[Bombelman]

I ordered one SI HT 18 two weeks ago, now just ordered another, so I can have a matching pair, hehehe...


The sub will need to fit under a shelf, in between brackets, so height is restricted (74cm) and so is width (58cm)

Shelf depth is 60cm, but I could go more if needed...


Currently I have it at 57x73x60cm (WHD) outer dimensions.

I will be using 22mm MDF for this build, double 22mm baffle, slot ported, as you can see...


I used the Precision Port website to calculate port length for round ports, but need some help with this slot port design...


When finished, I will have it sprayed with Speedliner (bedliner used for automotive and industrial purposes)


Questions:

- what frequency do I tune it to ? 20Hz ? Fs17Hz ? Lower ?

- what would be the port length ?

- How do I measure port velocity to avoid chuffing ? Without flares etc...

- also, do I need more volume ? Currently it's about 7cuft sans port.... do I need more ?


Thanks guys !!

 

[Audio Geek]



Check out the threads on LTD02's MartySub variants.

 

Start here: http://www.avsforum.com/t/1516724/martysub-flatpacks

 

[Audio Geek]


What you have is pretty close to the Martycube.

 

[Bombelman]



Quote:
Originally Posted by Audio Geek  /t/1522085/my-first-si-ht-18-build/0_100#post_24469489


What you have is pretty close to the Martycube.

yes, it is *inspired* by it, however I have different width and height to fit my needs. The size and build are quite different. It's just a regular slotted box...

 

[Audio Geek]

Ah, OK. Have you tried playing around with WinISD?

 

[steve nn]

If you want to give me internal after displacement I'll sim it for you if you like. I can do 5.5cf if you have 7cf now before displacement. The larger you can go the better the driver will like it, especially for a 17hz tune. I'm not going to mess with cm though I'm lazy. I will put time into your sim though looking at things. I would need to know how much power also. So I need to know what size your box is in inches.

 

[Bombelman]

I have a free version of winisd but still a n00b in that area...

for power I currently have a Behringer NU3000DSP, bridged it does 4ohm at ~2000W RMS, 3000W max...


If there is a real gain in output, I can "relocate the brackets of the shelves, which will allow me to add more width to the enclosure, if needed ! This would yeald MAYBE 3-4" in overall width ?


Thanks for helping out with modeling, I really do appreciate it !!


edit: internal volume without the slot port: 200liters or 7cu ft, sufficient ?

is there any "differende" between a 17Hz tune and say 20Hz ?

 

[steve nn]

No prob.. you would want to go with 880w. I'll play around with it if you give me the dimensions though. Oh and presuming 3/4 with a 1.5" baff.

 

[Bombelman]

oh, and if it matters, I have 2 of these babes coming,

In 2 channel mode, the Behringer NU3000DSP does 2x 620W RMS at 4 Ohm (2x 820W max).

Sufficient power for 2x SI HT 18 ?

I don't need "screeming loud", I'd rather have chest pounding and gut wrenching lows hehe

 

[steve nn]

Yeah you're only going to need one.

 

[LTD02]

is it more for home theater or for music bass?

 

[Bombelman]

I watch movies and when I do I want good, real good lows.... when I'm not watching movies, I have reaggae music playing, great lows also....

you could say it's a 50/50


I mostly watch action/thriller/sci-fi.....


my current setup is a Dayton Ultimax 15" in 9cu ft.


I want this slot ported box to be at least as good as the Ultimax.

I have some bad experience with a slot ported box, the Polk PSW505, but hey, that was a sub-$200 box ;-)

What a terrible purchase it was, or maybe for the good, as it brought me where I am now, here with you fellow bass-nuts.... hehe

 

[steve nn]



Quote:
Originally Posted by LTD02  /t/1522085/my-first-si-ht-18-build#post_24471265


is it more for home theater or for music bass?

Are you going with this now John>> or something like it?


that is a very good question, i own an NU3000, which i bought figuring it for approximately 1200wrms...since my purchase, with manual in hand, and the unit before me, i still was hard pressed to nail it down....


the tell tail clue ended up being the "350W" marked below the AC Mains connector, ( the manual offered no better specifics, just the same unidentified ratings)...


so i'm going to give you my math and thoughts on it so you can double check my work..


350W @ 115Vac rms, ( line voltage peak is 163V), is 3.043A x 115Vac rms= 350W....


ok...now here's the tricky part...switching power supplies are generally extremely efficient, we'll say 96% here for a ball park...ok...D class power stages are also extremely efficient, as well we'll give that 96% for the sake of moving on...96% of 96%=92.2%=322.7W...


but now... what can you do with a 92.2% efficient amplifier capable of sucking 350Wrms continuous out of the wall socket?


the answer can be found in the term "average music power", ( generally half RMS), so...i'm going to step out on a limb, and call the NU3000 a 322.7x2=645.4Wrms aplifier...


but now let's double check that against peek, like we might a class A/B amp...3000 peak/4=750Wrms....Hmmmm....should we say calling it a 700 watt amplifier is close enough?


or should we consider the supply may have the ability to store quite abit of power between amplifier pulses, and as well may be wired to "read" the output stage....


if we do that, we could possibly call it a very well designed 750Wrms amp...


so...


110Wrms/ channel @ 8ohms 220Wrms/ channel @ 4ohms 375Wrms/ channel @ 2ohms



375Wrms mono bridge @ 8ohms 750Wrms mono bridge @ 4ohms


rulg

 

[steve nn]

Well I went 1,100w regardless what amp you decide in the end. More power is always good as long as your driver/vc can handle it. I’ll leave the amp conversation alone. I just pm’d another member a few days ago trying to get more of a handle on the inuke though. (not the quote above) Having the power on hand for dsp would certainly be nice.


Going with a enclosure 28” tall, 25” wide and 23.5” deep that puts you at 7.9cf minus about 1.5cf displacement presuming a few things. It should put you very close. Your vents come in at 2 X 1.33 X 11.37 at 40.7” long. So that’s a single vent the width of your enclosure with 3/4 brace running down the middle making it two vents counting your 3/4 vent material if indeed it is 3/4”? As far as slot correction goes it’s coming in at 35.17.. Being that you would only have one bend, but is a bit narrow and and close to floor, you might want to go the full correction. With some dsp shaping and power on hand, you can shape your response depending on your room to a degree of course. I put a hp in at 15hz.


EDIT> You also always have the option of three vents 1.33 X 7.33 same length.

 

[Bombelman]

Thanks Steve !

I for my *design* I had used a 5cm (2") high port.

Is this recommended and how long would the port have to be then ?


Can your software calculate port velocities voor either 1.33" and 2" ? Thanks again !!

 

[steve nn]



Quote:
Can your software calculate port velocities voor either 1.33" and 2" ? Thanks again !!

Yes that's a big factor in deciding on your size vent. You're coming in at 21 m/s now. The problem with going 2" on your vent is that it brings your 1st port resonance down and your vent way to long. If you went full correction of 20% you could conceivably come out ok though but put your vent ending right at the top of your enclosure. We could tune it 1hz higher higher though.

 

[splotten]

Steve.


When the Inukes first came out, Behringer disclosed the the rms values in the specifications. They were later removed but someone saved them and posted them online. The values depicted here are very close to what independent testing have found:

 

[Bombelman]



Quote:
Originally Posted by splotten  /t/1522085/my-first-si-ht-18-build/0_100#post_24473721


Steve.


When the Inukes first came out, Behringer disclosed the the rms values in the specifications. They were later removed but someone saved them and posted them online. The values depicted here are very close to what independent testing have found:

Thanks !!!!

 

[steve nn]

Thanks splot! That's really close to what I have had suggested to me or the same without looking. I know he could run more and do the limiters with the 6000 or dual 3000 but I don't want to go there or $uggest myself in case VC's got fried. Anyway 620 v 880 is only a dB although dsp like power of course.

 

[steve nn]

Instead of 1100w but 880w peak (worst scenario air velocity) would put you at 16 m/s if we hit tune with the 3000.