PDA

View Full Version : speaker ohms



ozboater
08-19-2009, 01:21 PM
i realise that this isn t an electrical question but it relates in some way ( i guess) :)... i have a new set of outdoor speakers that i want to connect to an old sony mini hifi... the sony has a pair of 6 ohm speakers and the amp is about 40 watts RMS... i d like to connect the second set of outdoor speakers with a speaker selector switch...one that will allow me to select A / B and A+B...

anyway, the outdoor speakers are 8 ohm... are there any potential problems hooking up speakers with different ohms ???

thanks for any advice / help

cheers

oz

domwilson
08-19-2009, 01:35 PM
What is the impedance of the other set of speakers? Are you planning on playing both sets simultaneously? Are you planning on playing them loud? Some amps become unstable or can be damaged with too low of impedance speakers. This is a complex topic. I can answer you better with more detail.

Jeff Wohlt
08-19-2009, 02:19 PM
You can go that way with a switch. 8 ohm is fine if it really is a 6 ohm set up...which is kinda odd. You will only notice the 8 ohm slightly lower in volume.

Now with out a switch and you add speaker in para then a 4 ohm system then becomes a 2 ohm and that can burn amps. My kid did that with his little room stereo and after you play it hard and loud it will shut down.

If you drive both A&B at the same time I would not play it loud or try to push any big watts thru them.

Of course, if you are playing Bethoven (SP)and all that kind of music then it will burn up anyway :banana::just-kidding:

It will be just fine as long as you play classic rock from the 60s-80s....har-har-har.

Flying Scotsman
08-19-2009, 04:09 PM
Douggie the HiFi "expert" will try to explain...speakers rated with a low ohm rating are easier to drive than those with high ohm rating. Car speakers are a perfect example, they are usually rated at 4 ohms and can be driven to high volumes with a crappy transistor amp but can not produce realistic base boom boom ...look inside and you will see chips that provide the amplication, not good. the ohm rating changes dramitically upon the frequency response...low frequency creates the highest demand on the amp. That is why a speaker with a high ohm rating and a low hertz rating requires a quality amp to produce the best overall sound. You will put a huge demand on that amp running 4 speakers

Douggie

ozboater
08-19-2009, 04:13 PM
thanks gents...

the old speakers and i presume amp is rated at 6 ohms... the new outdoor speakers are 8 ohms...

yeah, i plan to use them together mainly (A + B)... occasionally i ll run them as pairs, either the outdoor ones in the garden and the old sonys in the man cave.... mainly playing together tho...

it s mainly to listen to internet streaming radio from australia so cranking it up doesn t really come into the picure... mainly talk radio etc... 702 sydney... great stuff... abc.net.au/streaming

i ll crank the rock upstairs on the big jbls and polks...

so you blokes reckon i ll be ok then... any idea where i can pick up a stereo selector switch ?? i ve seen on at radio shack that allows the hook up of four sets of speakers but i m not sure if it ll allow you to play two or more sets together... plus i only want two sets of speakers hooked up - not 4...

thanks again for the help men... much appreciated

oz

domwilson
08-19-2009, 04:27 PM
You should be ok as long as you don't crank it. Speaker impedance is a nominal figure as speakers present a very complex load to the amplifier. But just like boats, Watch the temps...:banana:

egneg
08-19-2009, 04:44 PM
All you need are 2 DPST switches and a plastic box to make it yourself.

http://www.radioshack.com/family/index.jsp?categoryId=2032278&allCount=91&fbc=1&f=PAD%2FProduct+Type%2FDPST&fbn=Type%2FDPST

http://www.radioshack.com/product/index.jsp?productId=2062279

Flying Scotsman
08-19-2009, 04:54 PM
As an aside, most mass market amp specs are rubbish and all they can do is drive a resistor at 8 ohms. In the real world they fail to live up to their promise, and as has been mentioned speakers and amps, like FE motors depend on the setup to live up to their credentials

Douggie

ozboater
08-19-2009, 06:23 PM
you blokes are awesome... thanks heaps... that looks like a good solution egneg, unfortunately i have no idea how to solder it together... soldering i can handle but the hook up has me baffled... any chance you could draw me up a quick wiring diag?? big ask i know but without one i m shot... sure looks like a cheaper and better solution than the 4 way radioshack thing i was looking at... plus it ll save me about 35 bucks...

with the dpst stiches i ll be able to run the speakers in the A / B , or A+B set up yeah ??

cheers

oz

egneg
08-19-2009, 07:19 PM
Yes you can choose a/b or a+b. Give me a bit of time and I will draw up the diagram.

Flying Scotsman
08-19-2009, 07:40 PM
i realise that this isn t an electrical question but it relates in some way ( i guess) :)... i have a new set of outdoor speakers that i want to connect to an old sony mini hifi... the sony has a pair of 6 ohm speakers and the amp is about 40 watts RMS... i d like to connect the second set of outdoor speakers with a speaker selector switch...one that will allow me to select A / B and A+B...

anyway, the outdoor speakers are 8 ohm... are there any potential problems hooking up speakers with different ohms ???

thanks for any advice / help

cheers

oz

It is very easy to wire think and what switch. Yes I am being nasty

Dougggie

ozboater
08-20-2009, 12:19 AM
cheers egneg, i apprectate it... i could get it eventually but it d need to be resoldered at least 35 times... good on ya mate..


douggie :thumbup::thumbsdown:

egneg
08-20-2009, 03:38 PM
Here it is Oz.

ozboater
08-20-2009, 09:43 PM
cheers egneg... awesome... i reckon i got it now... i ll post ya the results.. :tiphat:

linnmajik
08-23-2009, 10:48 PM
OK, I'm glad I found this thread. I've gone to school for electrical engineering and have actually installed home theatre systems that sold for over $200,000. Let me begin by helping to reduce some confusion. I may repeat some things that were already said but this should be very helpful in summing up everything in one thread.


I don’t have time to write this perfectly so some parts may be point form.
This paragraph is my basic answer to the thread (I will expand and explain afterwards):

There is no problem with hooking up speakers with different ohm ratings as long as the total load impedance doesn’t drop below what the amplifier is designed for. The safest way to do the switching is to buy an impedance-matching speaker switcher. You can buy one that will allow the Sony to “see” 6 or 8 ohms - even when you are running both sets of speakers at the same time. I believe companies like Q.E.D. and Russound have these switchers.

Ohm’s law: As resistance (or in AC circuits - impedance) decreases, current increases.

As impedance drops, the circuit gets closer and closer to being shorted. This increases the current demands from the amplifier. Most amplifiers are current-limited and are not stable driving low impedance speakers (or a combination of speaker pairs that allow the amp to “see” a low impedance circuit) Since Sony mini systems have almost no current reserve, keeping the impedance high is much easier for the amplifier to drive.

Two sets of 8 ohm speakers switched on in a series circuit, the amplifier sees 16 ohms. Two sets of 8 ohm speakers switched on in parallel, the amp sees 4 ohms (current demand is 4 times that of the series circuit - but more voltage is required)


Ohm rating is nominal, impedance fluctuates with frequency. An 8 ohm speaker can be as low as 3 ohms at a certain frequency and some have been measured as high as 70 ohms at certain frequencies. At low ohms, the amplifier needs to swing large current, at high ohms, it needs to apply high voltage (to make up for the large voltage drop across 70 ohms)


Douggie,

Low impedence speakers are HARDER to drive than high impedence. Car speakers are 4 ohm because high impedence causes voltage drop and the power supply “rails” in a car amp operate at a lower voltage than a house amp. LOW ohm rating and low frequency is the most difficult - massive current demands and the amp has to control a larger moving mass with more back EMF. You are right about the specs of mass produced amps - it got even worse when home theatre came out - An amplifier that draws 150 watts from my wall outlet can’t put 110 watts out to each of my 5 speakers at the same time. Its all lies. And, in most situations, power has absolutely no bearing on performance. It all demands on how well the amp was made. I’ve heard great sounding 20 watt amps and terrible sounding 100 watt amps.

Jeff,

8 ohm speakers are not lower in volume than 6 ohm - their volume has to do with input power and efficiency, not their impedance. Current does not provide loudness, the product of current and voltage is power, which, combined with the speaker’s efficiency make it play at a certain volume.

If someone does have low impedance speakers, it is better if they have high efficiency.
A 90db speaker will require half the amount of power to get to the same volume as an 87db speaker. (A 90db speaker at 50 watts will play as loud as an 87db speaker at 100 Watts.)

A 4 ohm 90 db speaker can sometimes be as easy to drive as an 8 ohm 87db, but there are a lot of variables.

Egneg,

Your diagram is a parallel connection with no impedance matching, switching A + B and running at the same time, the Sony will see 3.4 ohms, "high-end" Sony ES amps can barely handle this.


Keep volume very, very low. (Which could be difficult outdoors)


I wish I was a better writer, but I can expand on everything later, I have to go.

domwilson
08-23-2009, 11:40 PM
OK, I'm glad I found this thread. I've gone to school for electrical engineering and have actually installed home theatre systems that sold for over $200,000. Let me begin by helping to reduce some confusion. I may repeat some things that were already said but this should be very helpful in summing up everything in one thread.


I don’t have time to write this perfectly so some parts may be point form.
This paragraph is my basic answer to the thread (I will expand and explain afterwards):

There is no problem with hooking up speakers with different ohm ratings as long as the total load impedance doesn’t drop below what the amplifier is designed for. The safest way to do the switching is to buy an impedance-matching speaker switcher. You can buy one that will allow the Sony to “see” 6 or 8 ohms - even when you are running both sets of speakers at the same time. I believe companies like Q.E.D. and Russound have these switchers.

Ohm’s law: As resistance (or in AC circuits - impedance) decreases, current increases.

As impedance drops, the circuit gets closer and closer to being shorted. This increases the current demands from the amplifier. Most amplifiers are current-limited and are not stable driving low impedance speakers (or a combination of speaker pairs that allow the amp to “see” a low impedance circuit) Since Sony mini systems have almost no current reserve, keeping the impedance high is much easier for the amplifier to drive.

Two sets of 8 ohm speakers switched on in a series circuit, the amplifier sees 16 ohms. Two sets of 8 ohm speakers switched on in parallel, the amp sees 4 ohms (current demand is 4 times that of the series circuit - but more voltage is required)


Ohm rating is nominal, impedance fluctuates with frequency. An 8 ohm speaker can be as low as 3 ohms at a certain frequency and some have been measured as high as 70 ohms at certain frequencies. At low ohms, the amplifier needs to swing large current, at high ohms, it needs to apply high voltage (to make up for the large voltage drop across 70 ohms)


Douggie,

Low impedence speakers are HARDER to drive than high impedence. Car speakers are 4 ohm because high impedence causes voltage drop and the power supply “rails” in a car amp operate at a lower voltage than a house amp. LOW ohm rating and low frequency is the most difficult - massive current demands and the amp has to control a larger moving mass with more back EMF. You are right about the specs of mass produced amps - it got even worse when home theatre came out - An amplifier that draws 150 watts from my wall outlet can’t put 110 watts out to each of my 5 speakers at the same time. Its all lies. And, in most situations, power has absolutely no bearing on performance. It all demands on how well the amp was made. I’ve heard great sounding 20 watt amps and terrible sounding 100 watt amps.

Jeff,

8 ohm speakers are not lower in volume than 6 ohm - their volume has to do with input power and efficiency, not their impedance. Current does not provide loudness, the product of current and voltage is power, which, combined with the speaker’s efficiency make it play at a certain volume.

If someone does have low impedance speakers, it is better if they have high efficiency.
A 90db speaker will require half the amount of power to get to the same volume as an 87db speaker. (A 90db speaker at 50 watts will play as loud as an 87db speaker at 100 Watts.)

A 4 ohm 90 db speaker can sometimes be as easy to drive as an 8 ohm 87db, but there are a lot of variables.

Egneg,

Your diagram is a parallel connection with no impedance matching, switching A + B and running at the same time, the Sony will see 3.4 ohms, "high-end" Sony ES amps can barely handle this.


Keep volume very, very low. (Which could be difficult outdoors)


I wish I was a better writer, but I can expand on everything later, I have to go.

Very good answer. I went to school and was engineer tech for a number of years. I repair equipment and design, build speakers as a hobby now. His answer is spot on.

ozboater
08-23-2009, 11:55 PM
my brain hurts :)

thanks lads, i have some work to do i guess...

Brod
09-05-2009, 11:38 AM
Linn is right ,higher impedance speakers are a kinder load to amplifiers,its the low impedance ones that need quality amps.
A decent amp should double the output at half the oms,rarely do.
Some people spend thousands on amplifiers that will do just that.
Class A is the way to go,very expensive,run very hot too.
I used to design and build valve amps,all triodes,the best sounding ones are low powered stuff with very high effiency horn speakers,my Klipch horns were 103db at one amp.
Awesome sounds..
See your name Linn majic? all Linn gear??
Brod..

Flying Scotsman
09-05-2009, 12:04 PM
Brod, I was never a fan of Klipch horn tweeters, but they could produce amazing volume with a quality amp. My first system was Marantz amplification with Celestion Ditton 66 speakers and a Thorens turntable. When I was stating the info on car speakers I neglected to state their frequency response which will never be 20hz to 20khz and above that is why I stated they are easier to drive. Yes 4ohm speakers rated at this frequency will put a huge demand on the amp...sorry for any confusion and as previously mentioned 12 volts will not provide the claims of many car amp specs

Douggie

linnmajik
09-05-2009, 12:45 PM
Linn is right ,higher impedance speakers are a kinder load to amplifiers,its the low impedance ones that need quality amps.
A decent amp should double the output at half the oms,rarely do.
Some people spend thousands on amplifiers that will do just that.
Class A is the way to go,very expensive,run very hot too.
I used to design and build valve amps,all triodes,the best sounding ones are low powered stuff with very high effiency horn speakers,my Klipch horns were 103db at one amp.
Awesome sounds..
See your name Linn majic? all Linn gear??
Brod..

Yes, one of my systems is all Linn gear. Linn Majik, Mimik, Pekin, LK85, and Ninka.
I have Yamaha, Thiel, Marantz, and PSB in other setups.

Greg

Brod
09-06-2009, 01:11 PM
Yes, one of my systems is all Linn gear. Linn Majik, Mimik, Pekin, LK85, and Ninka.
I have Yamaha, Thiel, Marantz, and PSB in other setups.

Greg

No LP 12!!!

My best ever system was a Pinktriangle turntable,SME IV,MC1 coil,MC5000 transformer,home made Phono amp,home made 300btriode single ended amp,Klipsch escalas.
The Triode amp had 4 separate choke power supplies,very transparent, very dynamic sound..
CD was a Micromega drive and dac.
Sadly the lot was sold,regret it every day..
Brod..

domwilson
09-06-2009, 01:27 PM
For me, It was old H.H. Scott and Bogen tube amps and home made speakers. Sound was so clean, vocals would be as if they were right there in the room. Of course that depended on the recording.

Flying Scotsman
09-06-2009, 02:17 PM
No LP 12!!!

My best ever system was a Pinktriangle turntable,SME IV,MC1 coil,MC5000 transformer,home made Phono amp,home made 300btriode single ended amp,Klipsch escalas.
The Triode amp had 4 separate choke power supplies,very transparent, very dynamic sound..
CD was a Micromega drive and dac.
Sadly the lot was sold,regret it every day..
Brod..

A very cool system..I still have a Dunlop Systemdek..circa 1980 with a highly modified Rega RB 300 arm and an AT-0C9mc cartridge. The Dunlop turntable was a $100 cheaper than a Linn LP12 at that time but I thought it was a better design and sounded as good with Grace 707 arms, both were Scottish designed and manufactured...say no more :olleyes:

Douggie

domwilson
09-06-2009, 02:43 PM
A very cool system..I still have a Dunlop Systemdek..circa 1980 with a highly modified Rega RB 300 arm and an AT-0C9mc cartridge. The Dunlop turntable was a $100 cheaper than a Linn LP12 at that time but I thought it was a better design and sounded as good with Grace 707 arms, both were Scottish designed and manufactured...say no more :olleyes:

Douggie

A very nice turntable indeed.

linnmajik
09-08-2009, 10:28 PM
No LP 12!!!

My best ever system was a Pinktriangle turntable,SME IV,MC1 coil,MC5000 transformer,home made Phono amp,home made 300btriode single ended amp,Klipsch escalas.
The Triode amp had 4 separate choke power supplies,very transparent, very dynamic sound..
CD was a Micromega drive and dac.
Sadly the lot was sold,regret it every day..
Brod..


Hi,

No LP12 - No turntable at the moment. I used to have a Philips table and an NAD (which I think was a Rega). My main source is CD right now, I like the convenience of it - but I understand why so many people love turntables. I've heard some amazing systems and a high-end turntable makes a great musical front end - many cd players just make me lose interest in the music - except when I heard Linn's CD12 cd player but they sold for about $29,000 here.

Greg

domwilson
09-09-2009, 12:58 AM
It seems the older "vintage" equipment reproduce recordings better than the newer mass market produced equipment of today.

Meniscus
09-09-2009, 01:18 PM
Linn,

I think you'll find there are many audio engineering types here. Welcome to OSE.

How much have you worked with capacitors in analog circuits? I find over and over that even when working on Neve and other audio gear, what it really comes down to is the capacitors and the circuit design. I'm not denying the differences of a Class A amp over another, but if you don't already know, there are many modifications that can easily be made to have much more efficient reproduction of sound.

Going back to who knows when, maybe circa late 60's, I have some fairly small wood grate 35-40watt passive speakers that sound absolutely amazing. Thing is, they take roughly 45mins to warm up and even out the frequency response. The moral is, just because something may not have cost very much originally, it may be just what you are looking to hear and ultimately, it all comes down to your perception of the sound, influenced by the shape of your ear, how much weedeating you did as a kid and whether or not you put ear plugs in when you use the dremel or chainsaw for that matter! LOL

Flying Scotsman
09-09-2009, 01:47 PM
There is a lot of hype today on the vinyl versus Cd versus MP3 etc.

All I can state that original stereo and even mono vinyl records are way better sounding than the compressed sounds of today. Some times new technology is crap

Edit

Note that Linn changed the Audio world and a cheap turntable/cartridge today will not give you that pleasure of fantastic sound married with a good amp and speakers

Douggie

Brod
09-09-2009, 02:43 PM
Regarding analogue circuits, i found when designing circuits the best sound was obtained by paying more attention to the power supply.Choke coupled power supplies give the most dynamic sound,of course putting quality caps on the line made huge differences too,especially output caps.
My home use valve circuits use real expensive Blackgate power caps and a mix of silver foil output caps,plus heavy use of 99.9999% silver solder,all hard wired together,ie no circuit boards..
The simplest circuits too ie single ended designs,no feedback also sound the most natural.
Music contains mostly midrange frequencies which the ear is the most sensitive to,get the midrange clean and smooth and it will sound well.
That is why valves sound natural,they excel at midrange frequencies.

Vinyl,with a correctly set up turntable,will always sound better,containing much more information than any cd recording.
The tiny grooves and mounds on a vinyl record can go down to molecular levels given good recording equipment.Something cds can only dream of.

saying that cd is more convenient,last longer and stored easier.
Plus some turntables are hard to setup right and meticulous cleaning of vinyl can sometimes be a real chore when all i want is music.
Brod..

Meniscus
09-09-2009, 03:36 PM
Has anyone kept up with SACD? When the technology first came out, I thought it was a great idea to represent the waveforms in 1's and 0's, resulting in a more accurate waveform.

I haven't kept up with the technology in recent years, but I will say this, I've always loved working with 1/2" tape on two-track mastering reel to reels. We typically use 15 fps (feet per second) rates. Plus you can always hook two of them up and by hand, speed up and slow down for true tape phase effects. LOL

Keep in mind, much of the recordings you have heard in years past as well as today are still recorded on 24 track machines running 2" tape. The sound is/was all analog, before they were ever put into other formats. .....Does it make a difference? Of course it does!.....

Flying Scotsman
09-09-2009, 03:43 PM
That is why valves sound natural,they excel at midrange frequencies.

Vinyl,with a correctly set up turntable,will always sound better,containing much more information than any cd recording.
The tiny grooves and mounds on a vinyl record can go down to molecular levels given good recording equipment.Something cds can only dream of.

saying that cd is more convenient,last longer and stored easier.
Plus some turntables are hard to setup right and meticulous cleaning of vinyl can sometimes be a real chore when all i want is music.
Brod..

Setting up a turntable is much like setting up an FE boat, minor changes on the ballance of the turntable and arm/cartridge settings make at times a huge difference to the performance and it is fantastic to hear the sound change, and yes I own 2 cd players but they do not compare sonically to vinyl

Douggie