Phil Starr

Of course that is true though if you are running high levels of distortion then you can get to within a significant %age of these figures. Nevertheless heat remains one of the main reasons for failure of drive units and magnets do regularly reach temps of well over 100C in normal use. I know from the days when I manufactured speakers that their reliability and longevity was better without stuffing. Modern coils are much better than older ones at resisting thermal breakdown but why create a problem? In addition some manufacturers do publish figures showing the loss of power due to rising temperatures when operated at continuous high levels.

[quote name='Mr. Foxen' post='866195' date='Jun 13 2010, 05:35 PM']I know this one has been disproven, BFM has pointed this out a few times, apparently it lowers the box Q but not the other benefits of increased size, although I still don't know what that means, aside from it cleans up midrange, rather than adding bottom like a larger box would.[/quote] If you get a look at the Loudspeaker Design Cookbook there are a collection of Graphs which represent data from experiments with different levels of stuffing and differing materials. They show both the lowering of Q directly from the impedance curves and the changes in frequency response created by stuffing. At low frequencies they tie in fairly with the idea of a 10%'ish increase in volume. I don't have the data in front of me but the concept of the transmission of sound being slower in dense stuffing comes from work on transmission line cabs and the phase inversions at the exit ports. Certainly the speed of sound is different in different materials and this is something you can look up in books of constants. I'm not keen on stuffing high power cabs for an entirely different reason. All of the stuffings are also good heat insulators. Speakers only convert between 2 and 5% of the energy into sound the rest is dissipated as heat in the cab. A 500W speaker is radiating the same heat as 4or 5 large incandescent lights or a 500W electric bar fire. All this inside a tiny enclosed space. The back of a speaker magnet at full power will be hot enough to burn without any insulation. All this heat changes the resistance of the voice coil dramatically and the tolerances of every part of the system and the air inside the cab will have very different properties too. None of the thiele/Small figures will continue to hold true and the sound of the cab does demonstrably change if you push it hard over a long evening. Adding the weight of stuffing needed to change the characteristics of a cab will make these problems a lot worse and will also increase the chance of failure of the speaker quite dramatically. I'd need to be able to hear a great deal of sonic benefit to take this on. I suppose I just wanted to alert you to the controversies about stuffing which theoreticians will pursue never mind the more practical people you will come across here. You won't get definitive answers to this one.

Stuffing is quite a complex matter as there are at least three ways in which it affects the internal environment of the cab. Heavy felts and rubbers mass load the panels and reduce resonances and the bits behind the cone reduce reflection of sound out through the thin paper of the cone itself especially if it is thick and its surface is uneven. (The felt that is, not the cone) Fibrous stuffing in the air space behind the speaker helps to break up standing wave resonances especially if placed at the nodal points of such resonances. Finally filling the air space slows the transmission of sound which increases the effective volume of the cab by about 10%. If you get hold of the 'loudspeaker design cookbook' by Vance Dickason there is some extensive information on this. Having said this opinion is really quite divided as to the advantages of 'stuffing' and what the best materials are and how much to use. I guess the difference between bass and guitar usage is that bassist like their speakers to be more accurate than guitarists who depend upon reaonances to give a characteristic cab sound.

You've probably guessed that getting the old stuff off is the tricky bit. I'd just use a scraper and some judicious heat as the adhesive will just clog up sandpaper. I use white PVA adhesive to stick the vinyl on. Sticking it on the flat surfaces is easy and you can use a seam roller to remove air bubbles if you have to. Getting it to fold round the edges is much trickier; I use the adhesive on both surfaces and let it almost dry. then I heat the vinyl/tolex with a hot air stripper (take care) which makes it quite floppy and then I smooth it over whatever the problem bit is. If the PVA dries on both surfaces it can be melted with an iron and your tolex becomes iron on but be careful as a hot as opposed to warm iron will melt your covering. Where did you get the coloured tolex from? It is hard to track down.

[quote name='Bill Fitzmaurice' post='857879' date='Jun 5 2010, 12:46 AM']Not if they do it the right way, by reducing the number of windings on the same former. But your point is valid, not every driver manufacturer does things the right way, and you must pay attention to all the driver specs, not just impedance.[/quote] You're right Bill, there is no reason for this to be a problem other than keeping the cost of manufacture down by a few pence/cents but all the drivers I have looked at by Celestion/Eminence/Fane have gone down this route, more exotic manufacturers may have done this properly. I simply don't have the data to know if the 4/16 ohm units in commercially made cabs have been properly engineered. It is something I can get very grumpy about, the manufacturers must know they are selling these speakers which are sometimes not fit for purpose and usually to someone who thinks they are getting the same speaker but just in 4ohms.

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.