Basic Crossover Question

[tube power]

In the case of this two way crossover...


Dayton Audio XO2W-3.5K 2-Way Crossover 3,500 Hz 260-146


Does it keep anything over 3500 hz out of the woofer


and


anything under 3500 hz out of the tweeter ?

[Steve Conner]

Yes, but not perfectly. At 3500Hz the level to both the woofer and the tweeter is down 3dB or so. Then it decreases 12dB per octave. So that means at 7000Hz the tweeter will have essentially full output, while the woofer will be 15dB down. (Or thereabouts.)

Vice versa, at 1750Hz the woofer will be fully active and the tweeter will be 15dB down.

That should be enough to at least prevent damage to a tweeter that's specified for use with a 3.5k crossover, so in this basic sense the answer to your question is yes.

But it doesn't guarantee that the thing will sound good For hi-fi grade performance, the crossover needs to be matched to the particular makes and models of drivers you're using. At the very least some form of attenuator to match the tweeter sensitivity to the woofer.

[tube power]

Steve


If I understand you correctly, that sounds like a reasonable trade off, if it does indeed sound good.



I am studying passive crossovers in bits and pieces, and as you may recall from help you have given me in the past,
I'm not very savvy to electronics, but I'm game to tinker and try to understand things when time permits.


As I gain a better understanding, I would like to construct as close to an ideal crossover system as possible.
But for now I'll settle for what may be less than perfect sound in exchange for speaker protection.
They are getting expensive!

[tedmich]

many fancy computer programs help audio engineers design crossovers, even ones which correct for little dips and rises in speakers response, which is never perfect. More modern approaches include crossing over the low level signal BEFORE amplifying the signal, often referred to as biamping or triamping, so called active crossovers split up the low level signal very accurately and then send them to the speakers that are capable of reproducing them. The passive crossovers in speakers (big caps and inductors) are getting expensive, as an example a 24db/octave so called Linkwitz–Riley passive crossover for a typical subwoofer at 200Hz would cost about $100 calculated here
ERSE - Crossover Calculator - Fourth Order 2 Way
but you could do the same thing with a few dollars worth of OP amps and a low level signal.


Modern advancements include time correction for each speaker, phase alignments, feedback suppression and adjustments for the rooms actual acoustics.

[km6xz]

Is this question related to the piezo HF driver as in the prior post? If so, the filter is not going to perform as expected without the designed load and reactance of a dynamic driver when loaded with a piezo HF driver.

[cbarrow7625]

Luckily you can put a resistor in series with the piezo (up to 50 ohms in some cases) to give it a more "normal" impedance curve so that it will work more like a "normal" driver where the crossover is concerned. A 10-20 ohms resistor in series with the piezo will typically not reduce the output level of the piezo while contributing the linearizing properties. If you need to reduce the piezo level you can use a pair of resistors to make an impedance-matched L-pad (voltage divider).

[Mark Hammer]

Making the boundaries between the content that goes to each driver less overlapping will often impose/require loss of efficiency, simply because one has to "bleed" low end to ground in order to not feed it to the tweeters/midrange, and bleed off treble to ground in order to not feed it to the woofer. A one-pole, simple frequency-divider may bleed off less audio signal to ground than a steeper 2-pole divider network.

That is not a major weakness, but it may require additional wattage capability from the amp in order to deliver the desired sound pressure levels. the tradeoff in permitting each driver to reproduce that which it truly excels at may be well worth it.

That said, the loss in efficiency is one of the many reasons why folks prefer an active crossover, rather than a passive one. Not only does the active crossover permit ALL the power of the amplifier to reach the speaker driver, but it is often easier to provide continuous variability of the crossover point/s, a simpler matter to produce much steeper and more selective frequency-division, and minimize phase-coherence issues.

[Steve Conner]

Yes, the Behringer DCX2496 digital crossover is very popular with DIY speaker enthusiasts. You can buy it for less than a pile of parts for a high-end passive crossover.

But if we're just trying to add a piezo horn to a 15" wedge or something, I think we're overthinking it. The whole point of those piezo horns is that they're cheap, and don't need a crossover, saving even more money.

I've owned a few bass guitar cabinets with horns, and I found that they sounded better with the low-pass part of the crossover bypassed, feeding the woofers full-range signal.

[tube power]

Once again to clarify, I have removed the piezos and put in titanium drivers.
I ordered the Dayton crossovers and I'll experiment with crossing and bypassing the woofer.

I just want to send as correct a signal as reasonably possible to each driver while also doing
what I can to protect them from damage.
This can be a complex science and I appreciate all the input in this thread very much.

How has live music ever gotten along without all the technology we are moving into?...

But the perfectionist in some of us emerges and we want as good as it can be, after all.

Now, how about adding a dome light bulb?...

[km6xz]

That what I was suggesting in a parallel thread regarding this system. Why waste a perfectly good,but lossy, passive cross over on a two way system that will work just fine without it, in fact be more efficient?
By not having the rest of the network connected( a dynamic driver) consisting of an equivalent inductor, capacitor and resistance in parallel the tuning of the network is going to change in both knee frequency and Q(slope).

[Steve Conner]

Well then, the Dayton crossover will work fine, provided the new tweets you bought have a crossover frequency of 3.5kHz or less. (Any tweeter you buy should have a datasheet/instruction sheet available, giving a recommended crossover frequency.)

You can try the woofer both through the lowpass part of the crossover, and full-range, and see which sounds nicest.

[TomCarlos]

MEF members ....

I recently read an article in a Parts Express Sales Catalog (just delivered)- "The Great Crossover Debate." I went looking for old threads here on MEF to read up on this and came across this one.

In the Parts Express article, it states the following:

"The greatest source of tweeter distortion occurs at and around the tweeter's resonant frequency (Fs). For this reason, the crossover point should be chosen to keep the tweeter from producing significant output at it's Fs. Classically, the phrase is to keep the crossover "double" the Fs, at least when using coming 12dB/octave slopes. An example of this: for a tweeter with a resonant frequency of 1,000Hz, the suggested crossover point should probably not be below 2,000Hz."

The Dayton crossover referenced by Tube Power (in thread #1) is specd at 3.5Khz.

In thread #2, Steve Conner mentions a 7K tweeter. Was that a coincidence?

I guess my question is... if you have a tweeter specd at 3.5K, would you use the Dayton crossover mentioned or would you go with a crossover specd at 2KHz or something like that (something below the tweeter resonant frequency)?

Thanks, Tom