This is a technique that looks good. Not a lot of infrastructure required, so you could try a few profiles out relatively quickly.
doityourselfaudio: 140Hz Petal Horns
He made a re-usable template to fit the mouth to, but I like the idea of making the templates as permanent rings, that act as bracing.
e.g. using this technique for a horn like the Azura 550, you could make a mouth ring that's ~300mm across and affix the petals to that.
doityourselfaudio: 140Hz Petal Horns
He made a re-usable template to fit the mouth to, but I like the idea of making the templates as permanent rings, that act as bracing.
e.g. using this technique for a horn like the Azura 550, you could make a mouth ring that's ~300mm across and affix the petals to that.
Nice work but TBO my horns are designed to absorb higher order modes and those that you make are higher order modes generating devices
It is still a good idea to always be accurate.First off: The intention of my post was to give an example of how your work might have been exploited by JBL Marketeers and not to think in absolutes.
My statements were not intended as academic comments to dispute your research (Waveguide Theory), and definately not specific(ally valid) to all cases, all high frequency drivers, etc.
After all, this is a DIY forum and not a scientific review board
To make anything "work properly ... design considerations have to be taken into account." When is this ever not the case? So your statement really didn't mean anything at all.
All finite sized sources eventually produce spherical waves, its just that a dome is not ideally spherical as is commonly thought. As a contrast, the wave front of a OS waveguide is exactly spherical.
Small waveguides on dome tweeters is not really what I am interested in. For the most part they don't have enough output and power handling - not compared to a compression driver. The thread that you posted confirms that they don't work as well as a compression driver on a waveguide.
The DE250 is a great driver, although I do like the DE500 a little better, except in some cases the higher output of the DE250 at > 10 kHz is necessary. For example a DE500 cannot keep up with a 15" B&C woofer, but it can with a 12" one.
Could you say if the response of my DE250 is normal, please ?
The loudspeaker unit is on the floor (on a cushion
) and the microphone is on axis at 30Cm without any horn.
@silverprout, your measurement illustrates why you want to avoid these things in horns and waveguides:
1) avoid using a horn or waveguide that's too small
2) avoid using a horn or waveguide that's circular
3) avoid using a horn or waveguide that's symmetrical
(Your unterminated compression driver behaves as if it was mounted on a very small round baffle (the face of the compression driver behaves as a baffle) and that's not A Good Thing.)
You can bend the rules a little if you address two of those three things. IE, a round waveguide isn't ideal, but if you make it very large, it's less of a problem. A small waveguide isn't ideal, but if you make it elliptical, it's less of a problem.
And all of these are my opinions of course, based on building and measuring lots o' waveguides.
1) avoid using a horn or waveguide that's too small
2) avoid using a horn or waveguide that's circular
3) avoid using a horn or waveguide that's symmetrical
(Your unterminated compression driver behaves as if it was mounted on a very small round baffle (the face of the compression driver behaves as a baffle) and that's not A Good Thing.)
You can bend the rules a little if you address two of those three things. IE, a round waveguide isn't ideal, but if you make it very large, it's less of a problem. A small waveguide isn't ideal, but if you make it elliptical, it's less of a problem.
And all of these are my opinions of course, based on building and measuring lots o' waveguides.
Same protocol :
Red : Fane FH450 (40x100 radial CD)
Green : Sica Q07015A (80x60)
Blue : JMLC700 (LeCleach)
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I understand why the Le Cleach is really better in this domain (comparatively to the others horns that i've tested)... i should perhaps integrate the horn in a sphere ?
These measurements are terrible. Go outside and do your measurement.
You shouldn't have this much ripple. If you'd set the gate really long, you might, but it looks like your gate is less than five milliseconds. (I don't use REQW, but it appears that your gate is set to 910Hz?)
In a room with eight foot ceilings, you could probably get a decent measurement down to about 2000hz indoors.
Also, with that much ripple, it's possible you have the wrong mic selected. For instance, on my laptop, I get measurements like that when I accidentally select the mic on my laptop instead of my USB mic.
You shouldn't have this much ripple. If you'd set the gate really long, you might, but it looks like your gate is less than five milliseconds. (I don't use REQW, but it appears that your gate is set to 910Hz?)
In a room with eight foot ceilings, you could probably get a decent measurement down to about 2000hz indoors.
Also, with that much ripple, it's possible you have the wrong mic selected. For instance, on my laptop, I get measurements like that when I accidentally select the mic on my laptop instead of my USB mic.
It was my first idea but there is a terrible wind outside and i must probably tidy my room.
I will redo ASAP with ARTA
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Also, post the impulse response, as that should make clear what is going on. But, yes, those results imply something is wrong.
John - those curves from Olsen are not very accurate as it is known that he just hand drew them based on what he thought would happen. They are NOT measurements. And to your three points - aren't # 2 and 3 the same thing?
John - those curves from Olsen are not very accurate as it is known that he just hand drew them based on what he thought would happen. They are NOT measurements. And to your three points - aren't # 2 and 3 the same thing?
Hello,
I've arranged my room for a 2pi measurement, the unit is at the center of the room on the floor with the mouth flaring on a 2m x 1.4m perfectly flat surface, the microphone is at 30cm of the source without any horn
i'm definitely not good at measuring.
ARTA with the standard settings :
REW 500ms
REW 100ms
I've arranged my room for a 2pi measurement, the unit is at the center of the room on the floor with the mouth flaring on a 2m x 1.4m perfectly flat surface, the microphone is at 30cm of the source without any horn
i'm definitely not good at measuring.ARTA with the standard settings :
REW 500ms
REW 100ms
"Five hundred milliseconds?" Is that how long your gate is?
If so, that is the problem. Sound travels one meter in three milliseconds. Due to this, we have to set our gate very short, particularly if you're measuring indoors.
If your ceiling is about 2.5 meters, you should have the loudspeaker elevated above the floor, and the gate should be well under five or six milliseconds.
Basically your measurement is all wavy because 98% of the data that you're recording is reflections.
I'm a fan of ground plane measurements also. They're not perfect, but you can get good results without a tremendous amount of furniture rearrangement.
In Arta, you can see where to set your gate by looking at the impulse response. For instance, if your ceiling is 2.5 meters, the first reflection will be somewhere around 2-3ms after the initial 'spike' of the impulse. You can see the reflection in the trail of the impulse. Set your gate JUST before that first reflection.
If it's still for sale, buy a copy of Joseph D'Appolito's "testing loudspeakers."
Testing Loudspeakers: Joseph D'Appolito: 9781882580170: Amazon.com: Books
If so, that is the problem. Sound travels one meter in three milliseconds. Due to this, we have to set our gate very short, particularly if you're measuring indoors.
If your ceiling is about 2.5 meters, you should have the loudspeaker elevated above the floor, and the gate should be well under five or six milliseconds.
Basically your measurement is all wavy because 98% of the data that you're recording is reflections.
I'm a fan of ground plane measurements also. They're not perfect, but you can get good results without a tremendous amount of furniture rearrangement.
In Arta, you can see where to set your gate by looking at the impulse response. For instance, if your ceiling is 2.5 meters, the first reflection will be somewhere around 2-3ms after the initial 'spike' of the impulse. You can see the reflection in the trail of the impulse. Set your gate JUST before that first reflection.
If it's still for sale, buy a copy of Joseph D'Appolito's "testing loudspeakers."
Testing Loudspeakers: Joseph D'Appolito: 9781882580170: Amazon.com: Books
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Thanks a lot
I've gated it, 3ms.
Red : 2pi naked
green : tractrix 500Hz
I'm not sure if a good reading can save me
The lack of loading of a WG should be precisely equalized, it is not really an amateur work IMHO.
Do you think that this is one of the most important reason of the DIY fails ?
There are a lot of basic guys (like me), that can't motivate themselves to learn if they don't experiment at all. The DIY is more a learning process than anything else.
What would you say about the SEOS WG ?... they are not specifically designed to operate correctly with all Compression drivers, they seems to be a very aleatory choice ?