Back home, day one of new school term. The pod was awesome. It gave us so much free space in the car, made travelling much more comfortable. Currently covered in over 2000 km of bugsEven if you had to pay $1000 AUD for a roof-top box made of it?
-Gnobuddy
Gnobuddy, if I had to spend that kind of money, I would make one instead. Currently, contemplating getting some HDPE sheets and heat welding a car topper skiff that doubles as storage pod. I am competent at pulling off a project like that. This is the first boat I ever made when I needed to just row out past a coral bommie to fish. I called it the "flying esky". Wouldn't do another in polystyrene though, tupperware would be an easier build requiring minimal finish work and a lot tougher\
Back to work o the amp in between whole house painting and reflooring and front yard plantscaping
You know, you are lucky, that means Australia still hasn't lost all its insects.
I remember that 30 years ago, every long drive left insect carcasses all over the windshield. But no more. Now, when I wash my car, I wash off road dust and soot and black powder (rubber abraded off millions of car tyres). But no insect carcasses.
This was true both in California, and in British Columbia where I live now. And scientists say it's the same all over the world - most of our insects have gone extinct. ( https://www.theguardian.com/environ...ng-insect-numbers-threaten-collapse-of-nature )
That's kinda what I was thinking. Dunno if I have the skills and access to the working space, materials, and tools needed to build one out of HDPE, but old hard-plastic suitcases are out of fashion, and therefore cheap at thrift-stores; a large one of those could serve as a roof pod.
That is a brilliant idea! 👍 If you're the entrepreneurial type, I suspect there would be a market for that product.
Cool Styrofoam boat!
(Now how about that Styrofoam bass guitar speaker?
)-Gnobuddy
Taking some time away from renovations to update the thread. Cabinet construction is now complete for preliminary stage. Amp functions as intended
Currently fitted with guitar input socket, preamp, volume control pot. This feeds the low frequency amp and driver. Tops and tone controls not yet implemented. The amp has been in use for two weeks classes now and teacher is impressed
Also did a demo at the local music shop, they haven’t heard anything this authoritative in a package this small and again very impressed reactions. The shop is looking forward to the tops being implemented to see how it goes as a synth and drum amp. I have been asked to put one in the shop after sourcing a safety certificate
Now I have to sort out the tone electronics. Then I’ll start on the larger project which is a build from scratch using a 10” dvc 400wrms driver and two 6” full ranges in a package not much larger then the Logitech build. I intend to use a four channel tp3255 board for power and trying to find one with a decent build quality. I already have the speaker drivers for this project as well as eight 5670 tubes for the pre and tones
Some pics of the completed cab for the Logitech affectionately called “Lil Terrors z623 Mod”
I would appreciate some feedback good or bad to fine tune the cosmetics. For example, I am changing the side protective plates to a thicker sheet material and using edge trims in tan colour
Currently fitted with guitar input socket, preamp, volume control pot. This feeds the low frequency amp and driver. Tops and tone controls not yet implemented. The amp has been in use for two weeks classes now and teacher is impressed
Also did a demo at the local music shop, they haven’t heard anything this authoritative in a package this small and again very impressed reactions. The shop is looking forward to the tops being implemented to see how it goes as a synth and drum amp. I have been asked to put one in the shop after sourcing a safety certificate
Now I have to sort out the tone electronics. Then I’ll start on the larger project which is a build from scratch using a 10” dvc 400wrms driver and two 6” full ranges in a package not much larger then the Logitech build. I intend to use a four channel tp3255 board for power and trying to find one with a decent build quality. I already have the speaker drivers for this project as well as eight 5670 tubes for the pre and tones
Some pics of the completed cab for the Logitech affectionately called “Lil Terrors z623 Mod”
I would appreciate some feedback good or bad to fine tune the cosmetics. For example, I am changing the side protective plates to a thicker sheet material and using edge trims in tan colour
Wow, that looks great! You have exceptional craftsmanship skills.
IMO, the only thing missing is some sort of logo, especially if one of your creations is going to end up sitting in a music shop where members of the public can see it.
I 3D-printed and then painted a logo for a guitar amp I built to give away to a friend. But with your hands and craftsmanship skills, I have no doubt you can come up with something much prettier than anything out of a 3D printer!
-Gnobuddy
Gnobuddy, thanks for the kinds words. I enjoy working on the aesthetic process. Notice how the side plates form ears or lugs at the top. Originally, I wanted to have a pair of handles cut into that area. But my head section grew too tall, and now that strip of upholstery fabric showing is becoming more and more of an eyesore
Also, the edge moulding trim can only accommodate 4 mm, which forced me to use 6 mm ply as the side plates and rebate the edges 1 mm on each side to flush fit the trim. The Problem I now see with it all assembled is the illusion that the walls are too thin for a bass box. What isn't apparent is that there is the actual original enclosure inside the new shell. This looks wrong
The top plate, the bit of birch plank I had left, was 3 mm too short to fit clean. I rounded over the sides where it almost meets the side plates in an attempt to disguise the gap and fill down the gap with a weather strip. This didn't work and looks like another area not very well implemented
I am going to build a new enclosure based on the Logitech box dimensions and make it just a bit taller to have a partitioned compartment for the head. This will let me do away with extra side plates and allow for a much shorter overall box. Will upholster it the same and run wider trim along the edge of the side panels in a tan colour, The side panels will still stick up like ears but not to form handles. Instead, they will be a touch taller than the knobs for protection
The birch looks ok in that position, especially in its natural colour instead of the silly stain I put on earlier. But, this top area can look better. I am entertaining the thot to use only a thick perspex as top panel. I have a trick where I print knob labels on a transparency in negative and stick it over the perspex panel. I stick aluminium foil under the panel. Then I wrap the whole panel in dark auto window tint film. This gives scratch protection and a dynamic instrument panel. Step drilling into that panel and gluing in LEDs at the appropriate points will make that light up when powered on
If I had a thinner slice of a nice dark heartwood, then it would have made a nice top panel trim. Will go look at some flooring slats at the reuse centre tomorrow
I still need to sit with the materials that I have been collecting for decal work and brew some thots
Also, the edge moulding trim can only accommodate 4 mm, which forced me to use 6 mm ply as the side plates and rebate the edges 1 mm on each side to flush fit the trim. The Problem I now see with it all assembled is the illusion that the walls are too thin for a bass box. What isn't apparent is that there is the actual original enclosure inside the new shell. This looks wrong
The top plate, the bit of birch plank I had left, was 3 mm too short to fit clean. I rounded over the sides where it almost meets the side plates in an attempt to disguise the gap and fill down the gap with a weather strip. This didn't work and looks like another area not very well implemented
I am going to build a new enclosure based on the Logitech box dimensions and make it just a bit taller to have a partitioned compartment for the head. This will let me do away with extra side plates and allow for a much shorter overall box. Will upholster it the same and run wider trim along the edge of the side panels in a tan colour, The side panels will still stick up like ears but not to form handles. Instead, they will be a touch taller than the knobs for protection
The birch looks ok in that position, especially in its natural colour instead of the silly stain I put on earlier. But, this top area can look better. I am entertaining the thot to use only a thick perspex as top panel. I have a trick where I print knob labels on a transparency in negative and stick it over the perspex panel. I stick aluminium foil under the panel. Then I wrap the whole panel in dark auto window tint film. This gives scratch protection and a dynamic instrument panel. Step drilling into that panel and gluing in LEDs at the appropriate points will make that light up when powered on
If I had a thinner slice of a nice dark heartwood, then it would have made a nice top panel trim. Will go look at some flooring slats at the reuse centre tomorrow
I still need to sit with the materials that I have been collecting for decal work and brew some thots
Back to it after being laid up for a while. I had been painting the QLD room and had pulled everything into the room centre. Not being able to properly stand on the stepladder due to existing injuries, I took a fall right on top of a drum set and caught my dressed wound on a drum tuner peg....... not pretty. I still can't get up to much physical work so researching parts to buy for the next project which is the larger amp, the Biggerer
On a positive note, the amp from this thread, the Lil Terror, has been a success so far. My daughter has been progressed to intermediate level early. Today was awards day for the semester. Proud to say, she was again the recipient of the academic gold medal for general school medal. She also has received an award for her bass guitar ability, and she received her bow license for the double bass for the German bow
Earlier in the thread, folks chimed in about how she might be too young and how she may not really be into this. She reads these postings when it up on the home screen. I hope folks would take a moment again to say well done
On a positive note, the amp from this thread, the Lil Terror, has been a success so far. My daughter has been progressed to intermediate level early. Today was awards day for the semester. Proud to say, she was again the recipient of the academic gold medal for general school medal. She also has received an award for her bass guitar ability, and she received her bow license for the double bass for the German bow
Earlier in the thread, folks chimed in about how she might be too young and how she may not really be into this. She reads these postings when it up on the home screen. I hope folks would take a moment again to say well done
A big congratulations to Jiya!
Sorry for the late reply - I've been gone for a few months.
The fact of the matter is that kids with real musical talent often start early, and it's not unusual for them to really get stuck into their instrument, to the point where those apocryphal wild horses couldn't drag them away. For instance, Emily Bear started at age three, and was already a virtuoso pianist and composer at age six:
In Malcom Gladwell's now-famous book "Outliers", he mentions that it takes 10,000 hours of practice to create a musical virtuoso, a top-level athlete, or many other experts in other complex fields. His research also found that the big difference between those who achieved excellence, and those who didn't, usually boiled down to the fact that the former began to voluntarily spend more and more hours practicing their craft as they grew older through their childhoods.
No telling what may or may not be in Jiya's future. But for now, she seems to be doing wonderfully well in school and with her music. And you seem to be doing a wonderful job of supporting and encouraging her. A big thumbs-up to you, too!
-Gnobuddy
Sorry for the late reply - I've been gone for a few months.
From the many, many posts in which you've mentioned your daughter, I get the strong impression that you're a really caring and loving father. I think you (and your wife) are far better qualified than some random stranger on the 'Web, to know whether or not your daughter is actually into her music.Randy Bassinga said:
The fact of the matter is that kids with real musical talent often start early, and it's not unusual for them to really get stuck into their instrument, to the point where those apocryphal wild horses couldn't drag them away. For instance, Emily Bear started at age three, and was already a virtuoso pianist and composer at age six:
In Malcom Gladwell's now-famous book "Outliers", he mentions that it takes 10,000 hours of practice to create a musical virtuoso, a top-level athlete, or many other experts in other complex fields. His research also found that the big difference between those who achieved excellence, and those who didn't, usually boiled down to the fact that the former began to voluntarily spend more and more hours practicing their craft as they grew older through their childhoods.
No telling what may or may not be in Jiya's future. But for now, she seems to be doing wonderfully well in school and with her music. And you seem to be doing a wonderful job of supporting and encouraging her. A big thumbs-up to you, too!
-Gnobuddy
This amp has performed solidly through the school year, but now it's time to retire her. Jiya is going to put our first prototype for our intended commercial bass amp through its paces in her school bass duties, classes, workshops and concerts. 1000wrms as opposed to the current 140wrms in an even smaller package with my Uffornica tube bass channel strip
with my Uffornica tube bass channel strip
@Gnobuddy and @Randy Bassinga, apologies for resurrecting a year-old message but I have a specific question for just the part I quoted: how does a dedicted cheap class-D board replace the need for the filter? It is probably a novice question. I understand it like this: if I send speaker output to several hi-, med-, low-frequency drivers, the sound levels from these drivers will be too different and random, and, also, they will probably shunt/short each other, so, for each driver, I need to remove the part of the spectrum that is not going to be reproduced by this driver. But, if I have a dedicated amp for each driver, each driver sits on the output by itself, and the level can be individually adjusted, so no need for filters.
Is this about right?
In general it doesn't - but the specific board I linked to actually consists of three separate class-D power amplifiers, and also includes active filters. It was designed for "2.1 channel" use, so there is a low pass filter feeding a dedicated subwoofer power amplifier, and two high-pass filters feeding dedicated power amplifiers for the two satellite speakers.
Because those filters are already on the board, you don't have to build additional filters, as Randy was originally planning to do.
If you search for them, you'll find other "2.1" power amplifier PCBs for sale. All the ones I've run across integrate the three necessary filters onto the same PCB.
No, unfortunately it's not that simple.
The trouble is that the subwoofer will make nasty noises at frequencies too high for it to handle properly, while the satellite speakers will make nasty noises at frequencies too low for them to handle safely. They will also rattle themselves to death if fed too much power at frequencies that are too low.
Tweeters are particularly fragile. Good ones are usually designed to work only at frequencies above 2 - 3 kHz. You have to ensure that frequencies below that are removed before the signal reaches the tweeter, otherwise the tweeter will fry in short order.
-Gnobuddy
@Gnobuddy , thanks for the explanation - it makes a lot of sense to me. The impedance of a speaker will be much lower for lower frequencies resulting in high currents and burning the tweeter since it is not designed for those frequencies and that load. On the opposite end, there is probably no danger to the woofer from high frequencies because the impedance will be high, and currents small. But I can see that it might create some unpleasant noise.
The "trick" with 2.1 class-D board makes sense because it has all these filters built in.
A follow up novice question: the concern about routing only the correct frequencies to the drivers seems inportant if I use just the drivers. Does the concern go away if I use the full speaker? Say, I have assorted speakers and woofers, as they come: as I understand, they always have a built-in filter, or at least I can take them apart and look if they do. If i use the speakers with all the electronics they are enclosed with, it should be safe to plug them into any reasonable unfiltered speaker output, right?
The "trick" with 2.1 class-D board makes sense because it has all these filters built in.
A follow up novice question: the concern about routing only the correct frequencies to the drivers seems inportant if I use just the drivers. Does the concern go away if I use the full speaker? Say, I have assorted speakers and woofers, as they come: as I understand, they always have a built-in filter, or at least I can take them apart and look if they do. If i use the speakers with all the electronics they are enclosed with, it should be safe to plug them into any reasonable unfiltered speaker output, right?
You're very welcome. Glad to help when I can.
But speakers are very strange things - they have less than 1% efficiency as a transducer, for starters! They're really much better heaters than speakers, but that's the best we can do. The reasons why tweeters burn if you feed them too-low frequencies are subtler and more complex than just the nature of inductive reactance. More on that in a moment.
One of the reasons for the poor efficiency of speakers is that the wire used for the voice coil is necessarily very thin (to fit in the tiny magnetic gap), and that means it has quite a bit of resistance. At most frequencies within the speaker's range, the voice coil resistance actually dominates the total impedance. For example, a nominally 8-ohm speaker typically has about 6 ohms of pure resistance. That means most of the input power is wasted as heat, rather than turned into movement of the voice coil.
It also means the speaker impedance is not, in fact, proportional to frequency - not, at least, over most of the range of frequencies it will be used at.
The other very non-obvious thing about loudspeakers is that, all else being the same, the sound pressure level generated by a vibrating disc (like a speaker cone) is proportional to the square of the frequency. (With caveats - this does apply over most of the usable frequency range of a speaker, though.)
Bernoulli's law gives you the first factor of "f" - pressure is proportional to velocity, not to displacement. The second factor of "f" comes from the fact that the speaker diameter is considerably smaller than the wavelength of the sound it emits (except at the very highest frequencies in the audio range). If you look up radiative coupling efficiency for a small antenna generating radio waves, you'll see that it's proportional to frequency. A speaker cone is a small acoustic antenna generating radio waves, and essentially the same math applies.
Now you put the two factors of "f" together, and you get the f^2 dependency I mentioned above.
At first sight, then, you'd expect a loudspeaker to produce an audio frequency response that rises steeply, i.e. proportional to the square of the input frequency. You'd expect a shrill screech, with negligible bass response.
But this doesn't happen. Why?
The solution to the conundrum is almost comical. The moving mass of a speaker (cone, coil, dust cap, spider, part of the surround) interacts with the stiffness of its suspension (spider, surround) to create a mechanical resonance. By suitable choice of mass and springiness (spring constant in physics terms), the resonance frequency is set to the bottom end of that speaker's usable frequency range. The resonance is quite heavily damped, partly from mechanical losses in the surround and spider, mostly by the induced current in the voice coil, which always opposes it's direction of motion - Lenz' law.)
If you work out the mechanical transfer function from input voltage to cone displacement, it will have a flat frequency response below this resonance frequency. Above the resonance, however, the cone displacement falls as 1/(frequency squared).
And so the very simple solution to the conundrum is to only use the loudspeaker at frequencies above its fundamental mechanical resonance. Cone excursion naturally falls as 1/f^2 above that, while the SPL (sound pressure level) generated in front of the cone rises as f^2. The two dependencies cancel, and to a good approximation, you get a flat frequency response (of SPL vs frequency)!
Note, however, that speaker cone excursion still has to quadruple every time you halve the input frequency.
This is usually the limiting factor regarding how low (in frequency) a speaker can go without damaging itself. Push it too low, and cone excursion can get large enough to cause mechanical damage. The problem is compounded by the fact that the human ear has poor sensitivity to bass frequencies, so the temptation is to turn up the volume. The combination of high input power, and low frequencies, demands extreme excursions of the cone, and the speaker will either rattle or tear itself to death, or the voice coil will fry from the heat.
At the other end of the frequency range, you encounter different problems. One of them is mechanical stiffness of the cone. A speaker cone is ideally infinitely stiff - the whole thing moves as a single rigid object. This is usually true at low frequencies, but as the frequency of operation goes up, the transit time of acoustic waves in the cone material becomes increasingly significant - parts of the cone start to vibrate out of phase with other parts. This is called "cone breakup", and it results in erratic peaks and dips in the speaker frequency response.
The other high frequency problem is that the wavelength of the sound waves gets smaller and smaller as frequencies rise. At some sufficiently high frequency the speaker diameter starts to approach the wavelength of the sound. Above this point the radiative coupling efficiency no longer has that f^2 frequency dependence, and also the radiation pattern starts to "beam" like a lighthouse.
So if we want good quality audio from a loudspeaker, it has to be strongly built , with a big heavy voice coil capable of handling lots of power, and a big floppy surround allowing for a low mechanical resonance frequency and large excursions at low frequencies. We also need a large cone diameter in order to effectively radiate low frequencies into the air.
However, the speaker has to be very light in order to respond rapidly to high frequencies, and it needs a very small cone diameter to avoid "beaming" of treble frequencies. A light voice coil necessarily uses very thin wire, and has low thermal mass, limiting how much electrical power input (heat) it can tolerate before burning.
There is no way to reconcile these conflicting requirements, which is why we have subwoofers, woofers, midranges, and tweeters, each optimized to work in a different (but overlapping) frequency band.
So why does a tweeter burn if you feed it frequencies that are too low? Part of the problem is too much mechanical cone excursion, which can tear the tweeter's moving parts apart.
Another part of the problem is that the average power in music is much higher at lower frequencies, and if we let these powerful low frequency signals into the tweeter, they will not only tear apart the suspension, they will also overheat and burn out the tweeter voice coil.
By now you've probably figured out the problem with allowing high frequencies into the subwoofer - cone breakup, and beaming. You'll get some sound out of it, but it won't be good sound - you'll have erratic frequency response, limited output, and acoustic beaming (poor dispersion of sound).
There are exceptions: some speakers designed for in-car audio or in-wall background music combine a tweeter, a woofer, and a crude high-pass electrical filter into one single unit.
Most of the time, the filter consists of nothing more than a single capacitor in series with the tweeter, reducing the amount of low-frequency energy that reaches it. This is better than nothing, but only in the same sense that eating worms is better than starving to death. The reasons are too long to go into here - they have to do with the various idiosyncracies of speaker drivers.
But the bottom line is that yes, you can feed full-bandwidth audio into something like this, and if you are respectful of power handling limitations, the speaker should survive.
It will not be capable of getting anywhere near as loud as a good guitar amp, and even less capable of getting anywhere near as loud as a bass guitar amp. But if all you want is relatively low volume in your home, it might do what you want.
Ironically, better quality speakers (ones made for Hi-Fi in the days when people still cared about good sound) are likely to be more fragile than the boom-box speakers. Better tweeters are generally much more fragile, better woofers have lower resonance frequencies, and are more easily rattled to death by excessive low-frequency electrical input.
Some of the concerns other people raised on your other thread are quite valid - it IS really easy to destroy Hi-Fi speakers by trying to play guitars or basses through them. This is not because Hi-Fi speakers are worse than speakers designed for live music - it's because Hi-Fi speakers are more delicate, but produce better sound quality, while P.A. speakers are more robust, but produce worse sound quality. It's a compromise, a trade-off.
That said, I've obtained quite good results playing electric guitar into a small pair of thrift-store "mini Hi-Fi" speakers driven by a little class-D power amp from Amazon. The key to good sound is the addition of a Flamma FS06 Preamp between guitar and power amp.
The Flamma includes what is called "speaker emulation" in guitar lingo; basically it includes a filter that mimics the very peculiar frequency response of a good guitar speaker mounted in its "cab" (enclosure). This protected the tweeters in my thrift-store speakers.
I have no affiliation with Flamma whatsoever, to be clear. But their little Preamp is, in my opinion, a really amazing product, in the sense that it produces very believable guitar amplifier sounds from a little digital signal processor in a box that would fit into your pants pocket. Currently priced at $76 USD on Amazon.com: https://www.amazon.com/FLAMMA-Digital-Cabinet-Simulation-Saveable/dp/B08LMLRQ44/?th=1
Here's Brett Kingman's quick demo of a Flamma FS06:
(Keep in mind Kingman is an incredibly good guitarist, and he does use some additional effects pedals in that video for some of the sounds.)
It's probably a good idea to look for some similar pedal or multiFX processor for your daughter's bass. That is more likely to get you acceptable sound than just plugging the bass into a subwoofer. Again, only for home practice, at SPL levels much lower than most musicians want.
I do tinker with bass guitar, but the bass-related equipment I own is over a decade old, and I'm not up to date with suitable budget-priced contemporary gear that also has good sound quality.
It's worth also considering a second-hand Boss Katana 50 (for your guitar) and a used Fender Rumble series bass amp for your daughter's bass. If one or both of you get serious about your instrument, those choices will take you a lot further. The budget is a lot more than a Flamma pedal and a class D amplifier from Amazon, though.
-Gnobuddy
That's a perfectly reasonable assumption when you think of the speaker voice coil as an inductance (i.e. XL = j * 2 * p i * f * L ).Crocobar said:
But speakers are very strange things - they have less than 1% efficiency as a transducer, for starters! They're really much better heaters than speakers, but that's the best we can do. The reasons why tweeters burn if you feed them too-low frequencies are subtler and more complex than just the nature of inductive reactance. More on that in a moment.
One of the reasons for the poor efficiency of speakers is that the wire used for the voice coil is necessarily very thin (to fit in the tiny magnetic gap), and that means it has quite a bit of resistance. At most frequencies within the speaker's range, the voice coil resistance actually dominates the total impedance. For example, a nominally 8-ohm speaker typically has about 6 ohms of pure resistance. That means most of the input power is wasted as heat, rather than turned into movement of the voice coil.
It also means the speaker impedance is not, in fact, proportional to frequency - not, at least, over most of the range of frequencies it will be used at.
The other very non-obvious thing about loudspeakers is that, all else being the same, the sound pressure level generated by a vibrating disc (like a speaker cone) is proportional to the square of the frequency. (With caveats - this does apply over most of the usable frequency range of a speaker, though.)
Bernoulli's law gives you the first factor of "f" - pressure is proportional to velocity, not to displacement. The second factor of "f" comes from the fact that the speaker diameter is considerably smaller than the wavelength of the sound it emits (except at the very highest frequencies in the audio range). If you look up radiative coupling efficiency for a small antenna generating radio waves, you'll see that it's proportional to frequency. A speaker cone is a small acoustic antenna generating radio waves, and essentially the same math applies.
Now you put the two factors of "f" together, and you get the f^2 dependency I mentioned above.
At first sight, then, you'd expect a loudspeaker to produce an audio frequency response that rises steeply, i.e. proportional to the square of the input frequency. You'd expect a shrill screech, with negligible bass response.
But this doesn't happen. Why?
The solution to the conundrum is almost comical. The moving mass of a speaker (cone, coil, dust cap, spider, part of the surround) interacts with the stiffness of its suspension (spider, surround) to create a mechanical resonance. By suitable choice of mass and springiness (spring constant in physics terms), the resonance frequency is set to the bottom end of that speaker's usable frequency range. The resonance is quite heavily damped, partly from mechanical losses in the surround and spider, mostly by the induced current in the voice coil, which always opposes it's direction of motion - Lenz' law.)
If you work out the mechanical transfer function from input voltage to cone displacement, it will have a flat frequency response below this resonance frequency. Above the resonance, however, the cone displacement falls as 1/(frequency squared).
And so the very simple solution to the conundrum is to only use the loudspeaker at frequencies above its fundamental mechanical resonance. Cone excursion naturally falls as 1/f^2 above that, while the SPL (sound pressure level) generated in front of the cone rises as f^2. The two dependencies cancel, and to a good approximation, you get a flat frequency response (of SPL vs frequency)!
Note, however, that speaker cone excursion still has to quadruple every time you halve the input frequency.
This is usually the limiting factor regarding how low (in frequency) a speaker can go without damaging itself. Push it too low, and cone excursion can get large enough to cause mechanical damage. The problem is compounded by the fact that the human ear has poor sensitivity to bass frequencies, so the temptation is to turn up the volume. The combination of high input power, and low frequencies, demands extreme excursions of the cone, and the speaker will either rattle or tear itself to death, or the voice coil will fry from the heat.
At the other end of the frequency range, you encounter different problems. One of them is mechanical stiffness of the cone. A speaker cone is ideally infinitely stiff - the whole thing moves as a single rigid object. This is usually true at low frequencies, but as the frequency of operation goes up, the transit time of acoustic waves in the cone material becomes increasingly significant - parts of the cone start to vibrate out of phase with other parts. This is called "cone breakup", and it results in erratic peaks and dips in the speaker frequency response.
The other high frequency problem is that the wavelength of the sound waves gets smaller and smaller as frequencies rise. At some sufficiently high frequency the speaker diameter starts to approach the wavelength of the sound. Above this point the radiative coupling efficiency no longer has that f^2 frequency dependence, and also the radiation pattern starts to "beam" like a lighthouse.
So if we want good quality audio from a loudspeaker, it has to be strongly built , with a big heavy voice coil capable of handling lots of power, and a big floppy surround allowing for a low mechanical resonance frequency and large excursions at low frequencies. We also need a large cone diameter in order to effectively radiate low frequencies into the air.
However, the speaker has to be very light in order to respond rapidly to high frequencies, and it needs a very small cone diameter to avoid "beaming" of treble frequencies. A light voice coil necessarily uses very thin wire, and has low thermal mass, limiting how much electrical power input (heat) it can tolerate before burning.
There is no way to reconcile these conflicting requirements, which is why we have subwoofers, woofers, midranges, and tweeters, each optimized to work in a different (but overlapping) frequency band.
So why does a tweeter burn if you feed it frequencies that are too low? Part of the problem is too much mechanical cone excursion, which can tear the tweeter's moving parts apart.
Another part of the problem is that the average power in music is much higher at lower frequencies, and if we let these powerful low frequency signals into the tweeter, they will not only tear apart the suspension, they will also overheat and burn out the tweeter voice coil.
By now you've probably figured out the problem with allowing high frequencies into the subwoofer - cone breakup, and beaming. You'll get some sound out of it, but it won't be good sound - you'll have erratic frequency response, limited output, and acoustic beaming (poor dispersion of sound).
In general, they do not include any filter.Crocobar said:
There are exceptions: some speakers designed for in-car audio or in-wall background music combine a tweeter, a woofer, and a crude high-pass electrical filter into one single unit.
Most of the time, the filter consists of nothing more than a single capacitor in series with the tweeter, reducing the amount of low-frequency energy that reaches it. This is better than nothing, but only in the same sense that eating worms is better than starving to death. The reasons are too long to go into here - they have to do with the various idiosyncracies of speaker drivers.
If you're talking about something like a boombox speaker (often found at thrift stores these days), yes, you're right. The manufacturer has typically mounted a woofer and a tweeter inside, along with some sort of high-pass filter for the tweeter. Most of the time the tweeter is a piezo tweeter (cheap, robust, but nasty sounding). Most of the time the high-pass filter is a series capacitor (cheap, but works very poorly.)Crocobar said:
But the bottom line is that yes, you can feed full-bandwidth audio into something like this, and if you are respectful of power handling limitations, the speaker should survive.
It will not be capable of getting anywhere near as loud as a good guitar amp, and even less capable of getting anywhere near as loud as a bass guitar amp. But if all you want is relatively low volume in your home, it might do what you want.
Ironically, better quality speakers (ones made for Hi-Fi in the days when people still cared about good sound) are likely to be more fragile than the boom-box speakers. Better tweeters are generally much more fragile, better woofers have lower resonance frequencies, and are more easily rattled to death by excessive low-frequency electrical input.
Some of the concerns other people raised on your other thread are quite valid - it IS really easy to destroy Hi-Fi speakers by trying to play guitars or basses through them. This is not because Hi-Fi speakers are worse than speakers designed for live music - it's because Hi-Fi speakers are more delicate, but produce better sound quality, while P.A. speakers are more robust, but produce worse sound quality. It's a compromise, a trade-off.
That said, I've obtained quite good results playing electric guitar into a small pair of thrift-store "mini Hi-Fi" speakers driven by a little class-D power amp from Amazon. The key to good sound is the addition of a Flamma FS06 Preamp between guitar and power amp.
The Flamma includes what is called "speaker emulation" in guitar lingo; basically it includes a filter that mimics the very peculiar frequency response of a good guitar speaker mounted in its "cab" (enclosure). This protected the tweeters in my thrift-store speakers.
I have no affiliation with Flamma whatsoever, to be clear. But their little Preamp is, in my opinion, a really amazing product, in the sense that it produces very believable guitar amplifier sounds from a little digital signal processor in a box that would fit into your pants pocket. Currently priced at $76 USD on Amazon.com: https://www.amazon.com/FLAMMA-Digital-Cabinet-Simulation-Saveable/dp/B08LMLRQ44/?th=1
Here's Brett Kingman's quick demo of a Flamma FS06:
(Keep in mind Kingman is an incredibly good guitarist, and he does use some additional effects pedals in that video for some of the sounds.)
It's probably a good idea to look for some similar pedal or multiFX processor for your daughter's bass. That is more likely to get you acceptable sound than just plugging the bass into a subwoofer. Again, only for home practice, at SPL levels much lower than most musicians want.
I do tinker with bass guitar, but the bass-related equipment I own is over a decade old, and I'm not up to date with suitable budget-priced contemporary gear that also has good sound quality.
It's worth also considering a second-hand Boss Katana 50 (for your guitar) and a used Fender Rumble series bass amp for your daughter's bass. If one or both of you get serious about your instrument, those choices will take you a lot further. The budget is a lot more than a Flamma pedal and a class D amplifier from Amazon, though.
-Gnobuddy
@Gnobuddy , once again - thanks! This is very detailed and really up my alley! Now that I feel like I got some basics, I will try to describe - in a separate thread - what I specifically have in mind, and I will ask you and everybody to critique it.
Yes! In fact, I do have a minimal multi-effect contraptions for both bass (this) and acoustic (this). The bass one also works fairly ok with the electric guitar (to my unexperienced ear), and I got this simple fuzz pedal from the same brand - mostly because of the sentimental value since Gilmour supposedly uses fuzz rather than distortion.
I never really planned to plug any of my instruments very directly into a subwoofer or speaker. In fact, I assumed that one does not do that because the electric guitar tone needs to be created somehow. In hindsight, it was a bad assumption - I did not realize that traditionally, people used the amps and cabinets to create tone!
The last component that I would like is a mixer - I also got that idea from your conversation with Randy from a year-old thread. But let me stop hijacking this thread - I will create a separate one for my imagined setup.
Thanks again!
This is roughly what I had in mind - except I did not know about the Flamma preamp until I learned about it from you in a different thread. My thought was that I would create tone with pedals/effects, and I would amplify it with a transparent PA as needed. It took me a while to realize that this is not a very natural way of thinking in the electric guitar world. Tone and amplification usually go together in people's minds it seems.
Yes! In fact, I do have a minimal multi-effect contraptions for both bass (this) and acoustic (this). The bass one also works fairly ok with the electric guitar (to my unexperienced ear), and I got this simple fuzz pedal from the same brand - mostly because of the sentimental value since Gilmour supposedly uses fuzz rather than distortion.
I never really planned to plug any of my instruments very directly into a subwoofer or speaker. In fact, I assumed that one does not do that because the electric guitar tone needs to be created somehow. In hindsight, it was a bad assumption - I did not realize that traditionally, people used the amps and cabinets to create tone!
The last component that I would like is a mixer - I also got that idea from your conversation with Randy from a year-old thread. But let me stop hijacking this thread - I will create a separate one for my imagined setup.
Thanks again!
Cool man, you should be able to have a close listen to the lil video that I linked in pm. What do you think tone and authority wise? I can't hear any mic rumbles or anything that peeps advising low filter keep saying is needed. Tone sounds fine to me too and nothing like what people think would happen straight into a sub. Deep low bass records just fine from a subwoofer driver without any filters. I have many such recordings, but wary of posting vids of any kids. Bottom line is there is nothing better than first-hand experience. Everything else is just speculation, never mind how educated
At home, I use a pair of Alesis Monitor One MkII near-field studio monitors as my main speakers, with a Velodyne subwoofer filling in bass below 70 Hz or so.
It's only the smallest little 10" sub Velodyne makes (made?), but it does a pretty good job reproducing deep low-frequency rumbling sounds from today's movies, and I can also clearly hear low notes from a 5-string bass guitar.
A few years ago I generated some low-frequency sine WAV files using Audacity, and tried playing them through the sub. IIRC, in our living room, the sub does a pretty good job down to around 35 Hz.
IMO the Monitor One Mk II are very nice speakers (and I once shared an office with the two engineers who designed them, so I got an inside look at how hard they worked at getting surprisingly good performance out of them on a budget price).
I was lucky and got my monitors at an absurdly low price because passive studio monitors had recently gone out of fashion, having been replaced by active ones.
-Gnobuddy