Any musos out there?

[bassboy]

LAdies and gents...some advise please.

I have bought a custom 1x18 cone which i wish to put into a cab so i can shake the ground with my bass guitar. It is one as used by a well known music company. Unfortunately i don't have any of the tech specs for it....yikes. I do however have the EXTERNAL dimensions of the cab that they use. I am missing one (or 2) of the others.

So any BASS players out there who cna help me please reply or PM me so i can chat...

BB

[sreten]

If you put it in a sealed box of approximately the correct
dimensions you will be very near the commercial model.

As its an 18" I assume its not a vented / reflex cabinet,
this is usually ~ twice the size of a sealed box and for
a PA 18" driver this usually would be a very large box.

Whether the 18" has enough midrange ? who knows ?

sreten.

[bassboy]

thanks for that sreten. I have done some looking around and found that most of the 18" i have looked at have ports. Might og to the shop and see if they have a cab to copy......or else start from scratch. I know it is tuned for 25hz.....

as for my mids...i think i'll let the 2x12 cope withe these as my bass amp is bi-ampable. Will push the lows out of the 18 and the rest from the 2x12.

Cheers for your help mate.....

BB amd the monster rig.....

[sreten]

I've done some modelling with PA drivers and it turns out
that for many a low tuned port (25Hz to 35Hz) can be
added without upsetting things too much.

Usually the port doesn't do anything much for frequency
response but does greatly increase power handling.

For a 4 string bass the port should be tuned to 40Hz,
though for an 18" I'd drop this to 35Hz.

For a 5 string low B bass the port should be 30Hz,
minimum I'd say would be 28Hz.

sreten.

[bassboy]

cheers buddy. I tend to play with a low b and got the freq of it from the internet. Was looking to port the cab to about 25 hz but the response looked badd on the graph so i think i'll do as you say ( and i have looked at some of your other posts, very informed) and tune it to 30hz. I think the likelyhood of me dropping my low b any further is slim.

Once again....thnanks a million for your help with this. Hope to get some ply this weekend and i'll make it up soon. Will get some pics for you!

Chris

[bassboy]

Mr Sreten...have almost built my cab.....just working out ports on it though. I managed to get some info about the SWR one and the ports are only holes (no tube at the back) They are 6 inches in diameter. One thing i'm not sure about is would it be possible to use 3 5inch diameter holes instead of 2 6inch ones?....I know the rules on porting but since there is no lenght associated with them is it safe to assume the rules about surface area are the same?

Thanks and i'll post some pics for you

Bass boy

[sreten]

Plain hole ports are not good, end of story.

They ideally should be between 1:2 and 1:2 diameter:length.

Here we are looking at 1:1 I think.

Identical multiple ports are not a problem, design by
dividing cabinet volume by the number of ports.

Post your cabinet volume, I'll post details of 30Hz ports.

sreten.

[bassboy]

Thanks for your help with this. I have already got 2 4inch ports with the pipe on the back to cut to length. Would it be possible to get a 3rd to have 3 of them? ( this is purely astetic?...it looks better with 3 across the bottom, more symmetrical)

I have also done some measuring and have worked out the box is

0.395 x 0.74 x 0.574 all in metres

this make ( i think) the box volume 0.1678 cubic metres or
167.8 litres

I made it using simple butt joints with 18mm square rod...but i haven't taken this off of the box volume (it would be small in proportion to the total volume i think)

Cheers for all of your help with this.....i'll should come and visit you next time in the UK....i'm an expat Scot now in Oz

Once again Thanks

CHris

[bassboy]

done some crunching too......might go with 2 at 4inches

comes out with details:

vent lenght 0.242 metres..... Vent Match 0.1


USed winISD to work it out.

Is this sounding good or not?

Chris