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AR9LS "i" crossover upgrade?


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Hey all,

I've searched high and low and after downloading all the schematics I could find it looks like I need 1 x 1.5 ohm @ 22 watt and 1 x 2.5 ohm @ 22 watt resistors to make this upgrade? I'm no electrician so maybe I'm missing something here but IF these are the correct resistors they seem awful hard to find!

Was hoping someone having familiarity with this specific upgrade might be able to verify these resistors and perhaps offer a site to buy them or suggest an available alternative?

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I've searched high and low and after downloading all the schematics I could find it looks like I need 1 x 1.5 ohm @ 22 watt and 1 x 2.5 ohm @ 22 watt resistors to make this upgrade? I'm no electrician so maybe I'm missing something here but IF these are the correct resistors they seem awful hard to find!

You don't have to get the wattage (power handling) exactly right. Newark sells a 1.5Ohm 55w resistor for about $12 (Ohmite brand, expensive). Once I found that one I didn't "shop" for you - I just wanted to be sure someone was making resistors in that range - so I have no clue if there is also a 2.5 Ohm version, but anything from 20-55w should be fine.

If you have no luck, don't give-up hope. Come back and report that you've had no luck.

Bret

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You don't have to get the wattage (power handling) exactly right. Newark sells a 1.5Ohm 55w resistor for about $12 (Ohmite brand, expensive). Once I found that one I didn't "shop" for you - I just wanted to be sure someone was making resistors in that range - so I have no clue if there is also a 2.5 Ohm version, but anything from 20-55w should be fine.

If you have no luck, don't give-up hope. Come back and report that you've had no luck.

Bret

Thanks for the quick reply and the bit of searching Bret!

I see Newark also sells a 1.5 Ohm @ 25 watts. I'm reasonably sure I should be able to find a 2.5 also within the range you have specified. Should I be concerned about a particular type of resistor? I see "film", "sand", "ceramic", "wire wound", etc. If they all the have the values I'm looking for how do I decide between the "types"?

Thanks again,

Jon

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  • 5 months later...
Thanks for the quick reply and the bit of searching Bret!

I see Newark also sells a 1.5 Ohm @ 25 watts. I'm reasonably sure I should be able to find a 2.5 also within the range you have specified. Should I be concerned about a particular type of resistor? I see "film", "sand", "ceramic", "wire wound", etc. If they all the have the values I'm looking for how do I decide between the "types"?

Thanks again,

Jon

I realize this is an old post. All I could easily find were the 1.5 and 1 ohm 25 watt wirewound resistors so I used them in series for my 2.5 ohm resistor, I hope that I did not do anything wrong considering how sensitive crossovers can be. Feel free to correct me if I did a no-no! ;)

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  • 11 years later...

Resurrecting this thread, since I am working 9LS speakers. I have some questions for the crossover experts. On the woofer and LMR shunt caps, there is a 0.5 ohm resistor. That small value in the scheme of things seems almost negligible, so what is its purpose? 

The next question, is not only are 1.5 ohm and 2.5 ohm resistors added in to attenuate the LMR and UMR, but the polarity of the tweeter is reversed, as well as the 5uF cap right before the tweeter + terminal (ls crossover) is eliminated. Why reverse the polarity on the improved, and why get rid of that cap? 

Im interested in finding out these answers, because I am planning on implementing a LS/LSI switch, to accomplish adding or the 1.5ohm and 2.5 ohm resistors, and also shorting the 5uF tweeter cap when LSi is selected, and of course the opposite when LS is selected. Easily implemented with a 3 pole single throw switch. However, reversing the tweeter polarity wouldn't be possible without another two poles or an additional switch, which id like to avoid. Do you folks think reversing the tweeter polarity would be necessary when using the LSi circuit?

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OK, revisiting with some clearer thoughts. I have 4 pole switches coming to use as an LS/LSi selector. Poles used as follows: one pole to switch in or out the 1.5 ohm LMR resistor, one pole to switch in or out the 2.5 ohm UMR resistor, and the the last two poles to reverse the tweeter polarity as well as bypass the 5uF cap when LSi is selected. 

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On 1/9/2021 at 1:45 AM, Chris1this1 said:

Resurrecting this thread, since I am working 9LS speakers. I have some questions for the crossover experts. On the woofer and LMR shunt caps, there is a 0.5 ohm resistor. That small value in the scheme of things seems almost negligible, so what is its purpose? 

The next question, is not only are 1.5 ohm and 2.5 ohm resistors added in to attenuate the LMR and UMR, but the polarity of the tweeter is reversed, as well as the 5uF cap right before the tweeter + terminal (ls crossover) is eliminated. Why reverse the polarity on the improved, and why get rid of that cap? 

Im interested in finding out these answers, because I am planning on implementing a LS/LSI switch, to accomplish adding or the 1.5ohm and 2.5 ohm resistors, and also shorting the 5uF tweeter cap when LSi is selected, and of course the opposite when LS is selected. Easily implemented with a 3 pole single throw switch. However, reversing the tweeter polarity wouldn't be possible without another two poles or an additional switch, which id like to avoid. Do you folks think reversing the tweeter polarity would be necessary when using the LSi circuit?

The 0.5 Ohm resistors change the damping of the filter cells and must not be removed!

The polarity reversal for the tweeter connections depends on the fact that the high pass filter is of the third electrical order for the AR-9LS while it is of the second electrical order for the AR-9LSI. So, if you change the filter you must also change the polarity unless you can verify the result with appropriate FR measurements.

The crossover changes made by the AR engineers in the AR-9LSI crossover are very "minor". The AR-9LSI used the "new" Tonegen drivers and the small changes in the LSI crossover were most likely made primarily to handle the small sensitivity an FR differences of the new drivers compared to the old ones. So, my personal advice if your speakers have the original (made in USA) drivers (tweeter-midrange and lower midrange), is not to modify the original crossover. If these small changes had led to any improvements, you can rest assured that AR engineers would have done them long before the introduction of the 9LSI as any advanced hobbyist would!

In any case, I would not be surprised at all if most audiophiles would say, due to the "improved" suggestion, that the 9LS sounds better with the 9LSI crossover...😀!

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On 1/8/2021 at 7:45 PM, Chris1this1 said:

On the woofer and LMR shunt caps, there is a 0.5 ohm resistor.

So you have the resistors? When I built some AR-3a crossovers from scratch the xo schematic in the restoration guide showed a 0.51 Ohm 20w resistor. That was actually a bit of nichrome wire in the 3a's. I used two 1 Ohm 10w resistors in parallel.

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1 hour ago, fedeleluigi said:

In any case, I would not be surprised at all if most audiophiles would say, due to the "improved" suggestion, that the 9LS sounds better with the 9LSI crossover...

In my case the LS model was unbearable without abnormal equalizer adjustments.  After the "I" installation the equalizer was not needed.  No auto suggestion involved.

Adams

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I own the 98Ls, 98Lsi & 9Lsi.  As I stated in a previous post, sometimes I can hear a slight harshness/brightness in the upper midrange of the 98Ls that is not present in either the 98Lsi or the 9Lsi.  Richard Heyser also noted this in Audio magazine’s January 1985 review of the 98Ls, stating that “on some material, the upper midrange has, to me, a ‘fizzy’ characteristic that gives a somewhat exaggerated brightness.”   In High Fidelity magazine’s review of the 9Ls they stated that “some members of our panel report hearing what might be described as a tinge of hotness on some high-frequency material (for which we have no ready explanation).”

The only other fault that Richard Heyser found with the 98Ls was the negative impact of the speaker grille.

It is interesting to note that when AR released the updated 98Lsi in late 1985, the 2 most notable changes that AR made to the 98Lsi was a redesign of the crossover and the grille.  Yes, they had outsourced the drivers, including the tweeter/upper midrange assembly, to Tonegen but I don’t believe that they had much of impact on the sound.  I have switched out the LM and woofer of the one of my 98Ls’ with Tonegen drivers and I didn’t notice any significant difference in the sound when compared to the 98Ls with the original drivers.  The occasional harshness/brightness was still noticeable in the 98Ls with the Tonegen drivers.

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The published performance for a 98LS is -3db @ 39hz and -3db @ 32000hz, so plenty of room for a hump in the mid range. I haven't seen anything published for the LSi.

Edit: LSi published spec is identical and can be found here http://www.classicspeakerpages.net/library/acoustic_research/special_sections/ar_uk_related_information/brochures/ar_uk_bxi_lsi_brochure/

 

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.....any case, I would not be surprised at all if most audiophiles would say, due to the "improved" suggestion, that the 9LS sounds better with the 9LSI crossover...😀!

Luigi.....i owned both.  There is no comparison in sound quality.  I get your point on audiophiles, but in this case its a dramatic difference.

In fact i run a touch more resistor on middome in mine.

I think Adams stated the LSI mod puts it about even with a AR9 in output......yep..he is right. Without the mod, its ridiculous..  Its flat harsh in LS form.

I dont care if they wired it in 7 loops, its better.

 

 

 

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On 1/15/2021 at 9:36 AM, AR55 said:

I own the 98Ls, 98Lsi & 9Lsi.  As I stated in a previous post, sometimes I can hear a slight harshness/brightness in the upper midrange of the 98Ls that is not present in either the 98Lsi or the 9Lsi.  Richard Heyser also noted this in Audio magazine’s January 1985 review of the 98Ls, stating that “on some material, the upper midrange has, to me, a ‘fizzy’ characteristic that gives a somewhat exaggerated brightness.”   In High Fidelity magazine’s review of the 9Ls they stated that “some members of our panel report hearing what might be described as a tinge of hotness on some high-frequency material (for which we have no ready explanation).”

The only other fault that Richard Heyser found with the 98Ls was the negative impact of the speaker grille.

It is interesting to note that when AR released the updated 98Lsi in late 1985, the 2 most notable changes that AR made to the 98Lsi was a redesign of the crossover and the grille.  Yes, they had outsourced the drivers, including the tweeter/upper midrange assembly, to Tonegen but I don’t believe that they had much of impact on the sound.  I have switched out the LM and woofer of the one of my 98Ls’ with Tonegen drivers and I didn’t notice any significant difference in the sound when compared to the 98Ls with the original drivers.  The occasional harshness/brightness was still noticeable in the 98Ls with the Tonegen drivers.

AR55

I looked up that review.  He was pretty spot on, especially in the Bass 

I personally cant take the 98 ls,9ls  without adding resistence to the mid dome.   Love it after i put 3 ohms to it.   

Glad to see 9lsi owners out here.    

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