Phil Starr

Hi again You've kind of asked several questions here, I don't have a lot of time so I'll just answer the one in this bit of your post. So first of all you are spot on, basically you get twice the power through 4ohms and half the power moving back up to eight ohms . But that's theoretical, the theory works when the amp is running with the volume down but when you turn up full practical limits come in and it's almost always slightly less than double. 125W is as good a guesstimate as any. The second bit is about how much power the speaker is safe with. Matching the amp to the cab (there is a third question about matching two speakers but I'll ignore that for now) It's slightly complex because the power rating of a speaker is measured very differently to the way an amps power is measured. For the amp you are just measuring it's electrical output. If you know the Volts and Ohms you know the theoretical power and you just need to check that the amp can provide the current. Speakers are more complex, you can destroy them in two ways, pass too much power and the coil gets hotter and hotter and eventually blows. (heat causes other problems too but let's keep it simple). The second thing that can destroy a speaker is uncontrolled movement beyond the design limits of the speaker. The more power you apply from the amp the further the speaker cone and couil move, but this is also affected by frequency. The lower the note the more the speaker moves and a combination of excessive bass and power is what is more likely to cause failure by over-excursion than heat alone. It's that frequency element that makes it complex because: a.) nobody knows how you are going to eq or play your bass and b.) The cab plays a big part in controlling excursion so the same speaker may handle 300W in one cab and only 150W in a different cab. So, at the factory where they design and build drive units they test speakers by putting them in a standard box and by passing a standard signal through the amp for several hours until eventually they know how much power they can apply before the speaker fails. The standard AES test is for two hours and the standard signal is white noise (all the frequencies) but filtered to mimic the mix of frequencies in 'typical' music. The AES test says the speaker should be able to handle the power for two hours without failing. It's a good fair test and easy to do so you can compare speakers. Engineers and speaker designers can be pretty confident with this information but they knows that this is only half the story. Once the drive units leave the factory they cannot know what cabinet they are going into and what instrument they will be used for or how the musician will play, there are so many unknowns that no attempt is made to rate the speakers for use. So when you buy a 2x10 fitted with two Celestion speakers rated at 200W ea you will be told its a 400W cab. and samples of the speakers have been through the severest test possible of running for two hours at full power without harm. The reality though is that your 500W amp isn't going to overheat them. Music isn't continuous noise it has loud bits, quiet bits and times when you stop playing. Have a look on the back of any modern amp and it will give a figure for power consumption which is way below the maximum power of the amp. I've got the 200W Gnome in front of me and it says 60W power consumption. That breaks down to 10W of energy wasted heating the amp and 25% of the 200W going to the speakers on average when the amp is running flat out. If you keep the bass eq down and play 'normally' you can safely use a 1000W amp without your 400W speaker over-heating and some people actually do that. The problem is that you might like a bit of bass boost or you may add in all sorts of pedals and you still have the excursion limits of the speaker to worry about. There might be a frequency where each of those Celestions can only handle 25W each and your 400w cab is only a 50W cab at that point. So going back to your question, you could almost certainly use your 100W speaker with your 125W amp. 99% of the time if you use a 300W amp with a 300W speaker you'll never have a failure, you can probably risk going a lot further and use an amp that is double the power. People rarely turn their amps up full anyway and in reality your average power use will never reach 25% of full power. You don't need to be over protective but you do need to be aware of the over-excursion issue. If you are using a of of bass boost, slapping your bass without compression or increasing the frequencies below 100Hz in an unusual way and you hear unusual noises from your speakers at high volumes then you just might have a problem. I suppose I'm saying just be aware you are comparing apples with pears when looking at amp watts and speaker watts, six apples don't necessarily weigh the same as six pears

Hi Smanth Power is all about the transfer of energy the watt is a transfer at a rate of one joule per second. In electrical terms it's calculated by multiplying the voltage by the current. So for 100W you could have a power supply of 100V at 1A. For a 10v supply you'd need to drive 10A and for 1V supply you would need 100A. Your amplifier will be built with a power supply which has a fixed voltage which it simply can't go above and it will also have a current limit where it starts to overheat, the voltage will drop and eventually it will burn out (OK it won't as it will probably blow a fuse or trip something, but lets keep it simple) So the current is reduced as the resistance increases. If your amp is a 50V amp and your speaker is 8ohms you'll get 50/8=6.25 amps. 50Vx6.25A=312W If you use a 4ohm speaker you'll get 12.5A which would give you 624W and a 2ohm speaker 1248W and so on, but of course you won't get unlimited current so in the end the amps power supply will overheat and break down in some way (usually controlled ) This is why you see so many 300W into 8ohms and 500 into 4ohm put a amplifiers. It makes no economic sense to put a bigger power supply into a medium power amp when you could up the voltage a little and deliver that power to an eight or four ohm speaker. So the instantaneous peak is just advertising nonsense. You can measure the power supply voltage and you can measure the maximum current and that gives the power. The instantaneous power is just the real power multiplied by 2. Sometimes they give it away with an asterisk* sometimes they don't and even don't tell you they haven't ever measured it, because you can't measure a ghost! *calculated (as if multiplying a number by two is much of a calculation) There is a fiddle here which lets the advertisers get away with it which I'm happy to explain but it's to do with RMS voltages and I'll only answer if you ask So minimum load is 4ohms because any lower would draw too much current and overheat everything if you turn the volume up too high and the Speakon is only marked as an extra warning, it's written on the amp and in the manual too so you can't say you weren't warned.

That's almost a thread de-rail One of my pet hates. They are always the ones that suggest the songs with all the clever arrangements, never get on top of the tricky bits and then tell us it is more 'creative' to do our own version with just verse/chorus and an extended guitar solo over 32 bars of E7.

Genre often makes things more difficult too, I briefly played in a country band and thought foolishly 'all root-fifth and on the beat' Completely missed that this leaves nowhere to hide and the bass is prominent so you can't afford to be sloppy. Every genre has it's meme's and looks easy when someone else is playing.

I feel the pain, though as you both say it makes for a more interesting song but I curse when someone wants you to play one of these with a couple of days notice. One thing that always trips me is where there are maybe only two or three chords and in just one or two parts of the song where the chord sequence changes but the rhythm doesn't.

I guess it's personal to an extent but playing with three covers bands I learn a lot of songs, mostly at fairly short notice. With Christmas coming up I'm getting suggestions for songs we'll only play a couple of times a year and a lot of them are written by 'proper' musicians and have a lot of arrangement going on where they look superficially simple but have a lot going on musically. We've also had a run of illness and had to use a lot of deps so they prefer to do simpler songs for what are one off gigs for them. It's a given for me that I don't have notes in front of me when I play. More or less in order I find these make things more difficult Songs I've never heard, it's so much easier if it's a song you can hum along to. Complex arrangements. Rhythmic complexity (took ages to get the Steve Harris thing) Chord changes part way through a bar. Every verse is different Stops So what makes your heart sink when the singer says 'Let's learn three new songs for a one off gig'

It all sounds promising. Our '30l' cab is actually around that size, I prefer to be slightly over than under and I found with your speaker that going down to 30l and below was where the performance fell off sharply so 34l looks good. I did try 55hz tuning and thought it looked a little better but that to an extent is about taste. It's worth remembering that winISD is only as good as the data you enter and that the manufacturers specs are sometimes not entirely accurate. The program also makes some assumptions about things like leakage from the cab assuming Ql is around 7 for example. so calculated tuning is not always the same as the actual tuning. With drainpipe being so cheap I've often made up a number of ports so I can swap them around quickly and try different tunings. It's all about what sounds good as well and ideally you want an iterative process of designing and testing. Have a look at excursion and maximum power handling too once you have programmed in the tuning as this will change at 55Hz too. This is the point where it gets exciting

I've had a quick look and Bill is spot on 40l is about right for your speaker. Any smaller and you lose a lot of bass response which you will definitely hear in the result. This is the bass response of your Deltalite in a 25l cab in red. The green line is the Celestion Pulse in our 30l cab which has a fairly light neutral sounding bass. You can get that sort of response if you go to 35 litres with your driver and I think you'll prefer the extra bass. You'll get even more of you go up to 42l but i personally wouldn't go down to 25l with that driver, for me you'd be squeezing the life out of it

When I designed the first easy build cab I wanted it to be something that someone with minimal tools and experience could build on the kitchen table with the minimum frustration and the maximum chance of success. I wanted to use materials that are available not just in the UK but around the world and not likely to disappear. I've 50+ years of experience building cabs and access to my own well equipped workshop but I wanted something somebody could build with the tools I started out with: screwdriver, drill, and a couple of saws. Using screwed and glued battens makes it all a lot easier with no need to wait around for glue to dry, no fiddly clamping and very little chance of failure. Happily lot's of people have been encouraged to build their first cabs and are happy with the results

But if you have found the amp that get's the best out of your speakers you have to buy one for demonstrations, that makes it a business expense The colours match too!

TBH if you have PA support then you don’t need 1000W or a 4ohm speaker. Indeed it is a positively bad idea. If the PA is what the audience are hearing then you need them not to hear the bass amp and even more importantly you need to turn down as much stage sound as possible to keep it out of the vocal mics. You’ll never get a clean sound if you and the other instruments are drowning the vocals and distorting the feed to the PA. Go for a really good 112, it will serve you better than a cheaper 212 and if you absolutely need volume when you don’t have PA support you can add a second. A decent 112 with 500W through 8ohms is already way more than you need for stage monitoring.

My computer is down at the moment, fixed now but I won’t have it back today. I’ll have a look at the delta lite for you some time. You can use two 68mm ports. There is a marginal gain to bo had from a single port of the same area in reducing turbulence in the port but in practice I’m not sure if it is significant. Using what you have makes sense and if you have a holesaw that size it’s a no brainer in keeping construction simpler. If you want a ready made design then the 30l easy build cab we used in the BC 110T and the Easybuild 12 would work well with maybe a slight change in tuning needed.

Good questions. Properly specified cabs are given a cut off frequency, but that is the point at which the response starts to roll off, anyone designing a cab will use the point where the response is 3db down but it doesn’t stop producing bass there bur rolls off the bass at 12-24db per octave. As Bill has said that -3db point is often around 60 Hz, you can still hear it a bit but it won’t be very loud and isn’t important for a band. Speaker diameter isn’t important in determining f3 (the roll off point). There are lots of 10’s That go lower than 15’s and I’m looking at my 5” monitors that go lower than any bass speaker. The cone mass and stiffness of the suspension determines f3. There is no magic. God does not play dice 😀😀 Most cabs are ported or bass reflex cabs. In a plain sealed box a speaker may go down to 60 Hz but in a ported cab the port output take’s the response down lower and gives you an extra 3 db of bass. It is really hard not to want that extra free bass. The port and cab work like a bottle when you blow across it and resonates at a particular frequency which is tuned to come in just where the speaker starts to struggle. So the tuning frequency is the resonant frequency of the cab. In practice the speaker and cab interact which is where the real action is in cab design and there is the possibility of tweaking a design.

Yes you will need to subtract those volumes😀

I believe the Super Steel is epoxy based with a filler. As described I don’t think you’ll have too much of a problem. The teeth of the t nut are only there to stop the nut turning. They shouldn’t need to be very strong and the epoxy or filler should hold it. If you check the thread isn’t binding and make it finger tight before you use any pressure you should be able to tighten it enough and the strength should be unaffected

Work is the curse of the musically inclined.

Ha ha I read 8” too 😀 Crossover design done well is tricky so it depends on what you are trying to achieve. You can make a simple high pass filter to protect the tweeter which will add a bit of tizz at the top end. A simple capacitor will do that and that is all you sometimes get with commercial speakers at the cheaper end. At the other end you can carefully roll off the midrange of your woofer at a target rate and carefully bring in your tweeter to take over the upper mids, correct for phase irregularities and peaks in the response of both drivers. you’ll need to decide on the best crossover frequency, match the sensitivity of each driver and decide upon how steep a slope you want at the crossover. You can copy an existing simple filter as in th BassChat 110T or buy a commercial two way crossover and tweak it with listening tests which will work after a fashion and maybe give you a sound you like. Beyond that it’s a question as to how far you want to go.

I switched recently to the Lekato from a Line Six. Nothing wrong with the Line Six but I prefer the simpler form of the Lekato. Both sound better than a lead. I did have one gig where I was picking up some electrical noise. A private party where someone had set up some cheap led party lights next to the band. I switched to a wired connection but have had no problems using the Lekato since and can’t reproduce the fault. I could probably have switched channels if I’d had time.

Glad it is working, I’m still slightly surprised by mine when I crank it. Another outing for it tonight as it happens. I need to get on with the Eight and a finalised design.

Welcome to BassChat. Whereabouts in Devon are you.

Jefferson Archive are really very good

That’s a lovely offer John. They are fine drivers.

He's a lovely guy IME I'm really pleased he's stuck with it and he's great when you have a problem. Lemonrock is such a useful resource when it is strong in your area. I'd hate to see it go under. And yeah I'm sure you are right Sylvie. In the end the forum just got too time consuming and stressful.

That's the truth

It wasn't any worse than BassChat but there were a few heated posts when some of the venues cancelled gigs at the last minute or refused to pay bands. Mac was trying to get the venues to join at the time so he obviously wasn't comfortable with that. I offered to be a moderator and I may have 'volunteered' a couple of other people like @skidder652003 as others who might have helped. Coming from the not-for-profit sector I'm predisposed to think its a good way of organising a small venture like Lemonrock or BassChat. The people doing all the work can be paid the going rate for the job and volunteers can add value. The collective nature of the enterprise means that in difficult times people are more willing to donate to keep something they love alive and thriving. It also offers a way of the organisation surviving when the initiating group moves on.