Espresso Machine Comparisons
I compared the BDB with two other espresso machines: Gaggia Baby and La Spaziale Vivaldi S1. The dual boiler BES920XL currently retails for $1300, similar in price to several low-end HX machines. The Gaggia Baby is a mid-level single boiler espresso machine with a list price of $600 (street price $350), and is distinguished from entry-level Gaggia models by a three-way solenoid valve. The Spaziale S1 is a fully plumbed, rotary pump, dual boiler, single group commercial machine with a list price of $3000 (street price $2300).
The grinder used in all tests was a Mazzer Robur (doser model). Coffees for testing were generously supplied by Counter Culture Coffee (Apollo, Rustico, and #46) and Bodka (Main Squeeze). Other coffees included Mountain Air African Espresso blend and Metropolis Ethiopian Gelana Abaya SO. Coffees were ground with a bean load in the hopper, and doses were weighed to the nearest 0.1g. WDT was employed to ensure good grinds distribution.
I experimented with a wide range of doses, brew ratios, temperature settings, and shot times on the BDB. For comparison purposes, I used the same grind on different machines, with a "normalized" dose (~18g for 58mm double baskets and ~15g for 53mm double baskets), target brew ratio (67%), and shot times (25-30 seconds).Forty-Six espresso blend by Counter Culture Coffee, pulled on BDB
A bottomless portafilter was used exclusively on the BDB and S1. I do not have a Gaggia BPF, so a spouted portafilter was used on the Baby. The unpressurized (single wall) 58mm BDB double basket was used for all extractions on the BDB and Gaggia, and the 53mm Spaziale double basket was used on S1 extractions.Manipulating extraction parameters
All three machines are capable of extracting an excellent shot of espresso. However, there are obvious differences in usability, consistency, and ability to tweak extraction parameters. As you might expect, the Gaggia comes up short in this comparison test. Other than dose and grind, you can only manipulate shot duration. There is no direct method for manipulating brew temperature, although experienced users may experiment with temperature surfing.
The S1 allows you to adjust brew boiler temperature in 1C increments. The S1V1 controls were designed by a sadistic alien, bent on sapping the will of Earthlings by creating the most confusing user interface possible. (Fortunately this has been improved in the S1V2.) An aftermarket mechanical progressive preinfusion chamber adds E61-style preinfusion. You must open the machine and physically install this aftermarket device, a nontrivial procedure.
The BDB menu system allows easy and intuitive adjustments to brew temperature in 1F increments. You can adjust the duration of preinfusion, and even adjust the amount of preinfusion pressure (as a percentage of full pump pressure).Performance
The Gaggia Baby, although capable of excellent extractions, clearly shows its limitations when compared to the double boiler machines. The small boiler (3.5oz) and lack of brew temperature adjustment resulted in one-dimensional flavor profiles and the least interesting shots. Milk-based espresso beverages are always problematic with single boiler dual use (SBDU) machines, and the Baby is no exception.
The BDB and S1 offer stable brew temperatures, plus the ability to manipulate brew temperature precisely and reproducibly. This translates into a full range of flavors in the cup, and a greater realization of the potential of a given roast. Dual boiler machines generally excel at milk-based espresso beverages, allowing you to pull the shot and froth the milk simultaneously.
Comparison tasting between the BDB and S1 generally resulted in small but discernable differences in the cup. This may be attributed to basket size (58mm vs. 53mm) and shape differences. In general, the BDB extractions showed slightly more sweetness, clarity, and separation of flavors than the S1 pours. The S1 extractions were thicker, richer, with better mouthfeel. Neither was demonstrably superior. Both machines clearly highlighted the varietal characteristics of the coffee.