Not really wanting second hand with no warranty or waiting a few months to find them to be honest.
Do you have any first hand experience with the BK range of subs that is informing that advice or is there just an implicit assumption that "well known brands" and/or more expensive must always be better ?
While there is a certain minimum components cost to be able to build something good quality, beyond that point a lot of the money that you pay is perceived quality/prestige based on a brand name that doesn't necessarily translate into good performance per $$, and brands like B&W are often guilty of producing good but very overpriced products. (I used to regularly listen to a friends B&W Nautilus 802's and while they were certainly quite good they were flawed in several ways and very over priced for what they were)
It's hard to find good, technical reviews of subwoofers by people that actually know anything about speaker design, (just the usual flowery subjective golden ear stuff that doesn't impress me) so I'm having to use a bit of gut feeling looking at the designs of the different subwoofers based on previous speaker building experience, but at the end of the day buying any speaker without auditioning it is like buying a car without a test drive, and like cars, there is a lot of subjective opinion about what makes a good speaker... at least with new I have a period of time when I can send it back based on distance selling laws...
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I've built all my own subs for the last 25 years so cannot really help with specific store bought stuff (which is why I post on diyaudio.)
I remember looking at BK's stuff a long time ago when not many decent subwoofer drivers were available in the UK. (about the time Adire had brought out the Shiva and Tempest drivers) I ended up sourcing a pair of used Tempests here in the UK, and importing a 3rd one from the States.
The best manufactured stuff I've heard were the Paradigm servo15, and the Martin Logan Descent subs. Both happen to be servo feedback subs with very good distortion measurements.
If you are going multi sub then quality could probably drop a notch or two as the subs won't have to be driven as hard, hence why I suggested the cheap 15's at the start of this thread. I still plan to buy 4 of them and see how they do.
I guess I've been fairly lucky with used gear, I'd say about 1 in 25 things I've bought has been a dud.
The 12" drive unit BK sells looks pretty solid tbh, but I'd wince at paying £400 for a little square box with a 12" driver and a plate amp when I know I can buy a pro amp, driver and build a better box for a lot less money. Maybe I should have just said 'you may get a better performing subwoofer in the used market for the same money as the new BK'
Cheers,
Rob.
I remember looking at BK's stuff a long time ago when not many decent subwoofer drivers were available in the UK. (about the time Adire had brought out the Shiva and Tempest drivers) I ended up sourcing a pair of used Tempests here in the UK, and importing a 3rd one from the States.
The best manufactured stuff I've heard were the Paradigm servo15, and the Martin Logan Descent subs. Both happen to be servo feedback subs with very good distortion measurements.
If you are going multi sub then quality could probably drop a notch or two as the subs won't have to be driven as hard, hence why I suggested the cheap 15's at the start of this thread. I still plan to buy 4 of them and see how they do.
I guess I've been fairly lucky with used gear, I'd say about 1 in 25 things I've bought has been a dud.
The 12" drive unit BK sells looks pretty solid tbh, but I'd wince at paying £400 for a little square box with a 12" driver and a plate amp when I know I can buy a pro amp, driver and build a better box for a lot less money. Maybe I should have just said 'you may get a better performing subwoofer in the used market for the same money as the new BK'
Cheers,
Rob.
I'm a bit the same - while I've auditioned and listened to a lot of commercial speakers in different settings I've never actually bought any. My Dad built and sold many speakers so I grew up around home built speakers and by the time I left home I'd built some of my own and never ended up buying any over the years as I found speaker building an interesting hobby.
So if I bought this it would be the first fully built speaker I've ever purchased.
Unless you count a couple of passive "helper woofers" with some line level EQ I have not built any subwoofers before either, certainly not anything active with a low sensitivity driver and high power amp. So no real experience there either other than hearing other people's systems.
I totally get where you're coming from that you're reluctant to pay for something where you know you could build something comparable in performance for far less money, (not counting your time of course) I feel the same way about main speakers as I know what I can build with around £800 worth of drivers and materials would be multiple thousands to get comparable performance in the commercial market.
I also know that the types of designs that interest me (particularly large cabinet high sensitivity, wide bandwidth drivers, ribbon tweeters etc) go counter to current HiFi trends where everything is slim, low sensitivity etc.... so even if I was willing to spend the money there is very little commercial stuff that follows my design philosophy so if I want a speaker of that sort I basically have no choice but to build it myself anyway, and I'm happy to do that. (Although I do find the woodwork and surface finish side of it a bit of a struggle, it's not really my forte)
The problem with building my own subwoofer is that not only am I not in a position to build cabinets for the foreseeable future, (hence the stall on the main speakers build) I just don't find an active subwoofer an interesting project to work on.
Low sensitivity, high power, small closed cabinet is the antithesis of my design philosophy and while I can turn a blind eye to a box that I just buy and plug in, I just don't find designing or building something like that interesting.
Another factor is the age old when you're young you have lots of time and no money, when you get older you have more money and less time... and that's definitely starting to bite me now. I used to do all my own car maintenance on a shoe string and enjoyed doing it, now its becoming a bit more of a chore and taking up precious free time that I don't really have, and I find myself more often taking certain jobs to a garage that I would have done myself in the past.
I see a subwoofer project in a similar vein - because it doesn't interest me the only reason I would build it myself is to save a bit of money, but I really don't have the time to do it justice. I'm willing to pay a little bit extra over the raw materials cost for someone to do the work for me using a proven design...
Main speakers are a different story - I'm still very interested in my next main speaker project, I have all the drivers ready to go, I have the overall design and crossover design in mind and have experimented with some crossovers in Vituixcad, but I need to build some prototype cabinets and flesh out the smaller details of the cabinet and crossover. I know it will work as it's based on a couple of previous designs I've built which worked great, this is a more modern take on those previous designs with similar but better quality drivers and a lot more experience going into the measurement and crossover design.
I can't wait but until I can get my work area and some free time back I'm stuck.
As in my first post, ultimately the main speakers will be high-ish sensitivity 110 litre bass reflex designs with a 12" woofer - sensitivity should be around 92dB/W/M, and based on past experience using those same drivers in a smaller closed box with some active EQ in a much larger room than I have now should have some serious punch when able to breathe properly in a larger bass reflex box that better suits the driver.
In that scenario the subwoofers are really just there to provide modal smoothing primarily in the 40-150Hz region, as if the main speakers are good down to 25Hz I'm fine with that, I'm not interested in wall shaking <20Hz stuff, just good solid music reproduction down to around 25Hz without any pesky holes in the mid and upper bass.
And by that point I'd have a minimum of two subs overlapping with the main speakers so I suppose technically if the mains go down to 25hz that would be a 4 "sub" system since the main speakers would have comparable performance to the sub albeit achieved with a bass reflex box a bit more than twice the size and a much higher efficiency driver.
I don't think I'll be able to physically fit a 3rd sub into this room unless I chose something a bit smaller than the P12-300SB-DF and it may not be necessary at all by that point, it remains to be seen depending on how the standing wave issues work out...
In the interim even a single sealed 12" powered subwoofer should give a significant improvement on the two small 8" full range drivers in bass reflex cabinets - they do remarkable work for a full range driver with a genuine solid bass output down to about 40Hz but fall off a cliff below that.
More annoying to me is the boundary cancellation effects of the midwoofer being so far from the room boundaries - while I can tame the peaks at 41, 71 and 105Hz I can't do anything about the major holes around 85Hz (nearly complete cancellation at the prime listening location) and big holes in the 110-150Hz range as well.
Solving those holes through subwoofer placement is actually the primary object of the current exercise. If I get improved extension over what I have now as well that's a nice bonus.
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One thing I noticed wrt sub drivers versus 'hifi' drivers. When I was running twin sealed scanspeak 8565-01's as the bass units in my mains (approx 120L cabs) The bass quality of the scanspeaks outperformed my tempests noticably. If I ran the tempests up to 40Hz and the scanspeaks 40Hz and up, it was so much better than running the tempests up to 80Hz.
(Aphex Twins remix of Flow coma used to bottom out the 10's if crossed at 40Hz 😀)
So maybe if you end up deciding to build something in the future you could consider multiples of the driver you are using in your mains, and maybe 1 biggish thing in a corner to do ~15 - 30Hz.
I hid one of my double 12 cabs under an ikea bookcase. Kind of blends in.
Cheers,
Rob.
(Aphex Twins remix of Flow coma used to bottom out the 10's if crossed at 40Hz 😀)
So maybe if you end up deciding to build something in the future you could consider multiples of the driver you are using in your mains, and maybe 1 biggish thing in a corner to do ~15 - 30Hz.
I hid one of my double 12 cabs under an ikea bookcase. Kind of blends in.
Cheers,
Rob.
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Ok so after a couple of weeks waiting the BK P12-300SB-DF arrived and I had a play around with initial setup last night and unfortunately I'm fairly underwhelmed. 🙁
I've noticed a few issues right off the bat:
1) It puts out a very audible hum when its turned on even with no cables connected and levels set to minimum. I've tried a couple of locations in the room and it's currently in the opposite corner near the right main speaker so about 3 metres from the listening position and I can clearly hear it humming from that distance when the room is quiet, which really isn't good enough and to be honest is a deal breaker for me making me consider sending it back.
Despite all the equipment in my AV cabinet, I've put a bit of effort into getting the living room quiet and it is almost silent at the listening position when music etc is paused. Not anymore with this subwoofer turned on.
It's not 50Hz hum, it's some multiple, possibly 3rd harmonic. I'm also not actually sure the hum is being produced by the driver, as putting some fingers on the cone doesn't make any difference.
listening to the cabinet it sounds like it's vibration from the power supply components being radiated through the wooden cabinet, albeit I don't know what kind of power supply it uses without opening it up.
So that was pretty disappointing as I noticed it immediately when I first switched it on. When the auto off activates after 10 minutes the LED changes from green to red but the hum remains!
2) Instead of a phase switch it has a continuously variable phase control. However when it's set to 0 degrees there is severe cancellation with my main speakers everywhere below about 60Hz and I actually have to turn it to 180 degrees for it to be in phase.
This shouldn't be the case with the subwoofer positioned relatively close to the main speaker - I'm also using the high level input on the subwoofer connected to the main amp output so the phasing of my main amp / pre-amp etc is eliminated as a cause - it's tapping the same signal that's going to my passive main speakers.
Big deal, just set it to 180 I hear people cry - unfortunately unlike a 0/180 phase switch, the variable phase control seems to have no effect at all above about 60Hz. With both main speakers and subwoofer on and overlapping there is a notch at 120Hz due to cancellation which goes away if I turn either main speakers or subwoofer off, so being able to adjust the phase a bit in this region would be beneficial but no, no effect whatsoever from the phase control at frequencies above about 60Hz.
I have a feeling that the issue might be with the high level input - I'm going to do some phase testing with a scope and ARTA to try to narrow down what's going on here.
3) Claimed frequency response isn't even remotely accurate. "-3dB lower than 20Hz" is the vague claim, but it simply doesn't come anywhere near that.
Currently my mains speakers as mentioned earlier are two 8" full range drivers as midwoofers up to 3Khz, (with a ribbon tweeter) they're in 43 litre bass reflex enclosures tuned to 41Hz.
Nearfield (summed driver/port) measurements show their anechoic response is about 6dB down at 40Hz and they have a sort of early gradual roll-off slope. (No B4 here...)
In room they are pretty solid and punchy down to 40Hz (I actually have to notch the 40Hz fundamental room mode down by about 6dB...) and still have useful output down to 35Hz then nothing below 30Hz.
I was kind of expecting the subwoofer to be able to extend the bottom end response down to at least 25Hz but no dice!
There is absolutely zero audible output in room at 25Hz from this subwoofer either by itself or with the mains still running. It's output goes down to about 35Hz well, is still audible at 30Hz then drops like a rock below 30Hz with nothing audible below 30Hz.
Songs that I'm familiar with with lowest bass note around 25Hz are still missing in action with the subwoofer.
In short, although I haven't measured it yet, the low end cut-off is pretty much identical to my 8" bass reflex main speakers and adding the subwoofer does not extend the low frequency cut off at all... That's pretty disappointing and inexplicable to me especially given the mains are high sensitivity, light cone (8 gram) full range drivers competing against a heavy 12" subwoofer driver in the same size enclosure! (Mind you they have always punched above their weight for bass)
Granted its a small room with its lowest mode at 40Hz but I thought I would have heard something below 30Hz from a sealed, 12dB/oct roll off woofer that claims to go below 20Hz. 🙁
I need to do some nearfield measurements of this subwoofer to identify the frequency of the hum, measure the true nearfield response to see if it comes anywhere remotely close to the claimed response, and also try to figure out what this phase control is doing (it only seems to bend the phase at low frequencies) and whether the phase of this thing is reversed when it says it's set to 0 on the high level and/or low level inputs.
I've got a couple of weeks to decide whether to return it or not by distance selling laws, if the hum can't be fixed I think I'm going to have to unfortunately.
Anyone have any thoughts on these issues ?
I've noticed a few issues right off the bat:
1) It puts out a very audible hum when its turned on even with no cables connected and levels set to minimum. I've tried a couple of locations in the room and it's currently in the opposite corner near the right main speaker so about 3 metres from the listening position and I can clearly hear it humming from that distance when the room is quiet, which really isn't good enough and to be honest is a deal breaker for me making me consider sending it back.
Despite all the equipment in my AV cabinet, I've put a bit of effort into getting the living room quiet and it is almost silent at the listening position when music etc is paused. Not anymore with this subwoofer turned on.
It's not 50Hz hum, it's some multiple, possibly 3rd harmonic. I'm also not actually sure the hum is being produced by the driver, as putting some fingers on the cone doesn't make any difference.
listening to the cabinet it sounds like it's vibration from the power supply components being radiated through the wooden cabinet, albeit I don't know what kind of power supply it uses without opening it up.
So that was pretty disappointing as I noticed it immediately when I first switched it on. When the auto off activates after 10 minutes the LED changes from green to red but the hum remains!
2) Instead of a phase switch it has a continuously variable phase control. However when it's set to 0 degrees there is severe cancellation with my main speakers everywhere below about 60Hz and I actually have to turn it to 180 degrees for it to be in phase.
This shouldn't be the case with the subwoofer positioned relatively close to the main speaker - I'm also using the high level input on the subwoofer connected to the main amp output so the phasing of my main amp / pre-amp etc is eliminated as a cause - it's tapping the same signal that's going to my passive main speakers.
Big deal, just set it to 180 I hear people cry - unfortunately unlike a 0/180 phase switch, the variable phase control seems to have no effect at all above about 60Hz. With both main speakers and subwoofer on and overlapping there is a notch at 120Hz due to cancellation which goes away if I turn either main speakers or subwoofer off, so being able to adjust the phase a bit in this region would be beneficial but no, no effect whatsoever from the phase control at frequencies above about 60Hz.
I have a feeling that the issue might be with the high level input - I'm going to do some phase testing with a scope and ARTA to try to narrow down what's going on here.
3) Claimed frequency response isn't even remotely accurate. "-3dB lower than 20Hz" is the vague claim, but it simply doesn't come anywhere near that.
Currently my mains speakers as mentioned earlier are two 8" full range drivers as midwoofers up to 3Khz, (with a ribbon tweeter) they're in 43 litre bass reflex enclosures tuned to 41Hz.
Nearfield (summed driver/port) measurements show their anechoic response is about 6dB down at 40Hz and they have a sort of early gradual roll-off slope. (No B4 here...)
In room they are pretty solid and punchy down to 40Hz (I actually have to notch the 40Hz fundamental room mode down by about 6dB...) and still have useful output down to 35Hz then nothing below 30Hz.
I was kind of expecting the subwoofer to be able to extend the bottom end response down to at least 25Hz but no dice!
There is absolutely zero audible output in room at 25Hz from this subwoofer either by itself or with the mains still running. It's output goes down to about 35Hz well, is still audible at 30Hz then drops like a rock below 30Hz with nothing audible below 30Hz.
Songs that I'm familiar with with lowest bass note around 25Hz are still missing in action with the subwoofer.
In short, although I haven't measured it yet, the low end cut-off is pretty much identical to my 8" bass reflex main speakers and adding the subwoofer does not extend the low frequency cut off at all... That's pretty disappointing and inexplicable to me especially given the mains are high sensitivity, light cone (8 gram) full range drivers competing against a heavy 12" subwoofer driver in the same size enclosure! (Mind you they have always punched above their weight for bass)
Granted its a small room with its lowest mode at 40Hz but I thought I would have heard something below 30Hz from a sealed, 12dB/oct roll off woofer that claims to go below 20Hz. 🙁
I need to do some nearfield measurements of this subwoofer to identify the frequency of the hum, measure the true nearfield response to see if it comes anywhere remotely close to the claimed response, and also try to figure out what this phase control is doing (it only seems to bend the phase at low frequencies) and whether the phase of this thing is reversed when it says it's set to 0 on the high level and/or low level inputs.
I've got a couple of weeks to decide whether to return it or not by distance selling laws, if the hum can't be fixed I think I'm going to have to unfortunately.
Anyone have any thoughts on these issues ?
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I feel your pain with the hum, returned a brand new amp recently that was so loud it might as well of had a fan in it...
Maybe try a heavy concrete / marble slab on top to damp the enclosure ?
Re: Phase, can you swap the + and - connections at your main speakers to cure it ?
Cheers,
Rob.
Maybe try a heavy concrete / marble slab on top to damp the enclosure ?
Re: Phase, can you swap the + and - connections at your main speakers to cure it ?
Cheers,
Rob.
Unfortunately it's quite high frequencies. I did some measurements today and while there is a small amount of 50, 100, 150Hz hum directly from the woofer, it's very low in level and not audible at a normal seating distance.
However the noise I'm hearing is coming from the plate amplifier and measurements are showing it has peak spectra at 200, 300 and 400Hz.
This fits in with what I was hearing - it sounded like a 300Hz tone to me, (which will propogate very easily in the room especially with the subwoofer in a corner where it will reflect from the corners) and 300Hz is indeed the largest peak.
A little bit of research suggests that it might be DC bias on the AC mains affecting a toroidal power transformer, although I'm a little sceptical as I've never had this issue on any other equipment in the past.
Unfortunately no, because the high level input cable uses 3 wires with a shared earth connection for both channels. So no way to reverse the phase and still sample both left and right channels. (The same would apply to the low level inputs to be honest, as they would share an earth as well. You could only get away with this if you were connecting to one channel)
I've done a whole host of measurements tonight - both the hum from the driver and plate amplifier, as well as a full set of nearfield frequency response measurements for every low pass filter setting.
Unfortunately the measurements confirm my fears and what I observed subjectively during my initial attempts to set it up. It's getting a bit late tonight so I'll post the measurements and some analysis tomorrow.
In short, it's probably going back after I give them a chance to respond and address (or not) the problems. As it stands it doesn't come anywhere near meeting its claimed low frequency response and the 200/300/400Hz tones coming from the power supply are far too intrusive in a quiet room especially when the tones remain even in auto-standby mode. I went to some trouble to make sure all the other myriad of equipment in the AV centre are whisper quiet so I don't want an always humming subwoofer to ruin that. 🙁
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Not quite sure I follow,
Speaker outputs are AC so should not have an earth as such ?
If you run the speaker outs from your amp to your main speakers + to +, and -to - , and the same speaker outs to your subwoofer + to - and - to + then you will switch polarity at the sub 180 degrees without using your phase knob.
Hope this makes sense,
Rob.
Speaker outputs are AC so should not have an earth as such ?
If you run the speaker outs from your amp to your main speakers + to +, and -to - , and the same speaker outs to your subwoofer + to - and - to + then you will switch polarity at the sub 180 degrees without using your phase knob.
Hope this makes sense,
Rob.
Isolation audio transformer or equivalent for just testing?*
I'm in the group that believes the right polarity is the one that sounds/measures better than the opposite. Hard to predict which will be over-all best in anybody's real-world setting.
B.
* OK, maybe already considered but my patience for prolix texts getting shorter each year.
I'm in the group that believes the right polarity is the one that sounds/measures better than the opposite. Hard to predict which will be over-all best in anybody's real-world setting.
B.
* OK, maybe already considered but my patience for prolix texts getting shorter each year.
No, that can't work, and you will do damage trying, so please don't try it yourself.
Whether or not the signal is AC is irrelevant - there is a signal ground reference on both devices.
On most stereo amps (which don't use bridge configuration output stages) the negative of both left and right speaker outputs are tied to the common signal ground reference and are thus tied together. (check it with an ohm meter...)
This signal ground is an internal reference in the circuitry of the amplifier and tends not to be connected to the chassis to avoid hum loops. The power supply will have say +/- 50 volt DC rails and the signal ground half way between those (0v) will be connected to both speaker negative terminals allowing the "positive" terminals to swing both positive and negative relative to the "negative" terminal.
The nomenclature is wrong, really, speaker + and - should really be called signal and signal ground.
At the subwoofer end the left and right inputs will likewise have their "negatives" tied together.
If you flip the polarity of the wires going from the amplifier to the subwoofer and connect to both left and right channels you will put a short across the output of the amplifier.
It's not a signal hum loop. The hum is (probably) coming from the transformer in the power supply, eg the transformer is vibrating. It hums all the time regardless of whether there are any signal cables connected and in fact it keeps humming even after the auto-off activates.
Sure, I agree, phase is a complicated thing for bass especially when you have what is essentially a bandpass filter as you have a mechanical high pass and an electrical low pass, and your main speakers have their own phase shifts.
The "centre" of this bandpass is around 60Hz so you would expect the driver to be in phase in the middle of the bandpass however with the phase control set to 0 degrees it is 180 degrees out of phase, and setting it to 180 does not fix this either.
There is a full 360 degrees of phase rotation between 160Hz and 40Hz on this subwoofer - it's in phase at 160Hz, out of phase at 60hz and in phase again at about 40Hz - all with the phase control set to 0 degrees. It should be opposite to this.
Most subwoofers have a 0/180 switch, that actually does reverse the phase at every frequency, however this only has a knob and from what I can see it has some kind of all pass filter with the knob adjusting the rollover point of the all pass filter. In short the phase is a mess. Give me a simple 0/180 switch instead any day.
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Ok now for some measurements. First the "hum" that I can hear clear across the room which sounds like low midrange frequencies.
It could either be reproduced by the woofer or by the transformer in the power supply, so I checked both.
Here is a nearfield measurement of the woofer with it switched on with no signal applied:
Green is ambient noise in the room before turning the subwoofer on, yellow is the additional noise added by the subwoofer.
Quite a bit of 50Hz fundamental and 150Hz 3rd harmonic is visible but the level is lower than this makes it appear as I'm doing a nearfield measurement, and this 50/150Hz hum is not audible at a normal listening distance.
Now a measurement taken a couple of inches away from the back of the plate amplifier:
Like before, green was ambient room noise as a reference with yellow being after the subwoofer is switched on.
The spectral balance is completely different here. A small amount of 50Hz but the largest peaks are 200, 300, 400Hz, and its those that I'm hearing from right across the room in a quiet room.
300Hz propagates very well into the room especially when the subwoofer is in the corner.
My ears are still not too bad - when I first heard the "hum" I though it sounded like lower midrange "somewhere around 300Hz" rather than 50hz and I was spot on.
Small comfort from being right about something that annoys me though. 🙁 To me this low midrange tone is unacceptably loud given the noise is there all the time unless you manually switch it off. I'm sitting 3.5 metres away from it and it's very obvious when the room is quiet.
It could either be reproduced by the woofer or by the transformer in the power supply, so I checked both.
Here is a nearfield measurement of the woofer with it switched on with no signal applied:
Green is ambient noise in the room before turning the subwoofer on, yellow is the additional noise added by the subwoofer.
Quite a bit of 50Hz fundamental and 150Hz 3rd harmonic is visible but the level is lower than this makes it appear as I'm doing a nearfield measurement, and this 50/150Hz hum is not audible at a normal listening distance.
Now a measurement taken a couple of inches away from the back of the plate amplifier:
Like before, green was ambient room noise as a reference with yellow being after the subwoofer is switched on.
The spectral balance is completely different here. A small amount of 50Hz but the largest peaks are 200, 300, 400Hz, and its those that I'm hearing from right across the room in a quiet room.
300Hz propagates very well into the room especially when the subwoofer is in the corner.
My ears are still not too bad - when I first heard the "hum" I though it sounded like lower midrange "somewhere around 300Hz" rather than 50hz and I was spot on.
Small comfort from being right about something that annoys me though. 🙁 To me this low midrange tone is unacceptably loud given the noise is there all the time unless you manually switch it off. I'm sitting 3.5 metres away from it and it's very obvious when the room is quiet.
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The other main problem I noted is that it simply doesn't live up to the stated low frequency response. Not even remotely. 🙁
The stated response is a somewhat vague "-3dB lower than 20Hz". Is this an in room response (room gain included) or a true (nearfield) response ? Either way it doesn't meet either possibility.
In room it only works well down to about 35Hz and is completely inaudible below 30Hz. So basically it only goes a few Hz lower than my 8" bass reflex main speakers.
I haven't been able to find any measurements for this subwoofer online, so here are my own measurements.
These were taken using ARTA and a calibrated microphone that should be accurate to <20Hz. I took a measurement for each increment on the low pass filter setting although I've only shown some of them here otherwise the graph gets too cluttered:
-3dB at 20Hz ? I think not.
Due to the overlap of the low pass filter, depending on where you set the low pass filter the -3dB and -6dB points do move a bit but here are a couple of examples:
With the low pass filter set to the maximum 120Hz setting the speaker is -3dB at 46Hz, -6dB at 38Hz and -17dB at 20Hz.
With a more typical low pass filter setting of 80Hz (orange line) the speaker is -3dB at 38Hz, -6dB at 30Hz and -13dB at 20Hz.
So, yeah... not good. Looking at the response it's clearly just the response of a large 12" woofer in a small (40 litre) sealed box without any active equalisation such as a Linkwitz transform to improve the F3.
Given the stated specs I just assumed it would be using a Linkwitz transform but it is definitely not, hence why it starts rolling off so high. You're not going to get the stated frequency response in a closed box this size without a lot of active EQ.
I had it plugged in via a 3 pin kWh meter to see how much power it draws and sweeping from 60Hz down the power doesn't increase at all in fact it drops a bit, whereas a Linkwitz transform to reduce F3 by an octave would cause approximately a 10x increase in power as you go down that octave.
So yeah, very disappointing and it certainly fits in with my subjective impression of "no bass at all below 30Hz". I generally find the -6dB point on a nearfield measurement agrees well with the lowest useable frequency in-room and that is the case here too.
For fun I decided to overlay the nearfield low frequency roll off with nearfield measurements of my existing main speakers, which are only 8" full range drivers in a bass reflex cabinet of about 40 litres.
Of course they ultimately roll off at a steeper rate due to being bass reflex, but they're within 3dB of this "subwoofer" right down to 35Hz, and below 30Hz neither set of speakers is audible anyway so the difference becomes academic.
Subjectively, down to 35Hz there really isn't much between them when an actively powered 12" subwoofer (with a proper Linkwitz transform) should be able to trounce them on low frequency extension.
So cavet emptor. 🙁 This will be going back and I can't recommend this model knowing what I know now.
The shame of it all is if it did have a proper Linkwitz Transform to extend the response another octave, and the power supply didn't have a noisy transformer, it would be a pretty decent subwoofer for the price. The box itself is solid, the driver looks pretty decent, it claims to have a 300 watt amplifier - so enough headroom for about an octave of Linkwitz transform to lower the F3 etc...
But as is often the case with speaker designs, the devil is in the details! The difference between a great speaker and a very average one can often be small details.
The stated response is a somewhat vague "-3dB lower than 20Hz". Is this an in room response (room gain included) or a true (nearfield) response ? Either way it doesn't meet either possibility.
In room it only works well down to about 35Hz and is completely inaudible below 30Hz. So basically it only goes a few Hz lower than my 8" bass reflex main speakers.
I haven't been able to find any measurements for this subwoofer online, so here are my own measurements.
These were taken using ARTA and a calibrated microphone that should be accurate to <20Hz. I took a measurement for each increment on the low pass filter setting although I've only shown some of them here otherwise the graph gets too cluttered:
-3dB at 20Hz ? I think not.
Due to the overlap of the low pass filter, depending on where you set the low pass filter the -3dB and -6dB points do move a bit but here are a couple of examples:With the low pass filter set to the maximum 120Hz setting the speaker is -3dB at 46Hz, -6dB at 38Hz and -17dB at 20Hz.
With a more typical low pass filter setting of 80Hz (orange line) the speaker is -3dB at 38Hz, -6dB at 30Hz and -13dB at 20Hz.
So, yeah... not good. Looking at the response it's clearly just the response of a large 12" woofer in a small (40 litre) sealed box without any active equalisation such as a Linkwitz transform to improve the F3.
Given the stated specs I just assumed it would be using a Linkwitz transform but it is definitely not, hence why it starts rolling off so high. You're not going to get the stated frequency response in a closed box this size without a lot of active EQ.
I had it plugged in via a 3 pin kWh meter to see how much power it draws and sweeping from 60Hz down the power doesn't increase at all in fact it drops a bit, whereas a Linkwitz transform to reduce F3 by an octave would cause approximately a 10x increase in power as you go down that octave.
So yeah, very disappointing and it certainly fits in with my subjective impression of "no bass at all below 30Hz". I generally find the -6dB point on a nearfield measurement agrees well with the lowest useable frequency in-room and that is the case here too.
For fun I decided to overlay the nearfield low frequency roll off with nearfield measurements of my existing main speakers, which are only 8" full range drivers in a bass reflex cabinet of about 40 litres.
Of course they ultimately roll off at a steeper rate due to being bass reflex, but they're within 3dB of this "subwoofer" right down to 35Hz, and below 30Hz neither set of speakers is audible anyway so the difference becomes academic.
Subjectively, down to 35Hz there really isn't much between them when an actively powered 12" subwoofer (with a proper Linkwitz transform) should be able to trounce them on low frequency extension.
So cavet emptor. 🙁 This will be going back and I can't recommend this model knowing what I know now.
The shame of it all is if it did have a proper Linkwitz Transform to extend the response another octave, and the power supply didn't have a noisy transformer, it would be a pretty decent subwoofer for the price. The box itself is solid, the driver looks pretty decent, it claims to have a 300 watt amplifier - so enough headroom for about an octave of Linkwitz transform to lower the F3 etc...
But as is often the case with speaker designs, the devil is in the details! The difference between a great speaker and a very average one can often be small details.
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That would be one option, yes.
Another option would be to reverse the connections to the driver in the sub itself. I won't be doing that if I'm sending it back though obviously.
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I was pondering whether you could do a 20Hz 6db/octave passive lowpass between your amp and the sub to flatten it out, but it seems a lot of messing about.
The other thought was take the new sub apart and build a ported enclosure for it 😀 (joke)
Rob.
The other thought was take the new sub apart and build a ported enclosure for it 😀 (joke)
Rob.
Just to close the loop I returned this subwoofer for a refund on the basis of (a) noisy power supply and (b) low frequency response doesn't come anywhere near matching the claims, so I've chalked it up to a learning experience.
I'm going to put the money towards accelerating the build of my large 3 way main speakers instead.
I'm going to put the money towards accelerating the build of my large 3 way main speakers instead.
Why not align and EQ, I’m flat to within 6db from 8-60 HZ across a 2m seating area with 3 12” and one 18” with no shelf or boost just PEQ at the main nodes
When it's 17dB down at 20Hz that's a lot of active EQ... 😛
To do what you're suggesting I would need to buy another EQ unit so I could apply EQ separately to the sub, just to try to approach it's original claimed response.
There's no guarantee that it could take that much low frequency boost without clipping at useful volume levels - if it doesn't already have a Linkwitz transform or similar built in then it's likely it won't.
Applying large amounts of EQ also doesn't help with the noisy power supply which to be honest was the problem I really couldn't look past.
Better to just send it back during the no questions asked return period, which is what I did.
I was looking at your 41HZ peak as the main problem ?
Are the BK measurements taken outside and far enough away from walls or reflective surfaces
For sure if your issue is hum and very low LF performance then clearly your on a non starter
I have a significant 34Hz peak with 17'x17' room size coincident at 34 front and back walls, I get this with one 18" and 3 12" properly aligned across a 2m seating area, with NO boost but some heavy PEQ's around the problems, you will need avoid clipping with gain, hence the reason the LFE channel in multichannel is set -10db
Are the BK measurements taken outside and far enough away from walls or reflective surfaces
For sure if your issue is hum and very low LF performance then clearly your on a non starter
I have a significant 34Hz peak with 17'x17' room size coincident at 34 front and back walls, I get this with one 18" and 3 12" properly aligned across a 2m seating area, with NO boost but some heavy PEQ's around the problems, you will need avoid clipping with gain, hence the reason the LFE channel in multichannel is set -10db
I think you're confusing room measurements with nearfield measurements.
The measurement showing the room response with a large peak at 41Hz is exactly that - a room response taken at the listening sofa with the main speakers alone and no subwoofer.
The measurements of the BK sub I posted later are nearfield measurements, aka quasi-anechoic measurements of the subwoofer by itself and do not include the effects of the room.
They are measuring the true roll off of the subwoofer before room effects add their contribution, and these measurements show the true response of this subwoofer is down 17dB at 20Hz.
Of course while I didn't show it, if you took a room measurement of this subwoofer from a distance the room modes would cause frequencies down to around 41Hz to be boosted a lot and counteract most of the roll off, however once you go below the fundamental room mode (41Hz in my room) the room response will drop off a cliff - and that's exactly what happens in practice with the response being inaudible below 30Hz.
If you have a large room with a low fundamental mode you can get away with a woofer with an early roll off as the room will keep boosting the bass down to that fundamental mode.
But if you're in a small room like I am with a fundamental mode of 41Hz and you want to produce bass down to 25Hz (let alone 20Hz) there is no getting out on the cheap - the woofer has to have true response down to those very low frequencies and 17dB down at 20Hz just won't cut it.
Yes, it's a non-starter for me. It's simply too noisy when the room is quiet.
Yes, as described above the fundamental room mode will provide a lot of boost, as much as 12dB is typical - my main speakers are about 6dB down at 40Hz measured nearfield yet there is still a peak of around 6dB at 40Hz in room. (Implying the peak would be around 12dB if the speaker was flat beyond 40Hz)
However below that fundamental mode the room gain disappears and the response will fall like a rock if the woofer is already steeply rolling off by that point.
To go lower in a small room you need a significantly more capable woofer to produce the very low frequencies below the fundamental room mode and then EQ to pull down the massive peak that you'll get at that fundamental mode, eg 41Hz in my room. (Or use woofers at both front and rear of the room to acoustically cancel that mode)
In any case this particular model of BK sub doesn't have anywhere near the low frequency response needed to produce those low frequencies below the fundamental room resonance where there is no gain from the room modes.
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