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RochaCullen
20-07-2009, 12:01
Hi All,

This is my first foray into speaker building and I think I picked a bit of a tough one. After three iterations I finally got a decent result.

I order the seas drivers and crossover gear from madisound in the states:

http://i830.photobucket.com/albums/zz230/rochaCullen/speakers/components_step1.jpg

Constructed the internal mould for the speaker cabinet using styrofoam, just to make it easy to gouge it out at the end I wrapped the main piece in clingfilm:

http://i830.photobucket.com/albums/zz230/rochaCullen/speakers/drivercutouts_step3.jpg

missing from this pic is the internal piece for the connection terminal

Then I shoved the port tube in the back of the big piece of styrofoam and assembled the mould:

http://i830.photobucket.com/albums/zz230/rochaCullen/speakers/securemould_step6.jpg

After a couple of days of drying I pulled it out:

http://i830.photobucket.com/albums/zz230/rochaCullen/speakers/removefrommould_step8.jpg

and after a bit of sanding, painting and crossover assembly, I put the whole thing together:

http://i830.photobucket.com/albums/zz230/rochaCullen/speakers/paintassemble_step9.jpg

I still have to build a set of stands for them, which will have to be pretty strong as the speakers weigh about 45-50 kilos a pop, as well as that I have to give them another coat of paint and put the crossover into a protective box.

As regards the sound, will know a heck of a lot better when I manage to put them on proper stands and position them correctly, but other than those obvious problems of context, they sound fantastic.

I had the idea of sticking a set of casters on the bottom of the stands that I build, any opinions on whether that would be a good idea or not?

Thanks,

Nathan

Labarum
20-07-2009, 13:44
I don't know why concrete isn't routinely used.

Wharfedale made kit many years ago that dropped inside a drainpipe. Column loudspeakers on the cheap!

RochaCullen
20-07-2009, 14:00
A friend of mine was raving about how great a cabinet material concrete is, so instead of exhausting my limited woodworking skills, I thought I would give concrete a go. After a couple of mistakes I managed to get it about right, its a learning game.

There are, of course, a number of things I would have done differently. In the latest incarnation I increased the depth of the mould internals by about 15mm, which was not matched by an increase in the depth of the mould externals. This put a bit more stress on the mould than there should have been and caused a warp in the walls of the resulting cabinet. I thought the mould would be able to cope with the small increase, but this was not the case. The pressures inside the mould mean that any mistakes in measurement become exaggerated. Sometime, again, when I have the time/inclination, I will have another crack at it and produce a perfectly symetrical pair.

aquapiranha
20-07-2009, 18:15
That is brilliant! well done you for even attempting it!

There have been a few commercial designs in the past, but none seemed to break the mould if you wil pardon the pun!

Yours look fab though.

NRG
20-07-2009, 20:57
I don't know why concrete isn't routinely used.

Wharfedale made kit many years ago that dropped inside a drainpipe. Column loudspeakers on the cheap!

:) The weight, the cost, consistancy of finish etc. Imagine the shipping costs for a large floor stander and then having to man handle them at the customers....god help him if he lived in a top floor flat! Just don't drop one and pray the shipping Co. hasn't already done so.

:lolsign:

And then the floor may need reinforcing as well! :doh: Maybe OK for DIY but not a good commercial proposition.

RochaCullen
21-07-2009, 09:33
:) The weight, the cost, consistancy of finish etc. Imagine the shipping costs for a large floor stander and then having to man handle them at the customers....god help him if he lived in a top floor flat! Just don't drop one and pray the shipping Co. hasn't already done so.

:lolsign:

And then the floor may need reinforcing as well! :doh: Maybe OK for DIY but not a good commercial proposition.

Yea, this is more of a problem than you would initially think. They are very heavy and a lot of work. Mass production of something like this would be a major engineering feat, not really feasible unless you gave your cabinets ultra thin reinforced walls.

The big problem I found was creating a solid set of holes for the screws holding the drivers. The driver recess and the holes for the screws are so close together that the brittle concrete would need a lot of time to dry out and develop the required strength. I tried two different methods before I finally gave in and included pieces of wood dowling in the mould which would remain embedded in the concrete. The driver screws could then be driven directly into the dowling.

If anyone fancies having a go at this I have a number of tips which can make things a lot easier.

My next task is to build some decent speaker stands. I wonder has anyone any tips on how to go about this.

Nathan

Hypnotoad
21-10-2009, 17:57
That's a great idea as concrete would not be resonant like wood.

A couple of things. You can colour the concrete using oxides and you can buy a bag of reinforcement that you just mix in with it. You must of course vibrate it when you put it in the mould.

The other thing is that if you mix the beans from bean bags with it, it makes the concrete lighter.

Rare Bird
21-10-2009, 19:02
Only concrete speakers i remember were from Avance yonks ago, i think they were Danish..

Cotlake
21-10-2009, 20:48
Focal used to offer a driver kit with plans for concrete enclosures.

steveinspain
21-10-2009, 21:00
Now this appeals - here in Spain concrete is THE main building material, so it could be cheap to try out.
Anyone got any ideas about dimensions, drive units etc - all need to be cheap as chips and guaranteed to produce a decent, if not neigh-on perfect sound.....
Any ideas ?

Covenant
22-10-2009, 09:22
Following on from the comments about the cost of transport if manufacturers tried to produce concrete speakers I wonder if a double skin MDF cabinet would be possible? Then when you have them at home you could fill the gap with dry sand. Just a thought!

Labarum
22-10-2009, 09:33
Following on from the comments about the cost of transport if manufacturers tried to produce concrete speakers I wonder if a double skin MDF cabinet would be possible? Then when you have them at home you could fill the gap with dry sand. Just a thought!

G.A. Briggs of the Wharfedale Wireless Works advocated sand filling.

ListeningEar
15-02-2014, 23:49
I know this is an old thread but thought you might be interested in seeing the latest speakers I have in for restoration, they are Avance Concrete 190's, old Danish company.

https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn1/t1/p403x403/1618623_365010190307124_881425900_n.jpg

https://scontent-b-lhr.xx.fbcdn.net/hphotos-prn2/t1/s403x403/1549206_366317840176359_1365024917_n.jpg

walpurgis
16-02-2014, 00:11
I know this is an old thread but thought you might be interested in seeing the latest speakers I have in for restoration, they are Avance Concrete 190's, old Danish company.

I seem to recollect those. I recall Elipson made concrete cabinet speakers too.

The Grand Wazoo
16-02-2014, 00:15
I do remember those!
It was half a lifetime ago and I remember being in a crowd of folks at a show, almost all of whom were appalled at the thought of a white speaker of all things!
Personally, I thought they sounded quite good......

Reffc
17-02-2014, 09:48
I think there's still a Swedish company making a range of concrete loudspeakers...Monolith or Monolit or something.

Barry
17-02-2014, 14:32
Back in the early '70s I knew someone who had built Kef Kit 3 (I think) speakers using concrete enclosures. The raw concrete was then (later)clad with veneered chipboard. The speaker stands were made from industrial Dexion strip!

In the late '80s a UK company called Faraday offered concrete speakers for sale. A collegue of mine at work had a pair. I never heard them so cannot comment on the SQ, but concrete does seem to be an interesting material from which to make speaker enclosures.

nat8808
17-02-2014, 16:20
I also have a pair of Avance speakers but smaller pyramids and attached stands.. Actually use decent drivers, scan speak tweeter and err... Vifa mid bass? .. from memory. Keep meaning to sell them on but know I'll get nothing for them if I don't do them up (bits of paint missing, couple of chipped corners, tweeter baffle foam gone sticky as per all of those scanspeaks!)

Now some say you should go WITH the concrete vibe and show it in all it's glory! Saw a pair of these on ebay 6 months or so ago:

http://i.ebayimg.com/t/RAUNA-LEIRA-LOUDSPEAKERS-TRANSMISSION-LINE-OPUS-3-RARE-/00/s/MTI5Nlg5Njg=/z/HaYAAOxycSdRzenZ/$(KGrHqJHJB!FGnKB5Fr,BRzenYz(rQ~~60_58.JPG

http://hifigoteborg.se/speakers/rauna_leira_test.htm

chris@panteg
17-02-2014, 17:11
I do remember those!
It was half a lifetime ago and I remember being in a crowd of folks at a show, almost all of whom were appalled at the thought of a white speaker of all things!
Personally, I thought they sounded quite good......

I remember hearing those, sounded good with hard rock I thought.

Barry
17-02-2014, 17:13
I remember hearing those, sounded good with hard rock I thought.

:lol:

The Grand Wazoo
17-02-2014, 20:25
I thought you were going to say that they sounded quite pour.

vinylspinner
17-02-2014, 20:37
Ideal if you are into the Stones.

Nigel

lurcher
17-02-2014, 21:55
That's a great idea as concrete would not be resonant like wood.

More than you might imagine. There is a chap who makes concrete speakers who brought a pair to Owston last year, Simon who just happens to be a Engineer responsible for motorway bridges had a very interesting conversation, and the outcome was that concrete is a lot more resonant that you might expect, and at a highish frequency. His suggestion was to mix rubber particles in with the aggregate to help damp them.

chris@panteg
17-02-2014, 23:13
I thought you were going to say that they sounded quite pour.

:)very good.

StuN
17-02-2014, 23:22
I have a book somewhere in my archive about making enclosures out of low-density concrete. I seem to remember that the enclosure was poured in a mould and the front panel was wood and fixed with bolts. I'll try and find it and see if there are any tips about construction methods.

Barry
17-02-2014, 23:54
More than you might imagine. There is a chap who makes concrete speakers who brought a pair to Owston last year, Simon who just happens to be a Engineer responsible for motorway bridges had a very interesting conversation, and the outcome was that concrete is a lot more resonant that you might expect, and at a highish frequency. His suggestion was to mix rubber particles in with the aggregate to help damp them.

Concrete, like any other material, does not have a resonant frequency as such. Structures have resonant frequencies, the frequency of which depend on the geometry of the structure with the Q-values (how sharp the resonance is, and how well it is damped) depending on the material properties of the material from which they are made.

REXTON
18-02-2014, 08:46
Do a search under Alexander accoustics

Reffc
18-02-2014, 09:10
Concrete, like any other material, does not have a resonant frequency as such. Structures have resonant frequencies, the frequency of which depend on the geometry of the structure with the Q-values (how sharp the resonance is, and how well it is damped) depending on the material properties of the material from which they are made.

Correct. Even if it was a homogeneous material which DID have a resonance at HF, providing that the resonance occurs above the critical mid range and high into HF response, then that is where we want it....not down low or within mid band. Every structure, be it a laminate or single material has a harmonic resonance point. The speaker designer's job is to ensure that the resonance is low in SPL terms (preferably well under -30dB if panels are considered as a radiator)and high enough in the frequency range (preferably above 10 to 15KHz).

This is where computers have helped in speaker design as finite element analysis is a very good tool for modelling cabinet response, although it can be done longhand (and as a young graduate engineer I remember spending many hours undertaking long hand finite element analysis on various structures). The interesting thing is that with the average cabinet, there are two basic rules when considering how to stiffen an enclosure: Firstly spacing between bracing should never be equi-distant and secondly, there will be an optimum number of braces beyond which you'd get the same result by doubling up cabinet panel thickness.

Concrete's behaviour and stiffness can be vastly improved by introducing glass fibres into the mix (using 10mm aggregate and making walls 50mm thick). Doing this, the average floor stander, let alone stand mount, will need no bracing. It will be stiff enough.

Another way to achieve similar results is to use 18mm Baltic Birch Ply (slow grown and dense) and line the inside with thick ceramic tiles glued to the interior panels. The resulting laminate is incredibly stiff and dense.

Be that as it may, most constructions still benefit from some form of damping to excel as speaker cabinets, just to limit the duration and amplitude of resonance. Whilst some manufacturers tout "tuned" cabinet resonance as part of the bass reinforcement, such designs usually sound too coloured and muddied for my personal preferences.

Macca
18-02-2014, 13:01
There are those Bosendorfer speakers that actually have vibrating panels attached to the speaker. Very odd way of doing things IMO

nat8808
18-02-2014, 13:41
Except that if you have resonant panels which resonate at a frequency different to the natural resonance of the cabinet it can kind of dampen the cabinet resonance.

There was a sound insulating material talked about in New Scientist once which was only a few mm thick - it consisted of a resonant rubber-like membrane attached to a grid in which each square there was a weighted disc suspended. The weighted discs and membrane each had natural resonant frequencies which cancelled each other out (along with all their harmonics) enough so that the result was a massive attenuation of sound trying to pass through it across a wide bandwidth.

3D printing made it possible for economic manufacture which otherwise was too complex.

nat8808
18-02-2014, 13:44
I had a pair of Jordan JX92 single driver speakers for a bit, transmission lines I think, which had a concrete front and rear panels and then veneered.

They were pretty good (but annoyingly sounded much better in the living room of the guy I sold them too! Often happens..). Were home-made (but still a mini commercial exercise) in someone's shed who had a little following in the JX92 world.

Reffc
18-02-2014, 14:05
Except that if you have resonant panels which resonate at a frequency different to the natural resonance of the cabinet it can kind of dampen the cabinet resonance.

There was a sound insulating material talked about in New Scientist once which was only a few mm thick - it consisted of a resonant rubber-like membrane attached to a grid in which each square there was a weighted disc suspended. The weighted discs and membrane each had natural resonant frequencies which cancelled each other out (along with all their harmonics) enough so that the result was a massive attenuation of sound trying to pass through it across a wide bandwidth.

3D printing made it possible for economic manufacture which otherwise was too complex.

That sort of misses the point. Any significant amplitude in the sensitive midrange frequency or lower upper frequency is bad, and adding resonant panels of a different frequency isn't really damping since it has no effect on anything other than it's own frequency (or equal multiples thereof). What it does is to shift the system resonance point one way or the other or introduce even more unwanted resonant panel amplitudes further colouring the sound. There are manufacturers using resonant panels for specific frequencies (Broadman acoustics springs to mind) and whilst they may sound great with certain instruments, they may also ultimately be coloured in other areas . Damping, by definition is a shortening of the resonance amplitude duration or a lowering of the amplitude or (preferably) both. Damping can be effected by laminar panel construction using absorbing layers between structural layers, by increasing stiffness (damps amplitude and lifts frequency) or by damping surfaces, (hence the use of bitumen etc) and also by the type of glue used to construct the speakers. Many (if not most) manufacturers have cottoned onto this and use "lossy" glues for panel joints. I used this trick myself for the Rhapsody and Fidelio speakers (as well as using exceptionally rigidly braced cabinet panels).

tpbholm
19-02-2014, 17:05
I have a pair of Opus3 Credo speakers that are made of a composite of crushed marble and concrete. They are actually the same shape as yours. The crossover is housed in a bakelite plinth which is bonded to the bottom of the speaker. I've had them for 20+ years. They were manufactured for Opus3 which is a Swedish company. The company is still going strong, it specialises in producing high quality audiophile vinyl LP's.

The speakers themselves sound fantastic and compare well to my more modern B&W 685's. I use them exclusively for vinyl playback fed by my Linn LP12.

Here's a link to some ltd info about them if you're interested: http://www.audiocircuit.com/Home-Audio/Opus-3

Mr Kipling
19-02-2014, 21:47
They also make mechanical tangentianal tracking arms.

nat8808
19-02-2014, 22:27
That sort of misses the point. Any significant amplitude in the sensitive midrange frequency or lower upper frequency is bad, and adding resonant panels of a different frequency isn't really damping since it has no effect on anything other than it's own frequency (or equal multiples thereof).

Depends... what matters is the final resonant amplitude and frequencies. If all parts combine to create a resonance which is out of important ranges then that could be good.

A panel which resonates at a slightly higher frequency to the tuned air inside (for example) can greatly dampen those resonances as the energy of one will be absorbed by the other rather than resonating in sympathy.

I've no idea what the Bosendorfer speakers actually do or how they work though, just talking very generally here..

nat8808
19-02-2014, 22:35
I have a pair of Opus3 Credo speakers that are made of a composite of crushed marble and concrete.

I guess concrete can take many forms..

In which case let's not forget the Celestion Kingston:

https://www.filepicker.io/api/file/lBecVvJhTemA8rkpMzDh+IMG_4217.JPG/convert?w=840&h=630&fit=max

Made of a powder and non-toxic resin compound with granite agregate (mainly for appearance). But still pourable and you would use the material just like concrete.

It is this stuff, commercial name Jesmonite: http://www.flints.co.uk/acatalog/Jesmonite_AC100.html

I have some Kingston cabinet/stands and the stands have white sink drainage pipes embedded in them for the cables :) Seems all very home-made when you examine how things are really constructed!

Reffc
20-02-2014, 06:33
Depends... what matters is the final resonant amplitude and frequencies. If all parts combine to create a resonance which is out of important ranges then that could be good.

A panel which resonates at a slightly higher frequency to the tuned air inside (for example) can greatly dampen those resonances as the energy of one will be absorbed by the other rather than resonating in sympathy.

I've no idea what the Bosendorfer speakers actually do or how they work though, just talking very generally here..

Panel harmonic resonance works independently from other panel frequencies. If something is causing a panel to resonate "in sympathy" then it isn't at a different frequency to the natural resonance point of that panel. I see where you're coming from though as it's the effects of resonance decay that can limit alternative frequency resonance effects, but where stiff panels are concerned, the decay times are usually sufficiently small in many designs for that simply not to be effective. Be that as it may, trying to cure one resonance by introducing another another isn't a very good way of trying to control panel resonances, as all muddy the sound to a greater or lesser extent. As you say though, providing those resonances are shifted where it doesn't matter, that, or controlling them is what counts.

nat8808
20-02-2014, 16:20
Panel harmonic resonance works independently from other panel frequencies. If something is causing a panel to resonate "in sympathy" then it isn't at a different frequency to the natural resonance point of that panel. I see where you're coming from though as it's the effects of resonance decay that can limit alternative frequency resonance effects, but where stiff panels are concerned, the decay times are usually sufficiently small in many designs for that simply not to be effective. Be that as it may, trying to cure one resonance by introducing another another isn't a very good way of trying to control panel resonances, as all muddy the sound to a greater or lesser extent. As you say though, providing those resonances are shifted where it doesn't matter, that, or controlling them is what counts.

Or creating an artificially "musical" sound, a bloom in some midrange area.. Some people do go for that, often in high-end speakers..

Reffc
20-02-2014, 19:37
Or creating an artificially "musical" sound, a bloom in some midrange area.. Some people do go for that, often in high-end speakers..

...yes, and to enhance bass response as in the case of one or two Harbeth/AN speakers (which may sound "musical) but are not exactly accurate in the bass...IMHO

sq225917
21-02-2014, 09:27
Patrick Handscombe made concrete speakers for years in the UK under the Electrofluidics brand. They were vibra moulded foamed concrete with some particulate filler. I spoke to him when building a composite loudspeaker cabinet during my degree. I ended up using an epoxy resin base loaded with rubber dust, wood flour and powdered glass. I literally made and NDT'd hundreds of sample tiles before arriving at a mix with high self damping, high mass and stiffness and available to take a great surface finish. Happy days...

struth
21-02-2014, 23:14
I used to be a concrete repair specialist.....maybe there is a new job opportunity for me:eyebrows:

nat8808
21-02-2014, 23:39
Patrick Handscombe made concrete speakers for years in the UK under the Electrofluidics brand. They were vibra moulded foamed concrete with some particulate filler. I spoke to him when building a composite loudspeaker cabinet during my degree. I ended up using an epoxy resin base loaded with rubber dust, wood flour and powdered glass. I literally made and NDT'd hundreds of sample tiles before arriving at a mix with high self damping, high mass and stiffness and available to take a great surface finish. Happy days...

Always fancied trying some Electrofluidics speakers from the decsription of their sound.

Any photos of the end product Simon (bet would need some scanning in)?

Reffc
22-02-2014, 09:52
Always fancied trying some Electrofluidics speakers from the decsription of their sound.

Any photos of the end product Simon (bet would need some scanning in)?

I'd be very interested too Simon. Sounds like a really interesting project.

Naughty Nigel
09-03-2014, 21:44
Some mad fools used to build boats in reinforced concrete (Ferro Cement)!

I built a set of concrete lined loudspeaker cabinets myself in my youth. These were very successful in reducing colouration, but I hadn't really planned ahead properly, and the concrete reduced the cabinet volume rather more than I had expected, reducing bass response.

However, concrete loudspeaker cabinets are not really a viable commercial proposition. Apart from any other consideration, most loudspeakers are now manufactured in China. so the cost of transporting them back to Europe in one piece would be prohibitive.

What does surprise me is that nobody has built commercial loudspeaker cabinets in FRP composite. Sandwich structures are incredibly stiff yet light in weight. There would be very little in the way of colouration, and any cabinet resonance that did arise would be easily damped with self adhesive sound deadening sheets (as used in motor vehicles).

Nigel.

sq225917
11-03-2014, 21:34
Always fancied trying some Electrofluidics speakers from the decsription of their sound.

Any photos of the end product Simon (bet would need some scanning in)?


I've got nothing left from my degree, it was 16 years ago. Lost in the last house move.

ListeningEar
14-07-2015, 08:29
Sorry Chaps, this project was put on the back burner but am now about to start finishing the cabinets as all drivers are ready to be re-installed. I have also been working on another pair or concrete loudspeakers from Sweden, Rauna Leira's but these will have a modified driver type.

Craig

Spectral Morn
14-07-2015, 11:47
Only concrete speakers i remember were from Avance yonks ago, i think they were Danish..

Shan Acoustics also had a speaker on the market that was made from a blend of concrete and some kind of additive (I don't know what) and they were very fragile, drop them and bang nothing but a pile of dust and bits.

They sounded great but way too fragile and finish was inconsistent.


Regards Neil

ListeningEar
18-07-2015, 07:02
The Avance and Rauna cabinets I am working on are very solid and well constructed, nothing fragile here. But then when does dropping a speaker become a concern for most buyers, surely that's not something us owners are in the habit of doing?! Hehe

tubehunter
18-07-2015, 07:17
Breeze/cinder blocks make a great speaker enclosure.
Cheap and easy to construct just add baffle and rear panel.

anthonyTD
18-07-2015, 08:06
The Electrofluidics with Jordan drive units sounded very good, they were made from a blend of polymer concrete from memory, apparently the same kind of material that is used on oil rig platforms.
A...

Box13
18-07-2015, 08:52
Some mad fools used to build boats in reinforced concrete (Ferro Cement)!
However, concrete loudspeaker cabinets are not really a viable commercial proposition. Apart from any other consideration, most loudspeakers are now manufactured in China. so the cost of transporting them back to Europe in one piece would be prohibitive. Nigel.

Bendix used to set their main bearing in concrete to stop vibration on spin.
It was not possible to lift one onto a sack barrow, it took two men.

walpurgis
18-07-2015, 09:01
Bendix used to set their main bearing in concrete to stop vibration on spin.
It was not possible to lift one onto a sack barrow, it took two men.

It was not uncommon in domestic appliances. The ballast weight being used to counterbalance moving mass, tune out unwanted oscillations and reduce excursions..

anthonyTD
18-07-2015, 14:51
Sorry Simon,i didnt see this earlier post of yours on Patrick and his Electrofluidics speakers before posting my ramblings!
Patrick Handscombe made concrete speakers for years in the UK under the Electrofluidics brand. They were vibra moulded foamed concrete with some particulate filler. I spoke to him when building a composite loudspeaker cabinet during my degree. I ended up using an epoxy resin base loaded with rubber dust, wood flour and powdered glass. I literally made and NDT'd hundreds of sample tiles before arriving at a mix with high self damping, high mass and stiffness and available to take a great surface finish. Happy days...

Reffc
18-07-2015, 16:45
If you can see past the flowery market-speak, and usual "without compromise" nonsense (all speakers are compromised irrespective of technology or price) these are the speakers that have currently piqued my admiration in terms of thought process, the outstanding performance of the drive units used (off the shelf Accuton I think and not cheap) and of course the thought and development work that's gone into the cabinets. Nothing new in constrained layer construction but it is a breath of fresh air to see such painstaking trouble gone into design and build of the cabinet construction. Never heard a pair in the flesh (would like to) but there is a Youtube vid link below:

http://www.audioacoustics.co.uk/products/aa%20speakers/audioacousticssc.html


https://www.youtube.com/watch?v=BbIr_9P2MGo&list=PL7EAB4DCB01690266

The amp's not half bad either ;)

slate
19-07-2015, 11:55
Hmm I was pretty sure that it was during my time that the Avance fiber concrete speakers was precented; but it seems that it goes back to 1973.

Still around http://www.avance-audio.dk/about1.asp

https://www.google.dk/search?q=avance+concrete&biw=1155&bih=1003&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCsQ7AlqFQoTCLbNxdOP58YCFWu9cgodYnoLhw&dpr=1