Why do 800D need so much current?

[wettou]

I know that some of you have a degree in electrical engineering on this forum and was wondering if you could explain the difference between Current vs Watt

Also how does one find out how much current an amp has? I apologize if you already have answered this question in the Classé thread but thought that this might be broader audience:T

[AV-OCD]

I know that some of you have a degree in electrical engineering on this forum and was wondering if you could explain the difference between Current vs Watt

Also how does one find out how much current an amp has? I apologize if you already have answered this question in the Classé thread but thought that this might be broader audience:T

Hey Wettou -

I'm not an EE, but I'll take a stab at this. You won't find a "current" (amperage) rating listed on the spec sheet of many if any amp, so the easiest way to tell if it is a high current design is to look at the wattage output into different impedances. If an amp outputs 200WPC @ 8 Ohms, if it is a high current design it should output approximately double the wattage into 4 Ohms (400WPC), and double again into 2 Ohms (800WPC).

I wasn't able to find the impedance graph for the 800, but the graph in Stereophile for the 802D shows that the impedance is right around 3 Ohms from 1KHz on down through most of the bass. That can be a demanding load for an amp, BUT only if you are cranking up the volume. You could run the 802 or 800 off of a decent AVR, as long as you don't exceed the wattage that AVR is capable of at 3 Ohms.

[audioqueso]

Wouldn't just using P I E work?

[Space]

...the easiest way to tell if it is a high current design is to look at the wattage output into different impedances. If an amp outputs 200WPC @ 8 Ohms, if it is a high current design it should output approximately double the wattage into 4 Ohms (400WPC), and double again into 2 Ohms (800WPC).

That seems logical but different amp manufacturers specify their power into different distortion levels. Two amps with very different capacity could specify the same wattage, but the less powerful amp will have higher distortion at that output level.

Generally I see rated power about 1.5x higher into 4 ohms than 8 ohms, until you get into the very expensive gear. Brands like Classe could do the same, and quote a higher power level than they do at 8 ohms, but they choose not to. I would guess that some manufacturers just want to look impressive by quoting twice the wattage into 4 ohms than 8.

It would be helpful for making comparisons if rated power were always measured based on the same distortion level, like 0.1%. They could also specify a lower power with 0.005% if they want to go that route, or a higher power with 0.5%.

[mjb]

Why do 800D need so much current?

Because they sound so good, you'll want to listen to them LOUD.

[AV-OCD]

That seems logical but different amp manufacturers specify their power into different distortion levels. Two amps with very different capacity could specify the same wattage, but the less powerful amp will have higher distortion at that output level.

Generally I see rated power about 1.5x higher into 4 ohms than 8 ohms, until you get into the very expensive gear. Brands like Classe could do the same, and quote a higher power level than they do at 8 ohms, but they choose not to. I would guess that some manufacturers just want to look impressive by quoting twice the wattage into 4 ohms than 8.

It would be helpful for making comparisons if rated power were always measured based on the same distortion level, like 0.1%. They could also specify a lower power with 0.005% if they want to go that route, or a higher power with 0.5%.

You're right, even most capable amps are closer to 1.5ish times the power into each halving of impedance, and it is important to consider the distortion levels at a given output.

I pretty much disregard manufacturer specs and look for objective measurements from independent sources. Home Theater Magazine and Stereophile both publish objective measurements for low impedance performance that include the distortion levels for the measured output that you said you're looking for.

BTW - Classe does quote power into both 8 and 4 Ohm loads on their spec sheets, though they don't give distortion levels for those ratings. But with their track record for delivering on spec, they can be trusted.

[boarder1995]

This is interesting, since most ICE power class-D amps I've looked at are double the power into half the impedance. Also, my Sunfire "high current" amp is double the power into half the load as well (I think). Of course, I'm mostly looking at manufacturers specs, not actualy measurements. However, I see lots of Mac amp specs on some of their older gear with impedance switches that don't double down, they stay the same power into 1/2 the impedance. This is the switch that's limiting the power though. I'm not sure what Mac does into the true variable loads speakers really present amplifiers. But, Mac gear is typically regarded as an ideal amp match to B&W and I tend to agree as I've heard and loved the sound versus even Classe gear on the same speakers at the dealer. This is of course personal ear preference and not scientific measurements, but still poses an interesting question to current vs. load on some of these "current hungry" speakers.

Basically, B&W big speakers can handle lots of clean power and they sound good turned up, and don't tend to get harsh, unless the amp does. With the new Di line, the drivers are supposed to stay even cleaner at higher excursions with the new quad magnet assembly, so possibly more clean power will be warranted.

[wettou]

Hey Wettou -

I'm not an EE, but I'll take a stab at this. You won't find a "current" (amperage) rating listed on the spec sheet of many if any amp, so the easiest way to tell if it is a high current design is to look at the wattage output into different impedances. If an amp outputs 200WPC @ 8 Ohms, if it is a high current design it should output approximately double the wattage into 4 Ohms (400WPC), and double again into 2 Ohms (800WPC).

I wasn't able to find the impedance graph for the 800, but the graph in Stereophile for the 802D shows that the impedance is right around 3 Ohms from 1KHz on down through most of the bass. That can be a demanding load for an amp, BUT only if you are cranking up the volume. You could run the 802 or 800 off of a decent AVR, as long as you don't exceed the wattage that AVR is capable of at 3 Ohms.

Thank you, so if I want to play them loud, I should probably get mono-blocks or very decent stereo since all multichannel don't double at

Classé CA-5200
200WPC @ 8 Ohms
370 WPC @4 Ohms

nothing at 2Ω?

Where as the CT-M600 rates

600W rms into 8Ω (27.8 dBW)
1200W rms into 4Ω (27.8 dBW)

what does rms means?

[wettou]

This is interesting, since most ICE power class-D amps I've looked at are double the power into half the impedance. Also, my Sunfire "high current" amp is double the power into half the load as well (I think). Of course, I'm mostly looking at manufacturers specs, not actualy measurements. However, I see lots of Mac amp specs on some of their older gear with impedance switches that don't double down, they stay the same power into 1/2 the impedance. This is the switch that's limiting the power though. I'm not sure what Mac does into the true variable loads speakers really present amplifiers. But, Mac gear is typically regarded as an ideal amp match to B&W and I tend to agree as I've heard and loved the sound versus even Classe gear on the same speakers at the dealer. This is of course personal ear preference and not scientific measurements, but still poses an interesting question to current vs. load on some of these "current hungry" speakers.

Basically, B&W big speakers can handle lots of clean power and they sound good turned up, and don't tend to get harsh, unless the amp does. With the new Di line, the drivers are supposed to stay even cleaner at higher excursions with the new quad magnet assembly, so possibly more clean power will be warranted.

To me ICE power sounds bad

[dknightd]

As mentioned, as the impedance of a speaker drops it needs more current to deliver the same power. If a speaker was a simple resistive load this would not be much of a problem (Voltage stays in phase with current, and life for an amp is pretty easy). But what can be even more of a problem is a reactive load (which most speakers are), now current and voltage are not in phase - an amplifier can be asked to deliver high current when the output voltage is low - this can be more difficult.
You could have two amps that are rated at the same power when feeding a purely resistive load. But one of the amps could run out of juice (current) when trying to feed a reactive load at the same power.

edit: wettou, rms = root mean square - basically the average power delivered. Usually measured using a resistive load (as required by government regulations, but not particularly useful)

[Orb]

As mentioned, as the impedance of a speaker drops it needs more current to deliver the same power. If a speaker was a simple resistive load this would not be much of a problem (Voltage stays in phase with current, and life for an amp is pretty easy). But what can be even more of a problem is a reactive load (which most speakers are), now current and voltage are not in phase - an amplifier can be asked to deliver high current when the output voltage is low - this can be more difficult.
You could have two amps that are rated at the same power when feeding a purely resistive load. But one of the amps could run out of juice (current) when trying to feed a reactive load at the same power.

edit: wettou, rms = root mean square - basically the average power delivered. Usually measured using a resistive load (as required by government regulations, but not particularly useful)

Just to add.
And is one of the factors why some well designed 60w (and low) amps can handle difficult speakers better than a 200w quoted one.
There are a few amps that do double their watts into each of the ohms at 1% THD up to 2ohms, but they arent cheap as already mentioned.

But this is only one of a few factors considered for handling speakers.
Cheers
Orb

[wettou]

Just to add. And is one of the factors why some well designed 60w (and low) amps can handle difficult speakers better than a 200w quoted one. There are a few amps that do double their watts into each of the ohms at 1% THD up to 2ohms, but they arent cheap as already mentioned.

But this is only one of a few factors considered for handling speakers.
Cheers
Orb

In brief if I upgrade my CA-5200 to CT-600M will I hear a difference?

[Relentless]

In brief if I upgrade my CA-5200 to CT-600M will I hear a difference?

I have gone up from 400 to 600 in the evo line and I can say that they are voiced the same so at low levels I don't think I would hear a difference worth the price of admission but the difference at high levels is why I went for it. The 400 would get out of balance sooner than the 600 as you get into the higher DB's.

[Orb]

In brief if I upgrade my CA-5200 to CT-600M will I hear a difference?

Now that is a really tricky question.
Mainly because in my experience A/B products briefly makes it tough to identify differences and requires specific music where traits-characteristics-niggles can be heard.
The other thing is that there is a good chance both resolve or fail the same traits/niggles.

One trick worth remembering is listen at all types of levels, I find some amps are better at low levels on difficult speakers than others.
However if you always play loud then again this is not going to bother you.

I guess where I am coming from is, its not necessarily hearing the differences but listening behaviour; does one amp keeps the urge of wanting to put on another album or does it start to feel a bit of a chore after saying 1.5hours.
For differences your best bet is to find some of your albums that has say a segment that you find niggling/artificial/etc and try that combined with lengthy listening sessions to see if it becomes a chore, rather than focus on the subjective what sounds better.

Bear in mind the good audio journalist has the amp for several months with other reference products as a comparison at same time, with extensive listening sessions.
Most of us cannot do that in our lives.

Sorry if this does not answer in the way you hoped for.
Cheers
Orb

[windshear]

Regarding the use of RMS. It can only be used in term of AC voltage. Its a means to give an average approximation, more or less to constant/DC equivalent. It CANNOT be used in a power equation. There is no such thing as RMS power.

Regarding how much power and current an amp can provide always raises the same questions. Most manufacturers use a different means of certifying. Its a pity there is no universal standard. Some specify rated power @1khz and some across a 20-20khz spectrum. Some specify it on a time limited basis, ie in milliseconds. In terms of audio, more is always better. Given that a loudspeaker is a reactive load that has impedance that varies according to the frequency, its not a fixed thing like a resistor. Also a lot of the times amps far exceed their power specs, however the specs are given to show in what range the amps total harmonic distortion (THD) is below an accepted norm.

More is always better especially when it comes to speakers that have extremely low impedance, that current becomes the issue as the amplifier then sees an apparent "short" and shuts down. It boils down to a cost versus capability compromise.

Getting back to the original question regarding how many amps can be supplied by an amp. If you dont have access to equipment to measure then you are stuck by what the manufacturer says, if they even mention it. Even if you do measure it, its difficult at the best of times as it becomes a practical/theoretical translation issue due to the reactive load the amp is exposed to. Hence using a fixed resistive load, to give a fixed current reading, but not accurate. If you could measure inline im not sure it would be accurate due to the nature of lag in the measuring devices or even issues of possible back EMF. There are many more aspects to consider which go way beyond my level of comprehension and in sure the "experts" who do this for a living would be better qualified to expand on them.

[Relentless]

Just something to add......in a lot of cases the wall voltage sags before high current amps can truly produce there published or possible 2ohm measurements. A true dedicated line is a great investment if you like to push the 800D's.

[Orb]

Just something to add......in a lot of cases the wall voltage sags before high current amps can truly produce there published or possible 2ohm measurements. A true dedicated line is a great investment if you like to push the 800D's.

Yep and thats a good point, some amps are more affected by this than others, why its interesting to read JA and Paul Millers comments at times on their measurements.
Other thing to watch out for is the amp's output impedence across FR and also impedence change (8/4/2ohm), only a rare few are truly stable without a noticable change in measurement.

Cheers
Orb

[mjb]

Power supplies are full of capacitors, so there goes the current lag theory.

Funny how the switching amps are immune to most of the problems talked about here, but nobody seems to like how they sound.

[Orb]

Power supplies are full of capacitors, so there goes the current lag theory.

Funny how the switching amps are immune to most of the problems talked about here, but nobody seems to like how they sound.

Although they do suffer distortion and output impedence fluctuation across FR and 8/4/2ohm impedence.
Not saying this is necessarily audible but points to a behaviour difference in terms of engineering.
Also Class D amps require filtering to remove the additional noise, maybe this is one of the reasons older designs of Class D are reported as sterile, along with the potential variance when considering FR-impedence and different speakers, etc.

And regarding power sag is measured at both Stereophile and Hi-finews, not sure if thats what your point was on lag.
But the capacitance capability and output stages are not standard in how implemented, some seem much better than others in products.
Sorry if I am missing the point you made.

Cheers
Orb

[wettou]

Just something to add......in a lot of cases the wall voltage sags before high current amps can truly produce there published or possible 2ohm measurements. A true dedicated line is a great investment if you like to push the 800D's.

I have a dedicated 20A line which is great as it reduce floor noise

[DM3000 Owner]

That seems logical but different amp manufacturers specify their power into different distortion levels. Two amps with very different capacity could specify the same wattage, but the less powerful amp will have higher distortion at that output level.

Generally I see rated power about 1.5x higher into 4 ohms than 8 ohms, until you get into the very expensive gear. Brands like Classe could do the same, and quote a higher power level than they do at 8 ohms, but they choose not to. I would guess that some manufacturers just want to look impressive by quoting twice the wattage into 4 ohms than 8.

I'm glad that you mentioned this. Industry trick that is used to show a higher "quality" by adhering to an impossible standard to meet doubling down each time impedance is cut in half).

THere is also a post about the 800D's impedence of 3 ohms. That is not a terribly difficult load, but if you are talking about a bis phase angle between voltage and curent (a reactive load instead of an active load) things get difficult in a hurry. It has been many years since my undergrad EE courses so I hope that I am expresing this correctly. :E

[Relentless]

I have a dedicated 20A line which is great as it lowers the noise floor.

That is a must for any high end system. Also the funny thing is we are talking about the 800D's but I believe the 802D's is a harder load for an amp because it spends more time in the 2ohm range than the 800D. That is something I remember reading a while back.

[wettou]

That is a must for any high end system. Also the funny thing is we are talking about the 800D's but I believe the 802D's is a harder load for an amp because it spends more time in the 2ohm range than the 800D. That is something I remember reading a while back.

I have 802Ds so where did you see that the 802D spend more time in 2Ω!

[AV-OCD]

I have 802Ds so where did you see that the 802D spend more time in 2Ω!

According to Stereophile's test, it doesn't.



The solid line is the impedance plot. You can see that there is a minimum impedance of 3 Ohms @ 600Hz and 100Hz, though it does stay below 4 Ohms more of the time than most speakers I've seen measured by Stereophile.

[wettou]

According to Stereophile's test, it doesn't.



The solid line is the impedance plot. You can see that there is a minimum impedance of 3 Ohms @ 600Hz and 100Hz, though it does stay below 4 Ohms more of the time than most speakers I've seen measured by Stereophile.

What does this mean excuse my ignorance??

[AV-OCD]

What does this mean excuse my ignorance??

See values along the left side of the graph that go 0.00, 2.00, 4.00, 8.00, etc.?

That is the impedance (Ohm) value.

Along the bottom of the graph is the frequency from 10Hz to 50KHz.

The solid black wavy line is the actual measured impedance of the speaker for a given frequency.

So, for example if you look at the black line just above the 100 mark, it is between 2.00 and 4.00, meaning the actual value is around 3.00 Ohms.

[Orb]

And just to add, put simply the phase angle (dotted line) is important as this affects the power required, bigger the phase angle greater power requirement over normal (say normal is ratio 1:1).

So at a few points the phase angle hits 45degree when impedence is under 4ohms, this can make it a tough speaker to drive.
IMO anyway.

Cheers
Orb

[Glen B]

Seconded on the significantly severe phase angle through the mid bass/low midrange region.

[PavelL]

http://www.stereophile.com/reference/707heavy/index.html

[wettou]

Thank you all,

Whoa I had no idea so an amp of lesser quality is really going to suffer with 802Ds!!!

It seems that a large monoblock with 400W@8Ω that doubles at 4Ω (800) and doubles again at 2Ω (1600W) will be ideal rather than a 200W per channel! Does the Classé CA-M400 able to do this or does any amp able to do that with out breaking the bank!


What if one cross over the 802D at 80HZ and let the subs do all the heavy lifting?



Interesting Emotiva states:
• Topology: Fully Discrete, Dual Differential, High Current, Short Signal Path Class A/B

• Power output
(all channels driven):
1,000 watts RMS @ 4 ohm (0.1% THD)
500 watts RMS @ 8 ohm (0.1% THD)

• Power Band Response: 20 Hz to 20 kHz with less than .05db deviation at rated power


• Broadband Frequency Response: (-3db): 5Hz to 150kHz

• Amplifier Gain: 32db

• Signal to Noise Ratio
1 watt: >89db
Full Power: >117db

• Input Impedance:
Unbalanced – 20kohms
Balanced – 18kohm

• Transformer Size: 1,200VA

• Secondary capacitance: 120,000uF

• Output Devices: 24


http://emotiva.com/xpa1.shtm Look at the pdf files with tests

[Orb]

Heya wettou,
heh I am sure you heard it many times but never use a manufacturers figures.
What your interested in is the measurements showing distortion across FR and impedence 8/4/2 presented by speaker, the amp's output impedence and how that also changes, and of course you have the power supply to voltage rails showing watt figures.

You do not necessarily need an amp that truly doubles the watts at say 1%thd, they are rare, think only of a handful of amps that can do this such as the Krells.
Check Stereophile to see difference between say the Cam 3200 against their Omega.
The Omega have slightly better measurements, but remember this does nothing to help identify whether you will enjoy the music with your speakers.

I see you got your eyes on Emotiva, you also thought about the Harman Kardon HK990?
Also seems a good budget amp that won EISA award and has good watt capability (way beyond its stated figures, measurements were in Hi-FiNews).

Cheers
Orb

[ryan.devry]

wettou, I was meaning to answer your original question a while ago, however, I have been at work a good bit and didn't have time.

"Why do 800D need so much current? "

I am in Electrical Engineer and I work in the Electrical Utilities. I control the flow of electricity in American Electric Powers eastern transmission system. So I work it electromagnets/Electromagnetic induction on a daily basis. I also have experimented in my college days with speaker construction. To get to the question at hand, it has to do with how Electromagnets actually work (most speaker are electromagnets).......

An Electromagent is essentaily a metal core with a wire tightly rapped around it. When there is no current applied to the wire, there is no magnetic field. However, once you induce a current on to the wire, you create a magnetic field.

In speaker construction this electromagnet is housed (held) by the diaphram. This basically sets inside the solid or permanent magnet. so when the system is idle (no current) your woofers don't move.

The amps job is to apply the current and constantly switch the singal. The amp does this by reversing the direction of the signal, this reversing the polartiy of the electromagnet from- to + and + to -. This is why you see the woofers move in and out.

Now the stronger the current applied to the voice coil, the stronger the magnetic field will be.....The stronger the magnetic field is, the stronger the amplitude of the wave form will be..... IE the potentail for the human ear to hear more (more volume, more detail, etc).

I hope I didn't rample to much but that's the basics. The 400W mono would have more current and yes you could possibly hear a difference!!!!!

If I am wrong I guess I wasted my money in college, and AEP should fire me...lol

[ryan.devry]

I am not for sure what the specs are on the 800D current carrying capabilities are, but I think B&W engineers designed them to be bullet proof.........No pun intended on the kevlar midrage...lol

[boarder1995]

I believe the new 800Di line can handle the higher power with even less distortion now with it's quad neo magnets which help with overhung driver excursions. The driver movement will remaing more linear throughout it's entire travel, particularly at extremes than the previous 800 line. Still both models will need clean power to fully realize the potential at high listening levels. I'm only running 200wpc of Sunfire power through my 803D, so I still haven't "arrived" at the potential of my towers yet, but hope to someday when I pick out an amp.

[wettou]

wettou, I was meaning to answer your original question a while ago, however, I have been at work a good bit and didn't have time. "Why do 800D need so much current? "

I am in Electrical Engineer and I work in the Electrical Utilities. I control the flow of electricity in American Electric Powers eastern transmission system. So I work it electromagnets/Electromagnetic induction on a daily basis. I also have experimented in my college days with speaker construction. To get to the question at hand, it has to do with how Electromagnets actually work (most speaker are electromagnets)....... An Electromagent is essentaily a metal core with a wire tightly rapped around it. When there is no current applied to the wire, there is no magnetic field. However, once you induce a current on to the wire, you create a magnetic field.

In speaker construction this electromagnet is housed (held) by the diaphragm. This basically sets inside the solid or permanent magnet. so when the system is idle (no current) your woofers don't move.

The amps job is to apply the current and constantly switch the signal. The amp does this by reversing the direction of the signal, this reversing the polarity of the electromagnet from- to + and + to -. This is why you see the woofers move in and out. Now the stronger the current applied to the voice coil, the stronger the magnetic field will be.....The stronger the magnetic field is, the stronger the amplitude of the wave form will be..... IE the potential for the human ear to hear more (more volume, more detail, etc). I hope I didn't rumple to much but that's the basics. The 400W mono would have more current and yes you could possibly hear a difference!!!!!

If I am wrong I guess I wasted my money in college, and AEP should fire me...lol

Ryan, thank you very much :T it is nice to read about some one who is actually qualified and has the educational background.

Here is an other question related to this one. So If I buy a second ampli like the CA-3200 would I be better off bi-amping the 802D using one channel for highs CA-3200 and one for the lows with the CA-5200 or should I bridge the channels and get more power to each speaker?

Also I read some where that when one bridges the channels you more than double the Watts?

Finally what is your take about cables, do you believe in high priced speaker cables

[Glen B]

I am sorry to be Devil's advocate but the above is a high school physics lesson in the fundamentals of electromagnetism and how a dynamic speaker works. IMHO, the reason why a high current amplifier is recommended for B&W 800D and other similar speakers, is because of their significant dip in impedance AND the effects of a quite severe phase angle. This is what Orb suggested above, and I though would have been clear enough. Please see the link below to a Rod Elliot article that explains phase angle, and its effects on an amplifier better than I could in this thread.

When you bridge the two channels of an amplifier, you more than double the watts output, but the amplifier also has to deliver twice the current because the load has been halved. Not all amplifiers take kindly to this increased current demand and some will overheat and shutdown or self-destruct. Some amplifiers are spec'd for bridged operation into 8 ohms only. Classé amplifiers are spec'd for bridged operation into 4 ohms, so you're good. I will leave comments on whether or not to bi-amp Classé and B&W to those who have tried it.

http://sound.westhost.com/patd.htm

[wettou]

I am sorry to be Devil's advocate but the above is a high school physics lesson in the fundamentals of electromagnetism and how a dynamic speaker works. IMHO, the reason why a high current amplifier is recommended for B&W 800D and other similar speakers, is because of their significant dip in impedance AND the effects of a quite severe phase angle. This is what Orb suggested above, and I though would have been clear enough. Please see the link below to a Rod Elliot article that explains phase angle, and its effects on an amplifier better than I could in this thread.

When you bridge the two channels of an amplifier, you more than double the watts output, but the amplifier also has to deliver twice the current because the load has been halved. Not all amplifiers take kindly to this increased current demand and some will overheat and shutdown or self-destruct. Some amplifiers are spec'd for bridged operation into 8 ohms only. Classé amplifiers are spec'd for bridged operation into 4 ohms, so you're good. I will leave comments on whether or not to bi-amp Classé and B&W to those who have tried it.

http://sound.westhost.com/patd.htm

Thanks well I never went to High School sorry....

[ryan.devry]

I really can't comment on the different classe amp and which would be better. I actaully have only listen to the CA-2200 once in my life time, and never compared it to anything bi-amped or bridged. My personnal preference is to have mono's for the front channels, and a multichannel for the rest.........

However, I can give you technical insight into bridging channels. This is something I have done with various car amplifiers, and have had very good results.

Just in layman terms, say you have a 100W two channel amplifer running on 10V to drive an 4ohm load. That has the capability to be bridged. (See attach diagram for basic wiring). By paralleling the two channels you double the voltage output of the amplifiers. You combine the inverted signal of one amplifier into the other in a parallel wiring configuration.

The formula for calculating power is

Power = Voltage squared divided by the impedance.
p = v ^2 / R

So, complete the formula:

R = 4 ohm (what the amp sees)

V = 10V -(-10V) = 20V or 40Vpp

P= 40^2/4

P = 400W (4 times the original value)

Hope that isn't to confusing, I tried to simplify a semesters worth of amplification/wiring....

I actually think some manufacturers use this method in creating their mono amplifiers......Not 100% on that, but I think????

[ryan.devry]

Glen B sorry to take you back down high school.......Oh what good days.....I wasn't even going into phase angles or anything of that nature. I was simply explaining the basic concept behind a speaker, and how current is effective.

Also I have to dissagree. You canot make a 8 ohm speaker magically become a 4 ohm speaker....Your not adding impedance to the speaker.....Your merely taking of the voltage.

Some people say that when an amplifier is bridged onto a 8 ohm load, it 'sees' a 4 ohm load. While it is true that the same current flows whether the amp is bridged on a 8 ohm load or a 4 ohm stereo load, the amplifier is driving a 8 ohm load across its outputs. A single 8 ohm speaker can never be a 4 ohm load.

[Orb]

Glen B sorry to take you back down high school.......Oh what good days.....I wasn't even going into phase angles or anything of that nature. I was simply explaining the basic concept behind a speaker, and how current is effective.

Also I have to dissagree. You canot make a 8 ohm speaker magically become a 4 ohm speaker....Your not adding impedance to the speaker.....Your merely taking of the voltage.

Some people say that when an amplifier is bridged onto a 8 ohm load, it 'sees' a 4 ohm load. While it is true that the same current flows whether the amp is bridged on a 8 ohm load or a 4 ohm stereo load, the amplifier is driving a 8 ohm load across its outputs. A single 8 ohm speaker can never be a 4 ohm load.

Although Glen B is specifically talking about bridge mode of amps, and this does half the ohm load for the reasons he mentions.
One of the reasons I tend to avoid bridging and surprised Denon,etc quite happily recommend it with their 8 or 10 channel amps when you consider many speakers have an average impedance between 4 to 5 ohms.
This then presents 2 to 2.5ohm.

I see we are talking semantics mostly, yes the speaker is still 8ohms but bridging presents 4ohms (as an example) and more stress to the amp.

Cheers
Orb

[wettou]

So bridging is not recommended then! Any one compared bridging with Bi-amping?

[ryan.devry]

Orb

I see we are talking semantics mostly, yes the speaker is still 8ohms but bridging presents 4ohms (as an example) and more stress to the amp.

AGREED...

[ryan.devry]

about speaker cable.....Thats a another highly discussed/debated topic. Obviously conduct sizing place a role, and the conductor material itself.....then you can get into low pass filter, and manufacting methods, etc.....Just to make it simple if buying nice equipment....buy a quality cables.

I could tell a huge difference from radio shack 12guage cable to my current MIT terminator cables on my old psb 6t speakers.....

[wettou]

about speaker cable.....Thats a another highly discussed/debated topic. Obviously conduct sizing place a role, and the conductor material itself.....then you can get into low pass filter, and manufacting methods, etc.....Just to make it simple if buying nice equipment....buy a quality cables. I could tell a huge difference from radio shack 12guage cable to my current MIT terminator cables on my old psb 6t speakers.....

That is where I have issues, I compared monoprice cable to a high end brand costing $1000/foot and could not hear a difference!

The dealer wanted me to be impressed so he loaned them to me for a month When I told him no thanks he was very disapointed never spoke to me ever since :roll:

[ryan.devry]

I don't think I would spend 1000 a foot..........lol......