Changing where, and the way the air comes into the firebox is critical.
By coming into the front, you'll find the ash burns down finer than in the rear. This allows you to remove the ash down to 1 inch in the front each morning, and rake ahead the coals and charcoal along with a little ash from the rear. This prevents the need to allow the fire to die to remove ash approximately weekly.
The deep, narrow stoves with the single doors burn the best due to the oxygen flowing down between the logs, mixing with the flammable gas emitting from the heated fuel. So incoming air should be of high velocity, from the front, for the best mix of oxygen.
The flow through the firebox from front to back is interrupted by a baffle, changing direction of flow, which allows more smoke particles to be burned in the stove. So coming in from the rear or sides is not going to feed oxygen to the front where ignition normally takes place first, preheating between logs.
Keeping the air inlet where it needs to be across the front also prevents ash from clogging the inlet into the firebox. A pipe, or pipes coming into the side at front, going across the front with holes or elongations would allow air close to the correct position, but the height also plays an important part getting oxygen to the fuel. It becomes complicated, since stray oxygen molecules touching the surface of the heated wood changes the speed of ignition. Creating flame, or charcoal when deprived of oxygen. The charcoal then has a lower ignition point, later bursting into flame. You would then need valves on the intake air lines, which is going to slow velocity, which you don't want. The pipes should be large, equaling larger than the air intake opening size you have through the doors. (measure this as square inch area) This is explained as resistance you're adding to the venting system below.
The basics of what makes a stove work is the hot rising gasses in the chimney being lighter than air. This creates a low pressure area in the chimney, pipe, and stove. This pressure is measured as draft at the stove collar where pressure is lowest. Atmospheric air pressure then PUSHES into the stove, feeding the fire oxygen. So the chimney creates low pressure, and everything else takes away from it. The chimney cap, spark screen, connector pipe, elbows, tees, variable damper, and the air intake opening (the most resistance in the system). A baffle adds internal resistance inside the firebox, and the venting intake into the stove is going to add more resistance. So the chimney needs to be hotter, air controls more open, flue damper if used more open to get the same mount of air. Getting air from outside the house has the huge advantage of having actual atmospheric pressure at any given time. So mechanical blowers and other factors decreasing the air pressure in the house are eliminated. That is the main advantage of the outside air intake.
A much easier way is simply boring a 3 inch hole through an exterior wall close to the stove. Install a PVC pipe through the hole with an elbow pointing upwards inside, and an elbow pointing downwards outside with a screen over the end. This allows atmospheric air pressure into the structure as the stove or other mechanical fans decrease the air pressure in the home. It will not allow warm indoor air to drop outside, or cold air outside to rise into the pipe. You only get flow when the stove decreases the pressure indoors or another appliance or mechanical blower decreases the air pressure inside. This air intake is needed for propane appliances such as ranges and cooktop, unvented heaters, any clothes dryers, central vacuums, or any other appliances burning fuels exhausted to the outside. An air intake directly into the stove does not do this for other appliances. I called these intakes an "elephant trunk" when I installed them in customers homes that needed oxygen or air pressure getting to an appliance. They do need to be closed off during summer if A/C I used in the home making the air inside cooler than outside air.
Many times I installed these into a utility room housing furnaces, water heaters, or boilers, that require lots of oxygen. It balances the entire home preventing appliances from drawing their intake air from your bedroom, across the entire house to the appliance. Pool heaters are another example in a utility room that require lots of outdoor square inch opening and required by code. Any appliance including the stove is going to allow air pressure outside to infiltrate into any crack or opening it can to equalize the pressure. It is best to have this leakage close to the appliance to prevent cold air drafts moving across the home toward the appliance using the air, than far from the appliance.
If you don't like the idea of allowing cold air into the home, (it's coming in elsewhere, you just can't feel it in one place) You can build an air mixing box that is a box made with galvanized duct (usually hung under floor in basement) with a screened air inlet from outside, and an air inlet from basement. This mixes incoming air with moderated basement air, vented through floor near stove. Another simple solution is a floor drain connected to PVC pipe, through the floor close to stove leading outside with a screened end. Don't be too concerned about the cold air blaring through the floor drain, it is headed into the stove preventing it from moving across the entire home from elsewhere.
The other solution is a Goldilocks stove model that uses the pedestal base as an air intake up through the floor. It would need to be plumbed out to a vent under the home, or basement. One word of caution; ANY outside air intake gets extremely cold in the winter. This condensates any water vapor in the heated area or basement. So a large PVC pipe leading from the stove base outside gets cold, condenses water vapor and drips. I heated a few years with a Goldilocks being my first new Fisher Stove I bought. I had to put a section or rain gutter under 4 inch PVC in my basement to catch the water dripping off it constantly. That shows you how much cold air is moving through that intake pipe, because the air in my basement was considered dry all winter! The intake supplied with Goldilocks was made by Dura-vent and was galvanized 6 inch pipe with screen at the bottom end used under mobile home floor.
A smaller Honey Bear was also produce with removable pedestal for outdoor air intake through floor. Dura-Vent supplied exhaust and intake kits for these stoves as well.
