reflex design questions,,,, again |
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PoteirosCorp
Registered User Joined: 31 August 2004 Status: Offline Points: 178 |
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Posted: 27 January 2005 at 2:00am |
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hello I know the response must be flatern as possible, but I try to know wich one is the minium aceptable to have a decent bass (dont want this boxes to loud , just a nice extension, cause I be playing till 45hz) |
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mobiele eenheid
Old Croc Joined: 15 August 2004 Location: Netherlands Status: Offline Points: 1568 |
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A 200 ltr box tuned @ 40 hz is pretty much safe design. You'll get a f6 of about 45Hz. And a very nice groupdelay. Usually the sm-115 is used for PA in a slightly larger box with a little higher tuning, more like 240 ltr tuned @ 44 Hz (for a double). This won't change the f6 much, but the f3 will be reasonable lower. Since there is no free lunch, the groupdelay will become slightly more noticeable, tho that doesn't seem to bother most users. Most professional designers will take only the f3 in account, since a 3 dB difference is just slightly hear-able. If manufacturers use the f10 point it's usually to impress the people that don't know what to look for. A 10 dB difference is a very big difference. If the usable frequency limits are given, without stated if it's f3 or f10 you can bet it's the f10 points given. If you're using WinISD Pro 0.44 it might be a good idea to upgrade to WinISD Pro 0.50a6 or 0.50a7. a7 has some improvements over a6 but since it has a bug a6 is much nicer to work with. The Pro versions will leave 0.44 far behind, since they give much more essential information and are still freeware. I've written a small guide that explains the important parts of the newer versions. It's in Dutch but I could translate it and put it on speakerplans as an topic if you'll like, or just e-mail it. Could be ready before the end of the week. Cheers Edited by mobiele eenheid |
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PoteirosCorp
Registered User Joined: 31 August 2004 Status: Offline Points: 178 |
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thanks The dimensions are given to fit my Ford Van (subs and tops with a lot of drums) so what should I do: higger tunning?? bigger box ?? Cheers |
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mobiele eenheid
Old Croc Joined: 15 August 2004 Location: Netherlands Status: Offline Points: 1568 |
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Yes, f3 = the -3dB point, etc. Hmm....Using a double 15" in a van (ehhrr... for inside?? or free party drive-in style; cops show up, close the doors and get the **** out of there ) The problem is that if you want a flat frequency response (performance graphic) you'll have to take the roomgain into account. You''ll have a lot of gain in a car for the lower frequencies. No idea how much exactly, depends on the dimensions of your van. So if you design it to have a straight frequency response (performance graphic) you'll end up with a huge bump in the low frequencies response. In a "normal" volumed car the room gain starts beneath 60-80 Hz. So if the frequency response starts to roll off at that point it's pretty much ok. At 20 Hz it can be as much as 9 dB of gain. But since I don't know enough about the room gain in a car I'm probably not the right person to talk to about the tuning (thought you were talking PA wise). My best bet would be to put it on a car audio forum. Guide coming at ya this weekend. Cheers
Edited by mobiele eenheid |
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Calitri
Registered User Joined: 02 November 2004 Location: Finland Status: Offline Points: 132 |
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You
also have to think about the crossover. The flatness of the responce
curve depends on at what frequency you cross it. Since you're using
WinISD, it has the EQ/Filter settings tab so you can test what would be
the best settings for your cabinet.
I would probably use about the same as you, because I like to have a bit extened responce too. And like mobiele eenheid said 200 litres @ 40 Hz is always a safe design. If you want extend it more and make it a flat responce do it the way Electrovoice used to do it. Put a high pass filter around 35 Hz and parametric EQ also @ 35 Hz about 3-6 dB of boost. That way you can get -3db to about 45-40 Hz and you have protection for your speakers as well and you can get it quite loud also if ever need that. |
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PoteirosCorp
Registered User Joined: 31 August 2004 Status: Offline Points: 178 |
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hahah my english is not so good I'm talking about PA I said to fit my van cause with those dimentions I can put 4 boxes inside, my currently big tops (later I gonna shrink them) and all my drums The Van is a Ford Econoline 86 Calitri, I take your advised and get a parametric EQ By the way, answering my first question... wich f3 will be a nice one ?? I saw some manufacters singles 15" that have f3 50-55hz f10 35hz (the same as my simulation) Cheers and thanks again
P.S. Just have to say "mostly" ?? |
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mobiele eenheid
Old Croc Joined: 15 August 2004 Location: Netherlands Status: Offline Points: 1568 |
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Don't know much about cars (or van's for that matter) can you give the dimensions of the space the cabs have to be fitted in?
There isn't really a limit to what would be a nice f3. It's more about what is possible in this case. The speaker is the first limiting factor, the cabsize the second. In an approximate cabsize of 240 ltr tuned to 45 Hz you will have a f3 of about 48,5 hz at full power. That's what can be done without sacrificing too much powerhandling and/or groupdelay. If the sizes allows that it would be my best bet. Usually the calculated volume times 1,55 will be the total volume (cabmaterial, loudspeaker, loudspeaker safespace, speakerfoam and bracing). So about 380 ltr per cab and weighing about 60 kg (say 135 lbs) if made from Finnish ply. Personally I would favor single driver cabs as they would be lighter, easier moved and perhaps would even fit nicer into your van. I would only think about doubles if I had a two man crew, don't know if you do? I will post the first part of the guide (about the powerdip) in a new topic, in the hope someone could check it for proper English. By posting it down here it would probably only distort this topic. By sending it straight to you it could be too sloppy to read. Cheers Edited by mobiele eenheid |
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PoteirosCorp
Registered User Joined: 31 August 2004 Status: Offline Points: 178 |
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45cmX90cmX55cm = 222 (minus speaker, ports and braces vllume) = 200 that way I can fit 4 (8 at full space with the new small 12" tops I want) I guess my "desing" isn't that bulletproof (hahah just kiding) I'll check if I can go up to 240ltrs   ; and taking consideration of single 15"'s 120liters 45hz give a f3 of 48.99 So, thank you very much
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