2123H response

[faulken]

Hello

I got three 2123H. I seek the response curve of the 2123. I have the documentation pdf of the 2123. But the response curve above is not very clear.
And I do not believe at all afterwards of multiple test in the output of 101 db announced. I saw that jbl had made a small enclosure of wiring for sound with the 2123 for bass middle.

This enclosure is announced for 93 dB. And I believe much more in this result. When think ?

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Faulken

[Robh3606]

Hello fauken

I use 2123's from 300h to about 1.2K they are in a small midrange box. I have E145-8 under them and they are more sensitive than they are. 145 are rated at 98db. The were also more sensitive than my 2122's. Had to rebalance after the switch. Don't know why the sensitivity is low on yours?? They are not as smooth as that response graph shows but they are pretty flat.

Rob

[faulken]

Hello Robh3606,

what is your configuration to use the 2123h ? Closed box ? Reflex box ? liter ?

is what it is for you best the 10" from jbl? Which type of filtering use? I have one 2426. Is what the 2123 would go well with?


Thanks

Faulken

[Robh3606]

I am using them closed box about 7.7 liters accounting for driver displacement. I am using active filters with 24db L/R slopes M552/M553 crossovers. I like the clarity and transient response. I use a 2416 compression driver with a 2344A horn. Which horns do you have for your 2426??

Rob

[nowater]

I think the 2012H response would be very similar and there is a 2012H plot in the JBLpro appnote http://www.jblpro.com/pub/technote/tn_v1n24.pdf
Fig. 2 shows output including distortion (very nice)

Hope this helps (belatedly)

[faulken]

Hello

Here the response curve. I mesure myself.
We are far from the Jbl's flat reponse.

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Faulken

[GordonW]

Well, in the region JBL commonly uses them in (200-1200 Hz), they're REMARKABLY linear. Yes, there's an upward-tilt to the curve... but that's a known quantity, and relatively easily dealt with.

BTW: What enclosure was the 2123 in when measured? I'd be interested to see you do another measurement, with the 2123 in about a .25 or .3 cubic foot (7 to 9.5 liters) enclosure, sealed. Oughtta bring up the bottom end (200 hz region) a bit to meet better, the 1KHz region...

Regards,
Gordon.

[Zilch]

JBL's published response is not flat....

[faulken]

I make new measure. I post it.
It's better now.

I'm not happy between Jbl, because on a pdf datasheet, we can see a flat response. I think it's a simulation oh the response.... not a realy measure.
Now I think it's a very good speaker but very difficult to use.
On the picture :

in green, 2123 non filter,
purple 2123 passive filter 18 db to high
yellow 2123 passive filter 18db better for me

I adjust the filter to have the more falt response with my 2426.
I don't understand why when I filter the speaker the area 150 250 hz increase of 3 db !!???

Sorry I can't make other measure. I got only 14 liters closed box.
Another think I don't say. I measure in axis at 50 cm (20").

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Faulken

[frank23]

I once found these on the internet.

[Robh3606]

Don't get too hung up on how they measure. I was dissapointed too when I first got mine thinking they would fix a peak in my 2122's only to find they had it too but to a lesser degree. Once you set them up they sound great so at least for me all was forgiven. That sheet says +/- 2 dB of the attached curve from 200-5K.

Rob

[Ian Mackenzie]

Great reference information.

Ian

[GordonW]

I don't understand why when I filter the speaker the area 150 250 hz increase of 3 db !!???

Faulken

It's because of the DC resistance of the inductors in your low pass filter. The resistance (which the speaker sees as additional 'source resistance') raises the Q of the speaker, increasing the output on the bottom end.

Looks to me, like this combination of filter, driver and enclosure is working out for a pretty darn flat response. If you were going to use no passive filters (ie, an active crossover before the amp), I'd use a smaller enclosure... but with your passive lowpass filter, I'd run it with the box size as-is!!

I think the moral of the story is this: Sometimes, what seems like a design "flaw", actually is just a method of "counteracting" other "forces" that can potentally upset the response. In this case, the rising response of the driver and the "bottom end boost" of the Q increase due to the passive crossover, cancel each other out. Quite an effective system overall design, all things considered...

Regards,
Gordon.

[faulken]

I think to use 2123 at is maximum, it's a horn. I trie quickly to put two pice of wood on the left and the right of the speaker at 45 °. The response was beautiful, ultra flat.

When I trie to filter it, in 12 db I never got a god measure. I don't use low pass filter juste a high pass filter but I know it isn't good for it.

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Faulken

[Bill Shenefelt]

I noticed you say that the small enclosure brings up the bottom end of the 2123. I have 2121 H drivers in a box about 0.3 cu ft. I was going to increase the volume to closer to 0.6 cubic ft. Is this the wrong direction to go? I have the 2121H's as part of a home built 4343 monitor set. My front baffles are narrow and I was going to widen them to bring up the 200 to 600 region output as it is low now. Am I defeating the purpose of widening the baffle if I increase the box size? I know they are 2121 H not 2123 but had to ask before I start cutting and rebuilding. .
Bill Shenefelt
[email protected]

Well, in the region JBL commonly uses them in (200-1200 Hz), they're REMARKABLY linear. Yes, there's an upward-tilt to the curve... but that's a known quantity, and relatively easily dealt with.

BTW: What enclosure was the 2123 in when measured? I'd be interested to see you do another measurement, with the 2123 in about a .25 or .3 cubic foot (7 to 9.5 liters) enclosure, sealed. Oughtta bring up the bottom end (200 hz region) a bit to meet better, the 1KHz region...

Regards,
Gordon.