JBL 2245 to JBL 2123 best crossover frequency?

[David Ketley]

Im having trouble finding the best crossover frequency for the 2245 to the 2123 any advice would be welcome.

Dave

[Robh3606]

How about 300Hz or so?? Rob:)

[David Ketley]

How about 300Hz or so?? Rob:)

Hi Rob my problem is I don't know how well the 2123 performs lower down, the graph I found was not clear at all and I know they straightened out the extremes.

Dave

[David Ketley]

Hi Rob my problem is I don't know how well the 2123 performs lower down, the graph I found was not clear at all and I know they straightened out the extremes.

Dave

Found http://www.audioheritage.org/vbulletin/showthread.php?29162-Is-my-2123-h-out-of-specs

but there was no final conclusion if the 2123 would perform as well in the right enclosure.

[Doc Mark]

Morning, David,

Well, there are quite a few JBL lovers out there that seem very satisfied with the 2123 in it's small closed box, when used in systems like the 4345, etc.. Have you actually listened to your 2123 in a system? What do your ears tell you? Good luck, and God Bless!

Every Good Wish,
Doc

[David Ketley]

Morning, David,

Well, there are quite a few JBL lovers out there that seem very satisfied with the 2123 in it's small closed box, when used in systems like the 4345, etc.. Have you actually listened to your 2123 in a system? What do your ears tell you? Good luck, and God Bless!

Every Good Wish,
Doc

Im just at the design stage for the cabinets for the two 2245s and understand that if I want to get the 2245 up to 300hz then I need to design the cabinet accordingly with say a 10 cubic feet volume rather than a 12 ?
But if the 2123 will perform OK down to 200Hz then I think 12 cubic feet would be fine.

[Robh3606]

Go here for a more realistic measurement. I use mine is .5 cubic ft and they play to 300hz just fine. I cross them over to E-145's and they sound great once you dial them in. Rob:) http://www.audioheritage.org/vbulletin/showthread.php?29742-2123

[pos]

It has been my experience that the 2245H will have no problem to reach 300Hz, and that the 2123H will have no problem either to reach that frequency or lower.

Let me give you three pieces of advice though:

- You should use whatever EQ and electrical slope is needed on the 2123 to get a proper summation with the 2245H, ie for example a symmetrical acoustical LR 24dB/oct crossover. Typically the closed box already provides a natural 12dB/oct high pass filter, the smaller the box the higher the fc and Q. If you use a small enough box you might only need a single 12dB/oct electrical high pass filter with a low Q to get an acoustical LR 24dB/oct high pass filter. The low pass on the 2245H will be much easier to deal with, and a simple electrical LR 24dB/oct low pass filter will result in almost the same acoustical filter. Measurement gears would help (close mic measurement is easy), but some simple simulation might do the trick.

- use a mid box with a large enough baffle: you do not want the baffle step to occur around your crossover point. If you use the same baffle for the 2245H and 2123H you should be OK in this regard.

- You should get the 2245H sufficiently off the floor to avoid bloating the low mids. In my own system I was using a pair of 4645 cabinets with 2245H drivers up to 300Hz. I had each cab laying on its side with the 2123H and horn on top of it. The horn was at hear level, but the 2245H was too close to the floor and this resulted in a big and broad boost in the 150Hz area. This could be EQed but this was never satisfying as the problem was position dependent. I then put the cabs vertical and upside down, with the 2245 the furthest off the floor, and the problem went away.
Of course this brings the horn on a much higher position, so you might have to put the horn between the mid and woofer, like in this system (not mine :D):

http://www.behringer-electric.de/images/lautsprecher/referenzen/BLS Horn Heimkino/SS101200.jpeg

[David Ketley]

It has been my experience that the 2245H will have no problem to reach 300Hz, and that the 2123H will have no problem either to reach that frequency or lower.

Two pieces of advice though:

- You should use whatever EQ and electrical slope is needed on the 2123 to get a proper summation with the 2245H. Typically the box already provide a 12dB/oct high pass filter, and the smaller the box the higher in frequency and the higher the Q. If you use a small enough box you migh only need a single 12dB/oct electrical high pass filter with a low Q to get an acoustical LR 24dB/oct high pass filter. The low pass on the 2245H will be much easier to deal with, and a simple electrical LR 24dB/oct low pass filter will result in almost the same acoustical filter.

- You should get the 2245H sufficiently off the floor to avoid bloating the low mids. In my own system I was using a pair of 4645 cabinets with 2245H drivers up to 300Hz. I had each cab laying on its side with the 2123H and horn on top of it. The horn was at hear level, but the 2245H was too close to the floor and this resulted in a big and broad boost in the 150Hz area. This could be EQed but this was never satisfying as the problem was position dependent. I then put the cabs vertical and upside down, with the 2245 the furthest off the floor, and the problem went away.
Of course this brings the horn on a much higher position, so you might have to put the horn between the mid and woofer, like in this system (not mine :D): http://www.behringer-electric.de/images/lautsprecher/referenzen/BLS Horn Heimkino/SS101200.jpeg
Thats good the consensus seems to think that 300Hz is right.
Im keeping the cabinet long and low 22" so I can get the 2123 tight in but its easy to put large section timber at each end to raise it to almost any level, I think its quite room dependant?

[richluvsound]

Sure looks like Guido's work :)

[David Ketley]

Sure looks like Guido's work :)

Stunning speakers just the screens to small.
Dave

[pos]

The horns are indeed Guido's work, and he also aquaplassed the 2435 (these were mine), but everything else is Johann's work.

The mains are 2245H+TM1201+2435 on H9800 clones
The center is a pair of 2012H and a 2431 on H9800 clone.

[stephane RAME]

Good job.

Stéphane

[frank23]

I cross my E145>2123 at about 125Hz using a modded M553 active crossover. This probably a bit too low for the 2123 specs, but this way I get the preferred sound in my room. Crossing over at 200Hz or so gives me too much boom from the E145. The E145 centers are about 48cm from the floor. I should experiment with placing the E145 differently and get the crossover to 200Hz or so.

I think 300Hz may be a bit too high for the 2245, the lower the better, I would go to 200Hz, I think the 2123 can do that easily using a 4th order active crossover.