LP-12 Naim Aro Owners Please Read

[graham55]

However lovely the DVXX-2 sounds, the fact of the matter is that, as the Aro does not have headshell slots, it will only be perfectly asligned with a cartridge which has the bolt-hole-to-stylus distance assumed by the Aro designers.

Regards,

Andy

Well, I believe that it does, not that my music is suffering!

 

[John]

Well, I believe that it does, not that my music is suffering!

Here's a Linn Arc Protractor that works perfectly with a Linn Ekos and Linn MC. You can try it with your setup to see how close you come out. I cut the box around the spindle with an razor knife. I'm looking spot on with my setup!

 

[Nik]

We may never know as Linn is unable to share that information. I have confirmed 7.1mm for the Arkiv and can only assume that the bolt to stylus is 7.1mm for the Troika and other Linn MC's as well. The 7mm is one I've seen bandied about for years. On the Ekos, the Troika is more towards the front of the slotted headshell, I assume that is because 7mm is at the short end of the range for bolt to stylus measurements. The extra slot room at the back of the headshell I assume is to accommodate for longer cartridges. So if the Aro and Ekos have the same geometry as some claim, then 7mm is ideal for an Aro and anything else, given the 211mm pivot to spindle spec, is not.

Yes, 7.1 seems likely for all 3 and it's also close to the 7 mm that's been mentioned a few times. My Arkiv is also close to the front of the slots and, as you say, that's what you would expect with 7 mm being at the short end; it looks like about 5 mm would be the shortest possible.

I don't know if anyone has claimed that the Aro and Ekos have the same geometry but I have certainly suggested that it seems extremely likely, given that they were both designed for the Troika with its third bolt. The spec for the Ekos (and every other Linn arm except the 12" Ittok) also exactly matches the original Aro spec at 229/211/24. The only thing that casts doubt on this is the pivot-to-outer-bolt distance for the Aro, which is incompatible with the combination of a 229 effective length, 24 offset, and 7.1 cartridge measurement.

 

[Nik]

Here's a Linn Arc Protractor that works perfectly with a Linn Ekos and Linn MC. You can try it with your setup to see how close you come out. I cut the box around the spindle with an razor knife. I'm looking spot on with my setup!

That looks good. JaS is, of course, responsible for Vinyl Engine's tonearm alignment calculators. The figures on the protractor will be useful too.

Cutting the spindle hole exactly is crucial. I'll give it a try tomorrow.

 

[flatpopely]

So can I just summarise this thread:-

1. NAIM published some specs on their website about the ARO that were wrong.
2. These specs have been used by some but not all manufacturers of subchassis accomodating the ARO.
3. The correct specs are available from NAIM if one asks for them.

I think that about covers it.

 

[sq225917]

That could be nicely summed up thus.

Cheats never prosper...!

 

[John]

My impression is that the published Naim specs [Effective length 230mm, Overhang 18mm, Cartridge weight 5.5–12gm, Pivot centre to platter centre 212.5mm] are correct and there appears to be an attempt to protect these so-called Linn/Naim specs that I can only guess were used with the Aro Keel and Aro Rubikon.

The Naim specs above have been published for years in Naim brochures, Naim's website, official Naim sactioned reviews of their products, as well as The Vinyl Engine website which has become a repository for turntable, tonearm and cartridge specs. The published Naim specs have also been used by DPS and Phonosophie, two turntable manufacturers who have been long proponents of using the Aro tonearm.

 

[John]

Yes, 7.1 seems likely for all 3 and it's also close to the 7 mm that's been mentioned a few times. My Arkiv is also close to the front of the slots and, as you say, that's what you would expect with 7 mm being at the short end; it looks like about 5 mm would be the shortest possible.

I don't know if anyone has claimed that the Aro and Ekos have the same geometry but I have certainly suggested that it seems extremely likely, given that they were both designed for the Troika with its third bolt. The spec for the Ekos (and every other Linn arm except the 12" Ittok) also exactly matches the original Aro spec at 229/211/24. The only thing that casts doubt on this is the pivot-to-outer-bolt distance for the Aro, which is incompatible with the combination of a 229 effective length, 24 offset, and 7.1 cartridge measurement.

I agree, something smells fishy.

 

[Nik]

So can I just summarise this thread:-

1. NAIM published some specs on their website about the ARO that were wrong.
2. These specs have been used by some but not all manufacturers of subchassis accomodating the ARO.
3. The correct specs are available from NAIM if one asks for them.

I think that about covers it.

If Naim will supply the correct specs on request, why don't they put those same correct specs on their own website? What is the matter with them?

 

[John]

If Naim will supply the correct specs on request, why don't they put those same correct specs on their own website? What is the matter with them?

Let's not forget this post from someone with the original Aro drawings:

A look at the Aro drawings shows that the spec on Drawing No. 310/3 was Pivot centre to Platter centre distance of 212.5mm (230mm effective length). On Drawing No. 310/4 (i.e. later revision) the same dimension is 211mm +/-1.5mm (effective length 229mm). I guess it was decided to make allowance for the adjustability of the Linn armboard?


http://www.pinkfishmedia.net/forum/showpost.php?p=1396602&postcount=130

 

[Nik]

Let's not forget this post from someone with the original Aro drawings:

A look at the Aro drawings shows that the spec on Drawing No. 310/3 was Pivot centre to Platter centre distance of 212.5mm (230mm effective length). On Drawing No. 310/4 (i.e. later revision) the same dimension is 211mm +/-1.5mm (effective length 229mm). I guess it was decided to make allowance for the adjustability of the Linn armboard?


http://www.pinkfishmedia.net/forum/showpost.php?p=1396602&postcount=130

Maybe, but it seems odd to place the original figure at the limit of the tolerance on the new one.

 

[John]

Maybe, but it seems odd to place the original figure at the limit of the tolerance on the new one.

If one used the original Naim spec with a newer LP12 plinth, the Aro would hit the corner brace. Using the original spec requires that part of the corner brace be removed, just as you would have to do with a Rega tonearm. I guess it's too much work to expect of a dealer.

So assuming the original spec is correct and using the 224.5 outer cartridge bolt to pivot measurement, what cartridge is ideal for that setup?

 

[John]

Might as well put it all together:-
7 mm: effective length 228.15, Baerwald 209.94, Löfgren B 209.42, offset 24.2
8 mm: effective length 229.04, Baerwald 210.91, Löfgren B 210.39, offset 24.1
8.5mm: effective length 229.49, Baerwald 211.39, Löfgren B 210.88, offset 24.0
9.6 mm: effective length 230.5, Baerwald 212.49, Löfgren B 211.98, offset 23.9
10 mm: effective length 230.84, Baerwald 212.86, Löfgren B 212.35, offset 23.9

If one used the original Naim spec with a newer LP12 plinth, the Aro would hit the corner brace. Using the original spec requires that part of the corner brace be removed, just as you would have to do with a Rega tonearm. I guess it's too much work to expect of a dealer.

So assuming the original spec is correct and using the 224.5 outer cartridge bolt to pivot measurement, what cartridge is ideal for that setup?

I suppose an estimate for the ideal cartridge bolt to stylus distance given a 230mm effective length the number would be somewhere between 8.5 and 9.6mm.

 

[Nik]

If one used the original Naim spec with a newer LP12 plinth, the Aro would hit the corner brace. Using the original spec requires that part of the corner brace be removed, just as you would have to do with a Rega tonearm. I guess it's too much work to expect of a dealer.

Yes, as described at the GreenStreet site.

So assuming the original spec is correct and using the 224.5 outer cartridge bolt to pivot measurement, what cartridge is ideal for that setup?

For the 3 quoted effective lengths, and assuming an offset of exactly 24 for all, the stylus-to-bolt distances are:-
229 7.952
230 9.067
230.5 9.625

 

[John]

OK, let's assume the original specs for the Naim Aro are correct: Effective length 230mm, Overhang 18mm, Cartridge weight 5.5–12gm, Pivot centre to platter centre 212.5mm.

Now if one was to mount the Aro with a 211mm pivot to spindle spec using a 7mm cartridge keeping in mind the effective length should be 230 and not 229mm. What would be the distortion measurements for that setup versus say the original specs with that same 7mm cartridge?

 

[Nik]

OK, let's assume the original specs for the Naim Aro are correct: Effective length 230mm, Overhang 18mm, Cartridge weight 5.5–12gm, Pivot centre to platter centre 212.5mm.

Straight away we have a problem. If you have an effective length of 230, you can't have an overhang of 18 with a pivot-spindle of 212.5. You can have:-
212 + 18 = 230
212.5 + 17.5 = 230
212.5 + 18 = 230.5
(or some other figures that add up.)

Now if one was to mount the Aro with a 211mm pivot to spindle spec using a 7mm cartridge keeping in mind the effective length should be 230 and not 229mm. What would be the distortion measurements for that setup versus say the original specs with that same 7mm cartridge?

Once we've decided on the right starting point, we can use the VE calculators for the rest. I think Paul R already covered this.

 

[John]

Once we've decided on the right starting point, we can use the VE calculators for the rest. I think Paul R already covered this.

But Paul R was assuming an effective length of 229 with the Aro, not the original spec of 230mm. Does that not alter the results?