4430 + 2123H : a way to improvement.

[screw_squirrel]

Good morning everybody,

I have bought a pair of 4430 2 years ago and played it with a single McIntosh MC2255 amplifier. One year after I upgraded the system by bi amplifying it with JBL6260 and MC2255. The result is like day and night, the system is much better. But… I have read that I could improve it by adding a medium speaker with no modifications on the basic speakers.
So I have found a pair of 2123H and I want to build the enclosure and buy the right crossover to achieve this project.
Knowing that I think use the 2123H from around 300Hz to 1000Hz, to make a good blend with the couple 2425H + 2344A

My questions are:

- What dimensions and volume for the enclosure with 2123H?
- Should the front side of the enclosure be like à square 30cmx30cm or can it be 55cm wide to fit the 4430 width dimension?
- Is the M553 crossover a good choice?
- Should I prefer a digital crossover with multi frequencies and slopes choice like dbx PAdriverack.?
- Can I run two active filter 5235 in serial with 300Hz and 1000Hz cards?

A lot of questions as you can see…
Can someone provide good advices to about it?
Thanks to anyone
Eric

[Robh3606]

Hello Eric

I ran an E-145, 2123, 2425 2344 combo using an M553 for a while. It was quite nice soundind. I now use a PTH1010 and a 2435 for the top end.

What dimensions and volume for the enclosure with 2123H?

I think it's .25 cubic ft but check the data sheet and Drew Daniels system on the site.

Should the front side of the enclosure be like à square 30cmx30cm or can it be 55cm wide to fit the 4430 width dimension?

I would match the 4430 width as far as the baffles concerned.

Is the M553 crossover a good choice?

Works for me.

Should I prefer a digital crossover with multi frequencies and slopes choice like dbx PAdriverack.?

Yes as long as you are going to actually use it.

Can I run two active filter 5235 in serial with 300Hz and 1000Hz cards?

I think you are better off with the steeper 24db slopes

I think use the 2123H from around 300Hz to 1000Hz

I would go higher on the 2123 so you match the directiviy of the 2344 at crossover.

Have Fun

Rob

[pos]

- Can I run two active filter 5235 in serial with 300Hz and 1000Hz cards?

You need to cross the 2123/2344 at 1600Hz to match directivity:
http://audioheritage.org/vbulletin/s...621#post247137

Concerning the 2235/2123 crossover point, that is much more room and placement dependant, so your are up for some experiments:
http://www.audioheritage.org/vbullet...134#post276134

In both cases I would use Linkwitz-Riley slopes (12 or 24db/oct) :
http://www.rane.com/pdf/ranenotes/Li...s%20Primer.pdf

the good thing is that at 1600Hz you do not need to take the horn rolloff into account, so the electrical slope will more or less match the acoustical one.

[screw_squirrel]

Thank you Rob and Pos for your good advices!
Here's a picture of the first version of my project: 14 L box (1/2 ft²).
I did it this morning at work during lunch time. 1/4 ft² seems to be a bit small. I'll post another version with width fiting 4430 size and a place for a future 4 ways extention with a 2405H or 2404H...
Conserning the active crossover I don't know what to think... My expérience is too small, and I know quite nothing about electronics.I'll try to find a M553 crossover, even if I think a driverack PA could help me better because it's more flexible.
Eric

[1audiohack]

You are headed down one of my favorite paths.

I have liked my 2123's enclosures best between 0.5 to 0.75 cubic feet loosely filled with fiberglass.

I agree with the crossover point 2123 to the 2344, 1300 to 1600 Hz. As a bonus, the 2123 and the 2344 (at least with a 2425 or 2426 driver) are right in time with each other at those frequencies if mounted on the same vertical plane so no delay or displacement is required. That makes use of a M553 just fine. Get them together as close as possible, its as easy a combination to make sound great as any I have used.

[screw_squirrel]

Well, I have simulated with WinISD the 14 liters box and the 21 liters box for 2123H with Highpass and Lowpass, Linkwitz-Riley (LR-4) crossover, as if it was done by M553 at 300Hz and 1600Hz. And the result is nearly the same... Something must be wrong in here but I don't know what exactly. I think I have missed one parameter somewhere...

[pos]

14L is already quite big for the 2123H (Qtc ~0.5), so going bigger does change much (especially with a 300Hz cutoff)
You should also consider the volume taken by the driver, so a 14L box will result in a 11L net volume.

For the box layout I would try to keep the 2123H vertically aligned with the 2344 (the 2404 position does not matter much).
I you use symetrical L-R filters it would also make sense to try to align the 2123 and 2425 (the 2123H/2235H alignement does not matter nearly as much) diaphragms, but it will be impossible (or counterproductive) with such a shallow driver. I you cannot time align them geometrically maybe you should use a digital crossover...
You can also try different slopes in WinISD Pro and look at the delay at the crossover point (but keeping the crossing point at -6dB for both drivers). For example a 15cm compensation is equivalent to a 0.44ms delay. That means that if the 2123H and 2425H diaphgrams are 15cm appart (that would need to be mesured...) you should try to achieve a -6dB crossing point with the 2123H having 0.44ms more group delay than the 2425H.

[ratitifb]

increase the internal volume of the dogbox from 14l to 21l is negligible compared to the T/S parameters of the 2123 and its own free frequency response ...

[Robh3606]

even if I think a driverack PA could help me better because it's more flexible.

If that is what you are more comfortable with go for it. The idea with using the 2123 with the 2344 is to get them as close as you can. You are also going to be in a seperate box you can move back and forth so "time alignment" is something you can adjust easilly. I had mine both mounted to the same baffle plain and it sounded fine.

Rob

[screw_squirrel]

Thanks Pos and Ratitifb for your help and support. This shows the initial project with an internal 14 Liters box (net), without speaker. 2123H and 2344A are verticaly aligned and in the depth also. My concern now is to find a M553... Or pick a 4 ways crossover to be ready for the next step => 2404H tweeter

[4313B]

JBL used these drivers in "oversized" boxes to get Fc as low as practical since it plays hell on any passive filter components. If you're going active then the box can be made smaller than the usual 0.5 cubic feet.

[screw_squirrel]

If that is what you are more comfortable with go for it. The idea with using the 2123 with the 2344 is to get them as close as you can. You are also going to be in a seperate box you can move back and forth so "time alignment" is something you can adjust easilly. I had mine both mounted to the same baffle plain and it sounded fine.

Rob

Nice alignment Rob! On my project I have 330mm between 2123H axis and 2344A throat. I wish I could do better.

[screw_squirrel]

JBL used these drivers in "oversized" boxes to get Fc as low as practical since it plays hell on any passive filter components. If you're going active then the box can be made smaller than the usual 0.5 cubic feet.

Thank you for this information.

[screw_squirrel]

Good morning.
As it seems not to be easy to find a M553 crossover at decent price, I am looking further for a backup solution involving my two JBL-UREI 2 ways active crossovers (5234A and 5235) in serial (cascade). That means reproduce 4 original blank cards with 18dB slopes based on 51-5130, and fill it with the correct componants according to 5235 manual. But... I have a big probleme I can't find the reference for the 6 pins connector .
If someone has the answer please help me!
Attached a new diagram with butterworth 18dB slopes @ 300Hz and 1600Hz.
Eric

[pos]

I would stick with L-R filters, at least for the 1600Hz crossover.
Maybe you should get a digital crossover, try different slopes and time delays, and then decide what to do.
I see you are in Paris, I can borrow you a DCX2496 to try if you want (I have a pair).