agedhorse

None of the Subway amps require a load to operate safely.

Distortion and square waves don’t obliterate speakers any more than an undistorted signal of equivalent RMS power, and in fact is easier on a speaker mechanically. A square wave of the same peak voltage as a sine wave has twice the thermal power but the same mechanical power. This is probably the root of most misunderstanding about the topic. Now peak power is something entirely different, a sine wave always has a peak power that’s double the RMS value, it’s purely two ways of using math to describe the same thing.

Just following up with a conversation w/ Dave over on TB so that you have a better idea about what's going on. I just heard about this decision this morning, I'm really sorry about this. The compliance issues aren't the issue with the bass gear as they are already globally compliant, but the supply chain pressures just won't let up. As soon as we solve one shortage, something else comes along to create a new issue and it's darn near daily these days. The decision was made to wait until these problems are resolved (on both the guitar and bass side) before re-starting things in the EU and UK. It's understandable why they made this decision, I absolutely acknowledge that it's frustrating for you (and for me too, for different reasons). We are seeing lead times on a few parts approaching 60 weeks, and lead times are increasing on some parts that already have scheduled delivery dates, it's a moving target. It's something that's out of anybody's control, and it's even worse on the guitar side with tubes and certain specialty capacitors/resistors, alternate sources of some parts affect safety compliance and require new approvals. Again, I am as sorry as you guys are about this, and I appreciate the few PM's I have received that were refreshingly respectful.

Just to be clear, I have designed products for many brands and at different performance levels. Fit/finish, quality of the covering, hardware and grille are all part of performance, as is size and weight, sensitivity, bandwidth (which tend to go along with higher quality, more expensive components). This has nothing to do with "barking my wares", as you have no idea who I have designed for other than what I have disclosed in my profile. Please stop with the personal attacks, I don't know what I may have done to you to deserve this, but it goes beyond disagreeing.

It doesn't matter where the distortion comes from, the distorted signal and the level is what matters to the speaker.

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I comprehended what you wrote plenty fine and you were clear in your assertion of both drivers and cabinets. As a designer, I have designed commercially many cabinets including high end cabinets, middle of the road and those designed to a strict budget. There is an easily measured difference in all aspects of performance (as well as weight, fit/finish, quality of covering, hardware and grille) that goes along with the difference in price. Real designers/engineers don't use vendor suggested cabinet designs because they have as much understanding of the principles behind the designs as the vendor's designers, and some of us have designed drivers as well when that's what's necessary to achieve the desired goals. Software (especially notoriously buggy software like WinISD) does not make somebody a true speaker designer. Understanding the way the various parameters trade off, the real world implications of what something looks like and calculates out to real world performance (and reliability) goes back to the basic principles, the math and a lot of experience. I agree that matching of the box to the driver is important to the total performance, but when you take a higher quality driver in a well designed box it will generally outperform by a wide margin a lower quality (or "budget") in an equally well designed box. This is why some products use more expensive components, because some players are looking for better than average performance, fit, finish, etc.

If this were the case, if there was little difference in drivers, then why would some designers choose expensive drivers over cheap drivers? Because in most cases, drivers with higher performance cost more (sometimes a lot more). Yes, driver performance can be very different from model to model, and some designers actually have a good idea of what players are looking for and are willing to spend to achieve this. You just don't know this (yet). Fortunately, I can design around whatever performance I need, and the cost doesn't matter all that much for our customer provided the speaker delivers the necessary performance in the size and weight box that the player is willing to accept. It's actually nice to design around performance and not have to worry about the cost (within reason), and for those players that feel that the cost is more important than performance, there are plenty of other options out there.

250 watts RMS is a (reasonably) clear term meaning that it's the thermal limit without the additional information regarding mechanical limits. Anything beyond this is speculation, and if you were to damage the cabinet with 500 watts, the question would then arise about what that 500 watts really means in terms of any warranty coverage. Now it's possibly that the 500 watts is being used as a representation of "program" power handling, but since program power is generally a thermal rating as well, in practice it really represents a reduction in the crest factor of the test signal waveform (an increase in thermal duty cycle). It clearly does not apply to distorted signal, from my reading of that statement. Regarding the use of the amp in question, I would recommend a healthy dose of caution and good judgement. The ShuttleMax 9.0 is rated at 500 watts RMS into 8 ohms, certainly enough to cause damage without good judgement.

Is the 300 watts in the marketing material "RMS" or "program" (2x the RMS value) or "peak" (4x the RMS value)? The details are important.

That’s too bad, but it is a fairly heavily voiced amp, and if the voicing isn’t your cup of tea then it’s not a good choice. Thousands were sold and there is still a robust used market for these amps.

I still get £261 with the courier fee, does VAT actually apply to the cost of shipping? I thought it was just materials and labor at the retail level. Generally, repair labor is excluded from our sales tax, only the materials are taxed. Slowly we are creeping up to European levels, some areas of our country are now over 10%.

By my math, it’s about 250 not 300.

When a resistor fails, it's almost always collateral damage from other failures that are not visually obvious. Replacing the resistor just burns up another perfectly good part and ultimately causes additional damage.

Parallel amp mode is 2 separate channels driven by the same signal of the same polarity. This requires a speaker on each amp channel. Bridged amp mode is 2 amp channels, driven by a common signal with opposing polarity. A single speaker load is placed between the speaker outputs of the two channels.

I worked as production manager for Robin on a new project less than a year before he died. Brilliant, intense and a classic example of burning the candle at both ends. Very, very sad.

I show around +/-56V

Actually, voltage, current, impedance and power are directly related and can not be separated. Double the voltage into the same nominal impedance and the power quadruples, that's non-negotiable. Power factor, or the phase angle between the voltage and current doesn't really matter because it applies equally to both situations. Power = Voltage squared divided by the nominal impedance. The reason the power quadruples when the voltage doubles is due to the squaring of the voltage. Bridging carries the risk of one of the two speaker conductors being accidentally connected to ground. Because the output of the amp is not ground referenced, grounding either terminal can damage the amp. Some amps are designed from the ground up to be bridged, these are generally fairly tolerant of real world loads. Some amps bridge as an afterthought, these tend to be more vulnerable. Many class D amps are designed using bridged topology, in part to improve the power supply efficiency when driving inductive loads. This is an important part of some of these amps.

No Genz Benz amp was ever a Fender designed or built amp.

Sorry, I will need to look in the archives.

There are multiple voltages, +/- main rails, +/-15V and +24V

On the amp, the channel 1 input sensitivity control should be set all the way up (fully clockwise).

There is almost no rare earth elements that are used for magnetic structures also found in other electronics (including semiconductors). The rare earth elements that are used for speaker magnets are also used in all kinds of motors, generators and actuators. These devices are found throughout industry, transportation and also within electronic products (such as vibrator motors, haptic actuators, etc.). The speaker industry competes directly with these other heavy hitting players in sourcing the material.

That's a (very) far cry from a square wave. On a sine wave (a fundamental with no harmonics) it looks more "spectacular" than it is, but on a complex (real world bass) signal, the signal is built up of varying amplitude sine waves comprised of the fundamental and its many harmonics. Because the amplitude varies by a large amount between component signal elements (which is what makes up the envelope of the composite signal), clipping affects only some of the signal.

A couple of things to try... Does it make this noise with either the 410 or the 115? What are the cabinet impedances? What are the amp's minimum allowable load impedances? Are you SURE your cabinets haven't been modified or repaired incorrectly? Different amp types have different protection circuits, some can cause the noise that you are describing.