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Modded X15 |
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alovan 
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Joined: 27 February 2013 Status: Offline Points: 7 |
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 Topic: Modded X15Posted: 15 May 2013 at 3:45pm |
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Hi!
I'm new here and I'm planning to build 2 mid-tops. They would be modded X15, since my budget is close to nothing. I want to use Pa 15BM300B mids and D450 tops. The planning was going very well when a problem appeared. Since the X15 has a trapezoid shape, the port's sides aren't parallel to each other. Becuse of that the cross-sectional area is different at the start and end of the port. How should I calculate with the port's cross-sectional area (average, start, end)?
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DMorison
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Joined: 14 March 2007 Location: Aberdeen Status: Offline Points: 1649 |
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Posted: 18 May 2013 at 10:10am |
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Average, AFAIK.
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AM55
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Joined: 16 August 2007 Location: Matlock Status: Offline Points: 1728 |
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Posted: 18 May 2013 at 10:23am |
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Draw it out to scale then measure it. I would use a cad program as it is easiest for me but a scale drawing on paper (newspaper?) is just as good.
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Baron Greenback
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Joined: 08 March 2011 Location: Shropshire UK Status: Offline Points: 456 |
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Posted: 22 May 2013 at 7:55am |
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Hi, just a thought... If you have the driver, have the Small parameters and have a copy of windows on a PC, why dont you get a copy of bass box pro (BBP), and model yourself a reflex cabinet. I did it with excellent results and no previous experience of enclosure design! It really was not too hard, took some thinking about and some basic maths, but nothing too challenging, give it a go matey, design your own box for your speakers needs. To model the actual cab I used sketchup and still do, it is really easy to use and best of all... it is free!
Edited by Baron Greenback - 22 May 2013 at 7:56am |
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The doctor recons I'm paranoid... well he didn't say it exactly, but I just knew the bastard was thinking it!
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ceharden
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Posted: 22 May 2013 at 12:55pm |
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The port is also against 3 sides of the cab so the actual tuning will not come out the same as the simulation.
To be honest, the safest thing is to leave it the same as the original X15. If you end up running with subs underneath it's a lot less critical anyway. Incidentally the X15 is a particularly large cab for a mid-top, you can probably make it quite a bit more compact. |
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Baron Greenback
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Posted: 22 May 2013 at 11:01pm |
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I used the size of the baffle to dictate the face area of the cab (HxW) allowing about 5mm between the horn (Faital Pro LTH 103) and driver (PDN.15BR40) and 3mm clearance around the horn and driver for grille baton clearance which was at a width of 18mm. I found that I had enough room either side of the horn for the vents and as such have a very compact 15" and later made a 12" cab using the same horn and a PDN.12MH25, if you want the sketchup plans I will be happy to send them your way. PS. The 12" cab in my opinion is a better cab for mid tops, 15" cabs are more of a full range jobbie and it shows, we use ours for monitor use these days as they just do not cut the mustard next to the 12's for HiFi sound. What sort of subs are you running?
Edited by Baron Greenback - 22 May 2013 at 11:04pm |
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The doctor recons I'm paranoid... well he didn't say it exactly, but I just knew the bastard was thinking it!
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ceharden
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Posted: 22 May 2013 at 11:22pm |
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+1 on 12" mid-tops, especially with 1" compression drivers.
15"+1" tends to leave a hole in the middle, you really need a 1.4" or 2" compression driver to make them meet nicely. |
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Baron Greenback
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Posted: 23 May 2013 at 6:21am |
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I would definitely agree, despite our comps being BMS 4550's being capable of 800Hz especially with the long horn (it is possible for a 1" and 15" driver to marry up reasonably well), it does take a lot more messing with the EQ to get it sounding good. In my experience this is not very ideal hence the recommendation for a 12" driver. Also 12's are cheaper so you will be able to get a better drive unit for your money and they are obviously more compact and lighter
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Edited by Baron Greenback - 23 May 2013 at 6:22am |
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The doctor recons I'm paranoid... well he didn't say it exactly, but I just knew the bastard was thinking it!
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alovan
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Posted: 23 May 2013 at 9:37am |
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Thank you guys for your help! I think I've done a mistake with the topic's title. To come clean, it's a really similar cab to x15... I designed it on my own, just used the x15 as a start point. Designed with Google SketchUp, Wind ISD, Hornresp and BBP.
I'll try to explain it. I've got problems with the port's design only. There are 2 options: a - circular ports, b - rctangular ports. I want to use trapezoidal ports (like x15), but I don't know how to calculate it becuse of the rectangular shape of the box and the base panel (the base of the ports also) of the box --> the effective length is longer, the areas are different at the start of the port and the end of the port. DMorison said, I should calculate with the avrg cross-sectional area. Any other opinion? So, drivers... I'll use 1.4" comp or 12" + 1" as you said. Space does not matter (only 1 crtitera - 1ply sheet/cab). Edited by alovan - 23 May 2013 at 1:02pm |
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alovan
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Posted: 23 May 2013 at 12:41pm |
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I've just missed Baron Greenback's post. For me it's a serious point to get out the deepest end from the box since I have a self designed W-bin for bass (actually it has a wide range of frequency response but with it's 40w rms and a maximum output of ~105dB.... WEAK).
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DMorison
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Posted: 23 May 2013 at 1:01pm |
That should give you a decent starting point, you may still need to build a prototype and check it before you get 100% what you want. One other thing to remember is that this kind of port will behave as if it's longer than the apparent length of the shelf (130mm in the case of the original X15). This is because 3 out of the 4 sides of the vent continue unobstructed past this point, so some of the air in the port is induced to keep moving more than it would of the end of the port were in free air. A rough rule of thumb is to assume it'll be 1/2 of the port height longer than the end of the shelf (ie an extra 30mm for X15), which in turn means that it will be narrower still by that point, so remember to factor that in when calculating the average width as well. HTH, David.
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alovan
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Posted: 23 May 2013 at 1:19pm |
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Thanks David! That's what I was looking for. This rule also true if I'm calculating the port's inner segment (the end which is inside the box)?
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alovan wrote: