Passive Crossover build.

[M1 Lupo]

Andi,

Have you found that site for the crossover calculations?

I'm not too far off putting a parts list together for a large components order myself as I am designing a single channel valve amplifier. Well building three mono block amplifiers to drive my centre and rear speakers. style="vertical-align:middle" emoid=":wub:" border="0" alt="wub.gif" />

Let me know the site and I will see what I can do.

Edited May 19, 2005 by Tigz

[Tigz™]

Ok Im home!

Sorry Dan forgot all about it, and only just found my phone and seen your text message.

Ok the site I use is Basic Car Audio Electronics.

Scroll down to number 54 (passive Crossovers)

The calculater is about half way down.

Take a read mate, pretty bloody intresting tbh

Thanks again Dan. style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

[M1 Lupo]

There is a lot of decent factual information on there! I think I have a mild headache now.

I have worked out how you can highpass the tweeters and bandpass the mids by circuit design, as two separate crossovers as you wanted.

Now just have to work out what parts are needed. Would you want electronics grade components or Audiophile? I can probably locate either.

I will find the prices tomorrow and post them here. style="vertical-align:middle" emoid=";)" border="0" alt="wink.gif" />

[Tigz™]

Thats great Dan thank you.

Glad you understand it.

Expect lots of phone calls lol

I go away in the afternoon for a week, but I will try and find an internet cafe and check in on this.

If not I'll give you a call you about it.

Ive editted the tital of the thread.

I can see this thread becomeing a good one. style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

[M1 Lupo]

Just a quick update.

I have been doing a bit of research into passive crossovers today at work, and one of our regular customers proved to be very usefull.

I can source really high end audiophile grade caps, no problem. The inductors seemed to be a small issue, we sell RF chokes at work. But they are tiny with no real power handling. A friend of mine (customer) makes all sorts of audio gear for a living, he can hand wind inductors to whatever is needed. I'm currently enquiring as to when he can build them.

I have some good material to put up on here, on design of high / low / bandpass passive filters. Which if I hadn't been stuck in work till nearly 9:30 tonight I would have posted..

[Tigz™]

That sounds intresting mate, I had a felling the inductors may have been an issue.

Have you heard anything from him yet?

[M1 Lupo]

Finally I have a chance to be seated and get this up on the forum. The following is how I see the basics of passive crossovers.

Passive crossovers are based on the principle that you can use a coil and / or a capacitor to create a frequency roll of at what ever frequency you wish. Andi found this site Basic Car Audio Electronics which fantastic! It has the calculations to work out what components are needed and compensate for Ohmage of the speakers used.

Now a little on capacitors. There are many varietlys available, but the main type you would use in a crossover is a radial electrolytic.

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Or an axial.

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Capacitors can be either Polarised or Bi-Polar. Polarised cap's have a positive and negative leg, so electricity can only flow in one direction. Making these the choice to use for DC. Bi-polar on the other hand work in either direction, making these the one to use for AC. Capacitance can be measired in nanofarads/picofarads/microfarads and farads.

Bearing in mind that an amplifier drives a loud speaker with an alternating current signal. It has to be AC otherwise your loudspeaker wouldn't move forwards and backwards it would just move in one direction and stay there till the signal was stopped.

Knowing that the amplifier drives with AC, means that you need to use a Bi-Polar capacitor to create the high frequency cut off in a crossover. If you used a Polarised capacitor in a crossover, half the time it would be in reverse bias. Meaning the cap most likely will explode. border="0" class="linked-image" /> border="0" class="linked-image" />

Now the High pass filter. A Capacitor in series with the positive connection from amplifier to speaker will act as the HPF. Typically used for tweeters.

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The band pass filter uses a cap for its high pass filter and a coil for the low pass. This only allows the frequencys that are above the LPF and below the HPF through. These filters can be used for mid range speakers, but within reason could be used on any speaker.

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[Tigz™]

Fantastic post.

Best post thats ever entered the Ice forum imo style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

Its amazing how easy it is (Once you have what you need of course) to build your own crossovers.

Especially when you buy quality aftermarket speakers that require lower frequencies.

And the best thing is, you can use a VW Tweeter, and cross over after market midrange drivers to follow suit.

[M1 Lupo]

Cheers mate,

I wish they let me use the knowledge I have at work...

I am currently waiting on Baz to pop into the shop to find out about the inductors. Plus I'm awaiting my favourite online retailer to have the caps I need for your crossovers. I have the crossovers for the tweeters / mids in hand, parts wise. Are you going to use an active crossover for the sub?

Edited May 31, 2005 by M1 Lupo

[Tigz™]

Yes, I use the headunit, and filter on the amp.

I cant afford to steal any power from the sub.

I feel like Im 100wrms down as it is now style="vertical-align:middle" emoid=":(" border="0" alt="sad.gif" />

Im so bloody excited this will be mint!

[M1 Lupo]

Andi, I'm sick of waiting for my friend to make me some heavy duty inductors. So I have bought a roll of enameled copper wire and a couple of toriodal 'donut' shape ferrites and I'm now having a bash at making some myself.

Please could you tell me what frequency you need the tweeters to be high passed at. And what frequency you want the mids to work in.

[Tigz™]

Ok Dan, heres a few options.

902.314 Pro series tweeter, 80 x 80mm, 1" dome with reflector port

Obviously Im gonna need quiet a powerful amp as the horns are 8ohm, but Id be suppirsed if I could find any 4ohm horns without looking at over priced car audio horns.

Frequency responce looks pretty good though, and they look narror enough to get in the door builds.

Looking at these, I think they'd be more sutable than the wide dispersion horn like the ones you sell at Maplin

Think they will be worth a try at the money they cost, other than the DLS tweeters I told you about, theres no real options when it comes to a more 'normal' tweeter.

[M1 Lupo]

Id say do it. You would then have some good tweeters with an excellent frequency response! Well, technically slightly ultrasonic. Should make the hairs stand up on the back of your neck!

Edited November 10, 2005 by M1 Lupo

[Tigz™]

We'll go with that one then.

4kHz it is then!

[M1 Lupo]

So the tweeters need to start at 4khz. What frequency band do you want the mids to play in?

[Tigz™]

What sort of slope are we looking at Dan?

[nfbr]

Dan, what you know about load resistors??

(i.e. the thing that keeps the impedance at a certain level)

[M1 Lupo]

Andi - As far as I know. 12dB per octave.

Al, I use load resistors in my amplifiers. In my main valve amplifier, I have two 20 watt resistors, in series. Four Ohms each, to create an eight ohm load to the amp, at 40 watts. So I can safely turn on the amp, pre heat the tubes, turn on the HT system. Then switch from the dummy load to the speakers, hence not putting any nasty DC offset signals through my speakers.

I also use load resistors in my headphone amps as a safety feature. I know if you unplug a headphone jack plug, you short the right channel to ground. I'm smart enough to add a pair of two ohm resistors per channel, configured to prevent the channel being shorted to ground and killing transistors... As there is always a 4 ohm load there in case my mother goes on a tidying mission...

Edited November 10, 2005 by M1 Lupo

[Tigz™]

So I think we should be looking around 1khz then Dan.

We'll soon see if my calucutions are any good!

[nfbr]

yumm... valve amps style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

[M1 Lupo]

Valve amps. Oh yes! Love them so much..

Andi, 1k upwards for the tweeters. But what do you want your mids to start working at? 80hz upwards?

[Tigz™]

60hz please matey style="vertical-align:middle" emoid=":shades:" border="0" alt="shades.gif" />

Edited November 11, 2005 by Tigz

[M1 Lupo]

Andi, now I know you like it loud and clear. But I have just cracked it!

I can make you crossovers that could allow you to use upto 500w RMS! yes RMS. Not gay PMPO. Just for the mids..

[Tigz™]

lol Dan you do realise if I tell Emma I now need a 2 x 500wrms amp to power the mids, shes going tp pull off my testicals and feed them to the dog dont you?

You are bonkers, but I love you style="vertical-align:middle" emoid=";)" border="0" alt="wink.gif" />

That would be cool though, if I deside to do away with the sub, I could use the 2 x 400wrms my Rockford amp gives me to power the mids.

Much diffrence in the price?

[M1 Lupo]

Well, I intend to make you these once. But last a life time! You wouldn't have to give them 500w rms. Just as much as you need. Me trying to make them futureproof, incase you get a bigger amp. For the beasty XXX's.

To get the inductors made I need would cost around £10 per inductor. Plus shipping. As off the shelf you cant get anything that will handle more than 100w rms, in the inductance you need.

Then theres the capacitors. I was thinking ones that are meant to go in high end valve amps as they handle really wattages.