AER vs Lowther and repairing suspensions

David Pinnegar

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Hi!

It's been a great pleasure finally to have a pair of AER drivers in my hands to play with that need refoaming, giving me the excuse to take them to pieces.

Just doing that is the first challenge! Every move of the spanner is impeded by the magnet snapping the spanner out of one's hands.

Looking at the specs it's hard to imagine what AER have done beyond the Lowther design. At around 2 Tesla the AER MD2 is comaparable to the PM2A but 8dB more efficient. Just how that has been achieved is extraordinary. Perhaps it's a deeper polepiece that gives an Xmax of 7mm rather than the Lowther +-1mm? The voice coil is smaller, wound on one side of the paper rather than the double layer of the Lowther and the wire is too thin to see individual turns of wire, yet does not appear to be thin on the leadouts . . . and yet is said to withstand, like the Lowther, 100W. My personal experience is that it's a mistake to put more than 20W on a Lowther but with the efficiency of these units does that matter? But will they really withstand 100W? Original earliest Lowther units had thin wire and were rated at a realistic 6W . . . at which they are deafening in any case . . .

Certainly the claim that AER give a range up to 80kHz is snake oil as their published graph extends to around 22kHz, like the Lowther, before tailing down 50dB at the 80kHz point.

The problem in refoaming the AER is the spider. Can one use Lowther spiders or with that 7mm Xmax does one need to buy a proprietary AER back suspension foam?

Best wishes

David P

 

AmDismal

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Be good to see some photos and measurements comparing the two. Certainly I'm impressed by 20Hz-80kHz, +/- 50dB :rofl:

Re the spider, The Lowther ones were quite tight, so I would have thought that you would need to use the AER stuff.

 

RobsterD

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You got Andy's MD2's David ?

I have the MD3's and the magnet on them is even scarier :)

Yes I would have a chat with Filip re the foam,I expect it will have a bearing on how they sound - from Andy's description they sounded broken as my original MD 2 's sounded great .

 

David Pinnegar

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Nov 26, 2010
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Hi!

Having the units with magnets separated from cones and one cone suspension being better than the other, and a spare PM2C magnet lying around I tried the AER cone on the PM2C magnet. I reckon that the Lowther magnet might give a couple of decibels more. Possibly the gap of the AER is a shade larger than the Lowther. The AER magnet gives a smoother sound, in comparison there being something hard from the Lowther C magnet on sibilants, something more agressive with the slightly higher efficiency. The only difference can be, possibly not the pole material but a resonance in the volume of space behind the voice coil gap on the Lowther.

With a spare Lowther "A" cone, I was able to compare the AER magnet with a PM2A and PM6A magnet - the PM6A being less efficient and a less pleasant sound than the PM2A and AER magnets which are comparable. I think the PM2A is improved with the doorknob stabiliser and possibly a foreshortened form to fit the AER might give the same effect. The voice coil of both AER and the Lowther A cones did not seem to make a remarkable difference. It would be interesting to test the AER cone on a DX4 magnet but without an excuse to take a DX4 to pieces I probably won't manage that comparison.

From comparison of the PM2 and PM5 which gives stronger treble than the PM2, a shootout between PM5 and MD2 and PM4 and MD3 would be rather interesting . . . but really possibly only a hair's breadth between them.

Best wishes

David P

 

RobsterD

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I've had DX2's DX3's,PM7A's PM2A's and PM6C's in my Oris 250/200 horns the PM2A's was the best of the Lowther bunch the step up from PM 2A's to AER MD2's wasn't a hairs breadth difference it was quite significant and again a marked improvement again going from MD2's to MD3's.

How PM4\5 sound I dont know my next step will be the Voxativ AC-X field coils :cool:

 

David Pinnegar

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in my Oris 250/200 horns the PM2A's was the best of the Lowther bunch the step up from PM 2A's to AER MD2's wasn't a hairs breadth difference it was quite significant and again a marked improvement again going from MD2's to MD3's.. . . How PM4\5 sound I dont know my next step will be the Voxativ AC-X field coils :cool:
My observations were only upon placing a bare mounted cone naked in the various voice coil gaps, the PM2 vs AER test being with a Lowther cone on account of the AER voice coil former not being long enough to reach into the A magnet gap. But the superiority of AER magnet is significantly audible. I'm going to have to find that excuse to take a DX4 to pieces to do the direct comparison . . .

However, the claimed superior efficiency of the AER does not appear to match observation.

Best wishes

David P

 

paulf-2007

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I've had DX2's DX3's,PM7A's PM2A's and PM6C's in my Oris 250/200 horns the PM2A's was the best of the Lowther bunch the step up from PM 2A's to AER MD2's wasn't a hairs breadth difference it was quite significant and again a marked improvement again going from MD2's to MD3's.How PM4\5 sound I dont know my next step will be the Voxativ AC-X field coils :cool:
Not wishing to hijack the thread, you might struggle to get AC-X field coils as they have been superceded by the AC-X2 and at £10,000 a pair they are out of my reach. I heard them in Voxative Ampeggio Due ( £75k ) , amazing for a single driver, did pretty much everything right, on par with my three way at twenty times the cost.
 

David Pinnegar

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I heard them in Voxative Ampeggio Due ( £75k ) , amazing for a single driver, did pretty much everything right, on par with my three way at twenty times the cost.
Personally I spend a lot of time listening to a pair of Lowther TP1A 1960s units, one with a PM5 and the other a DX4, and don't notice an earthshattering difference between the two . . . and despite the legendary status of these speakers and associated cost, cannot imagine how £75k could improve on them, let alone justify such expenditure when just a few pounds per week can alleviate starvation in this world.

One acid test is whether when radio interviews played through speakers give the illusion in the next room of a physical presence of real people . . . and the TP1s certainly do that and a lot more.

Meanwhile, I often play with modified full range drivers in the region of £100 - £200 which fitted into plain Acousta cabinets make one wonder whether decades of price multiplication are significantly proportionately audible at all. . .

Best wishes

David P

 

paulf-2007

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David, I have to say they are not worth £75k of anybody's money nor the field coil drivers at £10k a pair, but they are without doubt better than Lowthers. They do excellent bass and most everything else without the Lowther shout. One of the less expensive drivers in the range in a quarterwave box vertically firing towards a semi cicrcular inverted cone was shouty just like all the Lowthers I have owned and heard. I do have two pairs of those cheap drivers you were selling that are very good in Fidelio cabs and OB. I would take them instead of a Lowther any day.

 

David Pinnegar

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I've had the unfortunate experience of refoaming a pair of BD2 units. Unlike Andy's MD units mentioned in this thread which have a wide magnet gap which does not require precision circularity of the voice coil the BD2 units have the Lowther style 1mm voice coil gap. 

This caused unexpected complications. When preparing a voice coil after refoaming for reinsertion into such a gap, it has to be precisely circular to within  less than 1/4mm. The way of doing this is with a Lowther jig, a tapered mandrel upon which you force the voice coil down as far as it will go to stretch all give arising from non-circularity so as to ensure that it's as precisely circular as it can be. For good measure, I reverse the cone on the mandrel ensuring the whole voice coil tube is precise. 

Using an aluminium mandrel the problem is that this can leave grey or black marks on the paper.

When the bloke saw this, even though it's hidden by a phase plug in normal use, he accused me of devaluing his units. There was a history to his dissatisfaction as the units had presented other problems, worse.

Another problem of refoaming units is that when the foam is really old and brittle, it snaps away from the paper crisply and gives little problem in cleaning. But when the foam is just on the point, it goes like a toffee goo and is a right beast to clean. And you have to clean it perfectly as you can't stick new foam on top of goo. So I use meths to dissolve it. The problem is that once dissolved, it can be carried by the meths on one's fingers and I accidentally left a dark finger-smudge on the cone from the meths in handling the cone whilst cleaning. 

Oh dear. As far as I'm concerned speakers are to be heard, to sound, to sound perfect, and visual matters especially of old refurbished units are of secondary importance. 

Of course the bloke could have sent them to AER to have them done at four or five times the cost . . . . but I really wonder if when you send a unit to AER for refoaming whether they really do send you back the original cone rather than simply inserting a freshly made one. The problems of removing goo , to say nothing of glue, and get perfect results make me wonder.

In handling a number of Lowther units and seeing how AER have copied them, clearly doing enough to avoid Lowther being hot under the collar, I really wonder what's necessary sonically and what's necessary simply not to be like Lowther, and when I see that claim that AER reproduce up to 80,000Hz, about which I've commented in this thread, I really wonder about everything.

Lowther units don't all have the "Lowther Shout". I think the reputation has been unfairly attributed. The C units which have Ferrite magnets can produce resonant frequencies in the region of the sound of cymbals - but this isn't because of the magnets. It's because there's a short paper cylinder connecting the voice coil to the cone, and resonances between one end of the paper and the other are not damped. This is cured by the A series and DX and EX with Alnico or Neodimium magnets. It's not the magnet that cures the shout but the longer length of paper cylinder connecting the two units and this provides enough disconnexion to interrupt any travelling waves. The paper is a treated paper like the rest of the cone. The foam spider used to be glued on with a brown glue, possibly shellac, which is brittle and often snaps away from the paper. I use Copydex, a latex glue for gluing the spider, which in future will always simply peel away from the paper.

It was coming to the gluing of the spider on the AER that I ran into real trouble. AER use some sort of glue possibly like silicone which can't be peeled off the paper without danger of tearing the paper. Unlike Lowther treated paper, the AER voice coil is on an untreated paper of the consistency of photocopy paper. Not only could I not remove the original glue, and can't imagine how AER can either, upon gluing on the new spider the water content of the Copydex glue simply disintegrated the paper. Inserting it onto the mandrel as a former to keep shape, it simply tore off. This was a surprise and a nightmare beyond contemplation.

Upon consulting an old friend who used to work for Lowther he said that they had this sort of problem from time to time and it was possible simply (not actually) to glue a new slither of paper inside to reconnect the voice coil to the cone and resolder the wires, and which even to my surprise I did successfully. So the unit was in working order again and working well, with no audible difference between the sound of the two newly refoamed units, the other one on which I'd used a thin silicone as glue.

As soon as I had the problem I confessed to the owner and this put him into the blackest of moods.

I'd loaned him a pair of the 97dB Lowther Challenge units available on eBay, which are rather good. (Perhaps I might talk about those on another thread) When he arrived to collect his AER units I asked him if he had brought my Chinese units back. He hadn't and from which I deduced that the bloke had come merely to haul me over the coals and give me grief.

He complained that I'd devalued his units, but the reality was that I handed back to him two perfectly serviceable newly refoamed working units.

AER charge 560eu each for refoaming (if in the light of what I've seen whether that's really possible) or 1500eu for reconing and upgrading. So for anyone really wanting the latest most improved AER experience an upgrade should be the way to go and to ensure top value is kept in the units.

As he was extremely dissatisfied with the quality of my work, with a mark on one and the other with a repaired voice coil assembly, I didn't charge and I'll be surprised to see my Chinese units back again.

I wouldn't be surprised were he to have intended keeping and using my Chinese units, as they're good, and expecting to sell the refoamed AER units for top whack.

He told me that he'd seen on YouTube how simple it was to replace Lowther foams. Ha ha! I responded that if he'd done his AERs himself he'd have got into a worse mess than I had found myself in, and then not have been able to repair them at all. 

Having looked at the AER and the Lowther units, for a number of reasons I know which I'd choose for myself. The roll back surround to the whizzer on the Lowthers needs to be flipped forward to restored to the original vintage format and then the A, DX and EX series are superb.

And for anyone wanting a cosmetic as well as a functional restoration of AER units, please do go to AER. I don't want to be in a situation of dissatisfaction ever again.

Best wishes

David P

 
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Tony_J

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I'd loaned him a pair of the 97dB Lowther Challenge units available on eBay, which are rather good. (Perhaps I might talk about those on another thread)
Please do David - that would be interesting. Are these the Chinese units you have been selling for some time now, or are they a new offering?

I can sympathize with your refoaming experience - as you know, I have refoamed a few Lowther units myself, and it can be a difficult job even when the material is treated paper. I suspect that AER would actually replace the whole of the cone assembly rather than attempt to salvage the cones.

 

David Pinnegar

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Tony - long time no hear.

And actually you're an inspiration on soldering voice coil wires as you've nailed this reliably and encouraged me to persist in experiment until getting it right.

The Chinese units aren't mine - they're much more expensive, marketed as "HiEND 8inch fullrange speaker 97db PK lowther KO fostex" from seller Anitaydavid currently on https://www.ebay.co.uk/itm/pair-2-unit-HiEND-8inch-fullrange-speaker-97db-PK-lowther-KO-fostex/322086949721 and I will be most frustrated to have lost my pair.

Thank you for your sympathies. I did the best job possible under the circumstances as a matter of goodwill and with what became hideously difficulty without an ounce of appreciation and a slap in the face to go with it.

Best wishes

David P

 

 
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Tony_J

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Tony - long time no hear.

And actually you're an inspiration on soldering voice coil wires as you've nailed this reliably and encouraged me to persist in experiment until getting it right.

The Chinese units aren't mine - they're much more expensive, marketed as "HiEND 8inch fullrange speaker 97db PK lowther KO fostex" from seller Anitaydavid currently on https://www.ebay.co.uk/itm/pair-2-unit-HiEND-8inch-fullrange-speaker-97db-PK-lowther-KO-fostex/322086949721 and I will be most frustrated to have lost my pair.

Thank you for your sympathies. I did the best job possible under the circumstances as a matter of goodwill and with what became hideously difficulty without an ounce of appreciation and a slap in the face to go with it.

Best wishes

David P

 
David - indeed, it has been a while 

Thanksfor the kind words - I have to say though that re-soldering ally voice coils isn't an exercise that I would be in a hurry to repeat unless absolutely necessary!

Those Davidlouis units look very interesting - it would be good to hear more about them and how they compare to the Lowthers.

Regards,

Tony

 

David Pinnegar

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Those Davidlouis units look very interesting - it would be good to hear more about them and how they compare to the Lowthers.
Flat. Audibly flat. Unexcitingly boringly flat. But one has the feeling this flatness is accurate. I have tried adding a cone extension to the whizzer and the AER man who now has them told me initially he couldn't hear the difference.

If ever they come back to me I'll be able to comment further.

Best wishes

David P

 
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Tony_J

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Flat. Audibly flat. Unexcitingly boringly flat. But one has the feeling this flatness is accurate. I have tried adding a cone extension to the whizzer and the AER man who now has them told me initially he couldn't hear the difference.

If ever they come back to me I'll be able to comment further.

Best wishes

David P
That sounds promising. You might just have cost me 300 quid... :dunno:

 

David Pinnegar

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I don't think you're going to be disappointed.

I have half a suspicion that were I not to have loaned the AER bloke the pair of Chinese units he'd actually have been more than grateful for the functioning of the AERs as a result of my re-foaming and that he might even have paid me having saved him rather a lot on the cost of sending them off to AER. The fact that he didn't bring the Chinese units back says a lot.

As far as I'm concerned they're worth every penny and more.

Best wishes

David P

 
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David Pinnegar

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The sequel to the AER refoaming disaster was that their owner saw the light of day, brought back my David Louis Audio units (sadly no longer made) and I loaned him a pair of DX4. He prefers the DX4 to his AER! . . . . And I haven't had them back yet. Need to chase.

Meanwhile I serviced a pair of Stamm units a month or so back. Really lovely beasties and meticulously made.

Best wishes

David P

 
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