Pressed steel speaker chassis vs cast or plastic

[unpluggged]

engineering excellence

Can be a very vague concept. I was taught that "engineering excellence" is when you achieve target results with less effort and resources, not by spending more just for the looks of it.

 

[olieb]

"engineering excellence" is when you achieve target results

Yes, but there are different kinds of targets. Besides audio performance there could be marketing targets like the use of precious materials, expensive components and exquisite surfaces among other things. It seems marketing might be right, as there are customers that react to that.

 

[RoA]

Yes, but there are different kinds of targets. Besides audio performance there could be marketing targets like the use of precious materials, expensive components and exquisite surfaces among other things. It seems marketing might be right, as there are customers that react to that.

Of course. Some of us have to share living spaces so something purely subjective such as finish options/quality does matter occasionally. My biggest beef with some studio speaker designs, especially but not exclusively at the lower end.

 

[Killingbeans]

I may be shallow but perceived value plays a role in my decision making.

I don't think it's shallow. Just a natural part of being human in most cases.

I've got a diagnosis of so called "high-functioning autism", and one of the few upsides to that, is near complete immunity to a lot of these things.

But 100% rational thinking is nearly impossible to achieve as a human being, and even with my robotic traits I honestly don't mind paying extra for some peace of mind.

The only thing that really grinds my gears, is when the manufacturers make claims about tangible effects, like lower amounts of resonances and/or distortion, but show absolutely no data as proof.

 

[mhardy6647]

Interesting replies and enlightening. Thanks to those that contribute rather than get defensive.

I guess you can damp a stamped steel chassis further with mastic or other damping pads of sorts.

The rear venting or potential lack of it when comparing cast with stamped steel, as mentioned above will probably play a role too.

I remember a pair of very cheap MS 20i Pearls I had many moons ago, I believe it was co designed by R Marshall of old Epos fame. The driver was integrated into the front baffle as a whole plastic moulding. I took it off and damped the waffle back of the baffle with tons of blue tack. Sounded great . I have not seen such a construction since. Lovely drivers for what was a budget speaker.

View attachment 406716
Not the pearl edition but the closest I could find.

After reading all your replies I would still rather have a solid, cast driver, ideally developed by the speaker manufacturer itself rather than an off-the-shelf solution for any speaker above a certain price point.

This price point is difficult to ascertain, but ELAC and the IAG group prove it can be done with their Quad, Mission and Wharfedale designs that often/almost always use in-house designed drivers even on budget designs. I really liked the S2's I had for a long time and I would get another pair anytime if I needed a non-active stand mount or desk top speaker. I am sure they could, if needed, design an active speaker that measures 'perfect' but a lot of people prefer designs that suit their tastes rather than being text book perfect.

At the higher end, give me an active ATC over a Kii anytime but that's just me. That is if ATC use threaded inserts rather than screws direct in to wood!

Reminds me of the earliest production of the KLH Six, which (to the consternation of decades of rehabilitators) integrated the woofer with the front baffle (albeit rather less elegantly than the M-S example cited by @RoA ).

source: http://fisherdoctor.com/pictures/other/Speakers/KLH6.jpg
The four round 'plugs' peripheral to the woofer are the sites of attachment of four metal rods that are, in essence, the "basket" of the woofer.

source: https://community.classicspeakerpages.net/topic/9850-klh-model-6-restoration-no-driver-access/
This one has been exhumed from its integral particleboard baffle with a saw.

For the young whippersnappers here -- Henry Kloss was the K of KLH, and Anton Hofmann (of Hofmann's Iron Law fame) was the H.
EDIT: For completeness, the L was Malcolm Low.

My embarrassing (and somewhat scruffy) collection of KLH Sixes -- none of which has the epoxied woofers (fortunately).

 

[Holmz]

If you can stamp steel and have it be stiff enough to be a car chassis and protect you in a crash then a well engineered stamped speaker frame shouldn't be an issue.

But some of the most stiff car chassis are aluminium and some of the most flexible ones are steel?

 

[Keith_W]

Cheap doesn't mean poorly engineered. Good-looking and expensive material doesn't mean it's well-engineered either. You'll find plenty of counter-examples for both cases. Best to not look at the price, but let the objective data speak for itself.

I swear that nobody on ASR ends a thread faster than you. In the first reply you already provided a clear, concise, and irrefutable answer that ends the thread. All the other replies are simply agreement, including this one.

 

[Frank Dernie]

But some of the most stiff car chassis are aluminium and some of the most flexible ones are steel?

I would love examples of which to justify that statement!
The design shape matters (far) more than the material but it is only easy to match steel with ally by making it equally heavy.

 

[DanielT]

Cast chassis tend to be made from aluminium, which acts to reduce certain types of distortion in the loudspeaker motor. The steel in pressed chassis increases that distortion. Plastic can sometimes be the best compromise, as it can easily be strong enough, if it's something like glass filled nylon, it's also cheap and doesn't increase distortion.

Pressed metal sheet,stamped steel chassis does not automatically lead to relatively high distortion. See this classic for example. Peerless SLS 10, Klirrfaktor=distortion level:

A good cheap bog standard bass driver that I think many have built with at some point. I can recommend it BUT consider its limitations in terms of :
Power Handling (RMS) 70 Watts
Power Handling (MAX) 140 Watts
OT:
I thought I had too little amp power when I tested two in a sealed boxes in a medium sized room.


They didn't seem to produce much bass at higher volume, SPL. Turns out I needed two more drivers to suit my needs. Pros: low price
$60 via Parts Express:

Peerless by Tymphany 830668 10" Paper Cone SLS Subwoofer

Peerless by Tymphany 830668 10" Paper Cone SLS SubwooferThe Peerless SLS Series combines high quality performance with an affordable design. The SLS drivers are ideal for use in systems with high power handling requirements, and are a logical choice for use with the SDS line of transducers.

www.parts-express.com

...and good performance. Cons: low power handling and thus the possible need for several driver and boxes, which can be a challenge with furniture but an pro, advantage then regarding to curb the problem with with room modes.

Peerless SLS 10 is suitable for sealed boxes so it is possible to fix, boost the lowest bass with them via:

Linkwitz Transform

miniDSP is a leading manufacturer of Digital Audio Signal Processors for the HomeTheater, Hifi, headphone and Automotive market. Join our large community of Audiophiles, Engineers and DIYers using our innovative products.

www.minidsp.com

..at the expense of lower decent distortion-free SPL then. As usual trade-offs.

Experiences of and / or measurements Peerless SLS series?

Seems to be speaker element with good performance - price ratio.:) You who have used these speaker elements, what are your experiences? Are there any distortion measurements on any of the elements in the SLS series? I tried to find some but I did not find any.

audiosciencereview.com

 

[AOR]

Pressed metal sheet,stamped steel chassis does not automatically lead to relatively high distortion. See this classic for example. Peerless SLS 10, Klirrfaktor=distortion level:
View attachment 432089
View attachment 432083
View attachment 432084
A good cheap bog standard bass driver that I think many have built with at some point. I can recommend it BUT consider its limitations in terms of :
Power Handling (RMS) 70 Watts
Power Handling (MAX) 140 Watts
OT:
I thought I had too little amp power when I tested two in a sealed boxes in a medium sized room.
View attachment 432091

They didn't seem to produce much bass at higher volume, SPL. Turns out I needed two more drivers to suit my needs. Pros: low price
$60 via Parts Express:

Peerless by Tymphany 830668 10" Paper Cone SLS Subwoofer

Peerless by Tymphany 830668 10" Paper Cone SLS SubwooferThe Peerless SLS Series combines high quality performance with an affordable design. The SLS drivers are ideal for use in systems with high power handling requirements, and are a logical choice for use with the SDS line of transducers.

www.parts-express.com

...and good performance. Cons: low power handling and thus the possible need for several driver and boxes, which can be a challenge with furniture but an pro, advantage then regarding to curb the problem with with room modes.

Peerless SLS 10 is suitable for sealed boxes so it is possible to fix, boost the lowest bass with them via:
View attachment 432088

Linkwitz Transform

miniDSP is a leading manufacturer of Digital Audio Signal Processors for the HomeTheater, Hifi, headphone and Automotive market. Join our large community of Audiophiles, Engineers and DIYers using our innovative products.

www.minidsp.com

..at the expense of lower decent distortion-free SPL then. As usual trade-offs.

Experiences of and / or measurements Peerless SLS series?

Seems to be speaker element with good performance - price ratio.:) You who have used these speaker elements, what are your experiences? Are there any distortion measurements on any of the elements in the SLS series? I tried to find some but I did not find any.

audiosciencereview.com

Yeah, you're right. Having a steel chassis certainly is no guarantee of high distortion. Phrased another way, the steel in a chassis is rarely the greatest contribution to distortion. That being said, it is an inferior material to make a chassis, from a distortion perspective.

Here's an example of a driver with a steel chassis (4.5" bass driver):

The steel of the chassis is a significant conductor of the magnetic flux, and is definitely affecting the BL profile of the driver. When designing this driver, I made some slight changes to the gap geometry when I found out we were going for a steel chassis...
Despite the "high distortion" (my words...) steel chassis, the THD in the midband of the driver is pretty low. However, this is due to the reasonably large demodulation rings.
This is from a nearfield measurement of the driver in a test box, scaled to 1m. The blue curve is -40dB (1%)

 

[DanielT]

Yeah, you're right. Having a steel chassis certainly is no guarantee of high distortion. Phrased another way, the steel in a chassis is rarely the greatest contribution to distortion. That being said, it is an inferior material to make a chassis, from a distortion perspective.

Here's an example of a driver with a steel chassis (4.5" bass driver):
View attachment 432107
The steel of the chassis is a significant conductor of the magnetic flux, and is definitely affecting the BL profile of the driver. When designing this driver, I made some slight changes to the gap geometry when I found out we were going for a steel chassis...
Despite the "high distortion" (my words...) steel chassis, the THD in the midband of the driver is pretty low. However, this is due to the reasonably large demodulation rings.
This is from a nearfield measurement of the driver in a test box, scaled to 1m. The blue curve is -40dB (1%)
View attachment 432112

Aha, interesting.

You as a technical developer of drivers at KEF (which I didn't know you were when I wrote my previous post) of course already know what I wrote (pretty basic stuff).
Others who read my post above may find something useful or interesting.

BUT speaking of KEF and pressed metal sheet, stamped steel chassis. I wonder what the classic B200's distortion levels are? Perhaps unfair to compare a fifty year old design and performance with newly produced drives, but out of pure curiosity one can wonder. The B200 driver is still a classic.

You know it but for others reading. B200 an 8 inch bass driver. There were different magnet sizes, which went under the name B200. Then either SP1014:

..or B200 with the large magnet SP1039:
(maybe there were more models of the B200?)

This is how the B200 looks mounted in a KEF 104Ab:

If they were in full working order that buyer got a good deal I must say. Sold For: £170.00.

Pair of KEF 104Ab reference series speakers

Lot Number 1202. Pair of KEF 104Ab reference series speakers. Auctioned at Day Two - Artist Associated Guitars & Memorabilia (including The Alarm collection), Guitar Amplification, Effects, Spares & Audio Equipment on 9th December 2021

www.guitar-auctions.co.uk

 

[Devnull]

Yup

But some of the most stiff car chassis are aluminium and some of the most flexible ones are steel?

Sure and those were decisions made by the manufacturer for obtaining the design goals of the vehicle.

Everything is a compromise. Material costs, material availability, engineering requirements, engineering expertise, manufacturing costs, government regulations ( probably covered under engineering requirements), market price point, etc. even advertising, repair and after sales support. All of these factors and more are decisions that need to made before a product comes to market. How well they are implemented and how they are implemented are up to the team building the product.

 

[dfuller]

Yeah, you're right. Having a steel chassis certainly is no guarantee of high distortion. Phrased another way, the steel in a chassis is rarely the greatest contribution to distortion. That being said, it is an inferior material to make a chassis, from a distortion perspective.

Here's an example of a driver with a steel chassis (4.5" bass driver):
View attachment 432107
The steel of the chassis is a significant conductor of the magnetic flux, and is definitely affecting the BL profile of the driver. When designing this driver, I made some slight changes to the gap geometry when I found out we were going for a steel chassis...
Despite the "high distortion" (my words...) steel chassis, the THD in the midband of the driver is pretty low. However, this is due to the reasonably large demodulation rings.
This is from a nearfield measurement of the driver in a test box, scaled to 1m. The blue curve is -40dB (1%)
View attachment 432112

Yes, this is what I mean when I say a steel frame is, all other things being equal, higher distortion. That said, as you've noted, you can engineer your way around it.

 

[Holmz]

Yup

Sure and those were decisions made by the manufacturer for obtaining the design goals of the vehicle.

Everything is a compromise. Material costs, material availability, engineering requirements, engineering expertise, manufacturing costs, government regulations ( probably covered under engineering requirements), market price point, etc. even advertising, repair and after sales support. All of these factors and more are decisions that need to made before a product comes to market. How well they are implemented and how they are implemented are up to the team building the product.

Ok…
Let’s ignore the compromises, the market, then after sales, etc.

It is a simple fact that speed is used because it is easy, cheap and known.
If one is talking performance then steel is seldom the optimal except maybe for connecting rods and crankshafts.

But what do cars have to do with a speaker basket?

 

[Holmz]

I would love examples of which to justify that statement!
The design shape matters (far) more than the material but it is only easy to match steel with ally by making it equally heavy.

I was thinking of the Lotus chassis, which looks like the Lola chassis that maybe the GT40 was using in the olden days.
I have seen a list of nM/degree, but that is not normalised by weight/mass… so it is difficult to do an orangesranges comparison.

Bugatti Veyron - 60,000 Nm/degree
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
McLaren F1 13,500 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Volvo S60 20,000 Nm/deg

Rolls Royce Phantom: 40,000 Nm/deg
BMW E90: 22,500 Nm/deg
BMW Z4: 21Hz... :scratch: Now I just need to figure out how to convert that...
Audi A2: 11900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
BMW Z4 roadster: 16,000 Nm/deg
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Ford GT: 27,100 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg

But yes shape is important.
In the context of steel, that stuff is mostly stamped, and while things like A-Arm have some ripples in them, they can seldom be stiff with a one shot stamping.

Comparing a stereo chassis to a car chassis is a bit inane (IMHO).
Comparing a ski to a car might be better, as a ski should have a high torsional stiffness, and somewhat independent of the longitudinal flex/stiffness.

In any case, a speaker basket is mainly in tension and compression, with the motor/magnet causing a basket resonance.
Maybe shape can make a basket stiffer, but it seems like it is not easy to envision, and likely FEM could used to work it out.
At that point we know the resonant frequency and how it shifts, but it is not clear to me what we do with that.

 

[Penelinfi]

Ok…
Let’s ignore the compromises, the market, then after sales, etc.

It is a simple fact that speed is used because it is easy, cheap and known.
If one is talking performance then steel is seldom the optimal except maybe for connecting rods and crankshafts.

But what do cars have to do with a speaker basket?

They need to be strong to support a motor system and moving parts, and consideration for transmission of sound through the structure.

 

[Holmz]

They need to be strong to support a motor system and moving parts, and consideration for transmission of sound through the structure.

OK then - how do you see the sound being transmitted through the system?

What are the moving parts?
The Voice-coil, cone and dust-cap?
How much does all that crap weigh?

I cannot imagine that turning a basket out of a billet of aluminium makes sense

 

[Frank Dernie]

I was thinking of the Lotus chassis, which looks like the Lola chassis that maybe the GT40 was using in the olden days.
I have seen a list of nM/degree, but that is not normalised by weight/mass… so it is difficult to do an orangesranges comparison.



But yes shape is important.
In the context of steel, that stuff is mostly stamped, and while things like A-Arm have some ripples in them, they can seldom be stiff with a one shot stamping.

Comparing a stereo chassis to a car chassis is a bit inane (IMHO).
Comparing a ski to a car might be better, as a ski should have a high torsional stiffness, and somewhat independent of the longitudinal flex/stiffness.

In any case, a speaker basket is mainly in tension and compression, with the motor/magnet causing a basket resonance.
Maybe shape can make a basket stiffer, but it seems like it is not easy to envision, and likely FEM could used to work it out.
At that point we know the resonant frequency and how it shifts, but it is not clear to me what we do with that.

Somebody has been busy compiling that!
Indeed not knowing the weight makes it limited but interesting none the less.
I am amazed by the Veyron but it is very heavy for a 2 seater.

Trying to make a stiff light structure when the stylist has primacy is usually the limit, not materials.

Even with racing cars there are other more important parameters than chassis stiffness. The stiffest Formula 1 car I worked on was the Toyota, with stiffness having been a main design target from the management.
If stiffness was a crucial factor the Toyota would have been fastest everywhere.

 

[dfuller]

Ok…
Let’s ignore the compromises, the market, then after sales, etc.

It is a simple fact that speed is used because it is easy, cheap and known.
If one is talking performance then steel is seldom the optimal except maybe for connecting rods and crankshafts.

But what do cars have to do with a component chassis?

Steel has a lot of benefits for a car. It's got enough elasticity to be pressed into shape and can absorb road bumps without fatigue cracks (aluminum does not do so hot here, it's fairly brittle in typical alloys and can fail rather spontaneously), it's easy to weld (unlike aluminum), and it's cheap. It is however heavier and harder to machine.

Those benefits largely don't transmit to speaker frames - which need to pretty much by definition be as stiff as possible with durability being a far lower priority.

 

[Frank Dernie]

it's much stiffer but not elastic and can fail rather spontaneously

This is not true.
Aluminium and steel are available in a plethora of alloys, some very much more malleable than others.
Pure aluminium is neither stiff nor strong and all the alloys have a specific modulus around ⅓ that of steel alloys. It is pretty soft and malleable when pure but the alloying elements change its properties a lot.
Alloys which cast easily can be pretty brittle but they are not stiff, the alloys have close to the same modulus - what varies is the stress strain curve and the load before plastic deformation and failure.

It is true aluminium alloys have no load below which fatigue failure won't happen, whereas steels do.