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Phil Starr

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  1. this shows pretty much what Bill is talking about and i happened to have it on screen. I'm designing a speaker for a practice amp and this is a plot of the maximum power handling for a 6" speaker. The flat line at the top of the graph is where the power handling is limited by the heat in the voice coil (100W in this case) Between 100 and 250Hz the speaker has to move a long way to move the air so the speaker can only handle 20W without distorting. The flat bit at around 90Hz is where the port will be making the sound and the speaker stops moving. Below that the speaker is effectively in free air as the port stops being a barrier and the power handling drops to almost nothing. This is a tiny speaker I'm proposing to use with a battery powered amp so it's fine for this job but the general shape of this graph will be the same for most drivers. Speaker manufacturers quote the thermal limit because it's easily measured and checkable. The rest depends upon the cabinet and frequency so they can't really give a definite figure but the cab designer can work it out. You don't really need to know this to buy a cab except that it is useful to know that sounds below the port frequency can damage speakers if you drive them hard and that driving any speaker to it's thermal limit isn't great.
  2. Hi Jack, you have it right, more or less. the 6dB gain is made up of two parts, there's a 3dB gain due to the halving of the impedance and the amplifier providing double the power (if it can, more later) The other 3dB is due to the increase in efficiency of converting the cone movement into air movement by doubling the cone area. Which is available simply by adding the extra cab. The complexity is in the amp. The amp provides a voltage across the speakers which determines the maximum power but providing tht power continuously depends upon the power supply built into the amp. If you move from 16ohms to 8 then the power will almost always double. For most commercial bass amps if you then halve again to 4ohms then the power supply won't be able to provide enough current and the amp won't quite be able to double the power. Typically most current amps will do something like 300W into 8ohms and 500 into 4 so the increase in power by doubling will be more like 2dB than 3dB and the increase in sound nearer 5dB than the theoretical 6dB. A few designed for 2ohm operation will still double at this point but will then run out of the ability to double the current going from 4ohms to 2. Power is voltage x current and the power from an amp can be voltage or current limited. The Barefaced is interesting as it has a crossover inside so the switch from 4ohms to 12 is achieved by changing both the crossover and the wiring of the speakers. Quite slick really. Impedance in any case changes across the frequency spectrum and the ohms quoted are for any speaker are an average. So to answer @alexa3020 's question. doubling up the BF 210's will give you extra volume. How much will depend upon the exact design of the amp you are using. You'll gain 3db from the extra speakers but how much power you will lose depends upon whether the amp is current limited or voltage limited at 6ohms. My guess is that it will be voltage limited and will provide roughly the same power into 6ohms as it will into 4. Overall you'll be 2-3dB louder, but it isn't as simple as this. By adding the extra cab you are going to lift the top speaker to ear level and changing the radiation pattern for the audience. You are also reducing the current and power to each of the 10's and this reduces the amount they heat up and power compression at high levels as well as distortion. There will also be changes in the coupling of the speakers with the floor as this is dependent upon the distance of each driver from the floor. The important thing is how this sounds. Adding the 2-3dB isn't huge but will be noticeable but I think you will experience a cleaner sounding and more authoritative sound and you'll be able to hear yourself more clearly above the band. Two speakers stacked vertically is a lovely experience for a bassist and if you can afford it then it will probably become your go to setup even at smaller gigs.
  3. It's simple enough to wire up a special lead to combine your cabs the way you want and @Chienmortbb would do that for you. It doesn't make sense though. So much of the power will go through the 15 that it's sound will dominate and the 10's will be almost. Using a single 8 ohm 2x10 would match the 1x15 much better, and probably better than an 8ohm 4x10 depending upon what sort of a sound you want. another option might be to swap around the drivers from the 4x10 for the ones in the 2x10's but honestly I don't see the point unless there is a particular sound you are trying to achieve. If you are keeping all four cabs you already have loads of options. The mis matching 3 cab solution makes little sense
  4. This sort of noise might well be due to failure of the adhesives around the cone if this is an older cab. It may well be that the whizzer cone is coming away, also have a look at where the main cone is fixed to the frame and around the corrugated surround. Look at the dust cover, the dome in the middle. I've always used copydex adhesive to glue thins back together. It's latex based and stays flexible and is great with wood pulp things like speaker cones.
  5. Most of the weight comes from the power supply. You can have a class D amp with a conventional power supply (why would you ?) or an AB amp with a switchmode (lightweight) power supply. Having said that this looks too heavy to be anything but a conventional supply with a heavy mains transformer and is likely to be class AB. I'm a little confused by Harley Benton's positioning of amps and speakers at the moment. Price wise this amp is in competition with the Bugera which doesn't give 2000W but does give 7-800W and has a good reputation from acual users, the Peavey Minimax plus less powerful but capable offerings from TC, Trace Elliott, Mark Bass. If I wanted a backup amp I'd go for these smaller and lighter amps and save the body building for my main amp. In fact I bought the Peavey and it is so good I use it as my main amp. Unless these things sound amazing, and they might of course, I'd go for a more glamorous brand which would fetch a better used price if you want to move it on.
  6. Hope it works out well for you, let us know how you get on. Good luck.
  7. I'm not an expert on the maths around fluid dynamics. the only time I studied it was back in the 60's so this is really broad brush. The thing that causes compression and the wind noise is turbulence in the port at high velocities. Turbulence will add in an additional resistive element to the port reducing the radiation of the cab around the tuning frequency. The port only really radiates sound at the tuning frequency so isn't going to affect the frequency response apart from around the tuning range. I don't think anyone can reliably answer the question about 'allowing' for 100W. Without knowing exactly how you play and what eq you will use in the future it's almost impossible to say what level of discount you could reasonably apply and how frequently and by how much you'd exceed 15m/sec in the port. Remember too that these guideline port velocities are just that, guidelines. The people that developed the theories behind all this differ in what sort of port speed is acceptable and I've seen figures between 14 and 20 given as ideal. To give you a wattage figure we'd need some basis in theory to make a calculation and we don't have that. If you look at the port velocity at 50W you are looking at 3dB down, if it is 6dB down it is 25W. Port dimensions around the sizes you are thinking of seem fine to me and so does a 64 hz tuning.
  8. Not quite, the point is actually really simple physics. The fundamental is the note produced when the string is vibrating as a whole. It's fixed at the bridge and nut (nodes) and the middle of the string is the bit that is moving furthest (antinode). The antinode for the fundamental on an open string is at the 12th fret and that is the only spot where you'll get full output of fundamental. The closer to the bridge you place the pickups the less fundamental you'll get. The note is irrelevant if your bass is 34" scale the fundamental dominates only 17" into the string at fret 12. if your PUP is at 4" from the bridge it isn't going to get much fundamental. https://www.physicsclassroom.com/class/waves/Lesson-4/Nodes-and-Anti-nodes You've found that on your bass it is 12dB down and this is typical, in fact what I predicted. That means at the point where your amp is turned up loud not much of the power is going to be in the lowest frequencies which will cause over excursion. If you are running at 100W into the speakers it's unlikely that 10 of those watts are going to be fundamental unless you are using a lot of bass boost. If you are my feeling is that the speakers are going to be overwhelmed before you get a noticeable level of chuffing from the ports. You've run WinISD, the plots you need to consider are the excursion plots and the maximum power plots which tell you whether the speakers are coping or not. That is a concern, but with little drivers like yours I wouldn't worry about chuffing. Experienced builders are telling you a single 68mm bit of pipe (outside diameter of course) is going to be enough and that is good advice IMO. I've got 12" drivers here with a pair of ports this size running at 300W at gigs and I've never noticed problems with port noises at gigs. i'm probably getting some problems with compression due to port resistance but again in practice I haven't noticed. Speaker design is like squeezing a balloon, you squeeze one problem and another pops up. You can't really achieve perfection don't let that be the enemy of building something good.
  9. You are probably over-thinking this. What your amp will do is actually trace a complex waveform which tracks all the different harmonics added together. It will do this until it runs out of volts or sometimes the power supply in the amp will run out of current. If you are putting music in rather than a test signal then the notes decay over time and there will be gaps between the notes. Your amp will pump out its full power at all frequencies over its pass band if you put the right signal in. You are back to where you were in the other thread. Your bass pickups aren't in the middle of the strings so won't give you as much fundamental as harmonics, you'll find all your fundamentals are down about 12dB or 1/16th of the power compared to the 2nd harmonic unless you are fretting higher up the neck just as I said last time, your own measurements confirm this. The advice to keep wind speeds below 18m/s are from people designing for hi-fi use It's nice if you can achieve that but sometimes you can't in a practical cab especially if you are trying to build something really compact. In practice this is not going to be a problem.
  10. If you are going to use a crossover at 180Hz then you won't be running into 4ohms. Below 180 you'll be running into the sub and above that into the One 10, both at 8 ohms. At the crossover point the impedance of the crossover in series with each speaker effectively makes them both 16ohms (sort of) and so the overall 8ohms is maintained all the way. No free watts I'm afraid What you will do is change the sound, hence Bill's suggestion you go for a second One 10. The One10 is designed to be 'old school' compensating for the lack of deep bass with a bit of bass boost baked in at around 100Hz, which i for one really like. If you colour in the missing frequencies it will change the balance of the speaker. You'll get more deep bass probably as you'd expect, you might find one of the speakers is more efficient than the other and will dominate. What you will get is the possibility of better power handling as the power is split between the speakers. with everything below 180Hz diverted away from the One 10's you could possibly double the amp power, or just trde that for the same amp with less distortion. If you have the woofer then the proof of the pudding is in the listening in this case, give it a try and if you like it try it more If you don't then save up for a second One 10
  11. from the looks of this you don't have a balanced line mic. You would need three wires; two out of phase and ground. You can do this with the right transformer and it would do some impedance matching for you too but to me it looks like the original guy has a simple isolating transformer and his isn't balanced either. It's hard to tell from the link exactly what he has done. It doesn't really matter though, you've made a mic from a speaker and it works. You don't have a balanced line to run 25m cables back to a mixer but does that matter? It's fun doing this, I days gone by I've used a headphone as a mic, you just plug the jack into the mixer and speak into the cup. It sounds remarkably good and makes an OK drum mic if you aren't too fussy.
  12. Out of curiosity I checked, the cab is made out of poplar ply which is probably the lightest practical material to build a cab with. It's actually quite expensive compared to generic hardwood ply. 15mm thickness is quite acceptable for a cab this size but 18 is normal. The reviews mention some stiffening inside but this may be a single batten across the back which is common in 4x10's. Even so this is remarkable and if you were home building buying this cab and replacing the drivers might be almost as cheap as building your own once the cost of covering and hardware are included. Here's the link https://www.thomann.de/gb/harley_benton_solidbass_410t.htm A cab like this is going to be filled with drivers with very modest magnets to save money. Retail it's hard to buy any 10 for under £30 but that's OK the original idea of an 8x10 was to get high volume and plenty of bass warmth by packing lots of cheap speakers into a cab. These speakers will only weigh 2-2.5kg with 1.5" voice coils and magnets that weigh around a kg. http://www.bluearan.co.uk/index.php?category=Speaker_Components&startprod=0&instockonly=&man_old=all&masthead=Loudspeaker_Drivers&subheadnew=10_Inch_Drivers&sort=pr&manufacturer=all&stock_option=All+Availability&submit=Go This cab really is serious value for money. I think Harley Benton is just a label and they can be made for Thomann by anyone. If it was Bugera then that is the same group (Music Group) as Behringer and many others and whatever way you cut it this is probably just a generic 'made in China' cab. Final observation, it might be around the weight of the BF but the BF cabinet is going to be a lot stiffer and have complex cabinetry as well as more powerful neo speakers inside.
  13. That's interesting, I've found I'm leaving my J behind most of the time as I'm getting frustrated getting a good live sound with the J-Retro, which sounds great at home. Any thoughts as to why?
  14. I was interested enough to read this thread and It's an interesting question. I've been thinking about it for a while. My go-to practice bass is my Cort action bass, I love the neck and it's my starter bass and owes me nothing so it's left lying around completely carelessly and nothing to worry about. The down side is that it has no real sustain and sounds completely dead. Over the years I've tried all sorts of strings and changed the PUP's (currently Kent Armstrongs) but it's just lifeless. I've two Fenders and a Japanese Thunderbird and they all sound so much better and they all have a lot of sustain as well as sounding so full of life but they stay in the rack until gig days arrive. Sustain is really demanding, you really have to worry about string damping and dynamics. Playing live in really loud environments makes it really lively as feedback creeps in and the strings start to run away from you but it also increases the fun factor. There's nothing like it when the bass comes alive in your hands and every fret touch becomes a hammer-on. So sustain is a really double edged sword. Hence the foam damping I guess. I've always assumed sustain is at least partly about resonance, the body of the bass vibrating in tune with some of the string movement. For me the sustain of the fundamental always seems there but the higher frequencies within the note seem to fade away quickly if the bass doesn't have sustain, so it's not just the volume but the timbre that changes over time. So I'd love to hear some opinions and maybe someone with a bit of knowledge to come along and maybe i can mod my old Cort and make it come alive.
  15. bass cabs aren't really designed to do what PA subs do. You don't really need a lot of subsonic bass out of a bass cab, there's a limit to how mush bass a bass pickup puts out so the actual amount of deep bass is fairly low often they don't go much below 50Hz and frequently they can't handle full power over the next octave. They also have to cover the full range of a bass and this means a compromise in the lower frequencies. The speakers in a sub only have to cover a couple of octaves and nothing over 150Hz so they are specialist one trick ponies and they can do that well as a result. However if you have them and you lack bass from your PA you have nothing to lose by trying them, you'll need a crossover to limit the frequencies you send to them and probably to limit what goes to the tops. If you can borrow a crossover it will let you experiment and you can see if it works for you. It won't be perfect but if it is an improvement then why not? However there is another possible route. If you can send the kick and bass feed out through an aux channel on the mixer you could send them through your Schroeders freeing up the tops from having to deal with any deep bass. Aux fed subs are an accepted technique which might be worth a try. You can then filter everything else through the mixer at 80Hz, which you should be doing anyway.
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