A Tapped Horn Experiment

[Triticum Agricolam]

So if you had a mayhem 10" would you throw it into one of these horns?

I'll double check when I get home tonight, but I'm pretty sure that sub has WAY too much motor force and would have a frequency response like the Himilayas. It might be possible to come up with a horn design it would work well in, but this one probably isn't it.

[Mike Gann]

Nice design, always learning new things about horns when I see your posts. I used to be interested in T-lines until reading that they're basically gimped horns. Makes me wonder if that's what's happening with Patrick's large ported sim, the port is so large it's basically a T-line which is basically a horn which would put the response near each other. I don't know though just my observation. What are you using to test your stuff, and how do you setup outside? I'm currently using a cheap Dayton Audio iMM6 with Audiotools app but the graphs are not as pretty as yours. When you do a 1w test are you clamping an amp, maybe running a large speaker wire out of your car and into a grassy field somewhere?

My first look at your design I thought the speaker blocking the mouth would cause an issue, or at least port noise on those sharp angles, but you mentioned the air velocity is so low it doesnt matter. So motor force is a big player in horns? Does that cause it to bottom out if it's too powerful? That's always been something I wondered about with taped horns, is if the speaker is getting any kind of support to prevent mechanical limits. Just like T-lines I hear you're suppose to put less than half power on them, can you put your horn on rated power? I guess if the resistance goes up like mentioned, it can handle rated?

I bet it's hard to find a driver with the right motor force because they're all designed to be put into bass reflex designs, maybe you should look into designing your own drivers and focus on horns? Maybe that's also why the FLH is performing better, because too much motor force will actually help in that case? Karkov mentioned that maybe horn design will get more common in car audio but what I've read is that horns were very popular in the genesis of audio and we're actually moving away from them as power and speakers become cheaper and bigger. Horns were always the most efficient design to be able to reproduce bass in an speaker with the hardware they had back then. Also horns seem to be more of a full range speaker thing, but these days we focus on specific frequency ranges which bassreflex/bandpass seems to be good for. Like you said a large bass reflex box should not play higher ranges as efficiently, but given the application this is fine for most people. It would be very cool to see what you can do with todays technology on a speaker made for horns.

Personally I'm starting to think I'll never build another bassreflex again, as even a bandpass seems to be a better choice for the same application. I hope to make a horn for my garage when I get around to making a system for it, I'm definitely going to be asking you about my speaker choice and more. Ha I believe I came on here hours ago to post a question about batteries, I better go do that..

Also, where can I get this EasyHorn I can't find it.

[Mike Gann]

This is what I think of when I see folded horn

That thing certainty is interesting. I like how the guy bolts the door shut. With what he had done to it it's not really a vehicle any more.

I thought bracing was illegal in comps?

[Jessica]

This is what I think of when I see folded horn

That thing certainty is interesting. I like how the guy bolts the door shut. With what he had done to it it's not really a vehicle any more.

I thought bracing was illegal in comps?

there are classes, extreme class is basically no hold barred. of course some sanctioning bodies have rules even then. Of course if you do some reading, those bodies are getting hate from a shit ton of people

[Triticum Agricolam]

So if you had a mayhem 10" would you throw it into one of these horns?

I'll double check when I get home tonight, but I'm pretty sure that sub has WAY too much motor force and would have a frequency response like the Himilayas. It might be possible to come up with a horn design it would work well in, but this one probably isn't it.

Yeah, the Mayhem won't work at all. It has too much motor force, but the bigger problem is it has too stiff of a suspension (too small of Vas). Here is what you get:

The dark line is the Mayhem, the lighter grey line is the E-10. The Mayhem would sound like hell.

[Triticum Agricolam]

Nice design, always learning new things about horns when I see your posts. I used to be interested in T-lines until reading that they're basically gimped horns. Makes me wonder if that's what's happening with Patrick's large ported sim, the port is so large it's basically a T-line which is basically a horn which would put the response near each other. I don't know though just my observation. What are you using to test your stuff, and how do you setup outside? I'm currently using a cheap Dayton Audio iMM6 with Audiotools app but the graphs are not as pretty as yours. When you do a 1w test are you clamping an amp, maybe running a large speaker wire out of your car and into a grassy field somewhere?

My first look at your design I thought the speaker blocking the mouth would cause an issue, or at least port noise on those sharp angles, but you mentioned the air velocity is so low it doesnt matter. So motor force is a big player in horns? Does that cause it to bottom out if it's too powerful? That's always been something I wondered about with taped horns, is if the speaker is getting any kind of support to prevent mechanical limits. Just like T-lines I hear you're suppose to put less than half power on them, can you put your horn on rated power? I guess if the resistance goes up like mentioned, it can handle rated?

I bet it's hard to find a driver with the right motor force because they're all designed to be put into bass reflex designs, maybe you should look into designing your own drivers and focus on horns? Maybe that's also why the FLH is performing better, because too much motor force will actually help in that case? Karkov mentioned that maybe horn design will get more common in car audio but what I've read is that horns were very popular in the genesis of audio and we're actually moving away from them as power and speakers become cheaper and bigger. Horns were always the most efficient design to be able to reproduce bass in an speaker with the hardware they had back then. Also horns seem to be more of a full range speaker thing, but these days we focus on specific frequency ranges which bassreflex/bandpass seems to be good for. Like you said a large bass reflex box should not play higher ranges as efficiently, but given the application this is fine for most people. It would be very cool to see what you can do with todays technology on a speaker made for horns.

Personally I'm starting to think I'll never build another bassreflex again, as even a bandpass seems to be a better choice for the same application. I hope to make a horn for my garage when I get around to making a system for it, I'm definitely going to be asking you about my speaker choice and more. Ha I believe I came on here hours ago to post a question about batteries, I better go do that..

Also, where can I get this EasyHorn I can't find it.

Here is where you can get EasyHorn: http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/36538-eazy-horn-spreadsheet-dum-everyone.html

So when I measure outside I use a Dayton UMM-1 calibrated mic, my laptop, and a Behringer NU3000DSP amp. I've got a IMM-6 too, but the software I use is for PCs so that's where the UMM-1 comes in. The software I use Room EQ Wizard. Its free and there are lots of good guides on there on how to use it. Its very powerful and works as well as anything for this kind of testing. When you setup outside you want to be far away from buildings and other things that will reflect sound. Middle of a field is ideal. I'm usually about 50 or 60 feet away from any buildings when I do testing. If I could get farther away it would probably be better.

To get the 1 watt at 1 meter measurement requires some careful setup. The power level is based on the nominal impedance of the driver being tested. So if testing a 4 ohm speaker you apply 2 volts of input power. An 8 ohm speakers gets 2.83 V, a 2 ohm gets 1.41 V, a 1 ohm get 1V, etc. Now testing at one meter can be troublesome because if your mic placement is off just a couple inches it can skew the results. Also with ported boxes you have to make sure the distance between the sub to the mic and the end of the port to the mic is exactly the same. A way to make this easier is to test from farther away, which lessens the effect of any mismeasurement or misplacement. To compensate for the increased distance you increase the output voltage so you are getting the same level of output at the mic as you would if it was at one meter. This is pretty easy to figure out. If you put the mic 3 meters away, you multiply the voltage coming out of your amp times 3. If the mic was 5 meters you would multiply the volts times 5.

I did this last round of testing at 3 meters and it worked OK. I think next time I'll take it out to 5 meters. I've heard Danley Sound Labs tests their stuff at 10 meters, which I'm sure is a better way to do it, but it takes long cables and is more of a pain to setup.

When it comes to finding subs that work well in horns motor force is important, but so is Vas (suspension stiffness) which is something I forgot to mention earlier. In fact Vas might be the more important of the two. A lot of higher power rated subs have really stiff suspensions. This will make them very difficult to use in a horn of reasonable dimensions. The low Vas actually requires a smaller horn, but it would be so small you wouldn't be able to build it and make it work.

I think the main reason the audio world has moved away from horns is power is cheap now. Back in the days of tube amps you needed the efficiency that horns provided since tube amps are low power. That requirement is gone now and horns are more expensive to build than bass reflex boxes and cheaper tends to win. I really like how horns sound and I'm starting to get to the point that I may never build another bass reflex sub for my own usage if I don't have to. That's not to say bass reflex subs aren't still useful, if you want to get as loud as possible over a limited frequency range, nothing does that better than a ported box does, but for my own use there is a lot more to the performance of a sub than just how loud it gets.

[Triticum Agricolam]

how does the performance of this compare to the autotuba from Bill Fitzmaurice?

The AutoTuba is tuned to 40 Hz, so this horn should have more low end output. The AutoTuba might beat it higher up though. I'm in the field right now but when I get home I can compare the two in HornResp and post the results.

I've actually got an AutoTuba sitting around. I'll drag it out next time I'm measuring and then we will know for sure how they compare.

Cool.

Here is how the AutoTuba models compared to my Sundown horn:

AutoTuba is the dark line, my horn is the lighter one.

Its pretty much like I said earlier, my horn plays a lot lower, the AutoTuba is louder higher up.

What Patrick said about the Autotuba is pretty much spot on. Its high efficiency frequency range is too high to really be useful. In the design's defense though you can build an AutoTuba to be a lot of different sizes. If you get the right size with the right sub in it it can perform pretty well. I liked the way mine sounded when I had it in a vehicle.

[Patrick Bateman]

So if you had a mayhem 10" would you throw it into one of these horns?

I'll double check when I get home tonight, but I'm pretty sure that sub has WAY too much motor force and would have a frequency response like the Himilayas. It might be possible to come up with a horn design it would work well in, but this one probably isn't it.

Yeah, the Mayhem won't work at all. It has too much motor force, but the bigger problem is it has too stiff of a suspension (too small of Vas). Here is what you get:

The dark line is the Mayhem, the lighter grey line is the E-10. The Mayhem would sound like hell.

I think you guys will like this post. Here's how you make these monstrous drivers work in a horn.

In TA's post, he showed that the Mayhem driver is massively peaky in his horn. The reason that the Mayhem is massively peaky is because the VAS is too small. (As TA pointed out.)

But the fix is easy. Just as you would use a smaller vented box if the VAS is too small, you can shrink your horn because the VAS is too small.

Here's the response and the excursion of TA's box with the Sundown Audio E10, versus TA's box with the Ascendant Audio Mayhem 10" BUT WITH THE SIZE REDUCED BY 67%.

Neat, huh?

You basically get the exact same response curve, the exact same displacement, IN A BOX ONE THIRD THE SIZE.

But wait! How is this possible? This breaks Hoffman's Iron Law! Alas, there is no free lunch:

Although the response curve and the excursion is identical, the Mayhem is sucking up way more power than the E10. The Mayhem dips down to 1.3 ohms; the E10 dips down to 4 ohm. So the Mayhem is getting three times as much power as the E10. There's no free lunch; you can reduce the box size by two thirds, but you'll have to ratchet up the power by three times to make up for it.

If any of this doesn't make sense, let me know.

[ckeeler11]

Maybe I'm looking at it wrong but when you shrink the horn doesn't the output suffer? You took the big old beefy Mayhem and the output is pretty much the same a the E10.

[Patrick Bateman]

Maybe I'm looking at it wrong but when you shrink the horn doesn't the output suffer? You took the big old beefy Mayhem and the output is pretty much the same a the E10.

That's exactly right!

You can't break Hoffman's Iron Law. The Mayhem will work in a box that's one third the size of the E10, but it needs three times as much power to get to the same SPL.

That might sound like a shitty deal, until you notice that the Mayhem has more excursion. So if you can afford a really REALLY big amp, you can get louder than the E10 using a box that's much MUCH smaller.

I think that's one of the reasons these exotic enclosures are compelling if you have a lot of money to burn; you can squeeze an extra 5-10dB out of a driver IF you can afford to buy a ridiculously large amp.

Keep in mind, that last few decibels is going to cost a LOT OF MONEY. You could easily spend an extra $500-$1000 to get it. (Due to the higher cost of drivers with very very low VAS, and the higher cost of multi-kilowatt amps.)