Phil Starr

[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.

Building cabs can be as expensive as you like, just as buying ready made cabs can be but generally you will always end up with better quality sound than you would buy new at every price point. Unless you are a good craftsman you generally won't get the finish and the cab won't have much of a resale value so buying second hand will work out cheaper if you include the resale value. I've just built a 2x10 for under £100 not including coverings for example. Designing cabs can be tricky and you have three options, copy a commercial unit, use one of the existing diy designs or get to grip with Thiele/Small modelling. There is not much point in using the computer modelling like WinIsd or the simpler and clearer AJ software if you don't have any grasp of what they are doing. I'd strongly recommend the 'Loudspeaker design Cookbook' if you want to read up on the technical side to see if this is for you. Have a look at [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] and also the article on speaker cabs which this article links to. Consider building a sealed cab also as a first build. You will get a little less bass volume for your money but the build will be simpler and the bass loss isn't as much as you have been told. Most of the failures of first builds centre around problems with the ports. If you choose a drive unit to use then someone here will work out the volumes and port dimensions for you to match that driver. Building your own gives you immense satisfaction and you will learn loads. There is only one way of finding out if it is for you.

I think you've got us all thinking here. You are running more power than most of the rest of us but if your amp is clipping and shutting down then clearly you have to fix things. What impedance are the bins? If they are 8 ohms then you will only be getting half the rated power through the Crown. The clipping light will be voltage dependant so no worries but the shut down could be dependant on the current or the voltage from the amp. What I am thinking is that if the subs are 8 ohms you can add two more and run them off the existing amp. This will give you an extra 6dB which is the same as increasing the amps power by 4. Basically running the extra speaker will draw double the power from the amp and the extra speaker surface area will improve the coupling with the air at low frequencies and increase the efficiency. Ok I've done some checking and the Crown only gives 1000W into 2 ohms 800 into 4 and 475 into 8. Which bass bins are you using? The idea of using some compression on your bass bins is a good one it will give more punchiness and you can move the average sound levels higher without peaking out. If you have a limiter on the compressor it will cut the peaks out as well which will be almost inaudible at these frequencies. Several manufacturers are starting to build this trick into their active subs now. The other trick while you figure this all out is to cut the bass a little on the mixer. 3dB will only just be noticeable and will give your amp a lot of breatjhing space. If the amp has a subsonic filter then use it losing everything below say 40Hz won't really affect your music unless you use a lot of synth and again reduces the load on your amp. I assume the subs are on the floor, this doubles their efficiency at low frequencies and moving them against the side walls will also help. It is really hard to mix from the stage. Do you have someone you trust who will give an honest opinion of your sound? You may be sounding better than you think or even bassier than you think.

It might simply have been old age, bits of me come off from time to time. If you still have the dust cap then stick it back on again. clean off any dust and stick it with copydex or any other latex based glue. This will restore the air flow over your coil and stop the dust getting in to damage your voice coil.

It depends on what you are trying to do. This is a already pretty impressive set up. The jbl's i find a bit bass heavy if anything and you already have subs. does your sound engineer have any indication that you are running out of bass grunt. is the XTi 2000 clipping? If you just add subs then you will only get extra sound below the crossover frequency and your sound wont be any louder psychologically, it will just get more gut wrenching which is fine if that is what you want to achieve. A bass bin which has a higher crossover frequency would beef up the bass and possibly reduce the demand on the PA but it will change your tone so that it becomes a lot deeper again this is fine if you want that effect. If you just want to be louder or to maintain the same volume then you will need either a bass speaker (which you can put out front to keep the sound off the stage) or to beef up the whole PA, If your PA isn't clipping you don't need to do this and you can put your money towards something else

[quote name='lanark' post='752223' date='Feb 20 2010, 09:12 PM']So your reccomendation is to insist he use the balanced DI socket instead of the line out unless he has a damn good reason not to?[/quote] If you've got a balanced input then it is best to stick to the balanced output because it will pick up less electrical interference and be cleaner but I was just imagining, having been a sound man for several years that he was being asked for more 'level' rather than actually to be louder. It was just a thought. [quote name='elliswasp' post='753798' date='Feb 22 2010, 01:38 PM']yeaj i know there isnt a great deal of difference in actuall listening volume when it comes to amps being twice the wattage its something like a 10% increase or so apposed to double which is what lot of people think because the wattage has doubled im hoping that i wont need any more than that as im not really prepared to spend any more money if its still not loud enough im gonna be a little stumped i guess it will be the drivers il have to change or something. heres hoping not im rather hoping it was more to do with the venue than anything else. Big open space with really high celings cant be good im sure? Markus[/quote] Fortunately adding the extra cab gives you an extra 6dB because not only does the amp give more power but the speakers increased surface area improves its mechanical coupling to the air making it louder. basically at low frequencies more of the speakers energy goes into making sound rather than just stirring the air. If you are going through the PA then the only reason you need an amp at all is so that you and the other band members can hear what you are playing on stage. Your set up really should be loud enough. Even if your 15's are very inefficient at say 94 dB/w then two with 200W through them will produce peaks of 120dB which means you could easily play at an average level of 100dB which is loud enough to cause permanent hearing loss if you keep it up for long. If you are having trouble hearing then try this: turn down the bass a little (10-11 o'clock on the Ashdown) this will allow your amp to go up a bit before it clips which means you can have more of everything else. Try gently boosting the mids which is what you hear more clearly when everyone else is going. If the Ashdown is the Evo model then use a bit of compression which moves the average level a bit closer to the peaks and makes everything sound louder just like the ads on TV sound louder than the programs.