So, having built some fairly powerful PA speakers*, I'm also going to build something much smaller and lighter, for those smaller gigs where you just need to reinforce acoustic guitar and vocals in a coffee shop.
Having looked around online, lots of people are using tiny line arrays with around 6 full-range drivers and a small sub. Bose L1, RCF Evox, that sort of thing.
Guess what I'm planning on building.
I happened to have 4x Bose 2.5" full-range drivers around. They're from the old SoundDock series. I found them to sound decent enough in that plastic enclosure (given by family - the iPod dock was broken) that I decided to keep hold of them, maybe for a little PC system or something. Anyway, I put all four in a cardboard box, taped them in place, wired them all in parallel to one side of an EP1500 (1ohm load, since they're 4ohm drivers), and had a listen. The result was pretty good. Not something you'd want to keep around, but there's definitely potential there. Quite a lot of power handling, except for at LF where (I suspect) air leaks produced lots of cone excursion but little below 100Hz or so. Through the mid-high range, quite a lot of output was available. To test further, I put a 12" in a ported box on the other channel of the EP1500. There was something of a sensitivity descrepancy, but once that was sorted, a ~200Hz crossover gave the little FR units more power handling.
I did note that moving off axis along the length of the array produced interesting effects: when your ear is no longer in-line with one of the drivers, HF output drops hugely. This led me to investigate the minimum number of drivers that would be needed to ensure that people stood up or sat down, and have them all in the vertical coverage. Measured my head height sat down, stood up, did a bit of rounding and ended up at 12 drivers.
This was enough for me to go and find 8 more drivers.
A couple of the frames were bent in transit, but the cones move freely so I'm confident they can be straightened out without breaking anything.
12 drivers is quite a long line, so, in order to contradict my findings about moving off the end of the line with the 4-driver array, I fired up The Edge, which is a rather nice piece of software, to simulate what the long array will be doing at different distances and listening positions.
Here's the 840mm array (12 drivers, 70mm square frames) at 8m distance:
Pretty good, if you ignore the baffle step effects. 8m is pretty far away for these gigs, though, so lets get a little closer. 2m:
Yuck. We've got 10dB difference from 1kHz to 6kHz. Well, I've heard about frequency-tapering arrays. That is, reducing the line length as frequency goes up.
Lets disconnect the top and bottom three drivers, so we're running 6 drivers
This is at 8m again. Better in the HF than the long array at the same distance.
Lets try closer. 2m:
Much better than the full-length array at HF. To achieve something like this, I'd add inductors to roll off the HF, starting around 1kHz). The phase shifts might do interesting things to the vertical polar pattern, though.
So, it looks like there's a balancing act to be done here. It seems that you need to be standing ~10x the line length away before everything sums nicely to give a good HF response. Tapering the array might help, but (and its a big but) the vertical dispersion is tight either way, and moving from sitting to standing would produce huge changes in the sound. I think some experimentation will be needed here. Maybe I could run only a couple of the drivers into the HF, and roll off the rest...
Anyway, that's where the experimentation will be.
Once I've got something I'm happy with (if I end up happy with it at all), I'll get myself a powered sub that has satellite outputs and an active crossover, and call it good. I might put a Behringer DEQ2496 in there if any serious EQ is needed, but I'm hoping to get away without it, just using a little notepad mixer for those tiny gigs. I'll test for SPL with the 12"s or 15"s I have to get an idea of what'd be required, but there's a few models (8", 12", 15") that I could go for. The array will be wired 3 drivers in series, two groups in parallel, giving a pair of 6ohm loads, which should be nice and easy for the built-in amps.
That's all for now. Interested to hear what you all think. The resale on these drivers is pretty good, so if I decide this isn't for me, its only time and wood used.
Chris
*http://www.diyaudio.com/forums/pa-systems/271132-chris661s-pa-system-thread-6.html#post4737809
Having looked around online, lots of people are using tiny line arrays with around 6 full-range drivers and a small sub. Bose L1, RCF Evox, that sort of thing.
Guess what I'm planning on building.
I happened to have 4x Bose 2.5" full-range drivers around. They're from the old SoundDock series. I found them to sound decent enough in that plastic enclosure (given by family - the iPod dock was broken) that I decided to keep hold of them, maybe for a little PC system or something. Anyway, I put all four in a cardboard box, taped them in place, wired them all in parallel to one side of an EP1500 (1ohm load, since they're 4ohm drivers), and had a listen. The result was pretty good. Not something you'd want to keep around, but there's definitely potential there. Quite a lot of power handling, except for at LF where (I suspect) air leaks produced lots of cone excursion but little below 100Hz or so. Through the mid-high range, quite a lot of output was available. To test further, I put a 12" in a ported box on the other channel of the EP1500. There was something of a sensitivity descrepancy, but once that was sorted, a ~200Hz crossover gave the little FR units more power handling.
I did note that moving off axis along the length of the array produced interesting effects: when your ear is no longer in-line with one of the drivers, HF output drops hugely. This led me to investigate the minimum number of drivers that would be needed to ensure that people stood up or sat down, and have them all in the vertical coverage. Measured my head height sat down, stood up, did a bit of rounding and ended up at 12 drivers.
This was enough for me to go and find 8 more drivers.
A couple of the frames were bent in transit, but the cones move freely so I'm confident they can be straightened out without breaking anything.
12 drivers is quite a long line, so, in order to contradict my findings about moving off the end of the line with the 4-driver array, I fired up The Edge, which is a rather nice piece of software, to simulate what the long array will be doing at different distances and listening positions.
Here's the 840mm array (12 drivers, 70mm square frames) at 8m distance:
Pretty good, if you ignore the baffle step effects. 8m is pretty far away for these gigs, though, so lets get a little closer. 2m:
Yuck. We've got 10dB difference from 1kHz to 6kHz. Well, I've heard about frequency-tapering arrays. That is, reducing the line length as frequency goes up.
Lets disconnect the top and bottom three drivers, so we're running 6 drivers
This is at 8m again. Better in the HF than the long array at the same distance.
Lets try closer. 2m:
Much better than the full-length array at HF. To achieve something like this, I'd add inductors to roll off the HF, starting around 1kHz). The phase shifts might do interesting things to the vertical polar pattern, though.
So, it looks like there's a balancing act to be done here. It seems that you need to be standing ~10x the line length away before everything sums nicely to give a good HF response. Tapering the array might help, but (and its a big but) the vertical dispersion is tight either way, and moving from sitting to standing would produce huge changes in the sound. I think some experimentation will be needed here. Maybe I could run only a couple of the drivers into the HF, and roll off the rest...
Anyway, that's where the experimentation will be.
Once I've got something I'm happy with (if I end up happy with it at all), I'll get myself a powered sub that has satellite outputs and an active crossover, and call it good. I might put a Behringer DEQ2496 in there if any serious EQ is needed, but I'm hoping to get away without it, just using a little notepad mixer for those tiny gigs. I'll test for SPL with the 12"s or 15"s I have to get an idea of what'd be required, but there's a few models (8", 12", 15") that I could go for. The array will be wired 3 drivers in series, two groups in parallel, giving a pair of 6ohm loads, which should be nice and easy for the built-in amps.
That's all for now. Interested to hear what you all think. The resale on these drivers is pretty good, so if I decide this isn't for me, its only time and wood used.
Chris
*http://www.diyaudio.com/forums/pa-systems/271132-chris661s-pa-system-thread-6.html#post4737809
You're experiencing the inherited characteristics of line arrays.
Vertical dispersion is pretty much limited to the height of the arrays.
The drop in HF is called comb filtering.
Here's a good read on line arrays that will make you understand why the things you measured are happening:
James Griffin's
http://www.audioroundtable.com/misc/nflawp.pdf
Vertical dispersion is pretty much limited to the height of the arrays.
The drop in HF is called comb filtering.
Here's a good read on line arrays that will make you understand why the things you measured are happening:
James Griffin's
http://www.audioroundtable.com/misc/nflawp.pdf
Hi,
I've been through that paper a couple of times. I'd like to use an array using full-range drivers. The LF is taken care of, so I don't need the extra power handling from going to a 3-way design. The arrays covered there are designed for near field use, too. Far-field will have its own set of compromises.
Having connected it all up again, the problem I'm finding is that the HF response varies considerably with distance, over the distances in which this system might be used.
Used the DEQ2496 and an ECM8000 to force a flat response, and it sounded pretty good. Moved a few metres further back, and suddenly the treble is excessive.
EQing the treble so it's more palatable at the further distance, and nearer sounds a little dull, but not too bad. Needed around 6dB of cut.
This project will be very much a "feeling my way around" sort of thing. I like the design idea - something tallish and very slim that can go surprisingly loud. There are lots of compromises to be made, and I plan to find some of them, and perhaps even work around some of those. I could, for instance, frequency-shade the whole thing, aiming for maximum power handling while ensuring the array remains effectively a point source, by rolling off drivers higher and higher until the top one or two drivers, which run full-range. Might not be enough HF power handling, but we'll see.
Chris
I've been through that paper a couple of times. I'd like to use an array using full-range drivers. The LF is taken care of, so I don't need the extra power handling from going to a 3-way design. The arrays covered there are designed for near field use, too. Far-field will have its own set of compromises.
Having connected it all up again, the problem I'm finding is that the HF response varies considerably with distance, over the distances in which this system might be used.
Used the DEQ2496 and an ECM8000 to force a flat response, and it sounded pretty good. Moved a few metres further back, and suddenly the treble is excessive.
EQing the treble so it's more palatable at the further distance, and nearer sounds a little dull, but not too bad. Needed around 6dB of cut.
This project will be very much a "feeling my way around" sort of thing. I like the design idea - something tallish and very slim that can go surprisingly loud. There are lots of compromises to be made, and I plan to find some of them, and perhaps even work around some of those. I could, for instance, frequency-shade the whole thing, aiming for maximum power handling while ensuring the array remains effectively a point source, by rolling off drivers higher and higher until the top one or two drivers, which run full-range. Might not be enough HF power handling, but we'll see.
Chris
I suggest the original paper on line array by David Smith. It is fantastic.
http://www.diyaudio.com/forums/mult...th-transducers-line-arrays-6.html#post2257395
http://www.diyaudio.com/forums/mult...th-transducers-line-arrays-6.html#post2257395
Probably, but not for certain, you're way better off letting some other driver handle the highs - like a proper compression driver + horn. Or a multi-cell, or an arrangement like that, given that you are talking "small" rooms.
Also the BOSE drivers probably do not have sufficient power handling and sensitivity to get your the SPL you would want.
Remember too, that BOSE usually EQ's the carp out of their drivers.
I'd guesstimate that you'd get reasonably good sound with a roll-off in the 2.5K range, handing over to something with proper dispersion for the highs, up top of the array, and then adding in some EQ to get it flat down to ~200-250Hz or there abouts.
More needs to be defined WRT the project, like size of the room(s), max SPL required, bandwidth required, power available, physical placement(s) available, and the WEIGHT that is transportable.
Also the BOSE drivers probably do not have sufficient power handling and sensitivity to get your the SPL you would want.
Remember too, that BOSE usually EQ's the carp out of their drivers.
I'd guesstimate that you'd get reasonably good sound with a roll-off in the 2.5K range, handing over to something with proper dispersion for the highs, up top of the array, and then adding in some EQ to get it flat down to ~200-250Hz or there abouts.
More needs to be defined WRT the project, like size of the room(s), max SPL required, bandwidth required, power available, physical placement(s) available, and the WEIGHT that is transportable.
From what I can tell, there's quite a lot of these little line array PA systems in use. The Bose and RCF ones I linked are a couple of examples - there's lots more.
These particular Bose drivers sound pretty decent. I wouldn't have kept them if they were anything like the drivers they use in the 901s. I've also ordered a couple of spares, and will be conducting some power handling tests. I'd guess in the region of 10-15w, and of the order of 85dB@1w sensitivity. Given I'll be using 12 of them, that's quite a gain in power handling and sensitivity, around 95dB@1w, and 100-150w power handling. Should be a match for an older-model 12" top speaker in terms of output, but in a smaller package.
I plan on buying an active sub that can drive satellites, so I will make sure power available is adequate. Weight is flexible. Less is more, but I can move 90lb cabinets alone, and I don't think these will come close to that.
The rest of it, I don't mind so much. I haven't played around with speakers like these much, so it'll be a learning experience as much as anything else.
I do have some small compression drivers and horns around, so might give them a try once I've knocked together a prototype.
Chris
These particular Bose drivers sound pretty decent. I wouldn't have kept them if they were anything like the drivers they use in the 901s. I've also ordered a couple of spares, and will be conducting some power handling tests. I'd guess in the region of 10-15w, and of the order of 85dB@1w sensitivity. Given I'll be using 12 of them, that's quite a gain in power handling and sensitivity, around 95dB@1w, and 100-150w power handling. Should be a match for an older-model 12" top speaker in terms of output, but in a smaller package.
I plan on buying an active sub that can drive satellites, so I will make sure power available is adequate. Weight is flexible. Less is more, but I can move 90lb cabinets alone, and I don't think these will come close to that.
The rest of it, I don't mind so much. I haven't played around with speakers like these much, so it'll be a learning experience as much as anything else.
I do have some small compression drivers and horns around, so might give them a try once I've knocked together a prototype.
Chris
Watch the excursion on those little drivers. I'd be surprised if they would handle full power even at 200Hz. Depends how much power you actually need I guess!
I'd be surprised, too.
I'm planning on putting some DSP on the front end of this setup, so I'll be making sure to set some limiters and/or dynamic EQs.
Maybe I could open the active sub and get the XO up to 250Hz...
I've been working a lot recently, but found a couple of hours to pick up a Dremel, vertical cutting guide, and lots of 90mm wide strips of 5mm MDF.
Unlike my previous projects, this one will, unfortunately, be painted black.
Chris
I'm planning on putting some DSP on the front end of this setup, so I'll be making sure to set some limiters and/or dynamic EQs.
Maybe I could open the active sub and get the XO up to 250Hz...
I've been working a lot recently, but found a couple of hours to pick up a Dremel, vertical cutting guide, and lots of 90mm wide strips of 5mm MDF.
Unlike my previous projects, this one will, unfortunately, be painted black.
Chris
Tested one of the drivers to destruction today.
These are 4ohm drivers (DCR is ~3.2ohm), and the test unit was free-air.
Set off at 6v, 80Hz. Lots of cone excursion. I realised this might be somewhere around Fs, so I moved the frequency up to 250Hz, which ought to be in the low-impedance range.
I set off at 8v, which was fine. 10v, fine.
12v increased to 15v over 5 minutes or so, still fine. Sat 15v for 5 minutes or so. Still fine, though the magnet was getting warm (~30C). Warm glue smell when you get close to the driver.
Remember this is with a sine wave test signal.
I got impatient, and did a (relatively) high-power test, without letting anything cool down.
20v RMS sine wave.
52 seconds later, we had smoke. 30s later, no more noise, and a hot magnet.
Cone excursion got to around 9mm p/p, but there was quite a lot of mechanical noise. These are linear around 5mm p/p, tops.
Given its a 2.5" driver with a 0.75" voicecoil, I was very impressed with how much power this unit stood up to. I'd say its safe to take 10v sine waves pretty indefinitely, which is around 25w. Pink noise has a 3dB higher crest factor than sine waves, so this would be a 50w pink noise rated driver (albeit not tested for the 2 hours or so that the AES standard tests require).
I'm using 12 of these drivers in the column, so thermally I'd be safe occasionally clipping a 600w amplifier, though that amplifier driven with full-power sine waves would burn the lot. That's to say nothing of power compression.
The active sub I'm looking at for this setup is this one:
the box CL 112 Sub MK II - Thomann UK
I expect it'll sound alright, though not fantastic. With some EQing and perhaps a different driver (got some 500w Fane 12"s lying around), I can probably get some decent sounds out of it.
Another avenue to explore would be whether to go sealed or ported. A few holes drilled in the back (perhaps doubling up the material thickness) would put tuning in the 120Hz range, which would certainly gain some mechanical power handling, and also some ventilation.
Things to do. I'll try to make a prototype baffle soon.
Chris
These are 4ohm drivers (DCR is ~3.2ohm), and the test unit was free-air.
Set off at 6v, 80Hz. Lots of cone excursion. I realised this might be somewhere around Fs, so I moved the frequency up to 250Hz, which ought to be in the low-impedance range.
I set off at 8v, which was fine. 10v, fine.
12v increased to 15v over 5 minutes or so, still fine. Sat 15v for 5 minutes or so. Still fine, though the magnet was getting warm (~30C). Warm glue smell when you get close to the driver.
Remember this is with a sine wave test signal.
I got impatient, and did a (relatively) high-power test, without letting anything cool down.
20v RMS sine wave.
52 seconds later, we had smoke. 30s later, no more noise, and a hot magnet.
Cone excursion got to around 9mm p/p, but there was quite a lot of mechanical noise. These are linear around 5mm p/p, tops.
Given its a 2.5" driver with a 0.75" voicecoil, I was very impressed with how much power this unit stood up to. I'd say its safe to take 10v sine waves pretty indefinitely, which is around 25w. Pink noise has a 3dB higher crest factor than sine waves, so this would be a 50w pink noise rated driver (albeit not tested for the 2 hours or so that the AES standard tests require).
I'm using 12 of these drivers in the column, so thermally I'd be safe occasionally clipping a 600w amplifier, though that amplifier driven with full-power sine waves would burn the lot. That's to say nothing of power compression.
The active sub I'm looking at for this setup is this one:
the box CL 112 Sub MK II - Thomann UK
I expect it'll sound alright, though not fantastic. With some EQing and perhaps a different driver (got some 500w Fane 12"s lying around), I can probably get some decent sounds out of it.
Another avenue to explore would be whether to go sealed or ported. A few holes drilled in the back (perhaps doubling up the material thickness) would put tuning in the 120Hz range, which would certainly gain some mechanical power handling, and also some ventilation.
Things to do. I'll try to make a prototype baffle soon.
Chris
Here we go...
So, after buying some small clamps, this build flew together. It ain't pretty, but it works for now. There's 2x NL4 inputs, so I can drive each series group of 3 drivers individually. I'm using a DCX2496 and an NU4-6000 for this, so I can add any crossovers, delays, EQ etc I want.
First of all, I ran all the drivers full-range. After messing with REW for a bit, I got some sensible graphs. Guess what, it looks like a 901 driver's raw response. Maybe not quite that bad, but not far off: a big hump around 1kHz, with 100Hz and 10kHz both 20dB down.
I'm going to attribute at least some of that to the line array. These drivers definitely were better than that in the Bose-designed cabinet.
Got REW to EQ the whole mess flat, and had a listen.
Where the mic was, it actually sounded quite nice. Good amount of headroom, flat, even response. Walked to the far end of the garden, and it was awful. A lot of treble. Yuck yuck yuck.
Next up, I put a low-pass filter (700Hz-ish) in on the DCX2496. This was a simple first-order filter, on the bottom 9 drivers. When I come to build the passive version, I don't want to have to mess with complex crossovers, so I kept it as simple as possible. Ran REW again (a mere 16dB between the top and bottom of the bump this time), and dialled everything into the DCX.
The result was actually really rather good. The sound stays pretty even when walking around. Perhaps a slight change in the last octave when you move over large distances, but nothing objectionable.
So, I went and got a 12" in a box, and sat back to enjoy the music for a while. Crossover LR4 at 200Hz.
That's all for now.
Chris
So, after buying some small clamps, this build flew together. It ain't pretty, but it works for now. There's 2x NL4 inputs, so I can drive each series group of 3 drivers individually. I'm using a DCX2496 and an NU4-6000 for this, so I can add any crossovers, delays, EQ etc I want.
First of all, I ran all the drivers full-range. After messing with REW for a bit, I got some sensible graphs. Guess what, it looks like a 901 driver's raw response. Maybe not quite that bad, but not far off: a big hump around 1kHz, with 100Hz and 10kHz both 20dB down.
I'm going to attribute at least some of that to the line array. These drivers definitely were better than that in the Bose-designed cabinet.
Got REW to EQ the whole mess flat, and had a listen.
Where the mic was, it actually sounded quite nice. Good amount of headroom, flat, even response. Walked to the far end of the garden, and it was awful. A lot of treble. Yuck yuck yuck.
Next up, I put a low-pass filter (700Hz-ish) in on the DCX2496. This was a simple first-order filter, on the bottom 9 drivers. When I come to build the passive version, I don't want to have to mess with complex crossovers, so I kept it as simple as possible. Ran REW again (a mere 16dB between the top and bottom of the bump this time), and dialled everything into the DCX.
The result was actually really rather good. The sound stays pretty even when walking around. Perhaps a slight change in the last octave when you move over large distances, but nothing objectionable.
So, I went and got a 12" in a box, and sat back to enjoy the music for a while. Crossover LR4 at 200Hz.
That's all for now.
Chris
Hi, strait-forward report, Chris! Fs is rather at 200 than at 80Hz, my experience tells me, and because a short 3/4 inch coil cannot handle 60W for a minute. Have thou examined the burnt driver? Maybe thou should disassemble a good one and see how the voice coil is built. I believe, that for the voice coil former aluminium is better than kapton, because heat radiation is not an issue, but heat conductance were useful. Aluminium is surely better than paper, because the latter becomes dark with heat and then behaves even worse thermically. Also important, if wires are fully glued to the former, or partly fixed with sticky tape. The latter is no good. If well made, i guess, that one driver can handle 25W short-term, as in a furioso song ending. Good luck!
Hi,
The voicecoil was a two-layer winding, both outside the kapton former. Since these drivers can do a useful amount of low end in the Bose-designed cabinet (which is a pretty standard ported box), I think their resonance will be somewhere near the usual for drivers this size. 250Hz is, I think, suitably far away from Fs.
I didn't quite believe the results either, but there they are.
Chris
The voicecoil was a two-layer winding, both outside the kapton former. Since these drivers can do a useful amount of low end in the Bose-designed cabinet (which is a pretty standard ported box), I think their resonance will be somewhere near the usual for drivers this size. 250Hz is, I think, suitably far away from Fs.
I didn't quite believe the results either, but there they are.
Chris
Bose uses the same quantity of exactly this driver in the MA12EX column, which plays acceptably low enough that in speech-range applications they can run them without a subwoofer or bass module. The predecessor, the MA12, needed one or more MB4 bass modules (quad 5.25" vented box) to provide midbass and bass range support.
One trick Bose uses to get more output and bass extension from small drivers (as told to me by a former Bose engineer) is to use a stiff suspension and a Q of about .7 (making the driver essentially comfortable in a free-air application where it is receiving no support from the enclosure) and then tune the cabinet below Fs. This leads to an underdamped sound that their customers tend to like, although it is not the last word in bass accuracy. I have played around with a couple of Bose bass speakers and found that they could take full rated power in most cases without reaching Xmax as long as they were high-passed below the tuning frequency of the box.
One trick Bose uses to get more output and bass extension from small drivers (as told to me by a former Bose engineer) is to use a stiff suspension and a Q of about .7 (making the driver essentially comfortable in a free-air application where it is receiving no support from the enclosure) and then tune the cabinet below Fs. This leads to an underdamped sound that their customers tend to like, although it is not the last word in bass accuracy. I have played around with a couple of Bose bass speakers and found that they could take full rated power in most cases without reaching Xmax as long as they were high-passed below the tuning frequency of the box.
With two and a half inch basket diameter? I really do not think, that the Bose ones have an fs that low, that at thy used sine resistance is 3.2 Ohms. Rather 6.4 Ohms, and furthermore still with phase shift between voltage and current, hence even less real power draw than a real 6.4 Ohms resistor.
Its a 70mm basket, but ~60mm cone.
Here's something the same size: Peerless by Tymphany 830984 2-1/2" Full Range Woofer
110Hz Fs, Qts = 0.7, and impedance is low and flat between 150Hz and 1kHz. These Bose drivers won't be exactly the same, but there's no way you'll convince me the resonance is up at 250Hz.
These drivers are designed specifically to be used with a small class D amplifier, which will work better with 4ohm drivers. Measuring 3.2ohm DCR sounds about right to me.
Taterworks, thanks for that lead! They're quoting 600w peak power for that column, which would be 50w per driver, pretty much what I observed.
As an update, I'm quite pleased with how the column sounds. Running only the top 3 drivers for HF has meant the whole thing is working pretty much as a point source all the way up, so there doesn't seem to be a problem with the frequency response varying with distance.
I have a 12" driver in a box around here, so will be conducting some high-power tests to make sure a 1x12" sub will be a reasonable match. I can go to 1x8" or 1x15" subs, both of which have amps etc built-in.
Chris
Here's something the same size: Peerless by Tymphany 830984 2-1/2" Full Range Woofer
110Hz Fs, Qts = 0.7, and impedance is low and flat between 150Hz and 1kHz. These Bose drivers won't be exactly the same, but there's no way you'll convince me the resonance is up at 250Hz.
These drivers are designed specifically to be used with a small class D amplifier, which will work better with 4ohm drivers. Measuring 3.2ohm DCR sounds about right to me.
Taterworks, thanks for that lead! They're quoting 600w peak power for that column, which would be 50w per driver, pretty much what I observed.
As an update, I'm quite pleased with how the column sounds. Running only the top 3 drivers for HF has meant the whole thing is working pretty much as a point source all the way up, so there doesn't seem to be a problem with the frequency response varying with distance.
I have a 12" driver in a box around here, so will be conducting some high-power tests to make sure a 1x12" sub will be a reasonable match. I can go to 1x8" or 1x15" subs, both of which have amps etc built-in.
Chris
Further update. Using what the stock active crossovers are likely to be in these subs (Butterworth 12dB/octave, 120-150Hz), this column will nudge 110dB (C-weighted) at 1m, though I gave up at that volume because I was hitting the limiter on the full-range channel of the NU4-6000 (around 200w peaks into the 3 drivers - not something I'd want to sustain). I suspect I can eek out some more by playing with the dynamic EQ section of the DEQ2496, but I'm pretty happy.
So, now I need to choose an active sub to match.
The column is power-hungry, and the bigger subs come with bigger amps to throw the power around.
However, making the whole thing small is a priority, too.
Its a choice between the 8" or 12" active subs here:
the box pro Achat 108 Sub A - Thomann UK
the box CL 112 Sub MK II - Thomann UK
8":
Pros:
- Smaller
- Lighter
- Cheaper
- No chance of burning the Bose drivers
Cons:
- SPL might be marginal**
- No socket to mount column
12":
Pros:
- Power, both for itself and the column
- Pole mount
Cons:
- Heavier
- More expensive.
** Lets do some maths.
800w peaks meant 110dB. Going to 120w peaks would give around 101dB, maybe a little more since the drivers were starting to get non-linear at the high power level. The 12" sub would give an extra 3dB in power, minus any compression (I'm ignoring their "peak power" rating).
I think I'll go for the 8" sub. There's a lot of playing around with dynamic EQs I can do - there's around 10dB of boost around 8kHz, so I think that can stand a little reduction when things are getting loud.
Chris
So, now I need to choose an active sub to match.
The column is power-hungry, and the bigger subs come with bigger amps to throw the power around.
However, making the whole thing small is a priority, too.
Its a choice between the 8" or 12" active subs here:
the box pro Achat 108 Sub A - Thomann UK
the box CL 112 Sub MK II - Thomann UK
8":
Pros:
- Smaller
- Lighter
- Cheaper
- No chance of burning the Bose drivers
Cons:
- SPL might be marginal**
- No socket to mount column
12":
Pros:
- Power, both for itself and the column
- Pole mount
Cons:
- Heavier
- More expensive.
** Lets do some maths.
800w peaks meant 110dB. Going to 120w peaks would give around 101dB, maybe a little more since the drivers were starting to get non-linear at the high power level. The 12" sub would give an extra 3dB in power, minus any compression (I'm ignoring their "peak power" rating).
I think I'll go for the 8" sub. There's a lot of playing around with dynamic EQs I can do - there's around 10dB of boost around 8kHz, so I think that can stand a little reduction when things are getting loud.
Chris
Well well, but again fs: The other driver example thou gave has a wide rubber surround, while the Bose ones have narrow impregnated paper. Why do thou not measure fs? This can save you much disappointment later. Plus, thou can calculate the crossover instead of just adjusting it.
According to my measurements, in this enclosure, bass rolls off around ~150Hz. Listening to the column matches this. Free-air resonance must be lower than 150Hz.
With the combination of Fs, Qts and Vas (each driver is in around 0.5L), I've got something that goes low enough, and, even in a 2nd round of high-power tests, stands up just fine.
I don't see why resonance is important here, unless its to verify my previous findings about the power handling. Even then, these drivers can stand more power than I'll be using them with.
FWIW, the surround material doesn't really matter. Its the combination of that with the rear suspension that gives a driver its resonance. Rubber can be pretty hard, too...
Chris
With the combination of Fs, Qts and Vas (each driver is in around 0.5L), I've got something that goes low enough, and, even in a 2nd round of high-power tests, stands up just fine.
I don't see why resonance is important here, unless its to verify my previous findings about the power handling. Even then, these drivers can stand more power than I'll be using them with.
FWIW, the surround material doesn't really matter. Its the combination of that with the rear suspension that gives a driver its resonance. Rubber can be pretty hard, too...
Chris
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