Bill Fitzmaurice

[quote name='Fubar' timestamp='1340993260' post='1712661'] This has the effect of making the cab 'think' it's bigger than it really is. [/quote]Myth, though a very widespread one. Sufficient stuffing will lower the Q of a cab, which can tame boom, which is [i]similar [/i]to the effect of a larger cab. But it's not the same, as a larger cab also gives lower response with higher sensitivity. And you only stuff a sealed cab, never a vented cab. Stuffing a vented cab will upset the box tuning.

[quote name='PlungerModerno' timestamp='1340882658' post='1710938'] Seems legit. If I was marketing a new cab, esp. a sealed cab... and wanted to show it could produce lots more lows at less watts than most sealed cabs... I'd give a chart because that'd be the hardest thing to argue against. [/quote]You'd think, but what would you compare it against? The major problem is that the response of most bass cabs drops off around 80Hz. That's normal. The expectation of users is that they should be flat to 40Hz or lower. No manufacturer wants their response charts to reveal that their cabs don't meet that expectation, so they don't make charts available. Most manufacturers also quote sensitivity measured in the vicinity of 1kHz, where it doesn't matter, instead of 100Hz, where it does. SPL charts would reveal the truth, a truth that they don't want revealed. What is the truth? Have a look: http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2357 http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2362 http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2374

[quote name='Lord Sausage' timestamp='1340822579' post='1710188'] So what region should you be looking for in SPL charts [/quote]First you have to find them; AFAIK no one reveals them. The official reasons why are 'we don't want to confuse players with information they might not understand (calling you stupid they are) and 'people buy our cabs based on how they sound, not how they chart'. But they don't explain how people are supposed to know how they sound before they buy them if they can't try them first. The real reason for there being no charts is either they don't want you to see them, or they don't have any. Or both.

Read this, and all the other bits on the site. It will answer not only most of the questions you already have but also quite a few that you haven't thought of yet. http://barefacedbass.com/technical-information.htm

[quote name='icastle' timestamp='1340729535' post='1708781'] Stop apologising The 500W will be split between the two cabs, so a pair of 300W cabs will get 250W each. [/quote]And since most 300w cabs can only make use of perhaps 150w each you'll still have plenty of amp headroom.

[quote name='Musicman20' timestamp='1340660211' post='1707846'] I think ALL engineers, no matter how difficult they find it, should find time to get the aesthetics right. Heck, they are probably missing a huge chunk of the market. [/quote]Gettting it right? Or getting it familiar? Just because bass cabs have looked pretty much the same since 1960 doesn't mean that's how they s[i]hould[/i] look, at least not if their main purpose is to be listened to. Not that they need be ugly, like these close relatives of Daleks: Those who can afford the hundred thousand quid a pair go for must not be bothered by their look any more than the likely Picasso on a nearby wall.

[quote name='Dave Tipping' timestamp='1340575348' post='1706584'] before if you knocked on the cab it sounded pretty hollow..Now it sounds solid with a high pitched knock. [/quote]The tecnical name for that is 'the knuckle test'. Using it on any cab you're considering is a good idea, as is using it on any you already own.

[quote name='Dave Tipping' timestamp='1340570369' post='1706461'] Cheers for the compliments lads, had a good play with it today and it's pretty incredible the improvement. [/quote]Good show, and it goes to this quote from your original thread: [quote]if your Laney hasn't got bracing then it probably doesn't need it and the same is probably true for the dampening material.[/quote] Ths fact of the matter is that speaker manufacturers are in the business of making profits, not making the best product possible and then selling it for peanuts. That often means cutting corners, and those corners most often cut are those that the buyer isn't aware of unless he opens the box up to see what he paid for, and in some cases didn't get. The good news is that putting in what the manufacturer left out isn't a bit difficult, and can as in this case have dramatic results for very little effort and cash.

[quote name='Mr. Foxen' timestamp='1339788888' post='1694523'] Get a bunch of distortion and compression if you put more in, so might be a win if you like that. Until they break. [/quote]True, and break they will. Guitar drivers are far more tolerant, as with their short xmax they distort around 10% of their power rating, leaving a lot more room between when they start to get nasty and give up the ghost.

[quote name='51m0n' timestamp='1339760667' post='1693844'] +1 excellent response Similar to the 500w of the TC Electronic amps is actually 300 (200??) and something watts with a load of DSP processing to make it seem louder. Tubes just do that processing for you in an analogue way. [/quote]+1, and by that same token you may use processing to get that same result with any SS amp. [quote] Bunch of that would be down to the 2x10 not actually being able to convert much more than 100w into spl. [/quote]+1. Few 210s can actually make use of even 150w, so anything more than that put in won't get any additional out.

The rear ported are that way because there's not enough room to fit them on the front. Larger box equals lower response with the same drivers used.

[quote name='Mr. Foxen' timestamp='1338897483' post='1680708'] That says a short causes no harm at all, which is as I said, low impedance is not an issue for damage concerns. [/quote]+1. Most tube amps use a closed circuit switching output jack that shorts the output if there's no speaker plugged in. That's to prevent damage from what really does bother tubes, which is no load. They're not happy with a load higher than the tap rating either, but a load lower than the tap rating is to a tube as water is to a duck.

[quote name='Lord Sausage' timestamp='1338829278' post='1679763'] So what do 1x15 give you then is it more low frequencies or is that bollocks! [/quote]Bollocks. Cone size in and of itself only affects one function, the angle of dispersion, The larger the driver the narrower the angle. All other aspects are determined by the driver specs. Same specs, same results, no matter what the cone size.

[quote name='Lord Sausage' timestamp='1338828441' post='1679756'] Also what about ohms? If you have say an amp that's 500w at 4ohms and 350w at 8 ohms and you run it thru a 4x12 that handles 500w at 8 ohms, i take it you'll get 350. If you add say a 1x15 cab that is 8 ohm would you still get 350 or do the ohms increase or decrease. Would i have to buy 4ohm cabs. [/quote]The watts just don't matter, you have to increase them by a factor of ten to sound twice as loud. Always buy 8 ohm cabs so that if you need to add a second you can. And the last thing you'd add to a 412 is a 115, a 115 can't even keep up with a 212.

[quote name='Lord Sausage' timestamp='1338802455' post='1679298'] Does it matter if the amp is more powerful than the speakers. [/quote]Only if it has no volume control.

[quote name='CraigPlaysBass' timestamp='1338409734' post='1674271'] Could someone please explain to me clearly what the difference is between DC and the clipped waveform? [/quote]DC is constant polarity and has no phase. AC has phase, and with each passage of 180 degrees of phase polarity is reversed.

[quote name='GregBass' timestamp='1338402599' post='1674085'] Good question. I posted what I felt was reasionable advice, but a couple of "experts" decided to rip into what I said. I responded. Things got silly. [/quote]Well, if you're going to give expert advise the first requirement is that you be an expert. My credentials as such are a matter of public record. I also have a personal rule that I'm here to teach those wishing to learn, not argue with those who don't. As you clearly have no desire to learn, only a penchant to argue that which you don't comprehend, with you I am done.

[quote name='GregBass' timestamp='1338387450' post='1673703'] And isn't a flat voltage waveform actually a direct voltage? [/quote]No. [quote] Go run a fast Fourier transform on your 'square' wave and see what harmonics you get [/quote]+1. Or run it through a low pass filter to remove the harmonics. What will remain is a sine wave. A woofer voice coil is a low pass filter. One of the design characteristics of guitar drivers is low Le, so that the harmonics aren't filtered at too low a corner frequency. .

[quote name='GregBass' timestamp='1338384355' post='1673631'] Clipping is EXACTLY putting DC in short bursts across the speaker. [/quote]It does not. DC does not alternate between positive and negative. [quote]Think of the theory. Consider a sine wave. When it clips the top of the waveform goes flat - that's basic waveform analysis. [/quote] That's flawed waveform analysis. The difference between a sine wave and square wave is the harmonic content. A sine wave has none, a square wave has all the harmionics of the fundamental occuring at the same voltage swing as the fundamental. [quote] the Fane technical department describe it as precisely that when they explain that over pushing the amp is more likely to damage speakers than driving them too hard.[/quote] If that's the case they're incorrect as well. I doubt Celestion would make such a grievious error, knowing that the tone of a guitar is pretty much predicated on clipping not only the amp but the driver as well. This document is the source of the myth of underpowering. If readers all paid attention to the key phrase 'high frequency components' the myth might not have arisen. But like all myths it grew with each retelling. [url="http://www.jblpro.com/pub/technote/lowpower.pdf"]http://www.jblpro.co...te/lowpower.pdf[/url] And as to why cliiping has no effect whatsoever on woofers, not only does the added harmonic content of a clipped signal not increase the maximum voltage swing, the majority of the added harmonic content is filtered out by the inductlve and capacitive reactance of the voice coil.

[quote name='GregBass' timestamp='1338383506' post='1673611'] I read your statement as meaning that under normal usage the output voltage of an amplifier is constant. [/quote]You misunderstood.

[quote name='dincz' timestamp='1338353498' post='1673105'] We're talking at cross purposes here. You're talking about an amp's behaviour under normal operating conditions. I'm talking about maximum available output voltage swing i.e. at clipping. [/quote]Since most players tend to use their amps under normal conditions that's what's pertinent. [quote name='JTUK' timestamp='1338371447' post='1673334'] But to follow that on logically, you have to put their opnions and thoughts below the producers who sell volumes of the stuff. [/quote] I can't speak for Alex, but I've designed dozens of speakers for said producers, the majority of whom do not employ engineers, and are not engineers themselves, relying on independants such as myself to do their design work. [quote name='GregBass' timestamp='1338376958' post='1673451'] Ah - I took the quote at face value (that the voltage must be constant). That was what I disagreed with. The output voltage of an amplifier is absolutely no constant. [/quote]It must be a constant, otherwise the amp simply won't work. Hook up an tone generator to an amp with flat response, the amp to a speaker. Measure the voltage as you sweep across the spectrum, it will remain constant even though the speaker impedance is not. If it's not constant the amp, or generator, does not have flat response, and you'll see the same voltage fluctuation into a resistive load.

[quote name='dincz' timestamp='1338322148' post='1672821'] Connect an 8ohm load, measure the maximum output voltage swing and then repeat with a 4ohm load. It'll be different on every single amplifier. Not even debatable, just a demonstrable as well as theoretical fact. [/quote]Explain then why a speaker doesn't reproduce every note at a different level, when this is what a typical speaker's low frequency impedance looks like:

[quote name='dincz' timestamp='1338311001' post='1672561'] On this I have to say that's absolutely untrue. Every amp I've ever bench-tested could deliver a higher voltage swing into an open circuit than with a load connected. The power rail voltage and maximum available output voltage swing reduce as you drop the load impedance. No surprises there, just Ohm's Law and real-world imperfect power supplies. [/quote]An open circuit doesn't deliver a load. Within the operating load ranges actually presented by speakers amps must deliver a constant voltage, otherwise they simply won't work.

[quote name='dincz' timestamp='1338307063' post='1672485'][b][i](to a specified load)[/i][/b] [/quote]Amps deliver the same voltage swing irrespective of load impedance. They have to, otherwise every note would be heard at a different volume, as impedance is not the slightest bit a constant. Current varies with load.

[quote name='dincz' timestamp='1338283581' post='1671971'] There seem to be only two points of view around here: 1. Power is everything 2. Power is meaningless [/quote]Point one comes from those who do not understand how gear works. Point two comes from those who do. What really matters is voltage swing. It takes a given voltage swing to drive a speaker to full output; if the amp can deliver that voltage swing you'll get full output. If it can't you won't. Voltage swing removes power factor and duty cycle from the equation, and all of the spec fudging that they allow. Amplifier and transducer engineers are well aware of this fact, so voltage swing is what they consider when designing your gear. Marketing departments and the vast majority of consumers don't.