With the UK live music scene comatose, I have chosen to create (yet another) portable system for myself and some others to enjoy as or when we can.
Below are the specifications with my current projection below:
1. Volume must fit inside a large backpack. Maximum 60L.
Fits in backpack, enclosure volume measured 57L
2. Weight must not exceed 10kg (excluding backpack itself)
Current complete mass estimate 9,5Kg
3. Weight distribution must allow full days hike
Check (good CoG/MoI)
4. Low extension F3 60Hz
Current F3 = 60Hz , F10 = 47Hz (winISD)
5. Simulation peak SPL to hit 116dB at peak, 110dB 50Hz
Current max SPL = 118dB (winISD), 50Hz = 110dB
6. Power distribution must be 90 horizontal x 70+ vertical. More the merrier.
Constant directivity horn supports this
7. No enclosure modes or resonances
Current modal analysis moves all fundamentals 400Hz+
7. Battery is to last 4hrs at full pelt, 12hrs at 100dB (sim)
Estimated life at full = 5.5hrs, 100dB = 22hrs.
8. DSP on board w/ missing fundamental
Check
Here is the current plan for the build:
Electronics
Power source: 36v 354Wh ebike battery (already owned)
Amplifier: 3e TPA3255
DSP: Sure ADAU1701 (already owned)
Buck converter (option to bypass, only used if want to sacrifice battery for a couple of dB): 400w Chinese module (already owned)
Drivers
LF driver: 1x B&C 12CL64 (1.9kg! BL:17.5, qts: 0.3)
12CL64 LF Drivers - B&C Speakers
HF driver: 1x B&C DE111 (320g! 1.2kHz full power XO)
DE111 HF Drivers - B&C Speakers
Horn: 1x RCF H100 (800hz cutoff, 90x75, CD)
Product Detail - RCF
Enclosure
Material: Poplar plywood, 9mm
External dimensions: 65 x 35 x 25cm
Coating: PU laquer
Tuned: vent at 60Hz
Build methodology: Braced as per FEM and battened at edges (18mm glue area)
How do you all feel this is as a plan to hit the specifications? Is there any other creative approach you would consider?
The LF section is of course the limiting factor for both battery life and SPL. I have looked at BP6 and tapped horn (such as cubo12) arrangements, but I am struggling to get any to work better in the 45L range. As per equal loudness and directivity, I expect around +12dB of gain to be added around 60Hz to keep it sounding 'full' outdoors
Otherwise, would you rather pair the LF with a 5/6" midrange driver (eg B&C MDN38) and tweeter (eg P-audio PHT-407N) with a passive XO? Do you feel the integration or intelligibility would be worth the extra cost and complexity?
Cheers,
Below are the specifications with my current projection below:
1. Volume must fit inside a large backpack. Maximum 60L.
Fits in backpack, enclosure volume measured 57L
2. Weight must not exceed 10kg (excluding backpack itself)
Current complete mass estimate 9,5Kg
3. Weight distribution must allow full days hike
Check (good CoG/MoI)
4. Low extension F3 60Hz
Current F3 = 60Hz , F10 = 47Hz (winISD)
5. Simulation peak SPL to hit 116dB at peak, 110dB 50Hz
Current max SPL = 118dB (winISD), 50Hz = 110dB
6. Power distribution must be 90 horizontal x 70+ vertical. More the merrier.
Constant directivity horn supports this
7. No enclosure modes or resonances
Current modal analysis moves all fundamentals 400Hz+
7. Battery is to last 4hrs at full pelt, 12hrs at 100dB (sim)
Estimated life at full = 5.5hrs, 100dB = 22hrs.
8. DSP on board w/ missing fundamental
Check
Here is the current plan for the build:
Electronics
Power source: 36v 354Wh ebike battery (already owned)
Amplifier: 3e TPA3255
DSP: Sure ADAU1701 (already owned)
Buck converter (option to bypass, only used if want to sacrifice battery for a couple of dB): 400w Chinese module (already owned)
Drivers
LF driver: 1x B&C 12CL64 (1.9kg! BL:17.5, qts: 0.3)
12CL64 LF Drivers - B&C Speakers
HF driver: 1x B&C DE111 (320g! 1.2kHz full power XO)
DE111 HF Drivers - B&C Speakers
Horn: 1x RCF H100 (800hz cutoff, 90x75, CD)
Product Detail - RCF
Enclosure
Material: Poplar plywood, 9mm
External dimensions: 65 x 35 x 25cm
Coating: PU laquer
Tuned: vent at 60Hz
Build methodology: Braced as per FEM and battened at edges (18mm glue area)
How do you all feel this is as a plan to hit the specifications? Is there any other creative approach you would consider?
The LF section is of course the limiting factor for both battery life and SPL. I have looked at BP6 and tapped horn (such as cubo12) arrangements, but I am struggling to get any to work better in the 45L range. As per equal loudness and directivity, I expect around +12dB of gain to be added around 60Hz to keep it sounding 'full' outdoors
Otherwise, would you rather pair the LF with a 5/6" midrange driver (eg B&C MDN38) and tweeter (eg P-audio PHT-407N) with a passive XO? Do you feel the integration or intelligibility would be worth the extra cost and complexity?
Cheers,
Attachments
Your plan to hit the specifications looks good, and BR for the size, weight and reasonable LF is probably the best approach in the 45L range.
A midrange driver and tweeter (eg P-audio PHT-407N) with a passive XO would add weight and a lot of build complexity, an intelligibility reduction, and extra cost.
Being old, weight has become more a concern to me than the last dB, the B&C10CL51 is less than half the weight of the B&C 12CL64.
The 10CL51 has a 60Hz Fc, using a 60Hz FB in the same box size might not need as much boost for the "boom", worth a sim. Using NU4-6000 (430w peak @8ohm) I have hammered on 10CL51s in small ported cabinets with power peaks above it's "300 watt continuous" rating with no problems, and good sound.
I'd be interested in seeing the sim comparison between the two drivers.
Happy hunting!
Art
A midrange driver and tweeter (eg P-audio PHT-407N) with a passive XO would add weight and a lot of build complexity, an intelligibility reduction, and extra cost.
Being old, weight has become more a concern to me than the last dB, the B&C10CL51 is less than half the weight of the B&C 12CL64.
The 10CL51 has a 60Hz Fc, using a 60Hz FB in the same box size might not need as much boost for the "boom", worth a sim. Using NU4-6000 (430w peak @8ohm) I have hammered on 10CL51s in small ported cabinets with power peaks above it's "300 watt continuous" rating with no problems, and good sound.
I'd be interested in seeing the sim comparison between the two drivers.
Happy hunting!
Art
Last edited:
Uh, wow! I thought I was creative fitting my autoharp+vocal rig in my bicycle panniers.
Does your amp have phantom power? My voice is too soft even for autoharp, I'm using a 1" diaphragm stellar labs condensor mike for both voice & instrument.
I have an 840 wh 48 v battery on the bike but at this point my $30 amp is 120 vac. MMA875t with 2 input cards. Will have to modify the amp to use some DC source besides an inverter. Internally it is +-40 v .
A picture or plan of the speaker would be nice. I'm using a visiton 6.5" whizzer cone driver in an 8"x8"x14" amazon cardboard box with the end cut out. 1" hole in other end for bass reflex. Of course I don't need 60 hz for guitar.
Question about the DSP. Do you have to have a android cell phone or windows PC to program one? I've been afraid to buy one. I have a stupid phone because I detest a certain dictatorship where all smart phones are made so much. My domestic assembled PC op system is lubuntu 14 which is only used by poor people so it is never hacked.
Does your amp have phantom power? My voice is too soft even for autoharp, I'm using a 1" diaphragm stellar labs condensor mike for both voice & instrument.
I have an 840 wh 48 v battery on the bike but at this point my $30 amp is 120 vac. MMA875t with 2 input cards. Will have to modify the amp to use some DC source besides an inverter. Internally it is +-40 v .
A picture or plan of the speaker would be nice. I'm using a visiton 6.5" whizzer cone driver in an 8"x8"x14" amazon cardboard box with the end cut out. 1" hole in other end for bass reflex. Of course I don't need 60 hz for guitar.
Question about the DSP. Do you have to have a android cell phone or windows PC to program one? I've been afraid to buy one. I have a stupid phone because I detest a certain dictatorship where all smart phones are made so much. My domestic assembled PC op system is lubuntu 14 which is only used by poor people so it is never hacked.
Last edited:
Many of your specifications make me think of the Soundboks, which is a 2 x 10" cabinet, that's made of 9 mm Baltic birch (7-ply, quality B/BB). This is the main thing I would change in your current plan, as I personally do not find the lower weight of Poplar to "outweigh" the benefits of Baltic. I also do not use battens, in any of my 9 mm builds and have never missed them.
I'm currently also building a backpack (similar dimensions, battery pack, amplifier and processing) that looks more like your alternative approach. Aimed at low bass performance with decent efficiency. Consisting of a 10" 6th order band pass (mono 30 - 80 Hz), 2 x 6" 6th order BP kicks (mono 80 - 200 Hz) and 2 x 4" (or smaller) full range drivers (stereo 200 Hz and up), all with active processing.
The thought behind it is that 200 Hz and below is where all the energy and excursion needs in music are, so in your case you could use a single 12" in a BR or 6th order BP. You can then use 2 full range drivers designed towards efficiency in a small enclosure, as excursion needs are low above 200 Hz, it also means you avoid the need of passive filters. You can aim at a flat response for faithful reproduction and when you want a 'party' simply boost the bass cabinet ~ 6dB. The full range drivers can be mounted in a separate cabinet, so they can be somewhat elevated to increase the 'reach' of the system but need to be relatively close to avoid sound separation between the bass and top cabinet.
I think your right that at 45 liter a Cubo doesn't have any real advantage over a BR. Most Cubo's that do are 64 liters or larger (external cabinet volume).
I'm currently also building a backpack (similar dimensions, battery pack, amplifier and processing) that looks more like your alternative approach. Aimed at low bass performance with decent efficiency. Consisting of a 10" 6th order band pass (mono 30 - 80 Hz), 2 x 6" 6th order BP kicks (mono 80 - 200 Hz) and 2 x 4" (or smaller) full range drivers (stereo 200 Hz and up), all with active processing.
The thought behind it is that 200 Hz and below is where all the energy and excursion needs in music are, so in your case you could use a single 12" in a BR or 6th order BP. You can then use 2 full range drivers designed towards efficiency in a small enclosure, as excursion needs are low above 200 Hz, it also means you avoid the need of passive filters. You can aim at a flat response for faithful reproduction and when you want a 'party' simply boost the bass cabinet ~ 6dB. The full range drivers can be mounted in a separate cabinet, so they can be somewhat elevated to increase the 'reach' of the system but need to be relatively close to avoid sound separation between the bass and top cabinet.
I think your right that at 45 liter a Cubo doesn't have any real advantage over a BR. Most Cubo's that do are 64 liters or larger (external cabinet volume).
@weltersys
Good choice of comparison. I had simulated the 10 in the range previously, but it seems on rechecking that I entered some TS wrong.
Despite the slightly higher initial sensitivity, the 10 inch does have superior LF performance (+2db at fb!). At max output the excursion limits can start to kick in below 50hz at 280w, but I’m not overly worried about that - given the usage and the relatively small amount out of the gap.
I guess the easiest way to compare the two is stiffer vs. looser. 0.3 vs 0.38 qts and 18 vs 12 bl. In these scenarios I tend to gravitate towards tighter sounding.. But I’ll have to sleep on it.. 600g lighter is a nice plus.
In the sims, first is 1w, second is 280w. Green is 10 inch, orange is 12 inch.
@indianajo
I think I used the phrase ‘live music scene’ loosely, we aren’t creators of music - more just replicators of it! Hence no real need for a mic input. (Results would not be pleasant).
Nice to hear your setup - it sounds as if it shouldn’t be too hard to convert to DC all the way through? Then again, with a battery that size, maybe you aren’t too worried!
I would love to have a picture of the current design, but thanks to the infinite wisdom of Win10, I am between CAD systems at the moment.
There is only one integrated DSP which I know of, where you don’t need a computer for the crossover control. Otherwise, you have to unfortunately fall within your corporate jurisdiction of choice
2.1 Amplifier with 100W+50W *2 for DIY Audio-Arylic.com
– arylic
@kipman725
For this one, I am keen to keep it backpack. Sacktrucks won’t be able to go where we’re going! I’m pretty used to carrying packs - so no worries there.
I was trying to originally keep it as two opposing push push 10s for the benefits of force cancellation, running in a 2.5 configuration. However I haven’t managed to find any that gave me a major benefit over the single 12 for the weight increase. Maybe I should keep searching! A bonus with two drivers is that you can run them both at 4r for double the power input, or 8r and reap the efficiency benefits.
I used to have a similar system to the one you propose with two fane 10-300s and a CD140. Great, but the whole thing weighed 20Kg+ and caught fire due to a self-made lipo pack.
Good choice of comparison. I had simulated the 10 in the range previously, but it seems on rechecking that I entered some TS wrong.
Despite the slightly higher initial sensitivity, the 10 inch does have superior LF performance (+2db at fb!). At max output the excursion limits can start to kick in below 50hz at 280w, but I’m not overly worried about that - given the usage and the relatively small amount out of the gap.
I guess the easiest way to compare the two is stiffer vs. looser. 0.3 vs 0.38 qts and 18 vs 12 bl. In these scenarios I tend to gravitate towards tighter sounding.. But I’ll have to sleep on it.. 600g lighter is a nice plus.
In the sims, first is 1w, second is 280w. Green is 10 inch, orange is 12 inch.
@indianajo
I think I used the phrase ‘live music scene’ loosely, we aren’t creators of music - more just replicators of it! Hence no real need for a mic input. (Results would not be pleasant).
Nice to hear your setup - it sounds as if it shouldn’t be too hard to convert to DC all the way through? Then again, with a battery that size, maybe you aren’t too worried!
I would love to have a picture of the current design, but thanks to the infinite wisdom of Win10, I am between CAD systems at the moment.
There is only one integrated DSP which I know of, where you don’t need a computer for the crossover control. Otherwise, you have to unfortunately fall within your corporate jurisdiction of choice
2.1 Amplifier with 100W+50W *2 for DIY Audio-Arylic.com
– arylic
@kipman725
For this one, I am keen to keep it backpack. Sacktrucks won’t be able to go where we’re going! I’m pretty used to carrying packs - so no worries there.
I was trying to originally keep it as two opposing push push 10s for the benefits of force cancellation, running in a 2.5 configuration. However I haven’t managed to find any that gave me a major benefit over the single 12 for the weight increase. Maybe I should keep searching! A bonus with two drivers is that you can run them both at 4r for double the power input, or 8r and reap the efficiency benefits.
I used to have a similar system to the one you propose with two fane 10-300s and a CD140. Great, but the whole thing weighed 20Kg+ and caught fire due to a self-made lipo pack.
Attachments
@rademakers
Yeah, I’m aware I’m heading into soundboks territory. Main differences is that I’m at 0.65x the weight and volume (15>10kg and 90>60l) . I’m happy to sacrifice overall SPL (by quite a lot in comparison), but not the bass extension. Also happy to throw more power at it (sacrificing runtime) and cheat a bit with psychoacoustics.
Keeping a hard limit of 10Kg (aiming for 9kg), means that the portability aspect should exceed that of the soundboks
Why do you feel the birch is still a better option? From a strength point of view, delamination or… ? Also, I mean battens at the corners to increase glue area - I assume you mean the same? I guess if I go the PU glue route then I can delete them and save a bit of effort and mass.
Do you have any links to the 10” you’re considering? I wholeheartedly agree with your energy / excursion comment. A separate mid top section is something I’ve entertained, if it can be kept simple and light. I have never been convinced that a BP6 sounds tight enough running above 100Hz, but I’m keen to be proved otherwise. Something like a high efficiency & light 6” coax driver (120-20k) above the 10” BP6 (50-120hz) could be a neat solution.
Yeah, I’m aware I’m heading into soundboks territory. Main differences is that I’m at 0.65x the weight and volume (15>10kg and 90>60l) . I’m happy to sacrifice overall SPL (by quite a lot in comparison), but not the bass extension. Also happy to throw more power at it (sacrificing runtime) and cheat a bit with psychoacoustics.
Keeping a hard limit of 10Kg (aiming for 9kg), means that the portability aspect should exceed that of the soundboks
Why do you feel the birch is still a better option? From a strength point of view, delamination or… ? Also, I mean battens at the corners to increase glue area - I assume you mean the same? I guess if I go the PU glue route then I can delete them and save a bit of effort and mass.
Do you have any links to the 10” you’re considering? I wholeheartedly agree with your energy / excursion comment. A separate mid top section is something I’ve entertained, if it can be kept simple and light. I have never been convinced that a BP6 sounds tight enough running above 100Hz, but I’m keen to be proved otherwise. Something like a high efficiency & light 6” coax driver (120-20k) above the 10” BP6 (50-120hz) could be a neat solution.
Going with a pair of the B&C10CL51 would equal the weight of the single B&C 12CL64, but gain sensitivity (and output) above Fb, around 123dB without exceeding Xmax/Xvar. If you are planning+12dB of gain added around 60Hz, "stiffer vs. looser" pretty much goes out the window, or more accurately stated, out the port
.While I would not argue that Poplar is better than Baltic Birch, with a small, well braced cabinet, the difference in SPL is probably less than 1/4 dB in the pass band, but the difference in weight is over 1dB
Art
aha I missed the full days hike part. I do lots of climbing (or used to before the indefinite confinement) so am used to overly heavy bags. It will defiantly be more fun the lighter you can get it.
I'm working on a high power (8*500W 4 ohm) battery capable DSP amp at the moment. For that I'm going to use a Analog devices sigma DSP, they have a quite a few psycho acoustic and variable frequency response algorithms that could enhance the bass: Dynamic Bass Boost [Analog Devices Wiki] Its going to take me a while to do all the development on this amp but I have attached a picture of one of the boards that make it up (16 of these to make 8 channels).
I wouldn't think BP6 would be worthwhile over reflex as enclosure size will go up and the efficiency/output boost will be in the region where the speaker has more output (above the LF corner).
Popular ply has been used in Soundgear Orbit speakers to reduce the normal 22Kg weight to 16kg so its defiantly worthwhile. However a very tough polyurea coating was applied to increase the impact resistance.
*Here is a link to my current portable system (that I'm trying to improve): Higher voltage? - Speakerplans.com Forums - Page 1
I'm working on a high power (8*500W 4 ohm) battery capable DSP amp at the moment. For that I'm going to use a Analog devices sigma DSP, they have a quite a few psycho acoustic and variable frequency response algorithms that could enhance the bass: Dynamic Bass Boost [Analog Devices Wiki] Its going to take me a while to do all the development on this amp but I have attached a picture of one of the boards that make it up (16 of these to make 8 channels).
I wouldn't think BP6 would be worthwhile over reflex as enclosure size will go up and the efficiency/output boost will be in the region where the speaker has more output (above the LF corner).
Popular ply has been used in Soundgear Orbit speakers to reduce the normal 22Kg weight to 16kg so its defiantly worthwhile. However a very tough polyurea coating was applied to increase the impact resistance.
*Here is a link to my current portable system (that I'm trying to improve): Higher voltage? - Speakerplans.com Forums - Page 1
Attachments
Last edited:
When either using normal (I think it's PVA) wood glue or polyurethane (a slightly foaming PU-tix), if done well, the bond will be stronger than the wood itself (tested many times). Plywood however can de-laminate, where the top laminate comes off reasonably easy. One way to prevent this is by using 45 degree angled cuts at corners, this also increases glue area by roughly 1.4 times.
I'm talking about the same battens
Baltic birch is more durable than poplar, more scratch resistant (polar dents easily) and stronger around the corners.
I once as a test made a PA bass horn cabinet out of 18 mm, 7-ply poplar, in hindsight I would rather have made it from 15 mm, 11-ply Baltic birch. That was mostly stiffness related, stiffness increases with thickness to the 3rd power, so the 18 mm did have the advantage over the 15 mm. I guess the Young's modulus of Baltic is thát much higher then Poplar (couldn't find any numbers on it, although I know they're out there).
Also whether you use Poplar or Baltic, the Young's modulus is higher alongside the grain, something you can factor into your design.
The 6th order BP is similar to Cubo Kick which is solely used in the 80 - 250 Hz frequency range.
I'm talking about the same battens
Baltic birch is more durable than poplar, more scratch resistant (polar dents easily) and stronger around the corners.
I once as a test made a PA bass horn cabinet out of 18 mm, 7-ply poplar, in hindsight I would rather have made it from 15 mm, 11-ply Baltic birch. That was mostly stiffness related, stiffness increases with thickness to the 3rd power, so the 18 mm did have the advantage over the 15 mm. I guess the Young's modulus of Baltic is thát much higher then Poplar (couldn't find any numbers on it, although I know they're out there).
Also whether you use Poplar or Baltic, the Young's modulus is higher alongside the grain, something you can factor into your design.
The 6th order BP is similar to Cubo Kick which is solely used in the 80 - 250 Hz frequency range.
@weltersys
Very true about the pair of 10”s. I have done a sim of them all (attached).
A pair could also be push-push opposing in a 2.5 config and directly coupled too.. Lovely opposing forces...
Taking the extra power available to a pair (560w) shows a clearer gain over all the other options again. I need to check battery life impact however - but the headroom may be nice.
Although I am slightly confused why xmax and xvar are the same in the 10”. Wouldn’t want to be hitting some hard limit if that’s what B&C are inferring.
You mention that the +12dB gain invalidates the lower qts of the 12 - can you explain how this is the case?
Very true about the pair of 10”s. I have done a sim of them all (attached).
A pair could also be push-push opposing in a 2.5 config and directly coupled too.. Lovely opposing forces...
Taking the extra power available to a pair (560w) shows a clearer gain over all the other options again. I need to check battery life impact however - but the headroom may be nice.
Although I am slightly confused why xmax and xvar are the same in the 10”. Wouldn’t want to be hitting some hard limit if that’s what B&C are inferring.
You mention that the +12dB gain invalidates the lower qts of the 12 - can you explain how this is the case?
@kipman725
I’m used to slugging bouldering pads around myself - so used enough to really awkward sized ‘backpacks’!
Amp sounds pretty beastly, I guess that is for a slightly more serious (professional?) system? Yeah - I’m aware of the sigma studio library, had a good play with them before and it seems a good match. Will have to be a tossup of how much psychoacoustics I can get away with, without detriment to the sound.
I live in hope that a BP6 or alternative design will come to the forefront. Maybe I’m just trying to make my life harder.
Nice setup you have there - I saw that on my last visit to SP. Glad to hear that commercial brands consider poplar too.
I’m used to slugging bouldering pads around myself - so used enough to really awkward sized ‘backpacks’!
Amp sounds pretty beastly, I guess that is for a slightly more serious (professional?) system? Yeah - I’m aware of the sigma studio library, had a good play with them before and it seems a good match. Will have to be a tossup of how much psychoacoustics I can get away with, without detriment to the sound.
I live in hope that a BP6 or alternative design will come to the forefront. Maybe I’m just trying to make my life harder.
Nice setup you have there - I saw that on my last visit to SP. Glad to hear that commercial brands consider poplar too.
@rademakers
True about the 45deg angles. I tend to avoid those mitres as in my experience it makes clamping together a slippery kind of hell. Also, you invalidate the mitre as soon as you put any kind of rad or chamfer on the edge.
With kit that I take out of the house, I almost encourage dents and scratches. The more they have, the better of a life it’s lived!
Aware of the impact of thickness on stiffness (mech eng by trade), but from the FEM I’ve done for this particular cabinet, with the same mass of material, you can easily exceed the stiffness through a thinner skin and strategic bracing.
And yes - YM of poplar ply doesn’t seem to exist. I instead took YM of the woods and inferred its sheet thickness as a ratio of the birches raw to sheet anisotropic YM. The way I see it there’s enough variation in these materials for this to be enough.
Never knowingly heard a cubo kick, but it seems to be more of a ported horn (with unfortunate cone loading)? Where the upper register is a through the short horn at front as opposed to a resonant duct.
True about the 45deg angles. I tend to avoid those mitres as in my experience it makes clamping together a slippery kind of hell. Also, you invalidate the mitre as soon as you put any kind of rad or chamfer on the edge.
With kit that I take out of the house, I almost encourage dents and scratches. The more they have, the better of a life it’s lived!
Aware of the impact of thickness on stiffness (mech eng by trade), but from the FEM I’ve done for this particular cabinet, with the same mass of material, you can easily exceed the stiffness through a thinner skin and strategic bracing.
And yes - YM of poplar ply doesn’t seem to exist. I instead took YM of the woods and inferred its sheet thickness as a ratio of the birches raw to sheet anisotropic YM. The way I see it there’s enough variation in these materials for this to be enough.
Never knowingly heard a cubo kick, but it seems to be more of a ported horn (with unfortunate cone loading)? Where the upper register is a through the short horn at front as opposed to a resonant duct.
For B&C xmax is a geometry measurement using gap size and coil overhang, this dosen't take into account fringe field from the gap or suspension compliance limits. While xvar is the limit given by a Kipple system so is an actual measurement of the usable excursion before distortion sets in. Xlim is the value which the driver if taken to will be damaged but most B&C speakers are designed to run out of motor force before getting close to that. Sometimes Xvar is more than xmax due to fringe field from the motor and sometimes its less than xmax because the suspension is non linear before reaching the limits of the motor system. For design use Xvar.
Amp is for exactly this type of use and a bit bigger systems (and also home hi-fi when mains powered) just quite a bit of development to go until I have a 'product'. E.G I'm using the IR4301 in ways that should be OK but where never intended so I have to build test boards just for the amp bit before I can go to the final design.
When working out power consumption you might be significantly overestimating if your assuming your amps are driving resistors. The actual drivers and boxes will have |Z|>Re in the frequency range with the most average power due to music and also have significant complex impedance which will cause imaginary power flow from the amplifier that will be returned back to the amplifiers power rails rather than been dissipated if you are using a class-D amp. This is an advantage also to BP6 over reflex as instead of 2 impedance peaks in the bass range you get 3 so your power consumption will go down even without the voltage sensitivity increasing.
Amp is for exactly this type of use and a bit bigger systems (and also home hi-fi when mains powered) just quite a bit of development to go until I have a 'product'. E.G I'm using the IR4301 in ways that should be OK but where never intended so I have to build test boards just for the amp bit before I can go to the final design.
When working out power consumption you might be significantly overestimating if your assuming your amps are driving resistors. The actual drivers and boxes will have |Z|>Re in the frequency range with the most average power due to music and also have significant complex impedance which will cause imaginary power flow from the amplifier that will be returned back to the amplifiers power rails rather than been dissipated if you are using a class-D amp. This is an advantage also to BP6 over reflex as instead of 2 impedance peaks in the bass range you get 3 so your power consumption will go down even without the voltage sensitivity increasing.
I used to do that too, until I learned the 'tape method', it's so easy now (no clamps. no screws, no brad/ nails, just tape).
Traditional 6th order BP wouldn't be my first bet when it comes to obtaining a higher crossover. However, tapped horns can be seen as a less traditional series tuned 6th order BP. If you mount those 2 x 10" push-push in a cavity, it also turns your (4th order) reflex into a 6th order parallel BP. Shaping the cavity like Cubo Kick improves the phase response/ group delay allowing a higher crossover (and more output higher up). That unfortunate loading minimizes the offset of the driver in favor of a higher crossover, enough have been build that I wouldn't worry about other misfortunes.
Kipman725 explained Xmax and Xvar in post #15. "Hard limit" would be Xlim or Xmech, which on the B&C10CL51 is around 12mm if I remember correctly- the surround being the limit. The coil will probably burn before Xlim, it is physically quite hard to push the surround to the limit, and the motor force (Bl) is pretty well gone by that excursion.
The lower Qts of the 12CL64 compared to the 10CL51 wouldn't be "invalidated" with a 12dB gain, but whether the transient response difference between the drivers attributable to Qts with that much boost around Fb would be noticed more than the level increase offered by the 10CL51 is something to consider.
If not for weight and output, the decision would be easier..
@kipman725
Thanks for the concise explanation re Xmax/var. I thought that Xvar was Xmax+%age until a given distortion figure, a separate measurement makes much more sense.
I’m currently using a 1/6 rated unclipped RMS power as according to the TI data sheets plus idle and DCDC boost losses as a multiplier where used.
Do you have a method that calculates a more accurate loss, using the impedance peaks? Perhaps using a mean value of the amplifier load power (VA) across a target bandwidth in WINISD?
In the attached data, in the 60-100hz range then this would be seen more as 300W power? Given that I am placing more emphasis on the 60Hz LF 'corner' perhaps this would rise closer to 460W. Still, a good amount lower than the 560W currently in the calculations.
Thanks for the concise explanation re Xmax/var. I thought that Xvar was Xmax+%age until a given distortion figure, a separate measurement makes much more sense.
I’m currently using a 1/6 rated unclipped RMS power as according to the TI data sheets plus idle and DCDC boost losses as a multiplier where used.
Do you have a method that calculates a more accurate loss, using the impedance peaks? Perhaps using a mean value of the amplifier load power (VA) across a target bandwidth in WINISD?
In the attached data, in the 60-100hz range then this would be seen more as 300W power? Given that I am placing more emphasis on the 60Hz LF 'corner' perhaps this would rise closer to 460W. Still, a good amount lower than the 560W currently in the calculations.
Attachments
Last edited:
@weltersys
Cheers again for the clarification. I have no worry of breaking this driver, unless fed with an obscene amount of power within xmax, the audible distress of passing over xmax/var is usually enough warning!
So, the transient response would suffer due to the long decay time at the port frequency and the over-abundance of energy at this point with poor damping?
In which case, if I keep the gain at Fb below a certain value then the advantages of a higher Qts woofer will be able to be heard? Would shifting Fb out of this range or introducing a small notch cut at Fb help?
If I understand your last sentence correctly, do you mean for maximum SPL at depth then the 2x10 would be superior, but if I am after transient response (and am sensible with EQ) then 1x12 would be best?
Cheers again for the clarification. I have no worry of breaking this driver, unless fed with an obscene amount of power within xmax, the audible distress of passing over xmax/var is usually enough warning!
So, the transient response would suffer due to the long decay time at the port frequency and the over-abundance of energy at this point with poor damping?
In which case, if I keep the gain at Fb below a certain value then the advantages of a higher Qts woofer will be able to be heard? Would shifting Fb out of this range or introducing a small notch cut at Fb help?
If I understand your last sentence correctly, do you mean for maximum SPL at depth then the 2x10 would be superior, but if I am after transient response (and am sensible with EQ) then 1x12 would be best?