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Problems with 18" project

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Category: Plans
Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
Printed Date: 22 February 2024 at 11:43am
Software Version: Web Wiz Forums 12.06 -

Topic: Problems with 18" project
Posted By: 13Tez
Subject: Problems with 18" project
Date Posted: 23 December 2008 at 10:23pm
Hi all this is my first post so here goes:
Ive been fiddling around with ht audio bass pro 6 for some time now, Im trying to design a vented cab (for playing bass guitar through) I really want something that can go lower than 40Hz, som where around 30-35Hz would be good. Been looking at the celestion ftr18 4080fd. However after finally getting the desired cut off frequencies, I checked through the other grahps given by bass pro and it seems the driver would struggle, at some frequencies, handling the 500w input.
Im no expert at all this so can anyone point out where Im going wrong? Ive tried everything on bass pro from box size to port size etc. Ive tried a different driver one with a bigger Xmax and it performed much better, could it just be the driver?
Any help would be great.

Posted By: _djk_
Date Posted: 24 December 2008 at 12:17am
You're fine with bass guitar if you go beyond x-max.
It's sine-sweeps where you get into trouble.


Posted By: Elliot Thompson
Date Posted: 24 December 2008 at 5:01am

Try a 183.6 liter (Internal) box tuned to 35 Hertz. You should be at 36 Hertz - 3dB (36.52 Hz f3) Normalised Gain with the Celestion FTR 18 4080FD driver.

Best Regards,

Elliot Thompson

Posted By: 13Tez
Date Posted: 24 December 2008 at 9:42am
Brilliant! Thanks for all the advice, got a graph now that looks rather tasty Tongue. Do I not need to worry about the "Maximum Electrical Input Power" Graph? It dips below 500w between 37-77Hz as low as 200w.

Posted By: Elliot Thompson
Date Posted: 24 December 2008 at 12:17pm

Punch these numbers in Bass Box Pro

Vb: 183.6 Liters

Fb: 37 Hz
QL: 7

Your Maximum Electrical Input Power should be 1000 watts from 100 - 34.7 Hz with an f3 of 36.82 Hertz. Normalised Gain should say 36.7 @ -3 dB

Bare in mind the xmax is 12 mm so, you should not encounter any problems from 30.6 - 100 Hz feeding it a 1000 watt amplifier. The Xmech is 18 mm one way or 36 peak to peak.

If I can feed the older Celestions that offer an xmech of 16 mm one way 1000 - 1500 watts without them damaging, this driver will handle 1000 watts as well.   

Best Regards,

Elliot Thompson

Posted By: aperrado
Date Posted: 26 December 2008 at 4:16am
where can i get bass pro ?

Im hard to learn but still asking

Posted By: tomschute
Date Posted: 29 December 2008 at 8:17pm
Originally posted by _djk_ _djk_ wrote:

You're fine with bass guitar if you go beyond x-max.
It's sine-sweeps where you get into trouble.


so with regards to "electronic" music what would you regard as a safe tolerence to work too for pushing you drivers past there x max?

Obviously it's not an option i'd like to take but i'm trying to box some 15" mckenzies and with 4.5mm x max i'm getting alot of probs keeping excusion below 5.5mm to 6mm with the desired freq range wanted... am I gonna kill them... again...

oh and Bass Box Pro available at -

Out to lunch...
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