Crossover

[lowell]

Got a Mackie powered speaker that I wanna gut and convert to passive. Curious on how y'all go about installing crossovers and if you make em from parts or just buy one of the many assembled options on sites like Partsexpress.com. I can go either way....but like advice from folks with experience. Love to learn from others who know the most efficient approach!

[olddawg]

Got a Mackie powered speaker that I wanna gut and convert to passive. Curious on how y'all go about installing crossovers and if you make em from parts or just buy one of the many assembled options on sites like Partsexpress.com. I can go either way....but like advice from folks with experience. Love to learn from others who know the most efficient approach!

A lot depends on the application. The most efficient approach is to simply run the woofer full range and parallel the horn off of it with a 2.2uf (or thereabouts) bipolar cap on the positive terminal of the horn. Most people can't tell the difference.

[eschertron]

A lot depends on the application.

+1

Unless the listening room has been tuned and is flat across the spectrum, limiting the LF into the tweeters is probably good enough. Find the value of cap that prevents too much LF into the tweeter, and also doesn't create a noticeable notch in the response.

edit: how much engineering do you want to put into it? - or - how much money?

[lowell]

how much engineering do you want to put into it? - or - how much money?

Minimal. Hey lets face it, guitar amps, bass amps, speaker cabs etc... it's not rocket science right? So whatever gets the job done (aurally) in the most efficient, low cost manner. Thanks for the input and that's a great point.

Woofers are basically low-pass filters in themselves. And depending on the speaker, the roll off is more or less. So I'll let the woofer handle that. And yes a simple series cap to the tweeter makes sense too....except I'm thinking the wattage of the tweeter will need to be compensated for somewhat. I'll see what the RMS wattage to the tweeter is after the cap is installed and report back.

See I was initially thinking inductors and caps... and bulb limiters. But this is more simplified and will probably be sufficient. Exactly why I posted. I think I will however add the bulb limiter.

[The Dude]

Parts Express has lots of available crossovers if you care to look through them.

https://www.parts-express.com/

[Chuck H]

+1 on Parts Express. They're not exactly a budget saver, but they have the stuff, and a lot of it that you can't easily find elsewhere. As mentioned, unless you're tuning to some very specific requirement, keep it simple. I don't know (but always wondered) what the downside is to running frequencies into a woofer that are above it's ideal response. Amplifier efficiency? Any damage potential? Sans either you can just go with the capacitor to the tweeter as mentioned. If you find you WANT to use a full crossover, buy a ready made one within the parameters you need. Building your own from parts would probably be more expensive in the end.

[potatofarmer]

I don't know (but always wondered) what the downside is to running frequencies into a woofer that are above it's ideal response. Amplifier efficiency? Any damage potential?

I believe it's mostly an issue of not running dissimilar drivers in the same pass band - funky phase interference and whatnot. I guess you might want to check what the resulting impedance is over that range too, but most woofers' impedances are already starting to rise significantly by the time it meets the tweeter.

Yep, Bill Fitzmaurice confirms my suspicions here: https://www.talkbass.com/threads/hig...owpass.362964/

[eschertron]

So I'll see what the RMS wattage to the tweeter is after the cap is installed and report back.

Music typically has a freq spectrum with energy 'about' 1/f , each octave carries about 1/2 the power of the octave below. I see loudspeakers with the tweeter sometimes rated at a tenth of the woofer. Your powered speaker probably has a LF to HF amp ratio of 5:1 to 10:1 because that's all the power the tweeter needs (for typical music program material). Once a crossover is installed, you can measure the power (pink noise or music) and guesstimate that raising crossover by an octave halves the power, lowering the crossover by an octave doubles it.

[Enzo]

P_arts Express sells made up crossovers, but they also sell bare circuit boards for crossovers, just install your own coils and caps for the frequency points you desire. They have charts to help you select values. They have a variety, two way, three way, subwoofer, etc.

[tedmich]

Erse audio sells there own stuff (also sold at PE) and their calculators work well too
Premium grade audio components including crossover inductors, audio capacitors, electronic assemblies | ERSE Audio

[TomCarlos]

And several web sources that have Crossover Calculators. If you are going with a simple first order, you can use this one... AJ Designer Calculator.

[lowell]

You guys rock!

[Chuck H]

I use a lot of on line CAD and calculators. In fact, I'm impaired enough WRT some of the math and theory behind electronic design that I RELY on them Fortunately for me I haven't been thwarted in my efforts by any particular websites going belly up yet. And I often gain a little knowledge in my weak areas whenever I use a program. Since I've only ever done electronics as an avocation (albeit with occasional fits of obsession) I expect to continue learning and having fun with this to the end

[Mick Bailey]

I've often thought about the separation of LF and HF. Apart from phase interference, I wonder if there's a possibility of a dedicated LF driver being damaged by excess HF not being dissipated as sound energy, but being turned into heat due to the inertia of the cone and voice-coil assembly (plus suspension elements)? This would depend on the program material.

Also, in a simple series-cap filter to route the HF to the horn, there must be some absorption of the HF spectrum if that part of the signal 'sees' the LF driver.

[loudthud]

I have experimented with passive crossovers and found that a low pass filter on the woofer makes the high frequencies sound clearer. You can hear it right away as you move the woofer lead from the crossover input to the LF output.

The simple series capacitor on the tweeter will limit the amount of power the tweeter will handle. For a speaker system that plays LOUD, you will need a better crossover to protect the tweeter from burnout.