Conference mit MeetMe large delay

I set up my asterisk with meetme for using conferenz.
I do not use zaptel hardware so I installed ztdummy.

Conference is now working but very slow. If one person talks, it takes about 4 seconds until the other person can hear something.

I am using Asterisk 1.2. on Suse 9.3 Kernel 2.6.

I am using PII Dual Pentium.

Has anybody a Idee?