Do I need a crossover?

Ron-P

Here is what I was told I need to do if I want to have "true" bi-amping.

...even though you are using 1 amp channel for each driver(woofer and tweeter), you are still sending the driver the full signal which then has to be filtered by the speaker's crossover network(either high-pass or low-pass). The only real way to biamp is to have a passive or active crossover between the pre-out and the amp, so as the high frequencies only go the the amp channel that will feed the tweeter, and the low frequencies go to the amp channel that will feed the woofer.

Step in here and enlighten me boys.


Peace Out~:D

RuSsMaN

Sounds like a good idea, if you want to remove the internal network in your speakers, otherwise seems like double-filtering to me....

I don't see what the real difference is, you filter outside the speaker cab before it hits the amp(as this post suggests), or inside it (as is from the factory), either way it is still filtered before it hits the driver. I don't see the point in doing both.

Maybe this guy has some reasoning behind this, only thing I can figure is that maybe the amps would perform/sound better (within a limited freq range), but he didn't say that, and I don't know that I really buy that....

Lets say it did make a difference, I think the cost would be high, for little if any performance gain.....

I say your bi-amped, period. But hey, I'm a mouth breathin' cloven-hoof ****, so what do I know....

Ron-P

I thought exactly the same thing, but was not 100% sure. You confirmed my thoughts exactly. I'm gonna send a reply off and see what kind of response I get. Thanks Russ.


Peace Out~:D

RuSsMaN

Hole up there Ron, I know some other mofos will have thoughts on this, let it ride for a little while....

Cheers,
Russ

nascarmann

You are bi-amping.....at least here in the **** hills were i'm from you are bi-amping! But I'm a mouth breather as well....:D

Ron-P

Here is the remainder of his comments. Which might have some validity.

Ron, when you bi-amp that way you are still giving the amp the burden or trying to reproduce a full-frequency signal while only the speaker has the ability to filter out the signal to the appropriate driver. For example, some tube amps have incredible mid and high clarity and smoothness, while the low end can be slow and sloppy, which in turn may electronically speaking effect the mids and highs coming out from the amp by making them a little less focused and dynamic. So when you feed a full range signal from the preouts to the amp, then the full range signal from the amp to the speakers, the mids and highs will be affected by the sloppiness of the lows, and this high and mid signal will be filtered through the speaker's crossover and sent to the tweeter as such.

Just seems no matter how you filter, you are filtering which is completely different from biamping. So there is a bit more strain on the amp for receiving a full signal vr. not.


Peace Out~

RuSsMaN

All that is well and good, what he said. But even if its valid, you aren't running tube amps, you are running solid state Adcoms, and they are 20-20K .08thd at full power. I don't know of any issues there....

Why would lows automatically be sloppy? And when does this sloppiness start? 2000Hz? 200Hz?

And on a final note, get a ballpark price from this guy, that will probably be the 'ender' to this discussion right there....

Cheers,
Russ

hoosier21

Ron

I had the same idea this guy has, you are "wasting power" or whatever, but I was then told if the "full signal" is not being produced by the speaker driver(s) the amp is hooked up to, the amp is not DRIVING the complete signal.

By sending the full range signal from pre-amp to power amp, the potential is there for you to use say 40 watts, BUT your tweeter is only reproducing 10 watts worth of the signal, the 30 watts are not wasted, it was never produced because the load was not there for the amp to see in the first place.

It is kind of like electricity it is available to all your outlets in your home, the potential is there, but without a load, it sits idle.

Now, can it be said the unused signal is piling up somewhere in the path, either at the preamp output stage or something, and causing distortion?? I will bet it is as good of a debate as the speaker wire and interconnect subject.

Somebody correct me if I am wrong on above she-at, MHL is well into the bloodstream.

Ron-P

I'm with you guys all the way on this. I think this guy might be talking out his **** just a tad.

I am bi-amped there is not doubt. The only difference I can see by going external on the crossover is to take some load off the amp, that's it. It might help, it might not.

Russ, I got your email, thanks!

Anyway, I replied with some pretty decent comments and questions which includes all that has been discussed above. I'll see what he says and post it.


Peace Out~:D

madmax

Ron,
I have a crossover I sometimes use with the SDA's and two amps. This doesn't work well for me because the SDA xover has a large freq overlap and the xover I have has no provision to overlap the xover frequencies. I tend to like it until I take it out of circuit then some aspects seem better. Your system is different though. One thing to keep in mind is that if the xover in the speaker is calling for certain frequencies then the amp is not trying to reproduce the others. What the xover in the speaker does is to raise the resistance for freqs other than what is being passed to the speakers which causes the amp not to work at trying to reproduce them. I'm not saying the guy is wrong. He is correct. The point is that the amp is trying to reproduce the freqs slightly and the external xover eliminates this altogether. Can you hear the difference? Possibly. In my opinion until you move much further up the food chain it is not an issue.
madmax

Aaron

That guy's so full of **** it isn't even funny.

Aaron

goingganzo

that is so funny the network olny lets sertan fr throgh so that is where the power is made also some amps produce bass beter than other and some strugle on the higher as the fr changes the restance the amp changes this a 2 cents to a dollar if you filter the sigonal befot the amp you can get some othre fr than what you want after the filter but if you filter at the speaker there is less of a chance fo getting more fr than what is wanted for the speaker

RuSsMaN

Originally posted by goingganzo
that is so funny the network olny lets sertan fr throgh so that is where the power is made also some amps produce bass beter than other and some strugle on the higher as the fr changes the restance the amp changes this a 2 cents to a dollar if you filter the sigonal befot the amp you can get some othre fr than what you want after the filter but if you filter at the speaker there is less of a chance fo getting more fr than what is wanted for the speaker

What?


Cheers,
Russ

goingganzo

maybe i had 1 to many too drunk

HBombToo

Ok guys let me try here.... I don't wan't to get into alot of equations but I can prove mathimatically hoosier21 statements except his mention of, "Pile UP???". I don't understand Pile Up?

Put simply a speaker is an RLC circuit and based on the values of C, L and R will determine the current draw at a certain frequency and over a range defined by the Q of the circuit. So tweeters are hipass and drivers are low pass circuits. Q is the -3dB point around the center frequency of the high/low pass circuit.

When we don't bi-amp, have the strap across high and low, the single amp must provide the power across the entire band, say 20Hz to 20KHz or 2 Q's. Now when we remove the strap, what we have done is effectively separated the band between high and low because the response of the drivers verse the tweeters are low and high pass respectively or separate the Q's.

Just for the sake of arguement, lets say drivers have the band from 20Hz- 10kHz and the tweeters are in the band 10kHz-20kHz. So by splitting the band we draw less power overall from the single amp because the load is only over 1/2 the spectrum or a single Q for that individual RLC circuit. Drivers consume more power than tweeters so from a single amp driveing say 2 Q circuits the low pass circuit could consume enough of the amp resource that the mid range or high's get muddied up because there is not enough power in the amp to drive or handle both.

Mr. DiComo of Polk in the last news letter argued that without removing the internal crossovers from the speakers that this configuration is "half baked" but is still bi-amping and the former in my mind is for the hard core audio file. Let me argue that as well as the Polk Speakers work and the amount of engineering that went into the cross over circuit, why would I, an engineer, want to re-engineer a good thing. If we removed the crossover I bet we would spend an enormouse amount of time trying to get the speaker to sound like it did before we removed the cross over circuit. I think that by adding an additional Amp we have ensured that enough power is applied to each of the passbands without any stress at all on the Amp.

This is the way I see it.
Now you can kick my **** lol

Hbomb

madmax

Lets be picky here. Audio file is really audiophile. Tweeters are typically crossed over at around 3K and tweeters as well as woofers are considered drivers. I am not sure 2Q means anything. Also, Q is the slope of the response, not the 3db down point. Both a high Q and a low Q circuit have an associated 3db down point. Just facts dude.
madmax

madmax

Originally posted by goingganzo
maybe i had 1 to many too drunk

Me too, but who's counting?
madmax

mantis

This is one crazy post.I think I'm gonna leave this one alone......way 2 out there.

RonP,

Have you tried just running your speakers with only one Adcom amp?Then did your bi amping thing and listened for the differences?
If without trying to be manly or what have you....what sounded better?
Thats what reallty matters....engineering a crossover to match and all that other s#$T that was said in here ...forget about it man.Go listen and enjoy.

mantis

To simply answer the orginal question.............NO PERIOD.

nascarmann

Both a high Q and a low Q circuit have an associated 3db down point. Just facts dude.

But it is rated....is it not?

HBombToo

OK Madmax001, you busted me on the audiofile thing and I appreciate you pointing it out but forgive me because I can't splell or tpe to good. Really though... I don't give a ****.

Lets not get to picky regarding actual frequencies here because the values I was using was for illustration only!

And it seems as though you like to get into some term tossing overthere so let me help you out... I was only referring to a bandpass and the Q of the bandpass is defined as Q=Fc/(Fh-Fl) where Fh and Fl are high and low freqs 3dB down from the center Fc.

I hope this help you out and yes I agree with Mantis... An external crossover is not necessary.

HBomb

HBombToo

Oh... BTW, all I meant by saying 2 Q was 2 different bandpass's.

Ron-P

My favorite answer so far.

To simply answer the orginal question.............NO PERIOD.

Peace Out~:D

Ron-P

Oops and to answer your question mantis. I did, sorta.

I wired up the right channel using a speaker wire jumper. I kept the left channel bi-amped. I then did a test between the 2 channels (using the balance dial). It did not sound as good. I'll elaborate later as I am really tir.........ZZzzzzzzzzzzzzz.

madmax

Originally posted by HBombToo
And it seems as though you like to get into some term tossing overthere so let me help you out... I was only referring to a bandpass and the Q of the bandpass is defined as Q=Fc/(Fh-Fl) where Fh and Fl are high and low freqs 3dB down from the center Fc.

HBomb

That is for a bandpass filter! Toss the right terms at least. There is no Fc for high and low pass circuits. OK, I'll admit the audiophile thing was a hit below the belt though. Sorry, just had to throw it in with the rest.
madmax

mantis

RonP,
I'd like to hear your results.After you wake up of course.

Doesn't drinking water the next day help?

ShrinkMan

I searched on "Biamping" and "Active Crossover" to get here and came up with three threads to read. I read this one first and felt pretty good about biamping my LSi-15's with two matched Denon POA-1500 power amps straight from my Yamaha C-85 Preamp without the necessity of an external active crossover.

Then I read the other 2 posts, both from the car audio forums, and each biamp post question having only a single response, both from a Polk Customer Service "Agent" named Kim insisting that active crossovers (or additional in-line passive crossovers) are required to biamp the questioners' car speakers.

What's that all about??!! Are car systems that different, or does Polk have an "official position" on the biamp/crossover question... or is "Kim" running her own confused agenda?

Any new help on this age old question?