What are the specs of a full range speaker?

Dave help me out with this: "Thor, The tranmission line (dual 7 inch) produces 4db of bass lift from 20hz to 110hz, with loss less than 1db of ripple....the -3db point is 45hz with roll off of 12db per octave below 45hz. ....Usable in room bass response extends well into the low 30hz range".
They lost me. I see 20hz, 45hz, and low 30hz. Which hz is this speaker producing?

Bartokfan

The measurement is from the "Thor"...-3db at 45hz would mean bass output (SPL) has dropped by around half at that freq. Most speaker systems are rated at their -3db points although how and where the measurements are taken is often not clearly stated.

The 12db figure...bass will be down in level by 12db at the next octave lower...a lot

Usable in room response means...some amount of sound that they deem "usable" will be output at those freq's. By saying in room, I guess they are saying that you will get some amount of bass help from the room....Maybe not in your huge room?

Dave

Dave, from your explantion + the link I looked at earlier today, I finally get the idea of db level.
"with rolloff of 12db per octave BELOW 45hz" That is not much going on in the 45hz range when the amp is at lower volume, which is how I listen.
I think the "inroom usable bass" has something to do with the open baffel in the back, has a interesting baffel system, and so in a large room there will be less, smaller more. As you explain.
Thanks.

Dave...

In your response to Bartokfan

>>>...-3db at 45hz would mean bass output (SPL) has dropped by around half at that freq<<<

Is there anyway to tell at what frequency the speakers output is flat?

I have to agree with Mdhoover and some others who are arguing against the "greater frequency reposnse is necessarily better" viewpoint.

Quality reproduction in the 80 to to 12Khz range is more desirable than a speaker that is "flat" from 20 to 20 Khz but suffers from significantly more harmonic and IMD distortion.

Furthermore, an SPL meter and a test CD will give practically everyone who owns a speaker with a flat reponse from 20 to 20 KHZ a surprise....as most rooms have between 10 and 20 DB response fluctuations (peak to trough) below 80 HZ. This is unavoidable and is caused by standing waves....room treatments can help some but fundamentally some fairly big bumps will remain unless they are equalized out, and then, even equalized, the reverberation problem remains and any EQ'd flat response is limited to a small sweet spot.

A further problem of a speaker with flat extended LF response (no roll off) is that LF frequencies radiate in ALL directions...therefore they reflect off the rear wall and will boost by +6db at some frequencies and will cancel out a quarter wavelength from the wall (producing more frequency response bumps in addition to room modes)

Which all goes to show that flat frequency response down to 20 Hz may not necessarly be a good thing in a speaker.