Half wave horn project.

[bobhayes]

Finished this fe166e project recently, and have been going through the music collection to test 'em and break 'em in.
Length is 3.75m (just under half resonant wavelength of fe166e), throat size is 0.0086 sq.m (13.3sq.in) or 0.65*Sd. Mouth is 0.14sq.m (231sq.in)
Expansion is something like half way between conical and exponential.

On first listening, I thought the cymbals sounded really horrible like dolby C, totally compressed and mechanical sounding, but with a few hours they've really smoothed out. I guess this is the coupling between the main cone and voice coil/whizzer loosening up? I see why these drivers require a long break in. The bass response seems to have improved too, not so much the extension, they've more like 'mellowed', for lack of a better description.

I can't see why you would need a T90A tweeter with these as the treble seems balanced to me, but I suppose I wouldn't miss them until I tried them!

Overall, I'm really happy with the result. The bass extension is great, and the Fostex drivers sound dynamic and very open right accross the frequency range.

There's a picture attatched for anyone interested. I priced Jarrah veneer, but thought better of spending more on the finish than the drivers, so my lass painted them in 'suede' effect textured paint and I really like the finish. I think timber veneer might have made them look a bit overpowering.

[Josephjcole]

Congrats! they look great. Care to share any construction details?

[Cortez]

Congrat too ! I have also fe166 speakers, but my horns are smaller. (ca 2m length)
Did you maybe measure them a little ? I mean speacially the bass region.
How deep they go ? It looks a little like an expanding TL, do they resonate on upper harmonics ?

[bobhayes]

Josephjcole,

They are MDF (not ideal but it was free!) and stand 1500mm tall.
They are built similar to any regular horn, trapping baffles and partitions between sides, except the baffles are all tapered and the curved sections at top and bottom are sectional (10 pieces for the top curve and 5 for the bottom) then sanded round. The side panels are single pieces with a saw cut from the bottom, to just short of the top and from behind the speaker to just short of the bottom, with a slight twist introduced to maintain the tapered shape.
The chamber is also sectional.
There is another unseen panel inside part of the back section of the flare to maintain the flare rate and brace the larger panel areas down the back.
I can supply drawings if you like and a photo of the cabinet before the side went on. I still need to add a little dowel

Cortez,

I havn't measured the response, but I run loads of albums through them including a great CD by 'No Doubt' called 'Tragic Kingdom' by them, which consists of a whole album of songs with musical running bass lines, and there are a couple of minor peaks and dips in the bass response, but nothing invasive. There is however a more noticable peak higher up in the lower midrange which I'm investigating. It could be panel resonance around the under braced mouth area, or just a peak in response due to the horns comb effect. It's only noticable very infrequently on certain vocals, and it doesn't bother me that much. I might try a bit of stuffing, but don't want to suck the life out of them.

What cabinets are your 166's in, and how do they sound?

[Cortez]

I can supply drawings if you like and a photo of the cabinet before the side went on.

Yes, we want it !

There is however a more noticable peak higher up in the lower midrange which I'm investigating.

Based on my experiences its caused by the compression chamber's reflections.
Try to get the speakers out, and then shout loud to the chamber on all kinds of tones.
You could seal the throat, and when the peak is still there, it isnt the horn.

I might try a bit of stuffing, but don't want to suck the life out of them.

Yes. Now whats with the stuffing ? Where did you put them ?

What cabinets are your 166's in, and how do they sound?

I tried 3 different horn, with roughly the same size (100x40x20cm), but the results were also similar.
They sounds not so bad, but the bass isnt enough for me.
Therfore now, i am interested on acoustical tricks, like more chambers in the horn to solve my problem...
But who knows, maybe its easier to put some bass-gain in my GC through the feedback...

[planet10]

Beauty.

We'd love to see more pics & some drawings.

dave

[brettleasure]

thats awesome, im currently in the process of building a pair like these. ill try to post some pics up when i get a chance. and yes, id like to see drawings as well

[bobhayes]

I'm waiting to use a friends camera to post reasonable j pegs of the drawings as mine doesn't show the dimensions very well.
Here's a picture from mid contruction.
The heavy glue mark is for the internal side bracing/ flare contour corrector panel.

The segments for the curves were not installed at this point, but you can see the general outline.

The side panels are about to be 'nipped in' to the narrow front part of the bottom panel.

The contruction isn't really that compicated, it's just cutting the chamfered segments for the curves that's a bit tricky, but cutting long strips with a 10 degree chamfer both sides, using a rip saw with guide fence quickly makes all the segment angles in one hit. (15 degrees for the bottom curve segments)

I'll post drawings soon.

[bobhayes]

Ok, I went over the drawings in pen to make them show up better.

The one attached is the assembly drawing.

Note that the first part of the horn (around E) is shaped to fit the finished compression chamber, so I left a bit extra on the relevent panels and pared them once assembled with sharp chisels. (Easy with MDF, harder with ply!)

I also fabricated the chamber parts into an open octagonal shaped box braced with the speaker panel and later cut the back angle to mate up with the cabinet upper front panel, if that makes any sense.

I didn't fit the mouth deflector panels as I haven't decided on this area yet.

Hope the pictures show enough detail. Anyone is free to have a go at these as I designed them. I can answer any questions you might have about the construction, but don't ask me what the phase response is like, as my scope and test gear still reside in the UK.

[bobhayes]

Here are the drawings for some of the parts.

I cut the curved segments out of one rip of material, then individually cut them to fit between the side panels to make up the curve. A small fillet was then cut to fill the small gap left at the end of the curve.

Also, I left the speaker panel oversize and edge trimmed it with a router to the octagon shape before centering and cutting the speaker hole.

Next post is the last drawing.