Driver efficiency

[JBLOG]

I have heard that both the D130 and 075 are very efficient. Does anyone have efficiency specs?

Thanks

[Robh3606]

You want the actual in percent or the SPL @ 1 watt?? The SPL's are on the driver spec sheets and the percentage you can get off the T/S data sheet for the woofers. 130A is a 2220

http://www.lansingheritage.org/html/...p/pro-comp.htm

Rob

[Thom]

Isn't the main difference in specs between the 130A and the D130 the measuring method. The 130A being measured as a woofer and the D130 not?
(If I'm wrong thats fine. You'll notice that it's a question.)

[JBLOG]

Hi Ron,
Thanks for the link.
I'm looking for sensitivity in terms of dB at a distance of 1 meter away being driven at by 1 watt. The specs of the 2220 are at 30 ft driven by 1mW.

Dave

[Thom]

I'm real foggy on this but I think you gain 3 db every time you halve the distance and I'm not sure what you gain going from milliwatt to watt but it's Less than you might think. It might be 10 db for 10x that would give you 9 db to get to one meter and 30 db to get to 1 watt. That would be about 91 db which doesn't sound right to me but they measured that warble instead of a solid tone so I don't know. My conversions may be totally wrong and maybe someone else can straighten it out.

[JBLOG]

I'm thinking (hoping) they're 98-99 dB.

The D130 driver as described in the following link..

"It was nonetheless a powerful magnetic structure that resulted in a new driver of unparalleled efficiency."

http://www.audioheritage.org/html/profiles/jbl/d130.htm

[Robh3606]

Do you have the D130 or a D130A?? The D130 has an aluminum dust cap and voice coil. The 130A has a copper voice coil and paper dust cap. Look here in this catalog. The SPL numbers are at 15 Ft. not 1 meter. The 130A is about 2 DB lower but you should be around 100-101Db

http://www.lansingheritage.org/image...comp/page8.jpg


Rob

[JBLOG]

BINGO! Thanks Rob!
That's exactly what I was looking for!
100dB!! That's crazy efficient!

I have the C38 with the extended D130 (shiney metal center) and the 075. What is the dB conversion formula to get from 15 ft to ~3.28ft (1m). I remember seeing it somewhere on the forum.

Thanks
Dave

[pocketchange]

If you need a 10/10 pair, let me know. These were in a set of Georgians
and were replaced with the proper 4 ohm 15" driver to get the system in line. Look and sound like they are new. pc

[Thom]

If I'm not mistaken that would give you 100 db at 3.25 feet If the D130 and the 130A were identical (I'm not saying that they are) they would have different stated efficiencies because the d130 is measured at 1Khz , and the 130A is measured with a low frequency tone warbled between two stated but not remembered frequencies. I'm almost certain that cutting the distance in half gives you 6 db. When I was selling them I couldn't tell the difference when used as a three way in a C34 or C40. In an 030 system there was a big difference because the 130A just wouldn't go as high.

I halved the distance twice. That would give you 3.25 feet. not exactly 1 meter but pretty close.

The D130 was listed at more than 100 db I believe. Though not much more.

[johnaec]

I'm almost certain that cutting the distance in half gives you 3 db.

Doubling power gives you 3dB, doubling distance is 6dB, (halving is -6).

John

[Thom]

Doubling power gives you 3dB, doubling distance is 6dB, (halving is -6).

John

If you are positive, I'll believe you. It's been a long time and I couldn't swear I wasn't wrong back then. There has to be experts (no disrespect if you are one) out there, where are they when you need them. Though for these purposes I believe you inverted halving and doubling. In this instance more is louder and it doesn't get louder as the distance increases.

There times when level is measured in db below a set point then + and - would be as you stated.

I found a site on the net that backs you up as to 6db for double the distance.

[johnaec]

Though for these purposes I believe you inverted halving and doubling.

'Sorry 'bout that - 'got my positive and negative's mixed up...

John

[Thom]

Thanks for correcting me on the distance formula. I don't know if or when I'll need it but, I really hate being wrong and without your correction I would have continued to carry the wrong formula in my head.

[Mr. Widget]

Thanks for correcting me on the distance formula. I don't know if or when I'll need it but, I really hate being wrong and without your correction I would have continued to carry the wrong formula in my head.

If you really want to be accurate, then you need to add into your equation that losing and gaining the 6dB per doubling or halving the distance only holds in a completely open space. In a typical room the sound drop or gain is significantly less since there are many reflections that tend to reinforce the sound.... though not equally at all frequencies.


Widget