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Need Some NHT Crossover Assistance, Please

Dr. Morbius

Dr. Morbius

I.N.T.E.R.O.C.I.T.O.R.
This is going to be fun. This is a crossover for an NHT Super Two. I'd like to replace the caps with something decent, yet affordable, such as Solen Fast Caps for the smaller two electrolytics. I've not come across capacitors like this yet, just caps with axial leads. I'm not quite sure how to approach this. :o

The resistors appear pretty straight forward. And the coils are staying put.

Any suggestions are welcome. Thank you in advance.

Values..
Small purple electrolytic: 5.5uF
Large purple electrolytic: 11uF
Small value green electrolytic: 165uF 100V
Large value green electrolytic: 200uF 100V

IMG_2121_zpsc096cde3.jpg


IMG_2130_zps08b60c60.jpg


IMG_2125_zpsbc1b8217.jpg
 
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Those are radial capacitors. I'd probably just use a decent Panasonic or such radial cap, but if you want to use an axial design, and assuming you have the room, you could bend it like this:
 

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I'm afraid I can't be of much assistance in terms of suggesting a good capacitor replacement but I will be very interested in hearing how the replacement capacitors change the sound. Frankly, I was expecting the XO board to look a little more...robust?
 
89grand said:
Those are radial capacitors. I'd probably just use a decent Panasonic or such radial cap, but if you want to use an axial design, and assuming you have the room, you could bend it like this:
Click to expand...
I'll probably have to use caps with axial leads as I'm not finding much selection, even on Mouser, for 200uF and 165uF caps.

My biggest concern is space. However, I could probably go ahead and use large caps and mount the damned PCB board onto the inside of the MDF cabinet instead of back on the plastic input terminal. I'm not too worried about voiding my warranty at this point.
 
CarnahanBB said:
I'm afraid I can't be of much assistance in terms of suggesting a good capacitor replacement but I will be very interested in hearing how the replacement capacitors change the sound. Frankly, I was expecting the XO board to look a little more...robust?
Click to expand...
The performance series was NHT's budget line. The Super Twos (Super Ones with a built-in passive 6.5" Peerless sub crossed over at 120 Hz.) had an MSRP of $750 in 1999/2000.

My guess is the sound will change for the better if the originals have drifted out of spec. If not, probably not much change.
 
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I'll bet you'll notice a difference especially if you replace those originals with a nice audio grade cap. The caps in the original crossover appear to be pretty standard fare.
 
CarnahanBB said:
I'll bet you'll notice a difference especially if you replace those originals with a nice audio grade cap. The caps in the original crossover appear to be pretty standard fare.
Click to expand...
I plan to replace the two purple ones with audio grade caps. The two large green ones would be too large and too expensive for audio grade replacements. They'll have to be electrolytics, but they'll be newer and will have tighter tolerances (5% vs. 10%).
 
CarnahanBB said:
I'll bet you'll notice a difference especially if you replace those originals with a nice audio grade cap. The caps in the original crossover appear to be pretty standard fare.
Click to expand...

Opinions vary for sure, but in my opinion, if two caps are of the same value, and measure as such, they should perform the same.
 
allsmith said:
Just curious as i have seen two polarized caps in series plus to plus to create a single non polarized cap before in a crossover.
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Interesting. These don't though. If you check the patterns on the underside of the PCB you will see they don't share any connections.
 
But....if you're only measuring the capacitance of a cap, you're not measuring all the things that can be measured.
 
PE has 200 uf axial npe's and you could use a 150uf and a 15uf in parallel for the 165uf. Not sure how big the 200 and 150's are, but there 100's are not very big at all.
 
allsmith said:
PE has 200 uf axial npe's and you could use a 150uf and a 15uf in parallel for the 165uf. Not sure how big the 200 and 150's are, but there 100's are not very big at all.
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I may go with Erse Audio caps. They no longer carry the good electrolytics with the 3% DF, but they have a 200 uF with a 6% DF ...

http://www.erseaudio.com/Products/NonPolarElectrolyticAll/ANP10C-05-200-0-PB

... a 150 uF with a 6% DF ...

http://www.erseaudio.com/Products/NonPolarElectrolyticAll/ANP10C-05-150-0-PB

... and a 15 uF with a 3% DF (some of the last of that batch)...

http://www.erseaudio.com/Products/NonPolarElectrolyticAll/ANP10A-05-15-0-PB

Plus they have an 11 uF Pulse-X in stock (and I've not seen any other 11 uF caps of this type) ...

http://www.erseaudio.com/Products/PulseXAll/MPX25-03-11-00

And I can use a 5.6 uF Pulse-X in place of the 5.5 electrolytic.

http://www.erseaudio.com/Products/PulseXAll/MPX25-03-5-60

I just hope I can seat these things on the board properly so they don't come loose or break off.
 
It looks like you're taking a very reasonable approach to this. I'd just like to point out that sometimes the ESR of the cap is used to lower the Q of the crossover knee and in these cases lower DF or ESR is not always better unless you also add a series resistor with the cap. Do you have a schematic for the crossover? This is usually not an issue if there is already a series R that is significantly higher (3X or more) than the ESR since the external R dominates. I do see that there are several resistors on the back of that crossover so you might be fine. Another advantage of lower ESR is less heating in the cap when driven hard.
 
Pete B said:
It looks like you're taking a very reasonable approach to this. I'd just like to point out that sometimes the ESR of the cap is used to lower the Q of the crossover knee and in these cases lower DF or ESR is not always better unless you also add a series resistor with the cap. Do you have a schematic for the crossover? This is usually not an issue if there is already a series R that is significantly higher (3X or more) than the ESR since the external R dominates. I do see that there are several resistors on the back of that crossover so you might be fine. Another advantage of lower ESR is less heating in the cap when driven hard.
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Unfortunately I don't have a schematic. Bill Bush was the designer at NHT at the time and that's about all I know. I'll take it on faith that there is a resistor in series somewhere along the signal path.

Before I order any components I plan to measure the resistors' values to make sure they are all within spec. If not I'll replace. I see they are rated as "J" or 5% tolerance. All of the resistors I find in DCM Timeframes and Timewindows are 10% so I usually replace them with something newer, tighter and better.

EDIT: From looking at the back side of the crossover it seems there is a 5.5ohm resistor in series with the 11uF capacitor. It also looks like there is a 3.3ohm resistor in series with the 5.5uF capacitor. I guess I'm good.
 
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