A question: I found some ISA series ampli with the switch set to "STEREO" and "BRIDGE MONO". I found on the manual that to obtain the bridge mono I should have "PARALLEL INPUT" and "BRIDGE MONO" engaged. What is the difference?

More: What will happen if I connect a speaker on the bridge outputs, but the switches are set to "STEREO"?
I know the answer (blow the speaker) but why?

Last: what is the meaning on a tri-amped system to have a BRIDGED ISA 450 for each HF and just one channel of a ISA 750 for each LF enclosures??

Both inputs are active. If you plug in a stereo source, the two inputs are combined. If the amplifier is strapped for Bridged Mono out, that is what you will have. A mono signal of the two combined inputs.

Mono output is across the two red output jacks.

The other two questions you have ... I don't know.

If you have a speaker connected in bridge configuration to an amp(using the L+ and R+ terminals), but the amp is set for non-bridge (stereo) operation, the speaker will reproduce the "difference" between the left and right stereo inputs. This will not damage the speakers, in fact it is known as a "Haffler Hookup" and has been used to get a crude surround signal when you don't have a surround decoder.

A tri-amped system needs 3 amplifiers. One for the LF driver, one for the MID driver and one for HF driver. I think what is meant by that statement is use a ISA450 amp in bridge mode for the MID driver, use another ISA450 amp in bridge mode for the HF driver and one channel of a ISA750 amp in non-bridge mode for the LF driver. I presume they are talking about a system using two LF drivers, so the other channel of the ISA750 would drive the second LF driver.

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Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

And connect a speaker to BRIDGE outputs with an amp set to STEREO with just one input used is not meant to blow a speaker? So why we are blowing a MF driver a day... ??

Tri amp. Isn't it better to use one half for HF, one half for MF and one bridged for LF?

I don't think that one 450 bridged amp is so useful for a HF driver in a triamped system, what do you think?

Yes, provided you are not using the right input.

"And connect a speaker to BRIDGE outputs with an amp set to STEREO with just one input used is not meant to blow a speaker? So why we are blowing a MF driver a day... ??"

Maybe you are driving the amp or speaker too hard.

"Tri amp. Isn't it better to use one half for HF, one half for MF and one bridged for LF?"

All you are doing is effectively reducing the power capability of the sytem. If you are not trying to blow the roof off, that would work.

"I don't think that one 450 bridged amp is so useful for a HF driver in a triamped system, what do you think?"

Depends on how much volume you are going for and the power handling ability of the HF driver. Assuming (and only assuming) an ISA450 produces something of the order of 900watts in bridge mode, not too many HF drivers will cope with that sort of power. So yes, one channel of a 450watt amp should be enough for the HF driver in a typical cinema system.

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Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

Thanks for your help.

Yes, the system can work in this way but I believe that it could be assembled better.

The could use one channel of ISA750 for HF and MF and one bridged 750 for each LF. I dont' have the specs right now but it seems a bit adequate for me. And the cost of the system would be approx the same.

Oh, we are talking of KCS speakers.

Blown MF: I clearly heard that MF distorcing once. But not always. If connecting a MF speaker to the bridge outputs at a stereo amp is not a problem, the amp could be defective... Otherwise the speaker should always distorce...

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Really? Does KCS has a Website?

Do you really think that the KCS are just copy of JBL, EV with just their design? I've heard their sound... They do not sound so well IMHO. They're fine but not comparable to JBL nor EV.
They're a bit harsh.

What do you think?

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I found the EQ almost good. I found the sound of KCS not comparable with JBL or EV. I do not believe that it is an EQ issue, but I can be wrong.

MF issue solved. Techs made the wrong settings to the crossover, the MF received 300Hz instead of 500!