Jbl 2118h

[Niklas Nord]

Any thought about the 8" driver JBL 2118H ?

Is this a "horn" -driver ?

http://www.jblpro.com/pub/obsolete/2118.pdf

is it as good as the 2123?

[4313B]

"Any thought about the 8" driver JBL 2118H ?"

No

"is it as good as the 2123?"

No

[Niklas Nord]

what is it ment for?
what is it´s application use?

[4313B]

"what is it ment for?"
"what is it´s application use?"

Read the PDF found at the link you posted

Here are some systems it's been used in:

http://www.jblpro.com/pub/obsolete/4612ok.pdf

MR835:

http://www.jblpro.com/pub/obsolete/MR_Series.pdf

http://www.jblproservice.com/pdf/SR-Series/SR4735.pdf

http://www.goldsound.net/kit11.htm

[Robh3606]

The 2118 is also used in the larger Sythesis Systems too. I have a pair I am going to make rears with 2404's a 1/2 a 4612! Its a nice sounding driver. If you want a horn loadable JBL 8" go with the M209-8 used in the 3115. I have a pair of them from the tent also a nice sounding driver. You can buy them from JBL, look in the driver list. Mike B. had a pair of 3115 set up at the MAF and they were damn nice!

Rob

[Niklas Nord]

Ok, nice to hear from you!

Ahh, i do not know how to say this in english, is it
called "dispersion" ? how the sound is on axis and
not on axis

in swedish "spridning".

the 8" driver maybe has better "dispersion" than the 10" ?

[Robh3606]

Well the smaller the driver the better the dispersion as long as the driver is clean and not in break up modes depending on how high you plan to cross it over. It does well up to the 3k crossover in the 4612. You won't be going that high with it as a midrange??

Rob

[Niklas Nord]

no, higher than 2200hz would i not go

[locanti]

Never heard 2118H but I use a pair of D216 front loaded with 136A(4333awx enclosure) and ALTEC 806 in my system between 320Hz to 1200hz.You can't use these drivers up to 1500HZ/1800hz max.Hope that's help

[more10]

I am trying to figure out how to design horns. When doing a simulation yesterday, I discovered "mass rolloff", and further googling led to http://www.speakerplans.com/index.php?id=faq10. - for 12” drivers and smaller for use in horns a figure above 180 is good -

2118J, EPB is 213 and BL is 0.10. Too low BL.
M209-8, EPB is 190 and BL is 9.5. Ok according to speakerplans.

But "mass rolloff" is 2 x EPB. 380 Hz for M209-8. Can someone explain this?

[more10]

I am trying to figure out how to design horns. When doing a simulation yesterday, I discovered "mass rolloff", and further googling led to http://www.speakerplans.com/index.php?id=faq10. - for 12” drivers and smaller for use in horns a figure above 180 is good -

2118J, EPB is 213 and BL is 0.10. Too low BL.
M209-8, EPB is 190 and BL is 9.5. Ok according to speakerplans.

But "mass rolloff" is 2 x EPB. 380 Hz for M209-8. Can someone explain this?

2118J, EPB is 213 and BL is 15 (corrected). This driver should be "better" than M209-8 for horn loading, but mass rolloff is at 426 Hz. This is too low. Non of these drivers will reach 1 kHz in a horn, or is there something I have misunderstood?

[pos]

When talking about motor strength, Re has to be considered toghether with BL.
BL alone means nothing

Consider the 2118J and 2118H for example.

2118H has a Re of 6.2 ohms and a BL of 11
2118J has a Re of 12 ohms and a BL of 15

These are similar in the frequency response and sensitivity because the BL^2/Re (motor strength) are similar, around 19

now with the Mms (0.017Kg) you can calculate the mass break point, in Hz :

BL^2 / (Re x Pi x Mms)

So for the 2118H it is :
11*11/(6.2*3.14*0.017) = 365Hz

and for the 2118J :
15*15/(12*3.14*0.017) = 351Hz

But that does not mean that the driver cannot be used above 360Hz when horn loaded.
It just means that, when loaded in a constant directivity horn, the response will fall by 6dB/oct starting at this frequency.

Most compression drivers have their mass break point around 3 or 4Khz, but can still be used up to 20Khz with some compensation (or with horns that beam...)

The Le parameter will also play a role in how high you can use your cone driver, as well as the phase plug you will be using (if any).
And then there is also the cone breakups to consider...

For example the 2250 used in in the 8" CMCD design has a break mass point of 741Hz (very high), and is used past 2khz in many current JBL designs (together with a phase plug)

[Robh3606]

Jbl used the M209-8 in a horn. They had some in the tent sale a few guys managed to get them

http://www.jblpro.com/pub/obsolete/venue/vs3115.pdf

http://www.jblproservice.com/pdf/Ven.../VS3115-WH.pdf

Rob

[more10]

So for the 2118H it is :
11*11/(6.2*3.14*0.017) = 365Hz

and for the 2118J :
15*15/(12*3.14*0.017) = 351Hz

But that does not mean that the driver cannot be used above 360Hz when horn loaded.
It just means that, when loaded in a constant directivity horn, the response will fall by 6dB/oct starting at this frequency.

Thank you very much pos. Very useful information. I guess I have some reading to do regarding phase plugs. I guess you cannot simulate them in hornresp. Is this the black magic of horn design? :-)

So I guess the 2118J is useable as a horn driver. Since I have a couple of them and no M209-8, I will start with a 2118.

I will build a conical horn to begin with. Just to learn.