agedhorse

Actually, balanced inputs do cancel noise that is common to both the + and - conductors, either through an input transformer or differential amp at the input stage. They amplify signal and noise that is not common to both conductors. Balanced is independent of level or connector type (provided it has 2 terminals plus ground… and ground may not be connected at both ends either because it is purely for shielding and not necessary for a balanced system to work.

It doesn't matter if it's protons or electrons, an outside energy force (mechanical, chemical, thermal) is required for there to be motion.

There are only 2 ways that voltage or current can exist without the other, these are both defined as limit or boundary functions... meaning that they are more theoretical than practical (though you can get close under ideal conditions). Voltage can exist with no current flow IF the load resistance is infinite (an open circuit with no parasitic shunt leakage) because I = V/R, and as R approaches infinity, I approaches zero no matter what the value of V. Current can exist when the load resistance approaches zero (a short circuit with no parasitic series resistance) because V = I x R, and as R approaches 0, the voltage will approach zero no matter what the value of I. There is no way to split apart the voltage and current relationship in resistive circuits except when R is either zero or infinity. While the voltage is generated by electrons moving from one place to another, an outside force or element must exist for there to do so. The outside force generates a voltage with no net current if the load is open, a current with no net voltage if the load is shorted and somewhere in between if the load is resistive.

Agreed.

Voltage and current have to coexist (in resistive circuits) until you add reactive elements... then it's possible to have current with no voltage due to the phase shift between the voltage and the current (for AC) because power is stored as voltage or current in the capacitor or inductor. This is an entirely different topic however.

With Eminence, most OEM recone kits are raw kits (unassembled) but only available to the OEM manufacturer and it was a 10 piece minimum (though that may have changed in then last few years). It's more difficult if you need to recone them from raw kits and do them properly to meet the original specifications to last like the original factory drivers. Details matter, and what I see of recone work by end users is usually awfully scary. Correct, I wouldn't expect these parts to be available unless Alex has them. Just because recone parts fit doesn't mean they are correct. The driver may make noise, but will be nothing like the originals. There are some abysmal aftermarket parts kits sold as original out there... buyer beware.

Shipping to the UK has almost doubled in the past 2 years, and the bigger challenge is dealing with UK customs which seems to be punitive to UK citizens. Add to this the VAT that applies on all costs including shipping and you have an unsustainable business model. The EU is similar though not a punitive. After my last battle with UK customs, where the paperwork was affixed to the package clearly marked, they returned it because of incorrect and insufficient paperwork, then lost the package. It mysteriously showed up at my shop 3 months later after their tracking showed that it never left the customs warehouse and customs washed their hand while shipping insurance refused to honor any coverage. Ultimately, after finally getting the amp back to the customer, he paid over $800 USD for a $150 repair (all due to charges and screw-ups at his end). Because of this last experience, I can no longer offer international service (outside of North America) on Genz Benz products. It's a sad state of affairs, and likely to get worse before it gets better.

That's an early 400RB for sure.

Enjoy it at low volume as it is. Maybe you don't need to mess with what's already cool?

Is this a multi-track recording with processing or post-production opportunities. If so, a pre eq DI would offer the most options "after the fact", in post.

Actually, something is required for the current to flow, and that is the volt. Without a volt, and without a resistance, no current would flow. It's like the "which came first, the chicken or the egg?" argument.

You ought to try some of the newer SMPS/class D offerings, you might be pleasantly surprised...

With the benefit of hindsight, I am in the unique position of being able to evaluate the reliability and lifespan history of many of my speaker and amplifier products. Speakers, when powered reasonably can last a virtual lifetime. We have many customers that have used speakers that are 20, 30 and 40 years old without a single issue and they are still perfectly fine. I had plenty of (pro level) PA speakers that I used in a touring environment 4 or 5 nights a week that lasted 20 years without any work necessary and continued to work fine for years after they were sold. All of our speaker products came with a 5 year warranty too, so 7 years is not well out of warranty and I would be horribly disappointed in me designs only lasted 7 years... that's a shameful expectation IMO. Bass amps generally last 10+ years without attention but I am now seeing bass amps in after 15-20 years of hard use that need refurbishment. It's not the SMPS and Class D part that needs work, it's everything else that suffers the wear, tear and handling accidents. Out of a hundred amps a year that I see through the shop, I replace maybe 2 or 3 power modules. So much for the urban myth that "all" modern bass amps are unrepairable/unservicable.

Certainly those who are under-qualified tend to struggle, but qualified pro techs generally don't have many issues. We have factory techs that can turn around 4 or 5 amps a day (depending on the problems of course), but they are excellent and good troubleshooters too. It's no different than for any product, the better qualified the tech is, the easier it is to fix. When I work on class D bass amps, I typically spend less that 1 hour on each amp. I find them easier and quicker to repair than my older class AB/G/H designs.

Don’t forget that sone of us have designed these products commercially for decades and have a much larger view of the results of “player versus speaker” interactions.

Sag is both measurable and subjective. It can be responsible for perceptions that are at odds with what’s really happening. Some of it is related to “perceived compression” and some is due to distortion harmonics that are generated. For some players this is good, for others it’s undesirable.

Reasonably powered, a quality bass guitar driver shouldn't wear out for many decades. Accidental damage and defects are a different matter of course.

Agreed, a 4 ohm load from 2 x 8 ohm drivers does. It suffer from the driver design sensitivity challenges that most 4 ohm drivers face. It’s also not impossible to design an equally sensitive 4 ohm driver, it’s just much more difficult and may trade off against other important parameters.

Driver construction has improved greatly over time, especially the bobbin materials and adhesives used. Also, for bass speakers, more attention has been placed on improving mechanical limits. This means that in general, matching the rms rated power of the amp to the rms rated input of the speaker is generally pretty safe. The main exception to this rule is when using heavy distortion and/or heavy compression. Under these conditions, I recommend some derating of speakers (maybe to 75% of their published rating) but conservatively rated speakers may not need this. There were two parts to JBL’s recommendations, unfortunately they get mixed up in the discussions… the part Bill quoted was for the HiFi industry and addressed the high frequency distortion impacts on tweeters mostly. There was also a section for OEM (original equipment manufacturer) customers regarding low frequency drivers for MI (musical instrument) applications which recommended a 50% derating for use with distorted and compressed program material. This was also incorporated into the OEM warranty agreements. I completed the JBL reconing and service school back in 1978 and worked at a service center that was JBL certified very early in my career.

In theory, it will be 3dB louder BUT in practice, it's very difficult to design a 4 ohm version of an 8 ohm speaker with the same sensitivity (based on power). Typically, the 4 ohm version will be from 1-3dB less sensitive, which offsets the increase in power. Additionally, if a 4 ohm speaker is being driven closer to maximum rated power than the 8 ohm version, there will be some additional losses due to thermal and electro-magnetic power compression.

Just a quick note... a nominal 8 ohm speaker can have different definitions but under IEC-268-5, will have an average impedance of 8 ohms with a minimum impedance of no less than 20% below the nominal value within the defined pass band. In reality, many manufacturers play fast and loose (or highly creative) with this definition, something that amp designers must anticipate (and that regulatory safety test labs will test for).

Sorry, this is not true. No, it's impossible to have DC offset on a tube amp, the output transformer prevents this. Sorry, not at all true. Sorry, not true. Woofers don't care about distortion and clipping as long as the distorted/clipped power is within their RMS rating (and the rating is honest) That's fine until the player has an accident (ie. cable pulled partially out of the bass causing a high power transient event) or the player has a lapse in good judgement that typically goes hand in hand with unrealistic expectations.

If you are looking for a brighter tone with a little sheen on it, the TT-800 will get you there by using the bright switch on the front. That's exactly what it's there for.

Or you can increase the Fb of the enclosure a little bit which will shift the ~43Hz peak upwards a bit while at the same time increasing the max SPL in the 50-70Hz range. If you want keep the LF extension the same (especially F10), then a slightly larger enclosure will offset this. It's very much a balancing act between variables, but IMO better choices could be made. Yes, this was much more common with vintage drivers, especially with extended low frequency tunings.

Because the tuning that produced that plot was a poor tuning choice and one of the impacts is poor mechanical power handling in exactly that region. It's no surprise, and no experienced designer that I know of would choose that either. They would quickly recognize that they were well beyond the optimized zone. This is the plot for an equivalent 212 at 600 watts RMS with an appropriate tuning. Note that the driver I developed had 0.75mm greater winding height than the stock 12PR300 and a different mid voicing, but the majority of the improvement is a better tuning choice. The ideal HPF setting would be 4th order BW, ~50Hz. The cabinet F3 is 57Hz, the F6 is 51Hz, and the F10 is 45Hz.