Bill Fitzmaurice

[quote name='pockethammer' timestamp='1388937880' post='2327820'] I see bass direct offering deals one of which is....... A GB shuttle 9.2 + a 4X10 (600w 8ohm) + a 2X10 (300w 8ohm). now...... If you rig all this up your cabs are down to 4 ohms & the amp will be capable of pushing 900w. Assuming that in reality the master on the amp won't be past 12 o'clock is this still a mismatch or is it workable? Cheers, John. [/quote]It's a mismatch. To be matched the 2x10 should have twice the impedance of the 4x10, so each driver receives the same power. That means a 4 ohm 4x10, and an amp capable of handling a 2.7 ohm load. It may be workable, but it's not ideal. The position of the master, BTW, doesn't indicated how much power the amp is producing.

[quote name='LukeFRC' timestamp='1388590752' post='2323736'] I've been asking this question too... but with the 12/6/1, but the F112 has same tweeter (the APT80) as simplexx... I know which one would be cheaper to build! [/quote]I did not make the Simplexx as 3 ways because their intent was to be inexpensive and easy to build. For the same reason I didn't design them around $300+ drivers. Besides, if one wants a 3 way that will leave fEarfuls in the dust there's already the Omni 12 and Omni 15 designs, currently on tour with The Animals.

[quote name='RandomBass' timestamp='1388484581' post='2322424'] That's an unusual or poor design solution. I'd be interested to know what forced the former. [/quote]+1. I can't imagine the need for a 230v and a 240v version, that's way too slight a difference to matter. 220v and 250v, maybe. Voltage fluctuations of at least 10% are to be expected and gear should be designed to operate with that much swing.

[quote name='flyfisher' timestamp='1388433755' post='2321983'] [u]even if[/u] the mains voltage is 207 volts (i.e. -10%) or 253 volts (i.e. +10%) or anywhere between then the actual amplifier circuitry voltage supply will still be operating from the same fixed, lower-voltage voltage it was designed for. [/quote]That's true with the low voltage rails powering the pre-amp, usually at +/-15v, and any DSPs, usually with 5v, as those rails deliver low current, so they can be voltage limited with zener diodes or voltage regulator chips. That's not the case with the high current rails for the power amp, which very seldom have any method of voltage regulation. But amp manufacturers build their amps to withstand fairly large voltage fluctuations, so seldom is it a problem. In the US the nominal voltage is 110, but it ranges anywhere from 100 to 125v, and you never hear of problems so long as it's within that range. [quote]Markbass and MSL Professional who do the Markbass stuff in the UK said it wouldn`t be, and to only get one made for this countries power supply[/quote]Markbass will say that to discourage gray market sales, and MSL doesn't want you buying from Thomann.

Your right, it's daft. You won't have equal power distribution to all the drivers. With six 8 ohm drivers you can wire them as series pairs for three sets at 16 ohms, parallel wire those sets for a 5.3 ohm total, which most amps will have no issue with.

[quote name='Leonard Smalls' timestamp='1387875199' post='2316608'] Fair enough... But looking at the frequency response curves in the link, they are far from flat! [/quote]And how would you classify this? That's an Avatar 4x10, and if you think that looks bad, you should see it at 30 degrees off-axis. Electric bass cabs are anything but flat response. As for PA, the EAW KF850 was a benchmark for 20 years. This is what it looks like with and without processing:

[quote name='Jus Lukin' timestamp='1387889166' post='2316882'] For recording a cranked amp sound at reasonable levels I like the idea of a small, low sensitivity cab for micing up. Would something like the Legend BP102, with 200W handling, Xmax of 10mm, and a sensitivity of 91.82db be a good idea in a sealed 1x10? [/quote]No, because cranked amp sound is mainly a product of a low xmax driver, not low sensitivity. That's why guitar drivers typically run 1mm xmax.

[quote name='LukeFRC' timestamp='1387829130' post='2316282'] cheers for the reply Bill I've only got 4 bands, and not swept. [/quote]In that case you'd want to try the combination before committing to it. I know there's at least a few on your side of the pond.

[quote name='LukeFRC' timestamp='1387825536' post='2316207'] just I'm not sure that my bass amp would be flexible enough to eq in the right places, I guess ideally you use a power amp with inbuilt DSP and just plug a preamp into that... I understand that practically the horn design is better and more efficient etc... but how practically do you make it work? [/quote]If you have at least a 5 band EQ then you have enough control for a horn loaded cab. It might not be for you with less than that. I use a Superfly now, before it I had a Hartke 3500, both have all the adjustability I need. PA is a lot more fussy, that's where a 31 band with auto RTA is almost indespensible. [quote]@OP: Low efficiency and at 56hz quite a high frequency rolloff. I doubt it's any good for metal. [/quote]The sensitivity of the Thunderchild is no lower than most 112s, and of those that claim having more most are lying. A Fridge has a 58Hz f3, so that's not out of whack either. It's not a design that stacks well, you can use two with the upper cab inverted to keep the HF horns adjacent but any more and there will be integration issues. OTOH it's no worse than most other cabs in that respect either.

[quote name='Leonard Smalls' timestamp='1387812011' post='2316000'] The flat response part is the difficult bit with horns! From my experience of hifi horn speakers, unless the horn is seriously well-designed it can sound properly honky - as if you'd cupped your hands and shouted through them. Fair enough, it's louder and therefore more efficient, but not necessarily accurate... [/quote]Read this: [url="http://www.avsforum.com/t/1353217/speaker-shootout"]http://www.avsforum....peaker-shootout[/url] Or the first page, anyway. The DR200 and DR250 are my designs, fully horn loaded, not just the tweeters. True, EQ is an absolute necessity, but that's true of all speakers, let alone high sensitivity pro-sound horns, because there are no rooms with flat response. Not that I recommend pro-sound PA cabs for home stereo/theater, this guys system is overkill to the nth degree. But there's no such thing as horn 'honk' with a well designed horn, be it a tweeter or a subwoofer. There are a lot of poorly done horns, though, so the notion is understandable.

[quote name='Beer of the Bass' timestamp='1387733045' post='2315006'] I wonder if one of these horn tweeter designs would still come out ahead if the blind test included a fuzz pedal, or other distortion effects? [/quote]No worse than any tweeter equipped cab, and with the ability to roll off above 3.5kHz, probably a lot better.

[quote name='bassman7755' timestamp='1387726850' post='2314919']why-arent-more-bass-cabs-designed-like-this [/quote]Because they don't look like every other cab. Bass players aren't quite as bad as guitar'd players when it comes to buying with their eyes rather than their ears, but they come close. The ideal cab showroom would have all cabs hidden behind a scrim, so that you couldn't see the cabs you were trying, you could only hear them. Said showroom wouldn't stay in business a week. [quote]Its almost there is some unwritten law against using a large flared horn in a "bass" speaker, when surely it is the obviously thing to do when designing a flat response 2-way system ?[/quote]Obvious to who? Duke approached the design with a clean sheet of paper and a real engineers perspective: [i]How do I make the best speaker possible for this application? [/i]That's diametrically opposed to the standard of most companies, which is: [i]What do we make these look like so that they'll sell. [/i]

[quote name='Jus Lukin' timestamp='1387568987' post='2313569'] Ok, cool, thanks Bill. So could I put words in your mouth to suggest that the Alpha 12s would sound much like a Fender speaker, but with better spec?[/quote]+1, the midrange response is quite similar, but with a lower Fs and 2.4mm versus 1mm xmax the lows are what we wished we could have had from Jensens. The only way I was ever able to get a clean low E back then was after I went from two Fender 2x12 cabs to a pair of 4x12 Kustom column speakers, that would have been 1968. [quote]Also, do you think the same might apply to a Marshall, for that snarling grit they put out [/quote]Safe bet.

[quote name='bumnote' timestamp='1387564740' post='2313503'] What about the phil jones 5" jobbies? I originally thought it was a gimmick but it works really well. I would love to try on of the big rigs with 24 or more speakers [/quote]Displacement is displacement, whether you get there with one large driver or a whole bunch of little ones. Using smaller drivers offers the potential advantages of higher frequency response and broader dispersion, but only if you use them correctly. That means either arraying them vertically or, if clustered, bandwidth limiting, so that only the innermost drivers operate to the top of their range, while the drivers to either side are progressively low passed to lower and lower frequencies the further they are from the cabinet center. PJ doesn't do the former, I don't know if they do the latter. The disadvantage to smaller drivers is cost, as for a given displacement using larger drivers generally costs less per cubic centimeter of Vd.

[quote] putting a pair of Jensen C12Ks in a Fender style sealed cab to be pushed with even 50watts of Bassman induced power sounds like it could risk over excursion. [/quote]I had a 65 Bassman with two cabs and still couldn't get a clean low E with any volume. You can get a good vintage tone in a sealed cab with Eminence Alpha 12s, and they have over twice the xmax of C12s. The Beta 12 has plenty of xmax, but doesn't have quite the high mids that the Alpha does. I'd go Alpha if you want more grit, Beta if you want more clean.

[quote name='LukeFRC' timestamp='1387220716' post='2309566'] Hmmm I think the back side is being treated as a horn of some kind. [/quote]They claim that it's a waveguide, based on the fact that it's tapered. A taper does not a waveguide or horn make. It's a tapered ducted port. [quote]I would be very interested to know what the 'cost no object' BFM solution would look like, if you cared to design it. [/quote]Simplexx is a cost no object bass reflex. There's only so much you can do with a bass reflex. You can load it with more expensive drivers, but otherwise that's about it. [quote]There is a niche for high performance bass reflex cabs, currently occupied (IMO) by Audiokinesis, Acme, BF, Baer, Greenboy, etc,[/quote]What makes them different than more pedestrian options, like Peavey and Ampeg, is the use of premium drivers, like the Eminence Kappalites. The engineering isn't all that different, other than those that use midrange drivers instead of tweeters. I received my Kappalite samples six months before they went on the market, I had bass reflex prototypes using them a year before Greenboy put anything out, and I designed one of the best reviewed 1x12/1x5 cabs that uses an OEM Kappalite 12 (I can't say which, as the first thing you sign when taking on a design contract is a non-disclosure agreement, as no company wants it known that they employ independent designers). I don't use a Kappalite loaded bass reflex myself, I use a Jack 12 Lite. I introduced Simplexx because I had many requests for an easy to build design that still met my quality standards, not because bass reflex is better than or even equal to what I already offered.

[quote name='brensabre79' timestamp='1387469442' post='2312360'] [url="http://www.ebay.co.uk/itm/like/400617627560?hlpht=true&ops=true&viphx=1&lpid=95&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=95&ff19=0"]Here's[/url] one under £70. [/quote]Unfortunately its specs are quite the opposite of those needed. if the OP wants a worthwhile driver he needs to spec match it as close as possible to the Delta Pro 15. If he doesn't care how it sounds or if it will last more than three notes that's a different story.

The original driver is an OEM variant of the Eminence Delta Pro 15.

[quote name='LukeFRC' timestamp='1387147740' post='2308823'] stumbled upon the physics defying cabs and tried to work out what on earth they were talking about... [/quote]What they've done is to take a bass reflex cab and put a reflector inside that directs the driver rear wave out the ports. It's been known since the 1940s that if you do that the front and rear waves will meet at various angles of phase, resulting in major reponse peaks and valleys. And since the 1940s bass reflex cabs have used damping inside the cab to prevent that, allowing only bass frequencies close to the port tuning frequency to come from the port. Damping the rear wave is one of the most basic tenets of speaker design, but these guys have managed not to learn that. The other feature they use is cross-fired drivers, but that's hardly new or unique. They use extremely expensive drivers, so their prices are off the charts. But they look cool.

[quote name='LukeFRC' timestamp='1387137630' post='2308598'] +1 I didn't even realise until yesterday Bill wasn't on TB anymore, no idea why (I don't want to know)[/quote] Explained here: http://billfitzmaurice.info/forum/viewtopic.php?f=7&t=18092 [quote]Mind you TB is an odd place I was reading all this hype for some "vortex" speakers and then went and looked at other more pro audio design forums... different response there!... [/quote]Those speakers attempt to defy the laws of acoustics. They fail in that attempt. But as our President Lincoln famously said (and probably paraphrased Shakespeare in so doing) you can fool some of the people all of the time. [quote]When designing a three way or two way full range system, how do you decide where to cross over? When polar response starts to drop off at the woofer[/quote]That's the primary concern, or should be anyway, but you do have to balance it against cost, as the lower you cross over the more expensive the components, not just for the driver but also the horn and crossover components. In a cost no object design I'd go even lower than I did with the Simplexx, but for most builders cost is an object. Most commercial cabs go too far in the other direction where that's concerned, and cross over way too high. Oddly enough the only ones who benefit from their cost savings are themselves.

[quote name='xgsjx' timestamp='1387101526' post='2308142'] A couple of weeks ago, my guitarists found out what dispersion is when the room we hired had a 4x12 guitar cab, stood right in front of it & kept turning it up because he couldn't hear himself. I suggested that he move further away & he stepped forward & to the side. He still thought he was quiet. The other guitarist pulled him over to where he was standing, straight across from the cab & he stood there for the rest of the sesh (& turned down too). [/quote]Not the sharpest tacks in the bin they are. I once mixed a band where the guitar player insisted that he not be mic'd. As I knew would be the case he couldn't be heard outside of a small cone shaped area directly in front of his cab. First break he asked how he sounded. I told him I didn't know, since ge wasn't in the PA I couldn't hear him. His solution? Turn his amp up. Needless to say that did not improve matters a whit. Go to a guitar forum and you see them go on forever about this speaker, that pedal, these strings, those picks, all in search of a magical tone that will make them the next Clapton, yet most are profoundly clueless about how to get said tone heard by more than 15% of the audience. The best player I've seen since Mike Bloomfield is John Mayall's current guitarist. His Fender Twin is aimed across the stage at the drummer. He doesn't hear it directly, like the audience he hears it through the PA.

[quote name='xgsjx' timestamp='1387069801' post='2308013'] What I meant was that a driver's diameter doesn't mean it has a particular sound. [/quote]+1. Within reason you can get pretty much the same result with any cone size from an eight to an eighteen, with the single exception of the dispersion angle. It isn't all that practical to get 30Hz out of eights, or 4kHz out of eighteens, but it can be done. There is absolutely no characteristic ten vs twelve vs fifteen sound.

[quote name='xgsjx' timestamp='1387014944' post='2307384'] Cone size makes no difference to the sound. [/quote]Cone size has a direct effect on the angle of dispersion. When the cone is one wavelength or more across dispersion narrows; a cone that's too large for the frequency being radiated is what causes beaming. While larger cones tend to have better low frequency response, and smaller cones tend to have better high frequency response, those are not absolutes. Dispersion is, and it's the primary reason why midranges are smaller than woofers, and tweeters smaller than midranges. A relevent point is that when two drivers are placed side by side the horizontal dispersion is the same as if they were one driver twice their size. Thus a pair of tens side by side have the horizontal dispersion of a twenty inch driver, explaining why a fifteen can have better highs off-axis than a two ten cab. Twelves side by side are even worse. Almost every guitar player running cabs with side by side twelves complains about beaming, as do those in the audience in front of them who get their heads taken off by even an AC 30, let along a stack, while those standing to the side can't hear them at all. The physics involved are quite simple, but few guitarists have a clue how speakers work, beyond "you plug an amp into them".

[quote name='nottswarwick' timestamp='1386967530' post='2307073'] Any thoughts? [/quote]Most tweeters don't do anything below 4kHz, and most players don't have a lot of content in their tone above 6kHz, so getting along without them you don't lose much. What most players can benefit from is better response between 2kHz and 5kHz, where midrange drivers operate. But midrange drivers and their crossovers are more expensive than tweeters, so they're rarely seen.

[quote name='jimbobothy' timestamp='1386522066' post='2300992'] Any suggestions please? [/quote]If it farts out turn down.