Major obvious difference is the Tempest comes with a stem, that is - the Tempest is a whole device - not just an oven/bowl. I use my TA3 on a Revolve Gen 2 with a Tempest wooden sleeve - so in a way - I use them the same way - as I use my Tempest on the native stem.
So ignoring the
Tempest stem & its features - which are extensive and include things like multiple cooling options, draw resistance options, a spinning mouthpieces that's isolated from the airpath so it doesn't get hot, different sleeves wood, glass, titanium, different colors....
I could keep going but you'll get bored.
The Tempest and TA3 both come with adjustable airflow on the cap; the amount of airflow is different but they both have the same feature.
Starting with the obvious - Size :
The Tempest's heat matrix is about 40x3mm vs the TA3 which is about 70x3mm, while they are similar in size side by side, the TA is far heavier and contains significantly more thermal mass - just from the metal - let alone the heat matrix which is about 40% larger. The Tempest has an additional section at the top that contains the temperature feedback components which really make the Tempest stand out against its competition (we will discuss this later) where as the TA3 uses that same space to house more balls to increase the size of the heat matrix.
When heating the TA3, the sheer size of the thermal mass, helps to create a buffer and this buffer helps to control the speed at which the device heats up and also slows the transfer of heat from the heat source to the balls inside the heater matrix. It takes significantly more calories to heat up the TA3 than it does the Tempest. I use a Blazer Big Boy on the TA3 for 17 seconds to the top 1/3 of the oven and its a reliable ritual. The buffer means that if I screw up and loose count and hit 18 or 19 seconds, I probably wont have added enough heat to the balls in the heat matrix to run the risk of combustion.
The Tempest is much more sensitive. There is less metal in the cap of the Tempest which facilitates quick and efficient transfer of the heat from the heat source directly to the balls that make up the heat matrix. This reduces the calories required to heat up the Tempest compared to the TA however, this also means that the Tempest is much easier to over heat.
Thankfully The Tempest comes with multiple temperature gauges in the form of a visual temperature gauge and click discs that give the user feedback while they heat the device.
In my experience using the Tempest without click discs or a visual indicator for about 5 months, without the click discs and visual gauge you are relying on timing (either using a Inspire wand with a timeout or a stopwatch) and due to the sensitive nature of the Tempest, too much heat in such a small space can cause radiant heat to scorch the top of the bowl.
I was lucky enough to get a new cap with (almost calibrated) click discs and a calibrated visual indicator and since then, the Tempest has really come to life. It became so easy to control with the clicks being calibrated for optimal temperature and the top end temperature allowing you to easily control the heat and via the adjustable airflow sleeve you can increase the density of the vapour.
I'll talk more about the temperature feedback later.
Another important difference lays with the bowl design :
Both the Tempest and the TA3 have an adjustable bowl design, I haven't actually weighed the amount I put in the to compare so I will do that when I finish, but I feel like the TA3 bowl is a little larger (which makes sense) but I don't remember the size exactly,
The Tempest has a slightly isolated bowl, the majority of the bowl doesn't directly connect with the walls of the cap which means there is much less conduction from the cap to the bowl as compared with the TA3. The TA3's bowl is directly connected to the cap and gets significant conduction from the cap to the bowl.
In the Tempest, this results in a convection dominant style vape with top tier flavour, as the partially isolated bowl protects the volatile terps in during the heat up process. The Tempest is built such that heating technique can allow you to add more conduction to the bowl directly from the heat source (torch or induction heater) by heating lower on the bowl than normal. The cap screws onto the bottom of the bowl, so as you use the device over a single heat cycle, the heat slowly balances out over the whole cap causing an increasing amount of conduction from the bottom of the bowl where you screwed on the cap, to the herbs - this helps to finish the bowl without needing to reheat or stir.
The TA3's bowl isn't isolated, the top of the Thermal Accumulators bowl is screwed directly into the bottom of the cap, so as the heat starts to build in the top of the cap - it starts to conduct down onto the bowl. However because of the sheer size of the thermal mass that makes up the TA, the first few draws through the device are delightfully full of flavour with a convection bias; however as the session continues, the conduction roast starts to kick in and the flavour becomes more toasty and the vapour more dense.
This is where the TA3 really stands out for me. The extraction with the TA3's oven is about as complete as in any oven and results in one heat extractions and AVB that often surprises me. The flower sandwiches (BHO/Rosin) almost always come out without any residual stickiness - the extraction capacity of the TA3 is probably far more than the bowl capacity is.
The Tempest more than easily extracts a full bowl of herbs on a single heat cycle, but when I have been using concentrates in the Tempest; in the form of a flower sandwich, sometimes there is some residual stickiness left in the bowl and I will go for another heat. I rarely have to reheat when using herbs or using Rayon and my concentrate of choice.
I feel that the conduction bias in the TA3 continues to increase during the session; I find that it provides a more physical, sedative or "heavy experience" as compared to the Tempest. The Tempest with its more convection bias provides a more stimulating, uplifting, mental experience that's tempered with just enough radiant heat and conduction to "ground" the experience and the effects avoiding some of those jittery experiences that you can get with some herbs.
Back to the temperature Feedback features and why they are important :
The Tempest is a sensitive when heating, there is significantly less metal in the head of the Tempest as compared to the TA3 and that additional mass in the TA3 helps to create a buffer to make it a little easier to heat without over heating it. The Tempest doesn't have this, the minimal metal in the cap means that the heat from the heat source is almost entirely transferred to the balls in the heat matrix. This makes it very easy to overheat the Tempest when you don't have any feedback however the Tempest has multiple temperature feedback features.
NOTE: Phatpiggie has mentioned that there might eventually be a cap for the TA4 with temperature feedback features - but its not a certainty and it would change the way that the TA is heated.
The Tempest has both a pair of click discs and a visual temperature gauge - like a thermometer. These features take the guess work out of heating the Tempest. The Tempest has 2 click discs, the first click is calibrated around 170c and the second click its set to around 210c and the visual gauge has 3 marks and covers a range of 110c-240c.
When using rayon with BHO or a concentrate in the Tempest I usually let the device go to the second click & maybe a little beyond, however when I am using herbs I prefer to stick to just before the second click.
.... you know what I need a break I will come back to this.