Bill Fitzmaurice

[quote name='NJE' timestamp='1448813552' post='2918322'] ...simpler still just keep one cab and have it angled at me at the side of the stage maybe?[/quote] If you're always at the side of the stage that's your best bet, and it leaves you with the option for using both cabs in a standard back-line configuration should the need arise.

[quote name='Merton' timestamp='1448724590' post='2917672'] Thought I'd give this a go with my Ashdown RM210 cabs. The tweeter and simple (series) RC crossover is is parallel with the main drivers so I can't see an issue with just chopping the wires at the tweeter end on this particular cab. Will take the RC crossover out too at some point just to be safe though... [/quote]A high pass filter with no resistive load can present an impedance load approaching zero at high frequencies, which can cause high frequency oscillation in the amp.

[quote name='icastle' timestamp='1448567977' post='2916571'] Never tried it but this stuff sounds about right... [url="http://www.vinyldye.co.uk/"]http://www.vinyldye.co.uk/[/url] [/quote]Dye should work OK, paint will rub off.

[quote name='ambient' timestamp='1448230812' post='2913882'] it works better if it's against a wall, that's how it was designed [/quote]Those slots cover a passive radiator, which functions in the same fashion as a port. You're correct in that close to the wall placement enhances the bass, but it does so by boundary loading.

[quote name='Chienmortbb' timestamp='1448056244' post='2912847'] Today many drivers are around 94dB and that old 50 watt baseman would need to be 200W to get the same perceived old skool volume. [/quote]The main change in drivers has been the development of true bass drivers with long excursion. Most of the old school drivers weren't bass drivers, they were generic musical instrument drivers, ie., guitar. I had a 50w Bassman, and it would give sufficient output to play loud, long before we had good PA, but not with the original Fender 2x12s, nor even with two of them. Before I embarked on building my own cabs the only rig that could take my Bassman undistorted was a pair of 4x12 Kustoms. It's the same reason why the original '69 SVT needed two 8x10 cabs to handle 300 watts cleanly. As for sensitivity, where it counts for us, below 100Hz, it hasn't gone down compared to vintage gear, it's gone up, not only due to the drivers but also the cabs.

[quote name='chris_b' timestamp='1447837841' post='2910744'] Heat isn't the enemy. All amps generate heat in their components and they are designed and built for that. Too much heat could be a problem but many amps these days have protection circuits built in to cut out if they go out of spec. [/quote]There's a big difference between short term overloading that will cause protection circuits to trip and long term heat damage to components, for which there's no protection.

[quote name='bassman7755' timestamp='1447773420' post='2910214'] To be fair though I think most people use a 4 ohm load because they want to run two cabs rather than to squeeze extra power from the amp. [/quote]If you peruse threads you'll find that just as many use two cabs to get a lower impedance load in search of more power. They do get more output of course, but due to the increased sensitivity and driver displacement that two cabs gives, not more power. It's also not the least bit unusual to find those who want to replace the drivers in a cab to get a lower impedance load, again in search of more power. Of all the attributes of an amp power is the least significant, but you'd never know that by reading manufacturer advertising.

FWIW it's not resistance, it's impedance, and the issue isn't power, it's current. The lower the impedance load the higher the current draw, which increases heat, and it's that heat which lowers component life. You often see questions about using lower impedance speakers "to get all the watts out of my amp", and that's usually not a good idea. As noted this doesn't apply to valves, where the load isn't the speakers, it's the output transformer.

[quote name='leroydiamond' timestamp='1447695402' post='2909586'] What your opinion on Hi Fi floorstanding speakers, particularly with regard to using spikes as opposed to rubber feet on suspended timber floors? [/quote]The only benefit to spikes is that they will grip better than rubber feet on carpeted floors, which can reduce the tendency of a speaker being pushed at very high levels to 'dance' across the floor. All of the other claims made for them are hogwash.

[quote name='discreet' timestamp='1447541501' post='2908496'] Presumably if the tweeter level was set at, say, 50% or so as a precaution against the probability of burn-out, then it would take proportionately less extreme EQ settings to achieve the final tone. [/quote]+1. A 50% setting, which is down 4.5dB, shouldn't cause a heat issue. Where it's usually a problem is when it's turned fully or nearly fully off, and being a resistor all of the power going through it is burned off as heat.

[quote name='discreet' timestamp='1447534682' post='2908453'] [color=#282828][font=helvetica, arial, sans-serif]From what I can glean from t'interwebz, minimising tweeter activity with the LPad (the big potentiometer-type thing on the back which varies the effect of the tweeter) can produce a resistance in the circuit which manifests itself as heat in said LPad - it is possible to burn out the LPad [/font][/color][i]and [/i][color=#282828][font=helvetica, arial, sans-serif]the crossover [/font][/color][i]and [/i][color=#282828][font=helvetica, arial, sans-serif]even damage the tweeter/horn in the process. Allegedly.[/quote][/font][/color] [color=#282828][font=helvetica, arial, sans-serif]Assuredly. It's rare, usually the result of inadequate slope in the high pass filter and an LPad that's undersized, but it does occur. [/font][/color] [color=#282828][font=helvetica, arial, sans-serif][quote]I have read on TB and elsewhere that if you have a cab with a tweeter/horn you should run the cab with the tweeter ON and make subsequent necessary tone adjustments using your amp EQ. I have a cab with a tweeter and have recently started running it with the tweeters up FULL as an experiment - and it [/font][/color][i]is [/i][color=#282828][font=helvetica, arial, sans-serif]indeed possible to make the necessary adjustments at the amp.[/quote][/font][/color] [color=#282828][font=helvetica, arial, sans-serif]That's why they put those knobs and sliders on the amp. However, you might find it's best to use a combination of moderate lowering of the tweeter level with the LPad along with EQ. [/font][/color] [color=#282828][font=helvetica, arial, sans-serif]Most of this issue can be traced to the use of a horn loaded tweeter that has much higher sensitivity than the woofers, and could be avoided by using a midrange with sensitivity closer to that of the woofers. This also eliminates the typical response dip in the 2kHz-3.5kHz region between where the woofers leave off and the tweeters kick in. But they're more expensive than horn loaded tweeters, as are the required crossovers, so they're rarely employed. [/font][/color]

[quote name='Naetharu' timestamp='1447520620' post='2908308'] is it safe to just cut the connection to the tweeter and have done with it? [/quote]It's not. Depending on the crossover configuration doing so could cause high frequency oscillation in the amp, leading to amp failure. If it has a crossover it should be removed or bypassed.

If the horn hisses it's working. The source of the hiss isn't the tweeter, it's the amp. Speakers will only reproduce the signal that is sent to them. [quote] is this the intended functionality? [/quote]The intended function is reproduction of frequencies above the range of the woofer. The typical implementation tends to be flawed, as what's required isn't a tweeter that starts at 4kHz, it's a midrange that starts at 2kHz, if not lower.

[quote name='Ian Savage' timestamp='1447346462' post='2906942'] one of these should do it, right? [url="http://www.duramat.co.uk/checker-plate.shtml"]http://www.duramat.c...ker-plate.shtml[/url] [/quote]That may be of higher density than you want. Try kitchen supply stores for a resilient mat. Another option is a yoga mat.

[quote name='Ian Savage' timestamp='1447344307' post='2906910'] I'm getting some problems at high levels with my Laney Nexus bass head seemingly vibrating in sympathy with the matching 1x15" cab it sits on a producing a low-level crackling noise with the very lowest notes. [/quote]While vibrating cab panels won't cause a stage to vibrate, that would be the tail wagging the dog, they can cause a head atop them to vibrate. All you need to fix that is a piece of this, cut to size: http://www.homedepot.com/p/TrafficMASTER-Black-24-in-x-36-in-Anti-Fatigue-Vinyl-Foam-Commercial-Mat-60-571-0900-20000300/202015909 UK sources for something similar must exist. That said, vibrating panels suck away energy that should be going out to the audience as sound. Even a single brace connecting the middles of opposing panels will halve the energy lost.

[quote name='karlfer' timestamp='1447243926' post='2906016'] Anyway, just wondering what is the best way to stack them, photos 1,2 or 3. Basschat experts, your advice please.[/quote] This: [url="http://s1354.photobucket.com/user/Karl_Altdorfer/media/001_zpsuui24s2u.jpg.html"][/url] It gives the minimum distance between the tweeters while keeping them on the same vertical plane. It would be better to have the cabs mirror imaged, so that the tweeter would be at the top of the lower cab and at the bottom of the upper cab, both on the same vertical plane. That arrangement is specified in my DIY cab plans, but with commercial cabs you don't have that option.

[quote name='Skybone' timestamp='1447160956' post='2905355'] The decibel scale is based on a Logarithmic scale, not a linear scale. .[/quote]True, and that's why 10dB is perceived as a doubling of volume. 3dB is a doubling of radiated power, not perceived volume.

[quote name='Happy Jack' timestamp='1447100195' post='2904914'] That's cheating, that is. Them's [i][b]valve [/b][/i]watts which are a whole nother thang. [/quote]A watt is a watt. If you want to do the same with 100w SS as you can with 100w valve use a compressor. [quote]Surely a Jack cabinet with a 200W amp and you are good to go Bill. [/quote]I only run 160w into mine.

[quote name='bonzodog' timestamp='1447089978' post='2904762'] I appreciate watts is not a good way of measuring volume but think its clear most 500w amps would be louder than 200w [/quote]By 4dB to be precise, which isn't worth the bother. As equally valid a question is what is the point of 500w amps? If I manufactured amps I'd make the size differential between models at four times the power rating, say 50w, 200w, 800w.

[quote name='Jono Bolton' timestamp='1447014006' post='2904199'] As the screw holes of the speaker overlap the screw holes in the baffle (but don't line up), what would be the best way to secure the speaker in place? [/quote]Pull the driver, fill the old holes, rotate the driver position 30 degrees, drill new holes.

[quote name='Jono Bolton' timestamp='1446929549' post='2903635'] One of the screws connected the bottom driver to the baffle wasn't tight and the screw holes on the speaker don't match the holes in the battle so it's not got a full compliment holding it in; as a result almost the whole left side of the bottom driver wasn't secured. [/quote]That would be problematic to say the least. The driver frame could vibrate against the baffle, with the same effect as rapidly whacking it with a hammer.

[quote name='shizznit' timestamp='1446986886' post='2903900'] they behave quite differently.[/quote]The particular neo drivers you have may behave quite differently from the particular ceramic drivers you had before, but that has nothing to do with the magnet material. Flux is flux, no matter the source, be it neo, ceramic, alnico or field coil. If there was a characteristic neo sound, or ceramic or alnico, then all neo driver would sound the same, as would all ceramic, etc. That's no more the case than all tens sounding the same, or all twelves, or all fifteens. [quote]Swapping drivers in a cab has always struck me as an illogical thing to do since the cab has to be designed around the driver, most likely outcome is that you end up something that sounds worse and is worth a lot less money than what you started with. If you want a lighter neo loaded cab then buy one[/quote]+1. Besides, not only do all neo drivers not sound the same, they don't all weigh the same, nor do all ceramic drivers. For instance, Orange uses Eminence Beta 10 ceramics, which weigh 3.1 kg. The most common neo ten is the Eminence Deltalite II 2510, which weighs 2.1 kg, so with four you'd only save 4 kg. OTOH there's the Kappalite 3010MB, and it weighs 3.2 kg.

[quote name='Ghost_Bass' timestamp='1446736503' post='2901885'] I think that any type of base (not just gramma pad) with such a low height won't do anything to isolate the cab. There's a bit of height needed to "decouple the bass from the ground", i use an amp stand and lift my cab about 1 metre from the ground, this works! [/quote]What you're referring to is acoustic decoupling, which is a real phenomenon. Full boundary loading occurs when the speaker baffle is less than 1/4 wavelength from the boundary. At 1 meter 1/4 wavelength is 85Hz, so you'll lose boundary loading above that, which can be effective taming boom, as that typically occurs in the 80-160Hz octave. [quote]I only see one use for those isolation foams, it's when you play on a hollow and flimsy stage and dial enough lows on the amp to make the entire stage vibrate (vribation of the cab being transmited to the stage) [/quote] A cab that flimsy is defective. Even in that case all that's required to 'decouple' the cab is rubber feet. If what decoupling devices claim is true then a drummers sticks left atop his kick drum or the snare wires beneath the snare drum wouldn't vibrate when you hit a note, since the cab isn't even remotely close to being in contact with the drum heads. Stages vibrate for the same reason as drum heads do, in sympathy to the sound that the speaker creates, not any vibrating of the cab walls.

[quote name='bassman7755' timestamp='1446705176' post='2901549'] Well speaking as someone with amateur interest in electronics (and therefore not really and "expert"), a pure square wave requires infinite signal bandwidth to amplify accurately and most audio signal chains have various filters which will attenuate the extreme high and low frequency content so what arrives at your speaker probably wont look much like a square ware.[/quote]Correct. First and foremost of those filters are voice coils, which are inductors, and as such function as first order low-pass filters. [quote]The clipped signal still contains more energy for a given amplitude though than a clean signal and so yes you will have to make some allowance for that. [/quote]Close. At the fundamental frequency the power density of a pure sine and pure square wave is identical. It's only in the harmonics where power density of a square wave is higher, and that's why tweeters and the occasional midrange can be vulnerable to the higher power density of a clipped waveform, while woofers and subs are not. That's one reason why guitar amps don't use tweeters, and why if you're a bass player running distortion pedals you shouldn't unless you roll off the high frequency EQ on your amp to compensate for the high frequency boost that most pedals create. The exception, and there are always exceptions, would be a bass specific pedal that has internal EQ compensation to tame the highs.

I suppose as far as placebos go they're cheap enough, but they're still placebos. I've never been able to find a single bit of objective data from any of the makers of either isolation or coupling devices (and you really should wonder why there are both) so I obtained my own. The results are posted here: http://billfitzmaurice.info/forum/viewtopic.php?f=10&t=19112 BTW, since hockey pucks are a high density material if they did anything it would be to increase coupling to the stage, not reduce it.