Phil Starr

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.

Hi Sam, I don't know if your Ibanez is active or passive, passives give outputs of a few thousandths of a volt actives a few tenths of a volt usually. most power amps are designed to take a 0dB input which is just under a volt though this can vary also. Fortunately amplifying a guitar up to line levels is just a straight piece of amplification and almost any simple pre amp will do it. If you have a practice amp with a headphone output then this will probably drive the power amp. I use my iPod to drive our power amp directly for example. I've also used a mixer aimed at editing the sound on videos which I got for £10 to drive into a power amp when my head broke down. You can buy cheap preamp units from Maplins also. When you can afford it there are lots of effects/modelling boxes that will give a line output and have plenty of gain which you can use to replace the cheap and cheerful solution. Interesting though, I rarely touch the tone controls on my Mag either especially at gigs, though I do roll off the bass a little when the room acoustics are bad. Apart from that I change tone by altering my picking position, dialling the bridge pickup in a little for some songs and cutting the top with the tone control on the guitar. I just prefer the sound of the guitar as clean as possible. Cheers

Have a read of this for the technical side of choosing an amp. [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] Your going to need 200W if it is going through a reasonably efficient (loud) speaker. I personally wouldn't buy any amp I couldn't try whether new or second hand as the sound it makes is kind of the point. I've used Peavey and Ashdown, both good and in your price bracket but there are plenty of others just as good. Think about what you want to carry too. Thats why I lost the Peavey 2x15.

Ooh there's nothing like a good tech debate. Is there something special about the relationship between bassists and speakers. Regarding Xmax. Celestion give the length of the coil and the magnet gap and the difference between the two is how far the coil can move without coming out of the gap. The magnetic field extends beyond the gap a little way getting weaker as it goes so the further the coil and cone move the greater the distortion. It is not clear on the Eminence website how they calculate Xmax but two years ago they used the same method as Celestion. I decided against Celestions because of the excursion/Xmax issues with my own speakers by the way. Why, if you are stuck on Celestions, dont you go for the BL series which have better excursion. Although they have conventional magnets you aren't going to notice the extra weight with your monster cab. The neo's are designed to have a light fast bass and they have sacrificed overall bass output to achieve a certain sound. You could also look at the Fane Sovereign range in this price bracket. (slightly cheaper actually) If you cant get on with the software try this [url="http://www.ajdesigner.com/speaker/index.php"]http://www.ajdesigner.com/speaker/index.php[/url] which is dead simple, just type in the figures from the manufacturers spec sheets. Not as versatile as other programs but it will calculate the basic enclosure sizes and port dimensions and give you a frequency plot at 1W and full power. Cheers

the internal speaker is 8ohms and the ashdown only develops it's rated output into 4 ohms. It is designed to work with the extra cab so no worries. Your sound man may have wanted things up high for two reasons. If you put out the bass through the stack and keep it out of the PA and monitors it reduces the demand on the PA and can clean up the sound. Alternatively he may have just wanted a high level feed to the mixer because it reduces noise and/or the mixer lacked an input which was sensitive enough for the feed. The line out on an Ashdown is only at mic level and a lot of cheap mixers only have a limited no of mic pre amps to keep costs down. The line out on my Ashdown is at quite a low level. In other words he wanted it turned up at the mixer but not necessarily on stage. An Ashdown giving 200W into 2x15 should be loud enough to drown out the drummer unless you are cutting the mids and boosting the bass

The trouble with these debates is that they are in terms of watts and not about how loud things are, which is measured in decibels. If your amp/speaker combination can reproduce 100dB average and 120dB peaks it will be loud enough for anything including permanent damage to your hearing. An efficient speaker will produce 100dB with one watt, doubling the power produces an extra 3dB and ten times the power 10dB so 100W will produce an extra 20dB and 200W 23dB. So 123dB which is plenty giving you 3dB of headroom through this speaker. Average speakers in combo's often produce only 96dB/W so a 200W combo might only get to 119dB. Then you add in effects. A compressor will limit the dynamic range so if you have it on low it might gain you 5dB or on high 10dB still leaving you with a dynamic range of 20dB. If you use 3dB bass boost you will need to double the power of your amp and 12 dB will need 16 times the wattage. A lot of the problems come because people miss the point that our ears don't work in a linear fashion. Doubling the power is only a small increase in volume, you need ten times the power to get double the volume. This is why bass amps come in silly powers an 800W amp isn't twice as loud as a 100W amp through the same speakers! It is also much better for your final sound to keep the volume down on stage as all the old musicians know. There are a whole load of technical reasons for this which I've written about on Ultimate Guitar, but for a touring band it can be a good decision to keep the bass out of the PA. Putting bass through the PA is an expensive decision as you will need a much bigger PA. Potentially you might need to upgrade your main speakers and add bass bins plus their associated amps. It is a lot cheaper to just put in a big bass stack and since bass is fairly non directional you can still sound good. All you lose is the ability to adjust bass levels from front of house, so long as you keep the bass filtered out of the vocal mics. There's nothing wrong about either way of putting out bass to the audience, PA or stack, it is just a decision you need to make. So I guess people putting 100W through efficient speakers are making good choices and so are people using 1000W amps through less efficient speakers. You need more power if you boost bass ( though you could just change your speakers) and less if you cut bass or use compression. It is sensible to go through the PA and monitors and it is sensible not to do this.

Yep you are right. At low frequencies the cone has to move further to achieve the same velocity so excursion becomes important. Without knowing the details of how excursion is limited in the Hartke's I couldn't say whether you will damage the speakers but I personally would look for something else. Generally speaking open back cabs won't go low enough for satisfactory bass as they would need to be huge (4mx4m) to reproduce bass. In addition the spring of air trapped in the cab helps control bass excursion as you have seen.

So long as you keep the sound clean you will be fine. Your average sound is only a fraction of the peaks. A 10dB headroom means you are running at an average of less than 50W. If you run into 'fart' territory or use a lot of effects though all bets are off

So long as you stay out of distortion levels you should be safe enough. The ratings of most speakers are EIA or something similar which is how much continuous power they can handle without overheating. If your peaks are 300W then your average level will be at least 10dB down unless you are using effects/distortion or compression which means an average of 30W. Since you don't say what amp or speaker or tell us the impedance of the speaker it is quite possible if it is an 8ohm speaker that you won't be producing 300W anyway. There is a risk but a small one the only way to be 100% safe is to use an over specced cab by 140%. It wouldn't worry me so long as the tone stays clean.

First of all you shouldn't get burning smells from a speaker cab. I think you said their was some discolouration of the fibreglass. If it isn't actually fibreglass but polyester wadding then this will singe even with speakers working normally at high power levels. You will have at least explained the smell. Move it around until it no longer contacts with the speaker. Neo's have smaller magnets so less area to dissipate heat. The easies way to test the speakers is to push some recorded music through them and listen at low volumes with your ears right up to each speaker one at a time and then with the volume up at a high level. If there is no obvious distotrion or funny noises then the speakers are ok. Have the closest look at your tweeter as this takes the bashing if you use overdrive. I can't think of anything that would cause a loss of gain without causing other problems with a power amp though I suppose a component failure around an op-amp in the preamp stages might change the gain of a stage. Tricky to find without the amp and a circuit diagram in front of you. There are two possibilities if it is the amp, it is actually ok and you just need to turn it up or you need a better tech. Don't worry about the volume settings between the amps though, that's al about gain and sensitivity and a halfway position on one amps gain control need bear no relationship at all with halfway on any other amp. There is an excellent piece on this on this site but you could look at this too [url="http://www.youtube.com/watch?v=EbVKWCpNFhY"]http://www.youtube.com/watch?v=EbVKWCpNFhY[/url]. Again if you play recorded music through the amp you should hear any problems as distortion. If you get the chance to try this then let us know what you find

[quote name='offom' post='722642' date='Jan 23 2010, 09:54 PM']I have an Aria Ab-25 and i feels buzzy when forcing the top strength strokes. I'm about to get a new speaker for it. Are car sound system based bass-subwoofer speakers suitable for such an application ? Any ideas or suggestions will be appreciated. Thanks.[/quote] No they are not the wattage ratings are almost never RMS which means they won't handle the power and the frequency response isn't good for bass either. In addition their efficiency is lower than most instrument speakers.

[quote name='Geek99' post='687954' date='Dec 18 2009, 04:21 AM']On talkbass wiki there is an article about queitening a marcus miller jazz. In it he advocates a separate wire to earth for each connection rather then each pot being chained to the next as standatd. Also says to de solder the earth tag of each pot and wire that to earth too. Would this nake a difference ?[/quote] Traditionally the best way to earth things is to use a star earth with each earthed item being taken back to a single point. This avoids any currents flowing along the earth wires and causing hum and noise. it increases safety and means if a cable breaks the earth remains secure on all the other connections. If there is a problem with noise on this bass it might well help.

your 4x10 with 300W should be producing peaks of 124 dB and be able to play at an average level of over 100dB which is loud enough to cause hearing problems. Something doesn't seem quite right.

The amp will give at least 150W into the 8ohm cab which should make it really quite loud. When you say it was worse with the old cab do you mean that it is worse now or that it was never very loud with the PA cab? Either way there are not many things that could go wrong with an amp that would make it quiet without making it very distorted. since you liked the sound it doesn't seem as if much is wrong. Try gradually turning the amp up full and trying different inputs if you have them. Also try changing your lead and trying a different guitar. Let me know how you get on.

Xmax (excursion) is fairly limited for a bass speaker and resonance is well above bottom E so don't expect thunderous bottom end. The frequency response promises a clean sound and the sensitivity is high so it would be quite loud for a single speaker. In other words you can't have everything but this speaker would promise the sort of response you say you are looking for and you can get it within your price bracket.