back loaded horn project for se 2a3 (~3W)

[makar0n]

hi,

my name is Lukas and I just started a double project. I would like to build myself a single end 2a3 amp (and this part looks fairly easy. I have blueprints and a soldering iron 😀).

the second part of the project are loudspeakers ( I slowly start thinking that loudspeakers should be the first part 😉 ).

because amp will be on the lower site of the force (~3W), I need very sensitive loudspeakers. at first I thought about fostex 206en, but fostex have a lot of adverse opinions.
then I chose tang band w8-1772 drivers as very similar but without bad shadow.

now, could you please help me to find a nice blh cabinet project for tang band w8-1772 drivers?

if it will be free of charge - excelent, but I can pay for plans some (reasonable) money.

I found a manufacturer's (tang band) project of blh cabinets, but I do not quite like it. I would like to build speakers like: dallas II, jericho horn (both for fostex 206), signature two (lowther), etc.

some information:
room size: 3x4m
speaker sizes: width up to 400-500mm, deep - even more, seling is on heigt 2400mm 🙂

I do not know what other info is needed. tell me please and I will provide it.

Lukas

 

[planet10]

The TB are not nearly as efficient as the Fostex... about 4 dB by my measures.

And i don't know how suitable it is for a horn.

dave

 

[makar0n]

that's a point, but fostex need an extra high frequency driver = crossover.
I would like to avoid anything between amp and driver if possible.

what driver would you suggest? apart from forstex and tang band. and cheaper than a small car 🙂.

 

[planet10]

that's a point, but fostex need an extra high frequency driver = crossover.

No more than the TB. The Fostex has some annoying peaks, the source of the so-called Fostex shout, We treat/modify the drivers to get rid of the worst of that. The TB is smoother.

what driver would you suggest? apart from forstex and tang band. and cheaper than a small car 🙂.

You might consider the Mark Audio Alpair 12p. A touch more efficient than the TB, but the Alpairs efficiency always seems to belie how much power you can get away with. And there is a good horn for it.

Woden Design | Avebury

Same site has a similar horn for the FE206

dave

 

[makar0n]

The Fostex has some annoying peaks, the source of the so-called Fostex shout, We treat/modify the drivers to get rid of the worst of that.

could you please paste a link to methodology of this "treatment"? I am very interested.
but still, price of fostex supertweeter is

You might consider the Mark Audio Alpair 12p. A touch more efficient than the TB, but the Alpairs efficiency always seems to belie how much power you can get away with. And there is a good horn for it.

alpair seems to be the weakest in effiency 😕
all from datasheets

alpair 12p 91.73dB
fostex 206en 96dB
tb w8-1772 95dB

Woden Design | Avebury

I like it 🙂. but 89dB ... will it be enough for ~3W midget?

Lukas

 

[planet10]

alpair seems to be the weakest in effiency 😕
all from datasheets

alpair 12p 91.73dB
fostex 206en 96dB
tb w8-1772 95dB

TB measures just under 92. Alpair much the same, Fostex just over 95.

TB is noted for fairly variable specs depending on the batch, and in this case stretch the reality by hand=picking the point they use to specify the efficiency

dave

 

[perceval]

I have the W8-1772, and I built Bob Brines' design and it is nice, but it needs a bit of EQ to shine in my room.

If I had the space, I would try the WIBAQ, which is a TABAQ on steroids!

http://www.diyaudio.com/forums/full-range/226767-wibaq-tabaq-design-betsy-k.html

 

[freddi]

planet10 has a good description of W8-1772 - imo, its smooth, well damped (maybe overly for some tastes) and sounds "hi-fi" - something like a well executed 2-way - but sometimes I prefer FE206EN even with its hard peak as I use Karlson. A 2a3 probably needs close to a real 100dB speaker to shine . 1772 could use 20 watts or more. 1772 seemed to like the old BK20 small blh - but I didn't take measurements. Alpair are considered to be good alternatives.

 

[Scottmoose]

1772 in the old BK20 would be an interesting option -it's going to be undersized for the driver requirements & since it's not tuned especially low, that will likely result in not a lot happening on the bottom end, but a fair old kick through the mid & upper bass region.

I don't mind the 1772. It's a sort of avereagely average Mr McAverage widebander. Doesn't do much objectionable, but nor does it particularly excel in any areas. It wouldn't be my first choice, but it looks nice, if you like that kind of thing, and does a solid enough job. I prefer the Fostex & MA units mentioned, but YMMV as always -different strokes for different folks & all that.

If you want to get the best from the 1772 (or take it low), then as far as back-horns go, it requires a fairly substantial enclosure given its moderate Q and Vas. That applies to all drivers of course -up to a limit (which is usually far beyond what most people are willing to tolerate anyway) bigger is better when it comes to horns. But with those specs., it tends to be larger than some others, especially when you factor in the output impedance of your proposed 2A3 SET amps, which is likely to be high -presumably in the 2.5 - 4ohm region or higher, which puts the necessary enclosure size up again.

 

[chrisb]

Well, here's a concept drawing of one that I built for a local guy - his design, and he quite loves them. I'm not such a huge fan of the driver myself - have heard them OB in a 3-way with JBL 2225* and Dayton AMT Pro4 tweeter, but not yet in this particular design. Not the tiniest of boxes, wider and approx same height / width as the SuperPensil for 12P, which if I had the space, I'd choose over the TB, or Fostex 206.

*now, that's a decent woofer, folks

 

[GM]

because amp will be on the lower site of the force (~3W), I need very sensitive loudspeakers.

room size: 3x4m
speaker sizes: width up to 400-500mm, deep - even more, seling is on heigt 2400mm

OK, where will the speakers, listening position [LP] be?

How loud on average do you want them to play at the LP?

Without this and the amp's output impedance, there's no way to know how efficient the speakers need to be at minimum.

GM

 

[chrisb]

Not a huge room, actually - if not a floor plan that opens into larger space such as dining room/ kitchen etc, you might find that a driver of approx 92dB sensitivity, and 2A3 amp ( a pair of which I've owned for over 10yrs) is surprisingly satisfactory, and with well matched MLTL design, generally "easier" builds than BLH - although as pointed out earlier, not necessarily much smaller- should be on your radar screen.

I've heard the 3 drivers cited in your initial post - actually in the case of the Fostex, including the 206ESR in monstrous BLH, driven by Welborne Labs DRD 45, approx half the power of 2A3 (that's a flea-watt amp for ya, but quite gorgeously detailed, and surprisingly dynamic ), and to repeat myself, would take the Alpairs over the others.

 

[atilsley]

Could go with something exotic for the Fostex or TB....

C-Horn designed for 8 inch driver, 3M length horn path...CNC access is needed....and you could save a few bucks if used ply or MDF sides instead of the 25mm acrylic.

Andrew

 

[makar0n]

TB is noted for fairly variable specs depending on the batch, and in this case stretch the reality by hand=picking the point they use to specify the efficiency

ok, I am convinced. bye, bye, tb, hello mark audio 🙂 . for now.

A 2a3 probably needs close to a real 100dB speaker to shine

any particular driver on your mind? even lother reach 97dB anc cost a little fortune.

Well, here's a concept drawing of one that I built for a local guy - his design

thanks for the drawing, but I've changed my mind and jumped in to mark audio alpair 12p

... where will the speakers, listening position [LP] be?
How loud on average do you want them to play at the LP?
... the amp's output impedance...

the speakers will be on the shorter wall, probably about 0.5m from corners.

clubs music - extremely too loud
friday pub music - much too loud
I'd like to hear my own thoughts and I don't like ear pain.
moderate loudness level, sometimes a bit more.

the output impedance should be the same as driver impedance, is it right?
all transformers will be custom made. I can choose impedance (two or three for small extra $$$. e.g. 4/8/16ohm or alternations)

... if not a floor plan that opens into larger space such as ... kitchen ...

... and with well matched MLTL design, generally "easier" builds than BLH...

...would take the Alpairs over the others.

the room is open to the small kitchen, but the space can be separated if needed.

generally I am not scared by challenges 🙂. if anything turns out be difficult for me (I doubt it, I'll just need more time to finish project) I have a friend who is a wood work magician 🙂.

I'll go in to Alpairs to.

C-Horn designed for 8 inch driver, 3M length horn path...CNC access is needed....

For me it's interesting, for my wife looks creepy 😉. calculations and design can be a problem without specialzed software. CNC can be found enywhere this time.

 

[Greg B]

that's a point, but fostex need an extra high frequency driver = crossover.

You seem to be under the mistaken impression that the Fostex FE206EN needs a supertweeter. It does not. The Fostex FE208E Sigma and FF225WK roll off in the top octave and could benefit from a supertweeter, but the FE206EN doesn't need one anymore than the other drivers you're considering.

I don't have much to add regarding your driver choice. It's been covered pretty well.

I would like to avoid anything between amp and driver if possible.

Nice idea in principle, but don't be dogmatic about it. There've already been hundreds of components in the signal path by the time it's recorded.... Better to have an LCR filter if needed than to listen to a speaker with grossly unbalanced response.

 

[Greg B]

the speakers will be on the shorter wall, probably about 0.5m from corners.

Wait a second... You've got potentially usable corners?? This changes everything, or at least some things.

 

[chrisb]

Avebury?

Woden Design | Avebury

Having heard the difference between Pensil and Maeshowe for the A7, this would probably be my choice if both the room and WAF could support it.

The former is often much easier than the latter 😉

 

[makar0n]

Wait a second... You've got potentially usable corners?? This changes everything, or at least some things.

unfortunatley no. on one side I can move tv set from the corner, but another corner is covered by coach. I think such a big muffler has bad influence on the speaker 😉.

 

[chrisb]

Corners are nice when available, but I think as close to symmetrical as possible is at least as important. If you've decided on the A12P, I'd suggest you consider the Pensil enclosure. For this particular driver, there are two sizes - the standard which is slightly under 12" deep, and the Super at approx 18.5" - I've only heard the latter, and it is definitely an excellent performer.

http://frugal-phile.com/boxlib/pensils/Pensils122p-plan-180412.pdf

 

[atilsley]

If corner access, consider also the Big Fun horn by Ketil Parow. Of all the horns I've built (many), this offers the biggest bass response by far. I've also had the 206E in this horn...very good indeed.

http://www.diyaudio.com/forums/full-range/264322-help-build-lowther-big-fun-horn.html

I used CNC to build a smooth horn path, and easier construction....still massively heavy.

Andrew