General question about Speakers, Watts, and A/V Receivers.

Jimbob -

Welcome to Club Polk. I can't answer your question regarding the clipping at what db, but I have some info. First - I would bet big money that the Onkyo Receiver is NOT 100 wpc with all channels driven. More than likely, it is well below that, which would change your calculations. It's always my suggest (Because I started like you did, with the 600 line of Onkyo) to buy a receiver with pre-outs so you can add amplification later if you want to really power your speakers.

Best of luck, and again, welcome.

James

Keep an eye out here as well Jimbob, deals on good AMPS can be found. Welcome to CP.

David

jimbobwey -

I'm just a step or so ahead in putting a system together. I took the advicee of the more experienced here and aquired an Onkyo AVR, their 707 model. It has all the functions you need for an HT and preouts for boosting power thru a power amp (just added).

Buying an AVR with preouts was the correct decision for me. I'm set up as a 5.2 becasue I biwired the front speakers using two speaker outs from the Onkyo. It will remain a 5.2 when the new amp is installed.

I see the 707s are deeply discounted now as Onkyo and others hurry to add 3D to their models. Hope this helped a little.

Dave

Also keep in mind that the sensitivity of a speaker is measured at 1Meter.

You will loose db the further you sit away.

Free space loss is -6db for every doubling of the distance.

So from 1m to 2m to 4m (~12ft) away you would experience a -12db loss in spl (free space loss).

You may not experience the full loss because of room acoustics/reflections, etc, but even so there is some loss that needs to be refactored into your power calculations for desired spl at your listening spot and corresponding power.

Wasn't the 'benchmark' of loudness a Who concert at something like 110db? :eek:

I would think that the average spl would be considerably lower -but where power gets gobbled up is in transient peaks where there could be sonic 'bursts' x2 relative loudness and so require x10 the power.

I think that is where amp headroom is the saving grace against nasty dangerous clipping

Erik Tracy wrote: »

So taking your example.

Let's say that at 12ft away, instead of a full -12db loss, you only loose 6db due to room acoutics.

If you want to be loud at 97db at your listening spot - you would need to be at 103db at 1meter (down 6db) and your power is at 16 watts - for average spl.

Now say a transient peak comes along in your listening at x2 loudness requiring x10 power. The amp would have to be able to deliver 160watts for that peak - else it will clip.

You are probably pretty close (you would gain 6db since you have 2 speakers playing and lose 12 db due to distance, so about 6db down is probably pretty accurate.) Using the chart he provided for 1 meter...

91db 1 watt
94db 2watt
97db 4 watt
100db 8 watt
103db 16 watt
106db 32 watt
109db 64 watt
---- (Clipping starts to occur?)
112db 128 watts
115db 256 watts

If you want to play at 110db at the listening position, it would be the same as playing at 85db at 1meter (therefore you would need 256 watts). As you correctly stated - if you had a 10db peak in the noise level (doubling the volume) - you would need 2500 watts to continue playing without clipping.

I think of amps like this:

If you want better sound quality and maybe a little better headroom, just in case - an amp will give it to you. It will provide better sound quality through much better control of the speaker cones and maybe a little more headroom for peaks, but not much more real volume (unless it is a REALLY powerful amp).

If you really want to mainly play louder - you should be looking at a more efficient speaker, not a larger amplifier. Some Cerwin-Vega and Klipsh speakers are over 100db efficient. The same senario listed above would put you at 110 db with only 32 watts of power and your AVR would still choke at the required watts to handle the 10db peak (320 watts) but a large amp may get you there.

Here is a comparison of the volume you would get with your 91db efficient speakers compared to some 101db efficient speakers (once again with a 6db loss considering speaker distance and multiple speakers playing)
[php]
Watts 91 - 6db 101 - 6db
1 85 95
2 88 98
4 91 101
8 94 104
16 97 107
32 100 110
64 103 113
128 106 116
256 109 119
512 112 122
1024 115 125
[/php]

As you can see - if you really want volume, it is alot easier to get it with speaker efficiency than amplifier power.

110 db's is not good for the ears,regardless if it's clean or has distortion. If the OP wants to play that loud for extended periods,get pro gear and make sure hearing loss is covered in your policy.