posted
Hey guys, just learned some new terms and it's all way over my head. I'm looking to go overboard with my 3db downpoint and trying to design a box for an idq 2 ohm dvc to run with a 3db downpoint at 30 hz. I'm hoping to go sealed as it shouldn't be that large anyways. I'm not too familiar with the terminology, but if anyone could point me in the right direction in my box design that would be great.
Fs 19.5 Hz Qts .319 Vas 7.65cuft (217L)
There's what I know, if you all could walk me through some of this I'd be greatly appreciative.--ward
Posts: 116 | From: New Orleans, LA USA | Registered: Oct 2000
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posted
You're not likely gonna get a sealed box f3 of 30 Hz, it's very rare. Don't worry too much about it, though. With cabin gain you will have flat response to very low frequencies.
Adam
-------------------- Alpine 7897 mp3 player USAmps (2) TU-600 hybrid Tube amplifiers USAmps USA-2000 Image Dynamics (2) CD2COMP Horns Seas (4) Excel 7" midbass Eclipse Ti Pro 18"
posted
Well I'm not sure of the exact way to measure the f3, but I bought a book with several curves for each qts and you figure out your fob and label it and then go from there. Anyways, from my calculations an idq could have a 3db down point of 27.1hz with a 3.04ft^3 sealed box. If someone else could run those specs or whatever or shoot me some formula's I'd be appreciative. Not afraid of doing the math myself, but most of this is real new to me. Thanks for that info though, still looking for more.--ward
Posts: 116 | From: New Orleans, LA USA | Registered: Oct 2000
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Your box f3 will be in the neihbourhood of 45 Hz with that box volume, not 27.
Get yourself a decent box design program such as unibox (free excel spreadsheet) calculations by hand just suck, and one size fits all charts are worthless.
Adam
-------------------- Alpine 7897 mp3 player USAmps (2) TU-600 hybrid Tube amplifiers USAmps USA-2000 Image Dynamics (2) CD2COMP Horns Seas (4) Excel 7" midbass Eclipse Ti Pro 18"
posted
Well that's the kind of stuff I need to hear. Where can I pick up this excel worksheet? I'm glad someone knows what's up. Thanks for the correction, I'm looking to build this thing right. I'm going to email you atomic fusion as you seem the most willing to share your knowledge. Thanks for the replies.--ward
Posts: 116 | From: New Orleans, LA USA | Registered: Oct 2000
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posted
Well, I'm rather have a smooth response, but I'll have to check out what the curve looks like again. I like my bass tight and low, not necessarily loud, but tight and low.
I'm pretty sure the F3 on the last driver I was running in a sealed 2.5ft^3 box was around 100hz, so anything would be a dramatic improvement. Anyways, I'm looking for a low F3. Maybe 40 is a more realistic goal, I just figured I might not ever get around to building another box just for an F3 of 30 so why not now. But in any event I think I'm going to need more help than I bargained for. Any help would be greatly appreciated.
For now my major problem is determining whether the box program I use accounts for the volume the port takes up and the speaker displacement. That would be nice to know before I do all this number crunching to find out how much my bracing is going to take up. I still haven't decided on my bracing technique, but that's not essential right now. I'm going to download boxplot if I can find it and I'll see what I can do from there, but Shadow Star if you want to shoot some info my way that would be greatly appreciated. I've already contacted Atomic Fusion and he's already been most helpful. I think between the three of us we ought to be able to make one kick ass box. But if you all have some sites that might help or anything like that I'm all ears. I love to learn and understand why I'm doing what I'm doing with my box construction. Thanks in advance for all the help.--ward
Posts: 116 | From: New Orleans, LA USA | Registered: Oct 2000
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posted
Ward, did you try that little program I sent you? It's simple but works surprisingly well. I can also send you unibox if you wish, it gets rather complicated, though.
Sealed boxes tend to couple better with the transfer function of most vehicles. Ported boxes (as shadowstar mentioned and I mentioned in my e-mail)Will have that rise in response because their output is the same while cabin gain continues to amplify the sounds the lower the frequency is, until you reach the box f3. A sealed box with an f3 in the range of 40-50 Hz will merge with your car's transfer function (most cases) to create a relativly flat response down to 20 Hz or even below that. Like I said, I'm no sealed box fan, but if you are dedicated to having flat response, sealed would be a better choice.
Adam
-------------------- Alpine 7897 mp3 player USAmps (2) TU-600 hybrid Tube amplifiers USAmps USA-2000 Image Dynamics (2) CD2COMP Horns Seas (4) Excel 7" midbass Eclipse Ti Pro 18"
posted
Well a sealed box with a higher F3 that still could manage some nice output at 20 hz with a nice response seems more up my alley. If anyone wants to shoot me some internal volume specs, preferably with the driver displacement included, because I really don't know how to account for that, I can do the rest. I may just save the other box for another day when i understand a decent box program that's out there. Thanks in advance for anything you all can do. I can't wait to get this thing started!!--ward
Posts: 116 | From: New Orleans, LA USA | Registered: Oct 2000
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