Phil Starr

There's a problem with most 4ohm drivers as well. they are usually made by just changing the voice coil for a shorter one which makes them less than optimum. typically the low level efficiency goes up at the expense of a much reduces excursion (Xmax) which means running out of grunt at higher sound levels. Another reason for not doing it.

You really need to try your speaker with another amp or another speaker with your amp to be certain of where the fault is. The speaker is the leading suspect but some failing capacitors could give you crackling at high levels. It is not unusual for one speaker to move more than another even if they are all working perfectly though if they do it probably means this speaker should not be in this cab for other reasons. Good luck

Actually I think a lot of this has to do with technology. When I started amplifier watts were really expensive and transistors which ran above 70V were unreliable and almost non existent. 100W was a big amp. Speakers were therefore made to squeeze as much sound out as possible with lots of big but lightweight cones which were loud but lacked bass extension. Now with FET's and class D amps watts cost pennies and we have more flexibility. Unfortunately guitarists watts are equally cheap and they can all afford to buy amps which make your ears bleed so we have to compete. The other thing is the improvement in PA's and monitors. We can be quieter on stage if we want and let the PA do the work. Hence all the metallists discussing 2x4x10's versus 8x10 whilst others pursue the ultimate lightweight solution. We are in the great situation of having choice so long as the rest of the band let us.

It also sometimes happens that an amp will start to oscillate without a load which could cause problems. It is one of those things that will probably be OK but isn't really good practice.

[quote name='stevie' post='848913' date='May 26 2010, 08:58 PM']It was a budget brand. I knew their PA speakers but I didn't even know they made a bass amp. They were well built though, with decent parts, but they were aimed at the lower end of the market. Your best bet might be to keep your eyes peeled for a secondhand unit. The current budget speaker best buys in the UK come from Fane and Celestion, both designed in the UK and built in China. I believe Phil has some recent experience of these.[/quote] It is the 10" Fanes that I have been using recently so no direct experience of the 15's. Very happy with the 10's so far and they are well made and meet their specs pretty well. If you go for Fane use the sovereign 15-500, the 15-300 is discontinued, the 15-400 would work in your cab and is cheaper but would compress the bass slightly more than the 500 at high volumes. Blue Aran have a single Eminence Kappa on offer at the moment which would just work for you.

[quote name='Mr. Foxen' post='847483' date='May 25 2010, 01:38 PM']The by all accounts very good Eminence Kappalite 3015 looks to be ok in this box, not gonna go really low, but it is the first thing I modeled, and it looks happy, I am supposing the port is a round one? If you can get another driver much cheaper, might be better with one of those, you'd be wasting a bunch of the potential of the kappalite.[/quote] Yep the kappalite looks good for this cab and it does have a nice little peak. If you can put up with a bit less presence and a bit of boom at the bottom end then the Fane Soveriegn 500 would just about do the job. Blue Aran are good suppliers.

Just to save anyone else needing to do the calculation the cab is 52litres. this is fairly modest for a 15" speaker so you are probably looking for something with a fairly decent magnet if you want a tight non boomy bass. Try reading this as a start [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] You sound as if you quite like the tone of the speaker you have so why don't you stick with it whilst it is reliable the only speakers I can find quickly that would be happy in a cab this size would be the Celestion BN15-400S or one of the Peavey Black Widows though I am sure that there are others. Of course it is not unusual for manufacturers to compromise the cabinet volume for convenience and for people to be happy with the sound. It would be interesting to see a pic of the current speaker to see if the magnet looks adequate for the cab it is operating in.

[quote name='Bo Millward' post='845843' date='May 23 2010, 04:21 PM']Cheers for the advice man, if I partition the cab inside so each speaker is loaded in its own sealed enclosure would that help to prevent this? (Oh, and add ports to each section)[/quote] I quite like partitioned cabs because they stiffen up the structure and reduce the interaction between two speakers however this won't solve the problem of the cabinet volume. I have done this by removing the back of a speaker and then putting a new back in place a few inches in front of the old back which I then put back to cover up what I had done. this makes the cab quite heavy but since the outermost 'back' is just cosmetic you could use a very thin panel. Sorry I was a bit negative about your speakers but if you like the sound then they are good and if it is the sound you want then you should trust your ears and not some techie advice. Thinking about what you are trying to achieve though it would be quite interesting to use just one of the Celestions with a partition inside the cab and then another 15 with a better midrange/top end in the larger top half of the cab. I don't know how you are getting on with WinIsd but if you are having problems I'll try and give you a hand with design.

your finished speakers are going to be overdamped which means that the bass, whilst going deep, will be somewhat squashed. With a Qts of 0.24 damping is very high and the speakers are designed to be used in a smaller box than the one you are going to put them in. Although the bass promises to be clean and have good transient response I suspect they wont be the bass monsters you are hoping for. In addition the lack of response above 2500Hz will mean that they will lack articulation and the ability to cut through the mix

[quote name='Ruck' post='840163' date='May 17 2010, 08:38 PM']Thanks for the suggestion, Im currently getting a second opinion from another techy but if he says the same about needing a replacement driver I might try fully removing the dustcap. Whats the best method for this please?[/quote] There's no magic method just work it loose a little at a time work round gently from the loose bit.

If it is any help I've found that when a dust cap comes loose the only way to fix it is to take it right off and re glue it all round. Just tackiing back the loose bit never seems to work. However pressing on the dust cap doesn't just move the dust cap so it may be a coil scratching which does mean a new speaker. You may be able to get it re-coned though which may only cost £40-50 if you can find someone to do it. I use copydex to re stick loudspeaker parts.

I used a Black Widow in my 1x15 and it does sound good. Clean bass and great top end for a 15.

[quote name='Bill Fitzmaurice' post='828743' date='May 5 2010, 06:05 PM']60l is adequate for twelves with Qts of .4 or less. As for the perception of low end response, the human ear is very inaccurate; most people are about an octave low in their estimates of the frequency they're hearing. Low 'B' players who swear they're knocking down walls with 32Hz output are actually hearing the 2nd harmonic at 64Hz. Good thing, as otherwise even a Fridge wouldn't be up to 5 stringer needs.[/quote] so true,try to get the chance to listen to a 32Hz sine wave through your speakers . If you hear it at all then you'll be amazed at how low it sounds. [quote name='Mr.T' post='828812' date='May 5 2010, 06:55 PM']Does that mean it's Ok for me to think that my new cabs sound good? [/quote] theory is great but if it sounds good; then it sounds good!

[quote name='LawrenceH' post='825507' date='May 2 2010, 02:07 PM']The Celestion Xmax figures are not comparable to (e.g.) Eminence or B&C, they are more conservative as they use a different method to arrive at the figure. They calculate Xmax the old way, which is (Voice coil winding width - gap height)/2. Alexclaber has posted figures showing that, for comparison to Eminence drivers (and presumably other manufacturers such as B&C), a more accurate calculation would be (Voice coil winding width - gap height)/2 + (Gap depth/4). This gives much more respectable numbers which I understand equate better with real-world performance. The Celestion BN10300X has a whopping Xmax of 6mm using this method, while even the Orange label series have Xmax of 4mm, directly comparable to a Deltalite II. The NTR10-2520E gives 6.75mm, making it on paper probably the best option on the market for really tight true bass from 10" drivers. The Celestion 10" units have notably lower Vas values than the Eminence Deltalite II, and combined with the high extension capabilities this means (at least for the green label and NTR) that you can put them in a smaller box and get reasonable bass, or you can put them in a big box with a low port tuning to extend the low end and they'll still be limited by thermal constraints rather than Xmax. Some B&C drivers give similar performance to the Celestions but are more money. I am hoping to do a DIY ultra-compact 1x10" build using Celestions, a bit like the one posted on here a few days ago but out of 12mm lightweight ply. I'll go with either the BN10300X or NTR10-2520E depending on funds and deciding whether I prefer the more balanced tonality of the NTR. Having said that, I do wonder how good the Orange label might sound with their extended top end - surprisingly nice, I'd bet, despite the (relatively) restricted low-end capability.[/quote] I wondered if anyone would pick this up. The alternatives are to measure the phsical dimensions of gap and coil os Celestion do or to measure the excursion at a set level of distortion, usually 10% which is where it starts to be audible. How quickly the sound becomes compressed as the coil leaves the magnetic field does depend upon the relationship between coil and magnet depth as well as gap geometry. I don't care much about which method is quoted but it would be nice if everyone stuck to the same method so we can make comparisons. Using Alex's method gives Xmax of 3mm for the Celestion BN10300 by the way. I'm hoping you go for the Celestion BN Lawrence. I can't believe Celestion of all people haven't tried out their designs but it is so off the wall to make a bass speaker that has a resonance at 77.9Hz and a much higher f3 in a cab that I chickened out of trying it and went for the Fane10-275 in my latest cab. It gives a lovely tight controlled sound but won't set the world on fire without a livelier top end.

Ooh I love a technical question. most speakers are designed as 8 Ohm units so a 3x8ohm will be 24ohms in series or 2.666ohms in parallel. so not good for most amps. secondly a line array speaker has two characteristics that dominate their performance. They reinforce each other in the horizontal plane and cancel in the vertical plane giving a broad flat radiation pattern. This is ideal for PA as controlling the direction of radiation this way helps you reach the back of an auditorium which is why in the seventies it was a dominant design. The disadvantage is that speakers mounted close together interfere with each other if the distance apart is a multiple of the wavelength of the sound they are radiating. This is in the mid frequencies and you can get lots of lumps and bumps in the frequency responce and some 'interesting' phasing effects as you move your head around. Of course any multiple driver cab will suffer this effect a little. So the design of such a speaker could be challenging and you could get similar results with say a 2x12 which would have the same cone area and could be made with a lighter cone to achieve similar results. Alternatively you might well get a better result with 2 better quality 10's costing the same as 3 lesser quality speakers without the problems. However all speaker designs are compromises and there is no reason why you couldn't design a successful 3x cab albeit with strengths and weaknesses.

First of all it can be difficult to pin down exactly where a spurious noise comes from in a speaker. anything loose in the cab might make a strange sound. Check that the speaker is screwed down tight and that nothing in the cab is loose even a loose cable inside the cab can rattle check the grille too. Then check the speaker itself, the glues that hold it together can break down with age The dust cap in the middle is most likely to go followed by the joint between the surround and cone. These can be successfully stuck back with copydex which is a latex based adhesive. If the speaker is blown contact Ashdown who seem to be pretty good on after sales care. If after all this you want to replace the speakers be aware that you can't just drop any speaker into any cab and expect the bottom octave to be any good. Each speaker needs to be in a box of optimum volume depending upon the weight and stiffness of the cone and the size of the magnet and coil. in addition a ported cab has to be tuned to the speaker with a fair degree of accuracy. The Fane 10-275 for example needs a smaller cab than the Celestion BL10. I've got reservations about the Celestion bass speakers (BL and BN) because of their restricted Xmax and the high resonant frequencies (based entirely on their specs). Stevie do you have any experience with these speakers as I am curious as to how they sound?

Speakers and cabs have to match. If a cab is too small you get a bass hump, lack of damping and the bass cuts out before it should. Too big a cab and the speaker will be overdamped and the bass will go low but at reduced volume. If the cab is a ported cab then it will simply not be tuned to the speaker you put in unless you are prepared to modify the cab or you are very lucky. by choosing the drive unit carefully you might find one that matches your cab quite well and if it is sealed or you are prepared to block the port then you have a reasonable chance. You can repair your speaker by using Copydex or any other similar latex based glue and the repair can be built up with layers of tissue laminated with copydex though it sounds as if you just need to stick two bits back together.

The cab was wired up in a mixture of series and parallel, if any of the series wiring is missing then you might well have a broken circuit and no sound. Since we don't know what has been done when the speakers were removed we can have no way of being certain.

Fane sovereign 6-100 might do or the Eminence alpha but ampeg originals would be best

[quote name='northstreet' post='785103' date='Mar 24 2010, 09:22 PM']Thank you for all comments received, whether sensible or not. I've now been told that the ticking is coming from the cab itself - ie not the speaker - but the actual box. I guess that means there's some sort of structural failure - a glued joint broken or something, and it's moving in sympathy with the speaker. Which is probably why the speaker has started to fail as well! I'd like to try a repair (on the basis that if I can fix it it's cheaper to buy a new speaker than it is to buy a whole new cab), but has anyone come across this before and have any ideas of where to start. Or should I just give up and bin it? More bomb jokes are always welcome.[/quote] If it is just a matter of sealing the cab then you can do this by applying a bead of acrylic mastic (decorators caulk) and smoothing it with your finger. If it needs mechanical fixing then cut a length of 25mm square batten and glue it in with white woodworking glue and a few screws to hold it in place.

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.