View Full Version : New guy needs 3105 crossover advice, perhaps more!

06-22-2005, 07:09 PM
Thanks in advance. Installation of a home theatre has me looking to restore my old speakers and add a center chanel. I THINK I should get another 2405 and K110 for the center chanel, as that is what my main speakers use for mid and hi. (I bi Amp with 2225's for bass) Further, I feel I should have three matching crossovers, as the ones I have are very old and well used. There are several ways to go, and I have found the 3105 to be the right crossover for my 2405's, but have discovered that they are meant to work with a 16 ohm 2440 as the mid.

Well, I wonder if the 3105's would work ok with my K110, as I dont want to hunt down 2440s. To further complicate things, my K110's are 8 ohm, so I would have to put them is series with a resistor.

I hope it will work well, but I could always buy a bunch of inductors and caps, and build simple crossovers. (Design advice gladly accepted)

Back in '80 the speakers were 2405, k110, LE15A, with passive crossovers designed by my electrical engineer neighbor. I was a teenager, and darn glad to have them. They sounded good, and rocked!

Thanks All,


06-22-2005, 07:25 PM
Welcome aboard!

Many of the JBL passive Xovers were specified in the large playback / theater systems with both single driver (16) and dual driver (8) combinations so don't lose a lot of sleep using the 8 ohm K110's.

The crossover caps don't age that well so replacing them with new, high grade types will definitely help, There are others who are familiar with this mod so post a question specific to that on the forum.


06-22-2005, 08:54 PM
Good to be amongst the like minded! I should have known you would chime in to help. Thanks for all your advice, clearly I've decided to try to stick with my old speakers.

So you're tellin' me I can use those crossovers and 'resistorize' my k110's to 16 ohm. Great, because I'd been looking into designing my own passive crossovers, and could not find a formula to determine inductors and caps for a 12 db set.

I'll wait a while and see what elses pops up here, but most likely I'll be looking for a slot, a k110, and three 3105's.

I still like the idea of putting the 2410's on subwoofers, and when I have the time to build boxes, and get a crossover, and whatever else, I'll have some cool speakers for the den. Wife permiting!


12-14-2005, 08:28 PM
in the original post I said I used 2225's for bass. That was an error. they are 2205's.

I will stick with the biamp setup, and build simple passive crossovers for the K110 to 2405, left right and center chanel. Three 3105 crossovers is just not needed for this incarnation.

Anybody have crossover advice? I'd like to keep it simple, as this driver combo is not the best, and I'm stockpiling cash and reasons to spring for something brand new!http://www.audioheritage.org/vbulletin/images/icons/icon10.gif

Mr. Widget
12-14-2005, 09:35 PM
If you can read a simple schematic and solder....


Though I'd build a simple third order network at 10KHz myself or at least the 3106.



12-15-2005, 12:28 PM
Thank you, Mr. Widget:

I can solder, and like the 3106, because it crosses at 7khz, the low extreme of the 2405. I can read the schematic well enough, and could set off on my own right now, but that sort of independence may well be why I’m rebuilding the speakers.

Now, as you read this, keep in mind that friends often tell me to relax and not be such a control freak. You mentioned building it at 10khz, which clicks with my concern that I should set the crossover point a bit higher than 7Khz, to ‘protect’ the tweeter. (In a quick search, I could not find the Fs for that tweeter.) Trouble is, the K110 is only advertised to reach 8khz. Why 10Khz? Left on my own, I’d follow the schematic for the 3106, and try to cross at 7.5Khz, but having an expert guide me is comforting. I bet parts availability, and manufacturing tolerances, will have something to do with the final choice? (Remember the line from the original Terminator movie when Arnold is in the gun store asking for weapons, and after requesting ‘a plasma gun in the forty megawatt range’ the proprietor replies: “ only what you see on the shelf, pal”)

I will buy my components from Parts Express, and will buy the mid quality parts that fit the design – this isn’t Project May. Stop me if I’m wrong. I recall they have info to help you design a crossover. Would it be reliable info if I wanted to ‘adjust’ the 3106 to another frequency?

Again, thank you for your time. I must travel for Christmas, but have already primed my dear wife with the idea that until the spring thaw, I’ll be in the shop, working on three important projects. My speakers, a dumbwaiter, and Her dining room table. Bless her, she goes along with me when I say I’m building a dining room table ‘for her’ – she knows darn well how much fun I will have building it and bragging later. Three months, three projects – what will foil such a plan?

I look forward to posting my results.


One more question: the 3106 is 8ohm, should I build it as shown and put a 16ohm resistor in parallel with the 16 ohm 2405?:confused: (http://www.audioheritage.org/vbulletin/misc.php?do=getsmilies&wysiwyg=1&forumid=4#)

Mr. Widget
12-15-2005, 01:28 PM
Trouble is, the K110 is only advertised to reach 8khz.Ooops... I guess I didn't really read your entire post... I assumed some sort of proper midrange... I wouldn't use the K110 above 5KHz. I would go with the baby cheek tweeter and use a lower crossover point if I had to use the K110. Twenty-five years ago I used the EV T35A with the K120... it was pretty good.

One more question: the 3106 is 8ohm, should I build it as shown and put a 16ohm resistor in parallel with the 16 ohm 2405?:confused: (http://www.audioheritage.org/vbulletin/misc.php?do=getsmilies&wysiwyg=1&forumid=4#)There is no 8 ohm 2405... this has been discussed on many threads.