| Re: More HornResponse [message #65259 is a reply to message #65181] |
Sun, 12 December 2010 21:42   |
lunkie
Messages: 14
Registered: January 2010
Location: Michigan
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Yep, I have a front chamber issue, On the smaller horn I built, I also have a 3/4" mounting plate with the 2.5 sq inch cut out. Using real small "seed beads" to measure the B&C 8" cone volume I have a total of over 28 cu inches in the front chamber. The response in horn response is not good, will not not go above 1k with a big bump in the 500 to 800hz region, which is pretty much what I measure in my smaller horn. I can thin out the mounting plate and make it thicker from the under side, but what to do about the 23.5 cu inches that the cone area displaces? A bigger dust cap on the speaker, but I suspect that will play havoc on the parameters. I think it better to use a driver that wants a larger front chamber, but getting to 2k may not be possible. Time for more beer.
Lunk and the Low Notes
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| Re: More HornResponse [message #70110 is a reply to message #65261] |
Sun, 13 November 2011 17:30 |
lunkie
Messages: 14
Registered: January 2010
Location: Michigan
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Chancellor |
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Hi all. It's been nearly a year since my last post on this but don't think I've given up on this. We just got crazy busy at work the past year and I haven't had any spare time to do anything. Work is still busy but surgery has put me on a 4 to 6 week disability so I might find some time to get back to this. I was looking into making a plug of some sort to take up space in the front chamber, as Wayne suggested, and I found some pottery plaster that mixes with water that will pour into the speaker cone (covered with plastic wrap of course) It looks like it will make a good mold that I could push some modeling clay into to make a plug to take up the front chamber volume space. When I can get active/mobile enough I'll give it a try.
Lunk and the Low Notes
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| Re: More HornResponse [message #70259 is a reply to message #70117] |
Tue, 22 November 2011 20:43 |
lunkie
Messages: 14
Registered: January 2010
Location: Michigan
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Chancellor |
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Actually I found out that the pottery plaster drills, cuts and sands pretty easy. So I molded 2 more casts from the speakers. Just waiting for it to completely dry before I put a throat cutout in them.
Lunk and the Low Notes
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| Re: More HornResponse [message #72051 is a reply to message #62155] |
Sat, 07 April 2012 23:05 |
lunkie
Messages: 14
Registered: January 2010
Location: Michigan
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Chancellor |
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Hi all, did get around to making a "volume plugs" but just using the pottery plaster. It dries pretty hard but drills, cuts and sands very easy and made a just about perfect mold of the speaker. So I cut a hole in it to match the throat and glue it to the horn. How well did it work? It definitely helped the high end, but the response had 2 big dips. One centered at 770 hz, about 200hz wide at the top, and the other centered at 1895 hz about 300 hz wide at the top. The depths were about -15 db and -30 db respectively. Not good. I tried putting different things in the throat, varying the rear chamber, plugging the vent in the speaker, nothing would vary the dips more than 3 db. If I added gasket thickness to the speaker on the faceplate (increase the front chamber volume) the dips would slowly push up in frequency and lower in depth, but at the expense of high freq response. So out comes the mold. Now what? I let it rest for a couple weeks and to drink some beer and keep re-reading Wayne's previous posts. I have Wayne's mid horns sitting there, so just for fun I punch in the B & C speaker specs into Wayne's horn and come up with this.
If we look at the 100db level I have 100 hz to 2000 hz response. I'm using a BBE DS26 DSP as a crossover network which has 5 bands of parametric Eq for each of the 3 way band passes I'm using. Maybe I can Eq this out, so I mount the B & C to the horn and test. The response is close but the peak is at 300 to 600 hz and at 2000 hz is about 12-13 db down. So by lowering the higher peaks by 6 db and raising the higher end by 6 db I ended up with a fairly flat response. It sounds pretty good rolling into the DE 250 driver / H290 horn on the top end. I'm pretty happy with it for now and those that have heard it really like the sound. Singers and instruments sound like they are in the room is the most common comment I get. But I think I can make it better, still digesting Wayne's previous posts, but for now I'm just listening.
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Attachment: B & C 8.jpg
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Lunk and the Low Notes
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