Bill Fitzmaurice

[quote name='Oxblood' post='18912' date='Jun 16 2007, 03:24 PM']I was thinking of things like organ pipes and suchlike, but I suppose the natural resonance of a very short, very fat cylinder like this would be virtually subsonic.[/quote] Their resonance is related to their length, not their shape, and is proportional to their length. A short pipe will have a high resonant frequency.

[quote name='Oxblood' post='18880' date='Jun 16 2007, 01:27 PM']something instinctively tells me that a cylindrical enclosure is bound to have a very strong resonance at one frequency, causing it to be something of a booming one-note samba.[/quote] The opposite is actually the case, round structures are highly non-resonant and have a far higher strength to weight ratio than flat panel structures. But aside from that all the other shortcomings of the design as pointed out by Alex et all are spot on.

[quote name='alexclaber' post='18563' date='Jun 15 2007, 04:22 PM']Obviously a well designed cab? I don't know how you come to that conclusion! Looks like a bog standard under-braced, under-insulated box which is too small for the woofers to operate efficiently, has a speaker arrangement that causes poor off-axis response, has too small a horn tweeter to cross over well to the woofers and to cap it all the drivers don't even match. However, apart from the latter point, that would accurately describe the majority of bass cabs on the market... Impressive name though! Alex[/quote] +1. If you took a course in audio engineering the typical 4x/tweeter configuration would be the example on the day they discussed 'How not to build a speaker'. It undoubtably sounds good in comparison to others of the same ilk, but the available room for improvement is vast. [quote]I'm really tempted to just wack out the Neo's and put them into an Omni 210[/quote] Aren't they 12s? Could go into one of these: [url="http://billfitzmaurice.com/phpBB2/viewtopic.php?t=3058"]http://billfitzmaurice.com/phpBB2/viewtopic.php?t=3058[/url]

[quote name='alexclaber' post='16474' date='Jun 12 2007, 03:06 PM']The cheapest and usually worst sounding is the piezo tweeter - Alex[/quote] When properly employed piezos work better than dynamic compression drivers. The problem with piezos is they are the least expensive tweeters available, and that makes them the tweeter of choice in inexpensive poorly engineered speakers. I switched to piezos for good when I found that a dozen of them, at $2 each, worked better than my $275 JBL 2426 driver coupled to a $180 JBL 2370 horn.

[quote name='Muppet' post='15888' date='Jun 11 2007, 03:51 PM']I take your point entirely but I wasn't suggesting a single 12" cab, merely a single 4ohm cab. The number of speakers in the cabinet is up to Rumble.[/quote] Either way it [horse and cart]s out with more than 50 watts per driver, so it can [horse and cart] out as a 4 ohm load or it can [horse and cart] out as an 8 ohm load but the stink is the same. My point is that far too many blokes shovel it against the tide going for as low a load impedance as possible thinking that 'getting all the watts out of my amp' will result in louder output, when the vast majority of the time it won't. OTOH, the vast majority of the time adding another speaker will give higher output. If you want to play loud and do it with one twelve take up guitar. If you want your bass to smack a room like Attila sacking Rome make two trips to the curb. Even better, three.

[quote name='Muppet' post='15631' date='Jun 11 2007, 10:06 AM']Get a 4 ohm cab. Less to carry and you use the full power of your amp.[/quote] A common notion, but a flawed one. The single most limiting factor in volume achieved is the driver's displacement capability. The average 12 is displacement limited to about 50 watts in the low frequencies, anything more than that only leads to farting out at the least, blown drivers at worst. If it's not loud enough there is no replacement for displacement.

[quote name='BOD2' post='8174' date='May 28 2007, 12:07 PM']I think the problem with paint stripper is that it doesn't really work. A "poly" finish is very tough and most paint strippers struggle to remove it. Then it's also layered so you get one layer off and have to do the same fo rthe next layer...and so on. Then you end up having to sand it down to finish off anyway.[/quote] You may be sadly disappointed if you sand the finish off to find that underneath the body is junk wood, quite likely glued up from smaller pieces. Leo Fender initiated the practice of using a natural finish on the best wood, sunburst on the middling and paint on the worst, no reason to think that's changed.

[quote name='The Burpster' post='12539' date='Jun 5 2007, 10:01 AM']B, The bridge was one of the first things I did, as it was loose! It has a lovely big fat connection to earth....... I am more and more resigning myself to the fact that its a [u]"they all do that, sir"[/u] and that Fenders are just not in the same league as PRS...... In its defence it does sound wonderful in passive mode so it may just have to stay there......[/quote] Single coils do all do that, always have, but if your bridge is grounded the hum should disappear when you touch your strings. As that's generally a prerequisite to playing the hum should only occur when you're at rest not touching the strings, and a noise gate will stop even that if it bothers.

[quote name='MoJ' post='13733' date='Jun 7 2007, 01:45 PM']I had channel one on the crossover marked as low, then channel one on the power amp as low, and the appropriate speakon connection on the cab (if it were th O15) labelled? Would make things clearer. Just a thought Thanks for all your advice though Bill, most helpful! Andy[/quote]All well and good provided you never muck it up, and if you don't you're a better man than I. Better to use a system that can't be hooked up wrong even if you try.

[quote name='MoJ' post='13291' date='Jun 6 2007, 03:51 PM']the wiring must be intergrated at the cab end with the -1 from the lows and -2 from the highs (or whichever way it is) going to ground and then the two + connections feeding the drivers?[/quote] The way it's done in pro-sound PA is to take the amp outputs to a separate jack panel on the rack for the Speakons that actually connect to the cabs via 4 or more conductor cables. Bad idea to use two sets of jacks on the cab both wired 1+1- to the same config on the amp via two cables, as a mix up will give you toasted MF/HF drivers in a literal flash.

[quote name='alexclaber' post='13229' date='Jun 6 2007, 02:06 PM']I'd leave it as it is - no 15" I've modelled in that size is any good and although it may only be rated at 100W it'll handle much larger amps. Listen and you'll hear when it isn't happy. If you simply have to do something, try a DeltaLite 2510-II - that's not a bad volume for a 10" and add a port to tune it to 45Hz. I do wonder though how much this HH cab weighs - my experience of them is that if it's well made it's also heavy which makes neo drivers a bit pointless. Alex[/quote] Chances are along with the low power rating is a low xmax, and you won't get much out of it. As to what to do with it I agree with Alex. A fifteen in 45l won't work as well as a ten.

[quote name='MoJ' post='13104' date='Jun 6 2007, 11:13 AM']Ive just looked at the online manual for a particular power amp (Peavey PV2600) and it says that unless in bridge mode, the speakons connections are arranged 1+ and 2+ for the outs, and 1- and 2- are the grounds. Is this still what you were getting at? Thanks Andy[/quote] That's normal for a stereo amp, where you'd have separate cables to separate speakers. To run a single cable to a bi-amped speaker you'd make up a dedicated cord with two plugs at the amp end. [quote]but as I understand low B on bass guitars is someting like 30 Hz. Is there someting Im missing? I gather that the human ear doesnt always need the fundamental to know the note, but surely having the fundamental and being able to reproduce it clearly is a good thing? I know that there must be something Im missing.[/quote] You wouldn't want a cab that runs flat to 30 Hz. The bulk of sonic content, and power demand, for the lower notes lies in their 2nd and 3rd harmonics, 60-100 Hz. Fundamentals only exceed the harmonics in strength once the string length is at least 1/4 wavelength. With a 34" scale bass that's from just about 100 Hz.

[quote name='MoJ' post='12865' date='Jun 6 2007, 04:26 AM']Good to know Bill. Of course buying seperates opens the options up some what. Does the O15 give a pretty natural sound bi-amped, if its all in one cab and with 3 drivers?[/quote] As I noted above, the main reason why bi-amping generally doesn't work well when using two commercial cabs is that those cabs aren't optimized for narrow bandwidth operation. It's a very different story when using two cabs that are bandwidth restricted, or a single cab that has multiple drivers that are bandwidth restricted.

[quote name='MoJ' post='12780' date='Jun 5 2007, 07:18 PM']So Im guessing Bill, that with your designs (if only the O15), bi-amping (of sorts) is something you feel is a viable option for bass guitar? Andy[/quote] Definetely. I don't make a big deal about it because bi-amping bass heads are so rare, but nearly all of my designs are bi-amp friendly.

[quote name='MoJ' post='12736' date='Jun 5 2007, 06:03 PM']Well,this at least tells me that its possible to do with your designs Bill. On the O15, I would assume then that 2 speakon connectors would be put on the back of the cab, and thus connected to the different speakers internally? And the HF horn,would that be connected to the same speakon as the mid driver?[/quote] The usual method employs a 4 pole speakon, with poles 1+ 1- for lows, 2+ 2- for highs, a single cable/jack. For electric bass a dynamic tweeter is often too sensitive, so an option is a pair of piezo tweets instead. This lowers driver cost considerably, and eliminates the need for any passive crossover at all in a bi-amp rig, as the mid and tweeters can be simply parallel wired.

[quote name='MoJ' post='12657' date='Jun 5 2007, 02:58 PM']If its any help Bill, I play 4 string tuned down to low B so I was swinging toward the omni 15 for its lf (correct abbreviation?) and I know that that has internal 3 way crossover in it for the differing speakers. Would a Titan and Omni 10 bi-amped be feasible?[/quote] The O15 can easily be bi-amped, and doing so eliminates a lot of costly and from what I understand hard to find in the UK crossover components. T39 and O10 can go either way as well, and again, bi-amping would save a lot on the crossover parts. I'd only go with an O10.5 with a T39, two tens aren't necessary.

[quote name='MoJ' post='12132' date='Jun 4 2007, 05:44 PM']Does it make a difference Id be using say a 2 x10 and 1 x 15 of commercial cabs? Thanks Andy[/quote] All the difference in the world. Bi-amping (or tri or quad for that matter) is de reguer in the upper end PA genre, where speakers are designed to work with high efficiency, in terms of both SPL and pack space, over a relatively small bandwidth, with no overlapping coverage. That's pretty much the opposite of how most bass cabs are designed, so the advantage of bi-amping with typcal electric bass cabs is greatly reduced.

[quote name='pete.young' post='12164' date='Jun 4 2007, 06:10 PM']So in order to get the optimum bass response, you need a cabinet volume equivalent to the VAS ? It can't be that simple, surely.[/quote] It's not, and stop calling me Shirley. For instance, a Beta 10 with a Vas of 82l works best in a 156l Vb. But 'best' is to a 38Hz f3, which is far lower than electric bass requires. A perfectly adequate 55 Hz f3 can be obtained with only 60l. The bad news is that most manufacturers will use the Beta 10, or the equivalent thereof, in only 30l, so not only is f3 up above 60 Hz but there's also a response hump around 140Hz that results in a boomy tone.

The Basslite Vas is very large and makes the driver one of the least desireable of the Eminence neo line. The Deltalite II 2515 and Kappalite 3015 are far superior.

[quote name='OldGit' post='10987' date='Jun 2 2007, 07:11 AM']So I'm going to email Marco and ask him directly - hey why not.[/quote] It is a fault, one that wouldn't get past FCC regulations this side of the pond, I'm sure you've got a bevy of similar bureaucrats on your side who'd be similarly upset.

[quote name='dave_bass5' post='11013' date='Jun 2 2007, 08:43 AM']Thanks guys yeah, the matt idea is a good one. ill try and track some down.[/quote] Try sellers of power tools. There are mats made to hold wood stationary atop a bench whilst being sanded or routed.

[quote name='dood' post='10478' date='Jun 1 2007, 07:45 AM']I've not heard any stories of the Behri' cabs 'blowing up' or anything.[/quote] I have, many times. Behringer electronics tend to be quite good, but they cut corners on everything mechanical, which includes switches, jacks, pots, and drivers.

[quote name='BOD2' post='7039' date='May 26 2007, 05:56 AM']Can you connect both to the same wall socket to see if this eliminates the problem first ?[/quote] Even then the ground loop may persist, as there will still be two ground paths connecting the devices. Transformer isolation is the best bet for a cure.