Retrofitting a tweeter switch

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Jarmin
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Retrofitting a tweeter switch

#1 Post by Jarmin » Wed Jul 15, 2020 3:36 am

Hi all

I have a chance to buy a Omni15 Tallboy however it is wired full range. Is it possible/easy to install a switch for the tweeters??

Many thanks in advance
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Grant Bunter
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Re: Retrofitting a tweeter switch

#2 Post by Grant Bunter » Wed Jul 15, 2020 4:30 am

Piece of cake.
Add a switch on the + line leading to the tweeter from the crossover board, and you can now turn it on and off.
It will cost you a couple of quid in parts and 10 minutes of your time if you can solder, wait up, 15 minutes, because you'll need to drill a hole somewhere for the switch
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Bill Fitzmaurice
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Re: Retrofitting a tweeter switch

#3 Post by Bill Fitzmaurice » Wed Jul 15, 2020 6:42 am

Grant Bunter wrote:
Wed Jul 15, 2020 4:30 am
Add a switch on the + line leading to the tweeter from the crossover board
Do not do that. The high pass filter must have a load, otherwise the amp could be damaged. A switch must be installed before the high pass filter, not after.

jimbo7
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Re: Retrofitting a tweeter switch

#4 Post by jimbo7 » Wed Jul 15, 2020 1:57 pm

Would a potentiometer work if it was grounded?
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Bill Fitzmaurice
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Re: Retrofitting a tweeter switch

#5 Post by Bill Fitzmaurice » Wed Jul 15, 2020 2:33 pm

No. It won't provide the constant impedance load that's required for the filter to function correctly. Use an LPad.

Grant Bunter
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Re: Retrofitting a tweeter switch

#6 Post by Grant Bunter » Wed Jul 15, 2020 3:32 pm

Bill Fitzmaurice wrote:
Wed Jul 15, 2020 6:42 am
Grant Bunter wrote:
Wed Jul 15, 2020 4:30 am
Add a switch on the + line leading to the tweeter from the crossover board
Do not do that. The high pass filter must have a load, otherwise the amp could be damaged. A switch must be installed before the high pass filter, not after.
With the Omni15TB being a three way box, doesn't the woofer LP filter, and a band pass filter provide sufficient load to the amp?
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Re: Retrofitting a tweeter switch

#7 Post by Bill Fitzmaurice » Wed Jul 15, 2020 3:50 pm

What happens when there's no load to any of the three filters is that the impedance seen by the amp within that filter pass band can go very low, even approaching zero.

tallevan
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Re: Retrofitting a tweeter switch

#8 Post by tallevan » Thu Jul 16, 2020 4:02 am

Also, keep in mind that if you install a simple switch (on the positive lead between the high pass filter and the input jack) to turn the tweeter on and off, the bandpass filter on the midrange is still in play.

So the midrange driver won't even attempt to reproduce the upper highs, because of the low-pass section of the bandpass filter used on the three-way version of the Omni Tallboy.

If this is what you want, fine. But if you wish to turn off the tweeter and allow to be midrange driver to take over the highs as best it can (like the two-way version of the Omni Tallboy) Bill has designed the bandpass filter for the midrange in two sections, which could allow you to use a dpdt switch to turn off the tweeter AND bypass the low-pass section of the midrange bandpass filter.

I suspect this it what Bill intended all along, though he doesn't mention it specifically.

If you like, I'll post a wiring diagram when I get a few minutes.

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Bill Fitzmaurice
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Re: Retrofitting a tweeter switch

#9 Post by Bill Fitzmaurice » Thu Jul 16, 2020 6:51 am

I didn't put a switch into the mix because the LPad is far more useful.

tallevan
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Re: Retrofitting a tweeter switch

#10 Post by tallevan » Thu Jul 16, 2020 7:47 am

<the LPad is far more useful>

It is, too.

I put both switch and LPad in my Omni Tallboy 12, thinking that switching to two-way mode (no tweeter) would sound better when using distortion.
How often do I actually use distortion? Never.
How often do I turn down the LPad? Never. Even with the rudimentry passive EQ setions I use.

If I build one again, it will be without LPad and switch.
Even with flats, I strongly prefer the slight click the tweeter provides.

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