The "Feils" ...A rookie LCR 3way build - diyAudio
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Old 29th January 2010, 11:48 AM   #1
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Red face The "Feils" ...A rookie LCR 3way build

Having travelled a long prelim of minor pre-projects before actually reaching a point where I felt starting a build thread was warranted. I present to you....

The Feils
a horribly ill-conceived rookie build

Current progress:
Click the image to open in full size.

"feil"... a Norwegian word meaning eg; mistake, wrong, incorrect, miscalculate. You get the idea... Whether or not the proper pural is feils, I don't know, but trying to come up with a name that sounded ok and summed up my misguided ambition accurately was tough. So I'm going to take some liberties with unknown foreign grammer.

A brief history:
..Just shy of two years ago, I was informed of my impending fatherhood. This of course forced me to re-evaluate my lifestyle, and more improtantly, my spending habits. So for some reason I thought diy speakers would be a good hobby

The Logic:
..In an effort to keep costs down I thought I'd reincarnate some components from my car audio days, and give them a shot at a HT LCR set-up. Behold the Diamond Audio DA6.6.
Click the image to open in full size.
Click the image to open in full size.
..and the LPG 25NFA
LPG 25NFA 1" Textile Dome neodymium magnet Tweeter from Madisound

Where I jumped the shark:
..HTGuide Forum - Matching drivers...beyond the specs
Not that posting for advice at another site was a mistake, but it definately got the ball rolling to has become the feils.

The advice I did receive over there did push me away from the LPG tweet, and into something that would play low enough to take the DA6.6 breakup out of the equation. Enters the SB29 Neo. SB Acoustics SB29RDCN-C000-4 Neo Magnet, Ring Dome from Madisound. I also decided to go the route of the DA5.6 for the mid. Not that either was necessarily the best choice, but the 5.6 are relatively cheap considering the Eton lineage ~$50eac, and the SB Neo has been getting rave reviews. I do have a hand written T/S spec sheet for the DA5.6 provided to me by Eton. Great people to deal FWIW. I'll add it in later today when I have access to the file.

As it is... The woofer inclosure volume is approx 10l shared, and the mids get <1.5l shared. The enclosure is of a translam/traditional construction and has the rough dimensions of 28"x8"x8". The cabinet pictured above is strickly a "trial" version for sake of experimentation. Anything and everything can be changed, so suggest anything you wish. I guess it should be said that the the Feils are intended to be used with a powered subwoofer, so response down to ~90Hz is only being considered in the LF design.

I will be bringing this thread up to speed over the next 24hrs, but please feel free to comment on anything you wish.

Stay tuned....

Last edited by smokinghot; 29th January 2010 at 11:53 AM.
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Old 30th January 2010, 03:52 AM   #2
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So the first problem I set to rectify was the flange that Diamond Audio choose to use with these drivers. Keeping in mind these drivers were designed to be used within a car. The composite basket was formed with a enlarged flange that held the protective grill in place, (see pic in first post). This makes perfect sense for a driver that would most likely end up in the kick panel of a car, but not so much for home use where a flush fit to the baffle is desired.

The simple part of the plan was to remove the unneed part of the flange at work using the machine shop's lathe. Why the lathe..? Well for one, I wanted repeatable accuracy, and two, I like having excuses to play in the machine shop The difficult part (and the reason for the accuracy) was fabricating a new flange that would be epoxyed to the remaining portion of the driver. What remained of the flange after the removal of the grill retainer was not all that visually appealing, and I wanted something would flush fit nicely in the yet to be conceived baffle. I considered a few different types of material to make these flanges. Aluminum, ABS, nylon..., and ended up with a Phenolic/Garolite board from McMaster-Carr, which is essentially fiberglass board cured under pressure. This allowed me to manufacture very thin, and very strong replacement flanges, in any fashion I chose.

I cut down the sheet of garolite down to manageable squares of approximitely 8"x8" in size. I then mapped out, and drilled the hole pattern for the DA5.6 on the smaller sheets. I made a jig out of aluminum and good sized bolt so I could machine the garolite on the lathe.
Click the image to open in full size.

For some reason, I can't seem to find the flange build pics I took during construction But here is one of the both the new 6.6 and 5.6 flanges along with the jig. I managed to fab up both a 6.5" and 5.25" flange out of the same sheet. Unfortunately that didn't allow both pieces to be identical proportionally speaking. Considering the cost of the garolite, I think it worth the scarifice.
Click the image to open in full size.

Once I turned the rough garolite into the desired dimensions on the lathe. I then took to the mill to proceed with countersinking the holes for mounting. The tapered edge of the flanges made using a standard drill bit next to impossible. A mill end would also leave a flat surface to allow the mounting bolts a even area to apply the maxium down force when installed.
Click the image to open in full size.
Click the image to open in full size.

The end result was a press fit shallow waveguide for the LPG, and what I like to think are fairly nice looking and functional flanges for the 6.6's, and 5.6's. It took a little trial and error to find a paint colour worth keeping. I ended up with a Tremclad "textured" product. RustOleum.com As you can see it blends very well with the drivers.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 30th January 2010, 06:07 AM   #3
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Usually, (at least from what I have gleened from the many build threads I've read through) the enclosure size and baffle layout are a result of extensive response sims (unibox,BDS,FRC) some using the T/S specs of the drivers in use. That may be so in the world of the wise diy'er, or even the ones smart enough to listen, but did you catch the part of the title when a I stated it's a rookie build..?

The current dimensions and baffle layout of the Feils, is totally based on aesthetics. Yes I have played with the aforementioned excel spreadsheets. However since I took to this hobby as a method of filling in my expendable time, both at work and at home. I thought the much longer and less traveled road of blue collar Build/Test/Rebuild, would be fun. I'm not knocking those spreadsheets by any means. I guess I'm just of fan of trial by fire. Jump in head first and see if you can make it out alive, and with something worth showing for it.

As it is, the outer dimensions of the Feils is designed on what would fit the best around my Plasma Ya, ya I know, but it had to start somewhere. I also wanted to test my cabinet fabrication skills, so I went the route of Translam. Well not completely Translam... From all the comments I've seen on the construction type. The only complaint seems to be the wasted material. So I thought I try a slightly different approach. Meet the rib jig..
Click the image to open in full size.
I used this little guy to fab up roughly 60 ribs, which would (after assembly) make up the sides of the Feils. The idea was to minimize waste by having multiple pieces make up each layer of the translam. The smaller pieces would of course be placed closer together on the virgin sheet of construction material...closer proximity=less waste. Was it worth it...? ....not at all

After many, many hours on the router table. I finally had enough 'ribs' to reach the minimum height to accomidate the WMTMW. These ribs were obviously laminated together into what could not be better described than a "rack". (get it..?.. rack of ribs) Anyway, gluing the ribs together was extremely difficult. An air finish nailer was used to keep them semi-aligned in groups of five, and those sections needed excessive weight along the rack's length to stop them from blowing apart while being clamped. The plan was to use the typical single sheet for the front, but also utilize the same method on the back. The completed 'racks' had dados cut into them to help align the front/back pieces. Here's a couple of shots of the front plate being attached.
Click the image to open in full size.
From this angle you can see the angle iron used to provide an even pressure along the length of the 'rack of ribs'
Click the image to open in full size.
Although I thought I had the ribs braced squarely enough when I did my dado cuts. Their badly squared edges showed up when I attempted to install the back plate. The remedy..?...the mill
Click the image to open in full size.
A couple of very light passes gave me the square edge I needed to glue in the back plate properly...whatever that is.
Click the image to open in full size.
The fit between the back plate and the ribs was so tight after the work on the mill. The section was held in place by friction alone . However, one aspect of installing that back plate from the inside out I didn't consider was clamping. No prob... Cut some precision blocks and slide them into place after the glue has been applied. That's fine in theory but what if the center height is slight taller than the height at the ends. Lets say roughly a 16th" The solution....
Click the image to open in full size.
yeppers... my car jack
So if you're foolish enough to mimic this part of my build. First apply glue on both pieces, put into place. Insert and raise car jack...
Click the image to open in full size.

More to come....
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Old 30th January 2010, 07:31 AM   #4
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Well done smokinghot. A great thread with a great sense of humor.

Keep having fun, cant wait to see the end result.

Dean
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Old 30th January 2010, 08:59 AM   #5
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Thanks Dean... If nothing else, I've certainly learned what to avoid the next time around.

Speaking of avoiding... If you find yourself using a mill/fly cutter combo to true up the end of your enclosure. Be sure to check the grub screws that hold the tooling in place
Click the image to open in full size.
Sure it doesn't look all that menacing now, but trust me when I tell you that once it gets spinning over 2800rpm. That chunk of carbide tooling is doing everything it can to bury itself into your chest. As it so happens, the patron saint of diy (whoever that is) was watching over me that day. That carbide bit, with all that pent up centrifugal force, somehow wiggled free of the fly cutter and split the uprights...(aka: the 12" gap between the cabinet and my chest). It took about a hour to find the damn thing, and about 2 more to calm my nerves enough to get back at it....

At that speed however, it does do a fantasic job of triming MDF.
Click the image to open in full size.

With the ribbed and flat panels all "squared" to each other, I proceeded to add 3 one piece laminate layers to each end of the enclosure.
Click the image to open in full size.
The last of which was to be removeable. Just to cover the bases as far as access to the internals.
Click the image to open in full size.
I know it looks odd that I'm taping MDF, but trust me that little amount was more for keeping the inserts straight during installation more than anything else. I glued them in heavily, and they're surprisingly robust. (at this time I'd like to remind you that this is a "trial" enclosure and will never be upgraded beyond that status. I don't suggest using threaded inserts as depicted)

So now that I have a sealable enclosure, I needed to determine the internal volume so I could play with some white collar spreadsheets . After quickly dismissing the plastic liner and water idea , I went with what I had handy. Plastic resin... ...and my wife's measuring cup (sorry hon)
Click the image to open in full size.
Up to the brim, and the resulting volume is ~14liters. For anyone considering a dry filler for this kind of volume measuring. Be sure to lightly tap all sides of your enclosure to allow the particulate to settle. I easily got an additional 200ml doing this.
Click the image to open in full size.

So now I have finally reached the point where I need to consider driver spacing. So far in this thread I've actively played up my haphazard approach to this design, but I did ponder the MTM configuration for quite some time. I was torn between achieving a straight line source for the L/R speakers, and visually matching the center channel. Which would suffer from the extra distance between the mids if they were spread apart the full width of the tweeter. Of course their crossover point plays into that equation as well, but who has a glue where that's going to end up . In the end, I reminded myself that this was indeed a "trial", and basically picked the happy median.
Click the image to open in full size.
(the pancake air cylinder was the closest thing in dimensions to the SB29 that I had on hand)
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Old 30th January 2010, 09:35 AM   #6
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Hi SH
Excellent construction stuff. Looks like you have access to a lot of tools!
Custom dress rings are very cool too.
thanks for sharing
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Old 30th January 2010, 03:10 PM   #7
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Very nicely done!
The box volume is on the low side (should be closer to 30 litres for 2 of those drivers and ported if possible) but they look good.
I have a similar problem on a woofer I'm using and need to do a similar fix but I think I'll leave the driver as is and construct the trim ring to fit.
Keep up the good work
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Old 31st January 2010, 01:00 AM   #8
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Thanks MJL... I have been told that the DA6.6s would benefit from a larger volume before. However I did do some work in unibox and didn't see the benefit in >doubling the overal size of the Feils based LF extension that isn't needed. I definately see version 1.1 of the Feils increasing in size, but that's more for some extra breathing room on the baffle than anything else. Size really does matter in this project, and at the absolute most the Feils will max out at 20liters.

Here are a few "sealed" sims I ran in Unibox to compare DA6.6 response based on volume.
Click the image to open in full size.

I do get a 2db rise with the 10liter volume before the nose dive below 100Hz. My original project goals were to include a powered sub-woofer to handle material below 100Hz. So I figured I'd allow the Feils to naturally roll off and then actively bring in the undetermined sub-woofer to smooth out the bottom end.

However, if you think I'm missing something or my line of thought is out of wack, please describe the benefits I could expect from increasing the volume.
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Old 31st January 2010, 01:30 AM   #9
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Quote:
Originally Posted by smokinghot View Post

However, if you think I'm missing something or my line of thought is out of wack, please describe the benefits I could expect from increasing the volume.
You need to look at the peak cone excursion. That doesn't improve any with a bigger box but you can't give these much gas before they run out of linear excursion: something like 20 watts max if you don't use a high pass filter (@ ~110Hz).
Using a separate sub is a great idea because you are not going to get much bass out of these at all.
My advice would be to not let these naturally roll off (previously mentioned excursion problem) and limit the low end to 120Hz. You could then build a (sub)woofer that would handle everything from 120Hz down.
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Old 31st January 2010, 02:50 AM   #10
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Quote:
Originally Posted by MJL21193 View Post
You need to look at the peak cone excursion. That doesn't improve any with a bigger box but you can't give these much gas before they run out of linear excursion: something like 20 watts max if you don't use a high pass filter (@ ~110Hz). Using a separate sub is a great idea because you are not going to get much bass out of these at all.
I believe that's why the specs suggest 7liters sealed each. Maybe the lower volume helps control over excursion..? Anyways with a Xmax of 2.5mm and sensitivity of 88db , I wasn't expecting much, and it was the driving force behind doubling up to the WMTMW.

Those same weak numbers were reasoning behind the intended application. A small scale HT LCR seemed like the best I could hope for. Going in knowing that a sub-woofer would be needed.

Quote:
My advice would be to not let these naturally roll off (previously mentioned excursion problem) and limit the low end to 120Hz. You could then build a (sub)woofer that would handle everything from 120Hz down.
Good think'n...
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