A
Anthony_Gomez
Admin Note - This thread is now been designated the Official Linkwitz Transform Discussion Thread. Please post all questions on LTs in this thread. Thanks.
(please forgive any spelling, grammar errors or typos)
What is a Linkwitz Transform you ask?....
Quite simply, an LT (LT=Linkwitz transform) is a piece of active circuitry that functions as a very special kind of bass boost for SEALED ENCLOSURES ONLY (or infinate baffle).
The really really really rediculously good:
What it does is artificially takes ANY sealed or IB sub and give you ANY response you want!. YOU choose what you want the QTC and Fb of the box to be. If you want the box to be the size of a tissue box and have a Qtc of 1.00 with an Fb of 10hz, you can have it!! The size part is the SAF dream come true
The bad::frowning:
This device is not magical. Being able to have any response comes at a price. For every 3db you boost, you require 2x the amplifier power. With this power, you now start chewing up xmax rather fast and given enough power, you will start to run into driver compression (driver compression is where you do not get what you put into the system. Going from 500-1000watts should give you 3db more gain, but compression might yield only a 2db gain).
More bad:
So as you can see, the more extreme LT systems require high excursion drivers (may have to then contend with an inductance hump)and a hefty amp which together yield a hefty price tag.
BUT, not all LT'd systems are extreme. Some could only add 3 db which isn't less than most bass boosts but you yield a superior driver response...so normal amps and drivers can be used! Others like myself and Jack Gilvey will go a little more extreme and get a 1000+ watt amp with a monster driver in a little box or an infinite baffle.
Lets see an example:
The new Tumult 15 driver is a superior LT driver. It has really high LINEAR excursion, high Surface area (15" driver) with monster power handling and no inductance hump (and it should be selling pre-order at a super price!). You want to drop it into a 17" cube and after subtracting all the bracing and driver displacement, you end up with a 42.8L enclosure. You then open up a modeling program like UNIBOX (linked below) and use it to calculate your actual Qtc and Fb. I like to model with no leaks and heavy stuffing. This yields a Qtc=0.707 and an Fb=36.8hz. You don't care so much about the sub being really really loud, but rather have it play really low with a loq QTC for your organ music that you love so much. So you WANT a Qtc of 0.55 and an Fb of 18.5hz (yields an F3=25hz which the program should calculate).
This equalization yields total boost of about 6db at 20hz and raises up to about 8.5db after you account for the input buffer. Lets say you are really cool and have a Crown K1 amp that puts out 1500watts RMS into 4ohms bridged. If we just consider 20hz and up, your 6db gain has already cut that amp effectively down by a quarter...or 375watts..but if you want to consider down to 10hz, you only have ~210watts to work with (but the driver is beyond it's linear excursion at 10hz with 255watts). Back to 375watts for 20hz and up. The single driver is rated about 85.5db 1w1m. With 375watts, you can get a maximum db of 111db at 100hz and 106db at 20hz (-5db down) and the driver happens to be at its xmax.
How can you model these things yourself?
Simple...download one of the many spreadsheet programs that are out there. Below is a link to the FRC consortium that has UNIBOX and an TL program that I helped to author.
http://www.pvconsultants.com/audio/frdgroup.htm
How can I get one of these?
If you are interested in an LT, you can work up a breadboard by yourself, or get one of the high quality PCBs from Rod Elliot at Link Removed. You will also need to get a power supply built for this too which I know Rod sells as well (there are other sources for these PCB's). OR you can get an adjustable (on the fly) LT from Marchand Electronics under the name BASIS at http://www.marchandelec.com
If you don't want to build your own and cannot afford the Marchand Bassis pre-built option, then you should have a look at this thread:
http://www.hometheaterforum.com/htfo...threadid=88950
Enjoy!!!
Hope I didn't confuse the heck out of you with all of that!!!
(please forgive any spelling, grammar errors or typos)
What is a Linkwitz Transform you ask?....
Quite simply, an LT (LT=Linkwitz transform) is a piece of active circuitry that functions as a very special kind of bass boost for SEALED ENCLOSURES ONLY (or infinate baffle).
The really really really rediculously good:
What it does is artificially takes ANY sealed or IB sub and give you ANY response you want!. YOU choose what you want the QTC and Fb of the box to be. If you want the box to be the size of a tissue box and have a Qtc of 1.00 with an Fb of 10hz, you can have it!! The size part is the SAF dream come true
The bad::frowning:
This device is not magical. Being able to have any response comes at a price. For every 3db you boost, you require 2x the amplifier power. With this power, you now start chewing up xmax rather fast and given enough power, you will start to run into driver compression (driver compression is where you do not get what you put into the system. Going from 500-1000watts should give you 3db more gain, but compression might yield only a 2db gain).
More bad:
So as you can see, the more extreme LT systems require high excursion drivers (may have to then contend with an inductance hump)and a hefty amp which together yield a hefty price tag.
BUT, not all LT'd systems are extreme. Some could only add 3 db which isn't less than most bass boosts but you yield a superior driver response...so normal amps and drivers can be used! Others like myself and Jack Gilvey will go a little more extreme and get a 1000+ watt amp with a monster driver in a little box or an infinite baffle.
Lets see an example:
The new Tumult 15 driver is a superior LT driver. It has really high LINEAR excursion, high Surface area (15" driver) with monster power handling and no inductance hump (and it should be selling pre-order at a super price!). You want to drop it into a 17" cube and after subtracting all the bracing and driver displacement, you end up with a 42.8L enclosure. You then open up a modeling program like UNIBOX (linked below) and use it to calculate your actual Qtc and Fb. I like to model with no leaks and heavy stuffing. This yields a Qtc=0.707 and an Fb=36.8hz. You don't care so much about the sub being really really loud, but rather have it play really low with a loq QTC for your organ music that you love so much. So you WANT a Qtc of 0.55 and an Fb of 18.5hz (yields an F3=25hz which the program should calculate).
This equalization yields total boost of about 6db at 20hz and raises up to about 8.5db after you account for the input buffer. Lets say you are really cool and have a Crown K1 amp
that puts out 1500watts RMS into 4ohms bridged. If we just consider 20hz and up, your 6db gain has already cut that amp effectively down by a quarter...or 375watts..but if you want to consider down to 10hz, you only have ~210watts to work with (but the driver is beyond it's linear excursion at 10hz with 255watts). Back to 375watts for 20hz and up. The single driver is rated about 85.5db 1w1m. With 375watts, you can get a maximum db of 111db at 100hz and 106db at 20hz (-5db down) and the driver happens to be at its xmax. How can you model these things yourself?
Simple...download one of the many spreadsheet programs that are out there. Below is a link to the FRC consortium that has UNIBOX and an TL program that I helped to author.
http://www.pvconsultants.com/audio/frdgroup.htm
How can I get one of these?
If you are interested in an LT, you can work up a breadboard by yourself, or get one of the high quality PCBs from Rod Elliot at Link Removed. You will also need to get a power supply built for this too which I know Rod sells as well (there are other sources for these PCB's). OR you can get an adjustable (on the fly) LT from Marchand Electronics under the name BASIS at http://www.marchandelec.com
If you don't want to build your own and cannot afford the Marchand Bassis pre-built option, then you should have a look at this thread:
http://www.hometheaterforum.com/htfo...threadid=88950
Enjoy!!!
Hope I didn't confuse the heck out of you with all of that!!!
