making a high pass filter....

[bezz]

Hi,
I got some tweeters to run in the front of my VK but they dont have HPFs on them. I thought I may as well build them, however I'm unsure as to what combination of resistor and capacitor to use to give a good cut off frequency.
the equation for it is f = 1/(2.pi.R.C)

Or if thats too much hassle could someone show me where to buy said HPFs for a low low price!?

Cheers

 

[Phreddy]

The simplest high pass filter of all is simplay a bipolar capacitor in line with the tweeter. You can make it a more finely tuned by adding an inductor coil as well. The value of the capacitor / inductor are determined by the crossover frequency in conjunction with the driver impedance.

Have a look on Jaycar's web site - they have a reasonable guide to DIY crossovers here....

http://www.jaycar.com.au/images_uploaded/crossovr.pdf

There's a handy cross reference chart near the bottom, you should be able to find what you need there.

Cheerz! :thumbsup:

 

[bezz]

cool thanks for the info. a couple more questions, what is a good cut of frequency for a tweeter, and what size capacitor would you recommend for it? (if i decide to just use a capacitor and series and no inductor).

thanks again

 

[azzfox]

the tweeters from jaycar are High Passed at 10kHz (10,000Hz) if thats any help.

 

[phree]

cool thanks for the info. a couple more questions, what is a good cut of frequency for a tweeter, and what size capacitor would you recommend for it? (if i decide to just use a capacitor and series and no inductor).

thanks again

the tweeters from jaycar are High Passed at 10kHz (10,000Hz) if thats any help.

10k Hz would be ok if the tweeters were for "ambient" use. i.e. an extra tweeter to boost only the very high frequencies to fill in gaps in the frequency response up high. They can also be used to correct staging/imaging issues.

Most mid woofers will not play well up to 10k Hz. Most car systems work best with a xover cutoff around ~3-4k Hz for two way systems. Three way may be different, with a separate mid range driver, but still not usually that high.

It is important to take into account the tweeters power handling ability. It is easy to let the smoke out of them if they are crossed too low. Their power handling is better the higher the frequencies they play. Sensitivity and impedance are also important if you are going to run them on the same amp channel as the mids.

Anyway if you give some more info about your gear we can make some suggestions.
1) What do you want to achieve exactly?
2) What brand and model are the tweets you have? We need the full specs.
3) What is the rest of your system made up of? Do you have splits or coax/full range speakers in your car now? How are you planning on powering them? What amp/s etc?

Cheers

 

[bezz]

1) i want to add some sound to the front of my vk, as I won't be putting front speakers in (planned restoration so i dont want to hack up the door trims)

2) pioneer, look fair old, not sure on model

3)haha you're gonna flame me now...
the system in this car is made up of bits n pieces i had lying around/got out of cars from auction. I'm saving my better components for a new car.
Anyway my system in the vk is as follows:
sony cdxl450x h/u
pioneer 6x9s (unsure on model but have a white cone)
pioneer 10" sub amped by boss ba 2200 :whistling

The 6x9s give a real unclear sound in my ears and I would prefer to replace em with some decent coaxials or something, but I'll just stick with what I have for now. By adding the tweeters and setting them up right i was hoping to enhance the sound quality just a little. Mids are something ill have to contend with later

 

[Phreddy]

Hey again Bezz.

Heh - everything Phree said above!!

When you're talking about speaker "systems", then it really does mean SYSTEM. It's a balance of what sounds are handled by what drivers, and the crossover points are set appropriately to that - but there are so many other variables in the equation....

A properly "crossed over" system will have not only high pass to the tweets, but low pass to the bss/mid. If it's a three way system (a PROPER one) it will also have "band pass" for the midrange driver. (the three and four way 6x9s commonly seen don't have a proper band pass filter for the midrange - most are just a cheap high pass, but at a lower frequency that the tweeter)

It's a complex subject, and just to make it a little bit harder is the personal preference side of it too! What sounds good to me might sound like arse to you!

Try this for a starting point though....

Let's assume a couple of things - your tweeters are a dynamic type (ie cone or dome, NOT piezo), and they have a 4 ohm impedance. We'll aim at a 10KHz crossover for now, so what you'll need for the simplest filter will be a bipolar electrolytic capacitor with a value of 4uF (micro-farad).

You'll be hard pressed to find one rated at 4uF, but you'll easily find a 4.7uF. (that will drop the crossover point slightly, but not much) If you have a Jaycar store nearby, the catalog number is RY-6904. Don't forget to use a BI-POLAR electrolytic, otherwise you might let the smoke out of that too. Just wire this capacitor in series (ie. In line) with the wiring to the tweeter, and Bob's your auntie's live-in lover.

Cheerz!

 

[phree]

Yep, what Phreddy said.:thumbsup:

I would check the dc resistance of the tweeter with a multimeter. This can give a clue as to it's nominal impedance. It is important to now this to even guess at the required value for a xover cap. To make an accurate choice, you need to know the impedance at the xover point. Separate tweeters typically (should) come with an impedance curve just for this purpose.

You can create different values by connecting multiple caps, in series or parallel as necessary.

Try what Pheddy suggested and let us know how it sounds. It will be safe at that. Be gentle with the volume at first. It may be the case that the tweets have a significantly higher sensitivity than the 6x9s. Therefore too loud relative to the 6x9s at the same volume setting. This may require a different set of components to fix.

Maybe grab the next couple of higher value caps as well. Just in case you want to lower the cutoff some more to include some vocals etc. They don't cost much in the end.

Anyway getting a bit OTT, LOL. I am doing some designs for some new home audio speakers at the moment and got a bit carried away with my newly aquired xover theory. Sorry.

Have fun!

Cheers

 

[Phreddy]

Anyway getting a bit OTT, LOL. I am doing some designs for some new home audio speakers at the moment and got a bit carried away with my newly aquired xover theory. Sorry.

Cheers

Ah, a man after my own heart.....

Good luck with the project Phree - let's know how it goes! (if they're three-ways, best of luck with the bandpass section!) :bang:

(funny ain't it - you could probably buy off the shelf to sound pretty much as nice for a good bit less bux these days, but there's nothing like building it yourself, huh?)

Cheerz!

 

[phree]

:wave:
Hi Phreddy.
No, just 2 ways at this stage. Then a single active sub, with inbuilt adjustable xover, to fill in the lower octaves. It's for music not ht use.

Yeah, it's a great feeling when you DIY, very satisfying.

Since i upgraded the car stereo, i can't listen to my existing indoor system without wanting to vomit. Used to think it was ok! Rediscovering music i am, all sorts of things in my music i've never really heard before. Can be quite an emotional experience. :cry:

The missus is also into it, which is a bonus when it comes to funding it and justifying the time spent in the shed.

Cheers