Bill Fitzmaurice

[quote name='richrips' post='564882' date='Aug 10 2009, 07:53 AM']hi bill, i'm swinging towards your idea for a couple of 1x12+horn jack cabs. before i place my order, a couple of questions: What speakers would this combination use for a good power-weight ratio. i'm quite keen on neo celestions but if you can recommend a 12inch driver,a tweeter and a crossover (or simple plans for one...) available in the uk, i can start doing sums. do you have a response curve for a 1x12 jack cab? Any user feedback on Bills 1x12 jack cabs would also be much appreciated! I'm glad that this is starting to point at a specific build route after all the discussion! Thanks to all the contributors, especially Bill, Mr.T, Alex, Stewart and i'm sure i've missed a few.... Cheers team! rich incidentally, i'm using a peavey 2x10 tvx and a bw 115 both mint condition unlike my back (which i screwed working for removals..) i'll be selling soon from cardiff, plymouth and anywhere in between. also i drive to maidenhead occasionally.[/quote]For specific information regarding my designs you should go to my forum, [url="http://billfitzmaurice.net/phpBB3/"]http://billfitzmaurice.net/phpBB3/[/url]. Thanks.

[quote name='Mr. Foxen' post='564470' date='Aug 9 2009, 04:14 PM']BFM's designs are probably totally awesome and will do what you want, but if you want to save $15 and get something a little more trad looking, go for one of Greenboy's fEarful designs.[/quote]Where basic bass reflex boxes are concerned the fEarful are as good as any commercial offerings, and better than most. I'd be hard pressed to name a commercial cab that's as well engineered, or even close to it for that matter. I've also recently prototyped a couple of 12/6 cabs for a manufacturer, similar to the fEarful 12/6, using the 3012HO driver. They're nice cabs, a lot better than the high priced 'boutique' 1x12s out there. OTOH side by side with my Jack 112 loaded with a only a 2512 they're very much also-rans. You can only do so much with a bass reflex box.

[quote name='richrips' post='564251' date='Aug 9 2009, 12:06 PM']I feel like i should be paying for this much knowledge..... alas, a couple more questions! 1.Is dispersion affected by the width of a cab or simply by the width of the speakers in the cab? (for a traditional box with speaker in front arrangement)[/quote] Both. [quote]2.Why is it bad to use different sized speakers to produce the same frequencies? (surely almost every rig [cue bi-amping argument...] with parallel identical outputs running in to two cabs where one is, say, a 4x10 and the other a 1x15, would be a victim of this fault?[/quote] Because their outputs are different they can detract from each other as much as they augment each other, with a different result at every frequency. Identical drivers/cabs will only augment each other. [quote]SOOOO.... what do i build? Thanks, Rich[/quote]What I said in my first post.

[quote name='Stewart' post='563944' date='Aug 8 2009, 08:04 PM']Take a look at RCF 4PRO 7001 as one example. [url="http://www.rcf.it/web/rcf/products/pro-speaker-systems/4pro-series/4pro-7001a-mh"]RCF 3way arrayable[/url][/quote] Child's play compared to this: [url="http://www.sweetwaveaudio.com/sales/l-acoustics/kudo.php"]http://www.sweetwaveaudio.com/sales/l-acoustics/kudo.php[/url] One could use a Kudo or two for bass, if you've got a mind to, and the price of entry.

[quote name='dood' post='563691' date='Aug 8 2009, 02:42 PM']If drivers of different sizes are in one box and are crossed over correctly, then should they in theory be in a vertical line for best dispersion?[/quote]If you really know what you're doing you put the woofers on either side, the midranges just inboard of them, and the tweeters in the middle. With the proper driver spacing and crossover points you can use this arrangement to deliver very uniform dispersion across the full bandwidth of the cab, and you also can stack multiple cabs vertically for longer throw with no degradation in the quality of the sound. This level of technology is commonplace in the PA world, with prices starting around $4000 per cab, and is as far removed from the typical electric bass cab as a Bentley is from a pair of roller skates.

[quote name='richrips' post='563593' date='Aug 8 2009, 12:39 PM']In the picture below, the speakers are staggered. Does this diagonal arrangement have any advantage/disadvantage over a purely vertical arrangement?[/quote] It's better than horizontally mounted, but not as good as vertical. [quote]Would a diagonally arranged 2x10 on top of a vented 1x12 cab (made possibly using one of bills designs to squeexe every last ounce of low out of it) be a scientifically sound (lol) solution?[/quote]Scientifically speaking never use different size drivers to cover the same bandwidth. Yes, it's seen all the time... for the same reasons that 4x10s are.

[quote name='Mr.T' post='563526' date='Aug 8 2009, 10:29 AM']Forgive my ignorance here.... I thought you said "The wider the source, the narrower the dispertion pattern" ????[/quote]You must also consider the frequency in question. Dispersion is not a static figure, it varies with frequency as well as the size of the radiating source. But your question brings up a good point, that being why high frequency sources are smaller than low frequency sources. One of those reasons is dispersion. The higher the frequency the smaller the source must be or dispersion will be unusably narrow, as in using eighteens for guitar. [quote]coupling output is when the bass makes the floor (or the box it's on) vibrate, causing the floor to generate sound, yes?[/quote]No. Boundary Coupling is when the source is close enough to a boundary to reduce the pi radian size of the space being energized, as in free-space, half-space, quarter- and eighth-space. I wish there was a simple non-technical way to explain it, but there isn't. When a nearby surface sympathetically vibrates it does generate sound, but that's a different scenario entirely.

[quote name='Zach' post='563498' date='Aug 8 2009, 09:40 AM']this may be a stupid question, but would a single 2x10 (or 1x12 in my case) therefore have better dispersal if put vertical on an empty box at chest height, instead of sitting on the floor?[/quote]Yes, though if the front of said box isn't a solid surface you'll lose coupling output above the frequency where the elevation is equal to 1/4 wavelength. With a 3 foot lift that's about 100 Hz. However, 'boom' also occurs in the vicinity of 100-180 Hz, so if you've got a boomy room elevating the cab can help tame it. [quote]and also, since my 112 has a tweeter, which way up is better? tweeter above or below?[/quote] Tweeter above, as tweeters have narrower dispersion than woofers. [quote]it is my honest opinion that two 2x10 cabinets stacked vertically look totally w**k when compared to a 4x10[/quote]Don't think for one moment that the marketeers aren't well aware of your opinion. That's why cabs are made the way they are. If engineers ruled the roost, and didn't particularly care about the source of their next meal, the 4x10 would have gone the way of the Dodo twenty years ago, and with them all the other cabs with horizontally placed drivers. But even engineers have to eat, explaining why so many who do know better continue to build what the market demands, as opposed to what would best suit needs.

[quote name='Mr.T' post='563332' date='Aug 8 2009, 05:01 AM']Can you help me to understand this concept? I can see that having multiple drivers vertically would extend the coverage vertically, but not how having two rows of drivers (traditional 4x10 or 8x10) would then make that coverage horizontally narrower.... am I missing something?[/quote] You've made one of the most common mis-assumptions about how speakers work, which is that they radiate sound in the same fashion that light bulbs radiate light, ie., proportionally to their dimension. The opposite is the case. The wider the source the narrower the dispersion, the higher the source the less the dispersion on the vertical plane. This means that a vertical 4x10 also has half the vertical dispersion as a standard 4x10, which at first glance may seem counter-productive, but it's not. At the distance you're standing relative to the cab getting the upper drivers closer to your ear level still allows you to hear them much better than you can with them down low. At the same time farther away from the cab the narrowed vertical dispersion puts more sound into the audience, where you want it, and less into the floor and ceiling, where you don't. So not only does the vertical array give more uniform audience coverage, it's also louder within the audience for a given amplifier output.

[quote name='lateralus462' post='563256' date='Aug 7 2009, 08:38 PM']but then again at some point someone is going to want to add more speakers - in fact it is fairly usual for someone to want to add, say a 15" cab or another 4 x 10 to their rig -[/quote] Also done on the basis of looks, not utility. The number one deficiency of commercial bass cabs is that they're too small for the drivers contained. One can build a 2x10 with the same low frequency output capability as the average 4x10 by simply making the cab large enough. So why don't manufacturers make cabs as large as they should? Because the average player would think 'it doesn't look right' not stuffing so many drivers into as small a box as possible that it takes a shoehorn and a good load of lubricant to get them to fit. A pair of well engineered 2x10s would deliver all anyone could actually need. [quote]in my opinion any problems with dispersion aren't really a problem in a band enviroment either -[/quote]That depends on how much of the audience you're content to have hearing the same tone that you do. With a 4x10 few will. You can't hear the mids and highs that pass by you at calf level, so you crank them higher. That means the small segment of audience within the cab's 'sweet spot' get nailed with excess mids and highs, while the rest don't hear them even as well as you do. Tilt the cab back and you can hear the mids and highs, but then no one else can. That's one reason why the 8x10 or stacked 4x10 is so popular amongst those who use them, the drivers are high enough so that you and the audience within the sweet spot hear the same thing. A vertical 4x10's/vertically aligned 2x210 sweet spot is literally twice as wide as that of an 8x10 or stacked 4x10s, making it a win/win rig.

[quote name='E sharp' post='563086' date='Aug 7 2009, 04:29 PM']I seem to remember a couple of their cabs being reviewed in Bass Player a few years ago . They picked up on the switch issue (the technicals are a bit beyond me , and I defer to Bill and Alex on this) and Accugroove's reply was a bit snotty . Haven't Epifani come up with a similar silly switch recently ?[/quote] There was a thread on TalkBass exposing the AccuSwitch, it probably set a record there for length. The initial response by A-G was 'we applied for a patent, and won't reveal the specifics until it's granted', which is piffel, since patent protection is retro-active to the date of the application. When the switch's circuitry was revealed and shown to be worthless A-G 'lawyered up' and wasn't heard from on the subject again.

[quote name='Protium' post='563058' date='Aug 7 2009, 03:52 PM']What about a vertical 410? The manufacturers of 4x10's must be doing something right or else no one would buy them...[/quote] Cab manufacturers build what they believe is most likely to sell. What's most likely to sell is what 'looks right'. Unfortunately what please the eyes the most pleases the ears the least, but we are creatures who are dominated by the visual sense. If blind bassplayers had a standard 4x10 and a vertical 4x10 put before them to choose from the vertical 4x10 would win every time. Discriminating sighted players would probably lean towards the vertical 4x10 as well, if they had the option, but the marketeers don't make that option available to them to make the comparison. BTW, said blind bassplayers would also tend to prefer the vertical 4x10 to an 8x10, though not by such a wide margin. That's because to a very large degree what makes an 8x10 sound like an 8x10 is the height of the driver array. Since the vertical 4x10 would be the same height it would share many of the same acoustic properties, though by being narrower it would have even better dispersion.

[quote name='richrips' post='562865' date='Aug 7 2009, 10:49 AM']which 2x10 plans would you recommend?[/quote] None. I only do high sensitivity cabs myself. But if you do go with a standard style 2x10 make absolutely sure you use the driver recommended for it. Choosing a driver and then designing a cab to work with it can be done, but only if you possess a rather high skill level in acoustical engineering. If you don't leave the designing and driver choices to one who does. [quote]But has worked for god knows how many bass players?!! I actually like 4 x 10's as a cabinet, they may not be "correct" but they still sound good![/quote]One might also conclude that a Ford Focus is the epitome of automobile engineering expertise... if one had only a Yugo to compare it to.

Don't build a 4x10. It's the poster child for how a speaker cabinet should not be built. Do a pair of 2x10, stack them with the drivers in a vertical line.

[quote name='BigRedX' post='558275' date='Aug 2 2009, 04:27 AM']it does appear to be fairly packed with components as it is, and tends to run pretty hot.[/quote]Get rid of the aluminum outer casings. If they'd been properly machined with fins for heatsinking the amp would run cooler, but being the slabs they are they retain heat instead of sloughing it away. They also double the weight of the amp. I rack mounted mine, and with a computer style fan ventilating the rack it's never more than slightly warm to the touch.

[quote name='thedontcarebear' post='560390' date='Aug 4 2009, 12:18 PM']going to try to get a new fuse, but I am not too sure it will do anything.[/quote] It may cause further damage. Take the amp to a techie.

[quote name='rmorris' post='559640' date='Aug 3 2009, 03:54 PM']I'm obviously late to hear about the 'AccuSwitch Debacle" (sp?) Would anybody be so kind as to post a link or whatever so I can catch up on that. Sounds like marketing hype over technical reality ? (surely not :-)[/quote]It claimed to allow switching from 8 to 4 ohm impedance. It consisted of a capacitor, switched in and out of series with one woofer of a parallel pair. When in circuit a DCR measurement would be twice that of when it was bypassed, since the capacitor wouldn't pass DC to the second driver. When an actual impedance sweep was done there was no difference, of course. There are only two possibilities for the origin of the circuit. The first is that the A-G engineering staff did not know the difference between DC resistance and AC impedance. The second is that they knew and tried to pull a fast one. Neither explanation is excusable. A-G never came up with a plausible explanation, the switch unceremoniously disappeared from their cabs and literature. They continue to make SPL claims that defy the laws of physics in this universe and at least two more that we know of.

[quote name='dood' post='559156' date='Aug 3 2009, 08:03 AM']Yes, I am interested in giving one of Alex's monsters a good once over! - I'm interested in your comments. I have seen that it has been suggested the cab volume for the 15" isn't big enough in the 'El Whappo' but what other 'issues' have been noted with the design? Out of interest, has anyone published any testing to support findings? Really, I'm just interested, being everso slightly geeky. There seems to be a lot of support for the cabs, I'm certainly thinking they are no worse than 90% of cabs on the market? - I'd like to know ![/quote] Noted technical deficiencies from various sources include, but are not limited to, poor crossover design, no crossovers at all, poor cabinet damping, tweeters horizontally mounted, and claimed response that verges on the ridiculous. No, let me amend that, they are ridiculous. The AccuSwitch debacle could only happen if either the designers at A-G lack even the most rudimentary knowledge of acoustical engineering or the company embraces fraudulent marketing practices, neither option being particularlry palatable. A-G does for the most part sound better than 90% of the cabs on that market, but frankly, that's not a very high bar to clear. As for testing, there are no sources that test bass cabs using the standards laid forth by the Audio Engineering Society, ie., measured half-space anechoic on-axis and off-axis. There are cabs out there which are far better engineered at a much lower cost. Barefaced is one of them.

[quote name='Balcro' post='558499' date='Aug 2 2009, 09:22 AM']The excursion of the front speaker cones will "start & stop" more quickly than conventionally loaded speakers. In theory this should mean less speaker cone break-up and distortion. Balcro.[/quote]The only difference between an isobaric and standard alignment is the net cabinet volume required for the same response. That made it a fairly attractive proposition for Hi-Fi forty years ago, when driver and amplifier technology was not what it is today, and 16 cubic foot and larger cabinets weren't at all unusual. Using a second driver to get cabinet size down to a WAF was of some merit. The downside to isobaric is that the net output is still the same as can be realized with only one driver, and with the far smaller cabinet sizes required by modern drivers the net volume savings don't amount to much, certainly not enough to justify the added cost compared to a single driver cab of the same response and output capacity. In laymen's terms, why pay for a 2x10 that sounds like a 1x10?

A-G getting caught with their pants down over the Accu-Switch was the tip of the iceberg. It brought to light that, while better engineered than the average bass cab, they aren't what they're cracked up to be, and certainly not worth the price of admission. On you side of the pond Alex's offerings are a far better option for a lot less Sterling.

[quote name='Musicman20' post='552604' date='Jul 27 2009, 08:36 AM']I had that annoying ‘buzzing’ whenever I took my hands off the string etc.[/quote]That's normal. With high impedance pickups you must be touching either the bridge or the strings for high frequency noise to be shunted.

[quote name='bassmansky' post='551169' date='Jul 25 2009, 10:31 AM']cheers could try that,although the tape isnt doing a bad job![/quote] Eventually the adhesive will dry out and fail. Use the tissue PVA trick, applied on both the inside and outside of the cone. Silkscreen fabric also works well.

[quote name='coully' post='549148' date='Jul 23 2009, 11:51 AM']Are there pre-amps or amps which support this kind of approach?[/quote]There are, but there aren't any speakers from electric bass cab manufacturers that support this approach, so your options are to use PA gear or build your own.

[quote name='Changles' post='548673' date='Jul 23 2009, 06:02 AM']so i've got a hartke lh 500 going through the errr hydrive 115, great half stack, really love the sound i'm getting out of it, but there is a hiss, and i want to get rid of it in time for recording, which is this saturday[/quote]Most studios will take a DI only if they have a lack of available channels, using the amp only as a monitor. If they've got the channels they may mic the cab onto a spare. Don't count on your 'signature tone' ending up in the final mix. Even The Ox couldn't get his tone onto the wax.

[quote name='SS73' post='548355' date='Jul 22 2009, 05:38 PM']I did use an Ampeg 810 from about 72, it had all the original Jenson drivers and was superb for a couple of years then i had to replace a few and opted for the trace 32 ohm 80w, it just never sounded the same after. Now i see the original Jensons fetch serious money, ironically i have an 810 trace cab now, loved that SVT 810.[/quote] SVTs never used Jensens. The first models were loaded with CTS. In the early 70's an engineer from CTS started Eminence, and one of his first projects was to clone the CTS driver and get the Ampeg contract. Over the decades the Eminence driver has gone through a number of changes, morphing from what was originally a guitar driver to one designed for bass, which explains the changes in tone over the last 40 years. There are a few sources for replacements, including Ampeg, Weber, Jensen and Electro-Harmonix. The problem lies in knowing which will come closest to the tone of any particular vintage SVT, so most owners choose to do a recone rather than replacement.