DIY bass horn build...Up next - Page 15

Somehow I missed these questions a month ago...I just saw them when I came to update the CEA2010 data.




I guess it should certainly be loud enough if you use 2-4, for most applications, but really the cab loading is lower than needed, and it is really big and heavy. You could gain a lot of top end output and efficiency in the meat of the live sound range if you moved the corner up a whole octave higher. You know like the Othorn. Basically the Gjallerhorn would be OK 40-90hz, but some smaller, lighter cabs can compare favorably over that range. It isn't until the octave and a half below that range that it starts to set itself apart from the normal live sound gear. In most live or SR instances that sort of content is pretty much non existent anyway though. Everybody usually filters below 30hz pretty heavily to protect their equipment and cabs and live music doesn't have much below 30hz anyway, so the extra extension is wasted in that application.

Don't get me wrong I am using them for live sound right now but they are stationary, it is only for myself and I run the system.






Violently. The pair that I have have been pushed in the >10,000cu ft very lossy space they are in a few times, just having fun with them and it is more than plenty for that space. They can shake the entire building and easily pressurize the space with Jurassic Lunch and I only have about 1300w of amplifier going to each one. They aren't even using all of that power. Some people say there is no such thing as overkill, but seriously the Gjallerhorn is simply not needed in any sort of domestic environment. Even one will do reference levels to 16hz in a normal room without breaking a sweat. I guess if you had a screen wall it might make some sense, but most of the time I doubt that you would use much of the available headroom. Most situations would be better served with multiple smaller, more modest subs scattered about the room to smooth the response.

I'd be lieing if I said that I wouldn't like to experience what they would do "opened up" in someone's HT room just once though. Maybe someone will have a GTG I can drag one to.

Here are the CEA2010 distortion results to go along with the basic output spl numbers.


Gjallerhorn CEA2010 output. Referenced to 2 meters, rms, outdoor groundplane.

10hz-----90.2db-----Distortion
12.5hz---105.2db----Distortion
16hz-----118.3db----Amplifier
20hz-----122db------Driver noise
25hz-----124.9db----Driver noise
31.5hz---125.8db----Driver noise
40hz-----128.4db----Amplifier
50hz-----127.2db----Amplifier
63hz-----130.2db----Distortion
80hz-----130.9db----Amplifier
100hz----131.1db----Amplifier
125hz----123.6db----Amplifier



















Here is 10hz distortion at just about maximum output. Obviously this is not clean or a passing result. This is way below the cab loading and the distortion is very high, but it shows what the Gjallerhorn can do dynamically down that low before getting the driver into mechanical trouble.

93.2db at 10hz

The signal is the standard CEA2010, 6.5cycle duration, Hann shaped, 1/3rd octave bursts. 100 and 125hz are very short duration. Nothing more than a blip. The program usually just records them like that.

I ran out of amp at 16hz, 40, 50, 80, 100 ,125hz. There were driver distress noises that made me leery of extra level at 20,25,31.5hz despite low distortion results. Distortion limited 10 and 12.5hz and 63hz. That is if I remember all of this right.

John with this type of burst testing even a 1" dome tweeter can withstand many kilowatts of input in certain frequency ranges. These same power inputs can cook even an LMS coil easily. It is only the very short duration that allows them. Every sub is going to be amplifier limited at a lot of frequency bands.

I like Ed's old charts. I had already been listing the limiting factor for long term signals on my Excel charts. It does make sense to include it for cea2010 as well.

Mike,
The program runs under a software package called IgorPro. Powerful and very deep software for audio. It is sort of like a measurement and graphical presentation tool kit. What I mean by that is it is sort of open for the user to set up routines or experiments or setup what you want to do. It is $600 for a license if I remember right. The experiment that runs this was created by Don Keele. It is not available for purchase anywhere still. You would also need some other minimum equipment to run it foremost being an SPL calibrator.





I will give the plans to anyone who wants to build it. All you have to do is pm me your email.

I would like to put 2 in the back of a shortie Astro van and see what would happen on a termlab at 16hz myself. Just for fun of course.

Well....That is a possibility I guess. I am stabbing at the distance from the floor to the mic but it was probably around 40 to 45". I wouldn't expect the reflection to cause that strong of a cancellation but maybe so. I also had a thought about a reflection from the mouth back into the horn which would also be 45" or so. I only plan to do one more test on these that requires me to drag one outdoors. If I remember I will try to check this again. Right now these are under JBL 4675-c's which aren't too easy to lift down off of them.

Good luck Mike but I am not sure how close the results would be. There has been significant differences shown between even the "official" setup used by different parties. I tried to use ARTA and a peak hold setup to capture something similar previously and that was just not the same. Some of the results were quite close and others were way off between the 2 different ways. If you want to try I would suggest getting the signal correct first. Good luck!

Might as well throw this in here. This is the new format for CEA2010 results I will be using.



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Agreed. I mentioned this to John long ago. If he can get harmonic distortion measurements during the sweeps implemented that would be huge for me. I use ARTA for that now. STEPS is great but way too brutal for high power. The other thing that I asked him about was beefing the generator up even further and allowing multiple sine wave output. Similar to NCH tone generator. Also the ability to do ascending or descending sweeps for measurements would be cool. REW has come a long, long way already.

Something near 14Hz and 18 or 24dB octave roll off would be recommended.

Sure.