Bill Fitzmaurice

[quote name='alexclaber' timestamp='1484656628' post='3217193'] Bear in mind that plenty of bass cabs with low excursion (<3mm) drivers are tuned to ~60Hz and used with amps in the 300W+ range - if they were behaving as suggested by these graphs people would be replacing all the drivers after their first loud gig. [/quote]Even if they did there's another consideration. Going beyond xmax doesn't cause damage, reaching xlim/xmech does. The Beta 10 has 3mm xmax, with 8.6mm xlim, so there's a lot of room for overshoot. The BP102 with 6.2mm xmax will go a lot louder than the Beta 10, but with 10mm xlim there's a lot less overshoot capability, so despite the higher output capabilty of the BP102 you're far more likely to see them creased than Beta 10s. A minimum 2:1 xlim to xmax ratio is prudent. If that much is not available then it's wise to not only high pass but to limit the maximum voltage applied to the driver as well. That's seldom seen with electric bass rigs, but in high end PA it's SOP.

[quote name='markstuk' timestamp='1484582603' post='3216481'] I was looking at driver spec sheets (3012ho) and noted that the impedance appears to go into tens of ohms at low frequencies. Does this not limit the amount of power your amp delivers at low frequencies ? [/quote]Speakers are voltage driven devices, not power driven devices. An amp will deliver a constant voltage into any load.

[quote name='Phil Starr' timestamp='1484409190' post='3215285'] I had some of the old Motorola piezos which sounded OK. Bill will know but I think CTS may have taken on the Motorola plant when they stopped production. They weren't widely available over here when I checked quite a few years back. The cheap Chinese made piezo's are definitely inferior both in sound and reliability. I decided in the end that a conventional horn driver and crossover were always going to sound better. [/quote]Motorola piezos were dismissed back when they were the only game in town, to some extent rightfully so, because they were never properly employed. Motorola sold their piezo business to CTS, and they were still disrespected until a few years after CTS went out of business. That changed when NOS Motorola and CTS piezos started to command premium prices, often ten times that of the Chinese versions. Then the same people who had never endorsed piezos changed their tunes, and said that the NOS Motorola and CTS were fine but the Chinese brands were junk. I still have some NOS Motorola and CTS on hand. Some Chinese brands, notably Goldwood, work better. Piezos properly employed work just as good as compression drivers. But to get piezos to work well they must be used at least in pairs, as they lack the voltage capacity to be run singly at high volume. They also must have a real crossover, one that employs a resistor to offer the crossover a resistive load. That resistor can't be 8 ohms to use an off the shelf 8 ohm crossover, as the insertion loss is far too high. There's no off the shelf solution, it must be custom configured. I have yet to see a single commercial manufacturer who properly employs piezos.

There is a right way and a cheap way to load bass cabs with tweeters. Care to venture which method is the most commonly employed?

If it's a piezo you can't use an LPad. Read this: http://www.baysidenet.tv/catalog/pdf/piezo.pdf Note that not all piezos are alike.

Insert an LPad between the crossover and tweeter. Google it.

[quote name='Lw.' timestamp='1484237779' post='3213865'] So - are we damaging our expensive ported cabs or not? [/quote]When's the last time you had to replace a driver due to mechanical damage?

The vented 2512 should be about 2dB more sensitive in the lows than the sealed BP1525, without the hump that causes boom, giving it the advantage unless you have more than 250w on tap. Then the higher Vd of the 1525 gives higher output, though you'd need a way to contend with that boom, such as a parametric EQ. I don't care for the SM212, or for that matter most European offerings, as they lack a rising response into the midrange. That's OK crossed over at less than 2kHz to a midrange driver, but IMO only then.

What does a comparative modeling of the two show you? Yes, the BP1525 will deliver a good low end in a sealed cab...if it's at least 4 cubic feet.

An 8 ohm 110 would keep the same power in all three drivers. If you were going to a 112 or 115 it would probably be better for that to be 4 ohm.

[quote name='AndyRoo' timestamp='1483712605' post='3209463'] [size=4][font=Arial, sans-serif]is this one thirds/two thirds power splitting based on the max head power (i.e. 500W, which would put 160W into the 8ohm and be fine but 333W into the 4ohm cab and ultimately shred it subject to “Alex’s first rule”) [u]OR[/u] is this power splitting based on the power at the overall impedance (i.e. 500 * 2/2.667 = 375W)[/font][/size] [/quote]It's based on the impedance. The problem here is that the 210 will be doing most of the work. Depending on what you're adding it might not be all that worthwhile. A second identical 4 ohm 210 would be the best option.

From 1965 I've only had four amps, and while I've built hundreds of speaker cabs of all types I've only used perhaps eight.

[quote name='gary mac' timestamp='1483204546' post='3205418'] I used a Markbass 12" cab with my Big Baby, I'm sure Alex from Barefaced would be horrified but it honestly sounded, to me, great [/quote]And how did it compare to using two BB? I'm going to assume that you didn't try those two options side by side. The fact of the matter is that unless grossly mismatched any two cabs will sound better together than either does alone. Chances are a matched pair will work better than a mis-matched pair, whatever they are, as one will likely be a weaker link in the chain.

[quote name='Dan Dare' timestamp='1482530204' post='3201361'] Could sustained current delivery be the way to measure "heft"? [/quote]Absolutely.

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.