diff --git a/convolution.cc b/convolution.cc
index f0a9d93..b50410c 100644
--- a/convolution.cc
+++ b/convolution.cc
@@ -368,6 +368,12 @@ int clv_initialize (
 
 	VERBOSE_printf("convoLV2: max-convolution length %d samples (limit %d), period: %d samples\n", max_size, clv->size, buffersize);
 
+    if (out_channnel_cnt == 1){ // running in mono, set to short IR mode
+        max_size = 0x00002048; // no useful info after 20ms for cabs. Set to 40ms.
+    }
+    else{
+        max_size = 0x00100000; // 2 seconds
+    }
 
 	if (clv->convproc->configure (
 				/*in*/  in_channel_cnt,
@@ -375,7 +381,7 @@ int clv_initialize (
 				/*max-convolution length */ max_size,
 				/*quantum*/  buffersize,
 				/*min-part*/ buffersize /* must be >= fragm */,
-				/*max-part*/ buffersize /* Convproc::MAXPART -> stich output every period */
+				/*max-part*/  Convproc::MAXPART
 #if ZITA_CONVOLVER_MAJOR_VERSION == 4
 				, clv->density
 #endif
diff --git a/lv2ttl/convoLV2.ttl.in b/lv2ttl/convoLV2.ttl.in
index 8b57101..2f593cd 100644
--- a/lv2ttl/convoLV2.ttl.in
+++ b/lv2ttl/convoLV2.ttl.in
@@ -37,7 +37,7 @@ clv2:Mono
 	lv2:microVersion 0 ;
 	lv2:minorVersion 4 ;
 	lv2:project <http://gareus.org/oss/lv2/convoLV2> ;
-	lv2:requiredFeature bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
+	lv2:requiredFeature bufsz:fixedBlockLength, bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
 	bufsz:minBlockLength 64 ;
 	bufsz:maxBlockLength 8192 ;
 	lv2:extensionData work:interface ,
@@ -96,7 +96,7 @@ clv2:Stereo
 	lv2:microVersion 0 ;
 	lv2:minorVersion 4 ;
 	lv2:project <http://gareus.org/oss/lv2/convoLV2> ;
-	lv2:requiredFeature bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
+	lv2:requiredFeature bufsz:fixedBlockLength, bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
 	bufsz:minBlockLength 64 ;
 	bufsz:maxBlockLength 8192 ;
 	lv2:extensionData work:interface ,
@@ -171,7 +171,7 @@ clv2:MonoToStereo
 	lv2:microVersion 0 ;
 	lv2:minorVersion 4 ;
 	lv2:project <http://gareus.org/oss/lv2/convoLV2> ;
-	lv2:requiredFeature bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
+	lv2:requiredFeature bufsz:fixedBlockLength, bufsz:boundedBlockLength, urid:map, opts:options, work:schedule;
 	bufsz:minBlockLength 64 ;
 	bufsz:maxBlockLength 8192 ;
 	lv2:extensionData work:interface ,