i have a friend i am recording some guitar clips for demonstrating the sound acheivable with a guitar pick up he made. he is now building a bass amp and he has emailed me the following question -


reevo, im designing an amp speaker cabinet for an eminence ca2010 bass
speaker, theres a downloadable spec on thier web site eminence.com
whats the difference between a small vented cabinet & a small closed
cabinet....in terms of sound ?.this is for a bass driver . theres also
mention of 2 holes in the vented , 1 at 4" diameter & a 2nd at 7.5"
diameter ? does the larger one need to be front mounted? i dont
understand it . can you help? im using this with a wal bass which is
a modern sounding bass with very high & low outputs , have a look on
their site ... walbasses.co.uk theres a bit about the preamp &
filters in the instruments & how low they go. im ordering the wood
(oak) 20mm thick for the construction as its quite cheap here &
natural woods sound better than composites . ive figured out the
internal area from the cubic foot guide from eminence , just dont know
wether to build a vented or closed cab. cheers , mh


my understanding of a vented cab is that it sounds better with low end freq as it pushes the sound generated from the rear of the speaker out of the front. is this correct? I have never built anything like this before and thought someone one here may be able to explain a little better than me.

cheers

Alex

Alex,
the advantage of a reflex enclosure is that it gives more LF output for a given size of cab but at the expense of a worse, often much worse response in terms of "flatness" and (for the hi fi buffs) a worse transient response. Even then the extra output will only be realized if cab and port follow very closely the drive units parameters, i.e. you need a makers drawing and stick rigidly to it! Ported cabs also "unload" the speaker for VLF and this can lead to speaker damage.

In the absence of a detailed drawing go for the biggest sealed cab you reasonably can.
I would not use natural timber and oak is a bugger to work with! MDF is acoustically better as it is dense and inert but will be too heavy for a portable speaker cab. Marine grade ply and plenty of bracings should do the trick.

Dave.