Can Someone Explain Upper & Lower db Speaker Specs

[mufsoman]

The thread title says it all. Just looking for an explanation of what this speaker spec really is telling me and how does it relates (or maybe doesn't) to the other specs such as efficiency, power rating, etc. What is a good spec and not so good? Thanks

[TNRabbit]

Not certain what you are referring to about "upper & lower dB"....?

Efficiency is how many dB the speaker with output with 1 wat input, measured at 1 meter in front of the speaker. The higher this number, the more efficient the speaker. The more efficient are usually close to or above 100 dB. For instance, if a speaker has a 110 dB efficiency rating, it would get D@MN LOUD with single-digit # of watts, while an an 84 dB efficient speaker would require HUNDREDS of watts to reach the same output level.

Power ratings vary WILDLY from one manufacturer to another. If a speaker has a "continuous" rating of 100 watts and "MAX" rating of 250 watts, it means the speaker can dissipate heat without failing at a constant 100 watt input for an extended period but can only withstand 250 watts for a short (usually milliseconds) period. The importance of this spec depends on your listening levels & how much amp you have.

[RyanJoz]

If you are talking like 20-20000 Hz +/- 3 dB, then that number is the frequency response of that speaker. If the last number is +/- 1 dB then the volume of all frequencies in that range will be much closer to the desired level.

Example, say you are trying to play a frequency of 30 hz at 100 dB, and the specs say +/-3 dB. The speaker may play that freq at 97 dB, 103 dB, or anywhere in the middle.

This number will not at all give you an idea for how well you will like the sound. LSi speakers and RtiA speakers have very close ratings as far as freq. response, but sound totally different.

[DaveHCYJ]

I think mufsoman is reffering to the "Lower -3dB Limit" and "Upper -3dB Limit" listed in the spec sheets.

As RyanJoz explained some speakers have a spec that states somethign like 50-25000Hz +/- 3dB, which means every frequency in that range is no more than 3dB off of what it should be. However, outside that range the speaker isn't totally silent, its just off by more than 3dB.

For example the RTi A7 states a frequency responce of 20-27000Hz. And its Lower -3dB limit is 35Hz. What that means is, although the speaker can play sounds down to 20Hz, the sounds below 35Hz are off by at least 3dB. In other words below 35Hz the volume level starts to drop off. The same is true for the upper limit. The speaker can go up to 27kHz, but above 26kHz volume level drops off.

[kuntasensei]

Yeah, what they said. Also, keep in mind that these are typically anechoic specs, meaning that's how they perform in an anechoic chamber. Actual real-world extension at the low end will typically be a little lower than the spec. For instance, my RTi28s have a lower -3dB point of 59Hz, but in my room they actually get +/-3dB down to around 42Hz.

A speaker's lower -3dB point is a good guideline for where you should set your system's crossover for that channel. In the case of my RTi28, I use 80Hz, since that gives me a full octave for the transition from speaker to subwoofer. Generally, you can get away with a half-octave transition above the anechoic lower -3dB point, so multiply that number times 1.5 and you've got a good best-case crossover point for your AVR. Ideally, you want all channels to stay at 80Hz or lower. In fact, in most cases, 80Hz will be perfect for all channels, regardless. But if you swap off for 2-channel listening + sub, it's nice to have mains with a little lower extension.

Also remember that the more bass you take off of the speaker and let the sub handle, the less power you need in your AVR to drive that channel cleanly. A speaker might optimally need 150w to drive its full range, but with an 80Hz crossover in the AVR, it can typically never use more than 60w in an average setup. That's why a well-powered subwoofer is always recommended for home theater.

[not savvy]

I know this is a POLK site, but you guys seem to know what you're talking about, and these questions are pretty general, not to any specific brand. PLEASE HELP US! The new wife and I finally got a used 5.1 550 watt Sony STR-DE975 with 5 speakers that will carry the receiver. What I don't understand in this manual are 2 things.
I'm reading earlier posts about db settings, but I'm still not clear. Do the db correlate, in any way, as to the frequency you set that setting at? I'm not understanding how to choose the Hz,KHz and then how to set the db to go with that Hz setting. It's all over my head, and I need help understanding. What we read on the previous answers are over both of our heads. We're trying to understand, first, how to choose the correct frequency, since there is a range given. Then, how many decibels go with that frequency setting, or does it matter? Once we fiqure out where to put the frequency, then are the decibels chosen by the frequency, whatever sounds best, or by how far the speaker is from where we're sitting (as one friend suggested), or by how far the speaker is from the receiver (as another couple told us), or is it any of the above? We're young, and just learning.

Also, I had set my spekers to small, my LFE highcut to 80 (sub setting all the way up to 250, switch to LFE), then I read on and there's an LFE mix from -20 up to 0. There's, also, in Equalizing, the lowest bass setting for each speaker 99Hz. Do I need to set the LFE highcut to 100? What do I do with the LFE mix? I never heard of that before.

We are so anxious to learn, and get our first system set up, but this has her in tears, and me just stumped. Any help??

[mshan242700]

Crossover setting in receiver should be set based upon speakers you are using.

Based upon saying lowest frequency for satellites is 99 hz, I would choose 100 hz crossover for sub and satellites to start.

The LFE mix (-20 to 0 sound output level from the sub) can be adjusted by ear or using something like Radio Shack analog SPL meter.

You should probably try and set volume of receiver around area you normally listen during movies and do your calibrations there; maybe 65 or 75 db if you share walls with a neighbor.

Digital Video Essentials or Avia Guide to Home Theater calibration discs help, as do some Star Wars dvds and others that have something like THX optimizer in menu.

[not savvy]

Thank you for responding so quickly. It's not my rears that only go down to 99Hz. In EQUALIZER I'm asked to set the frequency and decibels for EACH speaker, and sub, treble, mid, and bass. That is where the lowest bass setting is 99Hz. Not rears, but fronts, center, and rears. And sub equalizing asks for frequency and decidels, too. That's all under EQUALIZING. There'a, also, SETUP, LEVEL, and Surround. If you'd care, the manual is here:

http://www.retrevo.com/support/Sony-.../387dj983/t/2/

It's for the 875 & 975. Ours is the 975.

On page 23 (SET UP) is where to set the XO for front, center, surround. Also, there, asks for setting for LFE high cut filter. I'm assuming that is like a low cut and I had all set to 80.

Under the LEVEL button ( page 37) it asks for the decibels of center surround and sub and LFE MIX. What does the LFE MIX do? I don't understand that mix. What is it mixing?

Okay, I've set the decibels in LEVEL. Then I go further and under EQUALIZING (page 38) it asks us to set the front gain (but it's decibels again, which I set in LEVELS) and frquency for front treble, mid, and bass, all 3 needing their own frequency and decibels. I, then, have to set center treble, mid, and bass frequencies and decibels. Same with surrounds-all 3 settings again. It's there, in EQUALIZING where the lowest bass that the receiver shows for fronts, center, and rears. I already set decibels in LEVEL.

Is there a correlation between where I set the decibels and the frequencies? There's such a broad range in frequency settings.

Am I making sense? Can you look at the manual and help? THANK YOU!!!!