Bass Cab Question

Stupinder · 2nd July 2011, 09:01 AM

Hope someone can give me a bit of guidance here. I'm looking at building some horns for mids and top end for use at home, not PA, and i'm struggling with the bass enclosure.
I have a pair of TOA 15" drivers and i'm looking for a cab to put them in that will do frequencies below 2/300Hz. I'd like it to go as low as possible and being wife friendly isn't really an issue, but i'm restricted to size to some extent - max depth is 1m, width 75cm and heigh isn't really an issue (within reason)
Any ideas where i might get some plans?
Thanks in advance.
Stup'

Brett · 2nd July 2011, 09:48 AM

You need to find the T/S paprameters for the driver or designing for an LF alignment is a very hit and mainly miss proposition.

Once you have them, plug them into a similator program like Unibox and start modelling and asking more specific questions.

sreten · 2nd July 2011, 10:15 AM

Hi, Need to know Fs, Qts and Vas of the driver to define the cabinet options, rgds, sreten.

Stupinder · 2nd July 2011, 10:29 AM

Thanks guys.

Fs - 40Hz
QTS - 0.26
Vas 180l

Sorry to be such a numptoid about this but i'm new to all this and want to get it right first time.

sreten · 2nd July 2011, 11:13 AM

Hi,

What you have are PA bass drivers, designed to go very loud in fairly
compact cabinets, around 50L tuned to 45Hz. What they cannot do
though is low bass, unless you use them sealed and apply bass boost.
Whatever you do F3 is around 100Hz, not good for domestic hifi.

rgds, sreten.

Stupinder · 2nd July 2011, 11:40 AM

They were bought with a view to using them in an open baffle system, which is something i may well try with them.

norman bates · 2nd July 2011, 01:35 PM

open baffle, they will roll off at its mass corner = Fs/qts = about 160hz.

Don't run them open baffle.

Norman

sreten · 2nd July 2011, 01:44 PM

Hi,

Qts is far too low for open baffle, unless again you uses masses of boost.
Or current drive, i.e. an amplifier will high output impedance.

rgds, sreten.

chris661 · 2nd July 2011, 01:50 PM

As a thought, the lowest string on a normal 4-string bass is 41Hz.

A 60L cab (per woofer) tuned to that frequency would give a slight bass shelf (how noticable that will be is debatable), but the lowest frequency the speaker is likely to see will be the one where excursion is minimal.
Add a steep low cut filter below that (most bass amps already have this built-in), and you're good to go.
If you're using a 5 (or 6) string bass, you may need to try different speakers with a lower Fs, in order to cover the lowest note (B0: 32Hz?) correctly.

Chris

Stupinder · 2nd July 2011, 02:12 PM

E bay beckons perhaps?

2nd July 2011, 09:01 AM	#1
Stupinder diyAudio Member Join Date: Apr 2010	Bass Cab Question Hope someone can give me a bit of guidance here. I'm looking at building some horns for mids and top end for use at home, not PA, and i'm struggling with the bass enclosure. I have a pair of TOA 15" drivers and i'm looking for a cab to put them in that will do frequencies below 2/300Hz. I'd like it to go as low as possible and being wife friendly isn't really an issue, but i'm restricted to size to some extent - max depth is 1m, width 75cm and heigh isn't really an issue (within reason) Any ideas where i might get some plans? Thanks in advance. Stup'

2nd July 2011, 10:15 AM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Need to know Fs, Qts and Vas of the driver to define the cabinet options, rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

2nd July 2011, 11:13 AM	#5
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, What you have are PA bass drivers, designed to go very loud in fairly compact cabinets, around 50L tuned to 45Hz. What they cannot do though is low bass, unless you use them sealed and apply bass boost. Whatever you do F3 is around 100Hz, not good for domestic hifi. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

2nd July 2011, 01:44 PM	#8
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Qts is far too low for open baffle, unless again you uses masses of boost. Or current drive, i.e. an amplifier will high output impedance. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

2nd July 2011, 01:50 PM	#9
chris661 diyAudio Member Join Date: Feb 2008 Location: Lancashire Blog Entries: 7	As a thought, the lowest string on a normal 4-string bass is 41Hz. A 60L cab (per woofer) tuned to that frequency would give a slight bass shelf (how noticable that will be is debatable), but the lowest frequency the speaker is likely to see will be the one where excursion is minimal. Add a steep low cut filter below that (most bass amps already have this built-in), and you're good to go. If you're using a 5 (or 6) string bass, you may need to try different speakers with a lower Fs, in order to cover the lowest note (B0: 32Hz?) correctly. Chris __________________ "Throwing parts at a failure is like throwing sponges at a rainstorm." - Enzo My setup: http://www.diyaudio.com/forums/multi...tang-band.html


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2nd July 2011, 09:48 AM	#2
Brett diyAudio Member Join Date: Jan 2002	You need to find the T/S paprameters for the driver or designing for an LF alignment is a very hit and mainly miss proposition. Once you have them, plug them into a similator program like Unibox and start modelling and asking more specific questions.

2nd July 2011, 10:29 AM	#4
Stupinder diyAudio Member Join Date: Apr 2010	Thanks guys. Fs - 40Hz QTS - 0.26 Vas 180l Sorry to be such a numptoid about this but i'm new to all this and want to get it right first time.

2nd July 2011, 11:40 AM	#6
Stupinder diyAudio Member Join Date: Apr 2010	They were bought with a view to using them in an open baffle system, which is something i may well try with them.

2nd July 2011, 01:35 PM	#7
norman bates diyAudio Member Join Date: Nov 2003 Location: iowa	open baffle, they will roll off at its mass corner = Fs/qts = about 160hz. Don't run them open baffle. Norman

2nd July 2011, 02:12 PM	#10
Stupinder diyAudio Member Join Date: Apr 2010	E bay beckons perhaps?

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