Bill Fitzmaurice

[quote name='Moos3h' timestamp='1321973822' post='1444975'] 2mm Xmax? Isn't that practically useless then? [/quote]If you want a highly compressed bottom thin tone or your only running 30 watts I guess it's OK. The BN15 400X is good at 4mm, though the .59 Qts of both it and the BL15 400 is a bit dodgy,

[quote name='alanbass1' timestamp='1321950384' post='1444621'] Is this a real bargain at £82 [/quote]Have you modeled it ? With only 2mm xmax I'm not sure it would be a 'bargain' at any price. The BL15-400 is infinitely better.

[quote name='NJE' timestamp='1321951334' post='1444642'] drummer/engineer [/quote]Oh, now I see where the problem lies.

[quote name='NJE' timestamp='1321872671' post='1443810'] The issue basically was that the front of house sound from my MarkBass was shocking and I put this down to the fact that the DI is only post EQ and the EQ was set up for me onstage. [/quote]Moot. The sound through the PA will be totally different than that on stage whether the DI is pre or post, because PA speakers are relatively flat in response, while bass speakers are anything but. The soundman should have had no trouble dealing with that, assuming the console had EQ on every channel strip. All he had to do was cut the lows and highs and boost the mids, the same as what your speaker does, to compensate for the EQ added to the signal. If he was sent a non-EQ'd signal he'd still have had to EQ the channel to get the PA feed to sound the same, or at least reasonably close, to the stage sound.

[quote name='51m0n' timestamp='1320450583' post='1427195'] You havent seen how small his back yard was [/quote] Road trip. Go to the nearest open field, all the required gear can be battery powered, including amplifier. [quote]Can't you just map the frequency response of a room? Not exactly simple but it's not rocket science either, just time consuming. Then it's a constant for all future tests? [/quote]In theory yes, but practically speaking, no. To measure in room at the required distances would be a sonic nightmare. There are methods to measure near field in room, but I don't place much faith in them myself.

[quote name='51m0n' timestamp='1320423838' post='1426762'] Yeah true, I've had long chats with Alex about the lengths he has to go to when measuring his cabs to get some idea of their frequency response - not a trivial undertaking at all! [/quote] It's actually easy if you have the right gear, and an open space to do the job. You measure ground plane, the mic literally an inch off the ground, for a half-space result below the baffle step frequency. Then you put the cab on its back and suspend the mic above it to get a half-space result above the baffle step. Splice the two together and you're done. If you want to do off-axis you do that with the cab on its back only, as below the baffle step axial and off-axis are the same. The gear used to be silly expensive, but today the software is free, and the hardware is less than a hundred dollars here. You can do the entire job, including off-axis plots, in about fifteen minutes.

[quote name='51m0n' timestamp='1320418058' post='1426658'] If so is it not possible that a combination of phase and off axis rejection from the mic would cause the mic to be significantly less bassy when micing from a couple of inches off the cone? Especially a cone a long way from the port? [/quote]Anything's possible, as every scenario is different. That's why definitive cab measurements are made outdoors (assuming you don't have an anechoic chamber handy) with the mic at least two meters, preferably more, from the cab.

[quote name='51m0n' timestamp='1320416219' post='1426620'] I'd beg to differ here Bill. If you close mic a couple of inches off the speaker you get none of the benfit of the cab port producing the low end. So by close micing you tend to take at least some aspect of the cab out of the equation as well as the room. [/quote] At a couple of inches off the driver the difference would be minimal; remember that port output is omni-directional. And there's also baffle proximity effect, which enhances the low end. True close micing to separate the driver and port outputs is done from more like a half-inch away.

[quote name='211dave112' timestamp='1320391937' post='1426146'] Is the sound that you get the sound of your cab or, as you're mic'ing the speaker, is it the sound of the speaker? [/quote]The two are inseparable. The point of close micing is to take the room out of the equation.

[quote name='Jamesemt' timestamp='1320240654' post='1424150'] I've currently got a Shuttle 3 10 with an ampeg mini SVT as an extension cab. That's 300w. [/quote]Get another Mini, stack them vertically. It's not about watts, it's about displacement and sensitivity. Two Minis is a pretty formidable rig, they just won't go real low due to the small size.

[quote name='pbaleiras' timestamp='1320321114' post='1425226'] Ok.... So what do you suggest?!? not forget that the orange has 500Wrms, And i Think should not link a cabinet with less power...am i right?!? [/quote] The power rating means almost nothing. What limits output is driver displacement; see the Barefaced site for an explanation of what displacement is. While an isobaric has the power rating of two drivers it has the displacement of only one, in this case no more than 300cc.

[quote name='citymariner' timestamp='1319972988' post='1420605'] I've just noticed on the 'What's in your rack thread' that someone has mentioned NOT to use a surge protector before the amp as it limits current drain. [/quote]It does not. A so-called 'power conditioner' can, and that's why AFAIK not one manufacturer recommends them, while many recommend against their use. But what 'power conditioner' means has been corrupted; most devices with that label today are actually just surge protected and possibly noise filtered power strips. Price is the clue, and if it costs more than 30 quid or so you don't need it. For that amount or less it's a power strip and won't bother your amp if rated for adequate current draw.

[quote name='Mr. Foxen' timestamp='1319988050' post='1420866'] Has anyone actually tried putting beefier caps into a SS amp, or is there more to it than that? [/quote] Much more. With a standard power supply too much capacitance can lead to a blown transformer, as the initial current rush on power up is determined by capacity. Enough capacitance can appear as a dead short to the transformer until they charge a bit. I'm not terribly familiar with switching supplies, but I suspect the same is true of them.

[quote name='JohnFitzgerald' timestamp='1319968072' post='1420519'] Is one watt the same as another watt ? I know there's more to it than that, but what are your findings ? [/quote] A watt is a watt. Reserve current capacity and headroom is something else entirely. Old 'big iron' amps have high capacity power supplies, most Class D use switching supplies that don't have a lot of storage capacity. There's still much to be said for those fat bottom girls. Of course there arises the question of when is a watt not a watt, and that involves marketing trickery, if not downright deception.

[quote name='bass_by_name' timestamp='1319631490' post='1416608'] I have often wondered about this. Lots of cabs have name badges covering the ports and/or drivers. [/quote] Badges should not cover ports, they will upset the tuning of the cab. I wouldn't cover drivers with them either, though it's less problematic than ports.

[quote name='alexclaber' timestamp='1319203119' post='1411247'] Regarding the thermal thing Bill, one would hope that if a cab is rated at 250W its woofers have endured the usual 1000W peak 250W average AES test for two hours. Surely it would have to be a really crazily loud and long non-stop gig for the RH450 to exceed those thermal challenges? [/quote] That test, as well as EIA 426a, is done with pink noise. The power density with a heavily compressed musical tone is far more stressful. I give builders maximum voltage specs for subwoofer cab/driver combinations, so that they may limit to that voltage to prevent going past xmax, not so much as to prevent mechanical damage but as to prevent long term heat build up. Eminence went through a nightmare situation with the LAB 12 driver and LabHorn, as telltale distortion when pushed beyond xmax couldn't be heard. Drivers dropped by the dozen, and almost all of them died from long term overheating even though they were seldom pushed past Pe. The problem was compounded by a driver chamber that was too small for adequate driver cooling, which was addressed with an aluminum chamber cover that doubled as a heat sink.

[quote name='alexclaber' timestamp='1319197712' post='1411121'] To address the specific problem, the real power output of the RH450 is ~130W into 8 ohms. The RS210 can handle 250W thermally so you can't overheat it. The woofers in the RS210 have small magnets (hence the low-ish weight for a ferrite thick-walled cab) and their sensitivity isn't that low so their maximum linear excursion must be low, thus I'd guess that the cab can handle somewhere around 100W before distortion/compression increases rapidly due to over-excursion (passing the mechanical limit) and you start to approach the failure point. As the RH450 only produces 130W into this load you're not going to be able to push the cab so hard that you reach the mechanical failure point (although you may hear some harmless distortion) so crank it to your heart's desires without fear! [/quote]I wouldn't be so sure. That amp seems to have a very high compression ratio, the source of the magic 'TC watts', so the power density will be higher than the actual voltage swing capacity would indicate. Short term that's not a problem, but between that and the heat retention of ferrite drivers long term heat build up could be a problem. Far more drivers suffer toasted coils from long term heat build up than short term overpowering. IMO if the OP has to consistently push the amp hard to get adequate output he could be looking at shortened driver lifespan, perhaps drastically shortened, so the higher sensitivity of adding a second cab would be in order.

[quote name='charic' timestamp='1319119073' post='1410160'] How is a power rating moot when the question at hand is can I turn my amp to full without breaking the cab? [/quote] I already told you. Go to the Barefaced site and read why displacement, not thermal power ratings, is what's pertinent.

[quote name='charic' timestamp='1318348882' post='1400988'] It says it'll handle up to 400 watts [/quote]Power ratings are moot. What matters is displacement. AFAIK only Barefaced reveals the displacement of their cabs. It's worth a look at Alex's site to learn what displacement is, why it matters, and ponder why every manufacturer doesn't provide it.

Chances are you'll have no warranty. Most manufacturers require that warranty claims be handled by the selling dealer, and even if not still a proof of purchase is required, one from your own country.

http://en.utrace.de/ Use this to trace the source ISP of email.

If it's not just a fuse or bad cable there's nothing you can do to fix it anyway. Check those and if no luck get it into the shop.

[quote name='Nodd' post='1371926' date='Sep 13 2011, 10:03 AM']Thank you Bill, amazingly they do work...for quite a while, advice gratefully received. Stevie, I will have a look at the Fane, need to check overall depth, thank you. All other comments gratefully received. Nodd[/quote]That Fane will give no better a result than the Eminence. They may not be twins, but they are very close cousins. If you're looking for a significant improvement you'd need an Fs in the vicinity of 80Hz or lower, and xmax of at least 4mm. That gets you mainly into the realm of hi-fi drivers, and then you sacrifice sensitivity. There may be some pricey drivers that are better, but there's the rub, they would be pricey.

[quote name='subdude' post='1370067' date='Sep 12 2011, 02:39 AM']i have a pre amp with 1/4" jack line out and an output impedande of 680 ohm that i want to connect to a power amp with XLR input and an input impedance of 20Kohms. do i need a DI box or can a simple adapter be used? thanks[/quote][url="http://www.rane.com/note110.html"]http://www.rane.com/note110.html[/url]

[quote name='fatback' post='1371580' date='Sep 13 2011, 06:03 AM']- is a bass sound omnidirectional from the cab when you're up close, like within 5 feet?[/quote]It's omnidirectional below roughly 200Hz at any distance.