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A resonance chamber with triple width for the LS1511-type speaker. This is the same type of the "sugar cube" speaker used in model trains by Zimo and ESU. A LS1511-speaker can be ordered at Doehler & Haass and can be used with the currently available decoders from Doehler & Haass, ESU and Zimo.
Most modern decoders can work with two sugar cube speakers connected to the decoder. With this resonance box you cen put them both next to each other. Use of this resonance chamber gives a better representation of bass-sounds than smaller version.
The resonance box can be glued (I personally prefer kristal klear) to the speaker. Make sure you'll have an air-tight seal between the speaker and the resonance box for the best sound.