Bill Fitzmaurice

[quote name='Helderius' timestamp='1472133508' post='3118777'] Yes, it is open back. [/quote]I'd suspect the speakers.

In that case it's not a microphonic tube. Is this an open back '59 Bassman reissue? Despite the Bassman name they're guitar amps, useful for bass only at very low volume.

The short answer is that you want to use your bass speaker as part of a hi-fi, and where both response and low frequency extension are concerned bass speakers are very low-fi. Use the right tool for the job, in this case a hi-fi powered sub.

[quote name='MoonBassAlpha' timestamp='1472042537' post='3117929'] That's not quite what I meant Bill, I meant the rear-facing speaker is also open to the air, just facing backwards, or even upwards or downwards. [/quote]Without a picture I can't be sure of what you mean, but on the face of it that's not an isobaric alignment.

Possibly a microphonic tube. To test turn the amp on with no instrument plugged in, volume halfway, gently tap each tube with a pencil. If you have a microphonic tube you'll hear it.

[quote name='MoonBassAlpha' timestamp='1471871112' post='3116532'] Could you run an isobaric cabinet with the speakers magnet to magnet, one facing forwards, one facing backwards, both emitting sound? [/quote]Technically they don't both emit sound. The area of only one cone is exposed to the air, so the maximum output with two drivers isobaric is the same as with one in a standard configuration. The only advantage is a halving of the Vas, but due to the space taken up by the second driver and the connecting plenum chamber the net cabinet size is not halved, while cost is greatly increased by using two drivers. That's why manufacturers in general have not jumped onto this particular band wagon.

[quote name='Twincam' timestamp='1471788894' post='3115857'] I'm using maths and a very simple port tuning program. [/quote]Why? I could see it to some extent if modeling software was a major investment, but as it's free I can't comprehend not using it.

The tuning is the same as with a standard cab. The modeling software will take into account that it's an isobaric alignment.

Having done studio work during that period my first hand experience was that studios dumped most of the valve gear because they didn't want to be perceived as having fallen behind the technology curve. This was during the same period when they were changing to 16 and more track tape decks and consoles that were designed for the studio, rather than broadcasting. There was a 'clean sweep' attitude, and to their later regret many a perfectly good baby ended up tossed out with the bath water.

[quote name='Beer of the Bass' timestamp='1470841717' post='3108873'] Will they, though? It seems there was a period of uncertainty from the mid 80's to some time into the 90's when US and western Europe stopped production, but if anything they seem to have undergone a resurgence since then. It's not just Russia and China either - JJ are successfully making them in Europe under all of the environmental restrictions that go with that. So I would be surprised if they disappear within my lifetime. [/quote]The only use for them is in amps. As demand for valve amps goes down prices on valve amps and valves will continue to rise, further reducing demand, further reducing production, further increasing price in a literal death spiral. That can only make vintage valve gear, or at least what will be vintage someday, appreciate in value. A comparison can be drawn to Fairchild valve compressors, the studio standard of the 60s and 70s. After SS took over the compressor market studios literally tossed Fairchilds into the trash bin. Now those which remain command the same price as a very nice car. For instance: http://www.analoguetube.com/#!Vintage-Fairchild-670-For-Sale-44000/c1czm/5576e3fc0cf2312d79783c31 I doubt that valve amps will appreciate that much, but one never knows. .

[quote name='M@23' timestamp='1470836822' post='3108832'] Really? They're not exactly hard to come by and seem to sell 2nd hand for the standard 60% (ish) of retail. [/quote]Wait 20 years, when valves have gone the way of the dodo.

Keep it, if only to hide it away and appreciate in value.

It won't go as loud down low as a driver with more xmax. The difference between a small vented cab and the Jack would lie in the midbass and low mids, where the horn of the Jack greatly increases sensitivity. If you want to get a lot more output down low you'd have to go to a longer xmax driver. A 3012HO, for instance, would have 6dB more output down low, the equivalent of two EVM. If it was me I'd sell the EVM, they do bring a good price from guitar players.

[quote name='MoonBassAlpha' timestamp='1470133430' post='3103429'] Would an EVM12L work well in a JackLite 12 Bill? [/quote]It will, about the same as with a 3012HO as far as response goes, although the 3.3mm xmax is less than optimal.

The DL15x was a later version of the EVM15B. A good driver, though weighty. Specs are Fs 42Hz, Qes .3, Qms 4.5, Vas 195L. xmax 4.1mm. Pe 400w. It would be fine in the Simplexx 15 or Jack/JackLite 15 cabs.

[quote name='Huge Hands' timestamp='1469775844' post='3100925'] What, bury him in a car park? [/quote]I was thinking of giving a headsman a bit of work, but the parking lot will do.

[quote name='Dan Dare' timestamp='1469715995' post='3100599'] Good for Bill. So much snake oil in cables, especially in wunnerful wold of hi-fi (where those with the most expensive set-ups usually have Van Gogh's ear for music). [/quote]Having lots of money doesn't necessarily equate to being highly intelligent. Take Donald Trump, for instance. Really, take him, please...put him in the Tower of London and do a Richard III number on him.

[quote name='goingdownslow' timestamp='1469546691' post='3099263'] were there 100w Eminence Delta speakers at one time? [/quote]No. The Delta line only came along perhaps 15 years ago. They've had very few changes since their introduction.

[quote name='waldemar' timestamp='1469478128' post='3098701'] Hmm, interesting stuff. I emailed a friend of mine earlier regarding some of this stuff - he's pretty seriously into his hi-fi, not just listening to, but building hi-end valve amps, collecting exotic paired valves etc. - even going as far as temporary structural modifications to his house to get his WE16A horns in... In short, a knowledgeable guy with a keen ear for detail who's not shy of spending a bob or two on his passion. He had this to say: [/quote]He's bought into it. Drank the kool-aid, we'd say here. What he says is true in an absolutely worst case scenario, such as using 200 foot long cables with valve amps, but if you did damping factor would be the least of your worries, as capacitance and inductance would create much more of a problem. It's kind of like skin effect, which as I recall Monster was the first to raise in their advertising. Skin effect is real. Engineers have to go to great lengths to minimize it in cabling for, for instance, radio transmission towers. What Monster, and others who employ it as a boogey-man to generate sales, don't say is that doesn't affect the audio frequency band width. Another cable expose: [url="http://www.verber.com/mark/ce/cables.html"]http://www.verber.co.../ce/cables.html[/url]

[quote name='discreet' timestamp='1469461355' post='3098489'] I read somewhere that it's not just about the power handling - thicker speaker cables allow for better damping. Whatever that is. [/quote]That would be damping factor, and it's not true: http://www.diyspeakers.net/Articles/Richard%20Pierce%20DAMPING%20FACTOR.pdf Damping factor is one of the oft-quoted reasons for the need for exotic/expensive wires. So is skin effect. On the face of it the crap spewed by cable crooks seems to be legitimate, if you have only a cursory understanding of the physics involved. Since few average people posses even cursory knowledge they get away with what's literally criminal. Interesting reading: http://www.roger-russell.com/wire/wire.htm http://www.avsforum.com/forum/91-audio-theory-setup-chat/2166017-monster-xp-versus-aluminum-foil-speaker-cable-test.html

[quote name='stingrayPete1977' timestamp='1469447950' post='3098322'] My 1.5mm melted in the speakon connector supplied by bass direct at the first gig [/quote]I'd blame that on a cheesy connector or a botched connector installation, not the wire gauge. 1.5mm wire can handle 14 amperes at full duty cycle with a resistive load. 600 watts into 4 ohms is 12 amperes. You'd only get that 12 amperes on a sporadic basis, if at all, as a speaker is not a resistive load. Throughout most of the speaker pass band the actual impedance will be far more than 4 ohms, so current will be far less than at 4 ohms. [quote]I thought I'd ask after noticing how prevalent the fat cables seem to be amongst fellow bassists[/quote]Probably trying to compensate for inadequate size elsewhere. Over gauged/overpriced/over hyped cables are the #1 rip off in audio, on both the amateur and professional level.

1.5mm is sufficient. If each cab is connected by its own cable to the amp it's considerably more than sufficient. You may go larger, but it won't work any better.

[quote name='obbm' timestamp='1469091544' post='3095599'] I've just had a look inside my Prodigy and the mains transformer is most definitely 220/230/240 only. There is no primary connection for 100/120 so it looks like they have different transformers for different markets. [/quote]I can't tell from the picture, but in any event there would be no primary connection for 110 versus 220. There would be dual sets of input wires to the transformer, allowing it to be wired like so:

Any decent techie would be able to tell if it has a dual primary winding on the power transformer. For that matter you could probably tell as well. Most amps do, rather than to have to use a different transformer for export models.

[quote name='Jus Lukin' timestamp='1468666274' post='3092487'] I'd read much about the de-coupling effects of casters and was left with no expectations either way, but once applied they made a big difference with boom-in-the-room, [/quote]FWIW casters will have no effect, unless they stand a foot or more high. That's because there's no such thing as mechanical coupling, and it takes that much distance from the floor to audibly impact acoustical coupling. OTOH adding damping to a under-damped or un-damped cab can have a major effect eliminating midbass boom.