Sensitivy advice...

[JerMu]

Newbie here so please excuse my ignorance...

I've been doing some research the past few years on speakers, trying to prepare myself for designing/building some projects and while I know more now than I did when I started I sometimes feel like the new knowledge is confusing me more. At any rate I think some good old fashion real life experience is what I need to help put some of this book knowledge in perspective.

My question is about speaker/system sensitivity. I'm planning on designing a speaker system which will include two front loudspeakers, with a center channel, sub, and rear speakers (basically a theater system with the loudspeakers doubling up as stereo speakers when I am not listening to 5.1/7.1). The obyss of speakers out there makes it hard to know which way to go, and I'm trying to find some good DIY projects that have already been done so I can mimic at first rather than jump in too deep of water, but still I find that one persons speakers/system response charts live in the 80-85 db/w/m while others are 90-95 range and I'm left wondering what isn't enough, what is, and what is over kill? I assume room size helps to answer this question, but so far I am totally clueless on how all this equate to a final result that I like or don't like and while I assume it is a bit subjective with each person there has to be some guidelines, right?

-Jman

[MaVo]

The more power you send into a speaker the more distortion there will be, so using a high sens speaker with small watt input will generally have lower distortion compared to a low sens speaker and lots of watts. but the overall design will also play into this equation. so this is a rather rough generalisation.

since most speakers will be able to achieve a satisfying spl in room (except maybe for the peoples with rather extreme taste) it becomes a question of how much distortion you would like to have. spl at 1 watt at 1 meter wont tell you this. i think you should read more in this forum to be able to recognice a good speaker by its design and to avoid falling into the many traps which are out there and cost alot of money.

[R-Carpenter]

I disagree with straight analogy between distortion and sensitivity. Seas and Scan Speak drivers aren’t known for their high sensitivity but for low distortion and high resolution.

The basic idea is this: lower the sensitivity of the speaker, more wattage you have to pump in to achieve same SPL (sound pressure level=loudness). Higher sensitivity speaker will need less powerful amplifier to be just as loud. It doesn’t mean that higher sensitivity speakers are better.

[JerMu]

I understand what sensitivity is what I don't know is what is a good application of the numbers. I'm looking for a good guide line to base my first design on. I don't want to design a system only to find out it doesn't fill the space with adequate sound. I need a good guage to start with. As I said in my earlier post I know this is probably somewhat subjective, but I am just looking for a good place to start that I will probably be okay with and then I can tweak my future designs off my tastes compared to this one. I also understand that a lower sensitivity means you need to pump more power into the speaker to get the same result as the more effiecent speaker, but you can/will run into power limits so you want an efficient system(imho). I just need to know what a good benchmark to start with is and at what point are you paying for something you really don't need. Does this make sense?

Thanks for the replies so far...

[jupiterjune]

I disagree with straight analogy between distortion and sensitivity. Seas and Scan Speak drivers aren’t known for their high sensitivity but for low distortion and high resolution.

Perhaps he was referring to the an amplifier effect, not a speaker characteristic?

At any rate -- 90 dB at 2.83V/m is (IMHO) perfect.

Those in the 82-86 range are usually small 2-way bookshelf speakers, with a largish inductor (1.5 to 2 mH) in front of the woofer to increase bass extension. They will require a lot of amp. to drive LOUD.

It is a rare 2-way that has 90 dB at 2.83V/ meter. If you do find one, it may have low impedence, or a really large box, or limited bass extension. None of which is particularly bad, especially for home theater. But you will want to know this ahead of time, and be sure your equipment can handle all the requirements needed to achieve flat, full range response.

Typically, you will find 3-ways in the 90 dB range. Much as I love the idea and simplicity of a 2-way, I greatly prefer 3-ways for many, many, reasons.

Once you get up to 93 dB at 2.83V/meter, you have a speaker that is so sensitive that you start to hear the ground and PS noise through it. You may need a really quiet pre-amp and amp.

Just my humble opinion! Hope this helps.

JJ

[Brett]

100dB is where I aim. Anything less than that sounds dynamically compressed to me.

[BHTX]

Originally posted by Brett
100dB is where I aim. Anything less than that sounds dynamically compressed to me.

..lol.

[JerMu]

Thanks Jupiterjune that is exactly the kind of advice I'm looking for, any other opinions or is this some what right on the money?

[ttan98]

Originally posted by Brett
100dB is where I aim. Anything less than that sounds dynamically compressed to me.

The range of drivers you are looking for would be fairly limited, there are not that many to choose from...

[Brett]

Originally posted by ttan98
The range of drivers you are looking for would be fairly limited, there are not that many to choose from...

There are plenty, and I don't mind using multiples to get the sensitivity up in the low end. Above 300Hz, there are quite a few that are 100dB. Again use multiples or horns/waveguides as neccessary.