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NCBlueTJ

Heresy Tweeter Mod

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Hi,

Been reading the forum for a while, but this is my

first post. I bought some 1978 Heresy I 's off of ebay

recently. I did the recomended rope caulk and box reinforcement

tweaks with very good results. I am really really enjoying these

new speakers. However, I have noticed the brightness on the

tweeter and have read several posts discussing how to remedy the

problem. I can't seem to get a direct answer using the search

feature , so I decided to just post my question.

What is the prefered way to lower the output of the

tweeter? I have heard moving it from tap 3 to tap 2 on the

autoformer as well as other methods (wiring a resistor in

parrallel?) What are the different ways commonly used to

accomplish this and which way is best? Thanks in advance for your

help.

System:

1978 Heresy I 's

AMC CVT 2030 (30wpc PP tube amp)

Carver preamp (1980's?)

Toshiba DVD player

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NCBlue..

FIrst off, welcome to the forum!

I think, given the simplicity of the netwrok in the Heresy I, I would just get an 8 Ohm adjustable L-Pad and put it in the lead going from the network to the tweeter. Mount it so the knob stocks out the back. Just adjust it to where you like it. Moving the tap on the transformer will seem to work, but it messes up other things. The L-Pad is the "safe" way to do it.

AL K.

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Here was my solution, a new reinforced back panel with L-pads. The original backs are safely stored away.

post-12829-1381928125576_thumb.jpg

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Or you could get a pair of tweeter attenuators/transformers from Al K. That's not the cheapest way, but it does sound better than an L-pad. It's MUCH easier to balance the proper tweeter levels--both with reference to the midrange and woofer and with reference to the other speaker--with Al's tweeter attenuator than with an L-pad. Unless you cut holes in your speakers, which many of us just aren't going to do, consider the process of opening up the back, making an adjustment, closing the back, making the wiring connection, listening to the speaker and trying to figure out if the tweeter is too loud or too soft, and then opening the back again to fine tune the L-pad, and then doing it all over again and again until you get the balance "correct" for that speaker, and then doing it all over again (and again) for the other speaker, only to find that one tweeter is slightly louder than the other. It's easier with Al's attenuator, believe me.

Al K isn't giving you bad advice; the L-pads sound fine when and if you get them dialed in correctly. Al is just looking out for your wallet, bless his heart. For me, though, avoiding either cutting holes in my speakers or the frustration of trying to balance both speaker levels was more than worth the difference in the cost of Al's attenuators versus a pair of decent L-pads. Not only that, but the attenuators really do sound better, and I don't think I'll get an argument about that from Al.

Don't misunderstand me: the L-pads don't sound bad at all; it's just that the tweeter attenuators sound better. It's your money, though, your speakers, and your choice.

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The transformer attenuators are a better way to go, but they will be hell to adjust since they require a plug to be moved rather than just turning a knob. Mounting them outside the box require that wires be run through the back. Sealing the holes air tight won't be easy and they could easily be damaged hanging off the back too.

Al K.

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Put a 15 ohm resistor in parallel with squawker, you can screw it right to the + - spots on barrier strip for the squawker. Then move the tweeter from tap 2 to tap 1, and the squawker from tap 3 to tap 2. This lowers the midrange and treble by 3dB which brings the bass up and makes the speaker sound much more balanced. The 15 ohm resistor means you don't have to change the primary capacitor value. IWOs, it keeps the crossover points the same.

Best way: 11 ohm resistor across taps 0 and 5, and change the primary cap from 2uF to 21uF. Then drop the tap settings as already mentioned.

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I didn't mean to give the impression that I was talking about putting the attenuators outside the cabinet. Sorry for the misunderstanding and confusion. I put mine inside the cabinets, and I opened and closed each speaker just once to adjust and install the attenuator. There are a "limited" number of choices with the ALK attenuator because there are a limited number of taps, even though the attenuator is more adjustable than you would need it to be with just about any tweeter.

Realistically, with a K-77-M tweeter, there are only two relevant choices on the ALK attenuator: -3 dB and -5 dB, and even with those two choices you're never more than 1 dB away from a "perfect" setting. I can't believe that a Heresy tweeter would be more out of balance than +5 dB, so you wouldn't really need the -7 dB or -9 dB settings on the attenuator, although they're there if you ever need them for a different tweeter. The -3 dB tap on the attenuator is probably the one to start with and most likely will do the trick. If not, the -5dB tap is the one. In the absolute worst case, you've opened and closed the backs of ONE of your speakers only twice. When you've decided on the balance for one side, then you just use the same setting for the attenuator on the other speaker, which automatically balances both speakers. It really is easy and idiot-proof--which is what I needed. For me it was much easier to do it the way I did than to cut a hole in the back of the speaker.

For someone like me who has no mikes, analyzing instruments, etc., and has to judge settings by ear, fewer choices means fewer chances to make mistakes. Infinite choices, such as a stepless L-pad, means, for me, a lot of frustration while I'm fighting through an infinite number of ways to get it wrong. I've tried both, and I never felt confident that I had it right with the L-pads. With Al's attenuators I know I got the tweeter levels correctly balanced; it was simple and quick, and my tweeters sound more lifelike now.

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Guys,

I really appreciate all the advice. It sounds

like the ALK attenuators are the way to go, Too bad, I was

looking for an "almost free" switching the taps type mod. Oh

well, guess this will have to wait for a while, the Heresey's ate up

all my stereo budget for the time being. At least I'm enjoying

them so much right now.

Lee

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On 2/2/2006 at 7:45 AM, Deang said:

Put a 15 ohm resistor in parallel with squawker, you can screw it right to the + - spots on barrier strip for the squawker. Then move the tweeter from tap 2 to tap 1, and the squawker from tap 3 to tap 2. This lowers the midrange and treble by 3dB which brings the bass up and makes the speaker sound much more balanced. The 15 ohm resistor means you don't have to change the primary capacitor value. IWOs, it keeps the crossover points the same.

Best way: 11 ohm resistor across taps 0 and 5, and change the primary cap from 2uF to 21uF. Then drop the tap settings as already mentioned.

Hi, does this apply to E-2 crossover ? I have a pair of Heresy I from 85...

when u say primary cap, you mean the one before the Autoformer? 

Do you still add the 15ohm if you add the 11ohm and change from 2uF to 21uF
Thx.

DA90E963-F862-4996-BD5B-96C517E58121.webp

Edited by Maxx

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3 hours ago, Maxx said:

Hi, does this apply to E-2 crossover ? I have a pair of Heresy I from 85...

 

Yes...works with E or E-2

 

3 hours ago, Maxx said:

when u say primary cap, you mean the one before the Autoformer? 

 

Yep.

 

3 hours ago, Maxx said:

Do you still add the 15ohm if you add the 11ohm and change from 2uF to 21uF

DA90E963-F862-4996-BD5B-96C517E58121.webp 5.14 kB · 1 download

 

No, the 15 ohm resistor should not be added if you are going with the 11 ohm shunt resistor/21uf primary cap.

 

Mike

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5 hours ago, mboxler said:

 

Yes...works with E or E-2

 

 

Yep.

 

 

No, the 15 ohm resistor should not be added if you are going with the 11 ohm shunt resistor/21uf primary cap.

 

Mike

Ok. So is this way best for a particular reason as opposed to adding the 15 Ohm resistor and doing the tap swaps... and leaving the cap values the same...?

 

Ps; for the 11 Ohm and 21uF, I only have a 12 Ohm resistor and 20 uF cap.. is this ok?

 

Thx.

Edited by Maxx

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16 minutes ago, Maxx said:

Ok. So is this way best for a particular reason as opposed to adding the 15 Ohm resistor and doing the tap swaps... and leaving the cap values the same...?

 

Ps; for the 11 Ohm and 21uF, I only have a 12 Ohm resistor and 20 uF cap.. is this ok?

 

Thx.

 

The difference between the two approaches is the load on the amp.  If you look at a Heresy impedance curve, it soars to 72 ohms.  If that's okay, than the 15 ohm resistor across the squawker (and I'd add an 8 ohm across the tweeter as well) will keep that same curve.

 

The 21uf cap/11 ohm resistor method will lower that curve to around 10 ohms...a flatter curve.

 

The 20uf cap and 12 ohm resistor you have should work just fine.  The impedance curve will flatten to around 11 ohms, so a lower value capacitor would be needed anyway.

 

Mike

 

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12 minutes ago, mboxler said:

 

The difference between the two approaches is the load on the amp.  If you look at a Heresy impedance curve, it soars to 72 ohms.  If that's okay, than the 15 ohm resistor across the squawker (and I'd add an 8 ohm across the tweeter as well) will keep that same curve.

 

The 21uf cap/11 ohm resistor method will lower that curve to around 10 ohms...a flatter curve.

 

The 20uf cap and 12 ohm resistor you have should work just fine.  The impedance curve will flatten to around 11 ohms, so a lower value capacitor would be needed anyway.

 

Mike

 

Ok thx 

i have some 15uf, 18uf caps 

would going lower be better? I’m assuming we need to get closer to 8ohm? Right?

thx for all your help..

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3 minutes ago, Maxx said:

Ok thx 

i have some 15uf, 18uf caps 

would going lower be better? I’m assuming we need to get closer to 8ohm? Right?

thx for all your help..

 

If you want to get to around 8 ohm, you would need a 9 ohm resistor across taps 0 - 5 and larger capacitors (around 27 uf).

 

Unless you really want an 8 ohm load, I'd stay with the 20uf cap and 12 ohm resistor you have and see how you like it. 

 

Mike 

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1 hour ago, mboxler said:

 

If you want to get to around 8 ohm, you would need a 9 ohm resistor across taps 0 - 5 and larger capacitors (around 27 uf).

 

Unless you really want an 8 ohm load, I'd stay with the 20uf cap and 12 ohm resistor you have and see how you like it. 

 

Mike 

Hi,

well my amp is 4 or 8 ohm 

I’m not sure if this is relevant.

What do u think?

 

thx 

 

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1 hour ago, Maxx said:

Hi,

well my amp is 4 or 8 ohm 

I’m not sure if this is relevant.

What do u think?

 

thx 

 

 

No matter what you do, the impedance curve will never be flat.  If your amp worked okay driving the stock Heresy using the 8 ohm outputs then it should be fine with the 20uf cap and 12 ohm resistor.   

 

Oh.  I assume the 33uf capacitor is the original electrolytic bipolar.  At 35 years old it's probably time to replace.

 

Mike

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1 hour ago, mboxler said:

 

No matter what you do, the impedance curve will never be flat.  If your amp worked okay driving the stock Heresy using the 8 ohm outputs then it should be fine with the 20uf cap and 12 ohm resistor.   

 

Oh.  I assume the 33uf capacitor is the original electrolytic bipolar.  At 35 years old it's probably time to replace.

 

Mike

Ok 

yes I have a 33uF Bi Polar electrolytic 

i also have a 33uf Mkp 

Any advantage to using the Mkp instead ?

thx

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7 minutes ago, Maxx said:

Ok 

yes I have a 33uF Bi Polar electrolytic 

i also have a 33uf Mkp 

Any advantage to using the Mkp instead ?

thx

 

The electrolytic is fine, since it is in a shunt position across the woofer.  I'm sure it's a lot smaller too!

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1 hour ago, mboxler said:

 

The electrolytic is fine, since it is in a shunt position across the woofer.  I'm sure it's a lot smaller too!

Ok thx 

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