Bill Fitzmaurice

[quote name='sifi2112' post='230846' date='Jul 1 2008, 03:04 PM']combined with 2 x Celestion BN10-300x perhaps ? [url="http://professional.celestion.com/bass/green/index.asp"]http://professional.celestion.com/bass/green/index.asp[/url] cheers Simon[/quote]Without full specs one can't even venture a guess.

[quote name='alexclaber' post='230493' date='Jul 1 2008, 08:24 AM']Doesn't look a great idea to me because the Kappa and Gamma speakers are midrange speakers, not true woofers. The thermally limited power handling may be high but the excursion limited power handling (basically Xmax) is very low, which equals farting at low volume with even moderate amounts of bottom. Fine if you're biamping and using something else to carry the lows though. Alex[/quote]The Kappa Pro's xmax is far less of a concern than the very low Qts, which chokes off bass response. Both of these drivers are marginal at best for bass. They're popular with both DIYers and manufacturers due to their high power ratings, but high power alone does not a good bass driver make.

[quote name='Balcro' post='229892' date='Jun 30 2008, 12:47 PM']Meanwhile I'll just have to save up for an octaver special effects pedal followed by another one in series. Cheers, Balcro[/quote] No need to do that. just use excessive EQ to boost the bejesus out of the first octave, then run it through PA subs capable of going an octave lower than bass cabs do. That's how ham fisted FOH engineers can take a perfectly good bass and make it sound like crap. The worst mixed gig I ever saw was Ringo and friends, with Greg Lake on bass. The bottom was so over boosted that it drowned out the entire band. OTOH the midbass was so subdued that whenever he went above C he completely disappeared from the mix, you could only tell he was playing by watching his hands. Needless to say the sound coming from the PA bore no resemblance whatsoever to that from the two SVTs behind him on the stage. Talent wise Ringo had one of the best bands ever assembled, yet one idiot at the FOH ruined the entire exoerience.

[quote name='Balcro' post='229673' date='Jun 30 2008, 08:16 AM']Devils advocate time. If low B on a five string is 31 or 32Hz, does that mean even every 15" is unsuitable? ? ?[/quote]If it did then the Fridge (f3=58Hz) would be even more unsuitable. While the fundamental of the low B may be 31Hz it's the length of the string that determines where the power bandwidth lies. Should you wish an instrument that puts out the low B fundamental with equal power to the harmonics you'll need long arms and big hands, the scale would be nine feet long.

[quote name='redstriper' post='229432' date='Jun 29 2008, 08:53 PM']To clarify my requirements - I'm considering an SWR Big Ben 18" cab - how would the BFM omni without horn and tweeter compare in sound and weight?[/quote] The O15 goes louder and lower. Not using the midrange driver would be a bad idea, as the woofer rolls off above 500Hz. Attenuating mids as desired with your amps tone controls. If you leave the mid driver out and find the mids lacking you're up the creek.

[quote name='redstriper' post='229403' date='Jun 29 2008, 07:18 PM']I'm intrigued by this cab and wonder if one would suit me. I only play dub reggae and don't want any treble or upper midrange in my sound - just deep warm bass. Which of BFM's cabs would be most suited to my sound and desire for lightweight and portability?[/quote] O15, standard or tallboy, leave the tweeter out. As for lightweight and portability, google 'Hoffman's Iron Law'. Big bottom does not from small cabs come.

[quote name='gilmour' post='229062' date='Jun 29 2008, 10:36 AM']Surely it's just down to manufacturing costs? Costs of making up moulds etc. would be very inhibitive given the relativley small number of consumers, and the cost of alternatives.[/quote] +1. Manufacturing costs are at least double that of plywood. Some forays into fiberglass and other composite constructions have been made, most have failed.

[quote name='jakesbass' post='229205' date='Jun 29 2008, 02:40 PM']Sorry if I missed this elsewhere, but what cabs do you have? are they matched?[/quote]Unless he built them himself, not likely. To take from his example: ABM 115 37Hz - 2kHz 98dB 1W@1m ABM 210T 75Hz - 20kHz 102dB 1W @ 1m These two cabs share bandwidth from 75Hz to 2kHz. Throughout that range they will both augment and detract from each other's output. In a 'matched' system frequency response of the 1x15 might be on the order of 37Hz-1kHz, with the second cab 1kHz-20kHz. They would employ either a passive crossover or bi-amping for frequency routing, and since they do not have overlapping bandwidths they could only augment each other. More important, one does not require tens to operate only down to 1kHz. Eights or even sixes would do, they'd do it better, and would do so in far smaller packages, leaving the option for a second 1x15 should the need arise for more low end capability.

[quote name='bass_ferret' post='229054' date='Jun 29 2008, 10:18 AM']I could be wrong - it did happen twice.[/quote]Not this time, you're spot on.

[quote name='phatbass787' post='228673' date='Jun 28 2008, 01:43 PM']Ahh I forgot about that, i think from what ive heard the 4x8 is split into two 4 ohm 2x8's so you run an input into each side and get full whack, anyone heard or got one of these cabs? Be interesting to know what it sounds like[/quote] I doubt it would do the OP much good. Four eights probaly aren't going to have more displacement than his 1x15, possibly even less. IMO it's displacement that's his limiting factor, not power. If his Diesel is loaded with an EVM it can't make use of much more than 100 watts through most of the bass range anyway, so one channel of the Fly has enough to drive it to full output.

[quote name='LeftySteve' post='228089' date='Jun 27 2008, 10:15 AM']Much as I like my Superfly I am finding it's use restricted by the inability of it to work in bridged mode to give 500W into 4ohms. Steve[/quote] Even if you could you'd only get an additional 3dB output, and that assumes that you have a cab that's not displacement limited to 250 watts or less anyway. The displacement limited power rating of any cab is a secret more tightly held than Joan Collin's real age, but on average it's 50% of the thermal rating at best, and usually less. Ergo, if you really need more than what the Superfly will deliver with one channel into one cab chances are you need a second cab anyway.

[quote name='tauzero' post='227185' date='Jun 26 2008, 06:02 AM']If they're 1/2 wavelength apart, a little thinking about the geometry of the two drivers and the listener's ear will show that the only place you can get phase cancellation will be if you are in line with them, ie. at 90 degrees to the speaker axis. If they're .7 wavelength apart, you'd get phase cancellation outside 45 degrees off-axis. You can only get phase cancellation over the whole arc in front of the speakers with 1 wavelength separation, if my quick scribblings and mental arithmetic is correct.[/quote] Kal is only partially correct, but he's a reviewer, not an engineer. The 1/2 wavelength he's refering to is the center to center to center distance at the crossover frequency in a vertically aligned MTM, which has nothing to do with the required spacing of horizontally placed drivers to prevent combing within their operating bandwidth. That is one wavelength, measured center to center. In those frequencies where that distance is less than 1 wavelength combing will not occur, where it is longer it will.

[quote name='Biggsy' post='225130' date='Jun 23 2008, 11:20 AM']I don't think cabs get much more efficient than my current ones[/quote]Possibly not commercial cabs, but no direct radiating cab is particularly efficient. One of the reasons for DIY is not having to live with the inefficiency of direct radiators.

[quote name='obbm' post='224877' date='Jun 23 2008, 06:43 AM']I strongly recommend that you read paragraph 2 on page 8 of the Hartke 5500 User Manual.[/quote]The technical acronym for this proceedure is RTFM.

[quote name='bnt' post='223644' date='Jun 21 2008, 10:51 AM']The power lost as heat in these components is proportional to the [i]square[/i] of the current (P=I²R), so if you double the current, the losses are [i]quadrupled[/i].[/quote] That's part of the overall no free lunch equation, which also encompasses output device and power supply failure if you go too low with the load impedance. Were it not so we could use 0.4 ohm speakers. That would be a very good thing as far as the efficiency of the speakers is concerned, but would require an entire retool of the amp/speaker relationship from low voltage high current to high voltage low current. Unfortunately Tesla wasn't involved when the dynamic loudspeaker came about.

[quote name='Musky' post='223115' date='Jun 20 2008, 12:40 PM']why aren't at least some manufacturers making amps with power supplies that would be capable of delivering the kind of power needed to make the most of the amp? Expense and/or weight?[/quote]Physics and the reality that there is no such thing as a free lunch. In any event, power is not the limiting factor of how loud an amp will push a speaker. A speaker's output is determined by voltage swing, not power consumed. The entire concept of going to as low an impedance load as one can to 'get all the watts out' of an amp is intrinsically flawed. The main result of so doing is to cause the amp to generate higher heat levels, shortening component life.

[quote name='Musky' post='222991' date='Jun 20 2008, 10:08 AM']Or am I missing something obvious here?[/quote] Nope. You're pretty much there. Scenario 1: You run your 500 watt/8 ohm SS amp with a 28v output into an 8 ohm speaker. It will deliver 100 watts. Add a second 8 ohm speaker, leaving all the settings the same. The voltage swing will still be 28 volts, the current will double into the halved impedance load, and you will get 200 watts. Scenario 2: Run your 500 watt amp at full power into an 8 ohm cab. The output swing will be 63 volts. Add a second 8 ohm cab. You won't get 63 volts, because the amp's power supply isn't capable of delivering maximum voltage into all impedance loads. It generally drops by a factor of .7 for each halving of the load impedance, so instead of 1,000 watts into 4 ohms you might get 700. So while you will get a doubling of power with a halved impedance load if the amp is well below full power you won't get it at full power.

[quote name='gypsymoth' post='222372' date='Jun 19 2008, 01:27 PM']the fender/fender combination is IT and is unbeatable - because that is what this contraption is supposed to sound like - technically right or not.[/quote]My first Fender/Fender wasn't first generation, but close enough to it, 1965 Jazz/Bassman, bought new. The damn thing farted out on the first low E I hit and every one subsequent. Never satisfied with how inept it was at actually producing useful bass I studied audio engineering to find out why. Today I owe my livelihood to Leo Fender's never having done the same.

[quote name='lowhand_mike' post='222228' date='Jun 19 2008, 10:27 AM']the same as in cross firing?[/quote] +1, though you don't have to limit yourself to a pair of drivers, you can use four or more to get the added sensitivity of an array. [quote]it is perhaps worth noting that all these problems were recognised waaay back[/quote]+1, though waaay back starts in 1927, when films added sound. Until the 1970s most of the innovations in sound technology were driven by what was the single largest industry that employed sound reproduction, and that was the moving picture industry. The shift away from the movie industry as the leader in the field started with the introduction of the VCR, which made home theater a reality. In terms of units sold home theater now accounts for the largest slice of the audio pie.

[quote name='lowhand_mike' post='222016' date='Jun 19 2008, 06:31 AM']i can understand roughly what those guys were saying about wavelengths etc but are they actually talking about speaker positioning....where-as we are talking about the wave lengths coming from a single box,.[/quote]Both. The rules that apply for placement of speakers within a room also apply to drivers within a cabinet. Just think of the cabinet as a room within which drivers reside, and that what differs between the two scenarios is the size of the 'room'. [quote]centre speakers for home cinema and lots of centres have two woofers each side of a tweeter[/quote] Same rules, you need to cross the woofers to the tweeter no higher than the 1 wavelength center to center distance between the woofers. But that only addresses combing, not dispersion, which is better on the horizontal plane with the woofers vertical. The inability to place woofers vertically below a TV is problematic, but can be compensated for by having them in a concave array.

[quote name='bass_ferret' post='221834' date='Jun 18 2008, 06:55 PM']Now i am really confused - combing and beaming![/quote] Beaming is when the dispersion angle is so narrow that you can't hear the mids or highs if you move a foot to either side. It's why you can't hear the guitar cab four feet to your left and four feet in back of you, whilst the poor lady at the table in front of the guitar cab fifty feet into the club stuffs her ears full of napkins in a futile attempt at self-defense. Combing is when the frequency response of the cab constantly changes as you move across the soundfield and literally doesn't sound the same in any two spots. The other blokes complaining you were too loud while you couldn't hear yourself probably involved both beaming and room modes, where in the spot you were standing reflected waves off the walls and/or ceiling cancelled out much of your low frequency output, while elsewhere in the room that was not the case. None of these conditions are at all desirable.

[quote name='lowhand_mike' post='221575' date='Jun 18 2008, 12:40 PM']i guess thats what raggy, and myself were thinking. or would it be that because they are close to side by side that they still suffer?[/quote] Two factors are at work. The closer the driver centers are to vertical the higher the frequency before combing starts, which happens when the driver centers are more than 1 wavelength apart. Fully vertical there can be no combing, but if the driver only goes to, for instance, 3kHz, then a CTC of four inches is sufficient. The second factor is the total width of the radiating plane, outer cone edge to outer cone edge. As that exceeds one wavelength the horizontal dispersion angle shrinks, eventually to the point of beaming. So even if combing isn't an issue dispersion is, especially considering that four inch wavelength at 3kHz. Even a single ten will be beaming up that high. Now consider a 2x12 or 4x12 guitar cab with driver CTC on the order of 16 inches and a radiating plane on the order of 22 inches wide, and the 4kHz tones they're pushing with only 3.4 inch wavelengths, and one can hardly tell which is worse, the combing or the beaming.

[quote name='stevie' post='221527' date='Jun 18 2008, 11:47 AM']1 wavelength is way too much for interdriver spacing. Anyone who familiar with the laws of acoustics would know that where the time displacement between two low frequency drivers corresponds to one-half of one wavelength, the outputs of the two low frequency drivers will null. 180 degrees and all that. Spacing needs to be less than half a wavelength. Back to the Loudspeaker Cookbook for you. It's interesting that you use the term 'debate' here, because I have not seen you debating on any of the threads you have been involved in on this forum - merely pronouncing, and belittling others.[/quote]Stevie, the one compliment I will pay to you is that you remind me very much of the Honorable President of the United States, George W. Bush. Like he, everytime you open your mouth you somehow manage to stick your foot further down your throat than the time before. Your above statement is complete and utter gibberish. I'll let Alex point out why if he cares to, I have far more important things to attend to. Cutting my toenails is first on the list.

[quote name='lowhand_mike' post='221142' date='Jun 18 2008, 04:43 AM'] ha i just thought one was a backup. doh! bill i'm glad you mentioned about being able to have side by side configurations if you go one wavelenthg out of p[hase or what ever it was. i was wondering about that last night. as in why cant we actually still have speakers side by side but performing correctly?[/quote]You can, as seen in this pic of a typical PA line array cab The woofers are at either end of the cab, crossed over at 350 Hz to the mids that lie just inboard of them. Being closer together the mids can run to 1.5kHz, where they cross to the center mounted HF drivers. [quote name='alexclaber' post='221378' date='Jun 18 2008, 08:55 AM']Something I've noticed from modelling drivers in WinISD Pro is that the phase difference between models is rarely so huge as to cause cancellation if the cab tuning frequency is the same.[/quote] It's a bit more complicated than that, and while I'd rather not get even deeper into the science of it, time align also enters the equation. Phase response is the major culprit at low frequencies, and if the cabs are properly tuned to their drivers one would expect a 2x10 and a 1x15 fb to be off by at least 10 Hz. In the midbass phase response becomes moot, but when you hit the midrange time-align becomes critical. For the best known example research the (in) famous Eleanor Powell tap dancing fiasco that led to the development of the Altec A7 style of theater boxes. For the sake of simplicity I lump the phase response and time align issues into the same bundle, since time align is a phase issue as well, though from a different source.

[quote name='JonnyM' post='221059' date='Jun 17 2008, 08:16 PM']Can't resist posting these pics... [attachment=9739:1974_07_21.jpg] [attachment=9740:grateful..._sound_1.jpg] The backline IS the PA (the bass "rig" is the tallest stacks the right and left of the drums: 2 vertical stacks of 15's, 18 per stack... (I have an LMII and 2x10 Traveller and when I need to, I'll get another identical 2x10 to stack vertically... )[/quote] The Dead were probably the most technically literate band of all time. They did their homework for sure. Their most ingenious invention was to use two mics side by side, wired reverse-polarity. They'd sing into only one, but any foldback was equally received by both, where the reverse polarilty cancelled out the signal, allowing outragous levels with no feedback.