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View Full Version : My pseudo 4425 / MR822 / SR4722 project



chad
12-02-2005, 04:02 AM
My MR 802 stage monitors (now with 2426h) have been a part of my toolkit as a paid performing musician for the last 5 years. Have always thought it would be nice to have a pair of speaks, of some sort, that would just reside in my rehearsal / practice / music room. Have always admired the 4425 and SR 4722 systems, and they fetch a good price on epay.

Got to thinking, I already have a spare 2022h 12" driver, (3) 2416h, and a spare MR802 crossover.... so I bought another 2022 and a pair of 2.0 cu. ft. boxes. I calculated the volume of my good sounding MR802's and the new boxes should be about right. The listening room has very dead acoustics, and is about 15' x 20'.

Here is the proposed system:

LF drivers: 2022h
LF enclosure: 2.0 cu. ft.
HF drivers: 2416h
HF horns: 2342 or 2344
Xover: MR802 (73224-001)

So I was wondering...

Should I pursue the 2342, or the 2344 horns?

How should I port the LF enclosure?

:confused::)

Don Mascali
12-02-2005, 05:05 AM
I picked up a pair of "2344A-modified" horns that JBL used in the 4726A. The area behind the horn had been drilled to allow 2" pvc vents to exit behind the "Butt scoops". This is a great idea for me as I am building a surround speaker with old L100t boxes and the rear vent won't work because they will be hung from the wall. They also have a radius cut to allow the lower edge to cover a 12" driver when they are close coupled.

The 2344 would play well a little lower than the 2342 (1K vs 1.2K). Zilch has a ton of info in the Q&D thread. The 2342 is about 9" square and the 2344 is 12 1/4".

http://www.jblproservice.com/pdf/Sound%20Power%204700%20Series/4726A.pdf

http://www.audioheritage.org/vbulletin/showthread.php?t=2371&highlight=2344a+modified

Good luck,
Don M

Zilch
12-02-2005, 09:55 AM
A quick look at MR802 says that crossover is not optimum for either 2342 or 2344 horns, as the CD compensation (none, apparently,) is wrong for them.

http://www.jblproservice.com/pdf/MR800%20Series/MR802.pdf

Plan on trying the 1.2 kHz NL200t3 first for a better match.

I've shown it running 2416H-1 on 2342 in this post:

http://audioheritage.org/vbulletin/showthread.php?p=79460&highlight=2416H-1#post79460

It may play even better with your 2022's than the LE14H's I'm using.

Crossover construction is detailed earlier in Q&D thread, including parts list and the DC-biased version used in that post.

It will work with 2344 also, but you'll need a threaded throat adapter such as is on 2426 drivers.

The original application is here:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L200t3%20ts.pdf

Thanks again to Giskard for turning us on to this simple, but highly capable crossover with built-in HF boost for the Biradial butt-cheeks.... :thmbsup:

BB6P says your 2022H driver in 2.0 cuft. box is ideal for their suggested "extended bass" tuning, and it's one of those combinations that doesn't require ducting, rather, merely a port hole (or two) in the 0.75" front baffle:

2 X 2.571" round or 2.281" square
1 X 4.106" round or 3.643" square
Triangles or slot(s) of equivalent area will work as well.

The suggested (quieter at high SPL) ducted ports are 2 X 4" round X 4.46" long, or,
1 X 6" round X 4.369" long.

It'd be good if someone confirmed my box design calculations here before you cut wood, tho. :p

You'll want to use a sub with them, probably; you'll be running out of cone displacement at 50 Hz, 200 Watts, though they'll be pretty damn loud there at 124 dB (300 - 400 Hz).

You've chosen an excellent combination to build, looks like:

chad
12-04-2005, 01:40 PM
I picked up a pair of "2344A-modified" horns that JBL used in the 4726A....The 2344 would play well a little lower than the 2342 (1K vs 1.2K). Zilch has a ton of info in the Q&D thread. The 2342 is about 9" square and the 2344 is 12 1/4"....


Hey Don, thanks for the info and links, looks like I have some reading to do:D.

chad
12-04-2005, 01:59 PM
...(insert much good info on my project here)...:D

Thanks Zilch. Especially appreciate the info on the CD compensation, port sizing, and the NL200t3. Oh, and I do happen to have a pair of the thread-to-3 bolt adaptors:).

doodlebug
12-06-2005, 04:19 PM
Zilch, you said: "The original application is here:

http://manuals.harman.com/JBL/HOM/T...L200t3%20ts.pdf (http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L200t3%20ts.pdf)

Thanks again to Giskard for turning us on to this simple, but highly capable crossover with built-in HF boost for the Biradial butt-cheeks.... http://audioheritage.org/vbulletin/images/smilies/thumbup.gif"

So, as I'm preparing to update the caps in the original 4425 crossovers, what is your advice for substituting the HF crossover circuit for the same 2416H/2342 combo? Should be easy to implement and is relatively low cost, too.

I'm thinking out loud, here, and haven't thought through the implications just yet but did wonder if I could benefit from someone else who's already 'been there...done that'.

Cheers,

David

Zilch
12-06-2005, 04:46 PM
Hi, David.

I'f you've got original 4425 crossovers, stay working with them. They are optimized for your driver/horn combination, and have adjustability.

NL200t3 is more suited to DIY projects with either of the Butt-cheek horns, and a variety of drivers, because it's so simple and inexpensive to build.

Works fine, but it ain't the "Real deal."

doodlebug
12-06-2005, 06:26 PM
That's cool, thanks. Original part values it is, then.

BTW, most of the UREI 809 xover caps got replaced this weekend - missing a couple yet to be ordered. Resulted in a definite improvement mostly in the HF levels, which had to be backed way off and is a bit crisper in the soundstaging. Have 2 other caps to replace in the HF circuit. Only using original values and will bypass them once I get it all burned in a bit more.

Cheers,

David

chad
12-23-2005, 03:09 AM
Ok, some more parts have arrived. Thus far, I have:

2.0 cu ft boxes
2342 horns
2022h woofs
2416h tweets
MR802 xovers (Zilch - these xovers have a "0, +2dB, -2dB" switch for the horn level so I should be able to find a pleasing sound even though I won't have the same CD compensation as the NL200t3's I'd like to build :))

Awaiting:

Jasper circle jig ala Parts Express (for use with a router to cut round holes in baffle)
NL200t3 xover - I want to build a set ala zilch, but for now the MR xovers will have to do :D

Hamilton
12-23-2005, 09:06 AM
Chad, here's a pic of a homebrew nL200t3 with a 5 ohm L-pad installed to give you an idea about a layout. Zilch informed me that I should rotate the iron core inductor 90 to eliminate crosstalk, which I will do maybe next week.

chad
12-23-2005, 09:04 PM
Hamilton -

Splendid!! Thanks for the inspiring photo - I've never built a crossover before and I really look forward to it!!!!

:)