zin1953 wrote:I'm not arguing, Chris. I think both types of machines are quite capable of producing excellent shots . . .

What Jason said. In fact, that was one of the main points of this thread.

akallio wrote:Out of curiosity: if you would set out to "ambush" Izzo Alex Duetto (with steam boiler on), what would be the sequence that you'd try first? Duetto is a thermosyphon DB, but the design of the thermosyphon loop is better than in some other E61 DB's AFAIK. I have been playing around with my Duetto now and measuring thermal stability in different conditions would be one interesting thing to do.

I think that the best reasonable test would be to run the WBC test series and look at how the machine behaves from very intermittent duty to through full-on, elbows-flyin, coffee-spewing frenzy. The WBC test was intended to tax commercial gear that would see all of these duty cycles. We tested the high-frequency limits of the test - to see if it truly mimicked real life, by getting James Hoffman to brew real espresso shots at the fastest rate specced by the test (an earlier version that contains the same test frequency, but less well though out analysis is on the Bench section of the forums). He managed to keep up just fine and thought that the specified frequency was reasonable enuff.

Now some have argued that the test isn't relevant for home use, but I disagree. The idea of the test isn't to talk trash about machines, but to learn how the machine behaves and what can be done to optimize the behavior. Once we have a first set of data showing how the temperature changes with duty cycle, we can try corrections in our technique to compensate for machine inadequacies. We can then test the correction by running the WBC series again, implementing the correction where appropriate. Often, a simple compensation flush is enough, but sometimes we will find that there is a fatal flaw that prohibits optimal performance beyond certain brew frequency ranges. An example of this might be a hypothetical double boiler machine with an e-61 group that features brew boiler feedwater preheating. We may find that at very high duty cycles the brewing temperature climbs enough so that the quality of the shots is affected, while the repeatability at lower brewing frequencies is very good. We'll then have to decide which is more important for our style of use, and if the machine is suitable. For the example given, if we value the ability to make walkup shots with minimal fuss, and don't often brew many shots in a row, the deficiency of the machine has little consequence. But if we intend to use the machine for parties and catering, we'll know that the machine has limitations

Now since I'm writing and ignoring my job, I'm gonna try to straighten out something:

I read lots of comments about engineer types trying to measure this and analyze that, vs tasting coffee. Usually the tone is that it's the coffee stupid. Well it ought to be the coffee stupid, but if your game is really on, I think it's entirely reasonable to examine all of the aspects of your game and try to understand and improve on them. Work towards understanding the process and getting the process more repeatable is all about making things better, so I often find the discussions of extraction and examination of technique to be very useful. On the other hand, if you're sitting there measuring your machine and you're screwing up making coffee, then you have it exactly backwards.

gscace wrote:Now some have argued that the test isn't relevant for home use, but I disagree. The idea of the test isn't to talk trash about machines, but to learn how the machine behaves and what can be done to optimize the behavior.

Exactly, it's like a test pilot working up the performance envelope for a new airplane. Unless you know what the limits are, you're groping in the dark.

gscace wrote:I read lots of comments about engineer types trying to measure this and analyze that, vs tasting coffee.

Without those engineer types, there are no stable espresso machines. And in the home barista environment, the hobbyists are helping to push the envelope and see what performance can be obtained from home machines. And for those familier with process flow charts, tasting the coffee is a decision point, where you either go back and adjust one of the brew parameters (dose, temp, tamp, etc.) or exit because you nailed it.

gscace wrote:I think that the best reasonable test would be to run the WBC test series and look at how the machine behaves from very intermittent duty to through full-on, elbows-flyin, coffee-spewing frenzy... Now some have argued that the test isn't relevant for home use, but I disagree.

No question: it is the best way to get at the thermal properties of a machine, and learn how to work it. But it is not the best test for how well it will perform either at home or in barista competition, since it is too strict. Certainly, anything that is stable in this test will be stable at home or in competition; but machines that do poorly in the test could still be very good at home and in competition. There is a bit of the "I need a Hummer in case it rains" psychology to these tests.

I read lots of comments about engineer types trying to measure this and analyze that, vs tasting coffee.

Again no argument. But ... The taste comes first, then the explanations. This is the order I follow in reviews. For instance, I knew the Elektra Semi made great shots before I did the temperature and pressure testing. The tests showed a machine with very imprecise temperature and pressure control. All that means is that I don't know why the Elektra makes good shots. The pair of test bench, PIDed and OPVed Silvias I had were extremely precise on pressure and temperature. But they produced hopelessly foggy shots that couldn't distinguish a lamp post from a barn at 10 yards.

BTW, my experience with the Silvias gives a "comfortable for engineers" methodology for taste testing espresso machines. Use three identical machines or groups. Make espresso blend A on two groups and blend B on the third. A & B should be very unalike. Then make blend A on 2 groups and 50/50 A & B on the third. Then blend A again on 2 groups and 75% A and 25% B on the third. The machine that allows testers to make the finest discriminations is making the best tasting espresso.

Obviously, a test like this does not replace verifying that the machines make proper espresso. It simply proposes to operationalize the concept of high quality shots as shots with the clarity to distinguish the smallest differences.

malachi wrote:Out of curiosity... how many of you are NOT arguing that your own personal machine type (DB, HX) is superior?

I have one of each. Each has it's strengths and weakness. Both are a reasonable compromise for their intended purpose and location. Neither is perfect.

Ian, just out curiosity (as an imminent buyer), if you had to choose between your VBM's, which one would stay, and why?

That's an impossible choice without some qualifiers.

At home, I futz more with the espresso than at the office so there I like the extra flexibility of adjusting the boiler temperature via the [user installed] PID and then the brew temperature by flushing as needed. The extra steaming and throughput capability of the HX is essential for dinner parties.

In the office, I just want to walk up and pull a shot. I don't think I'd like pulling a long cooling flush there, so I'd probably keep the DB. I like the DB brew boiler only mode. Saves a bit on electricity and A/C and reduces the number of descales on the steam boiler.

Bottom line : It's 50.5% for one vs 49.5% for the other. I'm just never sure which is ahead

gscace wrote:Examples of such cobbling is the use of thermosyphon groups in double boiler machines. There really is no good reason for this. The thermosyphon group works properly when there is a large temperature difference between the boiler and the group. The double boiler idea is that the brew water should be very close to brewing temperature

Certainly correct me if I'm wrong...but my Brewtus III DB has the thermosyphon supplying the water to the brew boiler. To me this is an excellent engineering concept to minimize the "shock" of cold plumbed-in water entering the brew boiler and the PID going into a frenzy trying to keep up with a series of shots.

danetrainer wrote:Certainly correct me if I'm wrong...but my Brewtus III DB has the thermosyphon supplying the water to the brew boiler. To me this is an excellent engineering concept to minimize the "shock" of cold plumbed-in water entering the brew boiler and the PID going into a frenzy trying to keep up with a series of shots.

Dane, the problem with that, and what Greg eluded to earlier, is that after a succession of shots, the temperature of the brew boiler can actually increase as the incoming HX for brew water over heats the inbound "fresh" water, thus increasing the brew temp.

In a typical home environment, this may not, and probably will not ever happen.

gscace wrote:An example of this might be a hypothetical double boiler machine with an e-61 group that features brew boiler feedwater preheating. We may find that at very high duty cycles the brewing temperature climbs enough so that the quality of the shots is affected, while the repeatability at lower brewing frequencies is very good. We'll then have to decide which is more important for our style of use, and if the machine is suitable. For the example given, if we value the ability to make walkup shots with minimal fuss, and don't often brew many shots in a row, the deficiency of the machine has little consequence. But if we intend to use the machine for parties and catering, we'll know that the machine has limitations