When you ignore the crossover

[Pbassred]

Given a notonal 100W 2 way "full range" cabinet Crossed over at 1500hz, driven by a notional 100W amplifier....
I would expect that the components and drivers would be a match for the power fed through it, given that the power is distributed across the frequency range.

If I applied a high pass filter before the amplifier such that it only recieved frequencies above 2000Hz and drove it at full power am I correct in thinking that:
100 Watts hits the tweeter, - so its about to blow,
The crossover is doing little or no work, but is still using power.

Just trying to get it straight in my head

[Cal Weldon]

Originally posted by Pbassred
given that the power is distributed across the frequency range.

(Non-technical) If you can think that it takes a lot more power to move a big ol' woofer back and forth than it does a little lighweight tweeter, then you can see the power is not distributed equally. If it were we have to build some rather robust tweeters. The SPL will be distributed equally (ideally) but not the electrical power.

[i]If I applied a high pass filter before the amplifier such that it only recieved frequencies above 2000Hz and drove it at full power am I correct in thinking that:
100 Watts hits the tweeter, - so its about to blow,
The crossover is doing little or no work, but is still using power.[/B]

The two way probably has about a 15 watt tweeter crossed over so that it will take a 100 watts from the amp as it is crossed over at 1500Hz where there is less electrical power needed to do the job.

If you add the new filter in with the old, it will affect the final XO point. You really want to remove the initial XO and perhaps consider running the woofer straight from your new filter and upping the XO point of the tweeter. Then you will have a higher power handling.

If not:

The speaker will likely handle a tiny bit more, but not much, as the tweeter will only be crossed over a little higher. The woofer part of the initial 2 way will now handle lots more power but is not very useful as it used to have a high pass at 1500Hz and now has a low pass at 2000Hz (or whatever the combined frequency result. One would think there is some serious cancellation happening), so that does not make a lot of sense.

[i]Just trying to get it straight in my head [/B]

It never becomes fully straight, you'll forever have questions. That why these forums exist.

EDIT: Upping the XO point of the tweeter can only be done if the woofer can go that high as well and we haven't even touched on the beaming or baffle step issues.

[Pbassred]

hold up Cal. This is a fictional cab. It does not exist. So, there is no reason to "fix" it.

My question was really about:- what happens if you only amplify the frequencies above 2000Hz to an output power of 100W.

Its a dumb question I suppose.

[Cal Weldon]

OK that's more of a question for the amp people. Perhaps they'll take the lead.

[Cloth Ears]

Not sure if I've read the question correctly, but this is what happens when you use an electronic crossover. You can design a passive crossover to go before your amplifier - but you would be designing it based on your amplifiers' input impedance, not on your speakers.

Generally you wouldn't need to use a 100W amplifier for your tweeter, but hey, why not? On the other hand, if you were using 500W a side for your bass, then you'd probably want 200W a side for the mids and 100W a side for the tweeters - but I wouldn't want to sit in the room...

The 100W doesn't really matter unless you're heavy handed on the volume.

[Bose(o)]

Even with an op-amp there will be insertion loss, though with a simple circuit this CAN be negligible. I'd figure that the main "problem" would be with time delay between the tweeter and the woofer though, this may be negligible.

[Pbassred]

WHAT!!!

Guys,
This is probably too simple for you. It a theoretical speaker cab. Don't try and fix it. 100W is an easy number. ( actually, I play with P.A. systems, so its a tiny number, but FORGET the application because there is NO application. Its theoretical). Lets start again.

Take this theoretical 100W amplifier and feed the input with a signal above 2kHz. Drive the amp to its maximum before distortion.

This is connected to a (imaginary) full range cab with a xover set at 1.5kHz. i.e. the bass driver gets nearly nothing. Which leaves the tweeter.
Is it as simple as saying that 100W hits the tweeter - and freaks it?

and the the power consumption of the Xover, in this case, is neglegable?

[moamps]

Hi,
theoreticaly, it is perfectly same where is the crossover placed, before or after the amplifier.

If your tweeter can't handle 100W at 2kHz, it will be dead in both cases: 2kHz - crossover - amp - tweeter or 2kHz - amp - crossover - tweeter.

Regards,
Milan

[Volenti]

Originally posted by Pbassred


This is connected to a (imaginary) full range cab with a xover set at 1.5kHz. i.e. the bass driver gets nearly nothing. Which leaves the tweeter.
Is it as simple as saying that 100W hits the tweeter - and freaks it?

and the the power consumption of the Xover, in this case, is neglegable?

But you're not hitting the tweeter with 100w, you're hitting it with a limited bandwidth signal at a certain potential, it's the impedance of the tweeter within that limited bandwidth that determines the current that it draws from the amp, which is the power it draws.

Since the effective impedance of the tweeter is high at these frequencies it draws little current and dissapates little power, this means the X-over also can be lower power. (but still needs to be able to handle the voltage potential of the amp)