planning to use 18" bass in OB to help LF

[c3conv]

I have a pair of Goodmans Axiom 15" in OB. It so happened I found a pair of 18" bass driver with 106db, resonance frequency of 28 +_ 3db, frequency response of 28Hz to 5000Hz printed on the back. I read from somewhere that in OB the bass should be at least 6 db more sensitive than the main driver. Are these all to consider? what about the baffle size? what about putting the main and the 18 together in one open baffle as I have seen in some designs?

[Cal Weldon]

Do you have any idea of the driver Q? Try and have that above .7

[c3conv]

Thanks Cal but I don't know what the Qs are and how do I get to measure them as I am not yet so familiar with them? Won't the sensitivity be enough? What does the Q do?

[tinitus]

Pictures might tell something

[Cal Weldon]

The higher the q the "bassier" they will seem and the more suited they are to OB. Tinitus is right, a few pics including the back would be helpful. Usually small magnets mean a higher q.

[Pano]

Originally Posted by c3conv;

bass driver with 106db,

106dB/Watt? Never seen a cone driver do that. What the heck is it?
Or did you mean something else?

[CLS]

About the Q, I got an interesting observation.

I have 2 types of papar cone fullragners, both are the same size - 8". Bought from a local audio shop, so they are not widely available, let's just call them MkI and MkII.

MkI is semi-shielded by a second magnet glued on the back, 1" VC, paper cone with a paper whizzer, fabric surround. Qts=0.5

MkII has single magnet but obviously bigger, larger VC (maybe 1.5"), also paper cone with paper whizzer, and fabric surround. Qts=0.35

(The numbers are not precise but close enough and good enough for discussion. And it's for sure that the Q of MkII is obviously lower.)

I have only used them on OB and it turned out quite the opposite of my expectation: the lower-Q MkII delivers quite a lot of bass than high-Q MkI. (all others being equal, of course) Examined again and again, it's a fact either by ears or by test mic. Lower-Q MkII give deeper bigger bass for sure.

Their parameters were measured by WT3, which I've been using frequently and found it very consistent.

Other than the T/S parameters, physically, the two drviers are quite different in their cones and suspensions.

The high-Q MkI has a thicker and harder cone with a stiffer suspension.

Lower-Q MkII has a thinner softer cone with a softer suspension.

Forgot to mention, MkII has a slightly lower fs, by a few Hz.

Their sounds are totally 2 different characters: higher-Q MkI is uptilted, bright, light; while lower-Q MkII is downtilted, warm, darker with slightly higher overal sensitivity.

How so? I haven't figured it out yet. Or maybe it's because Q tells us little about the sound in the first place.

[c3conv]

Originally Posted by panomaniac

106dB/Watt? Never seen a cone driver do that. What the heck is it?
Or did you mean something else?

I don't have my laptop with me right now I will post it as soon as possible. Thanks

[c3conv]

Originally Posted by CLS

About the Q, I got an interesting observation.

I have 2 types of papar cone fullragners, both are the same size - 8". Bought from a local audio shop, so they are not widely available, let's just call them MkI and MkII.

MkI is semi-shielded by a second magnet glued on the back, 1" VC, paper cone with a paper whizzer, fabric surround. Qts=0.5

MkII has single magnet but obviously bigger, larger VC (maybe 1.5"), also paper cone with paper whizzer, and fabric surround. Qts=0.35

(The numbers are not precise but close enough and good enough for discussion. And it's for sure that the Q of MkII is obviously lower.)

I have only used them on OB and it turned out quite the opposite of my expectation: the lower-Q MkII delivers quite a lot of bass than high-Q MkI. (all others being equal, of course) Examined again and again, it's a fact either by ears or by test mic. Lower-Q MkII give deeper bigger bass for sure.

Their parameters were measured by WT3, which I've been using frequently and found it very consistent.

Other than the T/S parameters, physically, the two drviers are quite different in their cones and suspensions.

The high-Q MkI has a thicker and harder cone with a stiffer suspension.

Lower-Q MkII has a thinner softer cone with a softer suspension.

Forgot to mention, MkII has a slightly lower fs, by a few Hz.

Their sounds are totally 2 different characters: higher-Q MkI is uptilted, bright, light; while lower-Q MkII is downtilted, warm, darker with slightly higher overal sensitivity.

How so? I haven't figured it out yet. Or maybe it's because Q tells us little about the sound in the first place.

I notice that there are a lot of drivers now for sale in our country that the specs were not all available and nobody minded what the specs are as long as they have the sensitivity, power and ohms. It just so happen for me to see these and I presume they were in the display shelves for some time now.

[c3conv]

Here are the pics.
i


Sorry the pics are too big. How do I get to do it to make it small?