KPT-684 impedance

[Giorgio Volpi]

Hi, I have a dude about the SW KPT-684: the tech sheet talk about 8ohm impedance, but I think the 8ohm impedance is referring to each speaker, and the SW is 4ohm impedance. Please let me know what is the real impedance. Thanks a lot, Giorgio.

[twistedcrankcammer]

Hi, I have a dude about the SW KPT-684: the tech sheet talk about 8ohm impedance, but I think the 8ohm impedance is referring to each speaker, and the SW is 4ohm impedance. Please let me know what is the real impedance. Thanks a lot, Giorgio.

Giorgio

The KPT-684 is 8 Ohms per woofer at 400 watts per woofer. The Woofers are not wired in parralel, they both have individual positive and negative terminals at the terminal strip, on top of the unit. You could wire both woofers in paralel at the terminal strip for a 4 Ohm load, if that is what you wanted to do. I just use a sub woofer splitter cable and run a 2 channel amp into my KPT-684.

Roger

[Chris A]

When the 684 woofers are wired in parallel (i.e., lowest impedance), the minimum impedance is 3.6 Ohms at 22 Hz. The maximum impedance in this configuration is 27 Ohms at 45 Hz.

Chris

[RRFL]

Hi, I have a dude about the SW KPT-684: the tech sheet talk about 8ohm impedance, but I think the 8ohm impedance is referring to each speaker, and the SW is 4ohm impedance. Please let me know what is the real impedance. Thanks a lot, Giorgio.

Giorgio

The KPT-684 is 8 Ohms per woofer at 400 watts per woofer. The Woofers are not wired in parralel, they both have individual positive and negative terminals at the terminal strip, on top of the unit. You could wire both woofers in paralel at the terminal strip for a 4 Ohm load, if that is what you wanted to do. I just use a sub woofer splitter cable and run a 2 channel amp into my KPT-684.

Roger

The 684 can be driven in 16ohm configuration also. We do it with a bridged amp and get excellent results.

It is not recommended to drive each woofer with separate amp channel as you will have phase errors from the amp. The 2 channels will not match exactly so the woofers will not move exactly together and since they are in the same enclosure the overall performance will be reduced. In some cases this is considerable. It is better to drive the speakers in 16ohm with the amp bridged. If the amp cannot be bridged then use only one channel as you will likely get better performance. There is no amp made regardless of price that will have exactly matching channels and the miss match is greater with the less expensive amps.

[mark1101]

So as opposed to wiring the 2 woofers in parallel and using a bridged amp..............you wire in series and used a bridged amp? So the difference is either around 3-4 ohms or around 16 ohms. Is this correct? Why use series over parallel? Advantages?

I will have a pair of 684s next week and have to go through this, so I might as well learn today.

I have a single QSC 1804 and will be using stereo subs. I.E. one on the left Ch. and one on the right Ch. My processor will feed the amp 60 hz and below. So my choices are to wire the woofers in each cabinet in either series or parallel. Hence my question.

Thanks

[RRFL]

So as opposed to wiring the 2 woofers in parallel and using a bridged amp..............you wire in series and used a bridged amp? So the difference is either around 3-4 ohms or around 16 ohms. Is this correct? Why use series over parallel? Advantages?

I will have a pair of 684s next week and have to go through this, so I might as well learn today.

I have a single QSC 1804 and will be using stereo subs. I.E. one on the left Ch. and one on the right Ch. My processor will feed the amp 60 hz and below. So my choices are to wire the woofers in each cabinet in either series or parallel. Hence my question.

Thanks

The amp used was a Yamaha P4500 and the bridged load spec was 1240watts into 16ohms nothing less according to the manual.

Yamaha offered a special showcase deal and the P4500's were replaced by newer equivalent models rated for 4 ohm bridged, can't remember the numbers of hand but, bridged with the 684's at 4ohm 3200watts we felt the old amps were better so experimented with 16ohm probably getting 1200 - 1300watts and it sounded better so that's the current configuration..

I suspect the amplifier damping improved and that made the difference. "Cleaner Depth" There are four 684's end to end across the width under the stage. They are cemented in position so the stage is poured onto the cabinets and the dance floor is level with the side of the cabinets. The power available makes me feel sick and I always wear ear plugs.

[RRFL]

Considering this further some clarification might be necessary.

The P4500 bridged is rated minimum load 16ohms.

A QSC PLX1804 is designed for stereo purposes only. A pair 684 should be wired to 4ohms each cabinet and driven one cabinet per channel. Providing the speakers with 800W @ 4ohms load.

This amp is not rated for Bridged operation. There is insufficient amplifier power available to make it worthwhile experimenting with 16 Ohm load in this case.

[Giorgio Volpi]

Thank you very much to all of you for the tips.

It seems the better way is connecting the two woofers in serial mode at 16 ohm load. For this channel I have a QSC MX3000a amplifier, with 1600W power at 16ohm in bridged mode. The power connection is with 2 AWG#10 cables. I think all is Ok in order to work fine with no problems.

The screen is working with Digital 3D projector.

If someone have to teach something more to me, I will be very gratefull.

[RRFL]

Thank you very much to all of you for the tips.

It seems the better way is connecting the two woofers in serial mode at 16 ohm load. For this channel I have a QSC MX3000a amplifier, with 1600W power at 16ohm in bridged mode. The power connection is with 2 AWG#10 cables. I think all is Ok in order to work fine with no problems.

The screen is working with Digital 3D projector.

If someone have to teach something more to me, I will be very gratefull.

Yes I would wire for 16ohm in this case also as you are using the whole amp for one speaker cabinet.

It is also possible that the Distortion Specification will improve as the 4ohm spec is 1% @ 1K. and 8ohm is much better.

You will also notice that the Distortion specs on the QSC are generally 10 times better across the board when the amp is running at 1/10 of full output i.e. -10dB.

Since your amp has double the speakers power available @ 16ohm and the speakers are very sensitive it is likely you will operate at below 1/10 of full output in your home and the result will produce very very low distortion with breathtaking ease and grace.

[Coytee]

Interesting stuff to a dummy like me.

Question (and this is just for theory & kicks, to see what the answer is, I'm not thinking about it)

The Jubilee bass bin has 2 drivers, each one comes to the terminal block.

I think they're wired in parallel (+/+ and -/-)

What would happen if they were put in series?

(remember to take any technical comment and dumb them down to a 5th grader level)

[mark1101]

Yes, thanks. In my case with only a PLX 1804 I will be wiring woofers in parallel so each amp channel powers both woofers in a single cabinet at ~ 4ohms per Channel. Should be fine. I already do that now with my MWM cabinets and a QSC PLX 1104.

[Chris A]

...What would happen if they were put in series?

Most audio amplifiers I've seen are designed to accommodate the lower 4 Ohm (nominal) impedance of woofers wired in parallel than in series. Remember that power (in DC Watts) is calculated by multiplying Voltage x Amperes.

The above issue comes along when certain amps aren't designed to operate at 4 Ohms equivalent load impedance Most consumer audio amps that I've seen are not like the amp mentioned above. In the above case, this amp can apparently handle the higher voltages required to drive the higher impedance series-wired connection, but doesn't like below-8-Ohm impedance of woofers wired in parallel.

Some of this behavior is due to the large moving mass of the woofers, which results in higher reactance presented to the amp output, and some to the inability to effectively drive lower impedance loads. Some of this behavior may also be related to the high output impedance of the amplifier (...like tube amps...).

Amps, in general, don't like to drive very reactive loads: they must be designed to remain stable when driving them.

Chris

[twistedcrankcammer]

Yes, thanks. In my case with only a PLX 1804 I will be wiring woofers in parallel so each amp channel powers both woofers in a single cabinet at ~ 4ohms per Channel. Should be fine. I already do that now with my MWM cabinets and a QSC PLX 1104.

Mark,

Kevin Harmon has both of his KPT-684s wired in Paralel as well with his Crown XTIs bridged.

Roger

[twistedcrankcammer]

Hi, I have a dude about the SW KPT-684: the tech sheet talk about 8ohm impedance, but I think the 8ohm impedance is referring to each speaker, and the SW is 4ohm impedance. Please let me know what is the real impedance. Thanks a lot, Giorgio.

Giorgio

The KPT-684 is 8 Ohms per woofer at 400 watts per woofer. The Woofers are not wired in parralel, they both have individual positive and negative terminals at the terminal strip, on top of the unit. You could wire both woofers in paralel at the terminal strip for a 4 Ohm load, if that is what you wanted to do. I just use a sub woofer splitter cable and run a 2 channel amp into my KPT-684.

Roger

The 684 can be driven in 16ohm configuration also. We do it with a bridged amp and get excellent results.

It is not recommended to drive each woofer with separate amp channel as you will have phase errors from the amp. The 2 channels will not match exactly so the woofers will not move exactly together and since they are in the same enclosure the overall performance will be reduced. In some cases this is considerable. It is better to drive the speakers in 16ohm with the amp bridged. If the amp cannot be bridged then use only one channel as you will likely get better performance. There is no amp made regardless of price that will have exactly matching channels and the miss match is greater with the less expensive amps.

I had previously tried my KPT-684 wired in Paralel, and it plays louder wired with each channel of my amp wired to a seperate speaker.

After reading your reply, I tried wiring it series, and it still played louder with both channels playing, granted that I am running a Nakamichi PA-7II amp that is only 225 watts RMS per channel. This amp cannot be bridged, and it is a STASIS amp, meaning it puts out 225 watts into an 8 ohm load, a 4 ohm load, or a 2 ohm load. I do intend to get a propper Pro Amp. and run paralel wired, and run a second 684 in paralel as well on the second channel.

I do not buy into your theory on phase variations between my stereo amplifiers two channels, it is either in phase, or 180 degrees out. How else would one phase multiple powered subs, or multiple 684s with multiple amps, not to mention line arays. I call [bs] on that idea.

Roger

[djk]

This amp cannot be bridged, and it is a STASIS amp, meaning it
puts out 225 watts into an 8 ohm load, a 4 ohm load, or a 2 ohm load.

The PA7-II is rated at 325 into 4 ohms.

It could be bridged at 650W into an 8Ω load, but would require an external bridging device.

[RRFL]

Interesting stuff to a dummy like me.

Question (and this is just for theory & kicks, to see what the answer is, I'm not thinking about it)

The Jubilee bass bin has 2 drivers, each one comes to the terminal block.

I think they're wired in parallel (+/+ and -/-)

What would happen if they were put in series?

(remember to take any technical comment and dumb them down to a 5th grader level)

The Jubilee drivers are each 16ohm so wired in series you get 32ohm nominal.

I know of a jubilee "damage during delivery"[] that is currently wired in series as we wanted to see what it sounded like on a QSC RMX2450 bridged in mono. I have not run it at more than about 0.5 watt yet as the room was busy with hotel quests eating and talking both times I was there. My associate who wired it at 32ohm has give it some stick and reckons re-wire in parallel as he expected it to be louder. He did not realise that I deliberately pined the max gain quite low on the system controller so no one could get to full power and blow it up before I was able to set the limiters with the room empty. The theory is that the RMX 2450 does 1300watt bridged into 8ohm 0.1% distortion the 2 jub drivers together handle 400watt so in that room since full jub power might not be required, would 32ohm sound better due to the amp producing less distortion that 0.1%?

Answer is I don't know yet. Also the permanent six SLS speakers are not yet available and two substitute larger power hunger SLS are being driven by only 1 of the RMX2450 amps where as the six intended SLS will be driven by 3 RMX2450 amps. So I was not concerned about the 32ohm load and other more important things have priority.

[RRFL]

Hi, I have a dude about the SW KPT-684: the tech sheet talk about 8ohm impedance, but I think the 8ohm impedance is referring to each speaker, and the SW is 4ohm impedance. Please let me know what is the real impedance. Thanks a lot, Giorgio.

Giorgio

The KPT-684 is 8 Ohms per woofer at 400 watts per woofer. The Woofers are not wired in parralel, they both have individual positive and negative terminals at the terminal strip, on top of the unit. You could wire both woofers in paralel at the terminal strip for a 4 Ohm load, if that is what you wanted to do. I just use a sub woofer splitter cable and run a 2 channel amp into my KPT-684.

Roger

The 684 can be driven in 16ohm configuration also. We do it with a bridged amp and get excellent results.

It is not recommended to drive each woofer with separate amp channel as you will have phase errors from the amp. The 2 channels will not match exactly so the woofers will not move exactly together and since they are in the same enclosure the overall performance will be reduced. In some cases this is considerable. It is better to drive the speakers in 16ohm with the amp bridged. If the amp cannot be bridged then use only one channel as you will likely get better performance. There is no amp made regardless of price that will have exactly matching channels and the miss match is greater with the less expensive amps.

I had previously tried my KPT-684 wired in Paralel, and it plays louder wired with each channel of my amp wired to a seperate speaker.

After reading your reply, I tried wiring it series, and it still played louder with both channels playing, granted that I am running a Nakamichi PA-7II amp that is only 225 watts RMS per channel. This amp cannot be bridged, and it is a STASIS amp, meaning it puts out 225 watts into an 8 ohm load, a 4 ohm load, or a 2 ohm load. I do intend to get a propper Pro Amp. and run paralel wired, and run a second 684 in paralel as well on the second channel.

I do not buy into your theory on phase variations between my stereo amplifiers two channels, it is either in phase, or 180 degrees out. How else would one phase multiple powered subs, or multiple 684s with multiple amps, not to mention line arays. I call on that idea.

Roger

It's not a case of being 180 degrees out of phase. It's a case that no two amplifier channel are identical in performance regardless of the manufacture. The error is small and depends on the accuracy of the individual components in the amplifier such as caps, resistors, transistors, etc. Consider the measurements people make when recapping their crossovers and the variation in capacitors when measured and then when the temperature changes etc. It's this slight variation that will have one woofer be just a touch behind the other like a horse race photo finish. When they are both inside the same cabinet in a common chamber is when this becomes an issue. It is something that people who set up large PA systems for bands are aware of due to the poor performance of dual woofer cabinets wired with separate amp channels and directly compared side by side with other cabinets where only one channel was use to drive the whole cabinet.

I read a review on the PASS LABS XA30.5 stereo power amp. It's rated 30watts/channel class A 0.1% distortion. The review found it delivered 153watts from 1 channel and the other 156watts @ 0.1% distortion. It's price is $8995.00 AU. It's generally considered a very good amp. The reviewer tested many aspects of the amp and graphed the differences between the channels to it's rated distortion of 0.1%. The guy was deliberately nailing it to see if it would stop. He was surprised he was given the smallest amp in the entire range to evaluate and review. So the point is when something that is constructed to a very high standard as this amp is has differences between channels then the less expensive amps would have greater differences and people notice this as unexpected "red faced" poor performance of dual speaker woofers when continuous full power is required for live band performances. It has not happened to me, I have never experienced it.

If I was confident that the two channels of my PASS LABS x350.5 were identical, then I would use one amp to drive one of my Jubs woofers wired one channel per woofer and the other X350.5 to drive the other 2 woofers in the other jub. Then I would get the XA30.5 to drive the tweeters KPT-402/K69. The 2 X350.5 channels cannot be bridges as it is a Symmetrical Bridged design.

Your STASIS amp is as I understand a Nelson Pass design and made him famous the channels would be of the most accurate available but would still have variations between the channels.

[mikebse2a3]

The Jubilee drivers are each 16ohm so wired in series you get 32ohm nominal.

Hey rodrocket the drivers are more like 8 ohm.

Here is a Raw Impedance plot of the Jubilee by Roy when the Jubilee is wired with the drivers in parallel.

mike tn

Here are more plots of the Jubilee by Roy

http://community.klipsch.com/forums/t/78174.aspx?PageIndex=17

http://community.klipsch.com/forums/t/78174.aspx?PageIndex=18

[RRFL]

The Jubilee drivers are each 16ohm so wired in series you get 32ohm nominal.

Hey rodrocket the drivers are more like 8 ohm.

Here is a Raw Impedance plot of the Jubilee by Roy when the Jubilee is wired with the drivers in parallel.

mike tn

Here are more plots of the Jubilee by Roy

http://community.klipsch.com/forums/t/78174.aspx?PageIndex=17

http://community.klipsch.com/forums/t/78174.aspx?PageIndex=18

Thanks for attaching those links they are very interesting.

.........I should clarify that I refer to the nominated value only so it's a very simplistic comment not a scientific detailed comment that requires graphs......

When wired in parallel they are 8ohm. Individually they are 16ohm. If wire in series they are 32ohm.

My pair, when the replacement arrives will be wired normal parallel 8ohm, my associate just wanted to do 32ohm because he could to see what it sounded like.

I reserve my opinion until I get to turn it up and it will all depend on the QSC RMX2450.

My original suggestion was to use only one channel to drive the jub and leave the other channel as a spare as I think the amp will be cleaner not bridged. My associate can't bring himself to waste a channel doing nothing. The jub is in the install only because it was damaged and the Cinema Dealer gets some recovery. The instal was going to have a pair of 18" 400watt drivers in two reflex enclosures with one speaker attached to each side of the amp.