rc-64 Center channel bi-wire

[Islander]

When not using an active xo for bi-amping, the HF and LF driver both get 200 watts in the example. the tweeter uses very little power or around 5-10% of what the LF driver uses. All of the additional power to the HF drives is wasted as heat in the passive xo. That is why people run SS for the LF and tubes for the HF drivers when using active bi-amping. Also, using an active xo is not necessarily better that using the passive xo that was designed for the speakers.

The power relationship between the tweeter and woofer depends on the crossover point. When it's fairly high, the woofer does most of the work. When it gets down to about 600 Hz, the load is shared equally between the woofer and tweeter. I've seen a chart showing the power distribution with various crossover points, but the link seems to be lost.

In the case of the Jubilee and JubScala, the crossover point is around 480 Hz, so the tweeter actually uses more power than the woofer. This can be detected by the treble amp running warmer than the matching bass amp. In many bi-amped systems, it's best to use matching power amps for bass and treble. This makes level matching much easier, and the sound is consistent from top to bottom, rather than changing "flavour" or timbre when it crosses from woofer to tweeter.

One advantage of having a low crossover point is that more vocals come through the tweeter than the woofer, which lets them sound better.

As for active crossovers, they allow a level of accuracy in frequency response tuning or voicing that's not possible with passive crossovers. In some cases, their delay units permit time-alignment of the bass and treble, making the sound that bit more realistic. Also, sending the audio signal through capacitors and transformers can muddy the sound a bit and absorb some of the power. Those factors don't come into play with active crossovers.

[derrickdj1]

Islander you are correct with where the tweeter is xo in the passive or active xo, not the xo in the avr for clarification. My comments were geared to the Reference line which uses higher passive xo's. With speakers xo in the avr around 80 Hz in the Reference line the power distribution will be equal around 300 Hz. By 2-3 kHz, the woofer will consume 90 + % of the power. The RF 7 II uses a much lower xo than the original RF 7's. But, even with the lower xo, the majority of the power will be used by the woofers.

An active xo can allow for some fine tunning of the sound compared to the passive xo. The trade-off are the cost of the extra amp, and also learning curve dependent. With electronic DSP units this has became much more easier to do. I have not read up much on the Heritage line of speakers thanks for sharing about the Jubilee's.

Edited February 17, 2014 by derrickdj1

[etc6849]

This is interesting. I knew horn loaded woofers were efficient, but whaaa?!?

I agree that matching amps sounds like the best way to go. Definitely less to mess up that way. However, I am now confused. Are you saying the impedance of a K402 horn is lower to that of a bass bin under load? It would have to be to absorb more power, and this seems backwards from what I would have thought?!? Assuming the impedance is not lower, that means the voltage going to the K402 must be higher. This also seems backwards. Clearly I'm missing something...?

In the case of the Jubilee and JubScala, the crossover point is around 480 Hz, so the tweeter actually uses more power than the woofer. This can be detected by the treble amp running warmer than the matching bass amp. In many bi-amped systems, it's best to use matching power amps for bass and treble. This makes level matching much easier, and the sound is consistent from top to bottom, rather than changing "flavour" or timbre when it crosses from woofer to tweeter.

Edited February 17, 2014 by etc6849

[Islander]

I'm not sure what you mean by the impedance of the horn. Think of the woofer/tweeter power requirements in terms of the frequency range they have to cover in terms of octaves.

The audio frequency range (20 Hz-20 KHz) covers about 10 octaves. Each octave contains a similar amount of energy, but the treble octaves have a much wider frequency range than the bass octaves. The 20-40 Hz bottom octave contains about the same energy as the 10 KHz-20 KHz top octave.

If the crossover point is around 600 Hz, that means that the woofer will cover the bottom 5 octaves and the tweeter will cover the top 5 octaves, so their power requirements will be equal.

Many speaker systems are crossed over at 1800 Hz or even higher, so many people believe that the woofer always carries the vast majority of the load, with the tweeter doing 10% or less. This may be true with most speaker systems, but not all. Some pro audio and related speakers have a very low crossover frequency, so things are turned upside down from the usual in their cases.

This would just be a rare and curious instance, if not for the number of forum members using Pro Theatre, Jubilee or JubScala speaker systems. If you ever get a chance to hear such a system, you'll soon realize why they have so many fans.

[derrickdj1]

Islander this would be an interesting topic on power use and amp selection on some of the Heritage line. Some of what you said does seem backward when you first hear it. But, that lower xo point makes a big difference. I still have not ever heard a set of the Heritage line of speakers.

Selecting the power handling of the tweeter/HF driver is more important when doing mods to Khorns, jubs, jubscala. I kown for some two way non-horn loaded speaker the tweeter can have a much lower power handling rating than the woofer. Once again thanks for the comments, I like learning some knew things!

[Islander]

Generally speaking, tweeters do have lower power ratings than woofers. While the Klipschorn and La Scala woofer (the K-33) has a 100 watt rating, the K-77 tweeter rating is much lower, less than 10 watts, IIRC. This is because the K-77 covers only the range from 6 KHz-17 KHz, or 4.5 KHz-17 KHz in the later models. That's only 1.5-2 octaves, so it doesn't see a lot of power.

La Scala Industrials use the K-43 woofer, rated at 200 watts, and have protective fuses.

With the Jubilee and JubScala, the K-69 tweeter is rated at 50 watts.

As you likely know, most musical instruments don't produce any fundamentals past about 4 KHz. The rest is harmonics, as you can see by this chart, and even the harmonics only go so high. As a result, the upper octaves don't contain as much energy in practical terms as they do in theory, since only whistles would be mostly playing at the very high frequencies.

Frequency chart: http://www.themusicespionage.co.uk/wp-content/uploads/2012/08/Frequency-Chart.jpg

Since the big Heritage (and Jubilee and JubScala) speakers are so sensitive, at 104 dB/W/M or more, the drivers are running on fractions of a watt most of the time, only pulling lots of watts during brief musical peaks. In my system, one 500Wpc dual-mono amp feeds the woofers and the second matching amp feeds the tweeters.

This means that each 50-watt tweeter has 500 watts available to it, and each 100-watt woofer also has 500 watts available to it. "Available" is the keyword. It's not like flicking a light switch and sending full power through the speaker cables. To reproduce music realistically, it takes a lot of power to accelerate a woofer cone or tweeter diaphragm to match the speed of a drumskin or piano string being hit, but the drivers can absorb large amounts of power for brief instances without any problems. However, if you were to push a constant sound, like a test tone, to a driver at high volume, you could fry it pretty quickly.

With the digital volume knob on the Yamaha receiver taking over 3 turns from minimum to maximum volume, you can't go to max volume with just a flick of the wrist, so the rising volume has time to warn you before you get into any danger zone.

I've never actually turned the volume all the way up, because painful levels are reached at least 10-15 dB before max volume with CDs or DVDs. Max volume with LPs is much lower, due to the comparatively low output of phono cartridges.

Your RF7s are highly respected and well-liked speakers, but the La Scala bass horn, with its 4 square foot opening, can move more air with less distortion than any direct-firing woofer. You're in for a treat when you get to hear a La Scala. I've not heard a properly set-up Klipschorn, but they also can move a lot of air with very little distortion.

Edited February 18, 2014 by Islander

[javelin]

Finally finished the "remodeling" and have the rc-64 in its new home. Scooby just can't stop staring at it.

There is a very noticeable difference between the rc-3ii and rc-64 in terms of vocal output and efficiency. On rc-64, I set my volume level to -23 and I never have to touch it again. With the rc-3ii, to hear the same output, I had to set volume level to -18 and sometimes I still have to adjust volume during in-movie.

rc-64 installed:

watching enders game:

Is there anyway to reduce the amount of vocal output coming from the La Scala? Is this plausible and is it even a good idea?

Just trying to find out if anyone has done this already; new xover maybe?

[derrickdj1]

The new home for the RC 64 looks great. As far as vocals, a lot of it depend on how the movie was made. THX modes on the avr will foucus on the center channel and decrease what comes out of the front speakers. Very impressive HT!!!

[javelin]

Thanks derrickdj.

I may need to recalibrate my fronts, center, and avr again. Then test the thx modes and see which one

sounds best.

I sometimes see crites crossover mention in the forum but never really investigate it. Maybe something to

look at for future upgrades.

[Thaddeus Smith]

Thanks derrickdj.

I may need to recalibrate my fronts, center, and avr again. Then test the thx modes and see which one

sounds best.

If you haven't done that since swapping in the RC-64, then you most certainly must. That's not small change and it has an impact on the overall audio presentation and balance.

[etc6849]

50-watts is a lot for a tweeter, wow!?! Usually I think tweeter wattage is very very low compared to a woofer's. That's what leads me to believe in general higher frequencies take less electrical power to produce, and the low end will almost always take more electrical to produce. It is true a cross-over circuit must have padding resistors for the tweeter (as it seems more efficent to get the same SPL) and these resistors must waste electrical power.

However, this power distribution plot you speak of sounds interesting... Can you provide a link? I agree at some frequency on a speakers response, the sum of the power spectral density (PDS: http://en.wikipedia.org/wiki/Power_spectral_density#Power_spectral_density) will be 50/50. However, the PSD, may not equal the instantaneous electrical power an amp may see at any given moment, and for sure thinking of things in terms of total energy by integrating the power distribution will not correlate to real world electrical power consumption versus time. However, I'm not sure what you mean by power distribution as I'm not a speaker designer.

For any given high frequency from a tweeter, producing x dB versus a given low frequency from a woofer producing the same x dB, I would expect the electrical power to always be more going to the woofer. After all, a woofer is larger and heavier, so I don't think it'll ever be as efficient as a tweeter (even if it is horn loaded). It's also true that a woofer will have to move a larger distance as the wavelength of the sound wave gets longer, so this involves putting more work into the system (and this takes more electrical energy). Even though a tweeter is required to vibrate faster, it appears base

Wrt to your question of impedance, I was referring to electrical impedance (R + jX), which is made up of resistance ® and reactance (X). Power (P) is P = i^2*R, one would expect at first glance, the driver drawing the most power to have a higher R. However, X can change the phase angle for i, which will change the magnitude of the i's phasor (http://en.wikipedia.org/wiki/Phasor), and jX will also change as frequency changes. Also i is squared in the equation, so it must be more dominant than R. In retrospect, this wasn't the best way to think of things. To make matters worst, it looks like the electrical models used for representing a woofer can get very complicated too, so figuring out what i and R might be without actually measuring them under load seems cumbersome. I also realize I keep saying power and not electrical power, and this is confusing as power and impedance are generic terms and apply to acoustics as well.

Not being a speaker designer, I wouldn't mind reading a technical paper that explains when a tweeter uses the same amount of electrical power as a woofer.

This means that each 50-watt tweeter has 500 watts available to it, and each 100-watt woofer also has 500 watts available to it. "Available" is the keyword. It's not like flicking a light switch and sending full power through the speaker cables. To reproduce music realistically, it takes a lot of power to accelerate a woofer cone or tweeter diaphragm to match the speed of a drumskin or piano string being hit, but the drivers can absorb large amounts of power for brief instances without any problems. However, if you were to push a constant sound, like a test tone, to a driver at high volume, you could fry it pretty quickly.

Edited February 21, 2014 by etc6849

[javelin]

The new home for the RC 64 looks great. As far as vocals, a lot of it depend on how the movie was made. THX modes on the avr will foucus on the center channel and decrease what comes out of the front speakers. Very impressive HT!!!

You're absolutely right. After recalibrating the speakers, I set THX to auto(I always had it on THX Movie or Cinema) and loaded Act of Valor blu-ray. Wow, the seperation is just beautiful. I set my ear close to the La Scala and I could hear no trace of vocal output at -20dB. It's totally new experience for me with the RC-64 and new settings.

[etc6849]

It sounds like -20dB works, but if that wasn't enough trim, the only other option is to install pads between an amp and a preamp. Since you can't do this with an AVR as the amp is internal, the last approach would be to lower the input level for each source you use, and raise the center channel a similar amount.

Awesome looking setup by the way!

Is there anyway to reduce the amount of vocal output coming from the La Scala? Is this plausible and is it even a good idea?

Just trying to find out if anyone has done this already; new xover maybe?

[Islander]

50-watts is a lot for a tweeter, wow!?! Usually I think tweeter wattage is very very low compared to a woofer's. That's what leads me to believe in general higher frequencies take less electrical power to produce, and the low end will almost always take more electrical to produce. It is true a cross-over circuit must have padding resistors for the tweeter (as it seems more efficent to get the same SPL) and these resistors must waste electrical power.

However, this power distribution plot you speak of sounds interesting... Can you provide a link? I agree at some frequency on a speakers response, the sum of the power spectral density (PDS: http://en.wikipedia.org/wiki/Power_spectral_density#Power_spectral_density) will be 50/50. However, the PSD, may not equal the instantaneous electrical power an amp may see at any given moment, and for sure thinking of things in terms of total energy by integrating the power distribution will not correlate to real world electrical power consumption versus time. However, I'm not sure what you mean by power distribution as I'm not a speaker designer.

Not being a speaker designer, I wouldn't mind reading a technical paper that explains when a tweeter uses the same amount of electrical power as a woofer.

This means that each 50-watt tweeter has 500 watts available to it, and each 100-watt woofer also has 500 watts available to it. "Available" is the keyword. It's not like flicking a light switch and sending full power through the speaker cables. To reproduce music realistically, it takes a lot of power to accelerate a woofer cone or tweeter diaphragm to match the speed of a drumskin or piano string being hit, but the drivers can absorb large amounts of power for brief instances without any problems. However, if you were to push a constant sound, like a test tone, to a driver at high volume, you could fry it pretty quickly.

You can think of the power distribution in terms of how many octaves each driver has to cover. In a 3-way system, the tweeter is crossed over at a fairly high frequency, say 4500 or 6000 Hz, so it has little work to do and needs little power. In a 2-way system, the tweeter starts working at a much lower frequency, say 450 to 1800 Hz, so it has more work to do and uses more power. A wide-range tweeter like that would naturally need to have a higher power handling rating.

As I mentioned in a previous post, at about 600 Hz, the load is shared fairly equally between the woofer and the tweeter. It's been a long time since I've seen the handy chart that spells out the power distribution by crossover frequency, but I did find a couple of links that might be helpful. Feel free to do some searching yourself.

Crossover basics: http://lenardaudio.com/education/06_x-over.html

diyaudio discussion of crossover points: http://www.diyaudio.com/forums/multi-way/45831-crossover-points-music-power-distribution.html

[robbiey60]

this has left me wondering... has anyone ever used three RC64's for the center and two rear channels in a 5.1 system?

maybe I should be the first

not quite rc64ii (I do have 1 as center) but I am toying with the idea of running twin rc62iis as rear surrounds. I have 1 as single rear surround and it is pretty good

NOT, a bad idea... and more cost effective!

I want to know who is going to be the first to try it

so I went ahead and got a 2nd rc62ii. I have sold my synergy f30 that I had as surrounds so twin rc62iis for surrounds now. Very impressed, long term goal is aquire another set of reference towers for surrounds and have the 2 rc62s as rear surrounds.

[javelin]

this has left me wondering... has anyone ever used three RC64's for the center and two rear channels in a 5.1 system?

maybe I should be the first

not quite rc64ii (I do have 1 as center) but I am toying with the idea of running twin rc62iis as rear surrounds. I have 1 as single rear surround and it is pretty good

NOT, a bad idea... and more cost effective!

I want to know who is going to be the first to try it

so I went ahead and got a 2nd rc62ii. I have sold my synergy f30 that I had as surrounds so twin rc62iis for surrounds now. Very impressed, long term goal is aquire another set of reference towers for surrounds and have the 2 rc62s as rear surrounds.

Would love to see your setup. Post pic when you can

[robbiey60]

this has left me wondering... has anyone ever used three RC64's for the center and two rear channels in a 5.1 system?

maybe I should be the first

not quite rc64ii (I do have 1 as center) but I am toying with the idea of running twin rc62iis as rear surrounds. I have 1 as single rear surround and it is pretty good

NOT, a bad idea... and more cost effective!

I want to know who is going to be the first to try it

so I went ahead and got a 2nd rc62ii. I have sold my synergy f30 that I had as surrounds so twin rc62iis for surrounds now. Very impressed, long term goal is aquire another set of reference towers for surrounds and have the 2 rc62s as rear surrounds.

Would love to see your setup. Post pic when you can

my room is a shambles lol (as long as it sounds good right) will try and tidy it up fot a more photogenic pic. I have some older pics of my gear over on avs forums, same username

[robbiey60]

this has left me wondering... has anyone ever used three RC64's for the center and two rear channels in a 5.1 system?

maybe I should be the first

not quite rc64ii (I do have 1 as center) but I am toying with the idea of running twin rc62iis as rear surrounds. I have 1 as single rear surround and it is pretty good

NOT, a bad idea... and more cost effective!

I want to know who is going to be the first to try it

so I went ahead and got a 2nd rc62ii. I have sold my synergy f30 that I had as surrounds so twin rc62iis for surrounds now. Very impressed, long term goal is aquire another set of reference towers for surrounds and have the 2 rc62s as rear surrounds.

Would love to see your setup. Post pic when you can

my room is a shambles lol (as long as it sounds good right) will try and tidy it up fot a more photogenic pic. I have some older pics of my gear over on avs forums, same username

[robbiey60]

Tried uploading pics, wont let me says file too big. Im using galaxy s4, any ideas?

[Youthman]

Robbiey, if the files are too large for the forum, you will need to use an image editor to resize them prior to uploading to the forum. For the PC, try Irfanview. It's free and really easy to use.