Phil Starr

First check your leads. the connections to the plugs fail far more often than the sockets. You can clean the contacts in the socket with a contact cleaner aerosol like Servisol but this will be a temporary fix. If you play live you owe it to your audience to take gear you know is reliable so you have to solder in a new socket. If you can't solder you have to pay someone else to do it. This is the sort of thing you only have to do every few years and it costs no more than a decent set of strings. Sorry

[quote name='stevie' post='1012492' date='Nov 4 2010, 07:51 PM']Yes. Because you're likely to blow your amplifier up if you don't. You could try a 47uF bipolar cap in series with the top cab, which should maintain the system impedance at 4 ohms. Pm me your info and I'll send you one. No guarantees, as you really need measuring equipment to do this properly.[/quote] Good advice. This will filter out the signal at about 400Hz at 6dB/octave and a reversible electrolytic will only cost £1ish (go for 100V rating) so you can afford to try it at little cost. You could use lower ratings for experimenting with if you don't crank up the power. I'd give it a go and try fiddling. Buy a handful of capacitors and try adding them in parallel until you get the sound you like best. Doubling the number will double the capacitance and halve the cut off frequency. If you've some speaker leads with bare ends you can wire this all up with 'chocolate box' connector strip whilst you are fiddling. If you have access to an electronic crossover of course you can do this more easily. Of course BFM may be right and this won't give you a better sound but without trying we are all guessing. Cutting the bass to the tops this way will increase their power handling within the system and will raise the overall impedance, dependant upon what frequency you end up with. Cutting the bass will cut the bass (duh) and make the mids stand out more. This may be good or not, there is only one way to find out. reversible electrolytics are getting harder to find, Maplin used to stock a wide range, also search for non-polarised electrolytics.

I've gigged with a 1x12 PA speaker in a smallish venue and it works. Clean sound and you don't overwhelm the rest of the band. I also gig regularly with a single 15" fitted with a Peavey Black Widow and a couple of piezo's, no problems at all. I've also been known to just use my 4x10 as a stand for the 15 leaving the 10's disconnected. We're not a metal band though.

Sorry I can't resist a good nerdy thread. There isn't a single solution to the problems posed by speaker design. All designs are necessarily compromises. Even a 10" speaker doesn't go high enough in its piston region to successfully reproduce the upper harmonics necessary for a decent sounding bass guitar and just about every instrument speaker I have seen is operating under cone breakup to reproduce the upper frequencies. Since most of the character and perceived 'loudness' of a bass speaker are all about what goes on in the midrange how a speaker behaves under breakup is pretty important. Even at the bass end size is only one factor. To go deep you need heavy cones but this lowers efficiency because you have to accelerate a bigger mass. The volume of air you shift is important and you can make a smaller cone shift a lot of air if you make a speaker with a good excursion (Xmax) but this means a long voice coil which lowers efficiency. It also lowers the damping of the speaker and affects transient response. Very little of the speakers energy actually makes any sound. Most instrument speakers are between 1% and 4% efficient, The big problem is that the air in front of the speaker presents a very low impedance to the speaker. Bigger cone areas increase the efficiency of this coupling of speaker to air as do horn enclosures like BFM's but to work properly a horn needs to be vast (16 feet across for low B!). So all things being equal a bigger cone area will give louder bass than a small cone and you can't completely compensate with a bigger excursion. You can compensate with multiple drivers or a horn cab but these bring other problems. I love the uncertainty. There are so many ways of solving the problems of speaker design and each only opens up other problems and compromises. Anyone who tells you they have the answer is kidding themselves, the only test that matters with an instrument speaker is do you lke the sound? The science will get you 2/3rds of the way there but there is still no substitute for a listening test.

If you are thinking of building a 1x12 then consider the Beyma SM212 which is a bit of a gem. Cast chassis, reasonable efficiency, good frequency response with well controlled cone break up and at the price a fantastic Xmax (cone excursion). Oh, and it sounds great with a bass. I can send you dimensions of my cab if you want.

every room has different acoustics and this really affects bass frequencies most of all. If you have walls, ceilings, floors or any other surfaces within the sort of wavelengths involved in bass then they will emphasize or subtract from those frequencies. My practice room for example resonates right on bottom A. I use my tone controls essentially to get a flat response and then use the deep and bright settings on my Ashdown to vary the tone along with the tone control on the bass.

[quote name='Dubs' post='1003474' date='Oct 28 2010, 10:44 AM']What are the problems when pairing ported and sealed cabs? After reading this thread a few days ago I was half considering to make a sealed 2x8 vertical array cab with the Fane speakers to make a matching pair with my 1x10 ported cab that I made a few months ago.[/quote] It is the problem you always get with multiple drivers. If you accidentally connect up two speakers with the connections reversed on one then as one goes forwards the other is going back and the air doesn't move the result is you get no bass. You can usually try this with your hi-fi if you want. In this case the speakers are 180 degrees out of phase. If two speakers are different distances away from your ears then the sound from one arrives a little later than the other and are out of phase by differing amounts. You also get phase delays at a reflex port. All this causes frequency irregularities and lobing of the radiation pattern of the speaker system. I hope Alex doesn't mind me answering in what is his forum but I'm going to stick my neck out. His designs aim at a clean and predictable bass response and mainly try to get the most out of a single driver. By investing in modern, long throw and well damped, high power drivers you get rid of the problems of multiple drive units and one good driver costs no more than a bunch of cheap ones. Because you have a well engineered speaker you can then use EQ to get the tone you want. There are loads of design considerations when you mix drivers, which are genuinely too complex for a forum like this. There are solutions, the easiest being to stop the bass going to one driver with a crossover. Some designs for an instrument speaker are messy and ill thought out but work despite this, in the sense that some people love a highly coloured sound. It is going to cost you £100 and a couple of days fiddling to find out if your plans will give you the sound you want. What you are suggesting isn't wrong it is just that there is no way of knowing what it will sound like.

[quote name='pandathe3' post='1003203' date='Oct 27 2010, 11:49 PM']Hey guys, thanks for all the input. Just so you guys get the idea: i chose the 2x8 build for several reasons. Most i mentioned before (weight, portability ect ect) increased midrange is another factor but maybe the biggest reason is having all the headroom in such a compact (and splittable) rig. As it is my first build, and is being built for use with the 4ohm 112 i will be taking what seems the easiest route. Sealed 2x8 enclosure (lined horizontally, so its as small as possible). The box design can be easily done. Just abit stumped on the wiring. If someone could present a rough wiring diagram of the speakers wired to 4ohms, then to speakon thatd be great. The idea of a single 8 sounds good but i need the 2 x 8 to handel the 500watts of power. Im quite like the idea of the 12 and 2 8s. You all must understand that this project is specifically being built to be coupled with my schroeder. I have been thinking about designing a 12 + 2x8 for the floor up. If done properly i think it could sound great! The plan would basically take the crossover and tweeter and place it in the 2x8 cab, leaving the 12 by itself! Porting for both cabinets, id then use fanes, and keep them tuned to get as flat as possible frequency response. SORTED! Ofcourse that will come after this and this first build is to give me an idea of what im working with and howthe config will sound.[/quote] One of us is confused, it may be me. A sealed cab is an alternative to a ported cab, are you proposing to build two cabs? Don't get me wrong I'm all in favour of self building and trying new ideas out and I think the idea of bassists adding smaller speakers to a rig is excellent. I've also sketched out a design for a 4x8 using the Fane Sovereigns and am working on designs to add upper mid to my own rigs. I think it is possible that your lack of theoretical knowledge may let you down in achieving what you want in terms of sound. You could use the 8's in two ways; you could build a full range speaker which would work as a stand alone/practice speaker which would have a different and more extended response to your 12 (kind of like a smaller version of a 15+4x10) or you could use it as a specific midrange speaker to take over and extend the higher frequencies, a tweeter for bass guitar. Both might work but they are alternatives and I'm not sure which you are trying to achieve. If you are after augmenting your Schroeder with a standalone speaker then you don't need a crossover and you might consider a sealed cab or a ported cab for this purpose. Both have advantages and disadvantages. You would need a stereo amp if you use a 2x8 or an amp capable of driving into 2 ohms. You might even want to consider a 4x8. If you are going to use the 8 as a midrange speaker taking over from the 12 at higher frequencies then you only need one speaker. Because even a simple capacitor crossover will filter out the bass (where all the watts are) your 8" speaker will handle its share of 500W with no problems. There is no point at all in using a ported cab for this purpose. It would be worse than a small sealed cab. You need to make a choice, are you building a mid/high cab to augment your 12 or a multiple 8 to share equal duties? If it helps you could have a look at this [url="http://www.ultimate-guitar.com/columns/gear_maintenance/cabinets_for_guitars.html"]http://www.ultimate-guitar.com/columns/gea...or_guitars.html[/url] and then start googling.

[quote name='alexclaber' post='1000943' date='Oct 26 2010, 11:21 AM']I agree with what Phil's saying! I'd put the 8"s in a small sealed cab, vertically aligned. If the dimensions of that bother you then lowpass one of the 8"s at about 1500Hz. Actually, re-reading I see that you're referring to a 1x12" cab, in which case you only need one 8" to keep up. Small sealed cab, highpass with a capacitor. Done. LH1000 is overkill to power them - they'll both reach their limits way before it does. If your current cab is a 4 ohm cab then by placing the highpass on the 8" high enough you can still present a suitable load to the amp (as the Schroeder's impedance will increase steadily though the mids and highs).[/quote] This is great advice. Using a single unit would be perfect, you should also consider using a 6" unit like the Fane sovereign. You'll need a 13.25 microfarad capacitor for a 1500Hz crossover using an 8ohm speaker, though they don't make them in this value, 12 or 15uF would be close enough. Reversible or non-polarised electrolytics are a cheap option costing a few pence. I would try lower crossover frequencies though. I'd get a bunch of 10uF capacitors and try adding 1,2,3,4 etc. in parallel and seeing what sounded best before making a final decision about the crossover frequency. doubling the capacitance will halve the frequency. [quote name='alexclaber' post='1001057' date='Oct 26 2010, 01:00 PM']Well I guess a diagonal array could be a good idea if you always play on hillsides facing in the same direction.[/quote]

[quote name='thinman' post='1000350' date='Oct 25 2010, 07:23 PM']There's no certainty that what you're doing will be wothwhile. It may sound great or it may sound rubbish - it's an unknown. A "proper" design would probably include a crossover and be on the basis that the 1 x 12 cab was tuned to do the very bottom and the 2 x 8 cab tuned for mids only - what you'll have is two differing designs trying to do the same job. As Mr Foxen stated, mixing of driver sizes to do the same job (rather than being part of a multiway design) is hit and miss. There are lots of people out there mixing 15s and 10s and if they're happy that way then fine, but in terms of "correct" design it's a no-no. Wiring these may also be interesting if they're 8 ohm drivers. If all three are in parallel you'll have a 2.6 ohm load - quite low for a lot of amps. If the 2 x 8s are in series and in parallel with the 12" then they may well get drowned out.[/quote] It's true that any DIY speaker design is hit and miss but the idea that mixing speaker sizes is 'incorrect' in any way is nonsense. You are going to get cancellation/phasing problems with any two speakers spaced apart in a single speaker but that will happen equally if the speakers are the same size. If you mix two different speakers then they will have all sorts of differnt peaks and troughs in their frequency responses and mixing these will be just about impossible to predict although in my experience it does tend to subjectively smooth the sound as the peaks rarely coincide. This in the end is going to be an instrument speaker so the aim is not to have a flat response but a musical one. You could add a crossover but it isn't necessary. It would change the sound and you might prefer it or not. I did think of adding a capacitor in series with the 8's which would roll off the bass at 6dB/octave and increase their power handling (and be cheap) He doesn't need to worry about 2.6 ohms. It's a stereo amp. [quote name='Mr. Foxen' post='1000505' date='Oct 25 2010, 09:16 PM']Also important to note is that WinISD isn't very good at midrange, it is ok for tuning boxes for bass, but the line it gives might not very well reflect what you'll get higher that 500hz or something, there are loads of other variable, like reflections from inside the cab and suchlike that affect midrange frequencies.[/quote] No computer Thiele/Small modelling tells you anything about midrange it just tells you about the interaction of the box and speaker at frequencies around the resonant frequency of the speaker in question. I still think that there is little point in you designing a ported cab however. It will increase the bass your 8's give but not by much and you aren't using them to add bass but to pep up the mids if I understand you. If this is right there are no advantages in a ported cab and several disadvantages, so why bother?

Thought I'd do an update on my latest experiments with Piezo's. I've built a couple of 12+horns for PA and monitor use and my wife is away so I've been fiddling with them. The speakers have Beyma SM212 12" drivers in a 45l box with cheapo piezo compression drivers with a simple attenuator so the piezo's won't conk out when I put 300W through them. I've A/B blind tested them (well I didn't tell my daughter/test subject which speaker was which) with the Yamaha S112V's that I usually use as PA. Young people and women have better hearing and I didn't want wishful thinking to colour my judgement so thanks Naomi for being my guinea pig. I was expecting the bass to be better as the Beyma's far outspec the Eminence Deltas the Yamahas use but didn't think the piezo's would be anywhere near the 2" compression drivers and proper crossover in the S112's, especially since when I tried them when I first built them there was a real hole in the midrange. Wrong! Piano, female vocals (Grace Slick, Joan Armatrading, I'm a bit old fashioned) male vocals all jumped out of the mix with much better detail and the midrange suckout had all but disappeared The bass tone was fantastic, but I knew that anyway since I often use them as part of my bass stack. I think what has happened is that using the Beymas has broken them in allowing the cones to flex more and increasing the midrange so there is no longer a gap. I wish I'd measured them when they weren't sounding so good so I could have a before and after plot. So, my conclusions are: piezo's can sound OK even in midpriced/mid-performance speakers and speakers really do 'break in' over time. If anyone is interested I'll start a new thread and put up a few details

Too good for me but when they performed this on 'Later' the bass player switched to keys halfway through. This is a very heavily mixed recording and I suspect a lot of overdubbing and some of the bass is definitely keys. Have a look at this and you'll get the hand positions. [url="http://www.youtube.com/watch?v=vMyc148Do_Q"]http://www.youtube.com/watch?v=vMyc148Do_Q[/url]

If your existing cab gives you enough bass then you have enough bass. Adding these speakers will give you more midrange although as I think you've already spotted the beta has a midrange peak and the Fane is relatively flat. The simplest way of building this cab is to make a sealed cab. This will reduce the bass from the 8's slightly but will leave the mids unaffected and make the build a lot easier. It will also improve the transient response and so long as it is sealed will guarantee a successful build. You will also end up with a smaller cab. If you do go for a reflex cab then tune it with tube ports as it is relatively simple to re tune if you get your calculations wrong, or more likely that the speakers don't exactly match their spec. You need to get to grips with one of the free design programs winisd or AJDesigner [url="http://www.ajdesigner.com/speaker/index.php"]http://www.ajdesigner.com/speaker/index.php[/url] are both useful, Win is more flexible and AJ is easier to use. If you get really stuck I'm sure someone here will calculate a volume for you. When you enter Vas into the programs you need to double it because you have two speakers.

[quote name='umph' post='993473' date='Oct 19 2010, 01:25 PM']The transformers are heavily overrated they are partridge afterall! You'll get 50w from a PAIR of el34's not each one unless your running them with 800v on the plate and 300 on the screens which the soundcity isn't.[/quote] 100W at that voltage according to the mullard data I have here, though I bow to your knowledge of how they are set up in the Sound City. I just remember what I measured into a dummy load because it surprised me so much at the time. This was in 1973 so they may have made changes since then. The transformers will give less current when they are warm. What is more important is whether you can get replacements. I have had to replace the output transformer on one of these long ago and no amp is completely bomb proof. I don't repair valve stuff any more so I've no idea about current availability but if parts are a problem then it is worth knowing before you part with any cash. I'm hoping someone can say it's no problem (unless it is) so this guy can make a good choice. Still it is nice to look at an old friend. All those lovely valves...

[quote name='Mr. Foxen' post='993335' date='Oct 19 2010, 11:38 AM']The Sound City will sort you, if you get an appropriate cab. When people say 'distortion', they don't mean pedal type distortion, compression is probably a better word. Valve amp power compression/distortion sounds good, not in a good distortion pedal kind f way, but in a big fat awesome valve amp tone kind of way that is pretty much not comparable in any way to pedals labeled 'distortion'.[/quote] Yep, that's absolutely fair [quote name='Crazykiwi' post='993348' date='Oct 19 2010, 11:45 AM']I think it would be better to talk about perceptions of loudness rather than watts, just to avoid confusion.[/quote] It is always difficult to know how techie to be. Using decibels rather than watts is better because it allows for the efficiency of the speaker but this still doesn't allow for the difference in sensitivity to different frequencies. I've tried to deal with these issues in my article a bit. Each EL34 will dissipate 50W and depending on the exact circuit details and bias settings you will get more than 120W. The limit is the transformers which will warm up and limit the power if you crank up for long periods. Hence the 120W rating, I guess. It is 40 years nearly since I took one of these babies apart however so take everything I say in that light. I think it will be loud enough and if it isn't you need to look at your speakers. My worry would be about reliability and the availability of spares. How old is this amp and how much will it cost?

In amongst all these posts you have most of the facts. A watt is a watt but valve amps behave differently when they are overloaded and so you can push the average levels closer to the maximum output. Watts don't measure loudness which is about sound pressure levels and the different perception of different frequencies. Sound pressure depends as much on the speakers as the amp. Doubling the amp power only gives a 3dB increase in power. If you want a summary of how this all works red this [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] I don't know which Sound City you are looking at but the ones I used to use had 6x EL34 output valves and I measured the output at 300W RMS over a 30sec test period (I kept blowing speakers) so the short term output might be better than the continuous rating. If your amp isn't loud enough for the audience then go through the PA. If a 120W valve amp isn't loud enough for you to hear then stand nearer your speakers and away from the guitarists/drummer. You are already causing permanent damage to your hearing by the way.

I've used an antex 25W iron for years and it does most things well though Stevie is right it will struggle to solder the earths onto the back of the pots. I get round this by warming them with a hair dryer if I need to do that job. A 40W iron can be too clumsy at times for working on small components. I'm using Adepto solder from maplins and like Stevie it's an old lead based roll, they last forever. Make sure it's rosin cored

The simple way to do this is to use your ears. If you have two amps and they are out of phase by 180 degrees you will lose some bass and if not you won't so just do two at a time and reverse the polarity of the input lead. Make sure you keep everything earthed though. The battery trick will give you a momentary movement of the speaker but obviously you won't want to put 9V into an input jack. Use 1.5V and a line level input if you want to try this way. I don't think you need to worry too much. You are going to get cancellation and reinforcement due to the different path lengths from spaced cabs anyway as well as those due to reflections off the floor and walls. Any phase lag of a few degrees will change the sound a little but whether this will be audible will depend upon the exact position of the listener and the room acoustics. Hope this helps

[quote name='XPAULUSX' post='981350' date='Oct 8 2010, 10:44 AM']But theres four speakers right? Two satellite and two bins, how does the impedance work out for the whole system? Sorry i'm just new at this :0)[/quote] Don't worry about it. The bass bins have a crossover in them so the sound is divided between the two speakers and the Impedance the amp sees is that of the bass bins, 4 ohms in the case of the Peaveys, 8 ohms if you use the tops on their own. The crossover splits the power at a particular frequency, above this everything goes to the tops below everything to the subs and at the crossover frequency half goes to each. The power handling is the sum of both (more or less)

The Wharfedales are fantastic value, not their best but at that price they will get you through. If I could get to W.Yorks they would be sold. The peavey's are OK too. they don't give the best vocal sound with their cheap horns but you'll need to spend more on something like the Mackies or Yamaha's etc to get better. Impedance works the same way for PA as it does for any other speakers and amps. It is fairly normal to use a slightly overpowered amp however as you never should run a PA amp into distortion, so a 500W/channel amp into 350W speakers wouldn't be considered unreasonable as long as you don't crank everything up to flat out.

Just thought I'd try to clear up the high Q issue. Q is all about the control of the speaker at resonance. A big magnet will control the speakers oscillations more than a small magnet. Of course it will also control the cone better at other frequencies and transients will be better. A high Q speaker will need a bigger cab and will tend to have a bass hump and any note near that hump will excite the oscillation in that area and sound bassy and wooly or warm and rich depending upon your prejudice. Cheap hi-fi exploits this phenomenon to make them sound bassy but it makes all bass notes sound alike cos your hearing the speaker not the music, hence the one note bass tag. A really low Q speaker gives you extended control of the bass and much better behaviour in a reflex cab but can squash the bass a little and it can roll off at 6dB/octave from quite high up. Because it is controlled a little eq sorts this out. For most purposes Qts above 0.4 is high and below is low. I wouldn't normally put a speaker with a Q above 0.4 in a reflex cab by choice and I don't think the beta is suitable for a reflex cab. If you go for this solution block the ports, it'll save worrying about tuning. The advantage of the bass hump in an instrument speaker is obvious; it will make the cab sound bassier and if you combine this with the midrange hump of the beta it will sound quite lively. A bit like switching the loudness control on a cheap hifi and I guess this is why BFM suggested it. The Fane which I've used in a design will be much better behaved and will sound quite 'polite'. With no real midrange hump it probably needs something else with it to help it cut through the mix. Coincidentally I'm currently messsing around with some 10" Fanes. I built a 4x10 for the 10-275's (big magnets, lowQ) and then because I had them to hand put the 10-125 (small magnet, highQ) in half the cab, which is partitioned so now I can compare the two speakers and see for myself the effect of the 'one note bass'. It is surprisingly subtle, very distinct on recorded music but certainly none of the rest of the band have noticed me swapping over at gigs where so many other factors affect your sound. Yeah, you probably can get something better for £100 if you look long enough but the beta is only £50 from Blue Aran and you could also look at the Fane 15-400 with a slightly bigger magnet at £56 or the Eminence Delta at £61

As a temporary and cost free solution you could try blocking the port. It seems possible that the cab was not re-tuned properly when the Celestion was fitted and there is no real loading on the speaker at low frequencies. It is equally likely that a 1970's speaker has a fairly short voice coil and it is simply exceeding it's excursion limits. Either way making a sealed cab might help clean up the bass a bit and it will cost you nothing to try. Putting 100W through a speaker like this is likely to blow it fairly quickly though and you need a new speaker. The beta looks good.

I've tried a Peavey. I like the Black Widows sound. good for everything but going up stairs!

It is not a sensible thing to do. The cab starts to cut out at any frequency below the point where the shortest distance around from the back of the speakers is haslf a wavelength of that frequency. in practice two octaves above low E. The speakers are designed with stiffer suspensions lighter cones and shorter travel etc. etc. for this application. Any deep bass will push the short voice coils right out of the magnet gap so you'll run out of output at probably less than 50W. Depending upon the detailed design of the drive units you may well blow them at a relatively low power and they won't sound good anyway. If you want the punchy sound of a guitar cab there are better ways of doing it.

[quote name='Bill Fitzmaurice' post='968428' date='Sep 26 2010, 03:03 PM']The adhesive used by Eminence is superglue (cyanoacrylic). Run a bead of it around the joint, spray it with superglue accelerator for an instant cure.[/quote] I'd back Bill on this one. I use copydex because I've always used it but the dust cap is a rigid fix and if cyanoacrylate is good enough for Eminence...