What box to build? 2 Mach5 IXL-18 with a Behringer NX6000D

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Hello,

I got a good deal on 2 Mach5 IXL-18 with a Behringer NX6000D amp and I am keen to build my first DIY sub box (I have moderate wood working ability, and live in Canada, so buying flat packs will not be a great option).

But I am wondering what I should build.

For background info:
Use will be 75% music, 25% HT
Room is ~ 16ft x 10ft
The way the room is laid out, one sub will most likely go right behind the main listening position and one directly in front / center.

Priorities for me would be (in order):
#1 Accuracy and musicality, so I was looking into a sealed box. But then I was playing with WinISD and noted that I may not be able to get as deep as I would like without extreme DSP (which I am ok with) but also extreme cone excursion (which I don't want to blow these subs).

#2 Low extension, the lower the better (although this is my first proper sub, so we shall see how addicting that low end really is), so then I was maybe thinking about a large EBS build. Would a full or mini marty be a good fit?

Thankfully space will not be an issue, so really any box size I would make work.
Also, I typically listen below reference, so will not need them to hit crazy high levels.
I just want it clean and then deep.

Super keen for any recommendations.
Also, since this is my first build, if there are any recommended sites for designs (mostly if ported is the way to go) that would be great!

Sub specs if that helps:
Mach5 IXL-18
T/S Parameters
Fs = 17.7 Hz
Re = 3.4 Ohms
Qes = 0.39
Qms = 5.59
Qts = 0.37
Mms = 434.3 grams
Rms = 8.69 kg/s
Cms = 0.184 mm/N
VAS = 274.1 litres
Sd = 1029.2 cm2
Xmax = 22 mm
Cone Diameter = 36.2 cm
Le = 6.09 mH
Bl = 20.51 Tm
Power Handling: 800 Watts SPL (2.83v/1m): 89.2 db
Ported: 200 litres (7 cu.ft.) 19hz tuning
EBS: 365 litres (12.88 cu.ft.) 15hz tuning

Thanks!
 
You have plenty of cone area and displacement, and don't want to get crazy-loud. I'd probably go for sealed boxes and EQ the result. Got any measurement gear?

Chris

Yes I certinaly do have a UMIK-1 and love playing around in REW, so I should be able to find the ideal location and also do some DSP work with it.
Just looking at WinISD it looks like if I play around with DSP to get that low end, that I could be hitting max cone excursion on those lower hz. Is that something I should greatly worry about? Or would that only occur when I was really increasing the SPL and thus not be an issue.

Because of that, I was wondering if I should:

A) Make a Martycube as it is 4.75 c.f., tuning = 20hz and then I could block the ports to effectively get a sealed 4.75cf sub (Which is super close to the recommended sealed size of 5cf by the manufacturer) - which gives a Qtc of 0.65

B) Make The V.B.S.S. as it would fit nicely in my room, be 6.25cf and tuned to 20hz. I just don't know if it would be a good idea to use this design if I am going from ported to plugging the ports as that would give a Qtc of 0.6
Is that enough of a difference of the Qtc (0.65 vs 0.6) that I should avoid this design compared to the Marty cube if I am thinking of occasionally plugging the ports?

Thoughts?
 
Just looking at WinISD it looks like if I play around with DSP to get that low end, that I could be hitting max cone excursion on those lower hz. Is that something I should greatly worry about? Or would that only occur when I was really increasing the SPL and thus not be an issue.

Check the SPL output when you're close to the excursion limits, and see what you think.

The pair of 18"s at Xmax will put out 114dB@1m@20Hz, and that's groundplane. +6dB for against a wall, +more dB when you include room gain.

That would be loud enough for me - I'm happy with a pair of 8"s for home use. YMMV.

Chris
 
Check the SPL output when you're close to the excursion limits, and see what you think.

The pair of 18"s at Xmax will put out 114dB@1m@20Hz, and that's groundplane. +6dB for against a wall, +more dB when you include room gain.

That would be loud enough for me - I'm happy with a pair of 8"s for home use. YMMV.

Chris

Perfect! Yeah I did not see that in WinISD. Ok yeah, the levels I would be hitting would be in the 100db range even with a sealed sub with full eq running prior to hitting max excursion. Thanks!

I think in that case, I will build the Mini Marty as then I can seal the ports and have it act like a sealed sub, but then also get to play around with what a ported enclosure sounds like. Seem reasonable?
How does one decide where to put the High Pass Filter - as it seems it will be very dependent on what levels you are listening to.
 
Hmm, thought I posted this overnight just to get the 'ball rolling' ;) .........

Greets!

Spec wise, a ~universal driver, so all sorts of alignment options with power handling [Xmax], box size the only limiter. The pioneer's Vb = Vas/1.44 tuned to Fs is the best trade-off between size, performance, though requires such a long vent that either dual PRs or an inverse tapered TQWT is required.

A Vb = Vas with the same vent creates a 'small' 15 Hz EBS, which in such a small room will be plenty low once room/boundary gain is factored in.

GM
 
Hmm, thought I posted this overnight just to get the 'ball rolling' ;) .........

Greets!

Spec wise, a ~universal driver, so all sorts of alignment options with power handling [Xmax], box size the only limiter. The pioneer's Vb = Vas/1.44 tuned to Fs is the best trade-off between size, performance, though requires such a long vent that either dual PRs or an inverse tapered TQWT is required.

A Vb = Vas with the same vent creates a 'small' 15 Hz EBS, which in such a small room will be plenty low once room/boundary gain is factored in.

GM

Would this line up with a Marty cube or a VBSS? Just looking for a pre existing sub design.
 
Ok, I was almost starting to suffer analysis paralysis, so my wife ended up making the decision that the VBSS would be better as it would have more placement options in our room and I could also get the to fit on one sheet of MDF each.

Anyways, we are using a port tune to 20hz yet can port plug to 15hz and to a sealed configuration.

Man I am excited to get these things up and running!

Any suggestions for wiring guides for the NX6000D and subs?
Thanks again for all the input!
 
Just finished building these! Man what a difference from two general 6-8" store bought subs!

Super happy with the results!
Thanks for all the advice!

Just wondering for using DSP, it seems like most people look at the combined frequency response of both the subs and then apply one filter to both subs. But would that not effectively double whatever alterations the EQ is calling for (as it will be applied to both subs)? Would it not make more sense to apply individual filters to individual subs to get each sub as flat as possible (with the goal of both then combined being flat)?
 
Just wondering for using DSP, it seems like most people look at the combined frequency response of both the subs and then apply one filter to both subs. But would that not effectively double whatever alterations the EQ is calling for (as it will be applied to both subs)? Would it not make more sense to apply individual filters to individual subs to get each sub as flat as possible (with the goal of both then combined being flat)?

That's fine if they are in the same location or the room is acoustically VERY symmetrical, ditto the subs in relation to it, but so many rooms aren't, so even way back when, I recommended/did tune speaker's vents individually for best overall performance and for vented subs, even more critical.

Speakers acoustically close will combine to double their acoustic power [+3 dB] and single power feed, another doubling [+3 dB], summing to +6 dB. Any EQ added equally to both speakers will just change the summed frequency response.

If done individually, then summing becomes frequency dependent and since each speaker's 'flat' response may not have the same amplitude it won't necessarily double: Adding acoustic levels summing sound levels 10 combining addition summation sum decibel levels or SPL of up to ten incoherent sound sources audio logarithmic decibel scale identical summing 1/3 octave spl full octave sum sound pressure level noise so

GM
 
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