Hi from Cambridge, UK

[peteaphid]

I got this (page 11, incl graph):

Another desirable consequence of diffuse radiation together with wide directivity is
that in a given room the acoustic output, and hence loudness, of an NXT panel falls
away more slowly with increasing speaker-listener distance than is the case with a
diaphragm vibrating coherently. The sound pressure from a conventional loudspeaker
approximately obeys the inverse square law, falling by 6dB for each doubling of
distance. With a DML the fall-off with distance is reduced, while the uniformity of
sound distribution is increased.

from here: http://www.tectonicaudiolabs.com/wp-con ... ersion.pdf

I guess this benefit might be lost without room reflections...

On the folded-horn front, I'm more or less decided on a single T39, built as:

- 39 x 19.5 x 16" in size
- 4 ohm 10" driver, hopefully neo-magneted
- poplar ply to reduce weight, maybe skinned with something to protect it from impact damage

If this sounds all wrong, someone please tell me, otherwise I'm going ahead and ordering the plans:)

[bjm362]

I got this (page 11, incl graph):

Another desirable consequence of diffuse radiation together with wide directivity is
that in a given room the acoustic output, and hence loudness, of an NXT panel falls
away more slowly with increasing speaker-listener distance than is the case with a
diaphragm vibrating coherently. The sound pressure from a conventional loudspeaker
approximately obeys the inverse square law, falling by 6dB for each doubling of
distance. With a DML the fall-off with distance is reduced, while the uniformity of
sound distribution is increased.

from here: http://www.tectonicaudiolabs.com/wp-con ... ersion.pdf

I guess this benefit might be lost without room reflections...

On the folded-horn front, I'm more or less decided on a single T39, built as:

- 39 x 19.5 x 16" in size
- 4 ohm 10" driver, hopefully neo-magneted
- poplar ply to reduce weight, maybe skinned with something to protect it from impact damage

If this sounds all wrong, someone please tell me, otherwise I'm going ahead and ordering the plans:)

I am going to use that word that people hate the most when I talk about sound and sound reinforcement (people ask a lot for advice when I show up at gigs due to having a very good reputation locally). It depends! Some of the situations you have stated you intend to use those in you are going to find some benefits from the rear projection feature of those speakers. There are a lot of situations where the volume they produce will be sufficient, some of those it will not! In my professional opinion you are right to focus on building good subs while you are evaluating what you have in those tops!
One thing to remember in sound reinforcement is that everything depends on how you are using it!
I would like to suggest that you also take a good look at BF's Wedgehorn series speakers. Those should prove to be very useful in that they can be used as vocal monitors on stage, or as good tops for a compact system at smaller gigs!

[Grant Bunter]

I would like to suggest that you also take a good look at BF's Wedgehorn series speakers. Those should prove to be very useful in that they can be used as vocal monitors on stage, or as good tops for a compact system at smaller gigs!

I disagree.

While this has been done by some, you have to be very careful using WH's as tops.
Even when I built mine, I ran them at perhaps 7 volts (just over 6 watts) without EQ and was surprised at their full sound.
Having said that, depending on which model one builds, they all reach Xmax quickly at lowish power levels, at a figure in Hz well above where one might normally like to crossover.
Their design is focused on vocal intelligibility and IIRC those that have used them did so with speeches etc, and very low level music.
You would be much better served to build a tops design of Bill's, eg half height SLA pro's...

[bjm362]

I would like to suggest that you also take a good look at BF's Wedgehorn series speakers. Those should prove to be very useful in that they can be used as vocal monitors on stage, or as good tops for a compact system at smaller gigs!

I disagree.

While this has been done by some, you have to be very careful using WH's as tops.
Even when I built mine, I ran them at perhaps 7 volts (just over 6 watts) without EQ and was surprised at their full sound.
Having said that, depending on which model one builds, they all reach Xmax quickly at lowish power levels, at a figure in Hz well above where one might normally like to crossover.
Their design is focused on vocal intelligibility and IIRC those that have used them did so with speeches etc, and very low level music.
You would be much better served to build a tops design of Bill's, eg half height SLA pro's...

That is very unfortunate to hear. I own some bass reflex wedges with 8s that cost about $50 each and have worked very well in that role running from 120 hz up. They too have tremendous intelligibility due largely to the 8 inch speakers ability to reproduce the human voice. 8s are wickedly clear in the 1k to 3 k range! Are the wedgehorn 8s you have loaded with less than favorable drivers or is it a horn design issue? Did you try crossing them a little higher? How high would you need to cross them to get the horns to work properly?

[peteaphid]

I'd like to just return to my original question, before I go ahead and order the plans.

I'm more or less decided on a single T39, built as:

- 39 x 19.5 x 16" in size
- 4 ohm 10"/12" driver, hopefully neo-magneted. I presume the plans will help my driver decision
- poplar ply to reduce weight, maybe skinned with something to protect it from impact damage

If this sounds all wrong, someone please tell me, otherwise I'm going ahead and ordering the plans:)

[88h88]

The T39 is a great sub, I have a pair of 22" wide ones myself. As you're running it off a battery you should make it as wide as possible to get free output, use a 12" again for more free output (in comparison to the 10"). Mine use Lab12s but the 3012LF are the neodymium option and hence lighter.

[whines]

Sounds like a good choice to me, t39's are reasonably small and have a lot more output than t24's. I'd go with the 12" driver.

[peteaphid]

Cheers for the info - it's decided, then! I'll stick to a narrow format, because it'll fit in my van, but go for a 12" speaker. I'll see what the suggested drivers/parameters are before going any further.