alexclaber

I'll just add that the Super Twelve T isn't really comparable to those other cabs, it can play much much louder - you need a pair of anyone of those cabs to compete. A Midget T will have similar or greater max SPL to the others when paired with the 900.

[quote name='bremen' timestamp='1350462921' post='1839075']I modelled a 2by10 using Eminence Beta 10A in WinISD and however big or small I made the cab, however I tuned it, the power handling dropped to 20-40W between resonance and 100Hz. Should I have doubled their stated Xmax figure, or are they really this crap? Or is WinISD very pessimistic?[/quote] You may have had the cab tuned a bit low but the power handling at low frequencies is pretty rubbish for a lot of bass cabs. It isn't quite as disastrous as it seems because you don't hit a brick wall at that limit and the power vs loudness relationship is logarithmic. I've been putting together some sample specs so people can compare generic cabs to Barefaced ones and this is what a ported 4x10" with Beta 10s is looking like: [color=#000000]Sensitivity (@ 1m 1W half-space) = 101dB[/color] [color=#000000]Max SPL (@ 1m half-space)[/color] = 124dB [color=#000000]Core bandwidth[/color] = 50Hz - 4.5kHz [color=#000000]Extended bandwidth[/color] = 37Hz - 6kHz [color=#000000]Volume displacement[/color] = 408cc [color=#000000]Recommended amplifier power (W)[/color] = 50 - 300W [color=#000000]Nominal impedance (ohms)[/color] = 4 or 8 ohms [color=#000000]Size (cm)[/color] = 64 x 58 x 47 You can knock 3dB off the sensitivity and 6dB off the max SPL for a 2x10" (and halve the Vd, size and max recommended power). Explanation of specs here: [url="http://barefacedbass.com/technical-information/how-to-interpret-our-specs.htm"]http://barefacedbass...t-our-specs.htm[/url]

[quote name='Wiggybass' timestamp='1350414395' post='1838582']I think you're on the right track but I think it's 99% to do with reflections from the floor, i.e. the effect of 'ground coupling' with LF sources and the long wavelengths they produce. There would be too much amplitude offset between direct and reflected signals coming off the walls and ceiling (especially in a room fitted with absorptive materials like carpets and curtains) for phase cancellation or summation to be an audible issue.[/quote] With the long wavelengths at low frequencies being very resistant to damping from furniture etc the boundary reflections are plenty high enough in amplitude to cause what I've described. I haven't just plucked this theory out of thin air, it's a well known phenomenon, especially on the cutting edge of home audio.

Yes, you can make cardioid arrays with passive cabs but as you say, you need DSP and separate amps for each part of the array. And the less accurate the cab, the further the performance will diverge from the theoretical ideal - and crank up the volume on a load of passive cabs (without DSP which compensates for voicecoil heating) and things will really diverge! But that's not massively relevant to bass cabs - the important bit is the interaction of direct and reflected waves, which you didn't say anything about because you said you didn't know why your low B could sound quiet by your rig and knock drinks over at distance tables. That is why!

[quote name='Wiggybass' timestamp='1350406116' post='1838405']For ages I assumed that one had to be standing at least one whole wavelength away from a LF source to receive it 'in full' as it were, but apparently this is not the case. The fact is though that, certainly as regards very low frequencies (like the open B on a five-string, about 30Hz), the level standing next to my backline can be quite modest whilst knocking people's drinks over at tables twenty feet away, and I don't know why.[/quote] This is due to direct and reflected sounds interacting. When the direct and reflected sound are approximately in phase you get a peak at that frequency and location, when they're approximately out of phase you get a dip. It's very obvious when messing around with bass cabs in our business unit as most of the boundaries are thick concrete so you get very clear reflections - run a frequency sweep and at certain spots and frequencies it can be completely silent, take a step or two to one side and full loudness is back. [quote name='Wiggybass' timestamp='1350406116' post='1838405']LF dispersion is a complex topic. Controlling it usefully has been perhaps the single greatest advance in PA in the last decade, but doing it takes quite a bit of DSP power, extensive control over individual enclosures and specific physical arrangements of multiple cabinets to provide 'beam steering' through selective phase cancellation. I've yet to see any bass backline equipment that even claims to provide dispersion control - and I don't think I will either![/quote] LF dispersion control with bass backline isn't something I see ever happening. To get effective dispersion control you need the speakers to be incredibly accurate, so low distortion in every way possible (frequency, time, harmonics, intermodulation etc). Something like this: [url="http://www.meyersound.com/products/1100-LFC/"]http://www.meyersoun...ducts/1100-LFC/[/url] And they need to be active and you need outboard DSP to control how the speakers within the array interact. Without a carefully positioned and programmed array of low frequency speakers you can't get LF dispersion control. Better to get the increase the midrange and treble dispersion as much as possible so that the direct and reflected sounds are more similar.

I don't know how that cab's tuned but if it's tuned oddly then it it could be the woofers hitting the backplate. Normally low G is quite close to the tuning frequency of a bass cab which makes it easier on the woofers, in which case it could be the amp clipping as it struggles to deliver enough current. But it does sound more like an imminent speaker death problem, so my guess is the cab is tuned too high and your bass and amp are putting out a lot of bottom on the low G fundamental and upsetting the speakers. As Bill says, regarding low being nearly on full, don't! It's fine cranking the lows at low SPL when your ears are insensitive to low frequencies, but once you're up at gigging volume you need to back off that bass boost. If you want your bass to sound more bassy, change what you're doing with your right hand and/or turn up whilst turning the treble down.

Third fret E-string G?

It could be that you're managing to bottom out the speakers (so the voicecoil smacks into the magnet backplate) due to pushing too much power into them in the low frequencies. Turn down your lows and see if the problem goes away. If you bottom out the speakers too hard you'll damage the voicecoil former, which will make the drivers distort due to internal parts rubbing, and eventually fail. Does it happen on any particular notes or as you go lower down the neck? Does it happen with particular playing techniques?

[quote name='thumperbob 2002' timestamp='1350403086' post='1838343']Bass is the bottom therefore cabs should be where nature intended- on the floor [/quote] I've yet to see a double bassist, tuba player or pipe organist performing lying down! Any why do marching bands not wheel the bass drum along the ground? There are two things to consider with the big vs small cab thing: Are you standing so close that you're in the nearfield? And how far off-axis from speakers that produce your critical midrange are you? A tall stack can get full boundary reinforcement from the floor whilst also having speakers reasonably close to on-axis whilst you're standing in the nearfield. If you accept that the rest of your band and the audience aren't in the nearfield, and therefore you'd have a better perception of your sound if you too stood in the farfield, and you can get far enough from a smaller rig to be reasonably close to on-axis (the better off-axis the rig is, the further from on-axis this can be) then a smaller rig which can really move air can feel just as epic as a big rig.

It's all about the cubic inches! Volume displacement, i.e. cone area x cone excursion. With that much cone area you don't need much cone excursion at all!

[quote name='countjodius' timestamp='1350309576' post='1837084']...I figured it's only and extra £100 for a lot more head room![/quote] Sensible thinking!

Look it at like with cars. An efficient car might do 60mpg, an inefficient car might to 20mpg. Put 10 gallons into one and you'll be able to go 600 miles but only 200 miles with the other. mpg=sensitivity; fuel put in=power from amp; fuel tank capacity=max power handling.

The first step to understanding cab loudness is to throw away the lies about cab power ratings - most of them are useless. It doesn't help that there are manufacturers still talking about cab X have 500W power output. It's utter BS. 500W acoustic power output is more than the Pyramid Stage PA rig at Glastonbury, which is the size of a few large trucks and worth more than a large house. Read this: http://barefacedbass.com/uploads/BGM59%20Oct2010.pdf Although other manufacturers quote sensitivity ratings, most are lies - Ampeg and Acmes are accurate. Epifani claim 100dB for a 1x12" containing a woofer with 95dB sensitivity - to get that sensitivity you'd need three of those cabs! It's all rather frustrating, marketing trumping honesty...

It's fine Andy, I realise all this stuff is very complicated - I didn't understand it when I started playing bass! Am going to write some better articles about decibels and hertz etc and put them on the site.

Andy, you don't hear electrical watts. Over 90% of the wattage you put into a cab comes out as heat. Less than 10% comes out as sound. According to Hoffman's Iron Law, the bigger a cab and/or the less deep it goes, the better it will be at turning electricity into sound and the less waste heat it'll generate. Big Baby sensitivity = 94dB therefore efficiency = 1.6% Compact sensitivity = 98dB therefore efficiency = 4% Dubster sensitivity = 101dB therefore efficiency = 8% So 300W electrically into a Big Baby gives you 4.8W acoustic output (300 x 0.016) and 295.2W of waste heat. To get 4.8W acoustic output from a Compact you need to put in 120W electrically, whilst to get 4.8W acoustic output from a Dubster you need to put in 60W electrically. The Headlite is about 250W into 8 ohms so right at the bottom of the power we recommend for the Big Baby. Furthermore, it's not an amp I have any experience of but I have found that in general micro-amps do not produce as much power in the real world with bass guitar as their specs claim, compared to heavyweight amps. Some micro-amps do better, and they're the ones we tend to recommend more often. As I said in my email, I think you'd be fine in your band with a DB750 driving a Big Baby but I'd be amazed if the Headlite has enough power to play loud enough without obvious clipping.

(Although there have been horn-loaded bass cabs, none of them exhibit loading down to low frequencies where volume displacement matters, so they're no better than sealed cabs down there...)

[quote name='stevie' timestamp='1349440678' post='1826352']The Marshall 4x12s from the late sixties didn't produce any true bottom. [/quote] But like all sealed cabs, they can given appropriate EQ! xgsjx, that's a 1W sensitivity plot - it's telling how how much air is being moved per watt but it isn't telling how anything about how many watts the cabs can handle cleanly and thus the max LF SPL available. With horn-loaded subs the volume displacement is effectively increased by the increased air pressure at the cone anyway - very different to bass cabs.

[quote name='Wiggybass' timestamp='1349438090' post='1826283']That's an interesting thought. Is there a linear correlation between increased excursion and equivalent increase in effective radiating area? My first thought would be that greater excursion would just push the same amount of air harder, not that it would move [i]more[/i] air, but I'm willing to learn![/quote] http://barefacedbass.com/technical-information/Volume-displacement.htm If you have a 2x12" cab and a 4x12" cab, both appropriately ported and both tuned to the same frequency, and the 2x12" has woofers with twice the Xmax of those woofers in the 4x12", then they'll both be able to produce the same amount of bottom (low frequency SPL). I don't know the numbers on the typical Marshall 4x12"s from the late '60s but I'd bet that our Big Baby 1x12" can produce as much true bottom, thanks to having easily three times the excursion and a ported rather than sealed cab. As long as the difference in radiating area isn't enormous (like a single 8" vs an 8x10" - because you'd run into issues with acoustic coupling) then cabs with equal volume displacement (cone area x cone excursion) will have equal ability to produce low frequency sound.

[quote name='Mr. Foxen' timestamp='1349436871' post='1826257']Also missed that impedance varies with frequency as well as phase, and fairly sure that can make fun with mismatched cabs too, picturing a ported cab with the big impedance peak at a frequency where the paired cab is not sensitive, resulting in more power going to the less sensitive cab at that frequency.[/quote] This doesn't matter when cabs are connected in parallel. Cone area alone doesn't tell you how much air a rig can move - you need to also consider cone excursion (and port area if that's a potential limitation).

Yes, re-reading your post Wiggy, you seem to have polarity and phase confused! Phase is continuously variable and all loudspeakers have varying phase response across their bandwidth because they are reactive electrical components (i.e. volts and amps do not move in simple synchrony).

More later but there's more to out of phase than being 180 degrees out of phase (equivalent to reverse polarity). Any amount of phase difference will affect summing!

In the vast majority of cases, two 4x10"s or two 1x15"s will work better than a 4x10"+1x15" stack. Bear in mind that when you go to big live shows the bass rig is almost incidental - there are big monitors, especially side fills, and a big front of house PA system. With all that acoustic output the 1x15" on the bottom of the stack is usually doing little more than acting as a stand to get the 4x10" up to a more audible height for the bassist. By all means use a 4x10"+1x15" stack if that's what you own. If you own a 4x10" and want to add another cab, get an identical 4x10". If you own a 1x15" and want to add another cab, get an identical 1x15". If you don't like the tone of your cab, adding another different cab to change the tone of your rig is not a great solution.

The point I'm always trying to get across when discussing pairing mismatched cabs is related to their differing phase response. The best way to understand of this is to think about the pickups on a Jazz bass. Think of the neck pickup as being a cab with a more bassy sound and the bridge pickup as being another cab with a more trebly sound. The common assumption is that if you pair a bassy cab with a trebly cab you'll end up with a stack that does bass and treble well, whilst getting the mids from both - "best of both worlds". But what actually happens when you both pickups on full on a Jazz bass (or any other bass with two pickups in parallel)? You don't get the bottom of the neck pickup plus the top of the bridge pickup and the mids being a mix of both. You get the bottom of the neck pickup, the top of the bridge pickup but much less midrange than from either pickup! Why is that happening? It's happening because there are phase differences between the two pickup's output and so instead of all the output summing fully, some of the output sums partially, some of the output cancels partially and some of the output cancels fully. This is a good thing with bass pickups because it gives us a very different third tonal option on a two pickup passive bass. The same thing happens when stacking dissimilar cabs. Now on the one hand this isn't a problem if the end result is loud enough and sounds right. But on the other hand, the reason someone tends to buy a second cab is because they want to add something in terms of both tone and output to the tone of their existing cab and as the pickup situation illustrates, you won't get that tidy summing - you'll get partial cancellation so the resulting tone will be unpredictable and equally importantly the rig will be less efficient. There's also the matter of mismatched power handling and the cabs' response diverging further at high SPL when things become less linear, so the rig may perform worse and worse as you turn up - exactly when you don't want it to become less efficient! We designed the Compact and Midget to work together - the two drivers have identical motors and the cab alignments are such that the phase response is very close through the lower frequencies (where it matters - at higher frequencies the path length messes with the phase response whether you have identical cabs or not).

[quote name='billyapple' timestamp='1349274280' post='1824101']I can't believe how cool my P looks in this pic what with it being all black and white and that. I built this don't you know? Well done me! [/quote] Tones down the turmeric headstock!

Wiggy, that's why we only do front-ported speakers, means you can push them right back against the rear wall without a thought, plus you feel the slam of air movement when you're standing very close, which is nice. Yes, the player interacts with their rig, which is very different to PA usage - and arguably another reason why dispersion matters a lot with backline (even though we're one of the few companies to be focusing on its importance). If you change your playing/EQ to get your tone where you're standing, you want that tone to be heard everywhere else. That change that's happened in the PA world, realising that dispersion matters is one we're trying to pioneer in the MI world (guitar too shortly!) Our lengthy specs are here: http://barefacedbass.com/uploads/barefaced-cab-specs-jan2011.jpg The unEQ'd -3dB points for the cabs I was referring to are 71Hz (1x12"), 63Hz (1x15") and 44Hz (1x12"). Obviously you can change the response with EQ but that's the starting point.