Question on Speaker Sensitivity

fraggle79

Folks,
I currently have a Rotel 931 amp and a pair of Mission 731's and am looking to upgrade. What would be the best amp and speakers?
Also I like to listen to music loud and how do match an amp to a speaker i.e how do you know if the amp can power them properly

cnocbui

You don't really want to know which are the best amp and speakers, as most people can not afford them.

It all depends on your budget.

If you like your music loud, then keep a close eye on the efficiency of speakers you are looking at, because it can save you money on the amplifier if your budget is tight. A more efficient speaker will require less power to achieve a given volume level than a less efficient one.

You need to know some stuff about audio jargon and the science behind 'loudness' to make sense of speaker and amp specs.

Loudness is usually measured in decibels (db). You need to double the power you are feeding to speakers to increase the volume level by 3 db, but this will not double the loudness your ears/brain perceive, it will only sound 50% louder. For speakers to sound twice as loud, you need to increase the volume by 6 db.

Therefore, to double the loudness you get from a set of speakers, you need to quadruple the amount of power (usually watts) you are delivering to them.

Speaker efficiency is usually given as the number of decibles you get, measured from 1m away, for 1 watt of power.

So if the efficiency of a pair of speakers is say, 86 db, you will get that amount of volume for only one watt of power. If you want the speakers to sound twice as loud, you are talking about a volume level of 92 db (86+6), but you will need four times the power to achieve it - 1x2 = 2; 2x2=4. So you will need 4 watts.

So if you are shopping for speakers and brand A is 92 db efficient and brand B is 86 db, you will need an amp that is 4 times as powerful to drive brand B speakers to the same volume level as brand A.

92 db is pretty loud, but you have to remember that you probably wont be sitting just 1m away from the speakers. The volume level will decrease with distance due to the inverse-square law (if you were out in the open), which I am not going to go into http://en.wikipedia.org/wiki/Inverse-square_law Since you will likely be inside a room, the decrease with distance is nothing like as bad and depends on how big the room is and whether it has sound absorbing features like carpets, sofas, curtains etc.

I have been talking about volume levels as if they were fixed, but music is dynamic. If you are sitting on the sofa and the average volume level is 80 db and along comes a sudden loud bit in the music that ought to be 116 db from where you are sitting, how much power would you need to achieve it?

Well if you needed 1 watt to achieve the 80 db, you would need 2048 watts to give you that 116 db transient. 116 db is pretty loud, but a loud hand clap can be 120 db close to your ear.

Find the speakers that you want, then work out how much power you will need, or can afford, to drive them.

**************
# 100 decibels, equivalent to a chain saw, pneumatic drill, printing plant, jackhammer, speeding express train, some car horns at five meters, farm tractor, riveting machine, some noisy subways [about 20 feet].
# 90 decibels, equivalent to a police whistle, heavy traffic, truck traffic, noisy home appliances subway-rail train, pneumatic drill [or hammer] at one meter, walk-man ear phone [average volume], rock drill at 100 feet, some motorcycles at 25 feet, shouted conversation.
# 80 decibels, equivalent to heavy city traffic [25-50 feet], alarm clock at two feet, factory noise, vacuum cleaner, heavy truck, loud-radio music, garbage disposal.

"A single, explosive noise is capable of damaging hair cells, but hearing loss is usually the result of continual exposure to volumes over 80-85 decibels."
—Harvard Medical School Health Letter, (Vol. II, No. 8, 1986), pp. 1-4.

Idleater

fraggle79 wrote: »

Folks,
I currently have a Rotel 931 amp and a pair of Mission 731's

Any particular reason you want to upgrade? Can you identify where the weakness are?

I'm running some of both the Rotel 10 and 15 series amps and I can recommend them. Rotel tend to work well with B&W so you can possibly try out a couple of sets of those with your 931 which by all accounts is not a bad amp.

You will get a bigger sound out of bigger speakers too, but big sound does not necessarily equate to detailed sound. More into quality than quantity myself.

fraggle79

Excellent posts Guys!!!

I was thinking of upgrading the Rotel Integrated AMP to the RA-04 and a Marantz CD 5001 CD Player and perhaps a set of B&W's. I have approx €600. What are your thoughts?? They seem to get five stars in What HiFi.

Cheers

cnocbui

If you already have a CD player that works, don't buy another, it won't sound any better.

You already have a 35wpch amp, is that right? The intended replacement is 40 wpch?

Don't bother.

The RA-04 won't 'sound' any better and will not sound any louder! You would only get about a 0.42 db increase in volume. You couldn't hear that small a volume gain.

Spend all the money on the best pair of B&Ws it will buy, that will probably give you your best chance of an improvement.

To 'meaningfully' upgrade from your present amp, aim for 140/150 wpch.