Using twin voice coils.

[awkwardbydesign]

My Jordan JX125s have 2 voice coils, but I'm only using one at the moment, making it a 12ohm speaker. Is there any reason why I can't connect the 2nd coil via an suitable inductor to give a 3dB boost below 400Hz? Lazy man's baffle step compensation? A temporary solution until I make new cabs and put the BSC into the electronics. My active system has gone, so I am running just 2 drivers for now. Of course I would make sure I connected it the right way round!

 

[i_should_coco]

Why don't you try it and let us know? :dunno:

 

[steve 57]

The only way you will get a volume improvement is if there is another amp driving it, but then you have the issue of phase which is is likely to do more damage to the sound than good, but you never know of course

my experence has show the more radiating area will give the best resultswhen it comes to bass, otherwise ohms law comes into play where you addeth and taketh away works out to leave you with the same thing

but go with pete and give it a try

Clipleads are good when it comes to messing like this

 

[steve 57]

Been thinking about this one.. i suspect it is likely that the signal passing throught the inductor will have an amount of phase shift, this is not the end of the world with seperate drivers but when that signal is in the second voice coil is likely to be out of phase with the 'full range' signal if thats the right description.. And that makes sense

the speaker will then move to the sum of the signal which is almost certainly going to take something away from the original signal...

Cheers

 

[awkwardbydesign]

Why don't you try it and let us know? :dunno:

:doh:

 

[awkwardbydesign]

Been thinking about this one.. i suspect it is likely that the signal passing throught the inductor will have an amount of phase shift, this is not the end of the world with seperate drivers but when that signal is in the second voice coil is likely to be out of phase with the 'full range' signal if thats the right description.. And that makes sensethe speaker will then move to the sum of the signal which is almost certainly going to take something away from the original signal...

Cheers

Would the out of phase aspect cause overheating in the coils? The crossover at 3kHz is 2nd order, so 180 degree shift at that point, and the BSC is 1st order at 400Hz, so 90 degrees there. I imagine I would feed the BSC coil from before the crossover to avoid affecting the normal crossover. I don't mind losing some volume, as this is a temporary solution. Eventually I will have to get my head round a crossover program, and get rid of the 6kHz spike, 2kHz plateau, etc. I've added a zobel for now, as the resistance at 3kHz was 36 ohms, and rising. These drivers (Jordan JX125 and JXR6HD) are quite transparent if implemented well. Anyway, I already have them, and having just spent £2750 on pre, power and CDP I cannot spend any more until I sell.

 

[awkwardbydesign]

The other alternative is to cross over at 400Hz, and adjust levels to suit. That means bigger caps and inductors plus reduced power handling. I may well do that later, and make MLTL or TQWT cabs for the bass. I like the shape of the Frugalhorns, but with the exit underneath. It could then be tuned by leg length.

.

 

[steve 57]

Thats an interesting set up, if i have it right you have two frugal horns per channel one playing bass..the other doing the mids/ top end..

I'm familiar with frugal horns but only full range types, scott lives around the corner to me and they are impressive for what they are

i had to look at your pics a few times

the bass drivers you are using are recommended to use a 1st order, which in my experience tends to give the best results with full range type drivers. I cant really comment on the voice coils if they are likely to overheat, as to removing the bottom you would be removing the horn element of the design, i would email scott on the frugal horn website and explain exactly what you are trying to achieve, he may be able to help..

 

[awkwardbydesign]

Ah, a bit of a misunderstanding here! The JX125s would be in a TQWT cabinet similar to a frugal horn. As I understand it, there are no designs available for a 6.5" driver, so I will have to calculate my own; which I have just done. The tweeter will be in a box or on an open baffle sat on top, rather like a supertweeter. I have a pair of Shackman electrostatic panels in the loft which I want to try again, so the tweeter has to be in a separate housing.

If there is a frugal horn design for the Jordan JX125s, I would be more than happy to use it.

 

[steve 57]

Sorry about that i saw the picture with the different drivers... I'm easily fooled..

cheers...

 

[Tenson]

I agree with Steve, the inductor would cause phase shift on the second coil signal meaning it won't sum well in the transition band of the filter with the main signal.

Dual coils are something I've never played with but I think the main advantage is being able to use one of the coils as a feedback signal from the driver so you can make a servo drive reducing distortion.

 

[awkwardbydesign]

What I have done in the end is cross over at 480 Hz, which matches the baffle width for BSC. The JX6 is 3dB down on the JX125, so it may work. I haven't smoothed the JX125's response yet, so watch this space.....