Speakers-amplificator match

Alberto86

Alberto86

Active Member
Hello all,

I'm running my klipsch 2.1 with my Mitsubishi da-r17 receiver. So far all good.

I just bought a pair of Klipsch forte II.

Now the question is: how may watts has my ampli has to be to run the 2 pairs of speakers together?

The 2.1 speakers require 85 watts
The forte speakers require 100 watts

My current receiver specs said that it produce 45 watts per channel. Of course that's little to run both those speakers.

As I have to upgrade the ampli I would like 1st to understand what watts range ampli I have to look for and 2nd have some advices about good vintage or new ampli that can fit my situation.

Thanks for your replies in advance.

AB
 
Ps :
Also both pair of speaker have 8ohms resistance.
What kind of ampli would work with this situation?

Thanks a lot in advance for any help!

AB
 
Alberto86 said:
Hello all,

I'm running my klipsch 2.1 with my Mitsubishi da-r17 receiver. So far all good.

I just bought a pair of Klipsch forte II.

Now the question is: how may watts has my ampli has to be to run the 2 pairs of speakers together?

The 2.1 speakers require 85 watts
The forte speakers require 100 watts

My current receiver specs said that it produce 45 watts per channel. Of course that's little to run both those speakers.

As I have to upgrade the ampli I would like 1st to understand what watts range ampli I have to look for and 2nd have some advices about good vintage or new ampli that can fit my situation.

Thanks for your replies in advance.

AB
Click to expand...
No, the Klipsch Forte II speakers do not require 100 watts, nor do the 2.1's require 85 watts. Where in the world did you come up with that bit of rubbish? The Forte speakers are very efficient and can easily be brought to EVICTION NOTICE levels with 10 to 20 watt amplifiers. They sound fantastic with low watt tube amps and many lower watt vintage SS amps/receivers. The other issue is why would you want to run both pair of speakers at the same time?
 
Alberto,
This is where many novices get befuddled... The watts listed on speaker specs, are not a "you need this many" to make the speaker work. Rather the Watts listed is generally a "do not exceed" number. I own Fortes, and a lot of times they are hooked to a ~14 watt amp... and they get plenty loud. When Darkblue asked, "why would you want to run both speakers at once"?... he is probably alluding to the fact that these are very different speakers that will just "get in the way of each other". Comb filtering and such...
Another novice befuddlement : Hey I have these two great speakers, why don't I play them at the same time and get twice the enjoyment? ... well because it rarely works out good, unless you just want loud.
If your receiver only has one set of speaker inputs, then you might just be safer only hooking up one set of speakers to it. Enjoy those Fortes! They are superb-
 
Biscuithead, botrytis,

All is clearer.
Thanks for your comments, I understand more now.
Still is there a way to calculate without measuring, how many watts the speakers can need depending on the volume?
All my questions are related to the following video:

Cheers
 
The first question is how loud do you want listen?

How far way from the speakers will you be?

What is your listening environment? How big is your listening environment?

The important specification is the sensitivity rating of the speaker.

I did not see this mentioned in the video. The sensitivity rating (And it is not efficiency, this is an incorrect term, although it is regularly used. I just mention this to help you get started in the right direction). This specification tells you how loud a speaker will play at a certain distance from the speaker with a certain amount of power applied to the speaker.

The information that you have supplied suggests that your speaker will produce a loudness level of 100 dB (this is rather loud) at a distance of 1 meter from the speaker when the speaker is supplied with 1 watt of power.

10 watts of power would produce a 110 dB loudness 1 meter from the speaker. This is a level that can cause hearing damage. The loudness will decrease the farther that your are from the speaker and it can be roughly calculated.

There are several apps available for smart phones that will allow you the measure the sound pressure, loudness of your music. Although some are not the most accurate, this can give you a reference or starting point.

Then keep in mind, and this relates to how loud you want to listen, it take an increase in power of about 10 times to cause a perceived doubling of the loudness.

Below is some information to help put the numbers into context. These numbers are averages for the average person. For some the risk may be greater and for a few not so much, but it is safe to say that hopping that you may be one of the ones that can withstand higher levels is not a good idea.

upload_2017-4-27_5-18-20.png

SPL COMMON.JPG
 
The single most important factor for matching speakers(load) to amplifier(source) is impedance.

Speakers that present low impedance or very reactive loads will always perform best with amplifiers having very low output impedance. think class A space heaters like Levinson, Rowland, Krell etc

High impedance speakers which are usually also well mechanically/acoustically damped will generally perform best with amplifiers having a high output impedance, these will usually be transformer coupled amplifiers. Think tube amps, classic autoformer coupled Mac SS amps, etc..
 
In the great majority of cases, what you really need to concern yourself with is the speaker's impedance limitations and the impedance of the speakers themselves. When you have an amplifier that says it can handle a 4 ohm load, this means you can apply the amp to 1 pair of 4ohm speakers or two pair of 8ohm speaker. Math is different in relation to impedance. 4 + 4 ohm = 2ohms not eight. 8 + 8 = 4ohm. The lower the final impedance is, the more strain it will put on your amp. An amp designed to function with an 8ohm load will run itself to death on a 4ohm load.

I compare this situation to running a motor in a car with its drive wheels off the ground. It would be so easy to over rev the motor because there is nothing to limit its power. This is what happens to your amp with a low load impedance. It will literally run itself to death because it does not have a load that restrains the amp's processes.
 
Consult the manual, or the back panel, of your amplifier. If it has A and B outputs, it should give requirements for the minimum impedance of each set of speakers in order to play them together. If the amp can handle a 4 ohm load, it may be internally wired to run the two pairs in parallel, which gives a nominal 4 ohm load. If the amp can't handle 4 ohms, it may say not to play them together unless they are each higher than 8 ohms (for example, 16 ohm speakers in parallel would work). OR it will put them in series.

So follow the instructions, AND: always listen to your speakers for distortion. If you have two pairs playing loud and you start to hear distortion, turn down the volume. Also monitor the amp for excessive heat. If it gets too hot to touch after playing for a few minutes, that is also a sign of stress. Avoid cranking up the bass or turning on the loudness control.

Many amps will handle 2 pairs of 8 ohm speakers just fine at low to moderate levels. Even some that do not recommend doing it. It's all about which particular speakers, the music, and the volume.
 
Alberto86 said:
Hello all,

As I have to upgrade the ampli I would like 1st to understand what watts range ampli I have to look for and 2nd have some advices about good vintage or new ampli that can fit my situation.

Thanks for your replies in advance.

AB
Click to expand...

Alberto, both of your speaker systems are efficient so your current amp will handle the pair with ease.

The problem you have is the Fortes are significantly more efficient (99 vs 93) than the 2.1's. This means that if you power both sets of speakers at the same time with a single amp, the Fortes will dominate the 2.1's by a lot.

Since these two systems are so far apart in sensitivity, you should really consider powering each set with its own amp. Now, this makes for complexity as getting the same signal to each set in phase can be a challenge. Purchasing a pair of identical amps would make life much easier.

One other solution is the Sherwood RX-5502. This receiver has 4 full range amps rated at 100 wpc @ 4 ohms in a single box. The RX-5502 is still shown on the Sherwood USA website, but are increasing difficult to find.

I got mine from these folks, but they don't have in stock and are expecting a shipment:

http://www.mcmelectronics.com/product/50-4640

Hope this helps...
Regards,
Jerry
 
Thank you very much everybody for your comments!!!

Jerry,
I currently have 2 pair of connections on my receiver and I can choose to use speakers A or B or both together. In this case the 2 speaker of right channel would share the same amp and the left another amp together right?

Thanks in advance.
AB
 
Alberto86 said:
Thank you very much everybody for your comments!!!

Jerry,
I currently have 2 pair of connections on my receiver and I can choose to use speakers A or B or both together. In this case the 2 speaker of right channel would share the same amp and the left another amp together right?

Thanks in advance.
AB
Click to expand...

Alberto, sometimes we get confused by the language/jargon we use. Inside your da-r17 receiver, you have two power amps: one power amplifier for the right channel and another power amplifier for the left channel. This is commonly referred to as a "stereo" amplifier.

When you select speaker A + B, this selector switch puts the speakers connected to A and the speakers connected to B in parallel on the right channel as well as the left channel. It would be exactly the same as connecting both sets of speakers to the speaker A terminals (except that you could not de-select one or the other set).

My point is both sets of speakers see exactly the same voltage. Therefore, the more efficient speaker system will seriously dominate the less efficient system and there is no way to balance the two. When each speaker system has its own stereo amplifier (with volume and tone controls), then you have a very good chance to bring everything into balance.

Hope this helps, Alberto ...
Regards,
Jerry
 
Last edited:
You pretty much have been delt good advice by the members As for what brand amp that could (again) start a fire storm of opinion. For myself I like the sound from my AA-1800 amp and matching AP -4300 preamp, Those are not cheap. The "G" series of Sansui are very nice receivers has loads of features and are rugged also with very good sound. NAD makes excellent receivers with fantastic "headroom built in. Their "little" 40 watts per channel will simply amaze you with it attack and clean uncluttered sound- a very good purchase especially if one have been recapped.

If I were to purchase another amp I would lean towards the ones with +2~3dB of head room . If your amp runs out of steam on fast, high reaching attacks, then find something that will not quit you!
DC
 
Last edited:
I don't know where you found the chart. The part about exposure vs time is correct according to OSHA. But the examples are way off. Discos run about 110 to 125 db at 1 meter C weighted. Spoken voice is about 75 db at 2 ft which would be about 71 db at 1 meter. The threshold of discomfort depends on the source. If its white noise its a lot sooner, pink noise before 110 db, and depending on music selection in the 90's. So I would look else where for more examples that are a consenous for given levels.
 
Really clear.

Thanks a lot Jerry!

AB

onplane said:
Alberto, sometimes we get confused by the language/jargon we use. Inside your da-r17 receiver, you have two power amps: one power amplifier for the right channel and another power amplifier for the left channel. This is commonly referred to as a "stereo" amplifier.

When you select speaker A + B, this selector switch puts the speakers connected to A and the speakers connected to B in parallel on the right channel as well as the left channel. It would be exactly the same as connecting both sets of speakers to the speaker A terminals (except that you could not de-select one or the other set).

My point is both sets of speakers see exactly the same voltage. Therefore, the more efficient speaker system will seriously dominate the less efficient system and there is no way to balance the two. When each speaker system has its own stereo amplifier (with volume and tone controls), then you have a very good chance to bring everything into balance.

Hope this helps, Alberto ...
Regards,
Jerry
Click to expand...
 
You must log in or register to reply here.

Similar threads

Alberto86
Huge hum problem
Replies
19
Views
730
Alberto86
Alberto86
Alberto86
Sw connection to vintage stereo receiver
Replies
10
Views
406
onplane
onplane
cicada
Sansui MA-7 manual and picts
Replies
19
Views
3K
Reidy12
Reidy12
patslice
I Need Some Advice!
Replies
19
Views
1K
patslice
patslice
W
Klipsch Forte II speakers Question
Replies
2
Views
659
soop
S
Back
Top Bottom