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Old 30th May 2011, 02:45 PM   #21
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It is compromised as every design is. Nearly every horn is undersized to some extent. This is about the largest cabinet that I could put up with. I tried to get away with just enough bracing as necessary. If I had it to do over there would be a few extra braces in the middle section. The design doesn't really allow bracing of the access panel area. It is by far the most resonant area. Fortunately I will be sitting the subs in such a manner that it is the bottom panel on the floor.
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Old 30th May 2011, 05:05 PM   #22
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any measurements of them in action??
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Old 30th May 2011, 07:49 PM   #23
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Not yet. Give me a couple of weeks and there will be a stupid amount of info.

Happy Memorial day everybody.
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Old 31st May 2011, 02:43 PM   #24
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Quote:
Originally Posted by revboden View Post
I'd try putting a reflector plate in the back of the mouth where that triangle brace is. I'd bet a buck that'll help with the null.

cheers,
Rev.
I just noticed this edit. That is a good idea. I will try this and see what happens. That is an easy mod if it works. I will also try some strategic placement of damping material and see if that has effect as it is also quick and easy to determine if there is any worth. I am also wondering whether simply placing the access panel on the floor may have some small effect. I took the FR measurement with the sub upside down from normal operation with the access panel up towards the ceiling to get the mouth away from the floor. The sub was in the center of the room and the mic was about 3cm from the plane of the mouth. I used a pretty hot drive level. The access panel area does act quite "live" when putting a lot of level through the horn.
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Old 31st May 2011, 03:21 PM   #25
tb46 is offline tb46  United States
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Location: Texas
Hi Josh Ricci,

This looks like a great project, thanks for sharing.

As to: "...access panel area does act quite "live"..." I have in the past stiffened panels successfully with permanently attached ribs glued and screwed to the panel, and with removeable ribs going accross the panel attached with bolts, and sealed with foam tape. Putting ribs on the inside of the panel should be an easy retrofit.

Regards,
__________________
Oliver
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Old 31st May 2011, 06:53 PM   #26
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Quote:
Originally Posted by Josh Ricci View Post
Well in some ways I am a little disappointed that the top end is not as good as hoped, which would've been merely rough to begin with instead of plain old beat up. I was hoping for it to be useful up to 100hz maybe with help from EQ. The null at 100hz is my biggest let down.

Also the cab is solid as a rock except for the bottom by the access panel where it is quite resonant. I knew this would be the case since the nature of the design didn't really allow any bracing in there and it is right by the driver back wave. The positive about that is that it is the bottom of the cab and in my application will be sitting on the floor with the full 300lb? weight on it. It won't be a problem in that case. I didn't wring the thing out but I did give it a little juice and thus far it doesn't appear that there will be any broken cone from horn pressure shenanigans. Its an angry little beastie. It slappa da bass around like it just don't care mon! . I can't really say that I am surprised by much of this. Par for the course so far.
Josh,

“Little” beastie ?
Impressive build !

You seem to be beating yourself up over a 5 Hz wide 100 Hz (out of the intended pass band) dip.
The DTS-10 has a deeper and wider response dip from around 105 to 125 Hz, and the Gjallerhorn seems to have a smoother response compared to your DTS-10 measurements.

A ramp in the last turn as suggested is worth a try, but probably is not going to cure the null. As far as the access panel vibrations, you might use strategically placed rubber feet in that area, the weight of the cabinet will be concentrated more on the center area if you sand a couple millimeters off the outside four feet. Sand them down until the outside feet are just carrying a few pounds of the weight.

Hope you don’t get cone sag problems, that is a lot of weight hanging down 24/7.

Speaking of your measurements, I notice DSL’s DTS-10 chart averages about 101.5 dB SPL from 20-50 Hz, while your chart averages only 87.5 dB. Taking the 6 dB drive level difference into account still leaves around an 8 dB sensitivity difference between your and Danley’s measurements.

The usual DSL tests are done using 28.3 volts at 10 meters outdoors, but the DTS-10 chart says “Danley Shop”.

I asked Tom Danley about that level disparity in some E-mail correspondence, but he did not reply.

Do you have any idea what would be responsible for the large disparity?

How does the Gjallerhorn sensitivity compare to the DTS-10 ?

The Gjallerhorn seems to roll off a bit steeper below 20 Hz than the DTS-10, any guestimate of how much more clean output it has over the DTS-10 above 20 Hz?

Art Welter
Attached Images
File Type: png Gjallerhorn.png (126.6 KB, 852 views)
File Type: png DTS10:LMSR.png (121.8 KB, 804 views)
File Type: png DTS 10 DSL.png (103.8 KB, 789 views)
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Old 1st June 2011, 01:42 AM   #27
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I don't have an answer to the dts10 question yet. I am getting ready to do some additional tests on those to try to answer a few questions I have. For one thing I measured the voltage at the amplifier originally and it has 60ft of cable out to the sub. That may account for some of the rest of that difference after the 6db less drive voltage, but no where near all.
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Old 1st June 2011, 01:50 PM   #28
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First off, love the design! I have followed several of your threads! I found this over on HTS first. Looks amazing and might be a great option for folks who have the room. I do share one concern in regards to cone/spider sag. You might want to contact Thilo at TC Sounds and see what he says, but I do know that their warranty explicitly does not cover sag...

Don
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Old 1st June 2011, 05:42 PM   #29
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I am not that concerned with sag at this point. It did not get any mention with the TC guys. I'm just hoping the drivers will survive high output use and the cabs actually work well. Besides these will be moved around with some regularity. Also there is nothing that prevents using the subs laying on their sides. I made sure that I had room for them that way as well. Depending on how some things turn out that may be the way that they end up anyway. I don't actually have them placed in what will be the usual area yet still have a lot of fiddling to do before I rearrange all of that. They will be back in a corner with a bunch of other gear either on or around them and it will be a tight fit.



On another subject .

How does everyone calculate delay needed for a TH? For a FLH this would be easy but since the TH is driven from 2 different parts of the path length is it still the same or modified to be somewhat shorter due to the placement of the tap in?





Art,
Thoughts on the previous conversation? Care to share what you are thinking? You usually tell it the way that you see it. BTW I saw your posts at another forum on a related subject but did not comment. I believe they were closed.
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Old 1st June 2011, 09:15 PM   #30
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Art here is some comparison via simulation of the DTS10 versus this horn. This isn't exactly an apples apples deal. The Gjallerhorn is 16% larger, has a higher 17hz versus 14hz loading, has 18% more cone area and 2.3X the total driver displacement and is in all likelihood heavier as well. Also this is just simulation, real world results will be a little or maybe even a lot different especially at high power.



Output at 1m with drive voltage corresponding to 1w into the minimum impedance in the passband
Click the image to open in full size.

Excursion at above drive level. Black is DTS10
Click the image to open in full size.





Output at 130v for Gjallerhorn and 39v for DTS10 (drivers parallel)which brings the excursion near to xmech at the highest excursion peak above the corner.

Click the image to open in full size.

Excursion at above drive level.
Click the image to open in full size.
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