Hi,
I wonder what 12" will do 100dB and take 1 KW
at the same time without running out of excursion.
If you like it loud outdoors you've got your work
cutout to do it in the bass into free air, most of
the apparent volume will come from further up,
and multichannel car amplifiers with built in x/o's
seem as good a way to do it as anything else.
rgds, sreten.
I wonder what 12" will do 100dB and take 1 KW
at the same time without running out of excursion.
If you like it loud outdoors you've got your work
cutout to do it in the bass into free air, most of
the apparent volume will come from further up,
and multichannel car amplifiers with built in x/o's
seem as good a way to do it as anything else.
rgds, sreten.
Well, yes, but with a battery management system that monitors and adjusts each cell individually during recharge and discharge.
You can't just take 2 LiFePO4 packs and put those in series either. You need to have a pack for the specified voltage. It's not recommended to run different packs in parallel either but it usually doesn't cause problems except for a very slightly reduced capacity.
No pain, no gain 
...
Having many batteries in series we get the additional criteria to choose a type which is forgiving vs. permanent charging in order to derive balancing simply by permanent charging at moderate rates. This might point to flooded types,
because you can access and maintain each cell seperately in case one of the cells suffers from water depletion. ... ugh, handling water and acid...
Well I am not deriving satisfaction from handling acids. Being an electronics nerd I would go for sealed or valve regulated types and a build balancer, or simply do manual balancing, by paralleling them during charging.
Unfortunately lead battery is not lead battery.
Everybody here agrees that a deep cycle type is required, which indicates
a certain plate construction, but also for deep cycling there are multiple available technologies behind.
My personal preference is usually sealed AGM, not gel.
In my experience AGM are more forgiving vs any kind of electrical stress.
On the other hand Gel is often advertised to be the basically more suited electrolyte for deep cycling - means not only the plates but also the electrolyte seems to influence the cycling robustness. Personally I cannot comment on that.
I guess/hope Nico has some more insight informations for us regarding the preferable versions in case of lead types.
P.S.
All the topics and uncertainties above pushed me to LiFePO4 with BMS for balancing + over charge protection + deep discharge protection + temperature protection.
In the mean time even the prices are coming to a reasonable level, especially when you take into account the life time.
...Having many batteries in series we get the additional criteria to choose a type which is forgiving vs. permanent charging in order to derive balancing simply by permanent charging at moderate rates. This might point to flooded types,
because you can access and maintain each cell seperately in case one of the cells suffers from water depletion. ... ugh, handling water and acid...
Well I am not deriving satisfaction from handling acids. Being an electronics nerd I would go for sealed or valve regulated types and a build balancer, or simply do manual balancing, by paralleling them during charging.
Unfortunately lead battery is not lead battery.
Everybody here agrees that a deep cycle type is required, which indicates
a certain plate construction, but also for deep cycling there are multiple available technologies behind.
My personal preference is usually sealed AGM, not gel.
In my experience AGM are more forgiving vs any kind of electrical stress.
On the other hand Gel is often advertised to be the basically more suited electrolyte for deep cycling - means not only the plates but also the electrolyte seems to influence the cycling robustness. Personally I cannot comment on that.
I guess/hope Nico has some more insight informations for us regarding the preferable versions in case of lead types.
P.S.
All the topics and uncertainties above pushed me to LiFePO4 with BMS for balancing + over charge protection + deep discharge protection + temperature protection.
In the mean time even the prices are coming to a reasonable level, especially when you take into account the life time.
You always have a lot of cells in series.
In lead types 2V per cell.
In LiFePO4 3.2V per cell.
Balancing is always an issue, just some technologies are forgiving vs continuous charging and allow simple balancing by overcharging the entire string...
It is just a question of definition what you call 0V and what -48V or +48V.
Important that you always use the same definition in your entire system!
Very true.
In fact I am limiting my PDX-M12 to 500W, because I am firing a 12" woofer with it. With 500W I am already close to the limitations of excursion when allowing a roll off around 20Hz. And this 12" speaker has just 84db/W @1m and allows up to +/-25mm excursion!
Here some older measurements of the sub cube, which is now in my car.
http://www.diyaudio.com/forums/subwoofers/55880-just-142vpp-20mm-excursion.html
Bass cabinet would be a 12" tapped horn with 18sound 12LW1400, a 4 x 10" reflex would be about the same size and weight, if i sacrificed extension i could get higher sensitivity, and 4 x 10" would be easier to amplify, i will give it some consideration, i would like extension though.
The cabinet will not quite be in free air, though the trailer is off the ground, it is closer to 1/2 space in the bass end. i did consider a tapped horn down firing through the grill in the trailer, to improve coupling to the ground, i might build a prototype.
The cabinet will not quite be in free air, though the trailer is off the ground, it is closer to 1/2 space in the bass end. i did consider a tapped horn down firing through the grill in the trailer, to improve coupling to the ground, i might build a prototype.
If i go for the tapped horn it will only run to ~50Hz, im not looking for 20Hz, ive read many say that excursion in tapped horns is less than simulated, i think it should be ok, at the moment its not looking like i will be able to get 1000W into it anyway. 500-600 from something like that PDX-M12 would be nice though.
Common mistake. Ground placement in 3pi is not the same as 2pi except for very near field.
Please note, the PDX-M12 really can deliver approx. 1200W as on the label.
I am just limiting the input level for the PDX in order to avoid more than 500W, because my sub cannot handle more excursion.
Using batteries in series for a +/- supply will save the ~15% power loss of a DC-DC converter. (no matter what type of batteries are used)
A few posters here have assumed one battery charger for the stack or one charger with the batteries placed in parallel for charging.
Why not have a smaller charger for each battery?
They are isolated and won't care about the other batteries and chargers.
A few posters here have assumed one battery charger for the stack or one charger with the batteries placed in parallel for charging.
Why not have a smaller charger for each battery?
They are isolated and won't care about the other batteries and chargers.
The 18 sound driver is 8 ohms, so would only get ~600W, it seems most of these amps are designed for low impedance use, which makes the 4x10" more tempting, i would like the extension though.
Yeah thats what i was thinking, also saves the cost of buying a dc-dc converter, but as people have pointed out it can cause issues, i think if i went for light weight high efficiency high power with LiFePO4 cells it would be the best but cost a lot.
Im thinking a 4 channel class d car amp is the best solution for now, with the potential to upgrade in the future, i was just wondering if i could do better than a vibe slick stereo 4 giving ~150w per 8 ohm driver, but i haven't found any amp boards that will give much more when running on a single voltage supply.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.