Graetz Siemens Telefunken

My best loud speaker so far, Telefunken 18x26 oval unit, circa mid 1950, in open back cabinet. Baffle size is 45cm x 25cm.

My initial trial was using Graetz 21x32 unit (Isophon P2132 equiv.) as full range, and I found, though it claims response up to 8kHz, I need to cut higher than 2.5kHz.

Firstly, installed few dollars Foster tweeter, then switched to Siemens 6 Ruf lap 28a, and finally Telefunken 10cm, mostly due to appearance matching to Graetz.

Both 6db/oct, phase inverted.

Inside stuffing.

Closed cell foam on the walls expecting to absorb low frequency reflection, and center wool felt for higher frequency resonance.

Even for open back speaker, these treatment gives noticeable difference.

These two way speakers were really nice, at least until I tried smaller 1826 Telefunken.

Anyway, very low frequency, such as we can feel by our body instead of hearing, cannot be expected from these open backs.

Free liveness is the priority of these system. And on this, full range Telefunken is definitely better than Graetz/Telefunken two way.