Bill Fitzmaurice

A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't.

2 hours ago, Beedster said:

 

There's no better evidence against the watts=volume argument than a B-15 👍

Or a Vox AC-30. 😉

You can buy one of Tom Hamilton's B15s for a mere $6k. https://reverb.com/item/68553915-tom-hamilton-s-aerosmith-ampeg-vintage-b-15-flip-top-bass-combo-amp-low-serial-number-early-1960s-6

Maybe it's not the same amp, but we often shared a stage in the 60s where we'd use his B15 and my Bassman. His 30 watt B15 was louder than my 50 watt 2x12 Bassman.

44 minutes ago, Dan Dare said:

 watts are not a very meaningful way to rate amps and some manufacturers' claimed figures can be a little optimistic.

Even when accurate they're not worth much. Is a 500 watt amp ten times louder than a 50 watt amp? Nope. It's twice as loud, assuming they have identical transfer function. That's a long leap as well. Ask anyone with a 50 watt valve amp. 😉

Watts don't matter. If they did one wouldn't be able to gig with an Ampeg B15N. It's the total package that counts. I know that trying before you buy isn't easy, but it's still the best way to find what works for you, well worth investing a day or two.

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Have you ever had a piece of kit fail on you in that time Bill?

Not one, other than cables and very rarely a string. When I was touring I had a spare amp, but never had to use it.

On 06/12/2024 at 03:49, JohnDaBass said:

Yes.

The internal amp sees a 4 ohm load and sends 400w to the internal 2x10 speakers and 400w to the extension cab.

Amps don't send watts, they send volts. How much power is consumed by each driver is the product of said volts and current, current depends on the load impedance. In this case where each internal driver is 16 ohms if you add an 8 ohm cab half the power will be consumed by the extension, the other half is split between the two 16 ohm internal drivers. What the impedance switch on the amp does is an unknown, as there's no real explanation in the manual. It may be some sort of current or voltage limiter but that's pure speculation.

In 50 plus years of gigging the only spare pieces of kit I've ever used were cables and strings.

Thanks, but I made an error. The radiation angle of any source only shrinks to 180 degrees when the radiating plane is a  wavelength in dimension. Since with direct radiating speakers the radiating plane is the baffle it's called the baffle step frequency. When it's smaller than a wavelength the sound will wrap around the cab, eventually going to 360 degrees as you go lower.

Some of us do. 🤥 

Port radiation is omnidirectional, so the orientation doesn't matter. Scientifically speaking the radiation angle of any source only shrinks to 180 degrees when the radiating plane is less than a wavelength in dimension. At 100 Hz a wavelength is 3.43 meters. Yes, that means the cone radiation is omnidirectional at 100 Hz as well. That's why you can hear the lows standing behind a cab.

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. 😲

It's not about increasing the power, it's about reducing the peaks in the response that are heard as distortion. Think of it as a fuzz box in reverse, making the tone sound clean at higher levels than it otherwise would. In the case of the OP it could well be that what seems to be speaker distortion is actually the amp hard clipping.

I don't know about GK but TC uses compression and other DSP tweaks to approximate valve transfer function with their RH amps, with power ratings of what they claim they sound like, as opposed to what they measure, leading to the 'TC Watts' scandal. The RH 750 is actually only 236 watts 'but it sounds like 750'. 🤔

On 20/11/2024 at 07:41, bertbass said:

I don't care what anyone says and they'll aways say a watt is a watt but, valve amps are loud!  Transistor amps are only half as loud as valve amps and class D amps are only half as loud as transistor amps.

Myth. A decibel is a decibel, no matter what the source. The primary reason why valves sound louder is the compression inherent with valves. Duplicate that compression, and all the rest that results in the amp transfer function, and SS amps of any class will sound the same as valves. Said compression and the rest takes place in both the pre-amp and power amp stages, so using the same pre-amp into different power amps will give different results. Valve compression results in easing into clipping, SS without an external compressor doesn't. That can result in very different results even when the power output and decibel levels are identical.

The dip on the maximum SPL chart is where xmax is reached. Since the 320 has considerably longer xmax it also has higher maximum SPL at those frequencies where xmax , rather than thermal power, is the limiting factor. You really don't want that dip in the 60-90 Hz range, as that's where the output demands of electric bass are the highest.

The speaker power rating is the maximum, not the minimum. For that matter the 600 watt rating is thermal. Chances are it may not handle anywhere near that before reaching its mechanical limit. I'd make sure that something's broken before trying to fix it.

On 14/11/2024 at 15:29, Chienmortbb said:

Funny you should say that as I was considering putting a PR320 up for sale. PM me. AS BFM says it has close to twice the XMax and goes lower so you would not need to push so much low end power from the amp.

+1. In the same box tuned to the same frequency the 12 PR 320 has the advantage in low frequency sensitivity (first chart) and maximum SPL (second chart).

The 320 has lower Fs and longer Xmax, better for the low end output.

An octave pedal is what you use if you really really want to blow drivers. 🤥

Agreed. By the same token if you don't like the sound of what you have don't try to improve on it by adding another cab. Start off with something you do like.

Those look like OEM versions of the 12PR300, so it's highly unlikely they were at fault. The PR320 isn't much better, if at all. You'd have to go FH520 for that. I'd have the old ones re-coned.

5 hours ago, Lozz196 said:

So 400 watts, 1x12 in combo gets 200 watts, each 12 in the 2x12 gets 100 watts.

True, but there's a lot more to it than the power to each driver, depending on the frequency response and sensitivity of the 2x12 versus the 1x12. The right way to do it is to get a 1x12 extension that uses the same driver with the same enclosure configuration.

That thump is normal, more or less. Better quality amps don't do that. Pulling the plug would be a bad idea if it's 1/4 inch, as that could short the output when you plug it back in and cause serious damage.

Duplicating high and low frequency shelving and midrange bandpass EQ with graphic isn't exactly intuitive, but if you know how they differ it's not all that difficult. However I'd venture that for the average player Q is just a character on Star Trek Next Generation. ☺️