Bill Fitzmaurice

[quote name='Marvin' timestamp='1324056989' post='1470457'] I sort of understand what 'beaming' is. This is a question out of sheer curiosity, how does speaker configuration affect beaming? Or what affect does speaker configuration have on beaming? [/quote]The angle of dispersion is inversely proportional to the size of the source. That's the #1 reason why midranges are smaller than woofers, and tweeters smaller still. Guitars have most of their frequency content above 1kHz, where the dispersion of a twelve is rapidly collapsing. Worse, when two twelves are placed side by side their dispersion on the horizontal plane falls to that of a twenty-four inch driver.The simple solution is to use eights and tens, not twelves, and stack them vertically, for maximum dispersion on the horizontal plane. But, while most guitarists are acutely aware that their cabs beam, as with the weather they complain about it but no one really does anything about it.

[quote name='4 Strings' timestamp='1324024201' post='1469792'] I have the opposite problem, as bass has more omni-directional frequencies (Bill?)[/quote]Bass cabs are omni-directional to about 250Hz, and don't beam much below 1kHz, so they're generally not hard to hear on stage unless cancellation modes mask their output.[quote] I never get much of the guitarist from the other side of the drummer nor the keys next to me but with his speaker the opposite side of him.[/quote]That's because most of their bandwidth is in the directional frequencies, and if their cabs have drivers placed side by side they're beaming through most of their range. The only solution is to have them in the monitors.

[quote name='ficelles' timestamp='1323991498' post='1469705'] . is an 8 x 10 a point source or a line source? [/quote]It's both, as are all speakers, depending on frequency and how far away the listening position is. Practically speaking all electric bass cabs should be considered point sources, save maybe a pair of 810s stacked vertically.

Tilting the cab back works too.

These symptoms can usually be traced to the venue, being caused by room boundary interactions, and changing the speakers would have no effect. All speakers lose volume with respect to distance via the same equation.

[quote name='Ghost_Bass' timestamp='1323798742' post='1467258'] Humm... i doubt the driver was changed... the previous owner was a BC member so he must definetly be an honest person! I'd rather believe that the driver used has somehow the same roots as the 3012 or that it could have been based on it's development... [/quote]There's also the possibility that whoever wrote the G-B ad copy that states a 7 oz magnet and 2 1/2" coil was wrong. Or that the driver was downgraded to a 2512 frame when the neo price hikes hit.

[quote name='Ghost_Bass' timestamp='1323780524' post='1466883'] Bill, if Jeff is using a 2512 based driver they must be very diferent from the stock ones because the frame and magnet are the same as the 3012HO [/quote]The 2512 and 3012 frames are almost identical visually. You'd be very hard pressed to tell the difference in pictures. The heatsink and rear cup of the 3012 are larger in diameter, to accommodate the eleven oz. magnet and 3 inch coil. Since the G-B driver has a seven oz. magnet and 2 1/2 inch coil it's a 2512 variant. BTW, the 2012 has a 2 inch coil, the 40xx series 4 inch coils, so you should see a pattern in their model numbers. There are OEM 2512s with longer xmax than the standard version, but as is always the case when you change one thing you change everything, and those versions give up midrange extension and sensitivity. A 300w coil is a possibility too, but that means a larger gauge wire, which means higher Mms, which means higher Qes and lower sensitivity. I have one such sample, and sensitivity is 94dB, compared to 96dB for the stock version.

[quote name='jimcroisdale' timestamp='1323713533' post='1466156'] I thought the 5mm+ Xmax was a significant improvement over most OEM drivers? [/quote]The Ampeg ten has 4.7mm. It's true though that many OEMs aren't as good as the Ampeg. [quote]The 2512 has a cast frame, which from what I understand, in general leads to greater stiffness/less resonance compared to typical pressed steel (as seen in the basslite). The frame is also important for wicking heat away from the driver, and cast alu should be better at that so in theory you'd expect the deltalite to show reduced power compression in comparison to the basslite[/quote] The 2512 has a larger coil, which gives it higher power handling, which requires more heatsinking. The Basslite doesn't use a cast frame because with its rated power it doesn't need it. If you believe the Ampeg spin doctors a stamped frame sounds better, but that's one wagon I won't jump on.

[quote name='jimcroisdale' timestamp='1323710054' post='1466108'] As a slight aside, knowing what I now know about xmax and fartout, do you think that manufacturers use the Deltalite 2512 instead of the Basslite 2012 just so that they can quote the higher wattage? [/quote]Probably. Even then G-B is stretching things claiming 300 watts. Not so long ago they were also claiming -3dB to 45 Hz. They were called out on it and now they're claiming -10dB. I'd be inclined to run a 2512 in a 112, I do in mine, just to have some extra thermal capability, but in a 212 I'd save the $ and use 2012s. As far as performance goes the 2012 is the equivalent of the average stamped frame OEM ceramic driver.

[quote name='Ghost_Bass' timestamp='1323692917' post='1465802'] I'm almost certain that Genz Benz uses the 3012 [/quote]G-B uses the 2512 motor: [i]2 1/2" ...voice coil...7 oz Neodymium magnet[/i]

[quote name='Mr. Foxen' timestamp='1323619687' post='1465084'] Not comparable to the Fearful again. [/quote]+1. Not even close. Very few manufacturers are using 3012 based drivers. AFAIK only Barefaced, AudioKinesis and Baer do.

Prices for neo drivers have gone up just as much for manufacturers. It's the reason why Bergantino stopped making their neo cabs.

[quote name='Merton' timestamp='1323017793' post='1458323'] Good point, I guess they (claim they) did the first bass-specific 4x10 but the format no doubt predates them. [/quote]Fender was doing the 4x10 Bassman combo in the mid 50s. Using guitar drivers, of course, as bass drivers did not yet exist. For that matter neither did guitar drivers, they were all classified as musical instrument.

[quote name='xgsjx' timestamp='1323005516' post='1458129'] ...could be due to the fact that it's been marketed like that for so long that the marketing dept (whom aren't engineers) don't want to take a chance & just stick with what they believe the average bassist will buy. [/quote]That. When I contract with a manufacturer to design a cab for them (because they have no engineering department; most companies do not) the specifications are laid out by the marketeers and bean counters. The number one consideration is how it will look, because looks is what sells cabs. The number two consideration is build cost, as these companies are in business with the intent of making a profit. My job is to then do the best I can within those constraints. Sometimes the restrictions I have to work within make it impossible to create what I'd put my own name on. But contract designs don't carry my name, so I just hold my nose and cash their check.

[quote name='allighatt0r' timestamp='1322946821' post='1457688'] using 410s for bass was born out of borrowed guitar cabs, and 115s being born out of borrowed PA subs back in the day. [/quote]Quite right. 30 years ago and more, when 410s were loaded with guitar drivers and 115s actually had the capability to go lower with more displacement than a 410 the 410/115 made sense. But continuing to do so 'because that's the way we've always done it' is as logical as mating a team of Percherons with a Rover for extra pulling power.

[quote name='stingrayPete1977' timestamp='1322930982' post='1457467'] He didn't design it though did he? I would imagine the top brass from Gallien Krueger would be happy to drop in and compare penis sizes Bill, No offensive [/quote]Frankly I've never seen a cab from G-K that indicates they have professional acoustical engineers design their cabs. Eye candy all, IMO. if you want to learn about how cabs should be designed and what really matters beyond looks spend some time on the Barefaced Bass site, it will be time well spent.

[quote name='stingrayPete1977' timestamp='1322919145' post='1457284'] Better tell Flea then Bill........ [/quote]I looked up Flea in the AES members directory. Oddly enough his name isn't there, so chances are he knows no more about how speakers actually work than anyone else who has not studied acoustical engineering. I've been driving for 45 years, that hardly qualifies me to design an automobile. [quote]if both cabs are of a similar quality running off the same amp hence the same EQ settings then the 15 will be producing more of the lower frequencys than the 4x10 even if that 4x10 could handle more[/quote]That's only true if the 115 has lower response than the 410. In most cases they don't. And then there's the matter of driver displacement. As one goes lower displacement requirements go higher. The total displacement of the average 115 is 330cc, that of the average 410 500cc. If the 115 were to add anything meaningful it would need considerably higher displacement than the 410, not considerably less.

[quote name='Lozz196' timestamp='1322866922' post='1456954'] Well the industry standard always seems to favour the 115 at the bottom. I suppose this is due to the "higher" frequencies that come from the 410. [/quote]That's the prevailing notion, but it's incorrect. The average 410 goes no higher than the average 115, while the 115 has wider dispersion. For that matter the average 115 goes no lower than the average 410, so there's nothing to be gained by mixing the two. What is pertinent is that the average 410 will handle more power than the average 115, making the 115 the weak link in the chain. For that reason put the 115 on top, so that when it starts to strain you'll hear it, rather than the 410, and know that it's time to turn the amp down.

[quote name='Ghost_Bass' timestamp='1322840846' post='1456558'] The Genz sounded very thin when standing on front of it but behind (in front of the ports) you could hear all the bass comming out, [/quote]Of course, because the mids and highs coming off the cones are directional. You didn't hear more bass standing behind the cab, you heard less mids and highs, which subjectively is the same thing. The difference in comparison with the Fender cabs has to do with a number of factors, port location isn't one of them. [quote]Sometimes i can't leave the cabinet near a wall to benifit from the reflex, in some places i had to play with my rig on my side, facing me [/quote]The cab doesn't need to be near a wall to benefit from reflex, again the port works in exactly the same fashion unless the cab is so tight to a wall as to upset the cab tuning. The cab does have to be close to a wall to gain boundary reinforcement, but that applies to all frequencies below the baffle step frequency of the cab, not just port radiation. The baffle step frequency of the average cab is 300Hz. Port radiation tends to be centered around 45-55Hz.

[quote name='Ghost_Bass' timestamp='1322830564' post='1456364'] I trust the opinions given above but i had rear and front ported cabs and i feel more bass if i'm using a front ported cab. The front port also helps the drum mics not to capture much of the bass... this is from my experience. If you place a rear ported cab next to a wall you'll get a bit more of the bass reflex but that just made my drummer complaint that he coudn't hear a defined bass sound, just boom... [/quote]You'll feel air flow more with the front port location, but that's not the same as hearing more bass. As noted port radiation is omni-directional, the actual dB level is identical no matter where it's placed. You can get some interactions with a rear port and a rear wall, but those tend to be easy to fix, just pull the cab out another inch or two. If anything putting the cab a bit too close to the wall will reduce boom, not increase it, as it lowers the cab tuning frequency. Putting it tight to the wall can upset things, but again it's an easy fix, don't put it tight to the wall. As to why they're sometimes placed on the rear, usually because the cab size is too small to fit them on the front.

[quote name='fatback' timestamp='1322763158' post='1455625'] Thanks, Bill. The cab on stand is chest height, so not so far off 5 feet. Do you lose midbass at lesser elevations? [/quote]Yes. There's actually a cancellation notch where the difference between the distance from the speaker to the bass and the reflected wave off the floor to the bass is 1/2 wavelength. You can vary the frequency of that notch by both speaker and instrument placement, IMO rotating a knob is far more practical.

[quote name='fatback' timestamp='1322743247' post='1455141'] Alex, is the Midget especially dependent on boundary reinforcement because of its small size (probably a dumb question, I know)? [/quote]No more than any other cab, as all react to boundaries in the same fashion. To be accurate, you aren't losing lows with the cab elevated. That would require lifting it at least 5 feet off the ground. You're reducing boundary loading in the midbass. Using a parametric EQ to notch out the feedback, rather than lifting the cab, would have the benefit of giving additional headroom in the amp and speaker, as it reduces the amp output in the notched bandwidth. It would also give you a bigger bottom, as being able to dial in the precise frequency, notch width and amount of gain reduction will stop the feedback with minimal effect on other frequencies.

[quote name='aidanhallbass' timestamp='1322731923' post='1454912'] I will be looking to put my hartke LH1000 head on two HX410 1000w cabs How is the best way to cable them up? The options I think are, 1. head to top cab using channel A and bottom cab using channel B (which is how i've done it befroe) Or 2. Out from head using Speakon to top cab, then out from top cab to bottom cab, or 3. out from head channel A to top cab (1/4 jack) to top cab then top cab out to bottom cab.. Any wrong way or right way? What power would be used? 8ohm 4ohm?? [/quote]Option 1, one cab per channel. There's no advantage to the others.

[quote name='bremen' timestamp='1322568264' post='1452674'] A solid state amp will specify a minimum load impedance. Anything above this (up to and including no load) will be fine. [/quote]Conversely a tube amp tap impedance is the maximum load, you may go lower. And you can't run tubes with no load, but you can run them in to a dead short. In both cases what matters is the output stage, not the pre-amp.

[quote name='icastle' timestamp='1322425408' post='1450773'] Did you [b]really[/b] just write that? Anyone who's incapable of plugging something into the mains is certainly working in the wrong industry and the 'interconnect' is no harder than it is running a DI out from an amp back to a mixing desk. [/quote]When one uses interconnected pieces of gear independently powered the potential for ground loop noise rises exponentially with the number of devices employed. And if all your kit is in one box you don't have to contend with issues of bad or disconnected cables. If the OP was really comfortable with a complicated system I doubt he'd be as pleased as he is with what he currently has.