Revisiting Jim Rogers JR149s

[Tony L]

The replica mk1 foams have 33mm wide 'bars' and 10mm wide 'spaces'. Also, I thought the mk1 foams were 10mm thick but they're actually 12mm thick (12mm at the 'bar' sections and 6mm at the 'space' sections).

I am just crazy OCD about this sort of thing and I came to the conclusion from studying original pictures that there is one more bar than that, i.e. there should be an odd number so one bar runs centrally over the logo/tweeter. Here’s my attempt:

I suspect this is very close indeed, but I also suspect JR used imperial measurements as (again weapons-grade OCD) I ended up about 3mm too long so they aren’t quite as tight as I’d like. Fixing it would involve working in fractions of millimetres to get it exactly right. Without having an original to hand I think I have the right number of bars and the right thickness (i.e. they should be slightly proud of the caps).

Here’s a brochure pic on Jim’s site that shows the top/bottom bevel. I’m pretty sure my red logo pair had these grilles. I’m happy where I ended up given I only had one go at it!

 

[mandryka]

It's all a matter of taste, but smooth foam on a JR just looks insipid to me.

FWIW - You can make the ribbed foam as tight as you wish by drawing it in at the back in exactly the same way as the smooth variety.

I particularly hate the optical qualities of the ribbed foam. Either you can't see that it's ribbed because of the dim light, or you can see that it's ribbed and it shines and reflects the light like sequins. Yuck. Smooth is best.

I am sure that Tony will ban me for saying this. Oh well, I shall be a martyr.

 

[ToTo Man]

I am just crazy OCD about this sort of thing and I came to the conclusion from studying original pictures that there is one more bar than that, i.e. there should be an odd number so one bar runs centrally over the logo/tweeter. Here’s my attempt:

I suspect this is very close indeed, but I also suspect JR used imperial measurements as (again weapons-grade OCD) I ended up about 3mm too long so they aren’t quite as tight as I’d like. Fixing it would involve working in fractions of millimetres to get it exactly right. Without having an original to hand I think I have the right number of bars and the right thickness (i.e. they should be slightly proud of the caps).

Here’s a brochure pic on Jim’s site that shows the top/bottom bevel. I’m pretty sure my red logo pair had these grilles. I’m happy where I ended up given I only had one go at it!

From Jim's site it's clear the mk1 foams had a bevel (or at least the red logo version did), I wasn't aware of this before. Also, assuming that image hasn't been vertically stretched out of proportion, the 'bars' look narrower than those on the Hartle foams, so yes I'd say your 29mm is closer to original spec than 33mm, the original looks as if it could even have bars that are thinner than 29mm.

EDIT - These are the Hartle foams for my mk1 I bought a few years ago. As you can see, there are minor variations in the sizings, and the 'bars' at each end haven't been cut to exactly the same width. However, if you're clever with how you fit them, you can have it so that a 'space' aligns with the tweeter, which gives you seven and a half 'bars' to each side.

 

[ToTo Man]

@Tony L, the photo I posted earlier of my mk2 grille clearly shows a 'bar' aligning with the tweeter, but the photo in this review shows a 'space' aligning with the tweeter, so maybe there is no 'correct' alignment? I might order my mk2 grilles a bit longer than 685mm so that I can chose whether to align a 'bar' or 'space' with the tweeter and then trim off whatever excess there is at the rear.

 

[Tony L]

Just heard from Graham via email regarding the grilles:

“To put the debate right the original..original foams the declon were 19mm bars so quite narrow and had a small bevel with a another line running top and bottom the same space as between the bars The foams I make are the size that where used after in the silver finish JR 149 Mk1 catalogue...”

This is what has confused me over the years as I didn’t realise there had been a change, and what I saw more recently didn’t match my memory of my red-logo Mk 1s. I guess logically my current pair, which I suspect are right at the very end of Mk 1 production would actually have had grilles like Graham’s. There was nothing beyond some sticky black goo in the box of mine, so I have no evidence.

One thing that really surprises me is the change from thin (cut) to thick (rib) section at the very ends of the grilles. I distinctly remember my red logo pair having the thin bit just the right size to feed under the ‘T’ section extrusion at the back of the cab. This meant the grille was held mechanically as well as by the velcro strips. I’m surprised they abandoned that as it was neat! It sounds like the original design was a far more complex cut with bevels on each side of the ribs.

If I can ever be bothered I’ll redo my grille plan and try and make it right for the first generation grilles complete with bevels. I don’t like providing information that I know to be incorrect, which obviously my plans are in light of now knowing the bar is 19mm. They work, look nice, but they are not right!

PS Another difference is the later Mk 1 box places both speakers next to each other the way one would expect with styrofoam top and bottom caps (annoyingly I’m missing one), my red logo pair had an odd tall hexagonal section box that placed the speakers on top of each other. There are a lot of changes over the life of the Mk 1s when one thinks about it.

 

[ToTo Man]

Just heard from Graham via email regarding the grilles:

“To put the debate right the original..original foams the declon were 19mm bars so quite narrow and had a small bevel with a another line running top and bottom the same space as between the bars The foams I make are the size that where used after in the silver finish JR 149 Mk1 catalogue...”

This is what has confused me over the years as I didn’t realise there had been a change, and what I saw more recently didn’t match my memory of my red-logo Mk 1s. I guess logically my current pair, which I suspect are right at the very end of Mk 1 production would actually have had grilles like Graham’s. There was nothing beyond some sticky black goo in the box of mine, so I have no evidence.

One thing that really surprises me is the change from thin (cut) to thick (rib) section at the very ends of the grilles. I distinctly remember my red logo pair having the thin bit just the right size to feed under the ‘T’ section extrusion at the back of the cab. This meant the grille was held mechanically as well as by the velcro strips. I’m surprised they abandoned that as it was neat! It sounds like the original design was a far more complex cut with bevels on each side of the ribs.

If I can ever be bothered I’ll redo my grille plan and try and make it right for the first generation grilles complete with bevels. I don’t like providing information that I know to be incorrect, which obviously my plans are in light of now knowing the bar is 19mm. They work, look nice, but they are not right!

PS Another difference is the later Mk 1 box places both speakers next to each other the way one would expect with styrofoam top and bottom caps (annoyingly I’m missing one), my red logo pair had an odd tall hexagonal section box that placed the speakers on top of each other. There are a lot of changes over the life of the Mk 1s when one thinks about it.

If you do re-do your mk1 grille let me know as I'd be interested in ordering a set too.

 

[calorgas]

Blimey, you guys are in deep with this foam grille business! I do prefer the appearance of the original ribbed foam, but when I was looking to buy some it was £30 for smooth vs about £120 for ribbed (from the US), and I decided that I didn't prefer ribbed that much.
I'm not that bound or dedicated to originality I suppose. I recently bought and attached some fairly recent Tannoy badges to the pair of Lancasters I have here. In all honesty I prefer them to the originals, and they were £10 instead of £75. Maybe I'm just a cheapskate

 

[Tony L]

Smooth grilles on JR149s totally trigger me! No way could I live with them hence going to the trouble and expense to get some made. I can’t remember how much I spent, I think about £140-150 landed, but I do have a spare pair sealed in a box away from any daylight (though these are treated, so allegedly won’t degrade the way of the originals).

I am hugely nerdy by nature, the ‘collector gene’ obsession runs very deep (it is why I’m a record dealer and likely why I was a good IT guy), so this sort of detail matters to me. It is just who I am. Exhibit B being my TD-124, which really was a remarkably obsessive rebuild!

 

[Martyn Miles]

Good to read that someone else is ‘nerdy.’
I’m obsessional about packing away my PA kit.
Only two close friends are allowed to help me, one of which is a PA engineer
who’s on the autistic spectrum.
I wonder...

 

[TonyScarlett]

I bit the bullet with mine & bought the ribbed grilles off the American supplier, they ended up costing about £150 with postage & customs charges but I figured as I've no intention of ever selling the speakers (made that mistake once) it was a worthwhile investment. They look so much better than the smooth grilles. Of course the day after I got the message that they had been shipped Tony L posted the message that Graham Hartle was making them again, for approx /2 what I had just paid. C'est la vie as The French would say, although I can't complain about the quality of the grilles I was sent, if Graham Hartles are as good then they are a bargain in my book.
TS

 

[ToTo Man]

Inspired by Tony's mk1 grille template, I think I've come up with a plan for my mk2 grilles.

The flat foam grilles that are currently on one of my pairs of mk2 measure 680mm long. This is too short as, unless you pull it tight, there's around a 10-12mm gap between the two ends of the foam at the back of the speaker (unlike the mk1, the mk2 has no t-piece to tuck the end into as the original mk2 grille is a one-piece sock). I reckon 692mm would allow the two ends of the foam to butt neatly without requiring any stretching.

Replicating the original mk2 foam requires 27 'bars' and 27 'spaces'. Having played around with the sizes I think 'spaces' that are half the width of the 'bars' look most aesthetically correct, so 27 x 17mm 'bars' and 27 x 8.5mm 'spaces' gives a total length of 688.5mm, which is near enough perfect. However, this will not guarantee that a 'bar' aligns with the tweeter. If I'm not mistaken, adding an additional 'space' onto one end of the foam solves this problem. This makes the total length of the foam 697mm. Assuming I haven't made any blunders, I think I'm ready to contact Graham.

 

[Tony L]

You haven’t counted your spaces correctly, there is one more as there is one each end. I had another email from Graham earlier and he reckons he can do the bevels too! Will be a bit dearer due to more complexity, but it sounds like proper replications of the originals would be possible. Same for early Mk Is too.

PS When calculating the length it is quite complicated as the correct measurement is half the thickness of the foam above the surface of the cylinder as when curved into place the outside of the foam expands, the inside contracts. It makes it a bit of a head-wrecker to calculate and I remember really struggling with it. I may actually just have used Graham’s length, I can’t remember, I did have his specs, I just re-jigged them as I wanted a central bar as I distinctly remembered that from my original 70s pair.

 

[ToTo Man]

You haven’t counted your spaces correctly, there is one more as there is one each end. I had another email from Graham earlier and he reckons he can do the bevels too! Will be a bit dearer due to more complexity, but it sounds like proper replications of the originals would be possible. Same for early Mk Is too.

Well spotted! I've fixed it now.

Great news regarding the bevels. I'm actually tempted now to get new foams for my 149 mk1, 149mk2 and 150. My wallet's gonna take some hit!

PS When calculating the length it is quite complicated as the correct measurement is half the thickness of the foam above the surface of the cylinder as when curved into place the outside of the foam expands, the inside contracts. It makes it a bit of a head-wrecker to calculate and I remember really struggling with it. I may actually just have used Graham’s length, I can’t remember, I did have his specs, I just re-jigged them as I wanted a central bar as I distinctly remembered that from my original 70s pair.

Yes, I tried measuring around the bare metal cylinder and then around the NOS mk2 ribbed foam sock and got drastically different results, so I resorted to measuring the smooth sheet of replacement foam on a flat surface and ended up with a figure that was roughly halfway between these values. My head spins when I think about stuff like this. Assuming ribbed foam doesn't behave differently to smooth foam when it's curved around the cylinder, the flat foam measurement should be a good enough proxy, shouldn't it? As I said in my previous post whoever cut the flat foams that came with my other set of mk2s cut them about 12mm too short, so an extra 17mm ought to give me enough safety margin.

FYI - I measured my existing Hartle 149 mk1 foams and they're all slightly different lengths, the shortest is 638mm and the longest 645mm, which is quite a bit shorter than your design. However, given yours have 'spaces' at either end instead of 'bars' I imagine it's easier to tuck more of the excess under the t-piece and achieve a neat/tight fit?

 

[Tony L]

I reckon mine are 3-6mm too long, though bare in mind mine are 14mm thick, so slightly thicker than Graham’s, i.e. they’ll contract/expand slightly differently.

 

[Tony L]

Great news regarding the bevels. I'm actually tempted now to get new foams for my 149 mk1, 149mk2 and 150. My wallet's gonna take some hit!

After looking at this pic for a while if Graham really can get that design precisely nailed I’ll be in for a pair myself. That bevel and narrower bar is actually quite an important aesthetic feature, they just look ‘right’ the way all really good design does. Obviously memory is part of it too as I still have a strong image of my first pair (which had lovely dark end-caps, probably walnut). The pair in the brochure pic are very interesting as they look to be a transitional pair as they don’t have the tweeter foam and deadsheet, but do have the gold logo.

 

[ToTo Man]

The pair in the brochure pic are very interesting as they look to be a transitional pair as they don’t have the tweeter foam and deadsheet, but do have the gold logo.

Unless they were just a 'window-dressed' pair for the photo shoot? The tweeter foam and deadsheet do reduce the aesthetic appeal somewhat, plus I've never actually seen a pair of 150s without deadsheet around the tweeter.

Interestingly, the foam on the 150 in that photo doesn't appear to have a bevel and look like the wider 33mm bar, so perhaps my 150 replica foams are period correct. They're still a few mm's too short top-to-bottom, which triggers my OCD no end, so I'll probably still order a new pair. The question then is whether to add the bevel, and what bar thickness to go for. Decisions, decisions...

EDIT - RE the mk1 grilles, you mentioned Graham said the original mk1 grilles had 19mm bars, did he say how wide the 'spaces' in between were?

 

[Tony L]

EDIT - RE the mk1 grilles, you mentioned Graham said the original mk1 grilles had 19mm bars, did he say how wide the 'spaces' in between were?

No, I don’t have that info nor any specs for the bevelling. My suspicion is all cuts are at a slight angle, not square as I cut them. Kind of like cubes on a chocolate bar if you get my drift.

 

[ToTo Man]

No, I don’t have that info nor any specs for the bevelling. My suspicion is all cuts are at a slight angle, not square as I cut them. Kind of like cubes on a chocolate bar if you get my drift.

I'm probably overthinking things now, but the bevel on my mk2 foams is more noticeable at the top than at the bottom. I don't know if this is how it would have left the factory or if gravity has pulled the foam downwards over time and the bottom bevel has compressed? Maybe that's the drawback of having a bevel at the bottom, 6mm foam being required to take the weight of the 12mm bars above it?

 

[Tony L]

It’s possible to overthink things?! I’m sure it was up to the task, but once the foam starts to decay/fail it will definitely suffer from gravity, plus stretch etc. The company that did mine implied there had been advances in materials and coatings in the years since and modern grilles should be far more durable long term. I suspect the originals only had a 15-20 year lifespan. I mentioned to Graham that he should maybe consider making grilles for SBLs, Saras, Isobariks etc as there is definitely a market here and elsewhere.

 

[Martyn Miles]

Someone on PFM was making foam grilles.
He made a pair for some Rega Kytes I owned.
I asked him to leave the triangular open reflex port and make them rectangular.
I thought they looked better than Way.