Hammond speaker add on question

[New2twg]

I have a Hammond M103 with field effect coil speakers and a AO29 amp that I would like to add an 8 ohm, passive permanent magnet external car speaker box and use both at the same time.

[New2twg]

Upon closer inspection, the car speaker box is a single coil 4 ohm passive permanent magnet speaker.

[tpappano]

I must ask, what do you wish to accomplish by adding the second speaker? Is it to perhaps brighten up the "high end"? Is it a 6x9, or something similar sized? Putting the 4 ohm car speaker in parallel with the 8 ohm organ speaker allows the car speaker to take the majority of the amp's output and you might hear better "highs" from the car speaker, but the organ speaker will be getting less signal to produce the "lows". A more pleasing result might be obtained by putting a capacitor in series with the car speaker to act as a simple crossover, allowing each speaker to best reproduce the highs and lows. In any case, go ahead and hook it up and see what it sounds like, you may like it just fine.

[New2twg]

Thank you for the informative response! Just wanted to see how it sounds out of curiosity. I'm using signal split between AO29 preamp/power and small guitar amp. The guitar amp makes the organ sound dull by comparison but good together. I have the car speaker unused in the garage and read in the manual that an extension speaker may be added. I know very little about this kind of thing and was wondering if a permanent magnet speaker is safe to add to field coil type and where to clip on.

[David Anderson]

A tube amp works best driving the impedance it was designed for, 8 Ohms in this case, so if you wire a 4 Ohm speaker in parallel with an 8 Ohm speaker, you now have a 2.7 Ohm load.

It would be better to take a line out from the organ and run it through a separate power amp and speaker. If a guitar amp makes it sound dull, then maybe there's a problem with the guitar amp.

[New2twg]

Makes sense, I worry a low impedance load seen for a tube amp might be dangerous and I'm not sure how to connect PM coil to field effect coil. Sorry, I should have said the guitar amp sounds great-a lot of highend tone available, making the Hammond speakers sound muffled. I have both guitar amp and Hammond amp/speakers playing together and it sounds nice with the reverb on the organ speakers. I think both are working correctly. I played guitar through it and the reverb was nice. I should leave it at that... but, I thought I could add 15" car sub on the opposite side of the guitar amp for a fuller sound. Thanks again for your help. I'll post results if I try to add to the amp output on the chassis.

[enor]

An M-100 shouldn't have field coil speakers - they disappeared about midway thru the M-3 series. Are you positive that's what's in this organ?

[New2twg]

Sorry for the late reply, I had to look behind organ. They're definitely coil speakers. Two 12" and one 8" off the reverb amp.

[tpappano]

That doesn't make sense to me, no way a M100 would have three field coil speakers. I could see *one* if someone put an old M-series amp and speaker into an M100. I'll bet yours are stock permanent magnet speakers. How many wires actually go to each speaker? Normal would be two each, colored black and green.

[tpappano]

A "field coil" speaker looks like this :

[tpappano]

A '60s vintage permanent magnet speaker usually looks like this :

[enor]

Also - AFAIK there's no Hammond reverb amplifier designed for field coil speakers. Any model with reverb is new enough to have permanent magnet speakers all around.

[handyczech]

Just to restate the obvious, A "field coil speaker" has four wires leading to it-2 for the signal and 2 to power the electro-magnet which energizes the speaker. A permanent magnet speaker has 2 wires. A steel object will hold hard to the magnet. Not so on the field coil with the organ off. I am not aware of the M-100 series having other than permanent magnet speakers. I do not believe there is provision for that in the amp.

[New2twg]

Apologies, you are correct. There are only three wires on one hooked to two terminals and two on the others. Also, the amp says AO-29-13. The horseshoe thing threw me off. Thanks for the clarification. I'll look for some wire to try the external speaker.

[David Anderson]

If you want more highs from the organ, you could always add a horn compression driver and a horn along with a simple high-pass crossover. The impedance of a standard speaker increases with frequency, so you can just let the 12" speaker run full-range and cross the horn driver at a frequency that gives you the highs you want.