Bill Fitzmaurice

[quote name='flyfisher' timestamp='1326207372' post='1493798'] I can't see valves disappearing unless demand really does disappear. [/quote]Demand already has disappeared. The music industry alone uses tubes, and it's a very small industry in the grand scope. The largest consumer of tubes was the military, and the reason former Eastern Bloc countries continued to produce tubes long after the West stopped was that their militaries still employed them. Once all the Soviet era military hardware using tubes has been retired so will the tube, as few musicians would be willing to pay the 50 pounds each that a 12AX7 will eventually go for. Eventually the tube will go the way of photographic film.

[quote name='kennyrodg' timestamp='1326186421' post='1493339'] It makes me wonder why it's 8ohm in the first place [/quote]Good question. None of the drivers recommended for it are available in 4 or 16 ohm.

[quote name='jackers' timestamp='1326198111' post='1493560'] This is true. China have almost all of the worlds supply of rare-earth metals, so they have a monopoly on neodymium, [/quote]Rare earths aren't rare at all, and most of the world's supply is outside of China. It's only rare earth mining and manufacturing that's concentrated mainly in China, a situation that is changing by the day. The current neo shortage won't last. Tubes OTOH are going away, it's just a matter of time. Producing them without destroying the environment is just too expensive, and when the Russians and Chinese finally wake up, smell the coffee and institute safe manufacturing regulations tubes will be history.

[quote name='kennyrodg' timestamp='1326038442' post='1491390'] Hi Bill, Thanks for coming along. i want to run the cab at 8ohms then I have the option of running another cab for larger venues if required. If you there is no need or a better option for me i'd appreciate the advise. See forum title=Numpty Thanks, Pete. [/quote]You'll likely find 4 ohm or 16 ohm drivers hard to find. I don't know of any off hand, neo or ceramic.

[quote name='kennyrodg' timestamp='1326031286' post='1491247'] run the can at 8ohms. [/quote]Why?

Output is limited by displacement. You can read about it on the Barefaced site. But you won't be able to compare the displacement of any other cabs to Barefaced cabs, because only Barefaced publishes their displacement figures.

[quote name='cytania' timestamp='1325485856' post='1483527'] I still wonder about getting some drummer headphones and standing there looking a noob like Paul Gilbert or Keith Moon (or do they look cool?). [/quote]Danny Seraphine used headphones back in the 60s, for a very good reason: foldback monitors had not yet been invented. No one ever accused him of being a noob.

[quote name='Mr. Foxen' timestamp='1325462303' post='1483451'] "Wattage" also relies on the cabinet since it varies with impedance, hence voltage swing, since that is the what the amp provides. [/quote]+1, and that's another reason why even rating amps with watts is of dubious value. They should be rated by voltage swing, just as light bulbs should be rated by lumens, which completely removes the fudge factor. But that's very much diametrically opposed to the goals of marketing.

I wouldn't take the amp volume all the way up, that leaves the door open to an untimely accident. Experiment with the bass volume. Turn the amp down to a low level, bring the bass volume up until you hear the clipping. Back the bass volume off enough to eliminate the clipping, then bring the amp volume up to playing level.

[quote name='Skezza' timestamp='1325011195' post='1479109'] the bass is active. [/quote]Make sure you aren't clipping the input. Turn the bass down and the amp up. If the amp has a master volume run that high and the input gain low for maximum headroom.

[quote name='deepbass5' timestamp='1325004186' post='1479041'] Sounds like you are driving the pre or power amp into distortion, which ultimately is going to be bad for the speaker, clipping/square waving the signal. [/quote]Point of fact, clipping has no effect on a woofer. It can result in over-powering a tweeter.

Both an amp and a speaker will fart out when its output capacity is exceeded. In most cases the speaker is the weaker link, but in yours it seems it's the amp.

[quote name='deanbean502' timestamp='1324908653' post='1478384'] Yep 30 watts! [/quote]Fine for the bedroom or studio, but not for gigging.

[quote name='alanbass1' timestamp='1324757114' post='1477691'] should I take the RMS as the safe load for my Bergs (should I get excited and turn them all the way up ). [/quote]99% of speaker thermal ratings are worthless as the drivers will run out of excursion at no more than half that amount of power anyway. That includes Bergs. If it distorts turn it down.

[quote name='ShergoldSnickers' timestamp='1324750113' post='1477627'] Yes, I found conflicting views on that and was wondering if we were back in that strange parallel world where 'larger drivers sound slow' etc. Fast transient response means a cliff-like rise in amplitude, something that can only be accomplished with a small and light driver - a mid or treble driver. Yes, it makes sense. [/quote]A number of factors influence transient response. Best results tend to come with low Mms high Qts low Le drivers, which tends to be common with drivers that work best in sealed alignments. Drivers optimized for vented tend to have higher Mms lower Qts and higher Le, so they may not have as good a transient response. But it's the driver that makes the difference, not the box you put it in. And if you want the lowest possible Mms along with the lowest possible Le you get it with a driver that has a smaller cone and smaller voice coil. In other words, a midrange driver.

[quote name='ShergoldSnickers' timestamp='1324744192' post='1477538'] The transient response of a ported cab is compromised through having to use the port resonance to get the extra output. Apparently. [/quote]That's a common misconception, and isn't true, as transient response is mainly a midrange issue, while porting doesn't affect the mids. Some vented cabs sound good, some don't. The same applies to sealed. One can mess up with either topology. The main reason to use a sealed cab or vented cab is the drivers contained within. Most drivers today are made with specs that work best with vented cabs. Most drivers from 40 years ago were not. Vented cab technology wasn't well understood prior to about 1970, and it took driver manufacturers about ten years after that to get up to speed. [quote]I've always gone with the general rule of ported for SS/Hybrid heads, and sealed cabs for valve heads.[/quote]There's truth to that. The impedance characteristics of vented tends to be more friendly to SS output stages, that of sealed more friendly to tube output transformers.

It's OK to run any amp with any cab so long as there's no impedance mis-match. If the amp is powerful enough to cause the speakers to distort turn it down.

[quote name='Mr. Foxen' timestamp='1324413573' post='1474041'] If DC did break voice coils, most of my cabs would break because I use a 9v battery to check I wired all the speakers in the same polarity. [/quote]+1. A case of another myth that has its roots in reality. If you blow your amp output devices that can result in a direct connection from the supply rails to the speakers, and that can toast them. Not because it's DC, but because the voltage is more than the drivers can handle. In short, overpowering. [quote]If DC alternates then it isn't DC anymore! [/quote]+1. Sources that say a square wave is DC should be universally ignored.

[quote name='4 Strings' timestamp='1324394867' post='1473798'] That's not it at all, Alex. The difference isn't before sounding dirty, the valve amp is incomparably louder. I know what you mean about clean, I only mentioned it as I was not comparing dirty/clipped/overdriven sounds. I'd love to know the reason why. [/quote]Compression, which valve amps do naturally without an outboard device. One can even tell the difference between valve amps that use valve power rectifiers versus SS rectifiers, as there's compression on the DC supply rails with valve. Keep in mind that honestly rated amps, which is most of them, are measured with a specific voltage into a specific load at a specific distortion percentage. When compression occurs THD goes up, so a tube amp honestly rated for 100w at 0.1% THD will have much more power at 10% THD, and the increased power density that results from compression makes the amp subjectively sound much louder still. With sufficient processing an SS amp can do exactly the same. Tubes just don't need the added processing. In the case of the TC they rate their amps with processing factored in, therefore at a very high THD. It's equivalent to measuring a car's gas mileage while traveling downhill with a tailwind.

[quote name='guildbass' timestamp='1324378032' post='1473498'] Now that's what I've SEEN happen out in the world. That's what I've observed happening on a scope,[/quote]What you see on a scope bears no resemblance to an actual musical waveform. In the real world what clipping does is to increase the power density in the harmonics. This greatly increases the voltage swing seen by tweeters, which can toast them. It does not significantly increase the voltage swing seen by a woofer.

[quote name='guildbass' timestamp='1324338355' post='1473296'] What kills cabs...or rather drivers, is Dc voltage, and the more an amp clips, the flatter the signal peaks get. Clip it enough and those flat plateaus add up to a solid elevated DC voltage...And that will brew up the driver coils. A 10 Watt HiFi amp can happily kill a 500 watt speaker if it's clipped hard into it for long enough. [/quote]No. Total myth, I'm afraid, one which is summarily dismissed every time it's unfortunately regurgitated.

Pushing air isn't about the number of drivers, it's about their displacement. Keep the car, get a high displacement Barefaced.

[quote name='chris_b' timestamp='1324254709' post='1472369'] [size=4][color=#222222][font=Arial]"Watts" are [i]not[/i] a scientific measurement. Only RMS watts is, and I don't recall TC claiming RMS. [/font][/color][/size] [size=4][color=#222222][font=Arial]Why do people keep banging on about full pints, half pints, being short changed? TC is selling an amp that in volume equate to a 450 watt amp. That’s the number that is important here, not the number before it was processed and boosted, that's the number you use when comparing its loudness to other amps, that's the number you use when you are buying cabs for it. That’s it!!! [/font][/color][/size] [size=4][color=#222222][font=Arial]You can like the sound and you can hate the sound, that's ok, but all this "I've been sold a 236 watt amp and I've been cheated" bleating is getting tiresome. [/font][/color][/size] [/quote]Bernie Madoff could have used you on his defense team. The only difference is scale, not intent.

[quote name='xgsjx' timestamp='1321047235' post='1434978'] Regardless of wattage, the RH450 is still a very good amp. [/quote]No argument there. I've not found anyone who says that it isn't. But when one goes into a pub and pays for a pint one expects to get a pint, not ten ounces, no matter how good it tastes.

[quote name='klaw123' timestamp='1324165095' post='1471506'] he cab would be awsome at 800watts but is is the best thing to do? [/quote]Driver power ratings are their least significant aspect. What matters are T/S specs ( [url="http://www.eminence.com/support/understanding-loudspeaker-data/"]http://www.eminence....udspeaker-data/[/url]) and frequency response. Driver swapping/replacement is dicey if you don't understand these factors and how to apply them. If you want to preserve your current performance re-coning your blown drivers is the best route. Dropping in new drivers based only on their size and power ratings is a risky proposition.