Horn Subwoofer Information Needed

nikg736

Member
2018-05-09 2:19 am
I had originally posted this over at the AVS Forum, but I am going to move my postings to this forum as I think this is more the right place to ask

I am intrigued with horn subwoofers. It appears that they offer some great benefits with regards to SPL and also sound quality. Ability to get the same sound with less power or fewer drivers or smaller drivers compared to other designs like sealed or ported.
However, I am getting confused about all the variations and characteristics of each. Tapped horns, front loaded horns, tuba horns, folded horns etc. Also specific designs from specific people like Danley, Fitzmaurice, lil mike. F20, lilwrecker, Full Marty, Titan 39 etc etc.
Is there a thread or website that explains all of this? For instance, would clearly explain each horn type or category. Like some of the designs have a sealed rear cavity firing into the "horn" pathway where others have the driver "open" on both ends and are placed within the horn pathway using a specific formula. Also is a tuba horn a type of front loaded horn etc? Explanation of the general characteristics of each type as far as efficiency, response etc. Pros and cons. Suitable drivers. Is a folded horn used to achieve a certain box size but same thing could be achieved with a simpler design if you were willing to build a longer/larger enclosure. Finally, an explanation of who's designs are what. For instance, the F20 is a specific tapped horn...but at the end of the day it is a tapped horn.
 
I can't answer all your questions but I can write about why I prefer horns and planar wave high order QW bandpass alignments like the ROAR designs.

A surface mounted driver (normal bass reflex or closed box for example) has way to much moving mass and not enough motorstrength to create a steep pressurized nonlinear and non-sinusoidal waveform in the air it couples to. This can be heard as a lack of slam and attack and a lack of fine grained reproduction of modulations and texture of the bass.

A first step to take to enable reproduction of details, texture, warped modulations, slam and attack is to mount the drivers in a PPSL arrangement. Once the drivers work against a 1/3 or 1/4 driver SD slot of air, their ability to create a high pressure steep nonlinear and non sinusoidal waveform greatly increases. A large fullsized horn takes this to the extreme, since it greatly increases the drivers ability to transfer energy effectively to the air.
 
Don't want much do you? ;)

The basics:

All horns are designed straight and folded as required to meet the needs of the app.

Tapped [TTL, TH] must be folded back on itself to load both sides of the driver.

Compression horns [FLH] have sealed backs. The driver is typically a 4th order band-pass [BP4] alignment.

Back loaded [BLH] have open backs or fronts depending on how you want to locate the driver, which is typically a vented alignment [BR] with a huge flared horn/vent. AKA 'BVR', 'Voigt horn' among others.

Compound [pipe] horns are front and back loaded. The most basic type is the B0$3 Wave Cannon.

Wave guides [WG] only get gain via directivity.

That's it, all the rest is variations thereof with some folks giving them names for marketing/whatever reasons and WRT driver selection it just depends on the needs of the app.

The rest and much more you're wanting is online...........

GM
 

nikg736

Member
2018-05-09 2:19 am
I had done a little looking online, but these responses are incredibly helpful. I want to build a subwoofer for an outdoor system for my back deck at my house. I am not necessarily looking for audiophile sound nor extension below 20hz. If I get down to 30hz that's actually fine with me. I originally was considering sealed, ported and bandpass. But then I found a thread on tapped horns and it intrigued me primarily because of output efficiency. But they appear to have some other great advantages as well.

I used to dabble in audio during my 20's but then life/marriage/kids etc. Now decades later I am getting back into it. I have found tons of drivers from back in the day and want to put them to use. For this particular project I would like to use a Kicker C12a with the following TS parameters. These were on the spec sheet and not actually measured by me.

nominal 4ohm
spl1w/1m 89.56dB
displacement 93cu in
Revc 3.59 ohm
Sd,sqM .0531
BL 9.61
Vas 15.59 cuft
Mms, gms 81.78
Fs 16.7
Qms 6.985
Qes .334
Qts .318
Pmax 400w
Xmax 7.68mm

These were intended to be used in sealed boxes or 4th order bandpass.
Could somebody tell me if these might be suitable for horn use just by looking at the TS data? I was leaning towards an FLH possibly because of the sealed rear chamber thinking that it would retain the air spring of a sealed box that these were originally meant for.
If these numbers dont look at all good for a horn, I do have another 12" DVC driver that I got either from Parts Express or maybe Madisound. I would have to dig up the specs or test myself to get them. Hoping a phone-based sine tone generator and a multimeter could get me those results.
 

nikg736

Member
2018-05-09 2:19 am
I found the other woofer. It is an old Madisound 12204 dvc. Specs in picture. It has been in storage in attic for many years and it looks a bit saggy. I think it was stored facing up and the spider is sagging badly downward. Is it ruined or could using it again fix that problem. Also are the specs any good for a horn. Thanks.
 

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TH tuning is normally somewhat below Fs, so combined with a huge Vas, low Xmax the C12a will be tuned too low, freaking huge with disappointing output for its size/cost. The 12204 will merely be tuned too low, huge and with less Xmax even more disappointing.

Depends, turn it over and use a hair dryer to heat up its spider, surround or if you live where it's hot outside just set on a flat hot spot outside like I do each summer when I flip some old Altec, Jensen on my sidewalk. At up to > 100 degF., it doesn't take long. ;) As long as there's no VC 'rub'........

For your app, a ~30 Hz Fs mobile audio or prosound sub-woofer with the highest Xmax, lowest Vas, medium Qts you can afford will suffice'


GM
 

nikg736

Member
2018-05-09 2:19 am
GM - I was thinking not to do a TH but a FLH with a sealed rear chamber. And tune it higher so the enclosure wouldn't be so big. But it sounds like even that might result in a huge box. Is there any way of getting a horn design down to a reasonable size, even if the response only goes down to say 35hz?

At this point I am thinking that maybe I am just better off looking into a bandpass box. My main goal is to make something efficient so it could be used outdoors, and I know the simple sealed boxes that these were intended for will produce the least SPL especially outdoors.
 
You can't have efficient, extension and small at the same time. Efficient and extension means huge. Efficient and small means no extension.

For your application you could consider the othorn. Alternatively you could go for a ROAR design if you're willing to sacrifice extension. Of course there are a lot of options.
 
I've been wondering how VAS affects the response / output in typical tapped horn applications. Or actually the theory behind that.
I only have Tham 15 and HOG scoops (which is a kind of TH too) and tested several drivers in these. According to my experiments, low VAS indeed seems to be better. More important than very low Qts or so.
 
my 4 m one fold frontloaded subhorns have ventilated rear chamber to balance pressure in horn....a calculated foam plug is placed instead of closed rear and side walls in rearchamber
result is more even impedance and easier load, and as a bonus the subs behave more like dipoles in that they don´t excite room nodes
custom designed for 3 guys here around Oslo, by one of the guys behind the new NNNN pro speaker line...
 

nikg736

Member
2018-05-09 2:19 am
You can't have efficient, extension and small at the same time. Efficient and extension means huge. Efficient and small means no extension.

For your application you could consider the othorn. Alternatively you could go for a ROAR design if you're willing to sacrifice extension. Of course there are a lot of options.

Jag...lets assume I have no idea what you are talking about with othorn or a ROAR design.

I guess I will just reiterate what I am looking to accomplish and maybe get some feedback.

1-Use the drivers I already have. I found a bunch of old drivers from back in the day and want to put them to use.
2-Be relatively efficient - I will use this outdoors so I know only certain designs will work. I originally considered a horn because they seemed efficient.
3-Reasonable size. Being outdoors and possibly below my deck size is not too much of an issue. But I dont want to use 2-3 sheets of plywood or MDF.
4-Reasonable extension. I dont need this to go down to 20hz. anything 30-35 hz or even 40 is fine.

Just looking to add some bass so music sounds better than stand-alone speakers. Probably going to use 5.25" or 6" mid woofers in the main 2-way speakers. I have woofers laying around and want to use them to improve the overall sound of an outdoor system. They will sound better radiating in free air vs sitting in my attic for another year.

If othorn or ROAR might work then would love to know more. Otherwise I might just stick to making a 4th order bandpass.

Thanks for all the help
 
I've been wondering how VAS affects the response / output in typical tapped horn applications. Or actually the theory behind that.
I only have Tham 15 and HOG scoops (which is a kind of TH too) and tested several drivers in these. According to my experiments, low VAS indeed seems to be better. More important than very low Qts or so.

Pretty much like a vented alignment for TH, but don't know the math, I just use some rules-of-thumb from experience. As a general rule I use 4x Vas, which is the ~ the beginning of an IB volume.

HOG scoops OTOH are closer to stub BLH [aka big vent reflex/BVR] than a BP6/TH, so yes, you want a very stiff suspension like a Kicker 9515 [once?] used in some really serious output prosound subs or similar since there's not enough horn throat pressure to really 'lock it down' when the power goes up. Qts' sets the gain BW, so choose it based on how much heat rise effects it.

Fhm = 2*Fs/Qts'

Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

GM
 
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jm61

Member
2013-04-26 4:59 am
As the lower frequency limit of the horn depends on the length of the horn and the mouth area, the size will increase surprisingly when going down in frequency. A rear sealed horn for a 12 inch driver with a limit of 38Hz (if I remember correctly, it was a long time ago I built it) needs a length of 1,5 meters and a mouth area of 0,5 square meters. That was for a horn placed in the corner of the room. If you move it to the middle of the wall (equals 1/4 radiating space) you will need a 1 sqm mouth, on ground with no walls (=outside) you need 2 sqm. Plus the added length to the horn. Be prepared to use at least 3 sheets of MDF:)
-As said, it was a long time ago, but I think that was how it went.