In Reply to: RE: rough front horn (semi fullrange) posted by SpeakerScott on November 13, 2014 at 12:38:35:
Thanks for the info.I measure with white or pink noise. I capture with Audiotool + Dayton Audio iMM-6 + phone, load the file to my PC and graph it in a spreadsheet.
In the graph I originally posted, it is a standard log scale, but the numbering is set by where I decide to chop the axis off. So, each minor gridline from 2kHz to 20kHz was a 2kHz increment. The notch is deepest at 7.2kHz.
1. This got me thinking in good directions. 7.2kHz = wavelength 47mm, which is a match for the driver radius. It may have been from a leak: adding a gasket has improved it. The throat interface, by the way, is rough and basic :)
2. Nope, just noise, so the window is totally open. The low end will be lumpy from room effects, the high end will have reflection artefacts from the mic apparatus, phone, and my hands.
I could improve the HF part by mounting the mic in a foam block and/or adding a lead to separate the mic.
3. I've heard good things about REW. I'm also tempted to get the Dayton Audio OmniMic V2 system: it seems like a more costly but easier way to improve my measurement capability.
The attached image (with the axis numbered more conventionally) shows where I'm at: added a gasket, filled in horn corners (now it has an octagonal rather than square throat), dragged an old pair of 12" boxes out, am running them in parallel for extra sensitivity. The horn is about as flat as I could hope for at this stage, but is still about 3dB hotter than the bass. This is much more efficiency than I was expecting: looks like it wants a pair of 15" direct radiators (or equivalent), separate amplification, or padding of some sort.
I purchased four of these 4" drivers (and four 3") so that I can sacrifice one or two with non reversible treatments. It looks like I can aim to add resonance-eating cone treatments which cost a dB or three, and this would make it easier to integrate with a reasonably sized bass system.
Edits: 11/13/14
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Follow Ups
- RE: rough front horn (semi fullrange) - hollowboy 16:42:48 11/13/14 (3)
- RE: rough front horn (semi fullrange) - SpeakerScott 16:57:51 11/13/14 (2)
- RE: rough front horn (semi fullrange) - hollowboy 03:08:31 11/19/14 (1)
- RE: rough front horn (semi fullrange) - Joseph Crowe 04:35:56 11/19/14 (0)