Bi-amped Cornwall III's

[Trey Cannon]

Using the attached schematic to discuss (this is not the cornwall III schematic), when the bi-wire jumpers are removed (the 2 x's), you are seperating the woofer low pass section from the squakers bandpass and tweeters high pass section. If you send full range sound to both the LP and the HP section, there is no place for the HP signal you sent to the LP section to go, as well as no place for the LP signal you sent to the HP section to go. This results in an abnormally high impedance load seen by your 2 amps. On some SS amps, loads grater than 16 ohms, can cause some damage.

Well, In my world, most every speaker I have or work on, has impedance peeks of as much as 100 Ohms. In fact, I am glad of this. I am glad because when the speaker has 100 Ohms of Z@ > Fc of the network will make my amp very happy. At 100 Ohms my amp will only allow as much as 0.92 Volts. Knowing that my am is able to give as much as 32 Volts rms, that 0.92 Volts will be easy. The current at that time will be only 0.0092 Amps. I am sure the amp I have knows it will have a speaker connected to it, therefore, it is ready for that.

Would you like to see what the impedance curve of a LPF connected to a woofer?

[jackpod]

What is so difficult about using an active xo? they are not voodoo

[Trey Cannon]

The hard part is knowing what you have done.

1. If you are to use an active xover, you must set the xover points, for the most part, from marketing numbers. Most folks have no way to test the outcome. So you never know what you will get.

2. If you remove the passive network, you will have no driver protection. You could send to much power to a part and kill it.

3. If you don't remove the passive network, you will be changing the slope of the xover. This is not bad all the time, but it will change the speaker from what was intended.

That's just 3 points. There are others.

[jackpod]

Ok, I am just going to calmly walk away from this thread, bite my toungue and let you believe what you want to believe

"You could send to much power to a part and kill it." I don't know who you think you are talking to here, but ... None of your points .. oh nevermind

[Guest " "]

jackpod

I agree.

They have been given info under advisement.

There is probally some intellectual property information that we do not have acess to, that would change our perception of this issue (swamping resistors, damping resistors, etc).

Most understand the flexibility of active crossovers and the advantages the reduction of in-line componets that exist in passive xovers offer.

I remain concerned, ( have not seen any impedance plots of either the HF ot LF section with the bi-wire jumper removed) about the abnormal load passive bi-amping with out the use of active crossovers places on amplifiers.

Otherwise, my opinions have already been contributed.

Here are some sample reactance numbers for passive xovers used in the manner we are dicussing. Note that at 40hz, the amp attatched to the HP section will see 306 ohms if no active is used.

For capacitave loads

assume capcitor of 13uf

-assume an amplifier connected to a HF section of a bi-wire network with no bi-wire jumper and no active xover.

-capacitor is a sample capacitor value for a 3-way xover

-frequency is the part of the sound band which we would like to know the reactance in ohms.

capacitor frequency reactance remarks

13 800 15 ohms normal

13 400 30 ohms normal

13 100 122 ohms abnormal

13 80 153 ohms abnormal

13 70 174 ohms abnormal

13 60 204 ohms abnormal

13 50 244 ohms abnormal

13 40 306 ohms abnormal

Inductive reactance on the amp attached to the LF section passive xover with out active xover.

-assume 2.5 mh inductor

-frequency is the portion of the out of band HF material being blocked by the LF passive xover

- reactance is the load seen by the amp at the indicated frequency

-remarks indicates if normal or abnormal

inductance frequency reactance remarks

2.5 mh 300hz 4.7 ohms normal

2.5 mh 1000hz 15 ohms normal

2.5 mh 5000hz 78 ohms abnormal

2.5 mh 6000hz 94 ohms abnormal

2.5 mh 7000hz 125 ohms abnormal

2.5 mh 9000hz 141 ohms abnormal

2.5 mh 10000hz 157 ohms abnormal

2.5 mh 11000hz 172 ohms abnormal

2.5 mh 13000hz 204 ohms abnormal

2.5 mh 15000hz 235 ohms abnormal

[jackpod]

Speakerfritz,

I can't help but shake my head. First if someone doesn't or can't understand the operation of an active xo, they aren't going to know or want what bi-amping has to offer.

only a few of the active xo's out there allow excessive overlap of the bands, from an electrical standpoint it requires duplication or triplication of the circuits, most simply give you a variance of where the crossover point is with individual gain controls for each segmented spectrum.

There is a big difference in momentry impedance fluctuations (which are present in all "properly" loaded amplifiers) versus constant impedance mismatch such as would be in the described method of "passive" bi-amping I guess is what you would call it

Like I said I need to just walk away from this one...

[Guest " "]

jackpod

I agree, walking away as well.

Anyone who wants to put a constant reactive load of 306 ohms at 40hz on their amp attached to the HF section and 235 ohms at 15000hz on the amp attached to the LF section should first check with the manufacture of their amp to see if their amp can handle abnormal inductive and capacitave reactive loads in the abnormal range indicated below.

[audiobliss69]

Oh, my; now I'm thoroughly confused! And concerned, since I'm biamping my RF-35!

I've been thinking for quite a while that it doesn't make any sense for

my HF amps to be receiving and reproducing the full frequency range,

while my LF amps are doing the same, while they're only actually

needing to provide one or the other. I've not liked that idea as

I see it as being unneccessary. However, I had never thought

about it actually having ill-effect on my amps.

Can someone a little more succintly explain what's going on here?

I see that using an active XO would do away with any concerns, but then

I like having as little as possible in the signal path. Also, I

don't want to worry with removing passive XO's in my speakers; I don't

really want to do anything to them except listen to them! Could I

place an active XO in front of my amps? Would that affect

anything?

Sincerely,

confused

[Guest " "]

"Could I place an active XO in front of my amps? Would that affect anything?"

Thats the place to put an active xover.

[Steve Donalson]

Hahahaha I love all the sample #'s and assumptions. One thing you guys keep forgetting is the amount of current at higher impedance loads. It goes DOWN. So far down, that it's meaningless. You can twist, add #'s however you like, but in a real world situation, this poses no problem.

Solid state amps love to run with no load, but can be damaged by a short or very low impedance load. I think you guys are confusing solidstate amps and tubes.

It's true that the passive xo will present a very high impedance load into the amp for freqs below the cutoff for the hp, and above the cutoff for the lp. This is of ABSOLUTELY NO consequence, because as previously stated, solid state amps operate perfectly well with high impedance or even open circuited loads.

Have you guys ever seen a solid state amp. damaged from passive bi-amping? Now, not an amp that had a problem and happened to be in a bi-amp configuration, but to be harmed from bi-amping? We haven't... and..we've no amps or speakers to passively bi-amp around here... hahaha

[Guest " "]

Steve Donalson

How about some impedance plots posted for a LF section and a HF section with out the bi-wire jumper installed.

Also, please don't invite character judgements or attacks, would rather have the impedance plots.

[Steve Donalson]

I didn't make any attack or pass judgement...

Let me see what we can do about some curves.

[Trey Cannon]

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

<?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" />

Trey Cannon

Engineering Product Designer

Klipsch Audio Technologies

rb25 z.doc

[Trey Cannon]

FYI:

I have been using active xover in live pa, car audio, for more than 20 years.

I use active xover to design new product here at klipsch.

If you can find a solid state AUDIO amp that will have problems with load impedances in the hunderds of Ohms, I will buy you lunch and tell you that your amp is junk.

BTW: no solid state amps were harmed in the testing of this speaker.[]

[Trey Cannon]

jackpod I agree. They have been given info under advisement. There is probally some intellectual property information that we do not have acess to, that would change our perception of this issue (swamping resistors, damping resistors, etc). Most understand the flexibility of active crossovers and the advantages the reduction of in-line componets that exist in passive xovers offer. I remain concerned, ( have not seen any impedance plots of either the HF ot LF section with the bi-wire jumper removed) about the abnormal load passive bi-amping with out the use of active crossovers places on amplifiers. Otherwise, my opinions have already been contributed. Here are some sample reactance numbers for passive xovers used in the manner we are dicussing. Note that at 40hz, the amp attatched to the HP section will see 306 ohms if no active is used. For capacitave loads assume capcitor of 13uf -assume an amplifier connected to a HF section of a bi-wire network with no bi-wire jumper and no active xover. -capacitor is a sample capacitor value for a 3-way xover -frequency is the part of the sound band which we would like to know the reactance in ohms. capacitor frequency reactance remarks 13 800 15 ohms normal 13 400 30 ohms normal 13 100 122 ohms abnormal 13 80 153 ohms abnormal 13 70 174 ohms abnormal 13 60 204 ohms abnormal 13 50 244 ohms abnormal 13 40 306 ohms abnormal Inductive reactance on the amp attached to the LF section passive xover with out active xover. -assume 2.5 mh inductor -frequency is the portion of the out of band HF material being blocked by the LF passive xover - reactance is the load seen by the amp at the indicated frequency -remarks indicates if normal or abnormal inductance frequency reactance remarks 2.5 mh 300hz 4.7 ohms normal 2.5 mh 1000hz 15 ohms normal 2.5 mh 5000hz 78 ohms abnormal 2.5 mh 6000hz 94 ohms abnormal 2.5 mh 7000hz 125 ohms abnormal 2.5 mh 9000hz 141 ohms abnormal 2.5 mh 10000hz 157 ohms abnormal 2.5 mh 11000hz 172 ohms abnormal 2.5 mh 13000hz 204 ohms abnormal 2.5 mh 15000hz 235 ohms abnormal

Here is the Z of a raw woofer. This is a 6.5 inch sub driver with the Z of the test leads removed. Note that the woofer only has 100 Ohms of Z at its highest point WITH NO NETWORK. This woofer will reject High frequency. Are you telling me that if I hook a SS amp to this raw woofer I can damage my amp?

HOW?

As the Z goes up the current and voltage (I and V) goes down.

IN RF (radio frequency) rejection is a point of intrest. IF you have more than 1 % you can damage the output amp. BUT, we are working with audio not RF. There is no SWR to worry about in a audio amp.

<?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

raw woofe z.doc

[Trey Cannon]

Ok, I am just going to calmly walk away from this thread, bite my toungue and let you believe what you want to believe

"You could send to much power to a part and kill it." I don't know who you think you are talking to here, but ... None of your points .. oh nevermind

Walking away may be a good Idea.

What I am talking about is that some speakers have protection against over powering built into the passive xover.

If you were to connect the amp to the HF driver with no xover using active xover in front of the amp, you will only send HF to the amp. BUT, IF the amp has more power than the HF driver can take you can still blow the driver. 100 Watts into a K-77 and K-55 even from 400Hz and up can still blow the drivers.

How do you think power testing is done?

[jackpod]

I'll be sure to never patronize your place of business, your childish nature must be in direct proportion to your age. I have seen amps damaged by just such stituations, but I am not going to get into this discussion with an inexpereinced kid

Bye~~~

[Trey Cannon]

<?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /> Notice that as the Z goes up current goes down. Not that there was much current to start with.

BTW: this was ran at 5 V.

woofer with 2 poll LPF.doc

[jackpod]

Above comment directed to steve donaldson

[Guest " "]

"Trey Cannon"

I think your confusing normal impedance which exist in a resistive load which is capable of dissipating power with reactive loads (i.e. inductive or capacitive) created when you introduce blocking inductors and/or capacitors which do not dissipate power and can only be reflected back into the amp.