Bill Fitzmaurice

[quote name='Musky' post='629721' date='Oct 18 2009, 02:21 PM']Running the MAG 600 into a 4 ohm load, the amp will be capable of knocking out it's full 575 watts if you turn it up full. Which obviously you don't want to into a cab that can only handle 400 watts.[/quote]Of more significance is that most 400 watt cabs will take no more than 200 watts before farting out, so running a 4 ohm cab to 'get all my watts' is a wasted effort in the short run and the long run as well.

[quote name='GreeneKing' post='613372' date='Sep 30 2009, 05:31 PM']If the amp has a max output of 200 watts or thereabout into 4 ohm, and you add an extension cab in [b]series[/b] to increase the impedance seen by the amp then the output will fall.[/quote]If the extension cab is identical the sensitivity will remain the same, as the 3dB lost to the doubled impedance will be offset by the 3dB gained via mutual coupling. In all maximum SPL will probably go up, as the fifteens typically used in combos are displacement limited to only 50 watts or so. Running a combo at minimum impedance with the internal speaker is rare, but not unique; Eden Nemesis does so and also runs the extension speaker in series.

[quote name='krispn' post='629538' date='Oct 18 2009, 10:33 AM']Seen one of these on evilbay and was wondering would a 100 tube power amp be enough for a bass rig? and would it be clean enough? Thoughts?[/quote]It depends on the speakers. More drivers means higher sensitivity, so you need less power. 100 watts from a tube amp into an 8x10 would certainly handle most any venue. But not through a 1x or 2x, maybe through some 4x.

[quote name='Count Bassy' post='627478' date='Oct 15 2009, 06:44 PM']I've read through this thread and am still a bit confused. Am I right in thinking then that ported cabs should be lined and that sealed cabs should be 'stuffed'.[/quote] Not necessarily, sealed cabs only need to be stuffed when they're too small for the drivers within. But that situation probably applies to 99% of the sealed cabs made. For instance, the SVT ten inch drivers are happiest in 6 cubic feet...each. [quote]I've suddenly become interseted as I've just opened up my Marshall combo (to fix an amp problem) and notice that the (sealed) cab part has no lining or stuffing of any sort.[/quote]I'd call that unbelievable if I didn't know better. Line or stuff it, based on ported or sealed.

[quote name='derrenleepoole' post='624379' date='Oct 12 2009, 03:34 PM']Well, my SF ran VERY hot -[/quote] So did mine, due to a design flaw. The heavy aluminum external chassis is not ribbed, to act as a heat sink, but is solid, retaining heat. It also doubles the weight of the amp. I removed that, mounted the amp in a rack, added a fan and it runs cool to the touch. You'll note that the LG has abandoned the aluminum crap and added a fan.

[quote name='derrenleepoole' post='624238' date='Oct 12 2009, 01:34 PM']I presume this has been covered then? Did a search but nothing came up - or I missed a thread? If there is a link to a topic on this, could you post it? Cheers...[/quote] You can use them with any head. Their only claim to fame was the stereo wiring that allowed each half of the driver complement to be hooked up to each of the two power amps of the SF head. BTW, I have a SF and I find it not the least bit underpowered, and that's into one 8 ohm cab, albeit one of much higher sensitivity than off the shelf. I can't see a LG not being able to push a SF cab to full output.

[quote name='alexclaber' post='623937' date='Oct 12 2009, 08:28 AM']Interesting. If the increase in compliance was due to a lowering of the speed of sound one would expect this to be consistent with larger boxes - so does this suggest that a larger box is inherently more isothermal due to the greater heat capacity of the air within it and the greater radiating area of the enclosure? I presume overstuffing is counterproductive because the increase in compliance due to heat absorbtion is offset by the decrease in actual net volume. Alex[/quote]The changes offered by stuffing have nothing to do with either lowering the speed of sound or heat. They're the result of the alteration of system impedance by the higher mass load of a stuffed rear chamber versus unstuffed. And that's why the response of a larger box is impossible, because stuffing is a passive component, and passive components can never add energy, they can only consume or reallocate it. Depending on system Q stuffing can reduce a midbass peak with little alteration otherwise to broadband response, and it can lower system Fsc while lowering broadband sensitivity. But what it cannot do is lower system Fsc while maintaining or even increasing broadband sensitivity, wheras a larger box can do just that. As to the heat increase exhibited in a stuffed box, there are two sources. One is the higher coefficient of friction offered by stuffing versus air to the rear wave, and where there's friction there's heat. The other is the insulation value of the stuffing, which retains not only the heat created by the stuffing but that of the driver motor. Measuring a higher temperature within a stuffed versus unstuffed box isn't the least bit unexpected, it would be inexplicable not to.

That's a lot of knobs for an older bass rig, be sure it's not guitar.

[quote name='tom1946' post='623105' date='Oct 11 2009, 09:14 AM']Are there any quietly powerful amps out there with maybe an ability to just flick a switch to silently kill it while things like prayers and readings are going on?[/quote]Those with a built in noise gate or downward expander. Pedals exist to do the same thing with your bass, most rack mount compressors also include a noise gate and/or downward expander.

[quote name='fenderiko' post='623194' date='Oct 11 2009, 10:59 AM']I disagree . I have the feeling that you need to speak, play , hear and interact with more guitar players. R[/quote]I play both guitar and bass, so I can speak on both sides of that great divide. For whatever reason I see a much higher percentage of guitar players falling into the "If Jimi/Eric/Stevie Ray (fill in your favorite Guitar God name) used it then that's what I need" mindset than bass players. OTOH I also agree that the technology of electric guitar peaked circa 1959, and that you can't get a better tone than a '59 Tobacco Burst or Strat through a '59 Bassman. Where the epitome of electric bass technology is concerned we haven't reached it yet.

[quote name='fenderiko' post='623156' date='Oct 11 2009, 10:11 AM']for me tone come first. then figure out if I can afford the damn thing . R[/quote]For me tone come first too. The point made is that weight and tone are not related. Some very heavy cabs sound really bad, some very light cabs sound very good. Having a cab that sounds good and is light as well is a win-win situation.

[url="http://billfitzmaurice.net/phpBB3/viewtopic.php?f=14&t=4140"]http://billfitzmaurice.net/phpBB3/viewtopi...f=14&t=4140[/url]

[quote name='Musicman20' post='622008' date='Oct 9 2009, 03:44 PM']I know it applies more to their guitar cabinets, but the Orange cabinets are made from 13 ply high density 18mm birch plywood. Is this an example of fast labour?[/quote] Probably. 18mm Birch does make a nice cab, and requires minimal bracing, so it's a fast and easy build, giving a good result with minimum labor costs. With adequate bracing 12mm birch can give just as good a result, with a lot less weight, albeit with higher build costs. If you price out 12mm versus 18mm you'll find not that much difference, not nearly enough for the materials savings realized using 12mm to come close to compensating for the additional labor that material demands for an equal result. Ask any structural engineer the best way to build anything to realize maximum structural integrity, stiffness and strength to weight ratio and they'll always reply [i]with minimal material thickness and maximum surface to surface bracing[/i]. An aircraft or boat serve as good examples of lightweight high strength construction. A Centurion tank is certainly strong enough, but it will neither float nor fly.

[quote name='stevie' post='621899' date='Oct 9 2009, 01:30 PM']His explanation about how stuffing works may be incorrect (although I think if you slag off Richard Small the least you could do is provide some supporting references) but the practical consequences of stuffing a sealed box are the same – you increase the effective box size! Call it increasing the compliance of the enclosure or lowering the system Q - these are both things that happen when you increase the size of the box.[/quote]When stuffing is used to achieve a lower Q overall system sensitivity and extension will be minimally altered, if at all. When a larger box is used system sensitivity will go up and extension will go lower. Using stuffing to lower Q can mimic the flatter response of a larger box, but it won't give the greater sensitivity and lower extension of a larger box.

[quote name='Balcro' post='621785' date='Oct 9 2009, 11:44 AM']Could the manufacturers also do this to deliberately give the speakers a rougher sounding edge? Balcro.[/quote]One could make that case, but the more likely explanation is that they don't want to add to the build cost of the cab by properly lining it. They'd feel quite safe in so doing based on the facts that most users aren't aware that the cab should be lined, and those who do aren't likely to examine the inside of the cab before buying one.

[quote name='stevie' post='621765' date='Oct 9 2009, 11:17 AM']Mr Small ([i]the[/i] Mr Small) disagrees. In fact, he disagreed in 1972 in his AES paper called "Closed-Box Loudspeaker Systems" when he said: "Many closed boxes contain filling material which helps to damp standing waves within the enclosure at frequencies in the upper piston range and higher. If the filling material is chosen for low density but high specific heat, the air compression inside the enclosure tends to be partly or completely altered from adiabatic to isothermal. This increases the effective compliance of the enclosure, which is equivalent to increasing the size of the unfilled enclosure. The maximum theoretical increase in compliance is 40%, but using practical materials the actual increase is probably never more than about 25%. An ancillary effect is an increase in the total moving mass of the system. Depending on the initial diaphragm mass and the conditions of filling, the mass increase may vary from negligible proportions to as much as 20%" It doesn't apply to a ported cab, though.[/quote]Mr. Small disagreed in 1972. In the intervening three plus decades the above explanation of how stuffing works has been found to be incorrect. As recently as three years ago the esteemed Vance Dickason's 'Loudspeaker Design Cookbook' still espoused this debunked theory, but in the latest edition he too has come on board with what is now recognized by the AES as to the true function of stuffing. How stuffing affects the cabinet Q and impedance can be clearly and easily seen with current loudspeaker modeling software; the accuracy of the software has been confirmed with actual measured results.

[quote name='Mr. Foxen' post='621597' date='Oct 9 2009, 08:50 AM']Does packing the cab with stuff (not just covering the walls) lower the speed of sound and make the cab respond as if it is slightly larger also?[/quote]No. Packing a sealed cab will lower the box Q to tame a midbass peak. Contrary to popular belief it will not give the same result as a larger box. Ported cabs should be fully lined, to no more than a 2" thickness, but not stuffed.

[quote name='OmeDunk' post='621633' date='Oct 9 2009, 09:16 AM']That wouldn't be easy, since I live in The Netherlands. Are there any other options?[/quote] Ask on my forum, we have members in the Netherlands.

[quote name='Ray' post='621295' date='Oct 9 2009, 03:54 AM']I've never known a bass cab to have foam inside.[/quote]Cabs that you may have seen without damping should be considered defective. There are two reasons for not fully lining a cabinet. One is that the manufacturer doesn't know any better, the other is that the manufacturer does know better but prefers not to go to the expense.

[quote name='fenderiko' post='620942' date='Oct 8 2009, 03:08 PM']so why making the cab heavy ? [/quote]Because it's cheaper. Many cab manufacturers make a big deal about using 3/4" plywood, as if that's a good thing. It's not. Manufacturers use 3/4" plywood because it will give an adequate result with minimal bracing and can be assembled by unskilled minimum wage help in less than two hours from start to finish. A properly braced cab made from 1/2" plywood will be significantly lighter than a cab made from 3/4", yet it will have the rigidity of a cab made from 1". But build time will be roughly doubled, as will the number of parts in inventory, so with the overwhelming majority of manufacturers that's not how it's done.

[quote name='Mr. Foxen' post='620822' date='Oct 8 2009, 01:07 PM']Labour intensive and don't lend themselves to mass manufacture.[/quote]What they don't lend themselves to is high profit margins.

[quote name='Monz' post='620452' date='Oct 8 2009, 07:21 AM']when you get to LOUD levels the lightweights seem to loose the ability to punch the sound forward and in the case of the ultra lightweights seem to vibrate rather violently[/quote]There's a right way to build light weight cabs, which when employed will vibrate less than heavy cabs while sounding better, and there's a wrong way. One guess which applies to the lightweights you tried.

[quote name='fenderiko' post='620191' date='Oct 7 2009, 08:22 PM']why designing them so heavy in the first place ? surely people rather not lift more weight ? ? what is making then so heavy ? the wood ? driver ?[/quote] Older drivers with ceramic magnets can weigh two to four times what newer neo magnet drivers weigh. Cabs made of cheap particle board or MDF will be heavier than those made of plywood. Well braced cabs made of 12mm plywood will weigh less than poorly braced cabs made of 18mm plywood. Birch is heavier than Poplar. There are many reasons why some cabs are light and some weigh a ton. But weight alone isn't an accurate predictor of how any speaker will sound.

[quote name='muzzer' post='619506' date='Oct 7 2009, 07:52 AM']Anyway, I have done some asking around locally and there is a furniture restorer close to me who will apparently do cabinet work so I'll give hime a go.[/quote] Insist that he follow the instructions to a T, including the choice of materials and adhesives.

[quote name='alexclaber' post='618703' date='Oct 6 2009, 10:59 AM']When you cut the lows on a bass amp it's akin to cutting the gain, i.e. turning the amp down, because most of the power demands for bass guitar are in the lows. Alex[/quote]And to paraphrase Mr. Franklin a watt saved is a watt gained.