DIY front loaded horns with Fostex FE206

[Beast_of_burden]

I have a spare pair of Fostex FE206 lying around. I did not really like them in the BLH so right now they are gathering dust, having moved on to the Lowthers in the front horns. The FE206 is similar to the Lowther in many ways and so the thought of putting them in front horns and seeing how it goes.

I want to experiment with commercial front horns that are available in Koti, Hyderabad. These are fabricated from aluminium and will need bracing with flexible plywood to stiffen them up. Before I spring the cash(700 per horn) I wanted to check other forum members if these will indeed work as a bass horn. I would have to make a circular baffle but that isnt really a problem with a jigsaw. Here are some measurements I took.

Throat area(sqmm)(r=102.5 mm) = 2073 sqmm (the FE206 might need a slightly larger baffle/throat)

Mouth area (sqmm)(r=330mm) = 342119 sqmm

Distance from baffle to the mouth = 330 mm along the curved surface( need to calculate the radius of curvature, but i dont think it was uniform like in the Tp1)

While I have been using front loaded horns in my system for a while, don't understand the math very well. This is a very large horn compared to the Tp1 Isis horn - the mouth area is nearly double. However, that isnt the whole thing, the Tp1 is 770mm wide but rectangular whereas this is 660mm and circular. The commercial horn may not go as low as the 200 Hz for the Tp1, but I would be curious to know the cutoff for this horn.

Can someone use hornresp and plot this? Wanted to do a bit of research before accumulating more stuff. Will come to the back chamber sizing a bit later in the discussion if this thread goes somewhere.

 

[Beast_of_burden]

Have been mucking around a bit on this site using exponential horn calculator.

Single Driver Website

Horn response is no longer available for download it appears.

With a horn cutoff of 190Hz and a throat of 330 Cm2 to accomodate an 8 inch driver, an exponential horn looks like this.

Exponential Contour
Throat = 330.0, fo = 190.0, sizeFactor = 1

Cm and sqCm
Dist Radius Area
0 10.2 330
1 10.6 353.7
2 11 379.1
3 11.4 406.4
4 11.8 435.6
5 12.2 466.9
6 12.6 500.5
7 13.1 536.4
8 13.5 575
9 14 616.3
10 14.5 660.6
11 15 708.1
12 15.5 759
13 16.1 813.5
14 16.7 872
15 17.2 934.7
16 17.9 1001.9
17 18.5 1073.9
18 19.1 1151
19 19.8 1233.8
20 20.5 1322.4
21 21.2 1417.5
22 22 1519.4
23 22.8 1628.6
24 23.6 1745.6
25 24.4 1871.1
26 25.3 2005.6
27 26.2 2149.7
28 27.1 2304.2
29 28 2469.8
30 29 2647.3

The mouth area of the commercial horn is actually bigger at 3421 sqcm and the mouth radius is 33 cm. Aper the calculation, the axial length is 30 cm but all I have is the contour length of 33 cm along the contour. In theory this horn is capable of going below 180 Hz I think. At 700 bucks for the horn, it is worth doing an experiment. Plan to integrate using a DCX and woofer in BR box. Let us see.

 

[kanwar]

These are fabricated from aluminium and will need bracing with flexible plywood to stiffen them up. Before I spring the cash(700 per horn) I wanted to check other forum members if these will indeed work as a bass horn. I would have to make a circular baffle but that isnt really a problem with a jigsaw. Here are some measurements I took.

With a horn cutoff of 190Hz and a throat of 330 Cm2 to accomodate an 8 inch driver, an exponential horn looks like this.

The mouth area of the commercial horn is actually bigger at 3421 sqcm and the mouth radius is 33 cm. Aper the calculation, the axial length is 30 cm but all I have is the contour length of 33 cm along the contour. In theory this horn is capable of going below 180 Hz I think. At 700 bucks for the horn, it is worth doing an experiment. Plan to integrate using a DCX and woofer in BR box. Let us see.

Commercial Horns are used for PA, there usuall cutoff is around 200Hz only, you cannot use them as Bass horns, they are only meant for vocal midrange. For a proper bass horn the throat length would easily exceed 10feet in length and you cannot make it straight for obvious reasons. Better go with folded horn.

 

[Beast_of_burden]

This is meant to be a bass horn from 200 Hz to 1KHz. Both the Lowther and Fostex FE206 have a rising response starting around 1Khz. This is the reason for their well-deserved reputation for shrieking(no kidding).

See Lowther's SPL reponse curve.

Preliminary Measurements of the Lowther DX Series of Drivers

See Fostex FE206 response curve.

http://diyaudioprojects.com/Drivers/FE206En/Fostex-FE206En-Datasheet-Recommended-Enclosure-Plans.pdf

The response below 1Khz needs to be augmented to sound balanced, that is where the horn comes in. I need it to really work from 200 Hz to ~1KHz knowing these drivers are already very efficient in the midrange and treble, hence the use of the term "bass horn". The TP1 front horns do this extremely well. See my other thread on active crossover setup using DCX2496. Below 200Hz I intend to use 95 db sensitive woofers with their own amplifciation.

Anyone who has the Fostex will know that it beams like crazy, big shifts in tonality even when you move a few feet side to side. The horns address this issue as well. Having attended enough live concerts and classical dance performances, I know what you mean by the PA sound. Truth be told both these drivers have their roots in PA. Some PA systems sound really good though, so I wouldn't paint all PA systems with the same brush.

These drivers are suited for front horn loading, thats for sure. Whether the commercial horns work is a question I set out to answer, the simulation seems to suggest they measure closely to an exponential horn and therefore it is worthwhile taking a chance.

 

[kanwar]

Better call it midrange horn, they are no way bass horns. You are after 200hz to 1khz which in pro audio field is considered as mid-range domain, not bass, correct it please.

Yes for this very range you can try the lowther & Fostex for sure. With active XO, things become damn easy to predict and control.

 

[Beast_of_burden]

Ok. I would imagine there are manufacturers of PA horns with decent build quality. The build quality of the aluminium horns a bit flimsy as the gauge used is very thin. Does anyone know where to source? Even better if the manufacturer can provide specifications.

 

[Beast_of_burden]

Not bad for a front horn that cost 800 bucks! All I did was cut out a baffle to fit the FE206 with a jigsaw. Tricky angled cut to account for the curvature of the horn, but took no more than 60 minutes. That response is with the horn being run full range. Quite good and I can tell because it sounds good, no glaring errors. I need to damp the horn surface itself, because it rings a bit. The quality of the horn is quite nice, made of 2mm thick aluminium sheet. Quite symmetrical with no obvious defects or surface imperfections. Need to add a rear chamber measuring about 3litres, right now running with the back open. Worth the effort I think, planning to get a second horn to complete the stereo pair.

On a side note, waiting for the Lyrita 2A3 SET which should arrive by the end of the week to hear the combo.

Eventually I will try the Lowther DX3s as well in these horns and see how that works out.

 

[Beast_of_burden]

The Lyrita 2A3 came home last night. This is a brilliant amplifier. Folks, I finally have attained the holy grail - Lowthers in front horns powered by a very good 2A3 SET.

 

[Rajiv]

Hi,

The Lyrita 2A3 came home last night. This is a brilliant amplifier. Folks, I finally have attained the holy grail - Lowthers in front horns powered by a very good 2A3 SET.

Congratulations on your new amp.

Pictures of your speakers and amp will be great.

Regards
Rajiv

 

[Beast_of_burden]

The speakers are a work in progress - Fostex in front horn on the left and a Lowther Dx3 in a TP1 Isis front horn on the right(shrouded in decorative cloth, this is in my living room). There is a difference in the efficiency but it doesnt matter, because the FE206 in that front horn sounds way better than the Lowther in the Tp1. The Lowther horn is wider and deeper and consequently the treble is muted, it sounds very polite(can't believe I am saying this of the Lowther). i will soon cut the baffles for the Lowthers and place them in the aluminium horns soon enough.

Live performances such as BB King - Live at Cook County Jail are stunning in this combination. These horns are doing something to the bass as well, although they roll off at 200Hz. CCR and Led Zep sound amazing, these things can rock. It is extraordinarily immersive. I will need a lot of time to pen down my impressions on the sound, but right now there is the hint of magic. The 2A3 and the big front horn are doing something quite extraordinary. In case you get the impression I am drinking my own Koolaid, my bro just asked me to build a pair of these for him. He was duly impressed within 15 mins into Live at Cook County Jail(BB's greatest record ever or what?) I will keep the Lowthers and give away the FE206 horns to him. Or maybe I will order another pair of the FE206s, depends on how the Lowthers turn out in the aluminum horns.

If you want to hear what a 2A3 sounds like combined with front horns, you are welcome to listen. As long as you have speakers such as these horns, Viren's 2A3 is a champ, I am blown away.

 

[Beast_of_burden]

Another update, I have been experimenting with the Lowther DX3(green curve) in the front horn. This might cause a storm in a teacup, but the FE206 (purple) is sounding better in the front horn. Perhaps the synergy with the amp is better, because both drivers measure very similar in that front horn.

How is the FE206 better? It sounds more balanced, more open, the cymbals less grainy and more extended. BB's guitar leaps from the mix, but never sounds harsh.

 

[kartick]

Glad you are enjoying the 2A3. I absolutely love this amp. But once I listened to this amp being powered by the Lyrita DHT pre amp, I never knew it was so brilliant. This pre-power combo absolutely transforms the sound in a magical way. Things just come alive. The DHT pre makes the 2A3 sound open and instrument separation gets improved many a times. The sound becomes crisper, more real and frequency response seems to just widen on both ends. The highs get better and so do the lows. I used to feel that just the 2A3 was restricting my listening to only one kind of music. But only till the time I paired it with the DHT. Now I almost enjoy everything with these amps. The sound has become faster and suits many more genres.

Intention here not to take away anything from 2A3's musical prowess. But to get its full potential out, just try it out in the pre power combo mode. My FE206 in BHL design seem to sound like different speakers altogether and in a good way.

 

[Beast_of_burden]

Kartick, Thanks for the tip. I have a nice Dared pre with all NOS tubes and it did make a big difference. I hadn't thought of putting it in the loop and see how it sounds. It definitely sounds more open. It sounds more extended as well. There is an all round improvement for certain. I had similar results earlier when I had paired this pre with a Wright 2A3, that was a marvellous combination too.

I need to borrow Viren's DHT pre and check it out in my system. But for now, the combination sounds just great.

 

[reubensm]

Fostex in front horn on the left

Pardon my ignorance but I am quite curious to know about the horn. You've used a regular Fostex driver with a horn, is this a DIY horn? I have seen some old generation high-frequency horns with the same approach, that's why the question.

 

[Beast_of_burden]

Regular Fostex FE206 in a midrange horn. The horn action is from 200hz to 1khz. This has the effect of smoothing out the response as you can tell from the curves I posted earlier. Horns run by the 2a3 and the woofers run by an old stereo receiver.

The horn itself is a commercial aluminium horn where only the front section has been used. The best quality horn I have seen so far is by a company called GSI, Gurnam Singh Ind.
The Fe206 in horn is run full range. The base is filled by two 12 inch woofers low passed at 200hz. As you may have guessed the whole system is bi amplified.