Smallest Footprint Horn and Driver that can reach 500 Hz

Hi guys!

Any ideas on the smallest footprint Horn and Driver combo that can go down to 500 Hz?

Listening room is only 9ft x 9ft (hence I need something compact) so I think I can get away with crossing a compression driver (or fullranger) lower to meet a 12" woofer.

Will be using a minidsp for crossover duties and eq to tame the driver and horn.

I live in Southeast Asia and the only direct couriers we have are in the USA. I dont know if horns.pl or stereo-lab.de can ship affordably to asia. So a US supplier would be ideal.

Thanks
 
Why would you like to build a horn? What is it that you are after, efficiency, pattern control, horn sound, high SPL capability, ...?

For a horn with 90 degree horizontal dispersion, a crossover frequency of only about 1 kHz is required to match directivity with a 12" woofer. Search for 'Econowave'. A 1" compression driver can handle that (meaning that it's high frequency performance still is OK; larger drivers do not perform that well at > 10 kHz), though it cannot go down to 500 Hz.

A horn that maintains 90 degree dispersion down to 500 Hz would need to be over half a metre wide, that's physics unfortunately. If you can make it flush with the corners of the room, it does not need to have a size because the walls will take care of the directivity.

Also check out the 'Small Syns' thread: Small Syns
 
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frugal-phile™
Joined 2001
Paid Member
The general rule-of-thumb is that the perimetre of the horn mouth should be at least a wavelength of the lowest fequency you want to reproduce. Length will depend on the flare.

You aren’t going to be able to fit a 500 Hz horn into a room that small and get a far enuff listening deistance for it to even work.

dave
 
Hi guys!

Any ideas on the smallest footprint Horn and Driver combo that can go down to 500hz?

Listening room is only 9ft x 9ft (hence I need something compact) so I think I can get away with crossing a compression driver (or fullranger) lower to meet a 12" woofer.

Will be using a minidsp for crossover duties and eq to tame the driver and horn.

I live in Southeast Asia and the only direct couriers we have are in the USA. I dont know if horns.pl or stereo-lab.de can ship affordably to asia. So a US supplier would be ideal.

Thanks

An older generation ( 1" exit / 44mm diaphragm ) will get you pretty close ( to your low X-over point ) when working through a large enough BiRadial horn.

"Older Gen." will usually translate into a Lansing company product ( JBL & sometimes Altec ) where historically the Fs of small format drivers were low and down around 600hz ( & max UHF is 15-16K ).

Here's a trace of a JBL 2427H on an Altec 811 sized BiRadial sold by ZXPC ( in Florida ).

JBL2427H_ZXPC_Horn.png

This horn needs about 1/2 lb of mastic/plumbers putty added inside it smoothed around the throat entrance area, to fix the egregiously lousy stock expansion curves ( IMO, the horn is useless without this treatment ).

Here's another ancient trace of mine showing a 2427h on an Emilar Radial ( which is slightly smaller than the ZXPC.

JBL2427H_Emilar_Horn.png

HERE's the horn link!

& here's what it looks like.

s-l400.jpg
s-l400.jpg


:)
 
Here is a small horn that can hold its polars down to 500 Hz...the Klipsch K-510 horn in the top of a modified La Scala industrial (split):

EA0512FF-E7E6-4F68-8E73-FAF571ED2118.jpeg

...and the vertical polars for that horn and compression driver (...measured polars, not calculated--as is shown in the title):

96782B32-0B80-40D6-AC33-AF61957E3E2A.png
 
An older generation ( 1" exit / 44mm diaphragm ) will get you pretty close ( to your low X-over point ) when working through a large enough BiRadial horn. <snip>
I found the same issue with that horn.

Here's some measurements I made here: Edge of No Control

Personally, I prefer the square one that Pyle sells, model "PH12S"

But the JBL PT waveguides work even better. Admittedly, they don't "load" as low as the horns do.
 
Hi guys!

Any ideas on the smallest footprint Horn and Driver combo that can go down to 500hz?

Listening room is only 9ft x 9ft (hence I need something compact) so I think I can get away with crossing a compression driver (or fullranger) lower to meet a 12" woofer.

Will be using a minidsp for crossover duties and eq to tame the driver and horn.

I live in Southeast Asia and the only direct couriers we have are in the USA. I dont know if horns.pl or stereo-lab.de can ship affordably to asia. So a US supplier would be ideal.

Thanks

I've posted zillions and zillions of Unity horn projects, and it's largely because what you're chasing after is virtually impossible.

There are a hundred compression drivers that can play 1khz-16khz on a waveguide or horn. There are a handful that can play 1khz-20khz on a waveguide or horn. There are very very few that can do 700hz - 20khz and they're REALLY expensive. For instance, a TAD 2001 can do it, and they're about $2000 a pair.

It's fairly trivial to make a Unity horn than can do 350Hz - 20Khz on a single horn, and that's probably the reason that Unity horns are on the front page of diyaudio every single month.

Horn aren't like regular speakers. You basically have two things that are at odds with each other, and those things make it exceptionally difficult to get wide bandwith out of a front loaded horn. Basically you need a very small throat to get the horn to play up to 20khz. And you also need a small throat to achieve a wide beamwidth. But at the same time, you need a BIG throat to play low. If you want to play down to 500Hz, you're going to need a throat that's fairly large. (If the throat is too small, you get compression, and that creates distortion.)

Unity horn solves all this nicely. It's basically two horns stacked on top of each other. A small one for the highs and a big one for the mids.
 
It's quite easy: simply use a 2" compression driver...

Here's another example...a Cornscala Style D: Faital Pro LTH142 Horn with HF200 series compression driver in a bass reflex cabinet with 15" woofer.

You could easily shrink that down to a Klipsch Heresy size using 12" closed box air-suspension woofer. Would sound pretty good. Crites sells a CW1228 woofer with about the same T/S parameters as the K-22 in a Klipsch Heresy.

Chris
 
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Part of the 'barrier to entry' with the Unity horns is that you have to be fairly adept at woodworking, 3d printing, or both. Until Parts Express or diysoundgroup starts selling a Unity horn, that will be the case. (The patent is expired, so there's nothing stopping them from selling one, just as they did with the AMT ribbons when THAT patent expired.)

In the meantime, it might be worthwhile to come up with a design that could be mated to a 2" horn.

post-42414-0-12680000-1463713236.jpg

For instance, this ZXPC horn is big enough to control directivity down to 700Hz, and it will load down even further. One could 3D print the first 4" or so, and then mate it to this waveguide. Basically the first 4" of the horn would be the "Unity" part and the rest would be a plain ol' waveguide.

This would simplify things for a DIYer quite a bit.
 
A slightly larger modified tractrix horn, intermediate between the K-510 and the K-402 would be ideal for a two-way MEH/unity horn for such small spaces. What a lot of people don't see is that these two horns (the 402 and 510) hold their polars to at least an octave below the "mouth circumference frequency" that's being bandied about. In the case oft he K-510, it's more like two octaves below that rule-of-thumb frequency. The K-510 is smaller than the two horns shown above.

That's why I asked questions in a full-range MEH kit thread. For those folks that can take a La Scala-sized full range MEH, the K-402 makes the most sense. For those in really small listening rooms, the intermediate size horn makes the most sense...in a full-range MEH. There are some definite advantages in a full range MEH approach. But you first need the horn(s) to do it. (That's what I'm currently working on.)

Chris
 
OP: I see you are new. nice profile pic :)

Have you done speaker builds before?

Have you got a plan for measurement and eq?

Does your living situation allow odd configurations, like mounting the system in upper corners of the room (so that 'footprint' becomes irrelevant)?

There are a hundred compression drivers that can play 1khz-16khz on a waveguide or horn.
[...]
Unity horn solves all this nicely. It's basically two horns stacked on top of each other. A small one for the highs and a big one for the mids.

A unity build may be jumping a bit too far in, if the OP isn't an experienced builder :)

Another solution: don't use a compression driver. The OP specifically mentioned using a fullranger as an option.

In a 9' by 9' room, SPL requirements are probably low, so a small driver (Fountek / SB Acoustics / Peerless etc) + the horn you show in post 12 could do the job nicely.

I've just taken delivery of some new drivers, so soon I'll be doing exactly that, with that horn.

One could 3D print the first 4" or so, and then mate it to this waveguide. Basically the first 4" of the horn would be the "Unity" part and the rest would be a plain ol' waveguide.

This would simplify things for a DIYer quite a bit.

Great plan! Please do it :)
 
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Hi, I did a cheaper version of this [...] using a different horn, Horn Flare Large Format 2" Throat 4 Bolt Mount

That looks like a good horn. Very DIY friendly with the ~flat sides and front.

you need to make a small little mating flange to connect the peerless driver to the horn to get a better/smoother transition and using some eq to boost the top end and cut down the mid and you get reasonably smooth response down to 400Hz .

I tried the NE65W-04, just using a brace & a chunk of foam to press the driver against the horn throat. It is not a perfect fit (the throat is a trifle larger than the moving area), but it worked nicely.

The pic = full space response without eq (just a 200Hz high pass), measured 50cm from horn mouth. Nothing clever done (no windowing, not calibrated with SPL meter, mic positioned on reflective object), but it still shows very smooth horn gain that will be easy to eq flat.
 

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Hi guys! Any ideas on the smallest footprint Horn and Driver combo that can go down to 500h? Listening room is only 9ft x 9ft (hence I need something compact) so I think I can get away with crossing a compression driver (or fullranger) lower to meet a 12" woofe[r].

Will be using a minidsp for crossover duties and eq to tame the driver and horn.

I live in Southeast Asia and the only direct couriers we have are in the USA. I don't know if horns.pl or stereo-lab.de can ship affordably to asia. So a US supplier would be ideal.

To follow up: it's clear that the 500 Hz to ~20 kHz band is easily covered using one horn and one driver...notably a 1.4 inch to 2 inch throat diameter compression driver. You can also look at using dual-diaphragm compression drivers (BMS makes them, among perhaps others) in this regime to reduce any existing angst about using single driver full bandwidth.

The reason for posting on the K-510 horn is that it has posted polars that are outstanding relative to other horns in this size class, and it is a very small horn physically to meet the stated requirement-15" width x 9" height x 4.75" deep (38wx10x12 cm). You also stated that you're planning to use miniDSP to perhaps cross and flatten the frequency response due to the constant coverage nature of the horn. This horn is unlike any others that I've seen or personally measured in terms of its performance. This is a significant performance advantage.

This K-510 horn is available with compression driver attached from Klipsch in Hope, AR. There may be others available used (horns only)--as I bought my K-510 pair. I have used these horns on top of Belle Klipsch bass bins, both in two-way bi-amped and three way tri-amped configurations.

Chris
 
Basically you need a very small throat to get the horn to play up to 20khz. And you also need a small throat to achieve a wide beamwidth. But at the same time, you need a BIG throat to play low. If you want to play down to 500Hz, you're going to need a throat that's fairly large. (If the throat is too small, you get compression, and that creates distortion.)

I am in disagreement with you here. (And this concerns me, as I come here to read your posts. Perhaps I am not picking up what you are putting down.)

First the play down to 500hz portion:

Lets look at the aforementioned BMS coaxial compression drivers. Both the 1.4" and 2" play easily down to 300hz. The 1.4 is no more adverse to the lower frequency response than the 2.0. This is because they both have the same diaphragm, and same exit from that diaphragm, and the same dimensions inside the driver where the diaphragm exits. The only difference is that the body of the 1.4" exit is truncated, as it does not need as much distance to open to 1.4", and the larger exit driver needs to open to 2.0". There is no compression in the exit, only expansion from the moment it exits into the throat of the driver, and the compression (in the compression portion of the compression driver) is in the diaphragm to exit portion, and is constant, from 300hz to 22khz. Are you speaking of compression in the horn, not in the driver? If so, how would compression in the horn be different at 500hz than at 20khz?

Next the play up to 20K portion:

The horn does not need to be any size to play up to 20K. 20K is already propagated when the signal leaves the driver. The smaller the exit the less that 20K will be bouncing around in there, and as you mentioned, the smaller the exit the better the sound will disperse.

I think that the BMS 1.4" coaxial on a RCF HF950, or an 18 Sound XT464 should be a good solution, and would crossover down to 600hz, maybe 500hz depending on the baffle that is used for the horn.

I am not sure what horn would be used to get to 500hz, or if directivity is needed on the horn at that frequency in that room.
 
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