Another DIY 4425

[John W]

I biased the HF section also.
The initial results were a little too bright. I need to Lpad the HF section to bring it down a little.
Doing this I need to keep the 4ohm impedance, so I put together a little spreadsheet that calculates resistor values for an Lpad. It is set up with 4ohm, but if you use it, you can change the 4 to 8, or 16 or whatever.
I ordered a few combinations of resistors, and decided to finish the cabinets while I wait their arrival.
Next step is to get a more accurate measurement of the frequency response and incorporate the Lpad.

[Zilch]

Another option: parallel the two gangs of 8-Ohm stereo L-Pads to make 4 Ohms for testing to determine what you ultimately need.

See Parts Express #260-251 or 260-260....

[John W]

I have finally got these speakers up and running. The current version of the crossover is much like the one at the start of the post except that the 2.2uf was replaced with a pair of 4.3uf and biased. Also I found that a 3db L-Pad brings the top end down to just where I like it. I must say that I really like the sound of these. They are a little larger than I first envisioned, but they really fill the room with nice music.

[Zilch]

YES! And just beautiful in their simplicity, too....

[In many ways.... ]

[duaneage]

Beautiful job. They look store bought original to me.


My counterfiit JBLs

http://audioheritage.org/vbulletin/s...ht=4411+clones

[John W]

One thing of note is that I was having a little trouble rounding up some 2 1/2 tubing for the ports. In the end I found some nice stiff cardboard shipping tubes at the local office supply store. They actually come in a range of diameters from 1 1/2 to 3 or maybe bigger and are about 2 feet long. Only cost me $1.50

[Zilch]

Where did you end up on the LP of the crossover? Stock NL200t3 with 3.0 mH laminate core inductor, or 3.8 mH per 4425?

It's amazing how effectively that simple HF compensation works. Several others I know are building with it now. We'll have more results reported here soon.
The forum owes SOMEBODY a keg of their favorite beer, I say....

[John W]

I used the 3.8mh inductor, like the 4425 schematic.
It sounds good...but I really need to work on my test setup.
When I measure this stuff using a mic hooked up to the PC its hard to tell whats going on.

[Zilch]

Yup. We need a thread on DIY RTA.

I can NOT do it without RTA.

No way....

[duaneage]

Electrical pvc conduit comes in 2 1/2 in ID It is grey and sold at electrical supply houses. After I sank my power feed for the house I ended upwith plenty. They also have 3 inch in electrical pvc conduit.

I scored 5 Inch ID pvc couplings to make midrange enclosures. 6 bucks each.

[Earl K]

Beautiful John just Beautiful !

[John W]

Someone was selling a Behringer DSP8024 locally for a good price, so I snatched it up and added a measurement mic. Finally I can get some fairly accurate measurements. It was a nice fall day here in the NW so I pulled a setup outside to preclude any room reflections and hooked it up.

Here is a shot of my test setup:

[John W]

Here is the pink-noise response measure with a 1db scale grid, followed by the response with a 0.5 db grid.

[John W]

Overall, not to bad.

[Zilch]

WAY cool!

No WONDER they sound so good, huh?

Looks like you're within +/- 3 dB the whole way, if I'm reading it correctly.

JBL'd say "SHIP it!"

Now try the NL200t3's 3.0 mH/20 uF combination in the LF and see it it'd be an improvement.

You probably do want to use the laminate core for a little more low end.

[John's a member of the Lansing Heritage research staff now.... ]