DIY bass horn build...Up next - Page 7

Bill, remember earlier in the thread where you talked about a TH having an advantage with large drivers...

Hey Ricci,

I've been meaning to chime in sooner, but work has been way crazy hectic lately. I've actually been working on almost the exact same application for a few months now so I think it would be interesting to compare notes. I was actually targeting 20Hz to 150Hz, but scaling it down would be no problem.

However, what is driving the 380L requirement? And what are the SPL targets? The idea I've been working on is meant to be a modular/scalable approach, and the target transportation size should be smaller than 380L and weigh less than 100lbs. However, when unpacked, I think it's going to be larger. I'll have to crank the numbers later.

And then how many cabs were you going to build? I think you mentioned only one, but that wouldn't be very good for a FOH system....is this for your drum monitors on stage?

Btw, have you read Keele's paper on the comparisons between horns and vented cabs of the same volume?
http://www.xlrtechs.com/dbkeele.com/...%20vs%20DR.pdf
I'm not sure I agree with Keele's conclusions, but I thought I'd throw the article out there as a discussion point.

mbentz, thanks for posting that paper. fwiw, i agree more or less with their conclusions. it is humbling to see how right these guys were about the science of audio in the days when they were using typewriters and manually drawing characters and equations into their papers.

Mbentz, good paper...thanks! I have a 3 hour flight to enjoy it and read it 10 times before anything remotely sinks in.

Use the 'ignore user' option. Life's too short to waste time wading through the chaff to find the grain.
It's a bit of a tossup as to whether it's an advantage per se. One trade-off of the tapped design is that they run with higher excursion. You get around that with a larger Vd. You can get that with larger/more/more expensive drivers; if it's one of the first two choices the lack of a rear chamber keeps the overall box size down.

Circa 1976, when amps started to break the 200w barrier and woofers the 2mm xmax barrier, Keele's conclusions made perfect sense. They still do to some extent. But you can only go so far using power and excursion to reach a desired output before said excursion gives unacceptable distortion. And there's still the matter of cost. Kilowatt amps today are common, but not free, and drivers capable of making use of those kilowatts don't come cheap.

On that point Keele nailed it. From a given cabinet size the direct radiator will win. The trade off comes with the cost of the power and drivers. For a given power input and driver complement the horn will win; the trade off comes in the size of the cab. On a simplistic level if you've got plenty of money and minimal pack space use direct radiators; plenty of pack space and not much money, use horns.

If you just go with SPL the Keele paper is right. There will be a few exception, but there always are.

If you look beyond SPL, and at the actual signal reproduced at said SPL another issue comes up.

Then the question is what is causing said difference? How much is from the horns folds, or it's acoustic load on the driver? How much is just from the excursion reduction? Do the same methods used on a direct radiator to control distortions carry over into a horn? If so, to what degree?

Every speaker will be different in the exact details. But one can generalize that when the same SPL is achieved with less excursion distortion will be lowered. And the bends in a folded horn do act as low pass filters, so there will less above bandwidth harmonic output. That being the case the lowest possible distortion will be realized with a folded horn. A tapped horn will come in higher due to the longer excursion for equal SPL and the cone that's not hidden around the bend(s), with direct radiators having the highest.

Those are all known data points, but they do not answer the questions posed. You also left out the last two, which are the key points.

Nice to see you still have the 1976 thinking, the TC LMS 5400 has a hellova lot less distortion + wider bandwidth in about the same package ( 7 cubic foot ) as the Klipsch Lascala.

To borrow a catch phrase from Oldsmobile: ' These aren't your father's transducers '

The LMS 5400 delivers in half space 1 meter 114 db with 60V at the terminals. You still can use a lot more power than that through it.

EVERY driver out there is so much more refined than the devices available even 20 years ago, that it's not even funny. Suspension linearity, motor linearity, inductance linearity.... heads and tails above what was the accepted 'norm' back then.

Heck, the LMS digs an octave lower than the Jubilee with a cabinet half the size, and still has lower distortion and about the same max SPL. The only downside is you can't get up to 1kHz with the LMS.

That said, I would really love to see some distortion/spl comparisons between the Jubilee and the Acoustic Elegance drivers, which can operate on the same bandwidth (and arguably do a better job at it too...)

At the end of the day, I think it makes more sense to talk about audible performance metrics like maximum SPL, distortion, polars, etc... rather than focusing on inaudible metrics like power and efficiency. Heck, in the electronics world, the best sounding gear tends to be the least efficient...throwing extra bias current at a fidelity problem is always the easiest solution - definitely not the most elegant engineering solution, but it's just an example of how efficiency doesn't directly correlate to fidelity.

At the same time though, I still believe horns should always be better....but that comes from having extra control over the polars and usually lower distortion.

Btw, it's rather straightforward to predict the levels of harmonic distortion generated at the throat. I might also mention that I would be worried about extra air disturbances on some of the designs offered where the driver is firing sideways into a narrow slot...think of how DC air flow is gonna have to bend, and that bend is going to create turbulence...just something to think about.

Ricci,
I would hate to read through your PMs...

And what do you think will happen when a modern transducer is put into a folded horn?

You still have smaller bandwidth from low pass filtering due to the folds in the horn, as well as the large ripples in FR.

Drivers have changed, yes. A modern driver in a horn could shift the bandwidth up or down in frequency and possibly change the maximum output some.

Unless you are building a straight bass horn, filtering due to folds is still going to be an issue.

Riddle me this: what happens when large bursts of low frequency energy is fed into a horn with a small throat / large compression ratio?

to ricci and all,

you guys are such unbelievable donkeys; i can't believe that you don't see things such as i do, as a master genius of all things. that paper is so stupid as it only considers efficiency of a system and not the limits of the system's performance. like all peer reviewed research it is just morons, reviewing morons about moronic research. anybody, and i mean anybody, who thinks that they know more than i do about audio is fooling themselves in the worst possible way.

as for that paper, who cares how efficient a system is at one watt if it only has one watt of power handling? only lemming peons from the 1970's would use drivers that have 2mm xmax. i'm superior to that. if you can't figure out why, you are stupid, ignorant, or delusional. choose two of three.

most folks around here ride the short bus, so it is no surprise that you are king of the special olympics ricci. can't speak for your followers, but the leader is typically more smarter than his followers. draw your own conclusions about them.

ricci, lol, you can't even figure out how to get a hair cut and you expect to lead the free audio world? as they would say in my homeland, нет. as they might say in your backarse language...not!

once the enclosure size is spec'd, then the driver actually matters. kind of like my panamera. excursion and power handling may not mean much to you idiots but in the world of auto racing it can...and it does. my porsche gt2rs packs 650 hp into a light weight motor, unlike your american fat hinies and its torque curve is as flat as salt lake. i was thinking about moving back to the soviet union, but...umm...err...[silence]

get with the program ricci and all you stupid americans. build a real sub with 50,000 tweeter units and when you do, don't even post it because it would be an insult to geniuses like me.

and if kyle is lurking, you don't know jack either. your subs are like crutches for men with broken legs and limp d_cks. i am the audio equivalent of viagra. i am the god of audio fertility. if you think otherwise, it is because you are delusional and confused.

some have called me YHVH, but you may call me vas.

hahahahhahahhhahhahahhahahahahahahaaaaa.....

One man's issue is another man's design goals. My goals when designing a sub is to limit bandwidth and filter above bandwidth output. Folded horns can do just that, so that's why I employ them.
OTOH if one desires a wide bandwidth folded horn for midbass/midrange use that also can be realized with the proper horn geometry.

LOL, haha... subtle.

speaking of the salt flats here is a pic of me on the Bonneville raceway last week:

http://www.box.net/shared/static/hd3xhffmyj.jpg

and the aftermath of two runs where i hit my 155 mph limiter.

http://www.box.net/shared/static/lrxqo2khdl.jpg

yes LTD that's "burger king" sign reflecting in the windows. grilled chicken salad was the best i could do given the situation.

those salt flats are probably the only thing America is good for

Nice car! I love BMW's. I want an M3 and/or M5 like there was no tomorrow.

don't forget this baby:

http://www.bmwusa.com/Standard/Conte...HClfplbPlEXg==

but Panamera is still better ...

Oh, sure, can't forget the Alpina.

I'm sure there are "better" cars in one way or another. Though, for me, the BMW will always be 'The Ulitimate Driving Machine'.

vas, this is what ricci was talking about. you have a neat car, but why are you posting pics of your car in his horn loaded subwoofer build thread?

because he called me obtuse now i am butchering his thread in retaliation

something that was missed in that paper is performance at the extremes. it more or less sets hoffman's iron law, but it remains silent on where a given design may give up the ghost (either in spl or distortion). two designs may be equally efficient, but the one with 2mm xmax is going to run out gas long before the one with 38mm xmax.

bfm keeps suggesting that distortion is related to excursion. is 10 mm excursion the same in an eminence driver as it is in an lms? i think not. i'm interested to see how this horn performs once the driver gets moving significantly. i've mentioned before that i think this thing is a linear spl monster in the making. many folks seem to be crapping all over ricci's design. i just don't understand why. 130db @ 30hz with neglible distortion.