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Ergo Number Nine - Adventures in Micromonitor Design

Carl,

I'd never considered the KFITS risk. Let me give some thought to how this can be accommodated. My initial thinking is to come up with two sets of identical baffles, except one is fashioned from 18mm MDF and the other 25mm stock. The 25mm baffle would mount flush with the cabinet edge for naked drivers, and the 18mm version can be configured to accept a 6mm grill.

Both would be bolted onto hardwood fillets on the inside edges of the cabinets, and I can take two sets of measurements for XO simulation and design. I just hope the FR is not so significantly different that completely different XO topology is required. With any luck, it'll just be a resistor change to lift the treble output in the grilled version.

James
 
Does anyone know of a good/cheap place to get the speakers? . . . Did a quick search and found a company in the uk (cant remember the name) that want £120 for one mid bass unit.
 
fatmarley said:
Does anyone know of a good/cheap place to get the speakers? . . . Did a quick search and found a company in the uk (cant remember the name) that want £120 for one mid bass unit.
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Scan-speak has never been regarded as a budget loudspeaker driver brand. I buy from madisound.com in the USA, where the 8530K-01 costs US$202 each. Occasionally, these drivers come up for sale second-hand on eBay.

Unfortunately, there isn't another 5.25-inch driver that offer the same level of transparency and bass performance in a sealed box.

James
 
On a side note, I think I've found that elusive 15" woofer for the Ergo X. It's a brand new product from a highly respected manufacturer. It features a cast frame, paper-pulp diaphragm, around 94dB/w/m, 8-ohm impedence and best of all, it has all the right parameters to be loaded by a sealed box of around 100L.

Why does this have to happen after I had sunk a not-insignificant-sum-of-money into this micro-monitor design? The 2x10" E-VIIIs are for sale shortly.

Dammit.
 
James,
Option 2 for me too, I think a deeper box has a better look. Also up against a wall, perhaps they would fit on Linn Tukan wall brackets.

Will the naked drivers option include a leather covered baffle?

I wonder if I have enough American Black Walnut left for a pair of these :)

Ashley
 
AshleyD said:
Will the naked drivers option include a leather covered baffle?
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Ashley, you should know by now that an Ergo ain't an Ergo without leather and hardwood. Looking at the drivers, there is less than 5mm difference (if any) between their respective 'zero-delay-planes'. Hence, there is no need to recline the baffle.

I wonder if I have enough American Black Walnut left for a pair of these
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It probably doesn't help there will be an extra 100mm of width required for the boards. Given their dimunitive size, I'd say a single plank of 200mm x 3m is plenty. Are you serious about building a pair of these? Is your EBAT accreditation still current?

James
 
James said:
Ashley, you should know by now that an Ergo ain't an Ergo without leather and hardwood. Looking at the drivers, there is less than 5mm difference (if any) between their respective 'zero-delay-planes'. Hence, there is no need to recline the baffle.
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Excellent news on the leather, I really liked the look and challenge of the rounded sloping baffle, but these sound like they are going to be a very accessible project.


James said:
Are you serious about building a pair of these? Is your EBAT accreditation still current?
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Yes. Not sure if my EBAT accreditation is still valid? I'm more than willing to resit the test though.

Ashley
 
AshleyD said:
Yes. Not sure if my EBAT accreditation is still valid? I'm more than willing to resit the test though.
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I'm expecting the E-IXs to require about 1/10th the effort and perhaps 1/5th the skill compared to building the E-IVs. You're more than qualified to build them as far as I'm concerned. Making sawdust is so therapeutic.

James
 
Excellent, I'll consider my accreditation still valid. Look forward to seeing the results of your efforts over the weekend.
Ashley
 
fatmarley said:
Whats the difference between the 8530k-01 and the 8531k-01 mid-bass unit?
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The 8531 has an uncoated cone, and is a 'newer' model. It is, however, supposedly identical in specs. The 8530 has a doped cone that, to some, might look a bit too shiny to be cool. I don't care about cool. :cool:

James
 
Cheers James. Those shiny drivers would be a good match for my leather thong.

Just need to find a supplier of those Morel tweeters.
 
I managed to find enough scrap pieces of prime Black American Walnut from my very first DIY design for the E-IX cabinets. Most of the pieces were around 75mm wide, and so needed to be jointed to form boards 260mm wide. These were planed on my router table for clean and straight edges, and simply glued together. Altogether, I made up four 260mm x 195mm boards, and four 260mm x 310mm boards. The slight over-length allowed me to make mitre cuts with some latitude for error to finally get 190mm boards for the tops and bottoms, and 305mm boards for the sides.

Once the boards were cut and planed to size, I put them through my router table again to cut the rebates to accommodate the baffles and backs. The original LS3/5a design calls for 12mm stock. The walnut I used was 19mm stock. Simply planing 7mm or so off the inside edge will preserve the 3/5a frontal dimensions. Here is the rebated inside edge with the panels temporarily assembled.

6446120-md.jpg


I used biscuit slots in each to increase joint strength, but more importantly, to help with alignment when gluing the cabinets up. Here is a mitred corner with biscuit slots just before I applied glue and headed down the path of no return:

6446121-md.jpg


I checked that they will assemble neatly together and square. Seemed like a good photo opportunity before it got too dark, so here is the first look at the cabinets in mock assembly sitting atop my Triton routing table.

6446110-md.jpg


James
 
Gluing is not my idea of fun. Even with biscuits in place, it's a royal PITA to get all four pieces exactly where you want them, make sure the cabinet is square, and get it all done before the glue sets. Anyhow, they are now done, bar the sanding down of the jointed edges to remove all traces of squeezed out glue and slight unevenness.

Earlier I pondered if I should have offset tweeters to diffuse edge diffraction over a wider frequency range. This is how offset tweeters might look. Of course, they will be mirrored as L and R handed pairs.

6446125-lg.jpg


Straight up, they look a bit more normal like this:

6446126-lg.jpg


I haven't decided yet which way to go.

The drivers look very much at home and proportionately sized. The deeper box also gives a sense of solidity and purpose. I will need to figure out how resonant the boxes are without any bracing. I don't have any fancy accelerometers, so a knuckle test will have to do. A higher pitched knock is supposedly better than a low pitched thud. As walnut is rather stiff and hard, it's already pitching rather high, so to speak. Here is a couple more pictures before I call it a night.

Brand new shiney drivers spatially located in an unfinished cabinet:

6446119-md.jpg


The newest baby Ergos being looked upon by its slightly bigger sibling, the Ergo E-VIIs.:

6446117-lg.jpg


Tomorrow, I will cut the baffles and sand the boxes down in preparation for a good lathering of Danish Oil.

James
 
Super work James, I wish I was that quick with the box construction.

Personally I prefer the tweeters offset. Makes the speakers look a little more quirky (hang the sound!), lol. I know that the Specials have offset tweeters as part of the OB design, but that configuration doesn't look out of place.

Where's the xover going to go?
 
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