Folded Horn Subs or recommendations

[kd7gab]

Hey all,
I am preparing to start building a sound system over the course of the next year. I have been doing a lot of research and searching on folded horns and i have yet to find a good source of relevant info. I have read that in certian cases the folded horns require a large distance to develop a wavefront. If anyone can shed any light on this for me that would be great. I am looking into building a set of horns, either 2 dual 18 and 2 dual 12 boxes or 2 dual 21 and 2 dual 15 boxes. I have been planning this arrangement to facilitate high spl's and lower distortion. I want to use this system in a variety of locations, mid to large rooms (larger auditoriums) and outdoors. Any input and advice would be greatly appreciated, I you have another route that might be more suitable please let me know. The mid/high cabinets i am going to construct are single 12" mids in a horn system and a pair of compression drivers.

Thanks in advance

[Rademakers]

Why not build 2x2 single 18"? In most cases it would offer more advantages and your back would be happier. One 12" to keep up with 2 hornloaded 18" would probably offer only very narow dispersion. Personally would double it.
A visit to www.speakerplans.com would help out, as it's more related to hornloaded and PA and it offers some very nice designs (1850 and 186 horn and tops).

Mvg Johan

[Brett]

LABhorn

[AndrewT]

Hi,
yes, have a look at Labhorn and particularly Tom Danley's treatise.
I liked his concluding comparison between his twin 12" horn cabinets and an IDEAL ported set of cabinets to produce similar SPL at similar frequencies. One set of horns is equivalent to 10 times as much power into 5 times (or did it say 10 times?) as many 18 inch speakers. At considerable extra cost and weight and volume (my words).

[paulspencer]

One set of horns is equivalent to 10 times as much power into 5 times (or did it say 10 times?) as many 18 inch speakers.

Andrew, that sounds like a bit of an exaggeration!

Ok so lets say we have one horn loaded 18 driven by 1kw to get max SPL. You are saying that it is equivalent to 10kw driving 5 or 10 of these drivers in a vented design?

That would be about 30db extra output gained through horn loading

Horn experts: how much extra juice (power and efficiency) do you get out of horn loading?

[mwmkravchenko]

Typically there is a 10 db efficiency gain when a driver is properly horn loaded.

In terms of input power about 8 times less for equal loudness compared to a direct radiator.

Figure it like this. Every 3 db is a doubling or halving of power input. So every 3 db of efficiency gained allows a halving of input power from the amp to produce the same SPL.

As a side note most people percieve something as being twice as loud when it is actually 10 db louder than before.
So horn loading is going to get you louder.

This is true for only the passband of the horn. Above and below it acts much like a direct radiator. The efficiency gain is out the window. Below the low end cutoff of the horn it behaves like a ported box. The driver will flap wildly and most often destructively.

All this wonderfull volume at the expense of room volume



Mark

[paulspencer]

Thanks Mark that is more like what I had thought.

[Brett]

Agree with Mark, plus, there is usually a large reduction in distortion in the passband of a well designed and implemented horn.

[AndrewT]

Hi all,
I did not claim the ten fold decrease in power. I was repeating what Tom Danley found out.
By the way 30db is one thousand fold decrease in power. Neither Tom Danley nor my reference to his work claimed that.
I too echo Mark's reply i.e. +10db improvement in efficiency for horn loading seems to be the norm.
Now go and read Labhorn and you'll find that it was designed for both in room and outdoor narrow band (30Hz to 80Hz) bass reproduction.

[dlsbobby]

Just remember though that the labs were designed to be in stacks of six. That is to reach the required mouth area to get good output at 30hz. However a friend of mine only has a four stack and says it's all he can handle. Also, speakerplans.com has alot of DIY plans. I've built some and they are pretty good. Robert.