agedhorse

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. 

12 hours ago, SimonK said:

 

I broadly agree with this - as Biochemist/Biophysicist speaking (at least originally) - there are plenty of biochemical systems that rely on the flow of protons rather than electrons, with the resulting electrochemical gradient measured in volts, so I would say volts are often used to describe the state of a system.

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

13 hours ago, TimR said:

Weird. I thought that moving magnets exerted a force on the electrons, causing them to move. That's the EMF. There's no voltage moving the electrons. The voltage is caused by the  electrons moving from one place to another. 

 

That's why voltage is defined in terms of current, not the other way round. A higher voltage is just where you have a higher density electro magnetic, electro chemical, theromionic field, or capacitive storage.

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. 

1 hour ago, Chienmortbb said:

Volts and current do have to coexist, in a resistive circuit, I think that going into phase shift, reactance etc. is a step too far for here. In fact, things have probably gone too deep for most already.

 

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.

10 hours ago, bremen said:

You do know that you can buy recone kits, and it's not nearly as difficult a job as you might think. I have 46 year old Tannoys and have reconed more than one of them.

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.

9 hours ago, chris_b said:

 

These are custom drivers, made to Alex's specifications, so my guess is that recone kits won't be available. Always worth an email to confirm.

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.

17 hours ago, ossyrocks said:

 

Ok, this is from the service manual. Not sure what this means.

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.

3 hours ago, TimR said:

 

Strictly speaking this is wrong.

 

The volt is defined as the difference between 2 points when a current of one amp flows through a resistance of 1 ohm (although it's expressed as power dissipation 1Watt). 

 

ie the current flow causes the volt difference. Which is a very difficult thing to get your head around and why the water flow/pressure analogy is more correct. 

 

Think of it as lots of blue men on the left piling up trying to get through the tube at the same time, with fewer blue men running off to the right as they pop out of the restriction. While the blue man stuck in the tube gets more hot and flustered and red in the face. 

 

 

Anyway. As you were...

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.

1 hour ago, moley6knipe said:

I’m still very much a large transformer sort of boy

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

4 hours ago, Stub Mandrel said:

If gear fails well out of warranty (7 years) there's really nothing to learn whatever the failure mode.

 

That's into the lifetime where random failures due to small manufacturing defects become possible. No matter what is said about the level and nature of usage, it has to be taken with a large pinch of salt as some people will be scrupulously honest and others may of thrashed it every night but not want to admit it. The have no way of being sure what the speaker has endured.

 

If BF get virtually no failures and they are all beyond warranty, then there is little reason to change.

 

If it was a 7-sigma, safety critical aircraft component it would be different.

2 hours ago, Chienmortbb said:

Agreed and if Airbus/Boeing/Lockheed made speaker chassis they would be carbon fibre. I also agree that 7 years is not unreasonable for a speaker although many will go on decades longer.

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. 

54 minutes ago, Chienmortbb said:

Are those the ones that make Amp Techs have nightmares?

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.

7 hours ago, Woody1957 said:

I get your point, but don't forget the bass players on this forum who have years of pro/semi pro experience, but without the so called technical knowledge that have witnessed otherwise....

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. 

8 hours ago, Dan Dare said:

It seems we're starting to strain at this. Those with years of expertise and experience, such as Bill, Aged Horse and Stevie, have given good advice above, which should be all we need.

 

To summarise, don't abuse your gear, ensure it matches (within reason - a 1000w amp with a 100w cab is almost bound to end in tears, but smaller discrepancies are fine as long as you are sensible) and that you use it within its specified limits.

 

Accept that drive units, as mechanical devices, are going to wear out/fail on occasion. Even electronics components don't last for ever. C'est la vie.

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

4 hours ago, Chienmortbb said:

Very close to a reply that I was going to post, The way to create a 4 ohm load is with two 8 ohm speakers in Parallel. 
 

I would hAve gone on to explain that despite looking like a simple machine, the drivers we use are complex. 
 

When Beyma published power compression graphs, the loss in power stated at way below rated thermal power.  If my memory serves correctly, most LF drivers at least in the Beyma range were approximately 1dB down on power by the time they had been driven to 1/3 of their right thermal power. At rated  power the compression had risen to over 3 dB.

The 4 ohms us that many amplifiers cannot supply the extra current needed to achieve the extra power. If you look at an amplifier spec and it’s 4 ohm power output is not double the 8 ohm power output then it is likely that tbr power supply is not able to supply the required current. 
 

Taken all these factors into account, There is very little to gain, if any, in going for a 4 ohm driver/cabinet. Two 8 ohm cabs, stacked vertically, with a decent amp is much better. 

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. 

15 hours ago, bremen said:

While you're here, could you help bury the myth that a four ohm speaker is twice as loud as an eight, with the same amplifier 😍

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).

On 24/12/2024 at 00:18, NAS Bass said:

Nothing to do with watts. I’ve seen and experienced low powered amps taking out speakers, usually the voice coil, because of a distorted signal. I suspect this may have been the case with the OPs 135w tube head. When I’ve seen it happen, it’s usually been caused by a tube head or distortion effect - nothing to do with power handling. I’ve know this happen with an Orange 120 and an Aguilar 412 - two speaker coils burned out. 

Sorry, this is not true. 

On 24/12/2024 at 01:47, Downunderwonder said:

Do tubes suffer DC offset? That's about the only way 135w can blow a BF woofer while still sounding clean.

 

I wonder if someone else had access to the cab? Either that or it's pure oddball failure of the stuff happens kind.

No, it's impossible to have DC offset on a tube amp, the output transformer prevents this.

On 11/01/2025 at 04:24, Woody1957 said:

Absolutely spot on! Running a high wattage amp on low volume is far better than running a much smaller wattage amp on full volume. 

What you need is an amp with head room and lots of it when playing bass otherwise the speakers will burn out, no matter how good or powerful they are.

Sorry, not at all true.

On 11/01/2025 at 08:22, Woody1957 said:

I'm sorry but my experience says otherwise....an underpowered amplifier driven hard can cause distortion and clipping....speakers don't like that.

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)

16 hours ago, asingardenof said:

BF actually suggest you can run a Two10 with an 800W amp as long as it's clean.

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.

6 hours ago, Bill Fitzmaurice said:

If you want to get rid of that dip it's easy enough, reduce Pe to 200w. It has nothing to do with the cabinet design, it just shows that the driver mechanical limit is lower than its thermal limit. That's not the least bit unusual. For that matter prior to roughly 20 years ago it was the rule rather than the exception. Want to know why vintage drivers were so poor with respect to bass? This is the maximum SPL of the ubiquitous Jensen C12N, which were in my '65 Bassman. If all you looked at was Pe then the 50w rating would seem adequate. Leo Fender certainly thought so. But with 1mm xmax it was mechanically limited to 5w at 60 Hz. 😲

 

 

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.