Hi guys,

The recent thread Silvia eye and hand cast over Sunbeam EM6910 was a brief overview of the 6910.

I've now posted a detailed comparison at http://www.coffeetamper.com.au/kb/reviews/sunbeam-silvia/

Enjoy (now I can get to bed!)
Greg

Greg

Great review... and I believe a very detailed and accurate comparison of the two machines......



Is there a clear winner? Well that depends on what you want..... Until you get into the $1500+ category - I've always said it's all about compromise.... giving the potential purchaser the maximum "bang per buck" at that price point.... And the purchaser must prioritise what is wanted and choose a machine which satisfies as many of their highest priorities as is possible.

Is there a place for both machines in the 'Snob world- definitely (unlike the 6900- "boat anchor")..... and what is best for one member won't be the best for another - but I have no doubt Greg's review will help you decide which is for you.  

Good one Greg!

Great work Greg  

Very good review...

I think what Greg pointed out and I do agree.. both machines are excellent but are different and really only share the same price bracket...

The Water\espresso temp suprised me.. the Sunbeam temp was too low for my liking... even set at 96deg... TB tech still has some work to do I feel... Boiler over TB for steam will always be I feel....

Agreed ozscott, but the graphs were based on the right grind giving a 'drip to slow stream' pour, and the similarities between the slow and fast pour graphs indicates the temp's inherently lower and a bit bumpier. But the right pour rate will certainly minimise the affect of those variations.

Excellent review, Greg, very thorough as usual, with plenty of detailed  comparisons to allow honest appraisal of the two machines by readers.

-Robusto

None specifically. This was because there's no indication on the Sunbeam when it's heating and when it's not unless you're able to decode the morse code produced by the thermostats, so it didn't seem fair to give the Silvia the advantage of brewing straight after the heating cycle. As I mentioned, once Silvia was stable it would heat for about 50 seconds and then sit idle for about 17 minutes, so the brews would have taken place during the idle period. The Sunbeam cycles much more regularly so I would expect almost identical results regardless of what timing was used.

Send it down to Melbourne Sparky...I'd be more than happy to do it. I have a naked, 6910 and datalogging DMM. This will put to rest all the bs everyone is talking.

I agree with you on the aluminium argument there. I'm currently studying a mech engineering unit called heat transfer and thermodynamics (boy is it hard) and cannot fault the "In fact al is more thermally conductive, and so responds faster than brass to fluctuating temperatures." The heat transfer rate through Al will be greater than in brass. But maybe having the a boiler respond slower to thermal gradients is a good thing(?)   Sort of like a thermal lag that allows the boiler to maintain temperature without much energy needed to keep it there. What it does mean though is that the thermoblock will respond to a re-programmed brew temp a lot faster than a boiler. 2 distinct advantages of each technology.

My premise for this argument is this. We all know the conservation of energy law....basically its the 1st law of thermodynamics and states that "for all adiabatic processes between 2 specified states of a closed system, the net work done is the same regardless of the nature of the closed system and the details of the process". So in essence, the 1st law is a simple energy balance. {Total E in} - {Total E out} = {Change in E total of system}

Aluminium as discussed above is a better conductor of heat. Applying Fourier's Law for conduction we have q" = -k dT/dx.
Thermal conductivity [k{brass}] of Brass is 109 W/mK. Thermal conductivity [k{A}] of Aluminium is 250 W/mK.

Take an instant in time where the rate of change of temperature with respect to the x-direction perpendicular to the direction of heat transfer does not change (i.e. dT/dx = same for Brass and Aluminium), it is easy to see the heat flux {q"} of the Aluminium is much larger than that of Brass. Which prove's Sparky's point that Aluminium has superior thermal characteristics. Actually I really didn't need to go through all that to prove that point. All I needed to do was compare their k values (thermal conductivity values).

But it sets up my next point. I discussed above the 1st law of thermo. If Aluminium is quick to heat and quick to cool compared to brass, it then requires more energy to keep it in thermal equilibrium (heat flux). The advantage of having a brass boiler is that the silvia element doesn't need to work as hard. There is a "thermal lag" or as explained above the heat flux of brass is lower....meaning it takes longer to heat up and longer to cool down. Aluminium is suited to tasks such as being heat sinks where the higher thermal conductivity is desired.

Thermoblocks and boilers are two totally different things, so the two really cannot be compared.

The test with the thermofilter will either confirm or deny Sunbeam is the sh!t or a piece of sh!t and:

• runs at programmed temp
• has good intrashot thermal stability
• has good inter-shot recovery

Would be very interesting to see how the Sunbeam stacks up against a PID'd Silvia in all the above points. My prediction is that it will fail test 1, do well in test 2 and even better in test 3.

Scientific discussion posts have been relocated to This Thread

I wasn't singling out your posts Mark, several posts were discussing highly technical material with regard to the performance of different boiler designs and is, in my opinion, deserved of its own thread...

Cheers,
Mal.

With all due respect, it may not have been 'highly technical' to those who know what they're talking about, but some of the terminology was certainly above my head. While I agree the review was the seed for this discussion, and that this discussion pertains to the review as far as the Silvia and the 6910 use the technologies being discussed, it's still a subject which can easily stand alone. Also given the thread is supposed to be commenting on the review, so much time had been spent on the details of boilers and thermoblocks that someone wanting to raise a different aspect of the review would almost be hijacking the thread by commenting on its original content. I think that's a good test of when it's appropriate to split a thread so I respect Mal's decision to do so.

I'm sure the new thread will have references back to this one so hopefully this thread can continue discussing the review in general and the new one can deal with the specifics of thermodynamics, emissivity of canned worms and radiation densities of eutectic alloys!

Greg

Nice work, however I feel could of been a tad bias as you have a Silvia and have worked on getting the best results out of this machine, I wonder if the outcome may of been closer in the output quality if you had the EM6910 for a longer period.

It comes down to rating the points of difference between the machines. At this price point.

One point that I didnt see mentioned and is important is how long from initial switch (cold) each machine was ready for use. I imagine that with the thermal properties of the brass boiler and the fact that is heating 300ml of water that it would need a much larger element to heat the water and boiler from the initial cold position from cold.

I know when I bring company home and offer a coffee I dont want to have to wait 10 minutes for the boiler to heat to temp before we can even make starting a coffee.

Also as over 50% of people drink milk coffees the lower quality of the output would be well masked by the milk.

As you say horses for course but I think on the review details the EM6910 is the bang for buck machine.

Yeah sorry;

Didnt read it correctly, originally just thought that it was saying that 20minutes was unacceptable heat up time, not that the Silvia took 20minutes.

One would almost need a coffee just waiting for the thing to heat up .lol.

A 20 minute heat up time is totally unacceptable.

So by the time you turn it on let it heat up, grind you coffee (because we dont want it stale so we would only grind when the machine is ready) , heat to steam temp and warm your milk it would be 25 minutes.

Could get a pizza delivered faster.

So working on the premise, if I owned a Silvia I should offer my guest a coffee and pizza because they will arrive about the same time .lol.

Give me a thermoblock machine everytime.  - hahahahaha

Or buy a timer for the power point - set to switch on 45 mins before you expect to return home with friends - machine could be all ready and waiting to go! ( I dont own a Silvia, so assume there are no safety issues doing this if you are late).

Kay

IMHO you can't beat having your machine - any machine that is (including commercials).... on whenever you are about .... and as both kay and Thundergod have sad above - it is dead easy to do.

If you, other members of your household or visitors feel like a great coffee at any time - just walk up to the machine, do the grind, tamp bit (flush if necessary) and make the coffee.

It is just so convenient, and the power consumed isn't that high (even with a two group commercial )

Coffee_guy:

As mentioned in the review's conclusion, the result was very much horses for courses, and the purpose of the pros and cons table was to let each individual see those with which they can decide what suits.

Coffee_guy wrote on Apr 28^th, 2007, 1:19pm:


In your opinion. But not mine. I mainly use my Silvia on the weekends or when we're having friends around. In each case I have at least an hour's notice for the drink serving time so the machine's on well in advance. I'm happy to work with that timeframe for what I consider to be a superior drink. Given it's horses for courses, I'm not saying that's going to suit everyone, but nor is it fair for you to say 20 minutes for warmup is unacceptable for anyone other than yourself. Each individual can consult the pros and cons table and decide for themselves.

There are very few dogmatic absolutes on either machine which apply equally to each person, so we have to be careful not to pick out a single point from either machine and use it to make a blanket statement which purportedly applies to everyone.

Greg

Greg,

Just a minor correction to your excellent article. The RRP of the Sunbeam is $699, not $599 as you stated in a number of places. Sunbeam put the price up $100 when they introduced the newer 6910 model.

Of course there is more room for haggling the Sunbeam down compared with the Silvia, with many CS'ers paying less than $600 for the Sunbeam (therefore has a lower street price).

Confirmation on this Sunbeam web page:
http://www.sunbeam.com.au/products/product_details.cfm?rec_id=660&sec_id=79

I agree with the concept and have been experimenting with a Sunbeam thermoblock and PID control. I've found that the group really does have to be actively heated, but the thermoblock has enough heating cpapbility to bring room temp water up to brew temp. To go a bit easier on it I've used a pre-heating boiler that's under PID control, so I can change the input temp compared to the thermoblock temp.

I'm looking to insert the thermoblock into the brew circuit of a conventional HX machine, using the thermosyphon to heat the group to near brew temperature and use a PID control to give temp settable output from the thermoblock fed directly into the gicleur/3-way. I have all the parts, just not the time at the moment.

Cheers,

Mark.

What about this setup with a Silvia (single boiler) type machine:
Create a water loop by fitting a removable "jacket" around the portafilter with a feedback line that connects to the boiler water inlet. A few non return valves, an insulated flexible hose and a T-type connector on the boiler inlet should do the job.

You would then heat up everything by basically turning on the machine, turning on the pump and letting the water circulate until the boiler light goes out. Then the entire group, portafiter, ... is on the same temperature as the water. Add a PID and you are laughing. The entire heating process shouldn't take more than 5 minutes because all relevant components are now force heated.

Cheers,
Edward

Sounds remarkably similar to an E61! A thermosyphon through the group. But then hey, what did Faema know back in 1961?!?

Just something to consider. Here is my theory. That a temperature offset on a machine where cold water enters the boiler during brewing is not necessarily a bad thing. On a Silvia. the temperature offset means that there is a small increase in temp during a pull. even though the boiler temp is dropping. so you get the group temp increasing while the boiler temp is decreasing and it all kind of balances out. If the boiler were the same temp as the group. by the end of the shot It may be getting a bit cold.

It all depends on how much the boiler temp reduces during a pour of which I have no idea. Im curious those with pids, how low does the boiler get below set point during a pour?

so how much change do you think there would be in the brew water temp during a shot @ the point that it leaves the boiler?

With out getting to far  off track,  for most of us there is a break even point where the;

1: Cost
2: Technical requirements / perceptions etc, and
3: Userbility

do not enhance the enjoyment of the actual outcome.

A mate of mine is an Audiophile, however the actual difference in what I can detect  with my sub $1000 system does not validate the $150K plus for his basic set-up.

As has been said many time before, the Quality of the output is in the perception of the end consumer.

For those who have the time and the drive to finely tune and modify their equipment, half their luck, and if it worthwhile and repeatable. I am happy to give it ago.

However at present I am more than happy with my EM6910 and the ease of use Vs what I watch a mate go through with his Silvia (In particular when making for more that two people at once)...  

It is the Quality of the raw product (beans)  that appears to have the greatest impact on the final product for me and in many ways, is the cheapest item to manage.

OK, not everything, I would still probably still rather the Silvia/Rocky, but not for twice the price of the sunbeam combo.
I'm not trying or asking to be flamed by all the sunbeam loathers or Silvia fans out there, just giving my $0.02.

John.