Hi,
I'm going to start off by saying that I am not formally educated in electrical engineering. I just know enough to be VERY dangerous.
I am building a Leslie-style speaker and need some help with the crossover. The Leslie has a 4 Ohm 6" speaker and my main speaker cabinet runs a 8 Ohm 12" speaker. I would like to make a low-pass filter for my main cabinet, such that when the Leslie is engaged the full signal goes to the Leslie speaker and frequencies above 400 Hz are cut to the main speaker cabinet. The idea is that the main speaker cabinet will supplement the Leslie 6" speaker's lack of low-end.
My goal is to be able to enable the Leslie/main speaker combo with minimal variation in impedance. It's easier on my guitar amps to increase impedance rather than decrease impedance, as far as I understand. So, this leaves traditional parallel crossovers designs out of the question. I need to run these speakers in series.
I've attached a drawing of my proposed circuit and I'm wondering if those of you who know what you are doing can tell me if I've reached my design goals. The resistors/potentiometer network is designed to create a variable resistance between 6-8 Ohms. In parallel with the 8 Ohm speaker, I'm hoping this appears to be a 3.4-4 Ohm impedance to the amp (but I don't know anything). I added the potentiometer as a rheostat to slightly adjust the impedance of the 8 Ohm main speaker. This speaker is much more efficient than the 6" Leslie speaker and I'm hoping that this will help me dial in the appropriate volume levels.
Please, those of you who are knowledgeable in such things, tell me if I'm crazy or not. Will this circuit produce an impedance of around 8 Ohms to satiate my amp? Will this design only cut upper frequencies to the 8 Ohm speaker while permitting full-frequency signal to the 4 Ohm speaker.
I thank those who may shed light.
Dave
I'm going to start off by saying that I am not formally educated in electrical engineering. I just know enough to be VERY dangerous.
I am building a Leslie-style speaker and need some help with the crossover. The Leslie has a 4 Ohm 6" speaker and my main speaker cabinet runs a 8 Ohm 12" speaker. I would like to make a low-pass filter for my main cabinet, such that when the Leslie is engaged the full signal goes to the Leslie speaker and frequencies above 400 Hz are cut to the main speaker cabinet. The idea is that the main speaker cabinet will supplement the Leslie 6" speaker's lack of low-end.
My goal is to be able to enable the Leslie/main speaker combo with minimal variation in impedance. It's easier on my guitar amps to increase impedance rather than decrease impedance, as far as I understand. So, this leaves traditional parallel crossovers designs out of the question. I need to run these speakers in series.
I've attached a drawing of my proposed circuit and I'm wondering if those of you who know what you are doing can tell me if I've reached my design goals. The resistors/potentiometer network is designed to create a variable resistance between 6-8 Ohms. In parallel with the 8 Ohm speaker, I'm hoping this appears to be a 3.4-4 Ohm impedance to the amp (but I don't know anything). I added the potentiometer as a rheostat to slightly adjust the impedance of the 8 Ohm main speaker. This speaker is much more efficient than the 6" Leslie speaker and I'm hoping that this will help me dial in the appropriate volume levels.
Please, those of you who are knowledgeable in such things, tell me if I'm crazy or not. Will this circuit produce an impedance of around 8 Ohms to satiate my amp? Will this design only cut upper frequencies to the 8 Ohm speaker while permitting full-frequency signal to the 4 Ohm speaker.
I thank those who may shed light.
Dave
Attachments
The inductor shunts the LF past the 4 ohm driver (so acts as a HP), the 8 ohm gets a FR signal.
dave
dave
Thank you for taking the time to reply.
Does this seem like a more reasonable configuration? I don't fully understand inductors, but my thinking is that since they work with AC this configuration may limit frequencies to both speakers. In my limited experience, I haven't seen low-pass filters use inductors in parallel with the speaker. They seem to be used in series.
The resistor network is intended to make the 8 Ohm speaker act like it is a 4 Ohm speaker, so that the two speakers in series equal around 8 Ohms. That way I can, hopefully, kick-in the Leslie without many bad side-effects.
Thanks,
Dave
Does this seem like a more reasonable configuration? I don't fully understand inductors, but my thinking is that since they work with AC this configuration may limit frequencies to both speakers. In my limited experience, I haven't seen low-pass filters use inductors in parallel with the speaker. They seem to be used in series.
The resistor network is intended to make the 8 Ohm speaker act like it is a 4 Ohm speaker, so that the two speakers in series equal around 8 Ohms. That way I can, hopefully, kick-in the Leslie without many bad side-effects.
Thanks,
Dave
That one acts as a LP for both drivers.
You want to run the 4 ohm FR and LP the 8 ohm? Put a cap shunting the 8 ohm.
Note that if you are only putting a filter on one driver you won't get a nominally flat impedance any way you wire them up, i'd start with no Rs.
dave
You want to run the 4 ohm FR and LP the 8 ohm? Put a cap shunting the 8 ohm.
Note that if you are only putting a filter on one driver you won't get a nominally flat impedance any way you wire them up, i'd start with no Rs.
dave
Sorry, that's a somewhat kludgy design, no offence meant.
Use a conventional parallel crossover which will simplify interconnection, just set to 400Hz crossover or whatever you need.
As you see they share grounds , which the series one does not.
I suspect (you didn't post any drawings) that you have a cabinet less 6" speaker rotating on one end of a balanced arm.
I have seen such "Leslie add ons" .
In that case you do NOT want any bass or even low mid frequencies reaching it or you'll murder it.
Nor need for a passive volume control , because everything below 400Hz will go to the woofer, since the 6" can NOT handle them, and everything above 400Hz will go to the 6"... because you want it "Leslied" 🙂
Just buy a ready made 12dB/oct 400Hz crossover and you are all set.
Just as a suggestion, Parts Express and USSpeakers carry them.
Use a conventional parallel crossover which will simplify interconnection, just set to 400Hz crossover or whatever you need.
As you see they share grounds , which the series one does not.
An externally hosted image should be here but it was not working when we last tested it.
I suspect (you didn't post any drawings) that you have a cabinet less 6" speaker rotating on one end of a balanced arm.
I have seen such "Leslie add ons" .
In that case you do NOT want any bass or even low mid frequencies reaching it or you'll murder it.
Nor need for a passive volume control , because everything below 400Hz will go to the woofer, since the 6" can NOT handle them, and everything above 400Hz will go to the 6"... because you want it "Leslied" 🙂
Just buy a ready made 12dB/oct 400Hz crossover and you are all set.
Just as a suggestion, Parts Express and USSpeakers carry them.
Except that those rarely work, and you are unlikely to find an off the shelf @ 400 Hz for a 4 ohm mid-tweeter and an 8 ohm woofer.
You are right about putting a high pass on the small driver.
dave
that's a very pessimistic blanket statement, isn't it?
Tell that to the thousands of home builders who use them all over the place.
Agree on the mixed impedance setup, but my next suggestion (if the OP actually bought it, of what I'm not certain at all) would have been to just use the high pass section with the 6" speaker, to avoid blowing it, and running the woofer full range or maybe clipping the bypass capacitor off, leaving the series inductor as a weaker lowpass crossover.
These days it's much cheaper to buy ready made and junk half of it than build from scratch.
If anything, I'd worry more about the 6" lower impedance speaker receiving mora than a fair share of available power and whether the driving full range amplifier would be happy with a 4 ohms load, being that it was presumably designed for an 8 ohms speaker, so the real help would be suggesting he walks the extra mile and gets an 8 ohms midrange/highs speaker.
We agree on that 🙂
As a side note, I suggest unglamorous off the shelf stuff because I want to keep the OP life simple, I wouldn't suggest him he studies, designs and builds his own crossover, at least not for this one specific project.
Even if somebody posted here a detailed recipe, stating wire bobbins, diameter, turns, etc. , it's hard to get wire in small amounts enough for a single Xover or two, plus having to kludge some kind of winder.
That's why specifying off the shelf is the way to go in these cases.
In fact, I searched a little to check what's actually available, and found this ready made 600Hz 4 ohms high pass crossover, which would be perfect for that application, considering it will protect the presumably unbaffled 6" speaker even more.
600 Hz High Pass 4 Ohm Crossover
An externally hosted image should be here but it was not working when we last tested it.
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Not at all, because it is very true. A crossover needs to be specifically targeted at the drivers used to work properly.
That is what the 1st XO did… the resistors can likely be removed, as they assume a simplistic view of the impedance of a driver.
Made up parts are readily available...
dave
Hey guys,
Thanks for your help. While I suppose I could purchase a ready-made crossover, I think it's more interesting to learn about them.
I have a slight correction. I'm using an 8" 4 Ohm speaker. The Leslie set-up is one of the foam rotating baffle types. The speaker is from a brand new Line 6 Spider IV. I didn't care much for this little amp. It's good for metal-type tones at lower volume, but the overdrive leaves a lot to be desired. So I used the speaker and chopped the cab into a head unit. I actually like this thing now running through my 12" and set to "insanity" mode.
I finally found some information regarding series crossovers and I think this might work. I just don't see a parallel configuration as an option. My main speaker is 8 Ohms and connecting the 4 Ohm Leslie speaker would drop the impedance to 2.7 Ohms. My amp would not be happy with me for that. I don't see adding an additional 4 Ohms in series with the 8 Ohm speaker as necessarily a bad thing as far as my amp is concerned.
I am concerned that if I don't correct the impedance of the 8 Ohm speaker that it will receive twice the wattage as the 4 Ohm speaker, if I'm understanding things correctly. This could present a bit of a problem. The 12" sounds way louder given the same amount of power and I think this crossover configuration may feed more power to it than the 4 Ohm speaker. I just want the 12" speaker to subtly enhance the Leslie.
Thanks,
Dave
Thanks for your help. While I suppose I could purchase a ready-made crossover, I think it's more interesting to learn about them.
I have a slight correction. I'm using an 8" 4 Ohm speaker. The Leslie set-up is one of the foam rotating baffle types. The speaker is from a brand new Line 6 Spider IV. I didn't care much for this little amp. It's good for metal-type tones at lower volume, but the overdrive leaves a lot to be desired. So I used the speaker and chopped the cab into a head unit. I actually like this thing now running through my 12" and set to "insanity" mode.
I finally found some information regarding series crossovers and I think this might work. I just don't see a parallel configuration as an option. My main speaker is 8 Ohms and connecting the 4 Ohm Leslie speaker would drop the impedance to 2.7 Ohms. My amp would not be happy with me for that. I don't see adding an additional 4 Ohms in series with the 8 Ohm speaker as necessarily a bad thing as far as my amp is concerned.
I am concerned that if I don't correct the impedance of the 8 Ohm speaker that it will receive twice the wattage as the 4 Ohm speaker, if I'm understanding things correctly. This could present a bit of a problem. The 12" sounds way louder given the same amount of power and I think this crossover configuration may feed more power to it than the 4 Ohm speaker. I just want the 12" speaker to subtly enhance the Leslie.
Thanks,
Dave
Attachments
Cool.
I missed the post where you ask the OP the full measured parameters of his speakers to design a custom, very accurate crossover. 😕
Not being aggressive but realistic: the OP wants a reasonably working crossover for his unspecified speaker, unbaffled, mounted at the end of a rotating arm:
Yamaha version:
Gibson Maestro version:
or even this really homemade version, based on a piece of 90 deg bent sewer pipe:
An externally hosted image should be here but it was not working when we last tested it.
or worse, the coffe can version:
Considering that a Leslie type rotary speaker is an >>effect<< and never ever intended to be an accurate and flat full range music reproducer, I don't understand why the OP might lose sleep about *possible* fractions of a dB accuracy.
Which nobody has provided so far.
To boot, I'm offering a practical solution to his real world building problem
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I would not buy a pre-built XO, ignoring the fact that he won't find one at 400 Hz for a nominal 4 ohm top and an 8 ohm bottom.
He should at least go as far as figuring out values using a calculator, and then wire in series, they tend to be self compensating.
True this is not hifi, but suggesting something that has no chance of working decently is not a practical solution.
ie 3 mH, 100 uF.
dave
He should at least go as far as figuring out values using a calculator, and then wire in series, they tend to be self compensating.
True this is not hifi, but suggesting something that has no chance of working decently is not a practical solution.
ie 3 mH, 100 uF.
dave
Attachments
I've attached a photo of the unit for your viewing pleasure. The baffle that it originally came with was slightly more dense than Balsa wood. The new baffle and cabinet are made from 3/4" Birch. The cabinet dimensions were taken from the Line 6 amp the speaker was cannibalized from. Unfortunately, all I know about the speaker is that Line 6 says it was custom made. That's all I will probably ever know about it.
This is not a hi-fi project. In fact, I don't think anybody would even enjoy the electric guitar if it were played through a hi-fi amp. Distortion is necessary. Guitarists even appreciate the sound of carbon comp resistors operating out of their intended range. Everybody likes to hear distortion in an electric guitar. It's just a matter of what type of distortion. I was not surprised at all when I learned that one of the secrets to Willie Nelson's tone is that Trigger is amplified and slightly distorted. The same goes for Eric Clapton. His acoustic guitar is dirty.
I think we're getting close here. Once I get the crossover working, then it's time to get the chorale effect out of it. Right now it's a single speed tremolo unit. My tremolo pedal is worthless in comparison.
Take care,
Dave
This is not a hi-fi project. In fact, I don't think anybody would even enjoy the electric guitar if it were played through a hi-fi amp. Distortion is necessary. Guitarists even appreciate the sound of carbon comp resistors operating out of their intended range. Everybody likes to hear distortion in an electric guitar. It's just a matter of what type of distortion. I was not surprised at all when I learned that one of the secrets to Willie Nelson's tone is that Trigger is amplified and slightly distorted. The same goes for Eric Clapton. His acoustic guitar is dirty.
I think we're getting close here. Once I get the crossover working, then it's time to get the chorale effect out of it. Right now it's a single speed tremolo unit. My tremolo pedal is worthless in comparison.
Take care,
Dave
Attachments
Cool, where did you get the foam rotor?
You pulled it from a real Leslie !!!
Everything else can be bought or kludged somehow.
As of the speaker, drop it in the nearest junkbin and get a real one.
A 4 ohms 6" speaker pulled from a small practice amp which I guess was 15W at best will last as much as a snowflake in Hell.
Get a real PA 8 ohms speaker, similar to:
Eminence Alpha 6A speaker. The Eminence Alpha 6A is a 6" 8 ohm speaker. Alpha-6A is a 100 watt RMS 6" speaker.
Faital Pro 6FE200 6.5" Speakers - Faital Pro 6FE200 mid-bass speaker. Faital Pro 6FE200 260 watt 6.5" woofer for all high quality mid-bass applications. Faital Pro 6PR150
they sell an Eminence 500 Hz crossover which will work very well here:
Eminence pxb-500. The Eminence pxb-500 is a low pass crossover. The Eminence pxb-500 500Hz low pass crossover handles 400 watts RMS.
but of course get a real speaker first.
The one you have will die quick, serious.
What head will you use to drive this cabinet?
Or you are using a combo external speaker out?
*Really* , you should use that foam rotor straight with a 12"speaker , you'll end up with something similar to a Fender Vibratone.
Not bad at all and quite suited to guitar use:
Rear:
Front:
Side:
Leslie 16 Rotor Photo by Fastocker | Photobucket
You pulled it from a real Leslie !!!
Everything else can be bought or kludged somehow.
As of the speaker, drop it in the nearest junkbin and get a real one.
A 4 ohms 6" speaker pulled from a small practice amp which I guess was 15W at best will last as much as a snowflake in Hell.
Get a real PA 8 ohms speaker, similar to:
Eminence Alpha 6A speaker. The Eminence Alpha 6A is a 6" 8 ohm speaker. Alpha-6A is a 100 watt RMS 6" speaker.
Faital Pro 6FE200 6.5" Speakers - Faital Pro 6FE200 mid-bass speaker. Faital Pro 6FE200 260 watt 6.5" woofer for all high quality mid-bass applications. Faital Pro 6PR150
they sell an Eminence 500 Hz crossover which will work very well here:
Eminence pxb-500. The Eminence pxb-500 is a low pass crossover. The Eminence pxb-500 500Hz low pass crossover handles 400 watts RMS.
but of course get a real speaker first.
The one you have will die quick, serious.
What head will you use to drive this cabinet?
Or you are using a combo external speaker out?
*Really* , you should use that foam rotor straight with a 12"speaker , you'll end up with something similar to a Fender Vibratone.
Not bad at all and quite suited to guitar use:
Rear:
Front:
Side:
Leslie 16 Rotor Photo by Fastocker | Photobucket
JMFahey,
I bought the assembly from ebay. You're doing a good job talking me into a new speaker. I didn't realize the Vibratone used the same 15" rotor that I have. The nice thing about using another 12" 8 Ohm speaker is that I would only need an A/B switch. No need for a crossover. Nothing but swoosh. I like it. I wished I thought about this before I built my baffle and cabinet. But, this is something I'm going to seriously consider. I may end up using the current baffle and attaching a larger cabinet to the bottom.
I might try out the current crossover design for now and play with it. It seems like the fastest way to fun.
I'm not a gigging musician and use small wattage amps. I like everything to be modular. My current favorite is the AX84 4-4-0. It's a Trainwreck preamp coupled to a small output amp. This little guy sounds huge. It will make your ears ring running through a 12" speaker. I've attached the schematics. Everybody should build one.
I bought the assembly from ebay. You're doing a good job talking me into a new speaker. I didn't realize the Vibratone used the same 15" rotor that I have. The nice thing about using another 12" 8 Ohm speaker is that I would only need an A/B switch. No need for a crossover. Nothing but swoosh. I like it. I wished I thought about this before I built my baffle and cabinet. But, this is something I'm going to seriously consider. I may end up using the current baffle and attaching a larger cabinet to the bottom.
I might try out the current crossover design for now and play with it. It seems like the fastest way to fun.
I'm not a gigging musician and use small wattage amps. I like everything to be modular. My current favorite is the AX84 4-4-0. It's a Trainwreck preamp coupled to a small output amp. This little guy sounds huge. It will make your ears ring running through a 12" speaker. I've attached the schematics. Everybody should build one.
I know AX 84 and I'm a big fan 😀 , they sound killer and are a no nonsense Forum.
Just curious, how much did you pay for it?
Are those original Leslie/Fender spares or somebody is making the rotors for homebuilding?
Just curious, how much did you pay for it?
Are those original Leslie/Fender spares or somebody is making the rotors for homebuilding?
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Hi,
You don't understand parallel and series crossovers, it makes no difference.
In this case, both will be 4 ohm in the treble and 8 ohm in the bass.
However for a simple first order x/o, series is the better option.
The 4 ohm treble will receive twice the wattage of the 8ohm bass.
rgds, sreten.
Try the free TinaTi simulator to see what is going on.
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I have a pair of those Foam drum Leslies which I put in cabinets and use for guitar and keyboard.
I adapted in higher wattage 10" PA speakers and have no need for crossovers at all.
I increased the size of the speaker opening, leaving tabs for the drum axle support strap, and added a 6mm plywood ring to hold the speaker above the surface to clear the strap.
Pretty straightforward,
I adapted in higher wattage 10" PA speakers and have no need for crossovers at all.
I increased the size of the speaker opening, leaving tabs for the drum axle support strap, and added a 6mm plywood ring to hold the speaker above the surface to clear the strap.
Pretty straightforward,
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