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Discussion Starter #41
Thanks Steve,

I've modelled your recommendations in WinISD and it's starting to make sense to me. However, looking at the port velocity, it seems quite high. Even at my probable normal listening levels (450watts) port velocity is 25. But you say it shouldn't be too much of a problem? My only concern is that one of the subs will be to the rear of the listening position so I don't really want to locate it. Still, if it's only for a few seconds at peak moments as Mike points out, then I guess it's not too much of a problem (I only use the subs for movies by the way).

Also, I presume the port diameter you and WinISD refer to is internal diameter?

What is end correction refering to in WinISD?

One important question - for the ports, do I need flares only at one end, or two?

Also, having 3 ports, would that mean I could block 1 or 2 of then and change the tuning for different SPL/extension - e.g. for movies/music? Not sure if that would be a good thing or not - I just recall some subs having that capability (SVS?).



Cheers,
Sam
 

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Blueeyedfrog said:
I've modelled your recommendations in WinISD and it's starting to make sense to me. However, looking at the port velocity, it seems quite high. Even at my probable normal listening levels (450watts) port velocity is 25. But you say it shouldn't be too much of a problem? My only concern is that one of the subs will be to the rear of the listening position so I don't really want to locate it. Still, if it's only for a few seconds at peak moments as Mike points out, then I guess it's not too much of a problem (I only use the subs for movies by the way).
There is no set limit of port velocity that can be applied to all port diameters, as the air speed at which chuffing or compression begin to take place varies based on diameter and flare radius. The larger the diameter and flaring, the faster the speed at which you can get away with. You'll want to download member Collo's program "Flare It", which can be found on this websit to play around with the numbers. But to give you a heads up, three 4" diameter ports equates to one 6.93" diameter port, which means you can get away with up to 29m/s before any compression takes place. Assuming a 1" flared radius, 24m/s before any chuffing sets in. You should be fine, especially with two subs.

One important question - for the ports, do I need flares only at one end, or two?
I'd go both ends in this case.

Also, having 3 ports, would that mean I could block 1 or 2 of then and change the tuning for different SPL/extension - e.g. for movies/music? Not sure if that would be a good thing or not - I just recall some subs having that capability (SVS?).
I view that more as a circus trick than anything legitimately useful, as you are increasing potential port air flow while reducing effective port area.....makes no sense. Keep all three open.
 

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Discussion Starter #43
Thanks Brent - I'll check that out now.

How much more power - I was looking at an EP2500 at about $585 Aus delivered - seems very cheap compared to anything else here (and about max's out my budget).

Cheers,
Sam/Blue
 

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Discussion Starter #44
I've contacted a couple of Australian CCS suppliers re the SDX15s but they inform me that they are expected later this year - no firm date or price. So, at this stage it looks like the Mach5 IXLs are winning...

So, in the meantime, I've been modelling the IXLs using Collo's sonosub and flare-it software. Flare-it suggests 35mm radius port flares for chuffing-free ports. Wanting to save money and reduce the sub's footprint, I'm considering using 610mm (24") wide sonotube as opposed to 762mm (30") diameter sonotube - I haven't been able to track down any 28" tube in Australia that Steve recommended. Steve also mentioned a minimum of 4" between ports and tube side walls - would that include the flares or just the inner part of the port? Do people think 610mm tube will be wide enough to fit 3, 100mm (+35mm flare radius) ports?

Cheers,
Sam
 

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Discussion Starter #46
Ok, as an update, while designing the subs with the Mach5s IXL18.4s I've also been considering the Tempest-X 15" drivers (design=424.8l, 15hz, 500watts, 8" wide 34.11" long port). They seem model very well (in my novice option) it terms of the transfer magnitude function (possibly better than the IXL 18s - can someone advise?) but appear to produce less SPL than the 18s at sub 20hz frequencies. Could anyone comment? How do these two graphs relate to each other and reflect real world performance?

Nevertheless, after investigating purchasing Tempest in Australia, due to budgetery constraints, I think the Mach5 route has won the day. This is because I intend to purchase one driver, and enough sonotube for two subs, first. Then, once I have built one sub, purchase an amp capable of driving two subs (which will allow later expansion). Finally, depending upon how satisfied I am with one sub, I can purchase the second driver, and build the second sub. I am hoping to find that the one sub will actually blow me away (literally?). Thus, I get one Mach5 18.4 delivered at $336 Aust, compared to $380 for a Tempest-x 15 (I can only get the Tempest drivers cheaper if I purchase 2 at the same time - $679 delivered). The Mach5 wins.

So, I could be ordering a Mach5 driver this week and starting my sonotube mach5 build this weekend unless someone can persude me otherwise... :huh: Comments/suggestions please!

P.S. Thanks Steve for all the design tips (I.e. - thanks for designing my sub!)
 
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