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Old 15th August 2012, 12:58 AM   #1
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Default Linkwitz Transforms

Hey guys,

I have really been researching the LTC and still have quite a few questions. First, here are the component values I have settled on and the circuit I want to use (see attached for circuit schematic).

C1 - 2.157μF
C2 - .068μF
C3 - .4014μF
R1 - 7.17kΩ
R2 - 39.96kΩ
R3 - 38.53kΩ

Now for the questions:

1. What is the difference between an opamp and amp? What would a traditional car amp be considered? What would a traditional home amp be considered?
2. Where exactly does this circuit get placed in regards to the signal source, amp, and driver? If the placement is between the amp and driver, as I believe it to be, how many watts can this circuit handle? How can I determine and appropriate this?
3. When selecting components for the circuit, what is the best way to determine the necessary component values to approximate calculated values with the least error?
4. When selecting resistors, how do I determine whether the resistors need to be 1W, 2W, 5W, etc? How do I determine whether the resistors need to be carbon, flameproof, etc?
5. Same question but in regards to the capacitors and their appropriate differences.
6. Where could I go to have this circuit built or bought without purchasing it from Australia?

Even if you can only answer one, or part of one, question I would appreciate it.

Thanks,

Tony
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Old 15th August 2012, 01:04 AM   #2
AJT is offline AJT  Philippines
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welcome to the forum, where is the attachment?
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the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
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Old 15th August 2012, 01:18 AM   #3
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You have a whole lot to learn before you will be able to implement this circuit properly.

Start here....

Operational amplifier - Wikipedia, the free encyclopedia

Linkwitz Transform Subwoofer Equaliser
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Old 15th August 2012, 01:35 AM   #4
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I don't know why it didn't attach.
Attached Images
File Type: jpg Circuit.jpg (9.3 KB, 252 views)
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Old 15th August 2012, 01:36 AM   #5
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Quote:
Originally Posted by theAnonymous1 View Post
You have a whole lot to learn before you will be able to implement this circuit properly.

Start here....

Operational amplifier - Wikipedia, the free encyclopedia

Linkwitz Transform Subwoofer Equaliser
I have read all this.
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Old 15th August 2012, 01:50 AM   #6
tvrgeek is offline tvrgeek  United States
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OK, You are talking about building a Linkwitz Transform circuit to equalize a sealed woofer that has very low Q, correct?

I don't want to sound discouraging, as I welcome everyone to DIY, but you are starting way over your head. We can easily answer all your questions, but I am afraid it would not be helpful.

To get started learning electronics, you need to start with the basics. Probably a lot of us started by building kits. ( we had Allied, Dynaco and Heath in those days) and most probably read Popular Electronics as kids. You would be surprised here how many may have degrees in electronics, built ham radios, or tinkered as little kids. I built my first crystal radio at about 7 and for many, that was late. But, you can do this yourself! You don't have to have a degree. It just helps.

The Linkwitz Transform Circuit is a very simple in execution, but you must understand what it is trying to do, and how it works with the speaker. It is part of the entire amp-speaker system. It is not just some bass boost. Most sub amps have some amount of bass boost built in. It would not be a LT as it would not be correctly calculated for a specific Q.

Even if you chose not to buy boards from ESP, his documentation is very good. A far more advanced discussion would to be to go to the source and visit Siegfried Liknwitz's WEB. If cornered, I bet a lot of folks here shudder when trying to understand s-plane, so don't get too discouraged when you see high level engineering math. It is a good to see what can be learned. Electronics is actually pretty straight forward. E=IR.

Quick answers. Op-amp here means an integrated circuit that behaves as an operational amplifier. For this use, you would want metal film resistors in 1/8 or 1/4 Watt. The circuit goes between the preamp and the power amp. It also needs a power supply. Caps are horribly complex little buggers, but you want to use a film type with a voltage at least double what the circuit would ever see. There are several web based sites that will calculate the values for you. If you don't want to buy boards, you build one of perf board. You don't need to be that precise in values because the speaker is not that precise. You don't know what the target values would be unless you can measure some parameters of the completed speaker.

Now, unfortunately, that does not help you build one. I just want to be realistic. I suggest you buy a car stereo crossover or amp with bass boost built in, then we can take some time to get you started properly in DIY electronics. Safer that way. Of course, one of the best approaches is to take basic electronics at your friendly community college. Something like a CMoy headphone amp would be a good start. Or any of the Radio Shack basic kits.

This is a great hobby. It can keep your mind going. The first time you build a circuit that works of your own design is a wonderful feeling. Of course, the first time you fail to keep the smoke inside the wires is not so wonderful. We have all been there and revisit that space more than we care to admit.
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Old 15th August 2012, 02:05 AM   #7
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Quote:
OK, You are talking about building a Linkwitz Transform circuit to equalize a sealed woofer that has very low Q, correct?
Yes

Quote:
To get started learning electronics, you need to start with the basics. Probably a lot of us started by building kits. ( we had Allied, Dynaco and Heath in those days) and most probably read Popular Electronics as kids. You would be surprised here how many may have degrees in electronics, built ham radios, or tinkered as little kids. I built my first crystal radio at about 7 and for many, that was late. But, you can do this yourself! You don't have to have a degree. It just helps.
First, thanks for not just dismissing me. I like to consider myself bright and a fast learning, I just need the direction. The problem I run into is the inability to find the resources to learn... I have taken Physics 1 and 2 at the CC, along with my degree courses, but its apparent just a few more classes are required ha. And I know there is a lot of learning involved, and the direction is what I need.

Similarly, I know this is suppose to be a fairly "simple" circuit with pretty impressive results, so it interests me. I would not mind buying a pre-built circuit, would actually prefer it, but buying it internationally I would like to avoid.

Thanks again, this was a lot of help.
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Old 15th August 2012, 02:23 AM   #8
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Here is a link to a site were you can get a p.c. board and full information for a L-T circuit...
Linkwitz Transform Subwoofer Equaliser
rcw
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Old 18th August 2012, 11:06 AM   #9
tvrgeek is offline tvrgeek  United States
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We all had to get started somehow.

You may not have noticed my comment, you also need a power supply. These too are pretty simple. You need a basic small plus and minus 15 to 17 volt supply. Simple three terminal regulators will work fine. There are many kits for this on the web. Of course, playing with a power supply means playing with line voltage and though not at all hard, there are a lot of little details to be know. There is a reason for those UL and CSA stickers on the backs of things. ( My apologies, I don't know the EU program).

By adding sufficiently large blocking caps, you could just run it off a few of 9V batteries. At least this would get you started easy, cheap and safe. ( before anyone else jumps in, yes single ended supply for batteries unless you build an artificial ground as one battery will drain quicker than the other and cause big offset issues. I am trying to keep this simple)

For an op-amp, just use a normal NE5532. More than good enough. Heck a good TLO74 is fine. You can hard wire this up on a good old vector board along with the power supply.

I don't know your location, but by far the best way to get going is with someone looking over your shoulder. There are so many little details we all forget to mention. I was very lucky that my father is an EE so we spent many an hour at a chalk board where I learned my basics. A CC night class or three ( thinking back, Basic AC/DC, Devices, Circuits.... ) would probably get you going. You are probably way ahead of the typical ET student as you will have had the math. (Tip: In electronics, we use "j" instead of "i" for the sqrt of -1.) Really too bad we don't have Heathkit anymore. Nothing like seeing physically how things are put together. Most "DIY" kits are just a main board leaving it up to you to deal with cabinets, power and safety issues.

To use the LT, you do need to know the target Q and response. This is why ESP also has the "sub controller" that is variable so you could tune it by ear. The LT requires you know the speaker.
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Old 18th August 2012, 06:23 PM   #10
AndrewT is offline AndrewT  Scotland
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back to designing and assembling the Linkwitz Transform.
You need the T/S parameters of the speaker.
You need the box that the speaker will be fitted into.
You need the "parameters" of that completed boxed speaker.
You need the parameters that you want that speaker box transformed to, i.e. the target parameters.

Then you plug all your various numbers into Linkwitz's formulae.

Start by giving us the speaker and box data.
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