Need speaker/crossover help - modifying Leslie cabinet

[duncand]

Hello,
I have a Leslie 125 that contains a 20W tube amp and a 12" full-range Jensen.

What I want to do is to add a 12"-ish horn to the cabinet in order to get more punch on the high end. I hope to do this without replacing the Jensen, but I will if I need to.

What I don't know how to do is to pick a speaker and crossover that will be correct for the 20W amp and the speaker I currently have.

Looking for advice in choosing parts to buy.
Cheers!

 

[TLS Guy]

Hello,
I have a Leslie 125 that contains a 20W tube amp and a 12" full-range Jensen.

What I want to do is to add a 12"-ish horn to the cabinet in order to get more punch on the high end. I hope to do this without replacing the Jensen, but I will if I need to.

What I don't know how to do is to pick a speaker and crossover that will be correct for the 20W amp and the speaker I currently have.

Looking for advice in choosing parts to buy.
Cheers!

The Leslie speaker is for the Hammond organ. It should already have a crossover. There should be two horizontally opposed horn tweeters at the top of the cabinet, driven by a belt. These horns rotate and give a tremulo by the doppler effect. The speed of rotation and therefore the frequency of the tremulo can be varied by a control on the Hammond.

That is a classic, and valuable if properly restored. Please do not muck it about.

If the rotating horns and or rotational mechanism is missing, look for parts on eBay. Usually the belt is missing due to breaking from age. You should be able to take measurements and replace the drive belt.

 

[duncand]

The Leslie speaker is for the Hammond organ. It should already have a crossover. There should be two horizontally opposed horn tweeters at the top of the cabinet, driven by a belt. These horns rotate and give a tremulo by the doppler effect. The speed of rotation and therefore the frequency of the tremulo can be varied by a control on the Hammond.

That is a classic, and valuable if properly restored. Please do not muck it about.

If the rotating horns and or rotational mechanism is missing, look for parts on eBay. Usually the belt is missing due to breaking from age. You should be able to take measurements and replace the drive belt.

Sorry, I have a Leslie 125 - emphasis on the 125. There is no horn on this model, and I am going to modify it to have a horn. This is because I do not have enough money to afford a 147.

 

[TLS Guy]

Sorry, I have a Leslie 125 - emphasis on the 125. There is no horn on this model, and I am going to modify it to have a horn. This is because I do not have enough money to afford a 147.

That's right the 125 has a single rotating 12" speaker with two speeds.

You will need to attach a horn to the driver and your simplest solution is to use a piezo horn, that will not need a crossover.

The horn must move with the woofer or you will get nasty dissonance.

You can connect the piezo horn in parallel with the woofer.

 

[duncand]

That's right the 125 has a single rotating 12" speaker with two speeds.

You will need to attach a horn to the driver and your simplest solution is to use a , that will not need a crossover.

The horn must move with the woofer or you will get nasty dissonance.

You can connect the piezo horn in parallel with the woofer.

Off topic, but I'm going to mount it so that the speakers both blow thru the same spinning baffle. I can just pick up any piezo horn? Why won't it need a crossover?

 

[TLS Guy]

Off topic, but I'm going to mount it so that the speakers both blow thru the same spinning baffle. I can just pick up any piezo horn? Why won't it need a crossover?

That will be correct. Piezo tweeters are high impedance and very efficient. That naturally roll off the bass without damage. The size of the horn will determine your LF cut off, so the bigger the horn the lower it will play.

This is a instrument speaker so we are not talking accurate reproduction. Piezo tweeters are cheap enough and you can experiment with them until you get the effect you are looking for.

 

[jostenmeat]

Leslie cabinets . . . what is next?!

First time this has come up (in assistance terms) that I have seen in any AV forum. I find it highly amusing. I will give my first 5 star rating in a long time.

 

[duncand]

Thanks!

I posted here because I was in search of some real audio braniacs. (I am not.) I learned something new today about tweeters and for that I am much obliged.

 

[duncand]

That will be correct. Piezo tweeters are high impedance and very efficient. That naturally roll off the bass without damage. The size of the horn will determine your LF cut off, so the bigger the horn the lower it will play.

This is a instrument speaker so we are not talking accurate reproduction. Piezo tweeters are cheap enough and you can experiment with them until you get the effect you are looking for.

One last question: Will this decrease the overall volume at all? Do I need to worry about which horn to buy in terms of the 20W amp, or does that not even matter? Do I need to worry about the tweeter's watts?

 

[highfigh]

One last question: Will this decrease the overall volume at all? Do I need to worry about which horn to buy in terms of the 20W amp, or does that not even matter? Do I need to worry about the tweeter's watts?

This kind of tweeter isn't like a regular speaker- it doesn't have a voice coil and magnet assembly. It can be damaged if you send the wrong signal through it but that will also kill your Jensen speaker. It won't be louder, just more full-range.

What model of Jensen is it? Also, what is the 6 digit code on the speaker frame? It's on the edge near one of the screws, starting with 220. That can be used to tell how old it is.