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front loaded horn detailed help

post #1 of 55
Thread Starter 
I'm thinking through a project but I have no experience with front load horns. I'm going for maximum efficiency and output with limited bandwidth. I don't know the exact frequency yet but it will be in the 50 hz range I suspect. The mouth opening could be 50" x 53" and I've got a good bit of horn length available.

Does this seem feasible? What are the basics I should know with horn size, throat size, and volume behind the horn? I'm probably going to use one of my 15" or 18" drivers.
post #2 of 55
The T/S specs of the drivers will dictate if you can use them in a horn design cabinet.
post #3 of 55
Have you read this thread yet?
post #4 of 55
Also, if you are not too interested in designing and just want to build a proven design, the Tuba HT is a well respected design. There are also several designs here (like lilmikes F20) if you search AVS.

Also, as Michael mentioned, horns have specific driver requirements. The horn designs I mention include a list of appropriate drivers for them, if you use a driver that doesn't match the horn you will not get good results.
post #5 of 55
that sounds like a typical p.a. horn.

they are pretty easy to model and to build.

here is the sideview inside a typical pro audio horn.

in this case, it is a cerwin vega.



the length of the horn determines about how low it will go.

the thiele/small specs of the driver determine how best to
make the horn.

any driver can't just be plopped in any horn and expected
to work.

which drivers do you have?
post #6 of 55
Thread Starter 
I have not seen that thread yet, but I should also mention the grand scheme of this design isn't what you're thinking. I'm learning so I can apply it to what I'm doing, without really divulging what I'm wanting to try. The best way to describe it is the driver won't be generating the pressure in a conventional sense.

The basis of how it works, I get. The specifics of my goal is the hard part. While how I'm using it, or wanting to try anyway, t/s parameters should not matter, but here they are:

Fs 28.33 hz
Qes 0.4968
Qms 5.5971
Qts 0.4563
Le 3.2838 mH
Vas 42.9541 L
BL 23.9283 N/A
MMS 555 grams
Xmax 50mm linear 1 way
Sens. 84.68 dB @ 1w/1m
Sens. 89.12 dB @ 2.83v

That's for the 15", I'll start there. The production sub will have a little lower Qts and a little more BL with a little less inductance, I haven't gotten parameters off the production prototype yet. This one is first revision. I know the Qts is not optimal for the application, but I have enough displacement and motor to make up for it.
post #7 of 55
Quote:
Originally Posted by EMF Audio View Post

I'm going for maximum efficiency and output with limited bandwidth..
If that's what you need you don't want to use a horn, you want to use a 6th order bandpass, which can be tuned for very high sensitivity with a narrow bandwidth, with the large chamber tuned high and the smaller chamber tuned low.
post #8 of 55
Thread Starter 
I'm avoiding that for a reason. One problem I've found with trying to create huge efficiencies with 6th order is group delay and phasing. The horn CAN have the ability for bandwidth, but trying to maximize it in 1 spot. This idea may not work at all, but I won't know if I don't try so that's where figuring out what I should do for sizing comes in.
post #9 of 55
"I'm learning so I can apply it to what I'm doing,
without really divulging what I'm wanting to try.
The best way to describe it is the driver won't be
generating the pressure in a conventional sense."

you asked for help on a front loaded
horn and then said that you aren't really
building a front loaded horn and in fact
don't plan to discuss what you are doing.

then you post a massive excursion heavyweight
driver as the test driver, but indicate that
t/s parameters won't matter in your design.

how the heck is anybody supposed to help
you with those design criteria? :-)
post #10 of 55
Thread Starter 
There's got to be some common ground on what to do. For what I do, t/s params aren't magical and you have to go by general knowledge to make things happen. I guess what I'm looking for is something like more Xmax needs a larger chamber or smaller chamber, this size sub needs roughly this size chamber, that kind of thing. General guidelines which I can figure out details in testing. Or for the sake of discussion, is it possible to get optimum efficiency with that size and frequency I'm after? Where my thought process is, with a tweeter, there are huge gains by putting an appropriate horn in front of it. I would like to recreate that effect, in the 50 hz range. The compression side of that would not be coming from a driver in a sealed chamber behind it.

Perhaps a better way to approach this is the horn size and shape itself being calculated and not concerned about behind it at all. I can work that out in testing. Can the size limitations I mentioned in the original post accommodate that?
post #11 of 55
Thread Starter 
This is the driver I'm using. This is the 15" but I may do the 18". http://www.youtube.com/watch?v=UUii8gKytVg
post #12 of 55
Download HornResp, learn how to use it. There may be some who might be willing to do calcs for you, but if they don't know what you're trying to do it's pretty tough to figure out how to do it.
post #13 of 55
Quote:
Originally Posted by EMF Audio View Post

There's got to be some common ground on what to do. For what I do, t/s params aren't magical and you have to go by general knowledge to make things happen. I guess what I'm looking for is something like more Xmax needs a larger chamber or smaller chamber, this size sub needs roughly this size chamber, that kind of thing. General guidelines which I can figure out details in testing. Or for the sake of discussion, is it possible to get optimum efficiency with that size and frequency I'm after? Where my thought process is, with a tweeter, there are huge gains by putting an appropriate horn in front of it. I would like to recreate that effect, in the 50 hz range. The compression side of that would not be coming from a driver in a sealed chamber behind it.

Perhaps a better way to approach this is the horn size and shape itself being calculated and not concerned about behind it at all. I can work that out in testing. Can the size limitations I mentioned in the original post accommodate that?

Take a step back, think about what you want, and once you understand what you want - or are clear on what you want, then you can form a question that would at least get you started.
post #14 of 55
Ok so he is using a custom or modified Sundown Zv4 driver and he is going to put this in a vehicle of some sort for auto competition... etc...You need to identify how much space you have in total for the cabinet how much power you plan on flogging it with and what is the peak frequency of your vehicle typically (50Hzish I would guess)? Do you want something that is listenable or just to put up stupid high numbers?

You mention a 50Hz cutoff and list a super heavyweight excursion driver with an FS below 30Hz and FLH...Your app seems very specific and for this type of thing you can't just start with a driver like that and then force everything else to fit around it. You need to start with the space available and budget...Then define what the system goal is (loud as possible, frequency range to be covered, is some listenability needed, etc..) Then define how much power you plan to have available...At this point start looking at what type/s of system fits into this plan logically(FLH, TH, TL, BP4/6, Vented, PSPCBM, etc...) At this point you would start identifying driver candidates that fit the bill for the app. You may find that there are other choices that would perform much better in the intended cabinet/app.
post #15 of 55
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

Download HornResp, learn how to use it. There may be some who might be willing to do calcs for you, but if they don't know what you're trying to do it's pretty tough to figure out how to do it.

I hate how Hornresp lacks labeling. It doesn't indicate what is what and in what unit of measure, that just takes 4 times longer to do anything. I know what I'm trying to do is very tough, that's why I'm asking for some assistance to guide me in the right direction. If I can't simply get a horn dimension for that frequency, then maybe a horn isn't what I need to be doing at all.
post #16 of 55
Thread Starter 
Quote:
Originally Posted by diaz View Post

Take a step back, think about what you want, and once you understand what you want - or are clear on what you want, then you can form a question that would at least get you started.

I know what I want, hence my clarification on taking a step back and looking at it from a general concept of a horn dimension that works best between 50-60 hz, regardless of what driver is used or the size of the sealed chamber.

Quote:
Originally Posted by Ricci View Post

Ok so he is using a custom or modified Sundown Zv4 driver and he is going to put this in a vehicle of some sort for auto competition... etc...You need to identify how much space you have in total for the cabinet how much power you plan on flogging it with and what is the peak frequency of your vehicle typically (50Hzish I would guess)? Do you want something that is listenable or just to put up stupid high numbers?

You mention a 50Hz cutoff and list a super heavyweight excursion driver with an FS below 30Hz and FLH...Your app seems very specific and for this type of thing you can't just start with a driver like that and then force everything else to fit around it. You need to start with the space available and budget...Then define what the system goal is (loud as possible, frequency range to be covered, is some listenability needed, etc..) Then define how much power you plan to have available...At this point start looking at what type/s of system fits into this plan logically(FLH, TH, TL, BP4/6, Vented, PSPCBM, etc...) At this point you would start identifying driver candidates that fit the bill for the app. You may find that there are other choices that would perform much better in the intended cabinet/app.

It is not a Zv4 in any form. It is my own brand of driver, with tooled motor, spiders, and coil. It's a 4" coil driver, not a 3", among other things being different.

The reason I said the driver won't matter as much is because the concept behind the idea is the driver isn't making the pressure at the throat. It is going for maximum output, and I don't' know the frequency yet because I haven't started the build yet, not familiar with the vehicle just yet. I have something like 140 cu. ft. to work with, also why I'm looking for general information to see if it's plausible. This isn't my first SPL rodeo, you CAN force equipment to do what you want it to, I've got a single 8" doing 151.2 on the dash @ 62 hz and its a musical design sub. Normally I'd just do ported or maybe a 4th order bandpass, but this not being my primary SPL vehicle I want to try something innovative. I do have the ability to change the sub as I need to once I get into testing, being as its my company and I designed the subs. But, I want to stick to a stock design till I get into the testing portion.

So, again, forget about the driver used, forget about frequency range, how can I simply calculate the horn size needed (throat, mouth, length, angle, etc) to excel somewhere between 50-60 hz. Surely there has got to be something generic for that, where the driver and chamber size dictates the actual response.
post #17 of 55
Quote:
Originally Posted by EMF Audio View Post

If I can't simply get a horn dimension for that frequency, then maybe a horn isn't what I need to be doing at all.
If the answer was that simple there would be no need for modeling software. HornResp isn't as easy to use as WinISD, but horns aren't as easy to design as direct radiators either. It's hardly rocket science, you just have to put in the time and effort to learn how to use it.
Quote:
I know what I want, hence my clarification on taking a step back and looking at it from a general concept of a horn dimension that works best between 50-60 hz, regardless of what driver is used or the size of the sealed chamber.
Once you do learn how to use it you'll know why there is no such thing as a horn dimension that works best between 50-60 hz, regardless of what driver is used or the size of the sealed chamber.
post #18 of 55
"So, again, forget about the driver used,
forget about frequency range, how can I simply
calculate the horn size needed (throat, mouth,
length, angle, etc) to excel somewhere between
50-60 hz."

it doesn't work that way brother. the only
thing folks could tell you is that the low corner
tends to be around 1/4 wavelength, which for 55hz
would be around 5.2 feet long. the cerwin vega horn
that i posted has a low corner a slightly lower
than that and has a path length of about 6 feet iirc.

also, horns aren't going to function as horns
in the bass region inside a car, but more like
putting the mic inside the horn and sealing off
the mouth.

this can create some weird effects like no bass
right in the center of the "room" or in your case,
the car.

horns are used to couple the driver to the air
load better than the cone can do on its own. the horn
moves the slog of air back and forth, but once you
put it in a car, there is no where for the slog to go.
so it is just pressuring and depressuring the entire
thing and that is what your driver will do in a car
anyways.

last, your comment about efficiency isn't what you
are thinking either. horns have multiple impedance
peaks where the power efficiency goes through the roof
whereas with a sealed or ported there is a single
impedance peak (at least above tuning in the case of
ported).

your best approach to maximizing spl is probably not
a horn, but reducing the air volume in the car to
a minimum and bracing the structure to provide
absolutely a minimum of losses. if the body or glass
of the vehicle vibrates, you have losses. spl in a
sealed container is directly proportional to the
change in volume swept out by the driver divided by
the total volume inside the car.

what you are talking about is akin to putting a horn
inside of a sealed box. again, i'm not sure that
would do anything.

here is the math for spl inside a lossless sealed
enclosure:


Edited by LTD02 - 7/3/13 at 2:57pm
post #19 of 55
You'll have to excuse me for making some assumptions on the driver because that certainly looks like Sundowns new basket, surround, cones, terminals, etc..I didn't pay much attention to the motor the first time. Also the background looks like their shop and there is a 3500 on the wall so I figured Jake atleast helped design it. Anyway...

Let me see if I can explain your request for generic information this way...What size does a vented box need to be for good 30-40Hz performance? How big should the vent be and how long? You'll be using....See what I mean?

Now consider that horns are about 10x more complicated and dependent on the driver than any vented system. One driver may work well with a throat of just 200cm area while another may be complete garbage with that much throat area and may not work right until it has about 700cm. That is just one of about 20 parameters in a horn. You have the expansion ratio, the throat area and geometry, the length and area of each section, the volume of the rear chamber,etc...And this is well before getting into actually building the thing to match the simulation, folding the horn up, making sure there are enough clearances, bracing the hell out of everything, etc...This later stuff is actually the hard part for most. One driver may work quite acceptably in a 50Hz horn that is only 300 Liters in volume while another may not produce anything "good" until it has 2 or 3 x as much total volume. Some drivers just are not suited to some designs as well. It happens. Maybe someone will take the parameters you posted and see what comes out of HR. It really is not that difficult to get the hang of just try a few tutorials and read what the parameters mean in the glossary, plug your parameters in and play around. It has a learning curve but it is not that bad.
post #20 of 55
Thread Starter 
It is the same basket, surround, and terminals, the generic parts of sorts. If you notice, I've got 4 pairs of terminals and 16 tinsel leads. There was a 3500 in the background because that video was shot at Sundown, and I'm a Sundown dealer aside from other ties to Sundown.

I get what you're saying in my request, but I did get a PM from somebody that contained EXACTLY what I was looking for. Throat 1/3 of Sd, mouth as big as possible, at least 1/4 wave length. Since nobody can seem to let go of the fact that the sub will not be at the throat, I'll lead in a little more to the concept. A port will be feeding the pressure into the horn, not the sub. The enclosure behind it will be optimized for the frequency needed, for example, 50 hz. It needs to do 1 thing and 1 thing only, play 50 hz, loud. I've done 160+ dB with 2 15's before, i want to do it with a single 15 or 18.

I am intrigued by the idea of simulating the effect of pressure in a sealed box. Care to elaborate how this happens in a vehicle? I can see if it was IN the horn, but after breaking the plane of the mouth I would think things would change. I've known people to build horns for cars and they worked fine.

For what its worth, I am also wanting to build a small scale version of this concept before building something big, with a single 8". In that scenario I could simulate an interior in front of it to test as well.
post #21 of 55
Thread Starter 
I'll throw this out there too. I know some of you are saying "that won't work", but have you tried it? There was a time when people said "sealed is the way to go for SPL" and not that long ago it was said bandpass sucks for SPL and now the loudest vehicles in the world are bandpass.
post #22 of 55
Any thoughts of making a HT version of any of your drivers? The driver itself is fugly like the sundowns but that could be overlooked if it performed well at home. Or is it more of a slp driver only?
post #23 of 55
Thread Starter 
In actuality, it isn't an SPL driver. It's intended for high power, high output, music. I'm taking function over appearance. The production models do have a chrome motor and a carbon fiber dustcap. As far as making a HT version, it would be possible as they are made to order. I would have to do a little something different on the spiders but I could probably leave everything else the same. I probably wouldn't need 16 leads on it for HT either. You tell me what you feel it should be like and I'll see if it's conceivable or practical.
post #24 of 55
Well, thats cool that it's not just a burp driver. I was in dB drags for over 10 years and personally think burp drivers/vehicles are the biggest waste of time/money possible. They generally sound like garbage lol.
As far as a HT driver, the sensitivity is a bit of an issue, as you said in your video, 3000 watts isn't enough to get what the driver is capable of, you're amp choices will be limited to but a few and even fewer guys that will own them. 6200 watts is just way too much for a HT driver lol, 2 to 4 tinsel leads would be plenty for anything up to 3000 watts or so. they are serious looking drivers and look to compete with the XXX's (which I have 4 of) and I'd personally like to try one if the HT variant came out.... 18" only though, 15"s need not apply biggrin.gif
post #25 of 55
"I get what you're saying in my request,
but I did get a PM from somebody that contained
EXACTLY what I was looking for. Throat 1/3 of Sd,
mouth as big as possible, at least 1/4 wave length."

1/3 of sd for the throat gives a compression ratio
of 3:1. that works for many drivers, but sometimes
it is way off.

here is an example using the lab12 driver. this one
was specified by tom danley for the lab subwoofer
horn project--which may be one of the most popular
early horn builds going.

the top plot has a compression ratio of 1.25:1, while
the bottom plot has the 3:1 that you are talking about.

this is why the guys are saying that you have to model
it up to know what you have there.

"I am intrigued by the idea of simulating the effect of
pressure in a sealed box. Care to elaborate how this
happens in a vehicle?"

all the math is in the picture that i posted.

just use different numbers based on the sd and xmax of
your driver and the volume of the car that you are
pressurizing. or, you could do it backwards and calculate
how much spl you are losing to vibrations of the car
by measuring the actual spl and subtracting it from
the ideal model spl.

" I can see if it was IN the horn,
but after breaking the plane of the mouth I would think
things would change."

at 50hz, the wavelength is about 22 feet long, so you will
have already filled up the airspace in the car before the
wave even leaves the horn. that is what i was getting at.

" I've known people to build horns for cars and they
worked fine."

i don't see any reason why they wouldn't work, but at low
bass frequencies the real question is whether you get any
addtional spl vs a sealed enclosure or not...in other words
is the horn actually doing anything if the driver is already
pressurizing the cabin.



post #26 of 55
Thread Starter 
Quote:
Originally Posted by N8DOGG View Post

Well, thats cool that it's not just a burp driver. I was in dB drags for over 10 years and personally think burp drivers/vehicles are the biggest waste of time/money possible. They generally sound like garbage lol.
As far as a HT driver, the sensitivity is a bit of an issue, as you said in your video, 3000 watts isn't enough to get what the driver is capable of, you're amp choices will be limited to but a few and even fewer guys that will own them. 6200 watts is just way too much for a HT driver lol, 2 to 4 tinsel leads would be plenty for anything up to 3000 watts or so. they are serious looking drivers and look to compete with the XXX's (which I have 4 of) and I'd personally like to try one if the HT variant came out.... 18" only though, 15"s need not apply biggrin.gif

In order for me to get the Fs down I'd have to loosen up the spiders, which would also reduce power handling, probably down to 3000-4000 watts. If you'd like to talk further about that possibility, email me sales@emfcaraudio.com.

Quote:
Originally Posted by LTD02 View Post

"I get what you're saying in my request,
but I did get a PM from somebody that contained
EXACTLY what I was looking for. Throat 1/3 of Sd,
mouth as big as possible, at least 1/4 wave length."

1/3 of sd for the throat gives a compression ratio
of 3:1. that works for many drivers, but sometimes
it is way off.

here is an example using the lab12 driver. this one
was specified by tom danley for the lab subwoofer
horn project--which may be one of the most popular
early horn builds going.

the top plot has a compression ratio of 1.25:1, while
the bottom plot has the 3:1 that you are talking about.

this is why the guys are saying that you have to model
it up to know what you have there.

"I am intrigued by the idea of simulating the effect of
pressure in a sealed box. Care to elaborate how this
happens in a vehicle?"

all the math is in the picture that i posted.

just use different numbers based on the sd and xmax of
your driver and the volume of the car that you are
pressurizing. or, you could do it backwards and calculate
how much spl you are losing to vibrations of the car
by measuring the actual spl and subtracting it from
the ideal model spl.

" I can see if it was IN the horn,
but after breaking the plane of the mouth I would think
things would change."

at 50hz, the wavelength is about 22 feet long, so you will
have already filled up the airspace in the car before the
wave even leaves the horn. that is what i was getting at.

" I've known people to build horns for cars and they
worked fine."

i don't see any reason why they wouldn't work, but at low
bass frequencies the real question is whether you get any
addtional spl vs a sealed enclosure or not...in other words
is the horn actually doing anything if the driver is already
pressurizing the cabin.




Not discrediting your knowledge here, but based on what I know, I don't think the theoretical math is lining up with reality. I know you're saying math this and math that, but for this application, the math doesn't work. You can take what I've been doing in my car for a year and the math doesn't add up, because simulation isn't reality. Within the confines of a car it isn't as much about wavelength as it is pressure. If I can generate the pressure from the horn so it resonates at the frequency desired, that pressure will continue into a confined space.

Now in terms of the throat opening, would it be possible to make it large and shrink it without changing the angle of the horn, or would that be counter-productive? Basically, so I can keep the same horn shape, but so I can tweak it inch by inch.
post #27 of 55
"You can take what I've been doing in my car
for a year and the math doesn't add up..."

that is an intriguing comment. i would be
interested to know what you are doing in your
car where math doesn't add up.

i can't think of any examples where math
doesn't work. from tiny two-way bookshelves
to the 40 box vertical subwoofer line array
that metallica uses, the math seems to work
everywhere.

"Now in terms of the throat opening, would it
be possible to make it large and shrink it
without changing the angle of the horn, or
would that be counter-productive? Basically,
so I can keep the same horn shape, but so I
can tweak it inch by inch."

no reason why that couldn't be done.
post #28 of 55
Quote:
Originally Posted by LTD02 View Post

"You can take what I've been doing in my car
for a year and the math doesn't add up..."

that is an intriguing comment. i would be
interested to know what you are doing in your
car where math doesn't add up.
+1. The math always works. One's understanding of the math, maybe not.
Quote:
at low bass frequencies the real question is whether you get any
addtional spl vs a sealed enclosure or not...in other words
is the horn actually doing anything if the driver is already
pressurizing the cabin
Horns work just fine in cars, they are after all just small rooms.
Quote:
I did get a PM from somebody that contained
EXACTLY what I was looking for. Throat 1/3 of Sd,
mouth as big as possible, at least 1/4 wave length.
Unfortunately, they were incorrect.
Quote:
A port will be feeding the pressure into the horn, not the sub. The enclosure behind it will be optimized for the frequency needed, for example, 50 hz.
I think I know what your intent is. It won't work. Been there, done that. One other bit of advice, if you want to get maximum output at 50Hz start with a driver Fs no lower than 60Hz and Qes no higher than 0.3.
post #29 of 55
i was thinking about your problem:

maximum spl in a car with as few
of drivers and power as possible
at a single frequency.

to any scientist of acoustics, they
would say create a resonant chamber,
or, lots of them.

so...

in theory, why don't you just turn
the entire cabin into a resonant chamber
by porting it or using passive radiators
to the outside of the vehicle? :-)

so some sort of vented or bandpass design
would excite the cabin of the vehicle,
just like everybody is doing right now,
while the energy would then be further
enhanced by the resonant feedback from the
port or the p.r. to the outside of the
vehicle.

if you use such a design and win, let me
know, an spl world record would be a fun
item to add to the resume as would seeing
a car with a giant smokestack sticking out
of it win an spl competition. :-)


........

"Horns work just fine in cars, they are
after all just small rooms."

bill, he mentioned using up to a 50"x53"
mouth firing into a car cabin. i was simply
suggesting that might cause the cabin to
function more like an extension of the horn
with a closed mouth, then a horn firing
into a room.
post #30 of 55
Quote:
Originally Posted by LTD02 View Post

i was thinking about your problem:

maximum spl in a car with as few
of drivers and power as possible
at a single frequency.

to any scientist of acoustics, they
would say create a resonant chamber,
or, lots of them.

so...

in theory, why don't you just turn
the entire cabin into a resonant chamber
by porting it or using passive radiators
to the outside of the vehicle? :-)

so some sort of vented or bandpass design
would excite the cabin of the vehicle,
just like everybody is doing right now,
while the energy would then be further
enhanced by the resonant feedback from the
port or the p.r. to the outside of the
vehicle.

if you use such a design and win, let me
know, an spl world record would be a fun
item to add to the resume as would seeing
a car with a giant smokestack sticking out
of it win an spl competition. :-)


........

"Horns work just fine in cars, they are
after all just small rooms."

bill, he mentioned using up to a 50"x53"
mouth firing into a car cabin. i was simply
suggesting that might cause the cabin to
function more like an extension of the horn
with a closed mouth, then a horn firing
into a room.

as far as i know installing ports or otherwise venting the cabin of the car/truck is illegal for competition, then again its been many years since i have actively competed so who knows.
going to keep an eye on this thread though as ill be looking to build an over the top system in a truck i just picked up
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