Which Horn for linear response down to 20Hz?

[Bass-Depth]

Hi !

I want to build a Subwoofer for my Homecinema and thought of a LAB-Horn,the Lab Horn is really nice but i want a Subwoofer which goes down to 20Hz with more Output than a SVS PB12 Ultra 2
It's important for me to have a clear Bass so I only want to build a Horn
Max.SPL @30Hz should be more than 120dB @ 1m

Please can you say which DIY-Sub would do all I'm dreaming of and isn't more expensive than the LAB-Horn???

David

Sorry for my english...i'm from Austria

 

[johninCR]

A LABhorn is only a 35hz horn. A true 20hz horn is huge. Plan on building something that utilizes a corner as part of the final flare to keep the size down. Personally, I would use a vertical array of drivers in a corner horn to make use of the vertical space that would otherwise be wasted and create a false corner that would actually be a huge horn without looking too intrusive.

 

[planet10]

Please can you say which DIY-Sub would do all I'm dreaming of

It will need to be BIG. Really BIG.

dave

 

[SpeakerBob]

Surely it must be time to post this badboy again


http://www.royaldevice.com/custom.htm#HORN SUBWOOFER


Rob.

 

[Ron E]

That 20Hz horn will be larger than Ober Oesterreich

I guess if you want to build a 20Hz horn, you should get Hornresp and spend a lot of time on "horny" forums. You can shorten the horn quite a bit and reduce the mouth area by the use of boundaries, but there is a limit to what you can do without making the response very ripply. In a high SPL environment, 35Hz is more than enough - the lower frequencies will just rattle stuff and waste amp power. I wouldn't knock the labhorn's extension until you heard it.

I lived in Austria a while back - in der Wachau.

 

[quiet]

Surely it must be time to post this badboy again
http://www.royaldevice.com/custom.htm#HORN SUBWOOFER Rob.

funny i thought the same thing -

still a vertical array using the hight of the room and a corner
or the hole wall..... seems like a good idea

20hz is loooow for a horn

 

[simon5]

I played with Hornresp a bit to help you.

Best results I had was with Acoustic Elegance AV15.

It's a Catenoidal horn.

Length of 6 meters and mouth area of 16612 cm^3 if it's a corner horn. You also need a rear compression chamber of 125 liters. Ripple is about ±3 dB with 110 dB sensivity with 2.83V RMS imput. I tried to design the smallest 20 Hz horn with ±3 dB ripple.

You'll need to be creative to build a catenoidal horn and to fold the 6 meter length in three so it can stand up in a corner of the room.

Good luck!

 

[simon5]

Just beaten what I said.

I used a Ascendant Audio Avalanche 18. I know it's discontinued but if you can get one...

Catenoidal horn
12100 cm^3 mouth area
5 meters long
250 liters rear chamber

In theory with a 800W RMS amplifier into 4 ohms, this horn could do 135+ dB from 20 Hz to 80 Hz.

 

[rcw]

re 20Hz. horn

Back in the 70's an Australian electronics magazine had a feature about a man who had an extension built on his house in the shape of a 16Hz. horn, it had a listening area at the big end and an array off 15inch woofers at the small end.
The report was that it sounded quite impessive with organ music.
Anything less than this would seem to be an inedequate compromise.

 

[planet10]

Re: re 20Hz. horn

Back in the 70's an Australian electronics magazine had a feature about a man who had an extension built on his house in the shape of a 16Hz. horn, it had a listening area at the big end and an array off 15inch woofers at the small end.

I had a customer (in the late '70s) with similar -- don't know how low it went, but he used a single B139.

dave

 

[Brett]

You can shorten the horn quite a bit and reduce the mouth area by the use of boundaries, but there is a limit to what you can do without making the response very ripply. In a high SPL environment, 35Hz is more than enough - the lower frequencies will just rattle stuff and waste amp power. I wouldn't knock the labhorn's extension until you heard it.

My LABs, corner loaded with a flare extension as per TD's suggestions got well into the 20's. Shook everything in my house, and the neighbours. I really don't beleive if you'd listened to them that you could realistically want for more.

 

[slowmotion]

Hi all

I'm going for floor-to-ceiling corner horns ( two of them ) myself,
but I don't expect to go much under 30Hz.
We'll see in a year or so

Seriously, I think about 30Hz is just about managable,
if you want to use proper horns. If you want to go down to
20Hz you probably have to build the horns as part of the house.

Good luck !

cheers

 

[johninCR]

What is the consensus regarding the use of a large chambered rear horn to achieve the extra low extension?

Designs like the Jensen Imperial are able to achieve extension far below the horn tuning this way. A corner array would be more impressive to look at if you can see the drivers. HornResp only goes to 99L for the chamber size for RLH's making modelling a big array impossible. Is there some rule of thumb for predicting the response from stacking horns if you know the response of a single unit?

 

[Bass-Depth]

Thanks for your answers!!!
Probably it would be enough with the Lab Horn but now my Sub is a Double 12" (one active one passive) which plays down to 25Hz @ -3dB...but it's not loud...this Sub is good for beeing in a 20m² room...
Has anyone of you ever heard an SVS PB12 Ultra2??? I want this deep bass of the SVS but more SPL and the Horn-Sounding Bass...

David

 

[moray james]

domestic size

Would not a bank of reflex loaded 18 inch deivers do the job in a smaller area and be less complicated cabinet work? The pro's usually do this as it makes for a more portable rig.
Ask Tom Danley he knows how to move a lot of air at low frequencies. Would be interested to hear his ideas. Regards Moray James.

 

[Kravchenko_Audio]

For JohninCR

I ripped this off the DIY-Systems site under the bass horn link:

Additional info to take into account

Until now only a small part is explained, there is more to it! Now we mainly know how to calculate the actual horn it is useful to know how two horns beside each other have influence on the response, and how the driver cabinet (the back chamber) has influence on the speakers parameters when adapted to the horn.

When the mouth area Am of two horns are placed beside each other then the result will be a better performance in the lowest bass because the area is now doubled. The next formula can be used to see if we can lower the frequency Fg by the enlargement of Am.

Mind in the calculation where you want to place the horn, by placement in the corner the surface Amt must be multiplied by 8 !

Basic formula for calculating the lowest frequency radiated by the horn...

An advantage is that the new horn can be calculated as being shorter. Because we work in stereo the efficiency is 6dB higher (two speakers instead of one) and the power capabilities (mechanical and electrical) improves.

What has changed is the larger (total) throat area Ah. In reverse you could say its the smaller (half) mouth area Am. The bigger the throath- or the smaller the mouth area the shorter the hornlength.

Suppose a Fg of 30Hz is wanted, according to the next formula the mouth area Am (m²) will be:

Calculating the horn mouth area...

Placed in a corner the result will be 1.32 m². When two horns with their mouth close to eachother are used, the result can be divided by 2 (0.658 m²). By calculating the contour (flair) of the horn it becomes clear that for the same Fg a shorter horn is sufficient. Of course it is possible to use more than one speaker in a horn, Ah is then multiplied by the amount of speakers.

The advantage of more speakers is that the power (mechanical and electrical) improves, the throath can be enlarged (shorter horn) and, not less importent, the speaker selection is less critical.

It is found here: http://www.diy-systems.com/

Bass horn design section

Hope this helps

Mark

 

[simon5]

Has anyone of you ever heard an SVS PB12 Ultra2??? I want this deep bass of the SVS but more SPL and the Horn-Sounding Bass...

SVS PB12 Ultra2 is not that hard to beat with a huge ported box. You won't have the horn sound, but it will be deeper and louder than the PB12.

 

[johninCR]

Mark,

That info jives exactly with some modelling I've done in HornResp. eg a 6ft tall corner horn with 8 $22/ea Pioneers , PE# 290-063 with an Fs of 40hz, shows a peak sensitivity of 110db at 90hz, dropping smoothly to 107db at 40hz, 105db at 30hz, and 100db at 20hz. That's an RLH with a 99L chamber and I believe a larger chamber would go even lower. With only a 1.7m horn length and 700cm throat (50% of Sd) and a 37hz flare rate, it would fit in about the same floor space as a typical boxed sub. At 30hz it would come close to Bass-depths requirements, but at lower frequencies he'd run out of excursion quickly.

I just wish HornResp could handle larger RLH chambers because I'd love to model a floor to ceiling corner horn with more appropriate larger drivers, like 8 12's or 6 15's.

 

[xstephanx]

Clean deep bass and no one said tline?

Tline can usually get VERY useable spl about an octave below tuning
but to go on the safe side, lets design a tline for 30hz instead of 40
so

speed of sound (330 m/s roughly for average air elasticity)/ frequency(30hz)= (330/30=11) soo 11 meters is how long a FULL wavelength of 30hz is, but with a tl you can get away with only 1/4 wavelengths.

11x.25= 2.75, a relatively feasable length, especially when you consider that this is a straight 1/4wave pipe, when you start getting into things like tapering, you should be able to reduce the length EVEN MORE

Stuffing to reduce length is a controvertial subject, ive heard reasonable arguments put forth by both schools of thought, so throw some in, but dont count on it too much.

The only downside to a tl as opposed to a horn is the efficiency really, tls and hrons are really different, horns are practical for high frequency, high efficiency reproduction, while a tl is more a low frequency lower efficiency route.

Oh, and hrons have colorations as well, ive heard alot of people say hey preffer a transmission line over a horn sound.

 

[Bare]

I think you guys are just 'wanking' here
What you fantasize about is perhaps considerably beyond your expectations in real life.
A few months back/last Fall ? Dr Edgar published /posted Images of Genuine 30hz horn(s) built on comission for some undisclosed Military purpose. Given their pedigree they likely did meet their design specifications.
These were Huge, monstrous in fact, as in they would not fit within in a regular house shape.
Just the thing to listen to Hip Hop with, in yer Mom's basement