RB-35 Crossover mods/tweaks

[lgo51]

Had no luck searching for these. Any suggestions/pointers?

Thanks !

LarryO

[Deang]

You're on your own. Current production, so no available schematic. You'll have to figure out how to get the networks out, and then measure the values in order to find suitable replacements.

[lgo51]

Gee, I thought that one of the purposes of a forum is to help mitigate that sort of "aloneness". Maybe I am the first to have a curiosity about a "current production" model.

[Deang]

On the contrary, I do RF-7 networks for folks regularly, and there isn't an available Klipsch schematic for the RF-7 either. I did receive one from another forum member who had traced out the circuit, but I really didn't need it to do my first upgrade - I just thought I did! Once you get the boards out you will see that all of the cap values are marked on the caps themselves. If you don't have an inductance meter, you can remove the inductors, and you will find the values marked on the surface of the PCB. You won't find suitable replacements for the HF inductors, so I would just leave them alone. You can go with a nice air core in place of the steel laminate LF inductor, but make sure the replacement matches in both inductance and DCR.

I said "you are on your own" because to the best of my knowledge, no one has done anything with an RF/RB-35 yet, including myself. I do know getting the networks completely out will be a pain, because to get them all the way out you have to be able to get to the horn to disconnect the leads, which means you have to remove the front faceplate. Now, if you're good, you may be able to simply work from behind the speaker with the terminal cups and attached networks pulled out. I simply don't know if it's possible, and you will just have to try it and see!

[lar418]

Hi Larry O,

I've just purchased a pair of RB-35's on line and they should arrive next week. I'll definately be tearing into them to examine and upgrade the crossover with better parts as a minimum. I'll post the info in a few weeks after I have some time to do some critical listening to see if the upgraded parts make a difference.

Lar418

[lar418]

Just completed the mods for these speakers and the results were very satisfying. This speaker is constructed very well and fairly easy to work on. I modded both the crossover and the dampening. Out of the box this speaker is voiced on the bright side and IMO the tweeter needed to be padded down a little. It was about 2 db's louder then the woofer Also the bass was a little on the boomy side, but not bad at all.

You will need a star screw driver to remove the front panel, woofer and crossover network. Once these are removed the mods are fairly easy.

Crossover Mod:

Replace the 6 ohm sand cast resistor with a 10 ohm Eagle or Mills resistor. (This will attenuate the tweeter by 2 db's)

Replace the 3uf and 5 uf caps in the tweeter circuit with Solen or better caps. (With the stock caps the tweeter sounded like a transitor radio. With the Solen caps the tweeter sounds much fuller. The Solens are about the same size as the stock cap and fit nicely on the board. Hovland or Auricaps can also be used, but they will have to be monuted off the board. I took mine one step further by using GE Oil caps from BEC, but it was allot more work. Solen's get you 90% to 95% of the improvement in sound and the Oil cap get you that extra 5%.)

Replace the 16uf cap with a Bennic cap. (It is a little longer then the stock cap so the lead on one side has to be bent under it to match up with the hole in the board.)

Dampening:

Remove the foam sheet and line the back, top and half the sides near the woofer with Deflex Panels. Wrap the tweeter horn with rope caulk and Duct tape. Wrap the bottom and sides of the port with rpoe caulk and duct tape. Place a piece of Deflex panel on the top of the port and on the interior brace directly behind the woofer. Use Welbond to attach these panels. (This really tightened up the bass and made the midrange clearer and cleaner.)

Cost: The Solen/Bennic caps and Eagles resistors cost about $20 for the pair. 8 delfex panels are used at a cost of $88. At a minimum use 4 panels, placed on the back and on the interior brace.

These speaker didn't sound bad at all stock, but these mods brought them to another level!

See attached pictures.

[lar418]

Picture of horn and port dampening.

[lar418]

Crossover with Solens

[lar418]

Crossover with GE Oils

[colterphoto1]

Oh, stop, you're having way too much fun!

[Deang]

Nice job, but why the cans?

[lar418]

DeamG and Colterphoto,

Thanks for the positive words!

DeanG,

I just finished modding my La Scala crossovers and went from a DHA2 crossover with Hovland caps and Goertz coils to a slightly modded type "A" with Goertz coils and GE cans. The La Scala with the modded "A" and the cans sounded better to me. There was less grain in the female voice and it just sounded more natural. Since I liked what I heard, I thought I'd try the cans in the RB-35's. I did try using some Hovland caps, but the board was too small. If I hot glued the caps on top of the coils, I couldn't get the board back in. It was easier just soldering leads to the board, mounting the cans in the box and attaching the leads to the cans just like the speakers are connected. (See Picture)

To my ears the Solens are a very nice sounding cap and the Hovlands are a little smoother. To me the cans are smooth, but also let a little more information through. I admit that I've never tried a MusicCap or an AuriCap in my crossovers.

I also considered changing the coils and building a new board. After hearing no improvement with a Goertz Air coil compared to the stock coil, I decided to leave that part of the board alone.

BTW: On my modded type "A" I made the following changes.

Moved squawker from tap 4 to tap 3

Changed the 13uf cap to a 6uf cap

Connected the tweeter to tap 4

Changed the 2uf cap to a 1uf cap

It's sounds very nice this way.

[Deang]

Female vocals are supposed to have grain -- you should hear my wife scream at the kids.

I think the LaScala is a bit like the Heresy, with a top running too hot in relationship to the bottom. Do you have your LaScalas pulled out, or in corners?

Since you dropped the squawker and tweeter down 3db, you really can't make any valid comparisons between the capacitors. However, like the Hovlands, the GE cans exhibit very low loss. I'm still on the fence on which is the best way to go -- low loss with attenuation, or a bit of loss and no attenuation.

You may not have been aware of this, but since the DHA is a constant impedance design, you could have set the autoformer up like the ALK so you could attenuate on the fly without shifting the crossover point.

I don't understand the change from 2uF to 1uF on the tweeter filter. You're probably getting very little output from the K-77. The tweeter filter is on the output side of autoformer, and changing taps doesn't necessitate an adjustment to the value(s).

At any rate, you do nice work.

[lar418]

The point about the female voice is well taken. My wife has also exhibited a little grain from time to time.

The La Scala's do have the same sound characteristics as the Heresy, which I've owned previously. My La scala's are presently in an unfinished basement (future winter porject) on a long wall. One speaker is in the corner and the other open on the side. They are about 8' apart and I'm about 8' away from them, which is not the best setup. Eventually, they will be on a long wall, open on both sdes and I'll be sitting about 11' away from them. As you can see I'm using these almost as near field monitors. At one time I considered going to the RF-35's or RF-7's instead of the La Scala's, but I like that horn sound.

I did listen to just the squawker and tweeter indiviually with different caps when I made my decision to use the cans. Listening to a tweeter alone can be a little rough at times. At their price point, the cans sound as good as the Hovlands at half the cost.

I was aware of the constant impedance of the DHA network and was originally going to leave the resistor on the Autoformer, but I'd need 4-10 ohm cans per side and BEC encourged me to just try the Type "A" network. Although, I wonder if the great variation in impedence over the bandwidth effects my amps performance. Maybe the grain that I was hearing was from the 39uf Solen cap or Goertz coil that I used on the squawker in the DHA crossover. The Solen was bypassed with a 1uf Hovland cap, but I'm not really sure if bypassing works. I've read many post that say it doesn't. I might try putting the resistor back, adding a few cans and comparing the two crossovers. Any suggestions??

I was trying to reduced some sibilance with the cap change on the tweeter. Using a signal generator and sound level meter, I noticed a peak in response from 4k to 7k, so I thought that I would raise the crossover point of the tweeter to reduce this. This was apparent with both crossovers. Plus with my seating arrangement the tweeter can be overpowering. If I had a larger room, it probably would not be a problem. Great point about the position of the tweeter cap the the Autoformer, I totally missed that.

I welcome any suggestion!