Speaker Upgrade - 2x15 Marshall

[Yokobono]

Hi!

Was wondering if anyone could help me. My current guitar rig includes a bass rig to make up for a lack of low end. The amp I have is a fender super bassman (the newish 300w version). I've been running this with an old 2x15 marshall cabinet (I believe it to be a 1551 with 2x100 watt celestions in it).

I guess it was only a matter of time before said amp & fuzz boxes has killed the speakers in the cabinet. I really like how the cab looks and sounded, so I was thinking that - instead of looking for another cabinet - maybe I could put some bigger wattage speakers in this cabinet?

I was just going to order some 300watt celestions, but a friend advised me to ask here. Also I'm unaware of things like 'xmax' measurements.

Any light shed would be hugely appreciated, thanks!

 

[BassmanPaul]

Welcome to TalkBass. Why is it that new folks don’t bother filling out their profiles? Knowing your location is helpful when giving advice.

For bass a cabinet needs to have drivers that are happy inside the volume of the cabinet. Just ordering arbitrary drivers is not the way to go. The TS parameters are important in determining how the drivers will respond in a given air space. Xmax is the maximum distance that the cone can travel before damage sets in.

 

[Cirk]

Welcome to talkbass! Please remember to thank your friend for telling you about this site.
What's the model number of your cab? Internal dimensions?

 

[Yokobono]

The model number is '1551'. There was also a '1552' which was exactly the same but had 2 x 250w celestion sidewinders fitted. So i suppose i'm looking for something similar to a celestion sidewinder?

After some digging around online (not able to get over to the studio currently to measure the cab), i believe the dimensions to be as follows:

28.5 wide
28.0 tall
13.75 deep at the top
14.75 deep at the bottom

Also, there is a port of 5.75 in diameter

Thanks!

 

[Cirk]

When you have a chance, see how long the port is. That also matters.
From what I could find, you are correct that there were 2 speaker options for the 2x15 bass cab. The same cab with a different baffle board was used for the 4x12 bass cab. This leads me to believe that it is another case of marketing doing design and stuffing speakers in a box without regard for TS Parameters.
The best I can tell you is to learn everything you can about Thiele/Small Parameters and download a copy of WinISD. Plenty of folks here know more than I do about this. Ideally, you want to build the cab to suit the driver. Doing this backwards is harder, but you should be able to find something pretty close. The whole point of this is to have the right combination of driver and cab for optimal performance.
Homework: go to Wikipedia and other sources to learn about Thiele/Small Parameters and how they work. This may require coffee and a sandwich. You'll be busy for a while.

 

[basscooker]

OP, are you actually using this as a bass rig?

The importance of proper design and matching of drivers and enclosures using Thiele Small parameters is diminished with guitar rigs. You do have the option of "stuffing" this box if there is no intended use of it as a bass cab. Please clearly mark the connector plate for future reference, lol.

Are you tuning down into the bass range? This could bring the T/S numbers back into play a bit more. It's the amount of frequency specific energy you dump into the drivers that determine the level of weight you have to put on some issues like xmax and fs. A standard tuned guitar just isn't going to need 7mm of xmax and an fs of 37 hz to peel off your face.

If it's for a guitar rig, you do have less "technical" options here. All the prior responses are spot on, though if you want to retrofit the cab for use as a modern proper bass cab.