Why a 4” coiled BTL? Well, because we can. New for 2019 is the first 4” coiled sub in the BTL Series. The BTL4-Ferrite is the latest in the progression of Fi subwoofers geared towards thundering daily drivers. Utilizing a favorite 3 stack ferrite magnet design using US steel cut on our water jet and finish machined on our CNCs, there is plenty of motor force in the FEA derived design for both daily and SPL use. Utilizing a solid pole and a venturi aided pole profile, the forced cooling keeps thermal temperatures under control. A classic 3 stack of ferrite magnets provide the Gauss while 4 Fi designed 10″ heavy progressive spiders keep things under mechanical control. Utilizing a special 144 tinsel count leadwire that is double sewn to the spider pack, there are no losses in power transfer to the coil (available in either standard stitched with terminals or the hybrid stitched with bolted termination.
Working in ported, 4th or 6th order applications the 2019 BTL4-Ferrite Series raises the power handling and thermal performance of a classic line to new levels . As always, the BTL is “Built To Last”.
Overall Diameter 12.500”
Dual 1 and Dual 2 Ohm
Custom Options Explained
P Chamfer: This is a chamfer on the end of the pole, it helps to bring the air down around inside of the motor and helps cool the coil better. It also helps relieve the pressure underneath the dustcap. We recommend at the bare minimum to get this option if you choose this series of woofers.
Hyper Pole: This is an extended version of the standard P Chamfer. It has 1.250” more pole and chamfer resulting in an increased compression ratio for better cooling.
Cooling: Self explanatory, the cooling channels are machined into the inside of the sub to help cool the coil FAR better. But there are some things that you sacrifice. There is less metal inside of the motor so it is a little weaker. If you are looking for a fart/burp only scenario for SPL we suggest that you do NOT get this option. Stick with only the P chamfer. Now if you are looking for a daily sub to beat on and you have less then 2000 watts then this is the option for you. 2000+ watts you need to look into the BTL series.
Flatwind: The flatwire coil option simply helps the power handling of the sub. The coil has more surface area to dissipate heat and will take more power then the regular round wire coil that comes in the ‘stock’ version of the sub. This option will also make the sub tend to be more prone to ‘peaking’. If you are looking to do an SPL install we highly recommend that you use choose the flatwound coil option. In testing it is louder then the regular roundwire coil and takes the thermal abuse much better.
BP: “BP” option which was a machined aluminum compression plug to the pole which helps channel all of the air under the dustcap around the coil for better cooling. To aid with this increased airflow we also added 6 axial cooling channels in the top plate. Along with increased thermal capacity comes the addition of an extra spider and a changed spider pack. All of these features increase power handling from 200-500 Watts depending on the application.
High QTS: This option is for users who intend on using the new Q series woofers in only a sealed enclosure. Low QTS: This option is for users who intend on using the new Q Series woofers in only ported enclosures.
Spider: This option adds an additional spider to the spider pack to help with mechanical power handling and keeping the moving assembly under control.
I Heat Ring: This option is a machined aluminum ring in the gap that lowers the inductance of the voice coil which allows it to play up a little higher in the frequency range and have better overall transient response. Please note that you can NOT select low Qts and the I Heat Ring options together.
Internal Lead: This option is for 8 lead coit per coil, increasing the current flow from coil to terminals.
Inner Heat Sink: Its a machined aluminum ring in the gap that lowers the voice coils inductance (allowing it to play up higher and have a little better overall transient response). It also reduces the volume inside the magnet gap of the motor increasing air speed with the cooling as well as allowing the coil to kick off heat to a more receptive thermal mass rather than magnets.
Daily or SPL: Simply put, if you plan on listening to any type of music you MUST choose the daily option. If it is strictly for a fart/burp scenario then choose the SPL option. The reason we have these options is the gap tolerances between the two are different. The gap in the SPL woofer is much tighter and FAR less forgiving in comparison to the Daily option. The Daily option simply gives the coil more wiggle room inside of the gap to deal with the non-linearity tendancys that you can get into when you are using a sub in a daily driving scenario. Typically SPL applications deal with 1 note and it does not change, therefore we can make the gap much tighter and get all of the motor strength that we can out of it.
Universal: This option gives you the choice to later chance the impedance of your voice coils. You can change from dual 2s to dual 1s and vice versa by reconing them. If you do not choose this option your motor(s) will be optimized per the coil resistance that you have chosen. (Dual 2s will forever be a dual 2 motor, Dual 1 will forever be a Dual 1 motor).
“Fi Terms & Conditions”
These are not mass produced items. Each and every order is built from the ground up. This is not by using pre made parts and bolting/gluing them together, far from. They are machined to exact tolerance for your given application. There is no mass produced magnet sitting on the shelf, your woofer is made for you, when you order. Sure others can produce drivers faster but our manufacturing goes much deeper giving greater control during manufacturing resulting in a ultra high performance regardless of the footprint.
As a result build time is typically 10-14 days. With the distance from USA to the UK this can be anywhere from 14-28 days till you receive your Fi subwoofer.
We can offer a faster service with additional freight charge to express. Typically 7 days. Please contact us about this before ordering.
Refunds, If your custom-built-item has not yet begun to be manufactured you will be charged a 5% processing fee for refunding your payment. If your speaker has begun to be manufactured, or is finished, but has not shipped, you will be charged a 30% refund fee. If the speaker has already shipped, you will be charged the 30% refund fee plus all applicable return shipping costs.
By reading these terms and conditions, you agree to wait upto the allotted 28 day period. If your order exceeds this due to manufacturing delay or part shortage you will be notified in good time and automatically will receive a free T-shirt.
If you have anymore questions do not hesitate in contacting us.