Phil Starr

I think what has thrown us is the word tick. I didn't read theis thread until now because I couldn't think of anything which would make a rig give a regular ticking sound, but of course this isn't your problem. My guess is that your problem is a simple overload on the transients. When you pluck a string it moves a long way with the first pluck then the vibrations gradually die away so all the energy is concentrated in the first movement of the string. You say the problem happens with bottom strings and with volume and eq up. When you turn the eq up you are demanding more power from the amp and speakers. If your eq is +/- 12dB which is common then turning the eq up to 3 o'clock is demanding an extra 6dB. this is 4x the power so if you were running at 50W you are now demanding 200W from the amp and through the speaker. all the way up and you are asking for 800W! Now two things might happen which would cause a sharp sound (click?) The speaker cone is being asked to move a long way and it may hit something or simply be limited by the internal design of the speaker. You might even eventually blow the speaker. The second possibility is that the amp limits, chopping off the top of the waveform and creating some short term sharp distortion which will be audible. This sharp change in the wave will be turned by a crossover into an extra treble and passed on to the tweeter if you have one and could blow the tweeter. With my piezo tweeters I get an audible click when I handle the bass carelessly when it is up high. You've blown a speaker and removed the problem when you disconnected the tweeter so it could be either or both of these. The root of your problem could be the excessive use of eq. Cheers

You've a lot of things to consider. Try reading this for a superficial skim of some of the technical issues. [url="http://www.ultimate-guitar.com/columns/gear_maintenance/choosing_speakers_to_drive_your_cabs.html"]http://www.ultimate-guitar.com/columns/gea..._your_cabs.html[/url] There are a few main issues with speakers for bass: Frequency Response: this divides into those speakers which are basically flat (some Eminence and Fane), which gives a DI into the PA type sound and those which have a midrange peak (like some Eminence and Celestion) which will give a more lively and punchy sound but more coloured and characterful. You will need to also consider the bass resonance which will define the bottom frequencies you can reach Celestions bass speakers for example go nowhere near bottom E and speakers that go really low are usually less efficient because of the heavier cones. at the top you need to go to at least 4000Hz unless you use a tweeter/horn and speakers that go to 10,000 Hz sound noticeably cleaner to my ears. Magnet size: a big magnet allows you to do two things well. It improves the control of the speaker cone or damping and it lets you have a combination of more speaker excursion and/or efficiency. It also allows you to use as smaller cab. Look at the figure for Qts to judge this, a Qts of around 0.4 is a useful figure to aim for. Above this means a smaller magnet and usually a bigger cab, below this means a bigger magnet but below 0.3 you are getting to a very tight bass which is not to everyones taste. Excursion: how far the cone will travel before the coil comes out of the magnet. Most speakers run out of puff at low frequencies and high power because the cone is asked to do too much and this varies from one speaker to the next. The critical figure is Xmax, the bigger the better. Beware, Eminence use a different way of measuring this from Fane and Celestion who are more conservative. Multiply their figures by 1.5 to roughly compare with Eminence. I've recently used Fane 15's and 10's in my designs and they are the bargain of the moment. They are of very similar quality to Eminence and look like they could be made next to each other. Eminence are the market leaders and their range is second to none. Celestion's look a little odd to me; their bass speakers have very high resonance figures (well above bottom E for their 10's) and Xmax is poor even allowing for their conservative rating system but some people swear by them. One speaker you might consider is the Beyma SM212. Their price has gone up in the UK because of the exchange rate (they are made in Spain) but I built two PA speakers using these and I use them for small gigs for bass. They are beautifully made, quite loud (98dB for 1W), quite light and sound gorgeous for bass. mine are in a 40l cab tuned to 40 hZ.

dood is right but you may want a little explanation. Two things limit the power of an amp; the voltage it can swing and the power that the power supply can provide. Bridging the amp means that the voltage is effectively doubled, which in turn means 4x the power. However 4x the power means a lot more current is needed from the power supply and must be handled by the output stage of the amp. Which means that the minimum speaker load has to be doubled (usually) to protect the amp and that the power is less than you expect because heating limits the power available from the transformer. What actually happens depends upon the detailed design of the amp and to what extent it is over-engineered. Some designs won't allow you to bridge anyway. You have to check this out with the manufacturers.

Music in your amp is turned into a voltage that goes up and down above and below zero, mainly following a curve called a sine wave. Because the volts go - and+ equally the average is zero over a full cycle. Squaring the voltage makes everything positive then you can find the average voltage and turn this back into volts by finding the square root (hence Root Mean Square). It is just a mathematical trick to deal with an alternating voltage or current so you can compare it with direct current or voltage. You don't need to understand this but it might help. Measuring the output of an amp is easy. You just pass the output through a known resistance and measure the voltage drop at the point where the amp clips. There are all sorts of regulations about the detail of doing this to ensure your amp gives something like this in the real world but this is the basics. Speakers are tricky to rate. Music has loud and quiet bits and all sorts of frequencies in it. Speakers are tested with white noise (all the frequencies) filtered as pink noise which is meant to have the same sort of frequency content as typical music! Speakers are rated continuously and if they were rated at 35W should handle 35W of pink noise for hours at a stretch and as Mr Foxen has said this is about their ability to handle heat and not music. The reality is that the tests are far worse than anything you are ever likely to do to them and most speakers can handle more than their rated power. The other problem with speakers that is not mentioned so much is that cones can only travel back and forward a limited amount and a few watts of deep bass can make them reach this limit. All bass guitar speakers are designed to stop this from damaging the speaker and th better designers make the limiting forces naturally compress the sound to avoid the farting noise of a speaker reaching it's limits but the excursion limit or Xmax means many bass speakers give far less bass at high power than their specs would show. Anyone advertising the rms wattage of an amp or speakers is liable in law for the claims they make so these are hte only reliable measurement to use. RMS may be described as EIA in the US as this is the body that designs the test regime.

[url="http://www.ultimate-guitar.com/columns/gear_maintenance/a_guide_to_fixing_intermittent_faults.html"]http://www.ultimate-guitar.com/columns/gea...ent_faults.html[/url] This article may help but tracing down faults like this often take time. It could be anything from a dry joint finally starting to fail to a capacitor becoming leaky. Just make sure you give your repair man as many details as possible.

[url="http://www.ultimate-guitar.com/columns/gear_maintenance/making_it_loud.html"]http://www.ultimate-guitar.com/columns/gea...ng_it_loud.html[/url] An article I wrote on the topic which might be useful

[quote name='Mr. Foxen' post='807767' date='Apr 15 2010, 10:37 PM']The problem is each cab receives the same power due to the same impedance (not resistance), but the one with 4 speakers spreads it over all 4, whereas the other only to two. So the two will be reaching their excursion limit at half the power of the 4x10. The 4x10 will be louder due to better coupling with the air, and possibly drown out the sound of the protesting 2x10, risking a breakage. Better having a 16ohm 2x10, making a 6x10 with all speakers working the same, at 5.3 ohm, or two cabs the same.[/quote] this is one way of looking at it. if your 2x10 will handle the full output of the Ashdown now it will go on handling it whatever else you add in parallel. The amp is limited by its rail voltage (100v) which it can't go past. Adding more speakers will draw extra current from the amp and if the overall impedance drops below 4 ohms you could damage the amp but if the 2x10 can handle the amp then they will not be damaged. If you use speakers with different impedances then the one with the lowest impedance will draw more power. If the speakers are the same then doubling the surface area will increase the sound level by 3dB. An 8x10 with the same speakers will increase the sound by 6dB over a 2x10 even though the impedance and the power used is the same. This will have the same effect as using four times the amplifier power though it will not be four times louder because of the way our ears work. It will be significantly louder though. If you want to go down the route of a 2x10 and a 4x10 then give us the impedances and we can tell you what will happen.

Not sure of the details of the bright box but any cab with a crossover built in should have the effect of not increasing the impedance. Basically it splits the signal so some only goes to the bottom cab and some goes to the bright box. I think in fact the Bright Box has a high pass filter, which is half a crossover. This usually consists of a capacitor in series with the speakers. This has an impedance the same as the speaker at the crossover frequency and it rises as you get to lower frequencies so that at really low frequencies the impedance is very high and the speaker passes no current. At higher frequencies most speakers including your 1x15 will have a rising impedance curve. An 8 ohm speaker is only roughly 8 ohms and only at the bottom of its frequency range. at the crossover frequency it may well already be 16 ohms so bringing in an extra speaker at this point will leave the overall impedance back to 8ohms. As I say this is all theory, I couldn't find anything about the technical details of the bright box only that they are very desireable items. You've done well to get hold of one.

If you use the delta with the blueline then the delta will take most of the power and produce most of the sound. Treat the cab as a 300W cab. The deltalite needs a sealed cab with an internal volume of 8.959l for best power handling/efficiency but with a bass hump and rougher transients or 29.96l for the smoothest bass response anywhere between these will work. If you want to go vented then it needs 42l of air in the cab and you can tune the cab with a 10cm port 12.7 cm long or a 6.3cm dia port (downpipe used in your gutters) 3.33cm long. These give rough tunings which usually sound ok but you will do better if tou can access a signal generator and use Alex Claber's salt method to tune, Add 3l or so to these volumes to allow for the volume of the speaker and any bracing or battens you use. Cheers Phil

I'd restore the speaker to original which will leave you with a deltalite to play with or sell on ebay. You could always build a cab for it if you are handy. We could give you dimensions.

There are two reasons for using thicker wires, current handling and lower reistance. The wires you will be using internally are so short that resistance is not a factor, there won't be any noticeable power loss. any of the cables above will handle the current. I use 42 strand from maplin rather than 79 simply because it is more flexible and places less stress on the soldered joints than the thicker wires.

Just a thought, no one needs 2x8x10's for the sound but it would look great. why not have an empty cab so you not only impress with the size of your stack but that you are seen carrying one of the cabs with one hand.

Don't knock the infinite baffle. Yes the cab will start to roll off a little higher and you'll lose 3dB at resonance but the sealed cab will roll off at 12dB/octave much slower than the 24dB/octave of the reflex and so at real lows there will be a little more output. (I might model this later if I get time) in addition you'll get better control of transients and excursion will be limited at subsonic frequencies. What I assume is happening is that the Deltalites resonance is 53Hz, slightly higher than bottom E and a fair bit higher than B which is apparently causing your problems. In addition your cab won't be properly tuned. There is little resistance to the excessive movement of the poor deltalite's cones at frequencies below50Hz and they are 'hitting the stops' Sealing the cabs will limit this and in a gig situation you will probably not notice the changes to the frequency response. I've been experimenting with this recently and although you can measure the frequency response changes and you can just hear them when you play unaccompanied in a gig it just isn't noticeable. Using socks to block the port is a great idea, you've nothing to lose and if it works you can make a permanent seal later.

Once you reach a certain point it is worth cutting your losses. I wouldn't just buy more speakers on the off chance that they might match the cab, either build a cab to match your drive units, put the old speakers back (I know that you would need to buy one new speaker. Alternatively adapt your cab to match your Deltalites. One way of doing this is to turn it into an infinite baffle (sealed cab) by closing off the port. This would load your speaker and probably stop the over excursion which you seem to be having. For optimum damping/frequency response(Qtc=0.7) you need a cab of 60litres and with a small bass hump Q=1.1) a cab of about 30litres will do. If your cab is between these two figures then try sealing off the port with a piece of timber (make it airtight). The bass will probably be lighter and 'faster' but it should cure the problem and this cab will respond well to a little bass boost. Alternatively seal off the port and then make a new port, probably on the back panel, to tune your cab to the Deltalites. Someone will calculate the port dimensions for you if you tell us the internal dimensions of the cab.

[quote name='Mr. Foxen' post='782657' date='Mar 22 2010, 08:04 PM']Better spending that sorta cash on better cabs. Unless you have a fairly good understanding of such things, port cabs and speaker swaps are unpredictable.[/quote] This is good advice. Cabs need to match drive units and the sound of the bass end of the spectrum is determined by the match between the cab and speakers. Ported cabs need careful design if they are to work well for bass.If you want something custom then you would usually be better building from scratch than trying to adapt a cab. The trade-in value of your cabs will be less without the original drivers as well. Guitarists get away with swapping speakers because they don't use ported cabs they aren't producing much real bass most guitar speakers are similar in design little of this is true for bass, which is why you haven't been able to find much about it. If you still want to go ahead only do one cab and tell us the dimensions of your cab (internal dimensions) and the size of any ports and we might be able to suggest some possibilities.

[quote name='escholl' post='781437' date='Mar 21 2010, 10:17 AM']Where are you getting this measurement of 10dB from? What nominal input level is the power amp looking for? Is is looking for +4dBu? The important thing to do is just to listen to your amp -- does it sound distorted? If it doesn't, then you've nothing to worry about. As the saying goes, listen with your ears, not your eyes.[/quote] I'd go along with this. Meters are a useful indication but not all power amps run off 0dB and the impedance needs to be taken into account too. If your ears say the setting is clean then that is usually good enough but male sure that you stick on or below these settings at gigs where the temptation to turn up is greater and the ability to hear distortion reduced.

The problem is that vinyl is shiny and hard to stick to and flexible so it needs a paint which will flex with it. The only paints that will do this are latex paints which won't stick and acrylic paints which are too soft. Any paint you apply will peel off in sheets or flake off if it is not flexible.

[quote name='Stylon Pilson' post='778372' date='Mar 18 2010, 10:38 AM']In the context of bass speakers, I was under the impression that it was the other way round. Again, I'm doubting that you know what you're talking about here. S.P.[/quote] No, I do try to be accurate in technical answers and all of this is in various texts. Rating a loudspeaker is surprisingly difficult for manufacturers. They really need to get as close as possible to the likely use of the speaker which is usually playing music but music is such a complicated thing that it is impossible to model objectively. Pure sine waves are nothing like music because apart from anything else there is only one frquency. You could use a random mix of all the frequencies (white noise) but music doesn't have energy evenly distributed so instead we usually use white noise filtered to more accurately resemble music (pink noise). Various test conditions are used (EIA,AES etc) but basically this 200W speaker probably got its rating by having pink noise passed through several samples for several hours (different for each standard) with none of the samples failing. The problem with this test is that it simulates every sound being at full volume all of the time. A bassist playing 16 beats with a heavy pick and driving the amp into clipping wouldn't be close to getting this much power. Speaker manufacturers then try to give other indications of power handling by quoting 'peak' ratings either at specified distortion levels or as a 6dB crest value (Eminence,Fane do this). None of this really describes real life. If you play with a dynamic range of,say, 40dB then your average power is 20dB down on your maximum power, so if this 250W amp is not being driven into clipping it is only actually developing an 'average' of 2.5W of heating and even at moderate distortion the long term average is likely to be less than 20W. The speaker shouldn't fail because of overheating. The next failure condition that causes problems is over excursion. The speaker is pushed beyond its limits of travel Xlim. as the coil moves out of the magnetic gap the electrical forces on it diminish. back in the 1930's speakers failed because designers didn't compensate for this and there was more of this in the 1950's and 60's when electric guitars and bass were used with what were essentially domestic speaker designs. The designers can get round this by making sure the suspension mechanically limits the excursion by proper design of the suspension. Celestion, Fane and eminence do this and so I expect do all the 'name' manufacturers. It is hitting the mechanical limit which causes the farting noise. The other reasons for failure are corrosion of the metal parts (beware aluminium coils) and fatigue due to the repeated high accelerations a speaker is subjected to. I could go on but I suspect most people won't be interested. The only other thing is that when driven into distortion an amp heats the speaker more than under undistorted sine wave conditions, up to root two (1.414) times the power for maximum distortion. This is more relevant to synths than bass. So matching speakers to amps for power is a little subjective. If you want to be completely safe then use a speaker better than 1.414 times the amps rated power but be aware that you will only be using a fraction of the speakers power handling. If you use a moderately clean sound you will have no trouble using speakers roughly matching the amp. If you really want a clean sound then there is nothing wrong with using a little amplifier overhead. PA engineers often use 6dB extra in the amps because amp clipping sounds worse than momentary speaker limiting. This means using 1000W amps with 250W speakers (but they do monitor for clipping). Some bass players do this too to get clean peaks. Obviously the harder you work your speaker the greater the accelerations it is subjected to and the sooner it will start to fatigue but regard the power ratings as a guide only. Under normal conditions this 200W speaker will work happily with a 250W amp for many years, just be aware that it is slighly under powered and if it distorts, turn it down.

I build a lot of speakers but the best sounding one for bass was an accident in that it was built for PA and used when I was between rigs. The drive unit was/is a Beyma SM212 350W, 98dB sensitivity 45-6000Hz at -6dB. I chose it as it has an excellent excursion figure due to a long voice coil (xmax is 7mm) so it won't run out of bass at high levels. It has a cast chassis and looks to be well made, so far utterly reliable after two years. Available from Blue Aran. If you want the cabinet dimensions I could send them.

Painting the vinyl will leave a mess whatever you use and bitumen as you will have gathered would be a big mistake. You can stick down any loose bits of vinyl with white PVA adhesive. For the stubborn curly bits coat both surfaces with glue, allow to dry and then iron down with a warm (not hot) iron. then get a felt tip pen and shade in all the tears and missing bits and scuffed bits so they don't show up. Once the glue has set spray the vinyl with WD40 and polish, it will lift the dirt and leave the vinyl like new.

It isn't usually the peaks which destroy modern speakers which are designed to mechanically limit this problem. They burn out when they are driven by excessive amplifier power over long periods of hours rather than minutes or seconds so it is your average power that matters. The peaks may sound like the aftermath of a mega chilli but they won't necessarily damage the speaker. A compressor restricts the peaks but will also boost the average level which is why the ads sound louder on TV. Having said that you shouldn't have any problems unless you run into distortion. Keep your speakers sounding clean and stop worrying.

You can buy a socket tester for a few pounds which will test the house wiring you are plugging into. always use an RCD with your gear. It is also sensible to plug all your amps into a single output so all the earths are at the same potential. You could get hurt or even killed if you are unlucky, why take a risk. I've written an article on this if you want to check it. Happy to write another for this site if anyone asks. [url="http://www.ultimate-guitar.com/columns/the_guide_to/this_article_may_save_your_life.html"]http://www.ultimate-guitar.com/columns/the..._your_life.html[/url]

[quote name='Fraktal' post='765416' date='Mar 5 2010, 05:23 PM']Partly because of the fun and partly because a very good local sound engineer was showing me there was no risk of blowing my 2x15 with a QSC power amp after I asked him. I was obviously very concerned about driving my dear 600w cab with a 2400w amp at full power, I always thought that was the quickest way to build up totally justified GAS for a new cab! To be completely honest here, I still cant understand what happened there. Maybe those amps monitor the speaker displacement somehow and limit themselves accordingly? The sound guy insisted it was safe to drive any given speaker with a goop pro PA amp several times the wattage as long as there is a "lack of square-wavy distortion", but I have heard equally respected professionals stating that is all bullshit. It would be great if Bill Fitzmaurice or Alex show some light on this subject (If you all can excuse this "off-topicness").[/quote] It is fairly simple. you have loud bits and quiet bits in your playing. if your dynamic range is 40dB then your loud bits are 20dB above your average level. 10 dB is 1/10th of the power and 20dB is 1/100th so a 100W amp, not peaking, is probably only giving an average of 1W. Your speaker is rated at 600W 'average' over a long period (several hours)and it is the waste heat that will blow it. So long as you have no distortion and the clipping light stays off then your speaker may limit the sound but it won't cook. The square wave stuff is because the amp will turn a sound wave into square waves if you drive it hard enough and this will contain up to 1.414 times the energy. Most of this is high frequency so watch the tweeters if you have them.

Check the bolts that hold the speaker down also. If none of this works the speaker may be coming unglued, check the corrugated surround and the dust cover (dome in the middle) They can be re-stuck with a latex based glue (Copydex) and small holes patched with layers of tissue laminated in copydex. Unless it is still under guarantee of course.

[quote name='mr.sibs' post='767701' date='Mar 8 2010, 10:47 AM']interesting idea - will the sound of a pa monitor be suitable as a bass cab? any idea the most suitable if such a thing exists??[/quote] This is probably your best option unless you really want to spend a lot of time or money. A PA speaker is designed to handle bass at the level of the rest of the band and may even go down lower than most bass cabs, frequency limitations are unlikely to be a problem. You are going to be limited though to just a single speaker + horn in most cabs so the ultimate sound levelwill be lower than say a 4x10, not a problem unless you have silly levels on stage though. Remember that PA speakers are designed to have a neutral sound and some bass speakers are designed to add character by having an uneven frequency response. If you like the sound of DI'd bass you are going to like this route, all you'll get is then sound of your bass it is going to sound very clean. It may be worth looking for one with a DSP (digital processor ) in it which will give you a lot of protection for the speaker increasing the reliability, if it includes compression in the processor then it will give you extra loudness. Active PA speakers should be more reliable than many combo's in any case. Finally you get what you pay for in PA units just like instrument amps the best ones will be loud deep and reliable the cheaper ones not so much.