My memory is shot- lucky I find my way home everyday.
But- my newest (noobie) ? is:Why should I care if my speakers are 4 or 8ohm?
I have the 950/770 -alas not hooked up yet.
And in line for the M&K 150's for 7.1
Answer has to be 15 words or less- my mind(whats left) tends to wander.
As an aside: I am building a dedicated HT in a new house and am overwhelmed at all the info I'm amassing in regards to equipment.

15 words or less: with the 770, you really don't.

With an amp like the 770, the only reason that you really care is that the power output at 4 ohm is a bit greater (which might make a difference if you had really low efficiency 4 ohm speakers and needed the 300 watts produced by the 770 with a 4 ohm load). With many receivers, however, the built-in amplification may not be able to support a 4 ohm or lower load. Dedicated power amps generally are more robust designs that can handle it.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

Thanks gonk- but to be more precise- I was wondering what the diff. is between having 4 or 8ohm speakers, not so much power consumption.Also- why produce 4ohm speakers- more efficient???
Do they draw more power to run???
anyone,anyone(Ferris Buehler)

15 words or less? The guts inside the 4ohm speakers offer more resistance than the 8ohm speakers. Nothing to do with quality, just electrical resistance. (I went over 15 words).

4 ohms is less resistance than 8 ohms, not more. It is a harder load to drive however, and draws more current from a constant voltage source.

The impedance of a speaker is a design consideration that doesn't really have much to do with the way it sounds.

Hey, I was in a hurry to get to work and was under pressure to get it said in 15 words or less. It is true, E=IR; so 4 ohms is less than 8. I hate it when I screw up like this. However, it still stands true that the ohms rating by a speaker manufacturer has nothing to do with its sound quality.

I was just busting your chops. I know how it feels to screw up, I did it once in 1975.

I never make misteaks.

Jeff Mackwood

Since 1975! That means I can go for 29 more years without the fear of anymore mistakes. That's great news!!!

Well, generally, 4 Ohm speakers present more of a load to an Amplifier and it tends to output higher wattage...
Sorry, 20 words,,,,

Uh, buddy:

A cool thing about 4 ohm speakers is that they will draw more current from your amp meaning that they will be producing more watts.

For example, an Outlaw 770 is rated at 200w x 7 into 8 ohms and 300w x7 into 4 ohms. Because I have all 4 ohm speakers, i'm running at 300 watts per channel instead of the wimpier 200wpc.

-sbc

There are a few real disadvantages about running 4 ohm speakers that offset the power gain. Firstly, the effective damping factor will be halved, since the ratio of cable/amplifier output impedance to speaker impedance is 1/2 what it would be with an 8 ohm speaker. Secondly, cable gauge and length will be more of an issue since twice as much potential current flows into half the load impedance - the cable's resistance effects the circuit by a factor of two. Lastly, most current power amplifiers, even if "rated" into 4 ohms, do not perform as well into this load as into an 8 ohm load. The distortion is usually higher among other things.

A power rating of twice, i.e. 400 watts verses 200 watts will yield a 3db increase in potential dynamic range, assuming the speaker can actually handle it! Almost no current speakers can handle 100 watts of continuous power, let alone 300 watts - they will simply fail outright or warp their voice coil formers.

Another consideration is the fact that by far the highest power demands are in the bass region and if a subwoofer is used in conjunction with bass management, the mains do not need all that much power at all - even 100 watts in a typical home theater is more than enough in most cases.

This used to not be the case in the days of "stereo" - speakers then were much less efficient and were expected to reproduce the entire frequency range. Power amplifiers were only two channels and this allowed a higher current capacity per channel verses a 5 or 7 channel amplifier. You simply have only around 1800 watts available from your AC wall outlet too, and this used to be available for only two channels, not 5 or 7. Stereo power amplifiers used to be built with more output devices per channel, and this translated to more current delivery capability. As a gauge, a "perfect" amplifier should be able to double it's power output for each halving of load impedance. Thus, a 200 watt into 8 ohm amplifier would deliver 400 watts into 4 ohms, and some amplifiers of that era would even deliver 800 watts into 2 ohms.

Yeah, all that other stuff he said. So you're looking at something like 2 db more output. Not all that huge. But you could look at it this way, yours can go to 11!

[This message has been edited by JT Clark (edited May 18, 2004).]

gasp, i think sh said it best about 4vs8 ohm speakers.

You can also increase the volume by doubling your speaker number per channel. For example, you can connect two speakers per channel. ( usually 1 per channel ) If you have a 7 channel amp, you just add 1 more speaker per channel and you can have 14 channels total by using this method to increase overall volume. But, this method put heavy stress on your amp. Make sure your amp can be abused this way. I also abuse my amp this way. and it smells hot from the heat sink!! But it sounds awesome

Do you understand wiring at all? You do not have 14 channels. You still have 7 at most. You can hook up 100 speakers to output of the amp and it will still be 1 channel. Also, you do understand that speakers have and impedance don't you? Amps can only play down so low before they overheat. Also, you understand that the additional speakers will take up additional volume in the room? Most every member here is also concerned with looks to some extent. Also the price of the extra sets. Don't forget setting up a sound stage so that it sounds good.

Ya, sorry about that man. I should say 14 speakers. I know it is the identical signal; you just duplicate the channels, but this method is to increase the overall volume without adding additional amplifiers. Also, additional speakers placed close to the original ones will acoustically couple so they act like a much larger speaker receiving twice the power. I found that using 2 pair of speakers for stereo sounds fuller, louder than using 1 pair. You can put that additional pair on the side wall near your ear height. It sounds better than using 1 pair. For ohm, if you connect two 8 ohm speakers per channel, the amp will see it as 4 ohm load. If you connect two 4 ohm speakers per channel, the amp will see it as 2 ohm load. That's why I said the amp will run hot by using this method. Sorry about confusing, bro.

I wouldn't plan on your amplifier's manufacturer honoring any warranty that might be left - electronics do not like abuse and will just fail, leaving you with no volume at all.

You have to check what your amp can do before you go wiring things up like that. I don't think all speakers can be coupled so easily either. Mine are omnipolar. I doubt the reflections will work exactly the same as before. If you have decent speakers they should be able to get loud enough.

For that "abuse" thing, I was just kidding. My amp never ran "hot"; it is just a little "warm" actually. If I only connect 1 speaker per channel, my amp cold like ice. Speaking honestly, it is totaly safe doing it this way. As long as the resulting load impedance you connect on each channel is 2 ohms or higher and you don't run the amp into clipping. But, if you're not that experienced with sound systems yet or feel insecure doing it this way, you're better off for now just connecting one speaker per channel.



[This message has been edited by theendofday (edited May 24, 2004).]

You can also use this method to duplicate your subwoofer channel. Just make sure you use 8 ohm sub so it is easier on the amp.

>>>As long as the resulting load impedance you connect on each channel is 2 ohms or higher.....<<<<

That's what I was warning against. Almost no home theater amplifiers made today are safe to run with a 2 ohm load - most can do 4 ohms, barely, and many of them have switches that lower the rail voltages for this impedance. This was not the case before home theater came into being when amps could sometimes tolerate loads as low as 1 ohm - but that was then, and this is now.

That's what I was saying too. You have to know your equipment. It's dangerous to just go hooking things up with no idea of its capability. Just going by heat is not a great idea either. Some amps naturally run hotter than others and work just fine. This flying by the seat of the pants method is going to end up costing someone a lot of money.

If for some strange reason you absolutely must run an ultra-low load (2 ohms or less) then you might want to check out a used amp from NAD. I say used because i) I have a few of their older models and I know them to be designed to handle those loads and ii) you can buy them cheap - in case you fry one of them .

However something like the NAD 2200 is pretty much bulletproof. The manufacturer actually rates it down to 2 ohms (800 W/ch dynamic power). Old reviews talk of taking it down to 1 ohm. In all extreme cases its protection circuits will kick in well before anything untowards happens.

As I said, if you must drive a very low impedence load, that's what I'd recommned.

Jeff Mackwood

since most subs are powered these days, yeah you can split the analog out to two different ones. but that isnt what you said, but then again what you said isnt sensible either. i dont mean to be offensive, but it sounds like you dont know what you are talking about.

I was talking about using external amplifier to drive unpowered subwoofer that kind of set up. Why must everyone uses active subs and built in Xovers? You can use a 7 channel amplifier to drive seven 8 ohm unpowered subwoofers. Then, by using this method, add 1 more 8 ohm unpowered subwoofer per channel to form a 4 ohm load on the amp for total 14 subs.



[This message has been edited by theendofday (edited May 25, 2004).]

most subs are powered. who has extra amps for subwoofer use? two reasons why. if i wanted 14 speakers (not 14 subs like you posted in that last line), i would use a distribution amp and not my MUCH MORE EXPENSIVE power amp.

Surely you cannot mean this - what do you mean by "distribution amp"? I think you have your nomenclature seriously mixed up.

Passive subwoofers are actually very common and are what I use. Professional installations are more likely to have passive subwoofers than not, although active subs are more common in the consumer marketplace.

I use a combination of three different types. Passive driven by a dedicated amp/controller, Semi passive with built in plate amp but external active sub controller and then the typical active. I prefer the external amplification and controller.

ok so i meant 14 speakers throughout my house, not in my one room. however that is the only way id have 14, until 14.2 comes out. by distribution, i mean mega-multi channel upwards of this http://www.nadelectronics.com/custom_installation/CI9120_framset.htm .

Professional installations like in a studio yeah maybe, but not a professional installation in your home. Very few people have passive subs in their home. I realize that their are applications of anything, however I tend to speak in terms of Home Audio/Theatre as that is what most people here are interested in. If you cant generalize, then you would never get anywhere by talking. There is always an exception... If passives were so great and common, why not dedicate part of receivers' amps to amplifying subs. Yes, I do realize this can be done with a pre/pro, but we're talking popularity here, i.e. what do most people have... Anyway, I know I am straying away from any sort of point; it is annoying, however, for someone always to specify some single condition where the one time something someone says cannot hold true. Its like someone saying he could never jump that high, and then someone saying if he was on the moon he could... Well, obviously that is true, we aren't on the moon here, nor are we in a professional studio.

Curegeorg

I really don't care what you want to use for your amplification or who has extra amps or who doesn't in order to use this method. All I was trying to say is to give you an example of how someone could increase the overall volume without adding additional amplifiers, since you said "I don't know what I am talking about". Who says you "must" use 7 channels for 14 subs?It was just an example I gave you for better understanding what I was trying to say, since you also said "I am not sensible". You really don't have to copy it or even listen to it if you feel bad about it. I also stated this in my previous post.

There are many ways to patch and duplicate identical signal to different power amps. Why someone must uses a "distribution amp" in order to have your so-called "mega-multi channel". Also, those duplicated speakers are the same signal as the original; they are not new channels. An amp acts as a voltage multiplier. Simply put, it takes the input voltage, multiplies it, and puts it out to drive a loudspeaker. It really doesn't matter what application you want use it for.

No one trying to play "professional" in here; I skimmed few of your previous posts and I can easily see through your knowledge about audio equipments is shallow, limited and still stay in people so-called "Hi-Fi Audiophile" world. I have been to the ultra expensive and terribly overpriced hi-fi audio stores and have NEVER been impressed. I am not talking about local circuit city that kind of store. I'm talking about places that want to sell me an amplifier and a turntable for 20 thousand and speaker cables for $20 a foot those nonsense stuffs. Tell you the truth, the only place I have ever been impressed was in the cinema, studio, and live concert with professional set up. Please remember, there are people who use professional gears in here. When you start talking about people do not know what they are doing when they use pro set up in their home, no one feels comfortable about that. I know you are only interested in home theater, and believe more in “Hi-Fi”. But, please wake up and listen to what people are trying to teach you and learn from those people who know audio better.

I think SVS is hoping people think otherwise with regards to passive subs.

I did not realize that that statement was directed to you. I do however know why you responded, and it is the same reason as I stated above. Making a recommendation to hook additional speakers up to the same speaker terminals where you have other speakers already attached is foolish. (everyone else seemed to agree with their posts) It is dangerous for their gear. You can short out everything by trying to cram too much wire in the terminal and having a couple threads contact elsewhere. Granted you could be using spades or something, but that doesnt mean that the amp still wont be overdrawn and fail. THIS MAY OR MAY NOT BE YOUR APPROACH, but to recommend others to do that is irresponsible.

ill stick by my statement that few people have passive subs in their systems as well. like i also said, there is always an exception to the norm, and to always point that out is annoying, however i guess that is the purpose of forums to explore every angle and im sure ive done so myself.

by you telling me , theendoftheday, that you have been to such and such, had such and such, etc. means nothing. your posts reveal your interest/knowledge in audio (15 on this forum), as do mine (399 on this forum), and we should let them speak for themselves. feel free to read all of my postings, you may just learn something. my comments about your ideas was intended to be a warning for others. goodday to you.

[This message has been edited by curegeorg (edited May 26, 2004).]

Well the reason for the SVS statement was to show that passives are used. Yes, I agree that it is annoying when exceptions are pointed out, but the point was to show that the reasons behind the abundance of actives compared to passives may not be what you think.

I use two 15" passive subs in my room connected to a Samson S-1000 Amp. I changed the VC's from 8 Ohm to 4 Ohm to try and get a few more db out of them. This did give me a slight increase in output, but the amp runs hotter and the circuit breaker in the Panamax 5300 (surge protection) is more likely to trigger. I also have two Mesa/Boogie Strategy 400 amps, for the front and rear channels (old amps are better for old music), and have the capacity to run at either 4 or 8 Ohms. In fact there are multiple outputs for 4 or 8 Ohm devices, but I would never run multiple speakers from a single output. It is just too hard on the equipment and the gain is slight. Maybe I am looking at this from a tainted point of view. I guess if I had a room full of Bo*e speakers adding a couple per channel could possible help. (Sorry the Mean came out again)

The bottom line: Stick with your manufactures recommended values, which is most likely going to be 8 Ohms.

P.S. You can always add more speakers to your system by buying speakers with more drivers in them. You could build your own speakers and use active crossovers for each driver for greater flexibility.


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