Bill Fitzmaurice

Guessing is all one can do when they don't know the driver Vd specs. If one does have that spec then one doesn't have to guess, one knows. Manufacturers love to brag on watts, which is so much useless information, while not revealing what actually matters.

[quote name='Kevin Dean' timestamp='1482659246' post='3202103'] If you had two cabs the same speaker configuration & same make & model , but one is a 400w version & the other a 1000w version [/quote]If that's the case they're not the same, so they probably wouldn't sound the same. [quote] the 400w is a lot cheaper & would easily handle the volume I would be putting through it [/quote]How do you know? Unless you've taken some measurements with gear that you probably don't have there's no way of knowing how much power you put into your old cab. The power rating of a speaker doesn't reveal how loud it will go anyway, and the specs that do tell you that manufacturers never reveal.

Daisy chaining sends the current for both cabs through the cable to the first. It's not a major issue, but technically each having its own lead to the amp is preferred, as is using Speakons.

[quote name='Phil Starr' timestamp='1482480798' post='3200861'] You can blow a speaker using an amp rated at half the speaker rating[b], yes but only if you exceed the excursion limits of the drive unit.[/b] [/quote] An amp rated at 200w at 0.5% THD should be quite capable of delivering 400w at 2% THD, and therefore it would have no problem toasting a 300w rated voice coil. That's why you cannot assume that an amp rated for less than the speakers insures that it can't damage the speakers. [quote]you can use an amp rated for ten times the speaker rating with no issues.[b]. But only if you keep it turned down. [/quote][/b]That fact should be self evident.

Amp power ratings are measured at low THD levels. If an amp will deliver 6dB more than it's rated for at high THD, which isn't uncommon, power output is quadrupled. Speaker power ratings are thermal, how much power they will handle before the voice coil melts. It's not unusual for their mechanical limits to be reached at half the thermal rating, especially with low frequencies. These are just two reasons why watts are possibly the least useful method to match amps and cabs. That said, a reasonable way to match them is to have the amp rating between one-quarter and twice the speaker rating. Our hearing has a built in warning system that tells us when speakers are in danger of being damaged: they sound bad. When that happens turn it down.

[quote name='28mistertee' timestamp='1482431349' post='3200578'] Contradicts earlier advice given earlier on in thread. [/quote]Not mine.

[quote name='28mistertee' timestamp='1482390667' post='3200067'] I'll look at ensuring the wattage of my head doesn't exceed rating of cabs. [/quote]I repeat: [b]You can blow a speaker using an amp rated at half the speaker rating, you can use an amp rated for ten times the speaker rating with no issues.[/b]

The Eminence Deltalite II 2510 is very well balanced.

[quote name='Jack' timestamp='1482319313' post='3199474'] I have a pet theory that older speakers seemed louder because we never expected big bass from them. So maybe they were more efficient in the upper registers at the expense on the boomy bass. [/quote]Maximum driver sensitivity was realized in 1949, with the JBL D130. It was very bass shy, because its low Qts responsible for high sensitivity also chokes off bass response. At the other end of the scale are high Qts drivers, typically found today in cheap combos and entry level separates. They have high sensitivity in the midbass, so they subjectively can sound loud, but they also sound boomy. Most vintage drivers were high Qts.

[quote name='sratas' timestamp='1482059210' post='3197225'] Markbass uses a HPF in its line of amps, a gentle slope if 6 db/octave at a frequency well below 40 hz...the vast majority of manufacturers use HPFs, some don't. I'm not sure, but I guess some old fashioned tube amp may not use it, think about svt, bassman of old, maybe even contemporary [/quote]Strictly speaking virtually all pre-amp cicuits, valve or SS, incorporate high pass filtering. The most common form of a high pass filter is a series capacitor, and every amp configuration that I'm aware uses series capacitors between stages, so it's not like a designer has to add anything to the circuit, by default it's already there. All one has to do to realize a desired high pass knee is to use the correct cap value. As for achieving more than a 6dB slope, which is what you get from a single cap, since there are series caps between each amp stage every one of them can be configured as a high pass, and their slopes are cumulative. Where valves are concerned they add another source of high passing via the output transformers. Fender in particular was well known for cost cutting wherever possible, and they did so with their output transformers. They never could have gotten away with the output transformers they used in the hi-fi world, where 20Hz response was demanded, but they can, did and do get away with them in musical instrument amps.

[quote name='Passinwind' timestamp='1482001187' post='3196930'] The long thread on Talkbass quickly devolved in a very contentious affair. [/quote]Doesn't everything? A goodly percentage of members there suffer from advanced cases of Dunning-Kruger effect. [quote]Its much more practical and efficient to do it in the amp, even if the speaker is able to handle subsonics the fact that the amp is producing them is probably seriously eating into the amps headroom. [/quote]That fact isn't lost on amp designers, so most have low pass filtering in the pre-amp as part of the pre-voicing EQ. Where you're most likely to have an issue is with a separate pre-amp/power amp configuration, and then only if the pre-amp designer didn't high pass for whatever reason.

[quote name='28mistertee' timestamp='1481989881' post='3196820'] So with the above in mind, is head wattage irrelevant as long as it isn't over the cab rating? [/quote]No, it's just plain irrelevant. You can blow a speaker using an amp rated at half the speaker rating, you can use an amp rated for ten times the speaker rating with no issues. There are too many variables involved to say that this amp goes well with that speaker.

Most manufacturers either glue the cloth to stringers or face the stringers with felt to prevent slap.

[quote name='Downdown' timestamp='1481918748' post='3196349'] I doubt I could return a cab under warranty if I'd blown a driver with too much power so why should blowing one by driving with too-low frequencies be any different? [/quote]For you to approach xlim with most drivers they'd sound really bad. It's ignoring the warnings of impending doom that often result in it.

[quote name='alexclaber' timestamp='1481900888' post='3196140'] the worst problems I've had with cone over-excursion were with cabs which were tuned to 31Hz, so you were never driving them with frequencies below the tuning frequencies. [/quote]That's not surprising. With 31Hz tuning excursion in the maximum power band width, from 50 to 70Hz (even with a low B ), will be considerably higher than with the usual 45-50Hz tuning. 31Hz is appropriate tuning for a PA sub, but not for an electric bass cab, not even a 6 string with a low F#. That's perfectly obvious to anyone who's ever seen a spectral analysis of the output of the electric bass, but I'd say that's rare even within the community of acoustical engineers, let alone bass players.

What cloth did you use? A proper grille cloth offers practically no resistance to the flow of either sound or air.

[quote name='Marty Forrer' timestamp='1481855735' post='3195782'] Most speakers will handle a pure signal many times their rating, but not if the signal is dirty. [/quote]Speakers can't tell the difference, and they're unfazed by clipped signals. Were that not the case guitar players would have to change drivers as often as they do strings. Tweeters can be toasted by clipped signals, because the high frequency power density is greater when the signal is clipped. Woofers, never.

On the issue of bridging: http://billfitzmaurice.info/forum/viewtopic.php?f=10&t=19292

[quote name='Phil-osopher10' timestamp='1481812543' post='3195366'] Is the only way to prevent damage a low pass filter of some description? [/quote]Most amps have HP filtering built in. If yours doesn't it will be obvious by excessive thump noise, which is cured with a rumble filter. [url="http://www.gollihurmusic.com/faq/38-HIGH_PASS_FILTERS_GETTING_RID_OF_THE_MUD_AND_RUMBLE.html"]http://www.gollihurm...AND_RUMBLE.html[/url] Ported cabs are no more prone to damage than sealed. If anything you're more likely to over-power a sealed cab, as they have less sensitivity in the lows than ported. Ported cabs also have minimum driver excursion at Fb, where the port is doing all the work. Finally, xmax is not where voice coil damage occurs. That would be xlim. [quote]I don't hear much about speaker failures these days, not at the rate they failed in the 60's and 70'[/quote]+1. If this was an issue reports of blown drivers would be rampant.

The rule of thumb in the US is that you're expected to provide PA. I doubt that one venue in fifty has a house system. When I was touring I played in better than average rooms, made a reasonable living, and as best I can recall over a three year period playing in perhaps a hundred different rooms a total of two had PA.

Wattage ratings mean next to nothing. Cab power ratings don't consider driver excursion, which is the primary limiting factor in output. An amp can't be too large, assuming that the volume control is functional, along with the brain of the user. And since sound levels are logarithmic, meaning it takes ten times the power to sound twice as loud, the audible difference between most amps is modest in any event. Other factors, especially speaker response and sensitivity, are far more significant than watts. And no, you can't under power a speaker.

I'd use something more than 1/8 inch thick. I imagine you have these on your side of the pond: https://www.walmart.com/ip/Ozark-Trial-Camping-Pad-Blue/16783660 Ask any Boy Scout.

[quote name='stingrayPete1977' timestamp='1481724564' post='3194568'] If it's small/medium functions I presume there will be a foh to go with the amp [/quote]One thing I learned long ago is that you can never assume that PA will be adequate, if there's any at all.

[quote name='LITTLEWING' timestamp='1481465832' post='3192450'] I know I'm going to sound old fashioned, but unless your entire set consists of every slap and pop tune in the world, there is no bleedin' point putting an HF horn of any description in a bass, yes BASS, cabinet. It's meant to reproduce low notes and low notes only. [/quote]Every low note consists of a fundamental plus harmonics that extend all the way up to at least 8kHz. There's nothing wrong with tweeters, the issue is that there's a big gap between where woofers, especially fifteens, drop off and tweeters kick in, on average at least an octave. Why? Because using tweeters that go no lower than 3.5kHz, if that, is the least expensive method of augmenting a woofer. The right way to do it is to either use a true midrange driver, or to use tweeters that can go to 2.5kHz or lower. But that jacks up the price.

[quote name='stingrayPete1977' timestamp='1481285650' post='3191198'] Plenty of good sounding bands out there where those pa tops will be what the audience hears. [/quote]If they're all the audience hears the lows will be weak. They're small, so they won't have much in the lows best case, and up on a pole where they need to be as PA mains is the worst case for lows, as they won't get boundary reinforcement from the floor. Used with subs handling the lows as they should be they'd be fine, but that scenario isn't what the OP is dealing with.