Bill Fitzmaurice

[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.

[quote name='ray_6ao7' post='547467' date='Jul 22 2009, 07:26 AM']looking at the warwick site it says they're celestion?[/quote] Insufficient data. You need to know the exact driver model, and have all the T/S specs for it, to know whether changing drivers would be of any benefit. It wouldn't be the least bit surprising if Warwick is unaware of the specs on the drivers they use, and if they are aware chances are they won't tell you. Your best bet is to take the bad driver out of the cab, identify it, and have whomever did manufacture it provide the specs. As far as what I'd use it would be the Eminence Basslite S2010, which is one of the least expensive neo tens but has low frequency output capability equal to anything in the Celestion line. It only has a 150 watt thermal rating, but with eight of them that's of no consequence.

[quote name='ray_6ao7' post='546783' date='Jul 21 2009, 12:50 PM']Hey bill, what would would you recommend?[/quote]That depends on what's in there now.

[quote name='ray_6ao7' post='546626' date='Jul 21 2009, 10:54 AM']Hey Alex one speaker's blown recently so i need to replace that anyway and i've been toying around with the idea of trying to get something that has a really nice clear,punchy but deep tone aswell...just thinking it'll probably be cheaper than buying a new cab [/quote] Changing drivers might be of benefit if the new ones are better than the originals, but that requires knowing what the specs on the originals are. FWIW IMO the BL10-200x is poorly suited for electric bass, the BN10-300S totally unsuitable. Neither is capable of delivering deep tone.

[quote name='Protium' post='540590' date='Jul 14 2009, 01:47 PM']Bit harsh. I suppose all your cabs were perfect first time?[/quote] Of course not. But before building my first cab I spent a month in my college library researching how speakers work, and the first few cabs I built were pre-existing designs from acknowledged experts in the field. So, while not perfect by any means, they still worked better than off the shelf. The questions being posed by the OP may seem innocuous enough to the average reader, but they're akin to going to a DIY aircraft forum and asking 'why do I need a wing?'.

[quote name='Boneless' post='540513' date='Jul 14 2009, 12:28 PM']I actually don't know WHY vertical alignment is better[/quote]Which goes to why everyone who does know how speakers work in this and other forums have told you that you should not be trying to design your own cab.

The simple physics of bass reproduction demand that if you're going to keep up with guitars driven to full volume you need four times the speaker complement that they have. So the options are they turn down or you get a bigger rig.

[quote name='Boneless' post='540430' date='Jul 14 2009, 11:12 AM']Many boxes have a similar alignment, so I guess it can't be too bad[/quote] Yes, it can be too bad. The basic design parameters of most commercial cabs are set forth by marketing departments, based upon what they think will sell, and that's almost always a matter of looking 'right'. But what's most pleasing to the eye is not what's most pleasing to the ear. The number one reason for building one's own cab is the ability to not have to settle for what some marketing department head who probably doesn't even play bass thinks will sell based on looks. Your reasoning for not doing vertical drivers is the same as theirs, and is intrinsically flawed. [quote]I'd actually rely on the woofers for true midrange (and, according to the charts, I should have plenty of it)[/quote]The charts aren't worth squat, because they show axial response. whereas 30 degree and 45 degree off-axis is what counts.

[quote]what does this mean?[/quote]That you haven't read the manual?

[quote name='Musky' post='532898' date='Jul 5 2009, 07:24 AM']Unless you're playing dub you don't want the LF version of the 3015 as it doesn't provide any decent output in the upper mids.[/quote] The 3015 and 3015LF have the same useful off-axis high frequency limit, so the axial midrange response isn't why you'd choose the one over the other. The 3015 is the better choice with a small amp, less than 250 watts, for its higher sensitivity. The 3015LF will put out more low end, but only if you have a large enough amp driving it. As is the case with all fifteens you can only get a good off-axis midrange response by crossing to a midrange driver at 1kHz or less.

[quote name='Merton' post='532753' date='Jul 5 2009, 03:32 AM']Good work Stevie! Like the investigative journalism Very interesting reading, makes me glad I didn't get the Mini15s I was looking at earlier this year [/quote] Don't be hard on Ashdown, most lower priced, and more than a few higher priced, combos and separates employ drivers with similar specs. As for a midbass bump, and corresponding lack of low end, that same response characteristic can be found in more than a few high end cabs, Schroeder and Eden among them. Not because they use cheap drivers, but because it makes the cab seem louder. Look at an Equal Loudness Curve to see why.

[quote name='Pookus' post='532674' date='Jul 4 2009, 05:29 PM']I am about to sell my Ashdown ABM900 head and 810 cab as I have left the band and want to do other things musically and don't need such a massive rig.[/quote] Dump the speaker, keep the head. Get a 2x10 for now, if you ever get back into it, and you will, add more speakerage.

[quote name='bumnote' post='532651' date='Jul 4 2009, 04:40 PM']I understand that a company might fit the cheapest speaker it can get away with, but why not port it properly, surely that costs nothing[/quote]Heard the one about a silk purse and a sow's ear? You can't use a sub-standard driver with a good result no matter what the box tuning. For that matter a driver with a Qts of .62 has no business being in a small ported enclosure in the fist place. It would work reasonably well in a sealed cab of some 15 cubic feet.

[quote name='Bassman Rich' post='532426' date='Jul 4 2009, 08:38 AM']Or is the cab too small to handle that type of speaker.[/quote] It's not too small to handle any fifteen. However, the smaller the cab the less low end it's capable of producing. [quote]at 8 ohms that should cut down the power from the amp (500 watt at 4 ohms) to under what the speaker can handle.[/quote] That's immaterial. Bottom line, if you want high output at low frequencies you won't get it from too small a cab. Before making an investment in a driver that probably won't cure your problems consider buying a well engineered cab that will.

[quote name='Bero' post='528955' date='Jun 30 2009, 01:38 PM']Whats the difference between a cabinet giving output power as ??? watts rms then ??? watts program. The RMS is always lower than the program, which should i take as the output power so that i dont get the wrong cab for my amp[/quote] RMS is what engineering departments use, for the purpose of technical accuracy. Peak, program, peak program, music power, peak music power and all that rot is what marketing departments use, for the purpose of generating sales.