Bill Fitzmaurice

[quote name='Big_Stu' timestamp='1344531622' post='1766123'] That used to be a hanging offence in "What Hi-fi" magazine. [/quote]I guess that would have made Paul Klipsch public enemy #1?

Unless you have a valve head that can't run at 8 ohms there's nothing to be gained by using a 4 ohm cab. That's not the case with the 400+.

[quote name='Jimelliottbassist' timestamp='1344526968' post='1766006'] Have you had any experience with eminence speakers beta or delta? [/quote]What matters is matching them to the cab and amp, using their T/S specs and a speaker modeling program to determine suitability.

[quote name='Jimelliottbassist' timestamp='1344380315' post='1763828'] Hi I'm thinking about changing the speakers in a mesa 4x10 cab from 8 to 4 ohm. [/quote]Don't bother. Unless your amp is seriously underpowered it won't go any louder, which I assume is the reason for wanting to change.

[quote name='jezzaboy' timestamp='1344164132' post='1760509'] Why don`t they just fit a speaker capable of running at 300w at 4 ohms? I guess there must be a sound reason for it? [/quote]If they used a 4 ohm driver you couldn't add an extension. As for the power issue, few fifteens are capable of making use of even 150w, irrespective of the thermal power rating, so you'd need at least two to make use of 300w anyway.

[quote name='xgsjx' timestamp='1344118987' post='1760188'] Anyone know if it works & if so, why don't more cab manufacturers do this? [/quote]It does work, on tweeters, and many manufacturers use bulb protection. It does not work with woofers, the current flow being far too high. The only sure protection for woofers is an active limiter.

[quote name='Lozz196' timestamp='1344107438' post='1759979'] No doubts about that. But it sounds ideal to me. The same sound coming from either side of the stage. [/quote]Above 100Hz or so that's perfectly OK, be it on stage or with the PA. Below 100Hz not so much, as explained here: http://www.prosoundweb.com/article/in_search_of_the_power_alley/

[quote name='vintage_ben' timestamp='1344029780' post='1759074'] And just to nit pick, I did specifiaclly say equivalent (I realise this wasn't original comparison). I.e if an established company decided to develop an SVT style 8x10 in 2012 - so not a Neo superlight thing, clearly quality comes at a price. So I'll stand by that one I think. [/quote]The design process for the original SVT was to build a box large enough to contain the drivers on the baffle and to adjust the depth to give a decent result without being overly large. A week, tops. To do so today using modeling software perhaps an hour to come up with the basic design, using CAD a few more hours to create the cut sheets. Things get complex when you use vented cabs and/or multiple drivers with a crossover, and then it's the crossover that takes all the time and effort. One of my commercial designs went through literally months of B testing until the manufacturer arrived at the combination of cab tuning frequency and crossover component choices that gave him the best result according to the testers. That does not occur with a simple one-way sealed box. Alex's 69er seems to be taking a long time to come to market, I suspect partly due to the complexity involved with his 2.5 alignment, which would take a lot of B testing to get it right. I expect it to be worth the wait. If I was going to do a cab of that sort that's how I'd do it, which I've mentioned more than a few times on various forums.

[quote name='Protium' timestamp='1344026748' post='1759012'] If you tip a 4x10 45 degrees the speakers will be even further apart horizontally [/quote]Quite right. Pardon my brain-fart. The reason they'll work better that way is that rather than having two vertical line sources there will be three, with the center to center distance between each less than that of the two in a normal position. But it still won't work nearly as well as a single vertical line.

[quote name='vintage_ben' timestamp='1344023180' post='1758944'] My hunch is that the Ampeg 8x10 was much more expensive to develop than a modern day equivalent. [/quote]The 'engineering' required to develop the SVT cab took perhaps a week. It's a sealed box, how difficult is that? Theile modeling was not being used at that point, having been developed only a few years before and was only known of in Australia until 1971. Drivers using Theile parameters didn't come along until a few years after that. The SVT drivers already existed, guitar drivers BTW, which were also used in some Fender guitar combos. They were chosen based solely on their 32 ohm impedance, allowing a simple parallel wiring harness that the assemblers would be less likely to screw up than a complicated series/parallel scheme. If some 32 ohm twelves had been readily available they likely would have been used instead and quite possibly tens would never have become the standard for electric bass. The SVT driver has changed over the years, but it remains an inexpensive stamped frame unit that costs Ampeg about $30 each. The neo drivers used by Barefaced, for instance, come in at least four times that.

[quote name='Mog' timestamp='1343905577' post='1757057'] This confuses me. Is the only thing that can cause this proximity to the stage floor or is it some new fangled physics I haven't heard about. [/quote]The physics of dispersion by a sound source were quantified in the 1930s. [quote]The thing is you don't want the bass to go everywhere on a controlled stage as it is a bugger to get rid off if it bleeds into other signals.[/quote]The low frequencies [i]always [/i]go everywhere. Below roughly 250Hz the radiation pattern of a typical bass cab is 360 degrees. Above that dispersion progressively narrows as the wavelengths become shorter. The wider the source the greater the disparity between low frequency and high frequency dispersion. That disparity is minimized by keeping the source as narrow as possible. Contrary to popular belief this is why midrange drivers are smaller than woofers, and tweeters are smaller than midranges. As the operating range of drivers goes higher in frequency the size of the drivers is reduced not for the purpose of extending the operating range of the driver higher in frequency but rather to counteract the narrowing of the system angle of radiation with increasing frequency. [quote]True - but Jacks don't produce a real arse-shattering sub-type bass, though.[/quote]Jacks produce at least as much low end as direct radiating cabs using the same drivers. Where they differ is that they produce stronger mids. And they're not rear-loaded horns, they're front loaded horns. [quote]Isn't it strange that if the sound man does manage to get a reasonable sound out front during a sound check how it suddenly changes to rubbish during the gig.[/quote]The room acoustics are totally different when the room is empty versus full with an audience. [quote]For instrument monitoring we just hear each other on stage as normal.[/quote]That's even more of a challenge than having uniform sound in the audience, as the cone shaped midrange and high frequency dispersion pattern is much smaller close to the amps. With a typical stage setup the mids and highs from amps can only be heard directly in front of them. Only by running the instuments through the monitors may what's heard on stage be as close as possible to what's heard out front. Since the low frequencies as noted are omni-directional there's no need to have them in the monitors, so the instrument feeds to the monitors should be high-passed.

[quote name='KingBollock' timestamp='1343857819' post='1756572'] Would tipping the cab up, so that it was in a more diamond style configuration, so one speaker above another and then one either side at middle height, help? [/quote]It would be better. Horizontal dispersion is inversely proportional to the width of the source. By making it narrower dispersion is widened. Of course this makes the head placement a bit of a task. BTW, the entire reason why drivers were placed horizontally in the first place was to accomodate a wide amp, first in combos, then in separates. No consideration was ever given to the dispersion issue because the amp designers weren't aware of it.

[quote name='BluRay' timestamp='1343847483' post='1756345'] This thread's taken a turn for the better [/quote]It should have ended at post #3. That's when the answer to the original question was given, most of what has been posted since has been silly catterwallering. Little wonder Alex seldom comes here any more. If one doesn't want the opinion of an expert in the field one should not ask the question to begin with. Unless they be trolling, of course.

[quote name='alexclaber' timestamp='1343814974' post='1755517'] I'd have thought I'd have already said enough in my columns and on our website to get my view across and hopefully increase people's understanding of acoustics. [/quote]Said thinking obviously falls into the wishful category.

[quote name='shizznit' timestamp='1343774579' post='1755208'] Dispersion is only a problem if you need your backline to fill a venue if you are not going through the FOH. [/quote]But most of us don't. By placing two tens side by side the midrange dispersion is less than that of a 1x15, or vertically aligned 2x15s. Tens naturally have the widest dispersion of the usual driver sizes, but only if kept in a vertical line. Want the tone and output of a 4x10 with wide dispersion so that the audience can hear them, and with the drivers high enough so that you can hear them? Stack two 2x10s vertically.

[quote name='Pbassred' timestamp='1343591996' post='1752517'] You might possibly want to check out the Eminence web site. [/quote]When you do spend time here: http://www.eminence.com/support/understanding-loudspeaker-data/ The only factor influenced by cone size alone is the dispersion angle. Where response is concerned there are tens that go lower than some fifteens, and fifteens that go higher than some tens, so to say that 'tens do this and fiteens do that' has no basis in fact. [quote]The benefit a 15 has over a 10 is that it moves more air (the surface area of cone is more)[/quote]The amount of air moved is determined by the driver displacement, not cone area. Some tens have more displacement than some fifteens, so how low/loud you want to go isn't a matter of cone size. .

[quote name='icastle' timestamp='1343584308' post='1752367'] Turn the scenario on it's head - if there was any real benefit in using a crossover in a bass cab then all the mid to high tier manufacturers would be fitting them, and they aren't... [/quote]The reason they don't is that the vast majority of players would not be willing to pay the added cost, lacking the understanding of how speakers work and therefore why a well designed and built cab is worth a lot more than a few drivers tossed into a box.

[quote name='Pbassred' timestamp='1343552150' post='1751885'] Surely you would want to use the 10" for Highs only and 15" for lows only Otherwise it would sound bad or be inefficient. [/quote]If the tens and fifteens used were optimized for highs versus lows this would be true. But they aren't. There's precious little difference in the response of electric bass tens through fifteens, and for that reason precious little benefit to mixing them, if any.

[quote name='Mr Fretbuzz' timestamp='1343069408' post='1744784'] I've kept that link thanks but all I've bought are shop cables so far... The last was a retro looking Fender Custom Shop cable in the smallest length I could find as I'm told that the smaller cable you can get away with the better the signal. One thing that I've been thinking about though is that i used to get gold plated connections for my tv surround/ play station etc.... Not seen any gold plated bass ones in the shops... How come as I thought you'd get a better signal etc with them ?.. [/quote]Cables should be kept as short as you need them because longer cables are extra cost and kit that you don't need. Gold plating doesn't corrode, but unless your installation is on a boat or in a beach house that's not a concern. Overpriced/overhyped cables are the number one ripoff in the world today, don't believe 1/10th of what you see in advertising for them.

[quote name='HotelEcho' timestamp='1343049091' post='1744242'] does anyone have any preferences for speaker cables from one manufacturer over any of the others? [/quote]Copper is copper. All you want to be sure of is adequate gauge, 16 will do for 1.5m, and the use of Neutrik connectors. Since Neutriks are more expensive than generic el-cheapos if they're employed it's a safe bet that the cable is also of decent quality. [quote]I'm slightly sceptical at spending £35 on a 1.5m lead [/quote]As you should be, for that length it's at least twice what you should spend.

[quote name='bigjohn' timestamp='1342973768' post='1743305'] Nowt wrong with the speakers. Cab belonged to my mates dad from new I believe and wasn't overworked. It's then spent some year being an occasional guitar cab / stored in a studio. [/quote]It's not a matter of anything beiong wrong with them, just the fact that 50 watt fifteens of that era generally were displacement limited to perhaps 30 watts before farting out. That's a mighty big box to haul about for such a small result.

To be gig worthy you'd need to replace the drivers, brace, port and line the cab. Otherwise it would be an oversized underperforming albeit cool looking curiousity. If you or a mate have the skills to do that it might be worth the hundred, much or all of which you could recoup selling the drivers to a collector.

[quote name='bremen' timestamp='1342705117' post='1739632'] You're telling me the spiltter transformer was invented in 1980? [/quote]I doubt that, but they would not have been common items in everyone's kit. True FOH consoles as we know them today were still few and far between even in 1980. Most of what was being used through the 70s for touring was studio gear, and most of that prior to 1975 was originally made for broadcast, not live sound. Even balanced mics using XLR connectors weren't standard until the mid 70s. They existed, but most PA mixers made prior to 1975 had unbalanced 1/4" inputs.

[quote name='bremen' timestamp='1342701437' post='1739544'] Seems an odd way of going about it. Why not just use one mic, one transformer, two mixers? [/quote]Easy to say that today, in the 70s not so much. Much of what we take for granted today didn't exist then. Keep in mind that in 1970 the Shure Vocal Master was state of the art.

[quote name='BRANCINI' timestamp='1342695420' post='1739386'] They always seemed to be two different mics, rather than two the same, probably a reason for that. [/quote]If the mics are not identical the technique won't work, so if that's the case the mics are being fed to two different consoles. That was done a lot in the 70s, using one console for the FOH and the other for the recording, as most consoles then didn't have the ability to do both simultaneously. [quote]with the mics, say, 5cm apart a bit of back-of-a-fag-packet maths says that they'll already be out-of-phase at around 3300Hz, [/quote]Not if the elements are on the same plane.