|   Audio Beginner with questions | n2s2
Apr 14, 2003 9:15 PM | | Hello all. Recently I inhereted a lot of audio equipment from my father from record player to an odd looking sony cd player. I have set up my home audio system to the best of ability but I have serious doubts that I am getting all the sound out of my speakers and sytem. First off I wanted know the importance of voltage and wattage in an amplifier. I have an NAD Stero Amplifier 3125 (its an integrated amp). Then I wanted to know about ohms and impedence. I have two 1970 type old speakers that seem to have been made in Japan. On the back it says that its maximum input is 150W and its rated impedence is 6ohms. On my amp it only has a switch that goes from 8ohms to 4ohms. Also on the back of the speaker it says something about 300W but since it is Japanese I can not read it.
Any help will be appreciated |
| re: Audio Beginner with questions | Kursun
Apr 15, 2003 6:57 AM | | If may find the post by Karl on "Tweaks, Mods and DIY" forum quite informative on the subject of power and impedance.
http://forums14.consumerreview.com/crforum?viewall@@.ef9a04e
Impedance-wise I don't think you have a problem. I would keep the impedance switch on the back of you amp at 8 ohm setting and look for any problem of over-heating at normal listening levels. Personally I don't like such switches on amplifiers. Unless it's a tube amp, IMO it means the manufacturer doesn't much trust the power supply and output transistors in their amplifiers.
You may try different locations for your speakers. Keep the speakers away from corners, otherwise bass will be boomy. Speakers may sound very different at each location in the room you try. The tweeters and midrange speakers should be at the same height as your ear at your normal listening position. |
| Inscruitable, n2s2-san? | Mash
Apr 15, 2003 7:03 PM | | The switch on the rear of your amp MUST be set to 4 ohms for 4 OR 6 ohm speakers. The switch on the rear of your amp can be set to 8 ohms for 8 ohm, or higher, speakers. Otherwise, you may start smelling something. And it won't be coffee.
Who knows about the speakers.... How do they sound, and are the cone surrounds good? The "300 W" may be a peak or music power rating and "150 W" may be continuous power.
Power = Voltage^2/resistance
and
Power = Current^2 * resistance
Excessive current will fry a solid state amp because transistors have a negative resistance versus temperature curve: the hotter transistors get the lower their resistance and so for a given voltage the more power they produce- until they fry. Most amps, not all, are constant voltage source, just like your wall plugs. So keep your amp output switch at 4 ohms for your 6 ohm speakers.... |
| 4 & 8 Ohms | Kursun
Apr 15, 2003 11:29 PM | | I get the impression you believe speakers are either 4 Ohms or 8 Ohms, period. That is not the case in real life. A speaker's impedance may vary from 3 Ohm to 40 Ohm on its impedance-vs-frequency plot. The same loudspeaker may be rated as 8 Ohms nominal or even 4 Ohms nominal, by its manufacturer. Loudspeaker impedance rating is a joke in many cases. The correct way would be to set the so called impedance switch to 8 at first and observe the amplifier. Unless it over-heats there would be no reason to change its position to 4 Ohms.
The 4 Ohm position generally lowers amplifier rail voltage slightly, limiting its maximum output. In this case you may get more risks of clipping the amplifier and the smell you'll get won't be the coffee but the voice coil windings of your tweeter burning. |
| Fiddlesticks! | Mash
Apr 16, 2003 5:17 PM | | The user's manual will state, if the amp's owner could find it, that the amp's designers intended the switch to be set to 4 ohms for speakers of less than 8 ohms i.e. 4 to 6 ohms. For speakers of 8 ohms or higher, the owner should use the 8 ohm position. So speaker resistance varies a bit. So what. This is taken into account by the amp's designers. The tweeters are not at risk.
The key point is to match the speaker to the amp when necessary, and it is necessary when the amp has that little 4 ohm - 8 ohm speaker selector switch. Always follow the design intent of those who designed the unit. People who fail to follow the design intent usually get into trouble. This is another way to say "Read and Follow the Directions!" |
| Fiddlesticks! | Kursun
Apr 17, 2003 1:31 AM | | (1) Anybody in this forum will tell you 6 Ohm speakers are OK to use with 8 Ohm position.
(2) Nad is a respected company known for conservatively underrating its products. They probably put that switch to prevent severe abuse of its product by the completely uninformed.
(3) Following the instructions is good behavior, but knowing what you are doing is even better.
The correct way is to use the 6 Ohm speakers with the 8 ohm setting on the amplifier and observe for any over-heating problems at normal listening conditions. ***In fact this is the recommended procedure even for using 8 speakers on 8 ohm taps.***
The use of the 4 Ohm setting on the switch for 6 Ohm speakers will cripple your amplifier unnecessarily as its maximum undistorted power output capacity will drop to as much as half its capacity in 8 Ohm setting. I see your "So speaker resistance varies a bit." a great understatement. You should study more about loudspeaker behavior. BTW tweeters are at a great risk when used with underpowered amplifiers.
A less respected practice in wiring the 4-8 Ohm impedance switch would be inserting a series resistor between the amplifier and speaker, and that would demolish the damping factor. |
| What the people on this forum 'say' | Mash
Apr 17, 2003 3:02 AM | | is irrelevant in the end because neither they, nor you, will buy n2s2 a new amplifier should his following your suggestions damage his amplifier.
B/t/w I have probably forgotten more about loudspealers than you have ever learned. I even made my own planar dynamic for ha-ha's.
I have U.S. & international patents which are in production so I am also quite practical. Anyone who thinks they know more than the people who actually designed the equipment should go into business building and selling their own lines of equipment. That is how you get rich!
Otherwise: "ALWAYS READ and FOLLOW the DIRECTIONS!" |
| What the people on this forum 'say' | Kursun
Apr 17, 2003 3:56 AM | | I think you are a naive, unpolite person and need a lot to learn. I wonder what a person like you doing in a nice place like this. |
| Ummm... another Q... | n2s2
Apr 17, 2003 9:46 AM | | Mash and Kursun I want to thank both of you for your input its given lots of help. With the advice given I seem to have gotten better high range and midrange sound. I think I still have a problem as my bass seems lacking. This is some more information I got on the speakers. They are from the 1970's, they have been recently reconed 1 month ago. The name, model of the speaker is "Victor Zero fince model 50". The woofer in the floor standing speakers is a 10-12 inch JVC in some kind of metal cradle. THe speaker has a squarish looking tweeter a round domed mid ranged speaker and the 10ish woofer. It also has a hole for the air and it has two switches one for the high range and one for the midrange. I can up the db of both by +1 or reduce both by minus 1 db or minus 3 db. I have no idea what they do. The cords I use between my eequipment and my speakers are just normal cheap wires.
I am not sure if this has any relavence but on the back of my amp where I put in the wires from the speakers it looks like this
(the zeros are where I can but the speakers in)
speaker A: 0 0 0 0
red black black red
speaker B: 0 0 0 0
red black black red
Im not really sure where to exactly put them.
Thank you for any replies. |
| Ummm... another Q... | Kursun
Apr 17, 2003 10:46 AM | | I am not familiar with your speakers or amplifier. Two probabilities come to mind:
1- Check if you have wired your speakers in phase. Connect speaker wires red-to-red (or "+" marked) and black-to-black post for both speakers. If one of the speakers is wired in reverse with respect to other phase cancellations will occur.
2- On the front panel of the amplifier look for a switch labeled "subsonic filter". Many older amplifiers (especially British amps) had one to filter turntable rumble. If there is one, turn it off.
If your speakers are wired in phase and your amp doesn't have any subsonic filter, you may try moving the speaker closer to the wall or corners. You may also try attenuating the midrange and the tweeter using the front panel switches on the speakers. |
| something I forgot | n2s2
Apr 17, 2003 11:19 AM | | My amp is integrated so I dont think I have that.
And MY speaker wires are long really long at around 30 feet. |
| something I forgot | Kursun
Apr 17, 2003 1:15 PM | | You don't think you have subsonic filter? No, an integrated amplifier may have one, a pre-amplifier too may have one. Just look at the front panel and see if there is a switch labeled as subsonic/infrasonic/high-pass/rumble filter.
Have you checked your speaker wiring polarity? If your cables are coded (eg. one line red) it should be easy to check just visually.
I don't believe in fancy wires. Just any good wire with enough cross section (gauge) should be OK. It should be thick so it doesn't introduce its resistance between the amplifier and the speaker. I also prefer speaker cables that have their individual lines slightly spaced apart so that capacitance between the two is low.
30 feet is long. If you must run that long the least you can do is to use thick cables (~12 gauge) and not pile up any extra length behind the speaker. Piling up the cable introduces inductance (coils) into the circuit. |
| Got Pudding ? | Mash
Apr 17, 2003 6:33 PM | | "(1) Anybody in this forum will tell you 6 Ohm speakers are OK to use with 8 Ohm position. "
I won't. So "Anybody in this forum ...." is not true.
"(2) Nad is a respected company known for conservatively underrating its products. They probably put that switch to prevent severe abuse of its product by the completely uninformed. "
"They probably put that switch..." In other words, you do not even know exactly why the switch is there? Then... you presume to tell someone how to use it?
Aahhh: "to prevent severe abuse of its product by the completely uninformed. " That sorta speaks for itself...
Reminds me of the song "Don't Let the Smoke get in Your Eyes".
"(3) Following the instructions is good behavior, but knowing what you are doing is even better."
The second part is not proven.
"The correct way is to use the 6 Ohm speakers with the 8 ohm setting on the amplifier and observe for any over-heating problems at normal listening conditions. ***In fact this is the recommended procedure even for using 8 speakers on 8 ohm taps.*** "
How does one observe "for any over-heating problems at normal listening conditions." ??
Oh, yea.... The smoke! Now I get it! "Don't Let the Smoke get in Your Eyes", second verse!
"The use of the 4 Ohm setting on the switch for 6 Ohm speakers will cripple your amplifier unnecessarily as its maximum undistorted power output capacity will drop to as much as half its capacity in 8 Ohm setting. I see your "So speaker resistance varies a bit." a great understatement. You should study more about loudspeaker behavior. BTW tweeters are at a great risk when used with underpowered amplifiers." This does not make sense...
You presume to tell me "You should study more about loudspeaker behavior." And now you call me rude? My friend, I am very well versed in structural dynamics and forced response. Very well versed. I even have some basic propeller blade retention patents to prove it, and speakers are very simple compared to propeller blades.
"A less respected practice in wiring the 4-8 Ohm impedance switch would be inserting a series resistor between the amplifier and speaker, and that would demolish the damping factor."
This is nonsense.
Ahhh, well. My evening's entertainment, I guess.
I have had audiophiles stand slack-jawed and speechless for the first five minutes that they heard my 1400 watt tube-plus-transistor system which can hit 20 hz without strain. The proof is in the pudding, friend, and I have the pudding. Tell me, have any audiophiles been left speechless by your rig? Got pudding? |
| I for one... | igor
Apr 17, 2003 1:24 PM | | agree with Kursun. I would keep the amp using the 8 ohm switch. If I used speakers that were inefficient like planars or Dynaudio, 4 ohm speakers, then I would use the 4 ohm swith. But 6 ohm isn't enough to go there. Not a big deal really, and I don't think we are helping the original poster too much with this debate. |
| I agree except the statement about amp clipping | Richard Greene
Apr 21, 2003 8:41 AM | | High frequency harmonics as a result of intermittent amplifier clipping account for perhaps 5% of the power going to a tweeter's voice coil ... yet for some reason seem to get 95% of the blame when a tweeter's voice coil
is damaged.
I recommend the impedance switch set at 8 ohms unless the amp case is very hot to the touch after at least 30 minutes of use. |
| I would agree with Mash that..... | arc_light
Apr 17, 2003 4:59 PM | | you'd want to set the switch to 4. I would think that in the 8 position the circuitry expects to see a higher load resistance and hence permits a higher current output, that might damage a 6 ohm speaker.
On the other hand, I wasn't aware that widespread discoveries have been made that required changes to Ohms law since I went to school.
Resistance now falls as temperature rises? Transistors make power now?
Just goes to show, the more you learn, the more apparent it becomes just how little you really know. |
| I would agree with Mash that..... | Mash
Apr 17, 2003 5:33 PM | | Ohm's law does not address the effects of temperature.... Only that current must be preserved. Then add the specified relationships between I, V, and R, and power....
"Resistance now falls as temperature rises?" For transistors, yes. Cool, huh? That is why transistor amps usually have protective circuits. The transistors could otherwise "run away" with themselves.... a lonely trip. For conductors in general, resistance usually rises with the conductor's temperature.
Your comment about the switch position is correct. The amp discussed may be a '70's or early '80's vintage... Most tube amps were transformer coupled and they had seperate output taps for 4 & 8 ohm speakers which allowed the speakers to be connected to the appropriate transformer secondary ratio. Using an 8 ohm transformer tap with a 4 ohm speaker made the amp unhappy which could lead to an unhappy owner. But connecting a 4 ohm transformer tap with an 8 ohm speaker was fine- just a slight loss of power that many audiophiles considered a favorable trade for less distortion.
And all transistor amps have "power transistors", and almost all transistor amps (I know of no exceptions but there must be a few...) operate as constant voltage sources, hence Power = Voltage x Voltage / Resistance. |
| I suppose the term power transistor..... | arc_light
Apr 17, 2003 7:30 PM | | is a a bit of a misnomer then? Are they not just switches, or rather shunts that modulate their "output" from an input source fed them, by introducing this source to a variable range of resistances as is needed while it passes through?
So these control/protective circuits must be akin to pilot valves or rather, a load shunt/dump activated in response to temperature/overtemperature? A mini bi-metallic strip derailler?
Self operating, no input control signal from another device? |
| OK, OK ..... | Mash
Apr 18, 2003 7:05 PM | | the "Power" really comes from an air-cooled, hydrogen-cooled, or, in a nuclear plant, a hydrogen-AND-water-cooled, 3-phase generator driven by its prime moover, a gas turbine, a steam turbine, or even a water-tubrbine at a dam. But the amp's 'power transistor' controls (gates) the power fed to the speaker from the amps innerards according to the input signal fed to the amp. You hope.
Amps are like refrigerators: Most of us pay them no mind, until they stop working....
And I believe a lot of folk think they need more powerful amps than they really do need. But then, I am partial to class-A amps, and since class-A amps chew up their full power rating all the time that they are 'on', an 'oversized' class-A amp is a definite "power-bill liability". |
| Please stop now...you're makin' me all verklempt ..... | arc_light
Apr 18, 2003 10:52 PM | | Steam generators and their related auxilliaries are among the things most dear to my heart.
Talk amongst yourselves. |
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