My Box Design Specs

My first homebuilt box, so I am looking for feedback. 

I have two 12" kicker comps to use and I will be running them paralleled with an alpine V12 bridged.  300 RMS 600 peak.  While I know this is a little underpowered, its all I have at the moment, so i have to make due at the moment.  This box will go in a 99' Tahoe with plenty of cabin room, hopefully this will help.   I listen to alot of everything but mostly probably hip hop.   I am also looking to impress some friends so leaning a little to the punchy or bass side of the quality spectrum.  But again, without the experience of boxbuilding or what it would sound like, I am definately open for suggestions.

This is the ported box I am proposing:

Driver Properties

• Name:
• Type: Standard one-way driver
• No. of Drivers = 2
• Mounting = Standard
• Wiring = Parallel
• Fs = 29.8 Hz
• Qms = 9.865
• Vas = 4.51 cu.ft
• Xmax = 9.76 in
• Sd = 82.31 sq.in
• Qes = 0.629
• Re = 6.89 ohms
• Le = 4.32 mH
• Z = 8 ohms
• Pe = 300 watts

Box Properties

• Name:
• Type: Vented Box
• Shape: Prism, square (optimum)
• Vb = 6.058 cu.ft
• Fb = 37.43 Hz
• QL = 5.952
• F3 = 34.46 Hz
• Fill = none
• No. of Vents = 1
• Vent shape = rectangle
• Vent ends = one flush
• Hv = 4 in
• Wv = 20 in
• Lv = 20.72 in

Thanks to whomever fixed my earlier posts!!!

Here is the data file for Bassbox 6.

https://www.spheresedge.com/images/Bassbox/sweet.bb6

Thanks again for any input. Just to reiterate, my main question is:

Take the extra SPL of this design even though it is a peak or change it to a more rounded design thus lowering my F3 but loosing the SPL.

Cypsteel

For you WINISD users:

WinISD shows the vent length a little shorter but the graph looks very similar.

Driver            : Kicker12/8
Project by        : Cypsteel
Project for       : you
--
Number of drivers : 2
Box type          : Vented
Box size          : 171.5 l
Tuning frequency  : 37.43 Hz
Vent              : 1 vent(s)
                    0.409 m length for each
                    0.102 x 0.508 m rectangle
                                                           
                                                           
             Relative                                      
Freq         Gain         SPL                              
[Hz]         [dB]         [dB]                             
20.00        -16.54       74.88                            
25.00        -10.36       81.05                            
30.00        -6.05        85.36                            
35.00        -2.60        88.81                            
40.00        0.31         91.72                            
45.00        2.63         94.04                            
50.00        4.11         95.52                            
55.00        4.72         96.13                            
60.00        4.71         96.12                            
65.00        4.39         95.80                            
70.00        3.97         95.38                            
75.00        3.54         94.96                            
80.00        3.16         94.57                            
85.00        2.82         94.23                            
90.00        2.53         93.94                            
95.00        2.27         93.68                            
100.00       2.05         93.46                            

Here is the datafile for WINisd:

https://www.spheresedge.com/images/Bassbox/sweet.wid

A couple things:

You need to provide the model of the Comp subs you are using.

I would never want a 5 db peak in the response in anything but pure SPL mode. 

Just for general FYI, you can allow a little more port noise than shown here and thereby make the port structure smaller in opening and length.

The Fs and Re you have shown looks suspect, so when you provide the model info this stuff can be checked out.

Thanks for your input stevdart.  I have read many of your posts on here, especially your guide on WinISD.  Its nice to be around knowledgable audio enthusists.

Here is the model of my drivers:         Kicker 05C128 12" Comp Series Subwoofer, 8-Ohm

As for the 5db peak, thats what I am struggling with.  Hence why I am coming to you guys.  My inexperience denies me the history of listening to differant boxes with differant frequency curves, so I am not sure what exactly I am looking for.    I have owned several prefab bandpasses in the past and it was very impressive to my friends because they hit so hard, I figured that was due to a gain like this peak.  My interpretation is this peak will provide a very hard hitting box, if I am mistaken, please set me straight.

As for the port noise, I will lower those vent parameters while keeping it tuned to 37.43.

Thanks again for your help.  I am hoping to build a box by this weekend if possible :)

CypSteel

Another thing about the 5db peak is I was hoping it would help me with my underpowered amp.  Its a Alpine V12 bridged to 300watts/700w peak.   Those kicker drivers are 300 a piece.  So I feel I am underdriving them a little bit.  Again, I could be wrong here too

Some things look wrong with the specs you listed, so I can't tell anything by the graphs your program has generated.  Is THIS your sub?  8 ohm model, two of them?  (9.76 inch Xmax, for example, should be millimeters.  Fs doesn't correspond but this website isn't showing parameters of the 8 ohm model.)  Check the modeling very carefully before you build.

As for peaking at 5 db to gain more power from the amp:  there will be less power going to the lower sub freqs because of the extra amount of power at the peaked level.  With such a peak in the response, the F3 point literally becomes F8 instead (8 db down from the peaked, or loudest, level.  This makes 'F3' a useless point.  The power is what it is and can't be further amplified by skewing the response curve...it's just spread out a little differently.  And it's fine to supply 150 watts to this sub;  you don't have to meet the RMS rating.

The response as you've shown does resemble more of a bandpass response than a good vented curve.  That is not desirable, IMO.

and note:  it's better to adjust the graphs so that only the most useful range of parameters (db in particular) are displayed.  You need to look at only 6 db above and below the 0 line to see a clearer picture of the output.

9.76 in Xmax...Good stuff 

I will recalculate that :P  Yes that link is to my subs...if you go to kicker.com and click support they have the 8ohm and 4ohm spec's seprated. I would link it but it is all flash so I can't find an anchor point.   You will find the 29.8 fs there for the 12" 8ohm comp driver.

I corrected the Xmax but it doesn't show any differance in my frequency graph. 

I am working on some other possibilities...how important is the knee to be rounded?

Would the purple here be acceptable?  How sharp of a curve is desired at the top of the knee?  Very sharp like the red and pink or gradual like the purple?

Don't worry about the shape of the bend as much as low end freq response and work at lowering the peak level.  And as I look at the specs in the section you described on the Kicker site...it says this is a DVC 8 ohm driver.  Is this right?  So you have two DVC 8 ohm subs wired together parallel/parallel and bridged to a two channel amp?  2 ohm load bridged, so 1 ohm stable, this amp?  What is the model number?

Or are you running an 8 ohm bridged load?  I'm not getting all the info needed here.

edit to add:  the blue (or deep purple) response is the best here.  Peak is slightly under +3 db and F3 is shown at 23 Hz.  Peaking at under +2 db is more desirable but you may not get there...I don't know yet.

Its an older amp.  Alpine V12 MRV-T501.   Again I am not an expert here, but I thought if I paralleled the two 8ohm speakers together it would run at 4 ohms.  Are you saying that because I am running the amp in bridged mode it drops it by another 2?

To bridge my amp, there is a switch along with connecting the speaker wire to the outside positive of left channel to the outside of the right channel.

Oh I realized what you meant by DVC :)

No they are SVC :)

Go to kicker.com and click support, then technical support, then T/S parameters.

They are the 8 ohm listed under comp.

Thanks again for all your help Stevdart.

Yes, if they are single 8 ohm subs they will work well with that amp.

There are too many discrepencies in the published info to model this sub successfully.  Actual use and trial-and-error would likely work out best.  The discrepencies lie in the fact that those T/S parameters as listed don't compute in a true T/S calculation.  For instance, this sub can't have Fs, Bl, Mms and Vas as shown and still compute.  The website clearly shows 'DVC' on the pull-down tab but the manual indicates single voice coil.  I suspect some other misprints here and there.  So, with everything I've seen...

...I would say that you would most likely get the results you want in a large sealed box.  Use the guidelines shown in the sub's manual for maximum SQ, which is still a high Q (higher than true SQ) as shown below.  The manual indicates that all of the larger sealed and vented enclosures allow for 150 watts per sub, so your amplification looks good for two of these.  The graph below shows a huge box at 7 cu ft, which is what Kicker recommends the maximum size to be to attain a reasonably SQ response.  Smaller sizes send the peak up and up and raise the F3.  You should use whatever will fit into your car, keeping BIG as much as possible.

Cheers and good luck with your results.

kicker_05c128.jpg

Would I be better just sending these back and getting an all in one enclosure with the speakers already?  This is getting a little more complicated than I thought it would be and I haven't even started building the box yet

Those response curves looks like crap to me, unless you plan to go into SPL comp and your vehicle resonance frequency is around 90Hz.  But I suppose if you were going into comps you probably wouldn't be asking about your low-power amplifier... Listen to Steve's advice about how to model those speakers.

cypsteel wrote:

---

This is getting a little more complicated than I thought it would be and I haven't even started building the box yet

---

Yes, building a proper enclosure for loudspeakers can get quite complicated and a properly designed bandpass is one of the most difficult of all.  In fact if you are an inexperienced builder I'd say do not attempt a bandpass enclosure under any circumstances, and especially not one for dual drivers.  Also, you are not likely to ever get really excellent response from those low-end Kicker speakers, they just are not very good IMO, so you may be modelling the best they can do.

My only experiences with boxes where prefab bandpasses with the speakers already installed.  We thought they sounded great because they hit so hard and got some of the lower frequencies.   A couple of my friends attempted building sealed and ported boxes but they could really never match up.  With that being said, I ordered two Kicker 12" comps (8ohm).   I have had hell trying to design a medium spl / SQ box as shown in this thread:

https://www.the12volt.com/installbay/forum_posts.asp?tid=80541&PN=2

I need some opinions where I should go from here, I am dying for my low end now that I got my front stage working!

• A.  Send the Kicker's back and buy a comparable replacement.  What would yall suggest?
• B.  Send them back and buy a prefab bandpass or sealed box:   https://www.maaudio.com/productcatalog.cfm?class=47495
• C.  Build a box with the kickers even though I can't find a good SQ line that fits my type of music (hip/hop / rock).
• D.   Send the 12's back and buy some 10's to put in my old bandpass box.

Thanks in advance for any suggestions,

Justin Pedersen