cab/amp incompatability?

[blackmail man]

so.
i got myself one of those tech21 landmark 300 heads.
great sounding amp but ive been having serious issues running it with my fender cabs (115pro & 210pro)

whenever i get to gigging levels, the thing really starts losing composure and makes this loud "crack" on top of every loud note. made especially worse by a bass with a bit of punch.

so, ive had the head checked by my local tech who told me it was running well within spec and he had no probs with his 18 EV at pretty drastic volume. i ran the head through a warwick 410 and had no probs.

now this only leaves the cabs to be at fault. but i did a gig with my irish punk band (loud drummer, loud stage level) and ran my cabs with an ampeg svt5pro no probs at all. confused...

i like the sound of this setup (before the clipping sets in) so i dont really wanna change anything.

anyone else had this issue before?

 

[Pilgrim]

What's the power rating and impedence range of your head - and what is the power rating and impedence of the cab?

Chances are you have a mismatch, or are either underpowering or overpowering the cab. I'm wondering if the cabs are low sensitivity and you're clipping because your head can't power them adequately for performance volume - but I don't know the head, so I have no idea what power it generates. I may be completely off-track.

 

[blackmail man]

my head is 300watt at 4ohm min. into my cabs which handle 400watts each and are 8ohm each.

ive thought about the low sensitivity thing, fender dont spec anything.
but i recently ran a warwick profet 3 (similar specs) and had no problem getting good volume and punch out of it.

i should have mentioned this problem happens more through the 210 than through the 115. it actually was clipping badly one day at practice so i unhooked the 210 and just ran the 115 and it was better.

im getting a loan out for a new double bass, so maybe i should top it up and get a new rig. grr..

cheers for the input!

 

[Rune Bivrin]

It's quite possible that the impedance of the two cabs together drops well below 4 ohms, particularly at low frequencies. That could send the amp into current limiting, resulting in crappy sound. You probably need more watts.

 

[high mileage]

How are you connecting the speaker cables? Does the 210 have a horn or tweeter of some sort? 300w @ 4 ohms isn't much power up against a loud drummer either way.

 

[GreyBeard]

Your amp is clipping and if you keep playing at that volume with those speakers you'll probably blow the tweeter. You need more power or more efficient speakers.