# Speaker Efficiency

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.

#### cm961

Hi guys!

Given the efficiency of the speaker, (1W 1meter), and the max R.M.S power, is it possible to calculate the max SPL at 100W 1 meter?

Pete

#### schizeckinosy

Pete,

10 times the power gets you 10 more decibels, so since 100 watts is 10 x 10 x 1 watt, you should be +20 decibels.

This assumes perfect linearity, which you will not achieve, so your real world result will be less than this due to compression and losses. I don't know how much you could expect to lose, it would vary with the driver.

Cheers, Dan

#### MRehorst

If you want to know the max spl in a room with reflective walls the result will be quite different from the ideal case of infinite baffel in an anechoic space.

It will depend on the room dimensions, frequency, etc.

There is no easy way to arrive at a specific answer. I think there are some software simulation packages that can give you an answer to this sort of problem, assuming the room is simple enough.

MR

#### cm961

Thanks for the info guys!

Pete

#### Eric

Paid Member
SPLs of room interaction

Theoretically (which NEVER happens), each "close proximity" room boundary such as walls and floors will add 3dB to the sound level. This is why corner loading your subwoofer can add up to 9dB to response in the 20-40Hz region. However, reflections from walls and other objects will cause the sound wave to interact. The results of the interactions will nodes and antinodes, some will increase your SPL while others will decrease your SPls.

Have a look at the Room Mode Calculator and plug in your room dimensions. The basic idea is that you don't want the room modes (given in Hz) to be too close to one another. You want to seem them fairly evenly spread out rather than be "clumped" together.

If 1 watt at 1 meter = 90 dB, then
2 watts at 1 meter = 93 dB, and
4 watts at 1 meter = 96 dB... just keep adding 3 dB. The final results are, of course, subject to the limitations indicated above.

Hope this helps! Eric

#### AndrewJ

Yet again the myth of room boundaries adding 3dB appears!!
Every boundary actually increases low frequency sound pressure level by 6dB, easily verified by measurement and theory. Just look up in Acoustical Engineering by Olsen, amongst other classic textbooks.

Andrew

#### Eric

Paid Member
My mistake, I stand corrected.

#### AGGEMAM

Eric said:
My mistake, I stand corrected.

Not entirely, while it is correct that in theory, each boundaery add 6 db, that only works if the point of origin of the sound is an infininetely small point placed directly in/on those boundaeries.

The effect in RL measurements varies depending on frequency between a 0 db and 6 db increase.

#### AndrewJ

Eric, sorry to correct you so publicly. Re reading my post, I hope I didn't come over as rude, it was not my intention.
Aggemam, I did carefully qualify my statement by saying low frequencies, and boundary reinforcement is by definition reinforcement by a boundary, not a "near" boundary!
One has to be very careful on a forum such as this to make clear the conditions that apply to statements being made. They are open to misinterpretation due to either being inconcise when making statements, or being misinterpreted when read. At least it can lead to lively discussion!
Regards

Andrew

#### Eric

Paid Member
Andrew: not a problem, thanks for your message! Indeed, sometimes more can be learned through disagreement, especially on the part of the lurkers

#### AGGEMAM

AndrewJ said:
At least it can lead to lively discussion!

Which is not that bad a thing (new ideas rarely surfaces in an enviroment in which everyone agrees on everything).

Oh, yes, you did write low freq, sorry.

#### AndrewJ

(new ideas rarely surfaces in an enviroment in which everyone agrees on everything).

Unless they are my ideas....

Andrew

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.