(4) Soundqubed 15's box. Dedicated Home Music System: Build Log - Picture Log - Help Log

[Impalalpine]

Triticum Agricolam

Maybe this will get me less shitty news about the drivers I picked: More T/S parameters on the HDS200-15's

What Soundqubed has on the website:

f(s) 36.34 Hz

Q(ms) 7.483

Q(es) 0.895

Q(ts) 0.800

V(as) 73.310 liters

(2.589 cubic feet)

More detailed:

* Model: HDS215-D4

* Piston Diameter = 330.2 mm
* f(s)= 36.34 Hz
* R(e)= 7.47 Ohms
* Z(max)= 69.87 Ohms
* Q(ms)= 7.483
* Q(es)= 0.895
* Q(ts)= 0.800
* V(as)= 73.310 liters (2.589 cubic feet)
* L(e)= 8.41 mH
* n(0)= 0.37 %
* SPL= 87.84 1W/1m
* M(ms)= 269.40 grams
* C(ms)= 0.07 mm/N
* BL= 22.65

give me some good newsssss (crossing-fingers)

[Triticum Agricolam]

Ok so here is the deal with using the HDC215 in a home audio situation. First off you need to understand that car audio and home audio have a lot in common but there are some important differences. One of the biggest differences is cabin gain, which in cars starts around 60 or so depending on the vehicle. In home audio the room gain may not start until the 20 hz area and depending on the room size and construction you may not get any gain at all.

The other big difference is the content that is played. With car audio it's all music, which has very little content below 30 Hz, in home audio if the speaker is going be used for movies there can be content down to 15 Hz or lower. You said you wanted to tune your speaker low, in the car audio world 28 Hz might be low but in home audio most large subs are tuned anywhere from 14-24 Hz. Now I know you said you will only be using your speakers music so this won't be as much of an issue, but the room gain might still be.

The problem with the HDC215 is it's QTS is too high to give you good low end output in a ported box. In a car this isn't a problem because of cabin gain. But in the home your bass is going to start rolling off at about 50 Hz. Its not going to be the end of the world, but you might not like how it sounds. Here is an example:

The green line is two HDS215's in a 9 cube boxed tuned to 35 hz. The red line is the same but with estimated cabin gain added in. As you the see the red line is what folks want and that's about what you are going to get in a vehicle. Without that cabin gain, which is more like what you will get in your house, you end up with the green line, weak low bass.

Now I'd like to point out that these results are just what you get with this particular driver. There are many car audio drivers that work well in home audio as well, so I'm not trying to generalize, this is just in this particular situation.

Here is an example using Stereo Integrity HT 18" subs.

The green line, again is a pair of HDS215's in a 9 cube box tuned to 35 hz. The red line is a pair of SI HT 18" in a 15 cube box tuned to 20 Hz. The yellow line is a pair of SI HT 18"s in a 36 cube box tuned to 14.5 Hz.

You can see that the SI HT subs in either box are a lot smoother and extend a lot lower than the HDS215's do. For movies the yellow line is the way to go, but since you are just concerned with music the red line would probably suit your needs very well. Also you wouldn't need 4 of the SI HT's, you would be just fine with two of them, which would be less money than four HDS215's. Now this is just one example of a sub that does home audio well and I'm not saying this is how you should do it, but it is something that would work.

In regards to this being a directional application, sound under 80 Hz is pretty non-directional, especially indoors. Other than how the room acoustics will affect it, which is impossible to tell without trying, it won't matter which way you face these subs or where you put them in the room.

Also, if you have never heard of Stereo Integrity before, the owner is the same guy that owns Sundown, they are good stuff.

[Impalalpine]

Triticum Agricolam,

With all this in mind (maybe foolishly) I want to move forward.

I noticed that those graphs were showing a box tuning of 35 hrz. Would a lower tuning such as 25-30 hrz solve any of this rolloff?

​Thank you for putting the time in, I really do appreciate it

[Triticum Agricolam]

Triticum Agricolam,

With all this in mind (maybe foolishly) I want to move forward.

I noticed that those graphs were showing a box tuning of 35 hrz. Would a lower tuning such as 25-30 hrz solve any of this rolloff?

​Thank you for putting the time in, I really do appreciate it

Yes, tuning lower can help somewhat. The only problem with tuning lower is while it gets you a little more on the low end you loose some in the 40-60 Hz range. This can be compensated for by making the box bigger, but you will end up with a pretty big box. Sounds like that might not be a problem for you though.

Also I don't want you to think I'm saying the SoundQubed 15's are a bad choice, I'm not. I'm just saying there may be better choices. If you want to stick with the HDS215s I totally understand and am glad to help you get the most from them.

It looks like you should get a pretty good response with a 31 hz tune and 7.5 cubes of volume per driver. Yup, that's a lot. I'd still recommend using a dual opposed layout and making two boxes each with two drivers. Even if you just stack the two boxes on of each other in the same spot, having two boxes will make them easier to move around without killing yourself and will let you place them in different parts of the room down the road if you so choose.

[Impalalpine]

I would say its safe to say I am sticking with the soundqubed woofer (price is hard to ignore)

I'm on-board with your (2) large box and 31 hrz tuning.

everything sounds great man, looking forward to the build and again thank you so much.

[Triticum Agricolam]

No prob, glad I can help.

I'm working on a potential design for you in Sketchup. You said your max dimentions are 72"x72"x20", which of those is the height, width, & depth?

[Impalalpine]

72in Wide

72in Long

20in Deep

[Triticum Agricolam]

How's this look?

The port is a piece of 10" sonotube and should be 7.5" total length. You can get the sonotube from Home Depot, like this: http://www.homedepot.com/p/SAKRETE-10-in-x-48-in-Concrete-Form-Tube-65470006/100350260

You can move the drivers and port to any sides of the enclosure you want. If possible I'd have the drivers be opposed to each other to cancel out vibration, but that may not work depending on where you are going to have them in your room. The enclosure is probably heavy enough it won't make a huge difference anyway. You will definitely need to brace the enclosure well. Hardwood dowels are good for that.

[OzzieComm]

i'm tuned in to watch this unfold, this sounds (no pun intended) great and look forward the the end result.

[Impalalpine]

It looks great, I have recently messed around with sketchup and can now appreciate the level of work that really goes in these designs so I just have to say thank you at least once more

The sonotube port is a design I havn't seen before, this is like a precision port or aero-port? could you expand on the the idea behind that over a slot port (I figure there is likely a reason this design is superior/more-suited)