what will work well in any cab is via loudspeaker modeling software, which allows for reverse engineering.

A harsh tweeter is an indication of high THD, which can be sourced by the amp and/or the tweeter. When it's the tweeter the usual reason is a poor crossover, which allows far too much low frequency content to reach it. The only thing most manufacturers go cheaper with than the tweeter is the crossover.

That's one of the most basic calculations. Where the barrier is at least one wavelength high sound is reflected back. Where it's less than one wavelength high sound goes over it. One wavelength at 100Hz is about 3.5 meters, so reducing transmission above 100Hz isn't difficult. One wavelength at 50Hz is about 7 meters, so reducing bass is impractical.

Start here: https://blog.soton.ac.uk/soundwaves/ We have difficulty understanding sound because of our assumption that sound waves behave in the same fashion as light waves. They don't. Not only do speakers as sound sources not behave like lamps behave as light sources, they behave differently at every frequency. That means the first step in knowing how speakers work is to learn how sound waves work. That would be easy if anything about sound waves was intuitive, but almost nothing is. Much of what intuition tells us is incorrect.

It could be done, but not by auditioning cabs. If you have the full specs on cabs it is possible to predict how they'll work together. The problem there is that full specs, including FRD, Z and phase response charts, aren't available for any cabs.

I understand the science, and that's why my advice is never mix cabs. Doing so is just like what Mama Gump said about a life and a box of chocolates: "You never know what you're going to get".

Yes, if that's what the amp and cab are configured to use. It would be in your manual.

Even perfectly shielded single coils will buzz, while reduction of buzz when touching the strings or bridge is normal. Blame it on whoever invented the magnetic pickup, making it high impedance to avoid the need for an additional gain stage in the amp.

You probably wouldn't be able to tell them apart. Back in the day we all found it odd that you couldn't hear any major difference between a Bandmaster, Bassman, Twin Reverb or Dual Showman when played through the same speakers. That was long before we knew about decibels and logarithmic hearing response.

It's not complicated, if you know how to use speaker modeling software, like WinISD, the process takes less than ten minutes, if you have the specs. IMO every speaker should make them available. Every driver manufacturer does, but that opinion isn't shared by the cab manufacturers. 🙄

It would be a simple matter to calculate the OBC 112 frequency response, sensitivity and maximum output using the driver Thiele/Small specs, but since there's no way of knowing what they are you're back to comparing it to other cabs the old fashioned way, trying them side by side.

The amp rating is moot, the transformer only powers the pre-amp tubes. I agree that the only reason it would blow is if there's something downstream is drawing a lot more current than it should be.

Based on the size I agree. You may find numbers on it if you pull it.

No. First off the position of the volume control doesn't indicate the power output. Depending on the level of the input signal halfway on the volume control could be full power, could be 1/10 power, could be clipping. Then there's the matter of the impedance load, which isn't constant. A nominal 4 ohm load will have an actual impedance anywhere between 3 and 30 ohms, depending on frequency. Power varies with impedance, so with 20 volts output the power can range between 13 watts at 30 ohms to 133 watts at 3 ohms with the same volume control setting depending on the note being played. Lastly, perceived sound levels are logarithmic with respect to power, not linear. To sound twice as loud doesn't take twice the power, it takes ten times the power. As for measuring power output, to do so requires simultaneous measuring of voltage and current, which requires two separate meters and a method to extrapolate the result, which will still vary with frequency. Engineers don't even try. We measure voltage, which is constant into any impedance load. We know the voltage output that an amp can cleanly deliver, and the voltage limit that a speaker can cleanly handle.

It works for their material. He's no slouch. I saw a video of him playing 'Roundabout' with 'Yes'. Not everyone can play like Chris did. Geddy nailed it, including the tone.