Cab advice

[GBH]

Hi all, i hope some of the more technically minded chaps among you could spare the time to go over my cabs specs.
I have a 4x10 cab made by a known british manufacturer,I'm not going to name it yet because I don't wish to potentially prejudice peoples views towards the manufacturer.
The cab itself sounds generally good,deep and punchy,even at reasonable volumes. However at certain points during a gig, it sounds as if the speakers are choking up,no real distortion as such but it's as if the sound kind of strangles. I'm using a Markbass little mark 2, usually with PA support and not at excessive volumes,playing mainly function type stuff.
The cab itself is fitted with celestion BN10 300X drivers. It has 2 100mm diameter,140mm long ports that are rear
mounted and the internal measurements are 570mmx540mmx395mm. I would greatly appreciate any advice regarding possible alteration of the ports,ie longer,shorter,smaller etc or any other suggestions.
Regards
Geoff.

[Mr. Foxen]

Are they the original drivers?

You can experiment with the port tuning a bit but rolling up some stiff card and putting it in the ports to make them telescopic, and lengthen them that way, see if it makes a difference.

[Delberthot]

I'm no expert but possibly putting to much power through the drivers causing the magnets to heat up and affect the sound?

[stevie]

Geoff,

Your cab seems to be tuned to 40Hz, which will help the B string a bit if you have one. If you want to try a higher tuning, take one of the port tubes out. That will tune the box to about 46Hz. I don't think it will make a lot of difference, personally.

Your speakers will handle at least 600 watts cleanly as long as you don't boost the very bottom end.My money's on the amp running out of steam, and I'd suggest you try a bigger amp, if you are can.

[Wil]

Little Mark 2s pack a lot of power, I wouldn't think it would be the amp running out of steam personally. Do you boost your low end a lot?

[stevie]

What impedance is the cab?

[GBH]

Hi guys,thanks for all of your responses. Mr Foxen, they are the original drivers. Wil, I generally boost the bass up to the first line and leave everything else flat although I may cut the high mid a small amount depending on the room. Stevie, the cab is 8ohm. If it is of any relevance I generally use a passive jazz bass.
Cheers
Geoff.

[Wil]

Right, in that case what Stevie said about the head running out of juice could well be the case, as it'll only be putting about 250 watts into it. Have you got the chance to pair it up with another 8ohm cab so your head is running at 500 watts into 4ohms?

[GBH]

Depending on the size of the gig i do have a 1x15 that i use with it and i still have the same problem.

[Wil]

Have you tried just using the 15 to see if you get the issue (to rule out the amp itself)?

Bit of an odd one really.

[stevie]

According to the review in one of the bass mags (the only one that does proper tests, IMO), this amp has a compressor that comes in at 440W into a 4 ohm load. Using the two cabs together will give you a 4-ohm load - and increase the efficiency of your speakers - and should be very loud indeed.

I don't think there's any obvious answer here. I'd try substituting another amp to see if the same thing happens.

Edited May 30, 2010 by stevie

[GBH]

I haven't used the 15 on its own at a gig,i'll have to try it. Thanks for your help,Geoff.