Replacing field coil speakers with resistors

[jordan86]

Starting *yet another* new thread on my Hammond H1 conversion, since it seems more appropriate to the issue at hand.

I moved recently and am just getting settled. Finally got a chance to load the field coil speakers that came with my amp into a 2x12 cab and test it out.

First fire up was very disappointing to say the least! The amp sounded pretty awful. No low end. Just bright and harsh. Seemed fairly quiet too for 30ish watts. Surprisingly low in headroom and earlier breakup than I expected. Not sure what was a fair expectation since this is ALL new territory for me, and I've never heard these organ speakers in any context. But I decided to bypass the voice coils (leaving field coils connected for bias) and go into one of my other closed back 2x12 cabs just to see.

Now we're talking! Tons of low end and punch. Highs were still bright but way smoother. And way more volume. Sounds like a nice 30w guitar amp. I got to about 1 o clock on the volume pot before breakup. So I think the stock speakers need to go.

I'm still learning but you all have informed me that I need to replace the field coils with some 30w resistors if I want to go with a different speaker setup. I can see where in the circuit that needs to happen based on the schematic. I presume these will dissipate quite a bit of heat though? Is there a best placement inside the chassis that I should look at? I may also ditch the mulitpin speaker sockets and move the speaker jack to the back side of the chassis. More like a standard guitar amp.

Thoughts? Advice?

Schematic
https://el34world.com/Forum/index.php?action=dlattach;topic=28902.0;attach=98603;image

Preamp:
https://el34world.com/Forum/index.php?action=dlattach;topic=28902.0;attach=100341;image

[sluckey]

You need one 5KΩ@30W and one 250Ω@25W. I suggest these US sellers on eBay. These will neatly mount on the PT end side wall.

I mounted my big brown field coil replacement resistor on the left side in my Rocky project.

[jordan86]

These will neatly mount on the PT end side wall. I mounted my big brown field coil replacement resistor on the left side in my Rocky project.

Thanks, Sluckey! I like the idea of using the side wall.

[jordan86]

Well, if I am anything, I am CHEAP. Before buying more parts, I was curious to see if my stock speakers were just broken or if they could be utilized. Based on the "no low end" situation I thought, "Maybe they are just out of phase"? So I flipped voice coil leads on one speaker. Low and behold. Beautiful music. There's a wiring harness they came with that must have been wired wrong. I never did do the old 9V battery polarity test because of the field coils.