agedhorse

Things get super exciting when neutrons move...

The simplest and most well known example of off axis extension is the Duraluminum dust cap that attaches directly to the bobbin. It radiates the HF component of the signal like a 4” driver. The Duraluminum material is the same material that jBL developed for use in high frequency compression drivers. A wizzer cone is not a separate transducer, it’s just a specialized dust cap that attaches to the top lip of the bobbin just like the JBL aluminum dust cap. How well the HF energy coupled to the secondary radiation device determines in part the effectiveness. Decoupling the dust cap from the bobbin can be used to alter the response, as does the choice of materials.

There’s the basic premise of destructive interference due to the diameter of the driver versus the mid-high frequency wavelength, but this is modified by the size/shape of the dust cap and the geometry of the cone. With the right choices, the mid polar pattern can be altered more than an octave above what the basic predictions suggest. this can be taken to an even higher level by the use of a “wizzer cone” dust cap.

700 watts RMS is 1400 watts peak and 2800W peak-to-peak. You forgot the squared factor in the formula.

Yet there are several mechanisms that are used to improve off axis high frequency extension. This is why some 15” designs are better than others in this regard.

It could be any number of issues. If the OP is in the US then any QUALIFIED, Ampeg authorized service center should be capable of properly diagnosing the fault (the first step in any repair) and then repair the amp. If the OP is in the UK, Surrey Amps is qualified and capable of handling the diagnostics and repair.

As you have probably learned, a little reverb on bass goes a long way, and just a little too much can quickly become a bigger problem than what you are trying to solve.

Cooling an amp in a way that's effective, quiet AND reliable is a lot harder than it appears. The fans that are featured as "super quiet" usually do not have the airflow , especially under any static pressure losses that a cooling system presents. The D-800 has a fairly expensive ball bearing fan that's reasonably quiet (not as quiet as the sleeve version by a dB or two) but is very long life (about 50k hours compared with about 5-10k hours of a typical sleeve bearing fan). It also runs continuously at a slow speed because the resulting air flow allows multiple components to stabilize thermally together as a system. It's extremely unlikely to ever run any faster than the slowest speed, even at 2 ohms. Back about 15 years ago, when I was working at another company, I led a research project (with the cooperation and support of ICEPower R&D) that specifically addressed a whole slew of thermal and dynamics/duty cycle management design approaches, which resulted in a US Patent relating to this application. Some of what we learned, and how they relate to bass guitar ended up being incorporated into the newer ICEPower modules.

Very few intended as a gigging amp, because live, reverb generally causes more trouble than any benefits it might bring. For recording, that's a very different application. I find that it usually works better to track dry and then add verb at mixdown so that it can compliment the bass in context of the mix. What sounds good solo often conflicts with the mix and muddies things up in the low end.

In general, when buying new, you get what you pay for... and if a product's claim looks too good to be true it's worth further investigation to determine how untrue that claim might be.

With the DI in the "direct" or "pre" modes, the HPF shouldn't affect the DI out. Unfortunately, their owner's manual block diagram forgot to include the bottom control, so there's no way to know if it's supposed to be applied in "post" mode.

Agreed, it helps to explain why it's becoming difficult for manufacturers to provide replacement parts at a reasonable cost. For many parts, we could give the part away for nothing but the shipping would make it too expensive to justify. In many cases, it's not because the manufacturer doesn't want to help, but because the way trade is changing, it's sometimes simply impossible to help in a meaningful way. It can also apply to American customers trying to get a replacement part out of Europe these days.

It seems to have changed after COVID, it used to be ok.

I totally agree Bill. I see it when I'm forced over to the guitar side to help out with support, and some of the comments players state as fact would take your breath away... they are really that gag-worthy.

We must also remember that there’s a lot of incorrect and terrible advice given through YouTube and other such platforms.

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.