bi-amping components correctly?

I'm in the design phase of my system and at this point, time is a luxury since $$ isn't. I've read a little on bi-amping and from what I understand it is the best way to achieve better SQ from your component speakers. This is what I think I have learned, bi amping cuts down on the stress to your amplifier by allowing it to "concentrate" on a limited frequency. The result is better signal reproduction with less chance of wave clipping at high levels.

Is that an accurate, yet very basic, depiction of bi amping? Please correct me if I'm wrong.

Also, I dont really have a full understanding of how to calculate the best wattage distribution for the mid-bass/tweeter speakers. Apparently my mid-bass/tweeters have identical sensitivity levels of 90db (1w/1m), but doesn't the crossover freq make a difference? They are rated at 125rms/side so does that mean 62.5w to each using the supplied crossovers? If the supplied crossovers are taken out, then what?

Here is a link to my speakers

https://www.polkaudio.com/car/product.php?name=mmc6500

I'm not asking for someone to tell me what to go buy, I want to learn this so that I can figure out what to go buy, for this application and others down the road.

I acquired my info from this page, but I had a hard time understanding it. https://sound.westhost.com/bi-amp.htm

Thanks........

You have a good beginning grasp, and Elliot's article (your second link) is a fantastic resource.  Look about 2/3 the way down that page and there is a chart of amplifier power relative to crossover frequency.  This will show you how to size your amps for the woof-mid-tweet.

The absolutly most important component in a bi-amp setup, IMO, is your crossover.  What crossover are yu planning to use?

Alright, I will look into those. An external crossover in line to the amp is going to completely replace the passive crossovers that were supplied with my speakers, correct? My job is just to match the frequencys to those of the original crossovers right?

For the sake of making things a little easier, is it safe to change the crossover freq. in order to balance the power to each component? I could use a 65w x 4 amp rather than a 100 x 2 and a 25 x 2, by setting the crosover at about 350hz. But is this safe for my speakers or do I need to stick with what the manufacturer frequency?

Thanks again......

You don't gain the key benefits of bi-amping if you still use the passive crossovers. 

Some folks, DYohn included, like the voicing of passive crossovers.  Cool, great, wonderful.  I have absolutely no arguments against that.

However, this is NOT the type of bi-amping the Elliot article and others about true bi-amping are talking about.  Again, if you use the passive crossovers you lose just about all benefit of bi-amping. 

(Unless you do some sort of hybrid thing like haemphyst was talking about on that linked post.  I've never tried anything like that, so I can't speak to how effective it is.  My knee jerk reaction is that the different crossover points and the both active and passive crossovers might cause some phase problems that interfere with the very voicing we're trying to maintain... but I'm a noob when it comes to passive crossover design, so I'd like to hear DYohn's, Stevdart's, and Haemphyst's opinions on this).

kfr01] wrote:

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You don't gain the key benefits of bi-amping if you still use the passive crossovers.

Some folks, DYohn included, like the voicing of passive crossovers. Cool, great, wonderful. I have absolutely no arguments against that.

However, this is NOT the type of bi-amping the Elliot article and others about true bi-amping are talking about. Again, if you use the passive crossovers you lose just about all benefit of bi-amping.

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kfr01] wrote:

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p>(Unless you do some sort of hybrid thing like haemphyst was talking about on that linked post. I've never tried anything like that, so I can't speak to how effective it is. My knee jerk reaction is that the different crossover points and the both active and passive crossovers might cause some phase problems that interfere with the very voicing we're trying to maintain... but I'm a noob when it comes to passive crossover design, so I'd like to hear DYohn's, Stevdart's, and Haemphyst's opinions on this).

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deocder wrote:

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Another advantage of using the passive crossover is DC current protection. I'd hate to burn up my tweeters because of a DC transient introduced while turning the amp on or off.

Elliot provides a protection schematic here. Has anyone used something like this in their system? Is it overkill? Has anyone ever fried their tweeters because they did not use a protection circuit?

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This is a good discussion.  In general, here's my opinion.

For car audio where the gear is relatively cheap and available, it is easier to use a full-active system.  Although I am a proponent for passive crossovers (and it is their "dirt" than gives them much of their character!) in cars it is easier to setup and easier to get 'right" to use active crossovers on the pre-amp side.

In homes and in HT, I prefer to use passive crossovers with bi- (or tri-) amp setups.  It can create a much warmer (i.e. dirty) sound and you can compensate for specific driver shortcomings with a few clever circuit tweaks that are simply not possible - or not easily possible - with active crossovers.  In cars these little peaks and valleys are largely not noticable since a car is a terrible place for critical audio.  But in a theatre they jump out and smack you on the head, so passives are the better choice to compensate for them.

Damping Factor = (Load Impedance) / (Output Impedance)  load Impedence is the loudspeaker SYSTEM Z and Output impedence is the output impedence of the amplifier (usually normallized at 1Khz.)  Load impedence is the total load presented at the amplifier teminals, including crossover, loudspeaker voice coil(s) and speaker wire.  DF has no real meaning above 1200Hz..

Damping (AKA cone control) is critically important in low-frequency systems where accuracy is the desired outcome.  Too low DF will result in "flabby" sounding bass with a LF rise in both impedence and distortion and loss of definition below about 100Hz.  A completely un-dampened speaker system will easily exceed the woofer's mechanical limits and cause it to "bottom out" and can fry a voice coil.  HOWEVER, a damping factor of 10 or greater is really all that is needed. 

Since even the crappiest car stereo amplifiers have output impedence of no more than 0.25 ohms, a load impedence of at least 2.5 ohms creates a DF of 10.  Higher load impedence and/or lower output impedence creates better DF.  But paying a ton of money (or sacraficing power utilization) to create very high DF numbers is largely meaningless and a waste of money.

haemphyst wrote:

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kfr01] wrote:

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However, this is NOT the type of bi-amping the Elliot article and others about true bi-amping are talking about. Again, if you use the passive crossovers you lose just about all benefit of bi-amping.

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kfr01, I am just curious, though... what about the(se) article(s) make(s) you suggest that one or the other of the articles is not what the OTHER article is talking about?

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Did I suggest that one article was different than the others?  I threw the modifier "true" in there simply to distinguish it from the "bi-amping" that home audio manufacturers talk about with their 5-way binding posts that still use the passive crossover.  I wasn't trying to say anything more.  I realize that wasn't the greatest sentence in the world - I didn't get much sleep this week. 

haemphyst wrote:

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kfr01] wrote:

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/p>

(Unless you do some sort of hybrid thing like haemphyst was talking about on that linked post. I've never tried anything like that, so I can't speak to how effective it is. My knee jerk reaction is that the different crossover points and the both active and passive crossovers might cause some phase problems that interfere with the very voicing we're trying to maintain... but I'm a noob when it comes to passive crossover design, so I'd like to hear DYohn's, Stevdart's, and Haemphyst's opinions on this).

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Generally speaking, I would go one way or the other as well, but I was just trying to suggest one possible way of getting a few benefits of both worlds. There is no free lunch, we all know this, but in some cases there may be a cheap lunch, and a few trades in one direction or the other might account for an acceptable "loss".

Passive crossovers are dirty places, and generally, I do not like to go there. I am a very strong proponent of active crossovers, and now that I have used digital active crossovers, I'll probably never go back. The WORST of the crossover distortions (primarily phase angle distortions) can be easily fixed, by simply reversing wires at the driver or the amp. (The rules following are applicable to both active (analog only - not digital) and passive components.) EACH 6dB of crossover slope on the high-pass will be a +90°, and EACH 6dB of crossover slope on the low pass will be a -90°. In this case, though, a plus does not cancel a minus out. They are still additive, so if you have a tweeter and a woofer, each at 6dB slopes, one the tweeter will be 180° out of phase from the woofer - which can be fixed by reversing the wires on the tweeter - voila! back in phase. For each 180° of phase, all you have to do is reverse the leads again.

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Very nice explanation.  I haven't seen the above paragraph said so succinctly.  I've also seen the articles on damping factor you posted. 

So, here's tangential question for you all that I've been curious about.  If damping factor doesn't matter, and if tiny levels of thd are inaudible, what other criteria should be looked at to evaluate amplifiers?  Intuition tells me that next to nothing is gained from buying very expensive amplifiers.  Is this true?  How and in what way do expensive amplifiers produce better quality sound? 

deocder wrote:

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Wow! Great stuff! I had no idea about the phase shift relative to the crossover slope. I wonder if manufacturers of passive crossovers take this into account, since phase is also relative to the position of the speaker. There are are so many variations possible....

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deocder wrote:

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I chceked out the specs on my amps....not sure how they rate in the scheme of things though.....not that it matters at this point, they are definitely being installed.

S/N - >100 dB
DF - >400 at output connector
Slew rate - >30 V/us

At lease they were listed...

I'm not to clear on weather or not you guys use something to protect the tweeter when using an active crossover system. Could you clarify?

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deocder wrote:

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Also, are there active crossovers that have variable phase adjustability? I'll search for the answer, but if so, do you find that beneficial?

I feel like i'm digging way deep into the particulars..... I guess thats the perfectionist inside me though.

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