The NORGE speaker build

[Toppsy]

OK, a few of you may be aware of the new speakers I have been developing that I posted up a photo of the prototypes on Steve's `Next Owston 1-2 November 2014' thread http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=5662 , so for those who are interested here is a new thread on their build and development.

A little background info - As stated these were originally intended by me as an indulgent personal build that on paper at least showed great potential and partly was a result of searchers Scott and I were doing to find a suitable alternative replacement 6 mid woofer for a MKII Edingdale. We were doing this exercise should a new production run of the original Mark Fenlon (MarkAudio) mid woofer drivers not happen. The drivers in these new speakers was one of the, shall we say, more expensive alternative drivers that caught my attention. This is a state-of-the-art design 6 mid woofer driver using Egyptian papyrus paper cone, cast aluminium chassis, low distortion neodymium motor and advanced BIMAX spider. FR plots suggested it was good up to 5 KHz with sensitivity (2.83V / 1m) of 87.5dB and rave reviews on the driver from the forums were very good. So the new speakers would therefore be as efficient as, if not a little more than my original Edingdales but had the potential to be better. More on this later, hey

As an aside Mark Fenlon recently visited the UK and he popped in to Topps' Towers to pay Scott and me a visit, have a chat and have a listen to our speakers using his drivers. So impressed was Mark with our efforts that we are now confident there will be a new 6 Markaudio mid woofer driver coming our way. Not the same driver but a better more advanced design over the original used in the Edingdales. More on this will be posted in a separate thread when we have any update info.

As part of the search for replacement Edingdale mid woofers Scott also researched alternative tweeters. It was at this time that Monacor announced a new range of true ribbon tweeters and one of these just looked to me like it was a perfect partner for the papyrus cones drivers, so I placed an order for a couple pair for experiments. These were tried originally on top of my original pair of Edingdale speakers with the pseudo ribbon removed; the cut-out blanked off with gaffer tape and the new ribbon simply wired to the original XO. Not ideal, but this showed me just how good the new ribbon was and so I asked Scott to come up with some basic designs for me to draft into suitable cabinets.

I perhaps should say where the name NORGE came from. The name comes from a touring Moto Guzzi motorbike that I lusted for when it first came out and wanted to swap for my Aprilia ETV 1000 Caponord but could never justify the additional spend. During a telephone chat with Scott I happened to mention this whilst we were thinking of suitable names and Scott said that name works for me and so the name stuck.

More to follow...............................

[Toppsy]

Scott sent me a few alternative cabinet alignments and port tuning frequencies for consideration.

I have for while fancied building a pair of curved speakers so using the different cabinet volumes Scott sent me got to task with AutoCAD and eventually settled on a design using a volume close to that of the original Edingdales.

Being prototypes and curved, using a true elliptical curve, I designed the cabinets to use frame and stringer type construction with 3 layers of 5mm thick flexible ply wrapped around the formers. This makes for a very strong, light and rigid structure. My thinking being this would be the easiest and likely cheapest way to make a 1-off pair of speakers should a second pair of prototypes be needed should the originals disappoint? Frames are CNC machined from 18mm BB ply, stringers from 18mm BB ply cut on my table saw and 36mm thick base also CNC machined from 18mm BB ply to add some mass. The front baffle is made from 30mm thick BB ply I had in stock from an earlier project that didn't live up to expectations and was eventually abandoned.

Here what most have perhaps been waiting for some construction photos:











Choosing a suitable impressive but not too expensive a veneer I chose to use Decoflex American Black Walnut veneer with the veneer grain horizontal wrapped around the elliptical curve sides. This really gives definition to the curved shape. Here is a couple of photos before the driver rebates are routed in the front baffle and before finishes.



More to follow.....................................

[Ali Tait]

Very nice Colin, look great.

[Firebottle]

A very attractive shape and finish. Hope the sound is top notch as well,


Cheers, Alan

[Toppsy]

I chose to finish the veneer in my usual Liberon Finishing oil and then applied a coat of General Finishes High Performance Gloss topcoat. This is a water based top coat finish that gives the durability of a urethane varnish but with added UV protection. The decoflex was ironed on using Titebond original wood glue applied to both the backing of the veneer and the ply cabinets. This gives a fusion bond without having to resort to vacuum press or such like. I'm not too chuffed with the end result as after applying the top coat I noticed some air bubbles under the veneer that are near impossible to remove now. I think this was a result of using the flexi ply wrap around method of construction as unless one applies even pressure to every band clamp wrapped around the flexi ply when gluing up the ply can compress in parts where there is open frame below the band strap. A lesson learnt here for future reference. Still these are only my prototypes after all and can only be noticed at close range and in the right light conditions.

Here are some photos of the finished speakers. Having said the above unsatisfactory results on my finish I must say the end result is rather pleasing on the eye and they do sound as good as they look.





For those that notice the small whitish spots on the driver cones these are not dust or dirt marks but a feature of the Egyptian papyrus paper the cones are made of.

Last week Scott came over to my place and we had the intention to measure the drivers with the AudioTester software program that NickG uses to measure is gear together with an external plug in M-Audio Transit soundcard and my measuring mike with phantom power supply. However, we found my laptop not up to it. I think my processor not up to the task and perhaps it is time to replace my over 5-year old laptop with a new model. So disappointed that we were not able to measure the drivers in cabinet Scott went home with the view the manufacturers data sheets could be relied on to make a first stab design at a suitable XO. This he duly sent me the beginning of this week and I took to task to make them up. Fortunately I had all the values of the resistors and caps in stock but had to wind off a few turns of available inductors to get to the correct values.

Well Tuesday afternoon this week I duly fired them up through my 300b SET monoblock amps and using CD as source sat down to be startled by just how good these speakers sounded. So good were they that I spent the rest of the day sat in front of them until 11.30 at night when my wife requested I either switch them off and come to bed or turn the volume down low so she could get to sleep. So I reluctantly switched off and went to bed a very happy chappie.

I reckon that even though the drivers are still running in these are the best speakers Scott and I have done to date bar none! They have a coherence of sound that draws you in. What impress's most is the clarity of sound and the richness of the midrange and bass. I am hearing sounds in the background of the mix on songs I am most familiar with that I haven't noticed before. They project the singer into the room like none of my (our) other speakers. I know there is a tendency for folk to get over excited about their new builds and perhaps I may be over enthusing about these so I invited Chris (stratmangler) for his opinion. He came over yesterday afternoon and though I don't want to quote him here (I'll let him do that for himself) I believe he went home very impressed.

There is still work to do on these speakers. When Scott, Nick and I go up to Scotland to stay with Andrew for our annual boys weekend bash I'll hook them up to Andrew's laptop and we can measure the drivers and them measure the speakers with the XO as is to see if we need to make any minor changes. So they are not a finished product yet, but so pleased am I of the results to date these are definitely going to be made available commercially but with different manufacture cabinets and slightly different cosmetic finish. From my experience building these the way forward is definitely to use a translam form of construction with veneered sides and top and a leather clad front baffle with rounded over sides to meet the elliptical curved sides.

[Toppsy]

To give perspective to the size of the NORGE speakers I have attached a photo of them alongside my original build Edingdale speakers.



As one see though the front baffles are the same width they are little wider overall due to the curved shape to get the required internal volume. They are also a tad taller to accommodate the larger true ribbon tweeter.

[pre65]

I wish you and Scott every success with them Colin.

[chris661]

Those look really good.

To get the veneer to sit flat when gluing, I've seen folk on diyAudio put another layer of bendy ply over before putting the straps round. I'd expect the wood to even out the pressure nicely.

Is it a two-way design, or are the bottom 2 woofers crossed lower for BSC?

Chris

[The Stratmangler]

... so I invited Chris (stratmangler) for his opinion. He came over yesterday afternoon and though I don't want to quote him here (I'll let him do that for himself) I believe he went home very impressed.

I think they're the best build you've done yet Colin, and they'll only get better as you clock up the playing hours and the drivers bed in.

The experience was a bit like listening to full range Quad ESLs with nuts.
Seriously, seriously good stuff!!!

[IslandPink]

Where's Dave gone when you need him ? ....

Shoddy

[Andrew]

Very shoddy!!!!!!!!

[Toppsy]

chris661 wrote

To get the veneer to sit flat when gluing, I've seen folk on diyAudio put another layer of bendy ply over before putting the straps round. I'd expect the wood to even out the pressure nicely.

Good tip Chris. However that would mean buying an extra sheet of flexi ply but likely would get over the issues I had. All good learning stuff though.

Is it a two-way design, or are the bottom 2 woofers crossed lower for BSC?

Chris it's a 2-way same as the Edingdales.

[Dave the bass]

MEGA-SHODDY!

Apol's for lateness of abuse!

DTB

[Toppsy]

chris661 wrote
Quote:
To get the veneer to sit flat when gluing, I've seen folk on diyAudio put another layer of bendy ply over before putting the straps round. I'd expect the wood to even out the pressure nicely.


Good tip Chris. However that would mean buying an extra sheet of flexi ply but likely would get over the issues I had. All good learning stuff though.

Of course if one was doing several curved speakers using this method of construction you might want to consider buying one of these: http://curvomatic.com/ Not cheap but would pay for itself in time and would save a LOT of aggravation.

DTB
Thanks for the thumbs up. Better late than never mate as they say. About time you built another pair of speakers hey Been a long while since one your build threads to keep us entertained.

[Ray P]

chris661 wrote
Quote:
To get the veneer to sit flat when gluing, I've seen folk on diyAudio put another layer of bendy ply over before putting the straps round. I'd expect the wood to even out the pressure nicely.


Good tip Chris. However that would mean buying an extra sheet of flexi ply but likely would get over the issues I had. All good learning stuff though.

Of course if one was doing several curved speakers using this method of construction you might want to consider buying one of these: http://curvomatic.com/ Not cheap but would pay for itself in time and would save a LOT of aggravation.

Colin, very nice speakers.

Look out for a used vacuum pump on ebay and buy some large vacuum bags; a lot less than that device and no more air bubbles! I use a vacuum pump occasionally for laminates so have a little experience and can point you to supplies.

Ray