If you are tests at some distant outdoor place, you probably have a 12v source from your car.
A 1000W modified sine wave power inverter cost around £125.00, a 500W inverter £45.95.
With a class D amp you'd be able to drive the speaker to ~500 watts with a 500W inverter.
You'd need to use some heavy duty jump leads directly to the battery for full tilt testing.
That said, you have already measured your neighbors response to the sub 😢
I have a setup similar to your plans and I really like it. Four sealed passive subs but with Dayton Reference series drivers. Two 12" that sit next to the front speakers and two 10" that are elevated on 16" stands on the sides of the listening area.
They blend seamlessly with the entire soundstage with no hint of their location. The stands evened out the vertical bass dispersion so there is no discernable difference for sitting or standing listeners.
Also, with multiple subs you have the opportunity to drive them in stereo. Mine were initially mono, but I was truly impressed after trying them in stereo. Never going back. Active XO at 120Hz / 12db/octave.
Much success.
Thank you, Art. Yes it might come to buying an inverter. I didn't really want to spend the money just for a brief testing period, but actually it would be useful for future testing, too. So more of an investment perhaps, and if course there are other reasons for testing outside of rooms. I'll be building some new main speakers after this, most probably multiple entry horns that will take a lot of iterative testing and tweaking. Some of that could be done quietly and nearfield but not all.
The neighbours are quite a disappointment in this respect. To be fair, there have been serious noise issues in the recent past; not from me, but it has made them sensitive to such things. I still hope that I'll be able to listen at adequate levels without much aggro, but initial testing indoors at xmax wouldn't improve the chances.. 🙁
That sounds like a nice setup! In the past I had a multiple arrangement, not done massively well but enough to convince me. So now I too would like to get a better one.
I've been without any subs for some time. In some ways that isn't a problem, and seems ludicrous to invest so much money and use up so much space for a bottom octave or two that one can often not notice. But gosh, even with just the one test box I'm revelling in the overall fuller sound; I've missed it. Though it is even more important for the future; my next main speakers will have their bass drivers acoustically band-passed so won't go very low by themselves.
That said I'm also being reminded of some dissatisfaction. A lot of music must be recorded for smaller systems as it has the bass unnaturally emphasised to some degree or other. Then if listening online or on radio, the broadcaster/streamer might add their own boost as well. Between that and the excessive compression some use, a lot of stuff isn't satisfying for quality listening on a quality system.
So I'll probably want some different EQ curves to switch in or out according to the source. But it seems likely that I'll even end up altering my music tastes in favour of genres and albums etc. that are well recorded and produced, and services/sources that don't purposely flavour the sound quality much.
Yes, there's a lot of level / tonal variations in recordings from any source.
My preamp has simple +/- 10dB tone controls which I find are enough to compensate, as I don't have any "EQ pre-sets" available.
I've not progressed very much with this, due to extra work commitments. But I've had more time to live with the test box/sub and am increasingly pleased with the way this is going. However whilst it isn't huge, at only about 45L (1.6cubic-feet) internal volume, I'm beginning to realise that three or four of these would take up quite a lot of my limited space. So I've been searching for a more powerful amp that would allow a smaller box. As I'm having to work overtime, might as well spend the money on something I want 🙂
So, I now have a used/second-hand Crown XLS2502 on the way, which of course is a risk; I'm hoping it will be in good condition. Crown specify 775W into 4ohms, which should be pretty comfortable as the amp is rated at rather more power into 2ohms; I'm not expecting the fan to come on in normal home use. According to these ASR tests the manufacturer's rating is perhaps not too optimistic; with the peak being even a bit higher. But it looks like I can expect roughly 2x 650w at 1%THD or nearly 2x 500watts at high quality. High enough for me, for a subwoofer, anyway.
That kind of power would allow Xmax to be reached in a sealed box of not much more than 25litres (0.9 cubic-feet) internal. In practice maybe 30L (internal) after driver displacement and bracing, if somewhat offset by stuffing. The FAB12 has a nominal rating of 500W so a fair pairing for the amp, but in practice I don't expect home/music listening to even approach the thermal limits. Obviously, in my current small flat (apartment) at the SPLs I can get away with, neither amp nor driver will be even slightly troubled; but I'm designing/buying with some optimism for the future.
So, I now have a used/second-hand Crown XLS2502 on the way, which of course is a risk; I'm hoping it will be in good condition. Crown specify 775W into 4ohms, which should be pretty comfortable as the amp is rated at rather more power into 2ohms; I'm not expecting the fan to come on in normal home use. According to these ASR tests the manufacturer's rating is perhaps not too optimistic; with the peak being even a bit higher. But it looks like I can expect roughly 2x 650w at 1%THD or nearly 2x 500watts at high quality. High enough for me, for a subwoofer, anyway.
That kind of power would allow Xmax to be reached in a sealed box of not much more than 25litres (0.9 cubic-feet) internal. In practice maybe 30L (internal) after driver displacement and bracing, if somewhat offset by stuffing. The FAB12 has a nominal rating of 500W so a fair pairing for the amp, but in practice I don't expect home/music listening to even approach the thermal limits. Obviously, in my current small flat (apartment) at the SPLs I can get away with, neither amp nor driver will be even slightly troubled; but I'm designing/buying with some optimism for the future.
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This project continues to be slow, as are most of my attempts to have a hobby. But I have been able to do a lot more testing with the test boxes, which has proven very useful. I almost didn't bother with prototypes, as there didn't seem much to go wrong with a simple sealed box. But as a result of playing around with them, I will now build something a bit different to what was envisaged.
A key issue is that my room (as most rooms that I tend to rent) is quite modest in size, certainly compared to what a lot of members in (say) the US or AUS may expect. So, after positioning a TV + left & right speakers either side of it, there is no additional room width for a corner sub along the same wall (a preferred positioning for my first subwoofer). It must therefore be placed beneath (or above) a main speaker. Which is fine, though in practical terms that means (for me) putting it in the TV unit/cupboard that the speakers & TV sit on (putting it in front is too obtrusive in limited floor space). So, vibration has become a more important consideration - especially as this location typically wants to be the loudest of the subwoofers.
That can be somewhat mitigated with vibration isolation and weighted plinths/stands etc. But by preference I'm now more seriously looking at dual-opposed (push-pull) designs. Possibly slot-loaded, as that could conveniently direct the sound of opposed drivers through only one face (such as frontwards or downwards). Keeping two opposing faces clear of obstructions would be more tricky in small spaces. To steal an image as an illustration (from here):
After some testing, I think minimising physical vibration is probably also going to be worthwhile for the other subs too, since my rooms are frequently flats (appartments) on suspended floors with neighbours on all sides + above and below. The increase in size (from dual drivers) is undesirable, however I now have some amps that offer almost 800w peak per driver, to use for DSP'ing smaller boxes. The drivers are only rated at 500W but that is (supposedly) an RMS rating; peaks above that should be no issue in a home setting, and I'm not chasing enormous SPLs.
Anyway, I have four drivers in total; so the new plan is to build two dual-oposed subwoofers now, and add one or more others later when funds allow. I seem able to serve my listening position (wrt the room modes around there) adequately with just two subs in the current room, so no pressing need to be impatient, really. Which is just as well, given the snail's-pace of this project!
A key issue is that my room (as most rooms that I tend to rent) is quite modest in size, certainly compared to what a lot of members in (say) the US or AUS may expect. So, after positioning a TV + left & right speakers either side of it, there is no additional room width for a corner sub along the same wall (a preferred positioning for my first subwoofer). It must therefore be placed beneath (or above) a main speaker. Which is fine, though in practical terms that means (for me) putting it in the TV unit/cupboard that the speakers & TV sit on (putting it in front is too obtrusive in limited floor space). So, vibration has become a more important consideration - especially as this location typically wants to be the loudest of the subwoofers.
That can be somewhat mitigated with vibration isolation and weighted plinths/stands etc. But by preference I'm now more seriously looking at dual-opposed (push-pull) designs. Possibly slot-loaded, as that could conveniently direct the sound of opposed drivers through only one face (such as frontwards or downwards). Keeping two opposing faces clear of obstructions would be more tricky in small spaces. To steal an image as an illustration (from here):
After some testing, I think minimising physical vibration is probably also going to be worthwhile for the other subs too, since my rooms are frequently flats (appartments) on suspended floors with neighbours on all sides + above and below. The increase in size (from dual drivers) is undesirable, however I now have some amps that offer almost 800w peak per driver, to use for DSP'ing smaller boxes. The drivers are only rated at 500W but that is (supposedly) an RMS rating; peaks above that should be no issue in a home setting, and I'm not chasing enormous SPLs.
Anyway, I have four drivers in total; so the new plan is to build two dual-oposed subwoofers now, and add one or more others later when funds allow. I seem able to serve my listening position (wrt the room modes around there) adequately with just two subs in the current room, so no pressing need to be impatient, really. Which is just as well, given the snail's-pace of this project!
Since you are still investigating the concept, might I suggest another one that could potentially be better than distributed subs: one nearfield sub. Distributed subs will not help all that much if your listening seat happens to coincide with a room node or null. It is difficult to overcome that when the source of LF is elsewhere in the room. In contrast, the nearfield source's SPL will overwhelm the room response. The only criteria is that the sub should be VERY close to your head, like 30cm away or less. One potential way to make this happen is with a 4th order bandpass sub that uses a poted front cavity. The port tube can be external to the box and terminate immediately behind your chest or head. If you choose to use a sealed box, the driver must be located close to your head and this is not as simple as bringing a port tube up to that location.
Since you will be in the nearfield and the room response will be largely suppressed, the response will be the same no matter what room (or what apartment) you are living in. Also the SPL can be lower and your neighbors will not be bothered as much as when you use many subs around the room.
IMO distributed subs are really only useful when the LF soundfield must be even across a wide area, e.g. for home theater with multiple seats, etc.
Since you will be in the nearfield and the room response will be largely suppressed, the response will be the same no matter what room (or what apartment) you are living in. Also the SPL can be lower and your neighbors will not be bothered as much as when you use many subs around the room.
IMO distributed subs are really only useful when the LF soundfield must be even across a wide area, e.g. for home theater with multiple seats, etc.
That is a very interesting suggestion, Charlie; thank you!
As it happens, my original plans (for dealing with small and varied rooms with thin walls) had been about very nearfield (main) speakers. These plans later diverged into wanting two setups; a 'very' nearfield one for decent SPL at the listening position without annoying other residents, plus a second whole-room setup for more general use and future aspirations towards having more space.
But in reality, I'm unlikely to get the luxury of large rooms any time soon, nor probably ever (given how the cost of living vs future pensions are going). So the kind of thing you're suggesting could well be a very nice and appropriate approach. I hadn't really thought of it for subs, just mains, but now that you mention it...
I suppose all I'd really want WRT distance/modes/reflections is just enough room ineraction to avoid sounding much like headphones or an anechoic chamber, and no more because that (or greater SPL from more distant sources) is only going to annoy other residents.
So yes, a very interesting idea,
Thanks again!
As it happens, my original plans (for dealing with small and varied rooms with thin walls) had been about very nearfield (main) speakers. These plans later diverged into wanting two setups; a 'very' nearfield one for decent SPL at the listening position without annoying other residents, plus a second whole-room setup for more general use and future aspirations towards having more space.
But in reality, I'm unlikely to get the luxury of large rooms any time soon, nor probably ever (given how the cost of living vs future pensions are going). So the kind of thing you're suggesting could well be a very nice and appropriate approach. I hadn't really thought of it for subs, just mains, but now that you mention it...
I suppose all I'd really want WRT distance/modes/reflections is just enough room ineraction to avoid sounding much like headphones or an anechoic chamber, and no more because that (or greater SPL from more distant sources) is only going to annoy other residents.
So yes, a very interesting idea,
Thanks again!
Thinking more about this, my choice of 12" drivers are probably a bit larger than ideal for a 'very' nearfield subwoofer. However, I think it may be possible to make something from them that isn't too obtrusive in this role, but which would also work as room-placed subs - which might be nice for future situations.
The bandpass option could be very neat - an external port could mean only a smaller tube extending up to near the head/ears. A little bit like the garden subs in concept (rather than execution):
except maybe disguised as a side-table and lamp, or just poking unobtrusively up above the back of the listening chair.
Though I considered bandpass before this thread and wasn't keen on how the extra chamber (and port) adds noticably to the total cabinet volume and complexity - given that in this case space is limited and I don't actually need the extra SPL that BP can offer (vs small sealed & EQ'd boxes).
It also occurs to me that a small sealed but slot-loaded configuration could offer 'some' similar benefits, at least in presenting a smaller opening. Like a sealed version of a SLOB
It seems (from hornresp) that one can even extend/lengthen the slot beyond the cabinet into something that looks similar to a port, although the unwanted peak from the slot then becomes lower, i.e. nearer to the intended frequency range, so there are limits. It is also relatively convenient to have dual opposed drivers by putting one each side of the slot - probably not necessary for a very nearfield (low spl) situation, but useful if this were to be a dual purpose box.
Or I could simply have one or more shallow sealed subs just behind the chair at head level. Perhaps disguised in a sort of deep picture frame covered with acoustic cloth. Like an 'on-wall' version of an in-wall design
Not ideal for depth as they'd still be maybe 8" or 10" thick, but simple, small and uncomplicated. This is made more possible because (in small rooms) the listening chair is typically against a wall - in itself not ideal acoustically, though maybe the sub could be within an 8"-10" deep sound-absorbing mat to help with wall reflections from main speakers.
So a few ideas to (yet again) change where I go with this, not yet decided which it'll be.
The bandpass option could be very neat - an external port could mean only a smaller tube extending up to near the head/ears. A little bit like the garden subs in concept (rather than execution):
except maybe disguised as a side-table and lamp, or just poking unobtrusively up above the back of the listening chair.
Though I considered bandpass before this thread and wasn't keen on how the extra chamber (and port) adds noticably to the total cabinet volume and complexity - given that in this case space is limited and I don't actually need the extra SPL that BP can offer (vs small sealed & EQ'd boxes).
It also occurs to me that a small sealed but slot-loaded configuration could offer 'some' similar benefits, at least in presenting a smaller opening. Like a sealed version of a SLOB
It seems (from hornresp) that one can even extend/lengthen the slot beyond the cabinet into something that looks similar to a port, although the unwanted peak from the slot then becomes lower, i.e. nearer to the intended frequency range, so there are limits. It is also relatively convenient to have dual opposed drivers by putting one each side of the slot - probably not necessary for a very nearfield (low spl) situation, but useful if this were to be a dual purpose box.
Or I could simply have one or more shallow sealed subs just behind the chair at head level. Perhaps disguised in a sort of deep picture frame covered with acoustic cloth. Like an 'on-wall' version of an in-wall design
Not ideal for depth as they'd still be maybe 8" or 10" thick, but simple, small and uncomplicated. This is made more possible because (in small rooms) the listening chair is typically against a wall - in itself not ideal acoustically, though maybe the sub could be within an 8"-10" deep sound-absorbing mat to help with wall reflections from main speakers.
So a few ideas to (yet again) change where I go with this, not yet decided which it'll be.
I should add that I also did some tests with sub(s) close to my head/ears and Charlie was (of course) quite right about this arrangement, which is why I'm persuing it.
I've found posts which say that nearfield subs don't excite room modes, which is technically not true and and so provokes argument. It is more true to say that if my ears are very close to the source, it (the direct sound) dominates the room modes such that they become much less important. Close seems to mean exactly that, sort of how a very nearfield mic might be positioned. I had initially jumbled this up in my head with the quarter wavelength thing, but that (and also the omnidirectional nature of long wavelengths) are separate/different issues which in this case don't seem to replace the effect of being very close.
Similarly, although the subs excite the room modes as normal, the lower SPL needed for listening at such close quarters mean the modes are excited to a lesser degree. That said, being placed close to the ears/head at the listening chair may or may not be the optimum room location WRT what the subs excite elsewhere, but (especially as I don't sit in a corner) I think I'd have to be unlucky if there wasn't an overall reduction in what people next door get to hear.
I've found posts which say that nearfield subs don't excite room modes, which is technically not true and and so provokes argument. It is more true to say that if my ears are very close to the source, it (the direct sound) dominates the room modes such that they become much less important. Close seems to mean exactly that, sort of how a very nearfield mic might be positioned. I had initially jumbled this up in my head with the quarter wavelength thing, but that (and also the omnidirectional nature of long wavelengths) are separate/different issues which in this case don't seem to replace the effect of being very close.
Similarly, although the subs excite the room modes as normal, the lower SPL needed for listening at such close quarters mean the modes are excited to a lesser degree. That said, being placed close to the ears/head at the listening chair may or may not be the optimum room location WRT what the subs excite elsewhere, but (especially as I don't sit in a corner) I think I'd have to be unlucky if there wasn't an overall reduction in what people next door get to hear.
GM, happy times. In the past I owned my own detached house and tried some IBs, myself too. In fact I vaguely remember that forum from the time, though can't recall if I ever joined. But unfortunate changes meant leaving the house behind, which is sad because the IBs had worked so well that I'd planned to take the (suspended) floor up and build some below there. How circumstances have changed...
However, I can at least still arrange the furniture in my room(s). With some testing, I've decided that the optimum very-close location for a sub is going to be behind the chair, but up at (seated) head/ear height. Especially when reclining, that typically puts my ears closer to a subwoofer than having one at the side(s), since some chairs are reasonably wide (and/or have wings). It would also work if in the future the listening chair became a sofa.
It means pulling the chair forward into an already small room. However it isn't great to have the listening chair against a wall anyway, due to wall reflections from main speakers. Maybe I could arrange for some cabinets behind the chair, to support the sub(s) and perhaps be loaded with things that disperse or absorb reflections.
I'm thinking to make it a push/pull configuration to stop the raised subwoofer tying to move around or vibrate whatever shelf/cabinet it occupies. So it'll be around 13" (33cm) deep, and either bandpass or (more likely) slot loaded to guide the output into one coherent outlet close to the head.
Though yet again, this design has evolved past the original intent and no longer fits the title of the thread so I'll have to start a new one when I've firmed up my ideas slightly
It means pulling the chair forward into an already small room. However it isn't great to have the listening chair against a wall anyway, due to wall reflections from main speakers. Maybe I could arrange for some cabinets behind the chair, to support the sub(s) and perhaps be loaded with things that disperse or absorb reflections.
I'm thinking to make it a push/pull configuration to stop the raised subwoofer tying to move around or vibrate whatever shelf/cabinet it occupies. So it'll be around 13" (33cm) deep, and either bandpass or (more likely) slot loaded to guide the output into one coherent outlet close to the head.
Though yet again, this design has evolved past the original intent and no longer fits the title of the thread so I'll have to start a new one when I've firmed up my ideas slightly
This is a ripol, a special version of a dipol. This CAN be the solution for your challenge:It also occurs to me that a small sealed but slot-loaded configuration could offer 'some' similar benefits, at least in presenting a smaller opening. Like a sealed version of a SLOB
- Very deep, precise sound
- No worries with room modes -> very flexible to place in different rooms
- Good for small / medium rooms
- Very slim design
- Ridiculous low efficiency
- Requires specific driver parameters (moves a LOT of air)
- Complex calculation to make is sound well
- Active crossover (DSP) with 8th order low pass highly recommended to mitigate resonance peak around 200-300Hz
- Has a bad reputation (placed in to large rooms, bad design)
Yes they're also attractive for box size, but as you say, also some disadvantages.
I've tried a few designs in this kind of family (i.e. with an open back), for both subs and mains. They certainly have a lot of attractions, but I've personally always found them to be somewhat too fussy about position for my needs. In particular, not great for being placed close to walls, which is where I so often want them.
The thread has moved on a bit anyway now though; I must start a new one. For minimising room effects and maximising direct sound very close to the ears, I really want the sound to emminate from just one single point/area/direction.
I've tried a few designs in this kind of family (i.e. with an open back), for both subs and mains. They certainly have a lot of attractions, but I've personally always found them to be somewhat too fussy about position for my needs. In particular, not great for being placed close to walls, which is where I so often want them.
The thread has moved on a bit anyway now though; I must start a new one. For minimising room effects and maximising direct sound very close to the ears, I really want the sound to emminate from just one single point/area/direction.
That's exactly what a ripol does. Yes, don't place it with back to wall, but between 20 and 40 inches are enough distance. My most recent simulation delivers >85dB@20Hz in 8,2ft distance. And a max. of 92dB@60Hz (it's cut off with a LR8 low pass at 85Hz). This is one single cube of less than 16 inches per side. I'll stack two of them in a tower of 45-inch hight for more SPL.
P.S.: I'll build and measure the speaker in the next 2-3 weeks. I've chosen a pair of 12" Alpine car subwoofers. Reasonable priced and with a bit of luck they have the mechanical quality to deliver the 85dB without side noises.
Unfortunately even 20" and certainly 40" from walls is rarely practical in my situations, which is probably why I've had less than perfect results.
It is also why I'm becoming so keen on Charlie's 'very' nearfield approach instead, to sidestep unforcastable room modes. After some tests I believe this will be a much more successful answer, but of course only 'if' one can design specifically for just a small listening position. In future my circumstances may change, but I think it might be possible to design a sub that will work in both very nearfield and whole (small) room applications, without much additional cost as I already have parts that are big enough for the latter. Of course, some may simply use headphones, but for me these just aren't the same (and I've tried), hence my recent obsessions with main speakers that are either nearfield too, or (increasingly) of tightly controlled directivity.
So, I started a new design and a new thread here to reflect the new intentions.
It is also why I'm becoming so keen on Charlie's 'very' nearfield approach instead, to sidestep unforcastable room modes. After some tests I believe this will be a much more successful answer, but of course only 'if' one can design specifically for just a small listening position. In future my circumstances may change, but I think it might be possible to design a sub that will work in both very nearfield and whole (small) room applications, without much additional cost as I already have parts that are big enough for the latter. Of course, some may simply use headphones, but for me these just aren't the same (and I've tried), hence my recent obsessions with main speakers that are either nearfield too, or (increasingly) of tightly controlled directivity.
So, I started a new design and a new thread here to reflect the new intentions.