My aim is to have subwoofers which will work with different rooms, usually small ones (I rent, and move home reasonably often). Room modes are therefore unknown and going to vary; the best way that I know of to counter this is flexibility of subwoofer positioning. I don't need to cover a huge listening position, but reasonable evenness is still desirable so multiple subwoofers are preferred - I shall aim for three or four. For both reasons, and to help when moving home, small size is wanted; I'd like to be building something more exciting, or at least dual-opposed (push-push), but for now have settled on single drivers in simple sealed boxes as the practical answer.
My drivers are the 12" FAB12 4ohm version from BK electronics (much like the famous LAB12, designed for large horns but also at home both vented and sealed).
One reason for going with sealed is to eliminate ports/vents; again largely for size but also to avoid having to deal with possible port noises. One down-side of distributed subs are if they make spurious noises, that can become audibly locatable. I've also no need for a resonant alignment to increase SPL as my goals there are fairly modest.
These subs are for music, rather than home theater, so in order to keep size/weight/cost reasonable I'm not going to aim for THX reference levels or super low frequencies. I'd be happy with 85dB + 15dB peaks = 100dB max at the listening position, down to below 30hz. IMO that is quite loud in a small space; it is often accepted that target SPLs should be reduced in such situations (I've even seen as low as 76dB + peaks considered appropriate for control rooms), so 85dB + 15dB is fine for me. The listening distance is 3m so as a worst case (except for room modes) I'd only need to achieve 110dB at 1m within Xmax.
Here is a WinISD simulation of one FAB12 in a sealed box. In this case it has a Linkwitz Transform to Q=0.5, with high-pass to restrain LF excursion and an 80hz low pass (my intended crossover). It reaches Xmax at about 20hz, with about 106dB output and still only -3dB at 27hz.
A pair of these should at worst gain +3dB, realistically in room I would expect at least +4dB so there is my 110dB, even without the third or fourth subwoofer. This is why I don't feel that I need a resonant alignment for my situation. The multiple subs are for smoothing but do add a little SPL as well.
My drivers are the 12" FAB12 4ohm version from BK electronics (much like the famous LAB12, designed for large horns but also at home both vented and sealed).
One reason for going with sealed is to eliminate ports/vents; again largely for size but also to avoid having to deal with possible port noises. One down-side of distributed subs are if they make spurious noises, that can become audibly locatable. I've also no need for a resonant alignment to increase SPL as my goals there are fairly modest.
These subs are for music, rather than home theater, so in order to keep size/weight/cost reasonable I'm not going to aim for THX reference levels or super low frequencies. I'd be happy with 85dB + 15dB peaks = 100dB max at the listening position, down to below 30hz. IMO that is quite loud in a small space; it is often accepted that target SPLs should be reduced in such situations (I've even seen as low as 76dB + peaks considered appropriate for control rooms), so 85dB + 15dB is fine for me. The listening distance is 3m so as a worst case (except for room modes) I'd only need to achieve 110dB at 1m within Xmax.
Here is a WinISD simulation of one FAB12 in a sealed box. In this case it has a Linkwitz Transform to Q=0.5, with high-pass to restrain LF excursion and an 80hz low pass (my intended crossover). It reaches Xmax at about 20hz, with about 106dB output and still only -3dB at 27hz.
A pair of these should at worst gain +3dB, realistically in room I would expect at least +4dB so there is my 110dB, even without the third or fourth subwoofer. This is why I don't feel that I need a resonant alignment for my situation. The multiple subs are for smoothing but do add a little SPL as well.
In a multi sub arrangement it is common to begin with one in a corner, and this one usually needs more displacement than the others.
Hi Allen, yes there seem to be a few theories on how best to position them, but one corner and one wall are where I've had luck in the past too. The nice thing is that the corner gives extra SPL but I might indeed need more, still. If that is so, my plan is to double up the subs in that position; closely coupled (within 1/4 wavelength) should hopefully gain something approaching 6dB, which at low frequencies is quite significant. Perhaps there are better answers but for small subs and flexibility I'm hoping this will work.
Just to add a general bit about my sudden interest in room modes, since it is a large element of this project: I've known of them for quite a long time, and found it surprising how sub positioning can really change what is heard at the listening position. But only very recently did I begin to realise quite 'how' big the modes (especially the nulls/drops) can be. In this post Art introduced me to a chart by Josh Ricci which shows quite how dramatically they can affect SPL.
Much bigger than most other aspects that affect SPL calculation, including alleged room gain.
There are some other minor benefits to multiple subs, like them being a size and weight that I can actually move around. So doubling them up seems better than making bigger ones. In the past I have made huge things with a convenient room position in mind, which limits where they can be put and took no account of what would actually work acoustically. These days I find that kind of thing too restrictive; if I ever settle down then I'd be able to work out where subs needed to go acoustically and then build the biggest/best for each specific position.
Just to add a general bit about my sudden interest in room modes, since it is a large element of this project: I've known of them for quite a long time, and found it surprising how sub positioning can really change what is heard at the listening position. But only very recently did I begin to realise quite 'how' big the modes (especially the nulls/drops) can be. In this post Art introduced me to a chart by Josh Ricci which shows quite how dramatically they can affect SPL.
Much bigger than most other aspects that affect SPL calculation, including alleged room gain.
There are some other minor benefits to multiple subs, like them being a size and weight that I can actually move around. So doubling them up seems better than making bigger ones. In the past I have made huge things with a convenient room position in mind, which limits where they can be put and took no account of what would actually work acoustically. These days I find that kind of thing too restrictive; if I ever settle down then I'd be able to work out where subs needed to go acoustically and then build the biggest/best for each specific position.
With a sealed subwoofer there isn't much restriction on size, if one can use EQ (instead of acoustic ports/vents, which want to be certain sizes according to tuning and air velocity). The trade off for a sealed box is ever more power needed as the box gets smaller. Here is a WinISD simulation of the apparent amplifier power needed to reach the same Xmax and same SPL for the FAB12 in different box volumes:
Seven volumes from 30L to 60L in 5L increments, all transformed with a Linkwitz Transform to a Q=0.5. Of course, 5L is proportionally bigger as the box gets smaller, and the amount of extra power needed also increases faster.
In theory the driver is thermally rated up to 500W and so can take any of these options, especially as they're related to short peaks (there may not even be much power compression). However, at least where I live, amplifier power still costs reasonable money above a certain point, so there is going to be a sweet spot between what box size one can live with and the cost of powering it to full linear potential. There is the added thought that if these were ever used for movies then I probably wouldn't mind going beyond Xmax, which takes more power again (I don't mind about staying strictly within linear travel for an exploding planet).
There are a couple of class-D prosound amplifiers around (such as the XLS range by Crown) that seem much cheaper than many plate amplifiers, and are well enough regarded for subwoofers. I don't particularly need the subwoofer to be active, in fact an external amp would make the sub lighter and mean only having to run one cable to it; I also think a nice vented case is going to be a healthier place for an amp than a sealed vibrating stuffed box.
Staying under about 300W into 4ohms would still be useful for price and availability though. Or if I ran four subs, they could be configured as 2x 2ohms, so still needing just the one stereo amplifier if it were 2ohm capable. Though that may not be the best option; I would prefer individual control of each sub.
Seven volumes from 30L to 60L in 5L increments, all transformed with a Linkwitz Transform to a Q=0.5. Of course, 5L is proportionally bigger as the box gets smaller, and the amount of extra power needed also increases faster.
In theory the driver is thermally rated up to 500W and so can take any of these options, especially as they're related to short peaks (there may not even be much power compression). However, at least where I live, amplifier power still costs reasonable money above a certain point, so there is going to be a sweet spot between what box size one can live with and the cost of powering it to full linear potential. There is the added thought that if these were ever used for movies then I probably wouldn't mind going beyond Xmax, which takes more power again (I don't mind about staying strictly within linear travel for an exploding planet).
There are a couple of class-D prosound amplifiers around (such as the XLS range by Crown) that seem much cheaper than many plate amplifiers, and are well enough regarded for subwoofers. I don't particularly need the subwoofer to be active, in fact an external amp would make the sub lighter and mean only having to run one cable to it; I also think a nice vented case is going to be a healthier place for an amp than a sealed vibrating stuffed box.
Staying under about 300W into 4ohms would still be useful for price and availability though. Or if I ran four subs, they could be configured as 2x 2ohms, so still needing just the one stereo amplifier if it were 2ohm capable. Though that may not be the best option; I would prefer individual control of each sub.
Thanks, GM. I remember reading (perhaps from Earl Geddes) about raising at least one sub higher than the others. That is probably doable even in a small room, if they're small-ish and not too heavy. Perhaps a reasonable compromise; to have every sub at its ideal position vertically as well as horizontally could become quite awkward.
Hi Kev,
There is no reason to use a high pass on 4 of those drivers in sealed boxes, if you are aiming for domestic levels of sound.
I had 4 LAB12's in sealed boxes at my last house, no neighbours. Never managed to over drive them.
Rob.
There is no reason to use a high pass on 4 of those drivers in sealed boxes, if you are aiming for domestic levels of sound.
I had 4 LAB12's in sealed boxes at my last house, no neighbours. Never managed to over drive them.
Rob.
My power calculations lead me to think that 40L is a reasonable compromise; not too big or too power-hungry. Allowing for the volume displaced by the driver and internal bracing would need it to be a bit bigger though. I do want these well braced, panel resonances could give their location away, so add several litres at least. It doesn't matter if they're a tiny bit bigger than needed, that would just mean a slightly easier life for the amp: the desired frequency response will be dependent on EQ rather than the natural acoustics of the box roll-off.
Cubes are efficient for surface area (panel size) and their internal symmetry doesn't really pose a problem at subwoofer frequencies. But I'd prefer a shallower design to help limit intrusion into the room when placed by walls etc. So More of a slightly taller rectangle would be best; I'll just have to constrain the slightly larger panels with more bracing, to stop their resonance lowering towards the frequencies of interest.
I think something like this would be good; not excessively tall and thin (in fact still okay to be disguised as a side table) but usefully shallower:
Cubes are efficient for surface area (panel size) and their internal symmetry doesn't really pose a problem at subwoofer frequencies. But I'd prefer a shallower design to help limit intrusion into the room when placed by walls etc. So More of a slightly taller rectangle would be best; I'll just have to constrain the slightly larger panels with more bracing, to stop their resonance lowering towards the frequencies of interest.
I think something like this would be good; not excessively tall and thin (in fact still okay to be disguised as a side table) but usefully shallower:
You're welcome! Yes, a local forum member uses multiple 12" Rhythmics? for his DIY Synergy horn system.
Thanks Rob, that is very useful to hear!
As it happens, I did a simulation in Hornresponse too, and that showed the excursion staying under control all the way down, whereas WinISD shows it continuing to climb. Hornresp is more sophisticated but I'm a beginner with it, so wasn't sure which to believe. I think you've put my mind at rest 🙂
I suppose I might sometimes want to add a rumble filter or similar to reduce annoying neighbors, or vibrating things in the room. But it could easily be made optional; for quality listening I don't really like sharp knees in the response from brick wall filters, but lower order filters affect the frequencies of interest more. There is also their affect on group delay, in some cases.
I've decided to go with 18mm multi-layer plywood for the cabinet. For the prototype at least it won't be Baltic Birch (£££), whether I step up to that for the final ones depends on how I get on with the (much) cheaper standard stuff. I've purchased some and there are no loose bits rattling inside, so it'll at least be good enough for the prototype, if well braced and any voids at the edges sealed.
Though not premium, it is still lighter and stiffer than MDF, so should be adequate. But a full 8'x4' sheet is still pretty heavy, even without drivers. Thankfully my 40L (or so) box needs only about half a sheet; driver and box combined should weigh roughly 20kg/45lb which I can carry up/down stairs without too much danger. This is one reason I've forgone dual-opposed drivers in bigger boxes, and compromised on smaller single boxes (that can still be placed close enough to acoustically couple if needed).
I can't get a full sheet in the car, or up the stairs. I could buy pre-cut 6'x2' sheets that will fit, but they each cost almost as much as a full sheet. So I bought a full sheet and had it cut down. For not much more than one smaller sheet I have enough for two boxes and 2x 2'-square offcuts which might work for bracing. This is how it (I hope) works out:
And that is where the project has come to a halt, since it is raining outside (yet again) and I can't sensibly use power tools like routers and circular saws in the flat. Hoping to visit relatives at the weekend, and see if I might borrow their garage.
EDIT: Originally I wasn't going to make a prototype; there isn't really much to go wrong with a simple sealed box, especially when already intending EQ, and I'm not new to speaker building. However, there is some question about whether the subwoofer might sonically reveal its location. I can probably stop the box doing that but I've no serious experience with these drivers; some drivers make audible noises at high excursion whilst others don't. I'm optimistic because they're good quality but if proved wrong then the project may have to revert to a bandpass design. One thing about having subs distributed, rather than near the main speakers, is they really need to avoid broadcasting their location.
Though not premium, it is still lighter and stiffer than MDF, so should be adequate. But a full 8'x4' sheet is still pretty heavy, even without drivers. Thankfully my 40L (or so) box needs only about half a sheet; driver and box combined should weigh roughly 20kg/45lb which I can carry up/down stairs without too much danger. This is one reason I've forgone dual-opposed drivers in bigger boxes, and compromised on smaller single boxes (that can still be placed close enough to acoustically couple if needed).
I can't get a full sheet in the car, or up the stairs. I could buy pre-cut 6'x2' sheets that will fit, but they each cost almost as much as a full sheet. So I bought a full sheet and had it cut down. For not much more than one smaller sheet I have enough for two boxes and 2x 2'-square offcuts which might work for bracing. This is how it (I hope) works out:
And that is where the project has come to a halt, since it is raining outside (yet again) and I can't sensibly use power tools like routers and circular saws in the flat. Hoping to visit relatives at the weekend, and see if I might borrow their garage.
EDIT: Originally I wasn't going to make a prototype; there isn't really much to go wrong with a simple sealed box, especially when already intending EQ, and I'm not new to speaker building. However, there is some question about whether the subwoofer might sonically reveal its location. I can probably stop the box doing that but I've no serious experience with these drivers; some drivers make audible noises at high excursion whilst others don't. I'm optimistic because they're good quality but if proved wrong then the project may have to revert to a bandpass design. One thing about having subs distributed, rather than near the main speakers, is they really need to avoid broadcasting their location.
Last edited:
Yes. It’s a matter of engaging the vertical dimension to address modes. Naturally in this statement Earl has condensed this into the minimum action that will fulfill this.
If you keep this in mind you can devise your own measurement scheme (physical sweep pattern) to show you which modes that sub is engaging.
Thank you again, Allen. I do like how Earl tests to evaluate the practicalities; their real-world impact and how far it is worth taking things. With so many competing requirements and compromises, it is sometimes easy to get obsessed with specific aspects, beyond the point of diminishing returns.
Yes, I shall have to work on room measurements and positioning. It is a while since I read about this, and I want to do a better job of it than I've attempted before, so revision will be the first step. Last time, I just played a sub at the listening position and measured levels at a few potential room locations, to find which weren't in SPL holes, which was easy but seems rather backwards. This time I'd probably want to map their individual and combined effect around the listening position and maybe across the wider room - especially if there are any unwelcome resonances of the room or its contents.
Yes, I shall have to work on room measurements and positioning. It is a while since I read about this, and I want to do a better job of it than I've attempted before, so revision will be the first step. Last time, I just played a sub at the listening position and measured levels at a few potential room locations, to find which weren't in SPL holes, which was easy but seems rather backwards. This time I'd probably want to map their individual and combined effect around the listening position and maybe across the wider room - especially if there are any unwelcome resonances of the room or its contents.
Just looking again at the high-pass filter. It was partly needed in WinISD's sim as a consequence of using the Linkwitz Transform, but not entirely; excursion still climbs at low frequency even without the transform:
whilst hornresp is less pessimistic:
Though just to mention: I'm not set on using a Linkwitz Transform, it was just convenient for equalising and so comparing different box volumes in the sims. It might be or not be the best choice. For example here is a non-transformed example (same 40L box) - even WinISD only thinks a low and unobtrusive HP/rumble filter is needed:
It has very little effect on the response curve at frequencies of interest, so the need for it or not doesn't really matter:
I've shown the Linkwitz-Transformed (to Q=0.5) version in green for comparison with the non-transformed version (Q=0.79) in orange. They're equivalent at 20hz (excursion limited) but even though the transform should give a shallower roll-off... the high pass filters needed to then tame the extra very low frequency excursion are more aggressive, so overall it falls off more steeply. Probably different LT or HP parameters could/should be chosen, but as I'm using PC-based DSP it might just be simpler to leave the natural roll-off and attenuate the higher frequencies to flatness. Certainly the excursion and FR curves look nicer.
Though this is more as a reminder, for much later in the project, and can be played with endlessly. For now the key thing is that I know the limit is simply Xmax as we head below 30hz, not things that can be easily adjusted in the design like (e.g.) cabinet volume or power available.
whilst hornresp is less pessimistic:
Though just to mention: I'm not set on using a Linkwitz Transform, it was just convenient for equalising and so comparing different box volumes in the sims. It might be or not be the best choice. For example here is a non-transformed example (same 40L box) - even WinISD only thinks a low and unobtrusive HP/rumble filter is needed:
It has very little effect on the response curve at frequencies of interest, so the need for it or not doesn't really matter:
I've shown the Linkwitz-Transformed (to Q=0.5) version in green for comparison with the non-transformed version (Q=0.79) in orange. They're equivalent at 20hz (excursion limited) but even though the transform should give a shallower roll-off... the high pass filters needed to then tame the extra very low frequency excursion are more aggressive, so overall it falls off more steeply. Probably different LT or HP parameters could/should be chosen, but as I'm using PC-based DSP it might just be simpler to leave the natural roll-off and attenuate the higher frequencies to flatness. Certainly the excursion and FR curves look nicer.
Though this is more as a reminder, for much later in the project, and can be played with endlessly. For now the key thing is that I know the limit is simply Xmax as we head below 30hz, not things that can be easily adjusted in the design like (e.g.) cabinet volume or power available.
Last edited:
As I've got enough sheet for two boxes, it is tempting to cut all the parts for two whilst I have the tools out etc. But that partly defeats the aim of a first prototype, so best to save the sheet for a second version if needed. I've also noticed that the FAB12 is physically a bit different to the LAB12, so my experiences with the latter may or may not count in all aspects.
It has been years since I had a LAB12, from the front I'm sure it has a slightly bigger dust cap (for the same nominal cone size). But, more noticeably, the vent on the back of the FAB12 looks much bigger than I remember the Eminence LAB12 having.
The FAB12 has basically a 2" ID tube straight through to the dust cap (and so presumably a bigger voicecoil). Pretty big vent for just a 12" driver, the picture doesn't entirely convey how big it seems in practice, and not what I recall the LAB12 being like, although there was a grill on it. (edit: the magnet diameters are about the same, the LAB12 suggests several mm bigger but it is covered in a rubber casing). The vent looks very promising for cooling and power handling, whether needed or not, though I don't know what other differences such changes might add up to.
It has been years since I had a LAB12, from the front I'm sure it has a slightly bigger dust cap (for the same nominal cone size). But, more noticeably, the vent on the back of the FAB12 looks much bigger than I remember the Eminence LAB12 having.
The FAB12 has basically a 2" ID tube straight through to the dust cap (and so presumably a bigger voicecoil). Pretty big vent for just a 12" driver, the picture doesn't entirely convey how big it seems in practice, and not what I recall the LAB12 being like, although there was a grill on it. (edit: the magnet diameters are about the same, the LAB12 suggests several mm bigger but it is covered in a rubber casing). The vent looks very promising for cooling and power handling, whether needed or not, though I don't know what other differences such changes might add up to.
Last edited:
Well as you say 'might' then chuffing may of been a thing on the early model. It's not a port width or flare shape you would choose. An enlarged dustcap could mean even more air having to pass. Though I look at the two, and just wonder how much magnet I might of lost. Though they are very nice looking drivers. And there is more than one type of magnet.
That is a good point, chuffing from vented boxes was something I wanted to avoid so to then have it arise from the driver vent would have been annoying (at least it is far too short for in-band port resonances though). So a smaller area of dustcap pushing through a bigger vent doesn't seem bad, though perhaps there was a cooling aspect to the design as well. Either way, this kind of thing is why I'm to be prototyping and testing even a simple sealed box, before making all four.
You may be right about the bigger bore making the magnet slightly less effective though. Eminence say the LAB12 has a BL of 15TM whilst tha FAB12 is 13.2TM. I'm also guessing that Fabbest may have compensated for a reduced 'B' with more of an 'L', in that BL product, since they have a 16mm Xmax instead of the LAB12s 13mm. Though people can derive Xmax in different ways, so that might mean not very much in reality. It is a welcome possibility though; even 16mm isn't huge (by subwoofer standards), but if it follows in the LAB12's footsteps it should be quite low distortion compared to many other modestly priced sub drivers.
Surprisingly the FAB12 claims a usable range up to 800hz, though I suspect that might not be an equal comparison; the quite similar LAB12 was specified to just 100hz (though up to 200hz was still okay for it). Either way, my intention is firmly as subwoofers here so upper ranges won't matter. I don't want to stray up into audibly localizable frequencies, when the subs aren't necessarily placed close to the main speakers.
You may be right about the bigger bore making the magnet slightly less effective though. Eminence say the LAB12 has a BL of 15TM whilst tha FAB12 is 13.2TM. I'm also guessing that Fabbest may have compensated for a reduced 'B' with more of an 'L', in that BL product, since they have a 16mm Xmax instead of the LAB12s 13mm. Though people can derive Xmax in different ways, so that might mean not very much in reality. It is a welcome possibility though; even 16mm isn't huge (by subwoofer standards), but if it follows in the LAB12's footsteps it should be quite low distortion compared to many other modestly priced sub drivers.
Surprisingly the FAB12 claims a usable range up to 800hz, though I suspect that might not be an equal comparison; the quite similar LAB12 was specified to just 100hz (though up to 200hz was still okay for it). Either way, my intention is firmly as subwoofers here so upper ranges won't matter. I don't want to stray up into audibly localizable frequencies, when the subs aren't necessarily placed close to the main speakers.
Last edited:
The FAB12 also has a lower Re, so the motor constant is actually higher than on the LAB12. Seems like a nice driver if the nonlinearities are kept in check
There are a couple of versions of these drivers, a 6ohm version has an Re of 4.29 and the 4ohm version is 3.1; similar values for the FAB12 and LAB12 in both cases. IIRC the 6ohm version was made to offset the 'in-horn' change in impedance for the original LABhorn design. That said, I can't find the 6ohm version of the FAB12 on BK Electronic's website any more (just their ebay store), so I don't know if it is less popular than the 4ohm.
I suppose lots of people would prefer 4ohms. Technically speaking, higher impedance is probably slightly better for sound quality (IMO), but with lower impedance you get much more power out of a given amplifier - since they're almost always rated for both 4ohms and 8ohms these days. Some amps (like those I'm considering) will do 2ohms, which would offer highest amp power into 2x 4ohms in parallel (thinking dual-opposed/push-push, if I ever get the space).
But yes, I agree the FAB12 still seems like a nice driver, a very nice driver. The similarities with the LAB12 are striking, and that has pretty good distortion figures (for a subwoofer); I hope these positive attributes carry over to join the slightly up-rated specifications. I suspect they will; BK Electronics know their stuff, IMO.
I suppose lots of people would prefer 4ohms. Technically speaking, higher impedance is probably slightly better for sound quality (IMO), but with lower impedance you get much more power out of a given amplifier - since they're almost always rated for both 4ohms and 8ohms these days. Some amps (like those I'm considering) will do 2ohms, which would offer highest amp power into 2x 4ohms in parallel (thinking dual-opposed/push-push, if I ever get the space).
But yes, I agree the FAB12 still seems like a nice driver, a very nice driver. The similarities with the LAB12 are striking, and that has pretty good distortion figures (for a subwoofer); I hope these positive attributes carry over to join the slightly up-rated specifications. I suspect they will; BK Electronics know their stuff, IMO.
Last edited:
Well I knocked together a closed box. At modest SPLs I can't localise the subwoofer from 80hz downwards, only with frequencies above 100hz does it start to sound slightly separate from the main speakers. Which means the driver isn't making any spurious higher frequency output, at detectable levels anyway. So good news as far as it goes. However, the cone is barely moving at this level, so it isn't yet a full test.
Here I have a problem, I'm designing these for future eventualities but my current situation is a small flat surrounded by neighbors on all sides (and below). I've already had annoyed comments, though not actually formal complaints; the SPL of these at Xmax is going to be 'way' too loud to test here. I don't have a mobile amplifier capable of doing it in some distant outdoor place either. So not yet sure how (or if) I'm going to be able to run proper full tests. In the meantime I might just try very low frequencies that can't really be heard, or that the neighbors can't localise to my flat. I need to break in the driver's suspension so that would be helpful there, too.
Though first I will need to get a bigger amplifier; my old behringer A500 hasn't got enough to push these to Xmax in 40L (which I already knew). But it is possible that I might also need to increase the signal level between my DAC (a Topping DM7) and the amp, as well, to get full output. I shall have to look at the specifications, to see if the DAC can power pro amps to full input levels.
Here I have a problem, I'm designing these for future eventualities but my current situation is a small flat surrounded by neighbors on all sides (and below). I've already had annoyed comments, though not actually formal complaints; the SPL of these at Xmax is going to be 'way' too loud to test here. I don't have a mobile amplifier capable of doing it in some distant outdoor place either. So not yet sure how (or if) I'm going to be able to run proper full tests. In the meantime I might just try very low frequencies that can't really be heard, or that the neighbors can't localise to my flat. I need to break in the driver's suspension so that would be helpful there, too.
Though first I will need to get a bigger amplifier; my old behringer A500 hasn't got enough to push these to Xmax in 40L (which I already knew). But it is possible that I might also need to increase the signal level between my DAC (a Topping DM7) and the amp, as well, to get full output. I shall have to look at the specifications, to see if the DAC can power pro amps to full input levels.