Phil Starr

I'm not a good bass player. You probably tear your hair out when you hear people like me playing in pubs. You know the sort of thing; plays the root in time and has copied the odd bass line from the tabs, and that on a good day. I started playing as a middle aged adult from scratch 4 years ago, went straight into a band so the bassist could move on to other things and was playing pub sets of 2 hours in just over a year from playing my first notes. My learning experience has been a desperate scrabble to learn the next song for the next rehearsal and gig a week later. This means that I have seized on what works with no attempt to master theory or scales. Not that I am averse to a more thoughtful approach I just haven't had time to get off the merry-go-round. Currently I grab the chords play in the root a lot and have found the fifth, minor seventh octave and chromatic progressions are my friends. I'm just starting to play with the major and minor pentatonics. I tend to think in terms of box patterns rather than scales, so most of the time I don't even know which note I'm playing, just where they are relative to the root. I never improvise except when working on a new song and never live. I've never had a lesson in my life. So that's me. Where do I go next?

[quote name='alexclaber' post='1358557' date='Sep 1 2011, 10:50 AM']Your conclusion that you prefer 15"s to other sizes is flawed because you can't accurately group the sound of speakers by woofer size. It sounds like you prefer smoother, fatter cabs - doesn't matter what size speakers you use to get that sound as long as you get that sound![/quote] [quote name='bobpalt' post='1358980' date='Sep 1 2011, 04:47 PM']Now I'm getting really confused!! Bob[/quote] [quote name='51m0n' post='1359351' date='Sep 1 2011, 11:29 PM']Nope, you are very misguided, diameter has nothing to do with tone at all.[/quote] It can be confusing but sometimes over simplifying doesn't help. I'm a bit worried that the OP is being told that size isn't important and that nothing in the 'Physics' makes it so. This just isn't true. Large cones shift more air and are generally more efficient than small cones. If they are the same thickness they will be heavier and have a lower resonant frequency, if they are are thinner they will flex more and give more (but probably uneven) mids and tops. You can make a small cone reach lower down by adding mass with a thicker cone but this will reduce the higher frequencies and the efficiency. A small cone needs to move further than a large cone to produce the same absolute sound levels at low frequencies and I won't go into the problems of radiation patterns and multiple drivers. There are certain things that are easier with a 15 and other things that are easier with a 10. There are also ways round the 'problems' of designing a cab around either. There is a tendency for 15's and 10's to have similarities but no iron laws on their overall sounds which depend upon so many factors. This is why Alex said "you can't accurately group the sound of speakers by woofer size." and went on to say "doesn't matter what size speakers you use to get that sound as long as you get that sound!" He was being careful, it is not that all 15's have a 'sound' but that ultimately you need to not have preconceptions and just listen to the sound a cab makes. He was also telling you to trust your ears. Sometimes the careful, thoughtful advice gets drowned out by the categorical and though a bit of technical knowledge helps you should really trust what you hear when it comes to tone.

If your amp is 200W into 4ohms stereo it will give 400W bridged into 8. It may well also give 400W bridged into 4ohms. This is because of the power supply. Solid state amps are limited by the voltage they run at. Running them as a bridge means the voltage is effectively doubled which theoretically gives 4x the power (power is Vsquared/R). In practice asking them to provide masses of extra power demands a lot more current which could damage the output devices or more likely simply demand more than the power supply can provide. Protection circuits may cut in too. Running bridged into 4ohms is much like running an unbridged amp into 2 ohms. You might be trying to draw more power than the amp is happy with and may in extreme cases damage it. You need to check the handbook as each amp is designed differently. Generally the more expensive amps have bigger power supplies, better output devices and better protection though you don't always get what you pay for. Power supplies can always provide high currents for brief periods. This enables some manufacturers to claim greater power outputs than the amp could manage over an extended period even if they are 'RMS' values.

Just so you know. The hole in your 15 is a port and it is meant to be the thickness of the board. The hole and the air trapped in the cab act as a tuned circuit and are tuned to a frequency which matches your speakers. if you added a tube it would be tuned to a different and worse frequency. If you wanted to port your 4x12 then the port would have to have exact dimensions to tune with the volume of air in the cab to match your speakers. Ideally you would also have to change the volume of the cab to match your speakers. The magnets on your speakers don't look huge and they are probably high Q speakers not particularly suited to reflex loading (ported cabs). I'd always encourage people to experiment with building their own cabs but you aren't going to improve these with a jigsaw. Speaker design isn't rocket science, but it is a bit complicated and it does involve maths and science unless you get a ready published design. If you start hacking bits out of your cab it is going to reduce it's value and probably make it sound worse unless you are prepared to spend a few months reading up about Thiele/Small parameters. I'd start experimenting on something a bit less valuable. Cheers

[quote name='fatback' post='1306026' date='Jul 16 2011, 05:35 PM']Presumably it's the longer scale length that's allowing for the different harmonics? How does that work?[/quote] A double bass is pretty complex acoustically. The string sits on a bridge which excites a resonant chamber. Movement of the bridge will damp the movement of the strings killing some harmonics quicker than others. The front face of the bass is under a bit of tension and will have its own series of resonances and the body of the bass forms a helmholtz resonator which will again have a resonant frequency. there will also be resonances and standing waves inside the cavity which is highly reflective and probably considerable sound contributions through the back and sides. Add in the possibility that the strings could be made from nylon, gut, polyester steel or some sort of hybrid and would in any case be different in construction from most electric bass strings and you can see there are plenty of reasons for the different sounds. [quote name='Mr. Foxen' post='1306369' date='Jul 17 2011, 02:07 AM']The ratio of harmonics depends pretty heavily on the sampling point I think. As in the pickup position.[/quote] Absolutely and also the point where the string is excited/picked. [quote name='stevie' post='1306453' date='Jul 17 2011, 10:14 AM']It's not a reflex cab. It's a Helmholz resonator - it more or less says so on the drawing. It has more in common with a classical guitar than a ported cabinet.[/quote] [quote name='stevie' post='1306601' date='Jul 17 2011, 12:55 PM']A reflex cab contains a Helmholtz resonator, which is the vent, but a reflex system is more than just the vent. This design seems to rely solely on the vent to produce sound - just like blowing over a bottle. The contribution from the rear of the driver would be what you would expect from a driver in free air (or from the air blowing over a bottle)- practically nothing. I think the only reason the driver is not boxed in is because it would raise its resonant frequency. However, if you imagine this system with the driver boxed in, it starts to look very much like a bandpass system.[/quote] I love these old cab designs, I don't think the designers knew themselves how they worked half the time. Reading the article in the link about adding weighs to the tone arm to extract more subsonics and needing to protect the room from the speaker reminds me of some of the loony articles more recently written about cables in hi-fi systems. For what it is worth, to me this is an attempt to get 'free' bass from the resonace of the cavity and to couple them along the pipe. The air space between the speaker and the cab would decouple the resonator from the speaker to a fair degree so it wouldn't act as a reflex cab in the conventional sense. I wouldn't want to have to do the maths to see how much of the pressure from the speaker went into the cavity and how much straight down the 'horn'. You could equally argue that the 'horn' would act as a port for the air space and you might with the right bit of luck get the resonances to work as a coupled design. Alex is right that the back of the speaker would radiate sound in the same way as the front but it's dispersion would be interesting with the basket and magnet in the way. The 'horn' would have its own resonances and also act as an acoustic filter losing almost all the high frequencies and selectively some of the lows. The design would be very sensitive to changes in the driver and to the way it would couple with the floors and walls of the room all things the designer alludes to. I suspect this speaker would have had a large resonant hump which would have been very satisfying at a time when very few speakers had any real bass, a bit like the in car systems the kids install, but not very accurate. I picture the owner only listening to 'Zarathustra' and the intro to the Toccata and Fugue in Dm so they can hear that lovely resonance. I love Basschat.

[quote name='Bill Fitzmaurice' post='1303817' date='Jul 14 2011, 05:41 PM']You may still be hearing a lot of harmonics, as your speakers create them. If you play a pristine 40 Hz or lower sine wave through a capable speaker with very low THD you can't even discern pitch.[/quote] Fair comment, I should have said there is little point in doing this with your computer speakers. Even with decent hi-fi speakers you will get some audible harmonics but it does give you an idea of just how low the fundamental of bottom E is and it's usually a shock to people who hear it for the first time.

Bill is right. Funnily enough I was driving home today listening to Lou Reed's 'Walk on the Wild Side' and I thought If anyone asks this question they should listen to this. The Bass sounds amazingly deep because it is played on an upright, even though the bottom frequencies are no lower than a four string the different mix of harmonics gives it a rich deep sound. There are loads of signal generators online and if you are deeply boring (like me)it is quite interesting to listen to a 40Hz (roughly bottom E) pure tone and realise just how low that is. If your speakers can go that low of course.

the easiest way to test your tweeter/horn is to put some recorded music through it. You should be able to rig up a lead to feed your iPod into it or even connect it to your hi-fi in place of one of the speakers. Cymbals have a lot of high frequencies so if you can't hear them then you know they aren't working. Check fuses and trace the leads back to the socket via the crossover to check there are no broken connections, then get on to Ashdown who are very helpful. Good luck

[quote name='Mr. Foxen' post='1293074' date='Jul 5 2011, 09:16 AM']All that is wrong. Watts don't mean anything, and ohms mean not much, the bit that matches drivers to cabs are another set of specifications entirely. Predicting how speakers work in a box without actually trying is quite difficult, but if you throw up the box dimensions (ideally internal, it is the amount of air in the box that is important), and where the box has a port/vent/hole in it and how big that hole is, some people can make some more informed decisions.[/quote] [quote name='brensabre79' post='1293209' date='Jul 5 2011, 11:36 AM']I beg to differ. Its not just about matching cabs to drivers... put a 100w 4 ohm speaker into a 200w 8 ohm amp and you will soon see, the power will be too much for the speaker and the amp will be underloaded. result, blown speaker, blown amp. Having said that, there is more to speaker/cabinet matching than just chucking in any old speaker. If your cab is an ashdown (don't get me started) then the best replacement would be an ashdown speaker - the cabinet is designed for this. Although in a 2x10" most are quite similar in size. Yes you may need to adjust the port length for the particular speaker to get optimum results but the end result of using a mis-matched cab/speaker combo is purely the frequency response which you can compensate for with EQ to some degree. The result of using a mis-matched amp/speaker combo is you could either underload or overload the amp and speakers and lose both![/quote] Mr Foxen is right and up to a point so is brensabre. A replacement needs to match the amp in watts and impedance but only in the sense that it needs to be able to handle the power. You can use 250W of speakers with a 200W amp or even 1000W of speakers with a 5W amp but not the other way round. Anything with an impedance of 4-16 ohms is fine with a solid state amp though you may lose a little volume/power. If the amp is a valve amp then you need to match the impedance and if you use this cab with another it needs to match that in impedance ideally. The speaker also needs to match the cab though. If the cab mismatches then you might need more than eq. and you might lose a bit more than just the sound. If the cab is tuned to the wrong frequency then the speaker may effectively be unloaded by the cab and may suffer excessive excursion and an early grave. This is especially true for a ported cab. Check the amp and everything else first, if it is definitely the speakers then ideally contact Ashdown and replace like with like. They are really helpful and reasonably priced. If for some reason you decide you want to replace the drivers with something different someone here will help you re-tune the cab, but there is a better than even chance the original speakers will sound nicer.

Well Done!

OK I think your problems are becoming clearer. I guess you don't have a lively used market in Greece and the same access to cabs to try out, something we take for granted in the UK. This makes building relatively more attractive. It's not as hard to design your own cab and come up with a successful design as some of the experts will tell you (they have a position to protect after all) but neither is it something you can do without considerable effort and the risk of an expensive failure. In fact it is fairly unlikely that you'll get the tone you want with a first attempt. If you want to learn speaker design you have to start somewhere so learn as much as you can and go ahead. It looks however that you actually just want a good all round cab to play through without spending a fortune. Correct me if I'm wrong but I don't think you really want to spend months learning how to engineer speakers. You really need to use an established design where someone else has done the work, designed the box and chosen the drive units. Eminence have designs on their website and you have the fearful designs, there are loads of designs if you care to trawl the web and plenty of build diaries on this site. You could also copy a speaker you like so long as you stick to exactly the same drive units. I hope you understand that the box and the speaker work together and that you just can't put any speaker in a box and expect it to sound good. Your builder needs to have exact dimensions if they are to do a good job so you are more likely to be successful if you use one of the designs which gives a lot of detail. You also need the details for any crossover I think it would be sensible to look at using a fEarful design. Price up what it would cost and then what a commercial speaker would cost including shipping (Thomann don't charge for shipping to Greece over 300euro). Then make your decision.

there's nothing much wrong with either of the speakers you suggest at the price, I'd go for the 15-400 by the way. Going neo won't change your sound per-se but there are some well regarded speakers out there that happen to be neo. You have to decide if you want to save your back and lighten your wallet! My 15 has a Peavey Black Widow in it which I picked up cheap. Nice sound but pricey, Peavey's box was all wrong by the way. Another 15 I've used is the Fane 15-500 which is great value. It's probably aimed at PA rather than bass as it behaves pretty well at cone break up, basically it has a more even response at the top end than the speakers you mention, but if you are going to use a 6 as well then that might not be a problem. It should have a more accurate bottom end than the other two speakers.

Now you have to tell us how you got on. I'm thinking of taking the plunge myself but the possibility of total humiliation is a bit daunting. The experience of someone in the same position would be great. (the lessons not the humiliation)

[quote name='Monckyman' post='1282252' date='Jun 25 2011, 04:37 PM']Thanks for the reply, yes I understand how it may be the context that`s emphasising certain freqs, and I can cut them reasonably well on the amp eq. I`ve asked a P.A firm friend to see if he has something knocking about that I can try out. I`m fully expecting to be proven wrong but it`s just an idea I want to try. MM[/quote] a good quality LPF isn't going to be cheap and without some way of measuring you could end up trying at the 'wrong' frequency to get the result you want. If your PA friend can lend you a stereo amp and an active crossover you can try different frequencies and different roll off slopes really quickly, then you can decide what frequency you want to crossover at and whether you want to use a high pass filter on one cab a low pass on the other or a full crossover. Use your bass amp as a pre amp if you have the right output (but use a dummy load if it is a valve amp). Have fun

assuming your cabs are all 8ohms you have it right. There will be no problems with power handling with what you suggest. The easiest way to rig up speakers in series is to wire up a special lead or adaptor box. Any competent repair shop should be able to do this. I don't know of any commercially available leads.

basically if you have four speakers in a square then the sound will be beamed in a cone which narrows with increasing frequency whilst placing them in a line will radiate sound in a broad flatter beam. This is going to be better in most auditoria because more of the audience will hear a better balanced sound with more mids and highs. Also having a speaker close to a hard floor will increase bass output by 3dB which could be good or bad depending upon what you are trying to achieve. It is also good to have a speaker at ear height as then you will hear more mids and highs which you need to hear what you are playing. You also hear a sound which is closer to that which the audience hear. Alex Clabers article is really worth a read. If it is possible I'd always stack vertically

Good to hear you are getting the sounds you want, I hope we helped a little. Careful about fiddling with vents though, it can get addictive.

[quote name='Nostromo' post='1274087' date='Jun 18 2011, 08:28 PM']Thanks for all the input so far guys . . . . I guess it gives me a lot to think about ? . . . . Must say, I haven’t got access to, or the knowledge of, WinISD Alpha Pro so not sure I'm likely to be able to employ anything like a computer program to any advantage, but I do take the point that it could produce a more optomised cab design/environment for the speakers . . . having said that I wouldn't know what effect that would have on the sound/tone/character of the cab ? . . I guess we all sort of know that basic sound that 2 x 15"cabs tend to have . . . and I sort of like that old vintage sound . . . and that’s definitely what I'm after here ? Obviously I'd like to create a cab that presents a good environment for those drivers to sit in . . one that would let them sound their best and operate properly ? . . I hadn't realised that the 70's cabs were developed with so little technical input . . sounds like it was more luck than judgement if they sounded good ? . . . I do like the picture posted up by Mr Foxen . . . thats the sort of thing I had in mind I think ? So, what gives that 70’s tone ? . . . is it the speakers themselves or the (sometimes badly designed) cabinetry ! . . . I’d definitely like to get a 70’s sound from this cab, thats the whole point of the exercise, but if a seventy’s design can be tweaked a bit to allow the speakers to perform even better without loosing the 70’s character then that would be worth doing I think ? . . . Not sure where to go next now ! . . . Further comments much appreciated ! [/quote] WinISD is a free program which google will find straight away. You probably need to know a bit about speakers to drive it though. AJ systems offer a simpler though less flexible box caculator which will offer optimum box sizes. The basic theories of box design were first published in the early 70's and many designers didn't pick them up until later so almost no cabs sold then were designed using the Thiele/Small models. In addition materials technology was developing so drivers got better. At the beginning of the decade most amps were valve amps with a very high price per watt. Speakers were usually general purpose designs with paper voice coils and low power handling. Magnets were small and often lost a lot of there power over time. There were very few horn tweeters around and these were expensive and unreliable. Most speakers tried to cover the whole audio range and tended to have thin flexible cones often with a second 'whizzer cone ' in the middle of the main cone to boost the higher frequencies. To get the most out of the low powered amps the voice coils tended to be short to boost efficiency and suspensions were often soft to lower the resonant frequencies. All this meant that most speakers were in boxes that were often too small and that the designs were often under damped meaning that you got a nice warm bass frequency hump at the expense of deep bass. Distortion set in early because of the lack of excursion and the only way of getting deep bass was using big speakers (2x15) or lots of them (8x10). By the end of the 70's glass fibre coil formers were creeping in and large ceramic magnets were common and designers were starting to use maths to design cabs though remember computers still used punched cards in the early 70's and pocket calculators were just being introduced. I was still using a slide rule and mechanical caculators at University. Bill is right, you'll get a better sound and more quickly without the error part of trial and error if you use a computer modeller. the seventies procedure was to listen to a lot of speakers so you knew the basic sound of each driver and then to keep building cabs untill you'd home in on the sound you wanted. Sometimes you had a lucky accident. Your best bet is to copy an earlier design where someone has done all this for you. Most of the 'character' apart from deep bass will come from the drivers. Good luck, let us know how it turns out.

Duvets and pillows are stuffed with polyester wadding which is the same as most of that sold for speakers I use it sometimes. Mostly I use higher density materials for PA/instrument cabs, Glassfibre or Rockwool. the disadvantage is that you rally have to keep the dust out of the voice coil gap. Even the commercial wadding does 'bugger all' unless you really pack it in though it works better for hifi designs.. I don't usually stuff reflex cabs, restricting myself to just trying to prevent internal reflections off the back panel. the advantage of a wedge is that the rear panel doesn't run parallel to the speaker so the primary reflection doesn't go straight forwards back through the cone. I'm agnostic about the benefits of stuffing, people get very nerdy about it wanting the long hair wool from mountain sheep sheared on a full moon in July. Having done a lot of A/B testing of my own designs I'm not convinced it adds a lot and I miss it out except for dealing with specific resonances or standing waves. Others will disagree. Gio for whatever sounds best unless you have acces to a lot of testing equipment,

If both cabs are the same size then replace the corners with ones that interlock, which most of the plastic ones do. Available from Maplin or Blue Aran amongst others.

Stuffing a cab is an interesting one, there are loads of theories around and you probably need to distinguish between damping the panels and stuffing the air space. On the panels it can reduce the internal reflections and mass load the panels reducing their resonance. In the air space it will affect the propagation of the sound, dampening standing waves and changing the effective volume of the cabinet, If you can get hold of a copy of the Loudspeaker Design Cookbook by Vance Dickason their are some nice measurements of the effects of differing stuffings upon the performance of cabs. One of the less well advertised effects of stuffing is that the speaker doesn't cool down so well if it is surrounded by a load of wadding/fibreglass.

[quote name='LawrenceH' post='1266138' date='Jun 12 2011, 02:58 PM']To match your point of order, accepted acoustic engineering practice for musical instrument cabinets has different design goals and acceptable compromises to hi-fi style cabinets designed for accurate reproduction. In the context of a budget alteration to a bass cabinet Phil's comment was a fair enough reality check, from his other posts it's clear he understands why there are limitations to mixing drivers - the physics behind it is something a child could understand (and yes, I have demo'd wave cancellation/reinforcement at a science festival for children). But from a practical perspective I've certainly never had serious problems mixing different bass cabs that were caused purely by phase compatibility, that weren't dwarfed by the usual limitations of playing in enclosed spaces or the inherent voicings of the speakers themselves. It's typically not nearly as a big a problem as having crap drivers or a poorly tuned cabinet and certainly not the deal-breaker it's sometimes made out to be when considering straightforward upgrades. In fact, mixing drivers often has the subjective effect of smoothing out the mid-range which can be beneficial. I don't understand the need to be so combative about these things. Your own cab designs contain many compromises from the point of view of convenience/cost some of which go directly against 'accepted acoustic engineering practice'. Not least arrayed tweeters spaced greater than 1/2 wavelength for much of their operating range. Yet you count yourself an acoustic engineer, understand the compromises and for you and the majority of your builders they're acceptable. Oh btw Phil was saying he is both 'old' and 'an acoustic engineer'. Hence 'both' in response to your 'neither'[/quote] Thanks Lawrence. I'm tempted to say 'leave him, he's not worth it'. The only reason I raised this is that advice from 'technical experts' is sometimes not that helpful and if it is too categorical it is often incorrect. Ultimately speaker design is about compromises even when you are designing for hi-fi and PA. When you are designing for musical instruments there are many more compromises which can give results some people will like. the idea that everyone who has ever used a 15 with a 4x10 was wrong or that all your speakers should be from the same manufacturer is a little odd. To claim that this is due to the laws of the universe and that anyone who disagrees can't possibly know any engineering principles is stretching things a little too far. Oh well. For anyone following this I'd say that mixing speakers is a bit like blending drinks. If you mix Cabernet and Merlot then you will lose some of the character of each. You get some mid range smoothing, but some people like Cabernet/Merlot. Cheers

I'm now feeling a bit guilty about not answering your original question and let some of the other posts distract me. The cab size will suit quite a range of drivers though you will need to adapt the ports. I gather you are just trying to fill out the bass a little so top end is less important. Do you have a budget in mind? If you find other drivers in your local shops tell us what they are and if the TS specs are available someone will advise you how to modify the ports. I'll look at drivers when I get more time. Gigging tonight.

[quote name='Bill Fitzmaurice' post='1263395' date='Jun 9 2011, 10:43 PM']And old acoustical engineers. From your response I gather you're neither. The advantage to identical drivers is that you always know what you'll get. With mixed drivers you never know what you'll get until you've got it, and that can turn out to be an expensive experiment.[/quote] How rude. and I'm both.

All this stuff about not mixing drivers is just an old wives tale. The 'character' of a speaker is largely about frequency irregularities asnd if you mix drivers these are not likely to coincide so you might lose some character, but some characters do need a little turning down at times. There are problems with any multi driver set up too but this is as true of identical drvers as differing ones. Some combinations work and some don't and some of us like a coloured sound and some don't. You have to listen to judge whether a particular combination will work for you.