Tuning a 1x12 cab

[nickm57]

Just about to finish my 1x12 ported cab.
(thanks funk), I've got a Jensen Blackbird Jet(the price was too good) to load.
Now can anyone give me some advice into the port tuning?
I've tried a couple of the cab calculators but I'm unsure of the port lengths.
I know that the ports control the bass.
Does anyone know of a good calculator to get into the ball park of the port lengths or is this a matter of trial and error?
thanks Nick

[deiseldave]

I've been very happy with Eminence Designer.

[nickm57]

any suggestions on the roll off frequency
80hz, 60hz ?

[deiseldave]

If you want to give me the Thiele specs on the speaker(s) you plan to use, along with any size restrictions, and a desired freq response, I'll model some cabs for you.
It would also help if you gave me an idea of the type of tone you're looking for also (Hendrix, Metallica, Tiny Tim, etc.)

[nickm57]

hi
I downloaded the eminence demo, it is locked to one style speaker....

I want the cab to have a bit more dispersion and bottom end than a closed back. In the ballpark of a 2x12 , but not hurt my back. Nothing extreme.

My cab is based on HAD 1x12 ported. Looks like it has 2x 100mm ports.
507X405X266mm (external) 19mm pine. 15mm ply baffles 210mm apart(internal).
So I'm after what and how the port sizes diameter and lengths are going to do to the cab.


the speaker is a jensen blackbird 12" 8 ohm
ts specs:
Voice Coil DC Resistance RE 6.30Ω
Resonance Frequency ƒS 95.1Hz
Mechanical Q Factor QMS 11.81
Electrical Q Factor QES 0.90
Total Q Factor QTS 0.84
Mechanical Moving Mass MMS 27.7 g
Mechanical Compliance CMS 102µm/N
Force Factor BxL 10.76 Wb/m
Equivalent Acoustic Volume VAS 34.4 lt.
Maximum Linear Displacement XMAX +/-1.0 mm
Reference Efficiency nO 3.13 %
Diaphragm Area SD 490.8 cm2
Losses Electrical Resistance RES 82.7Ω
Voice Coil Inductance @ 1kHz LE 0.59 mH

thanks nick

[deiseldave]

Hey Nick,

When I get off work, I'll look at those values for you. Hopefully, I can locate my Eminence Designer CD without too much trouble. The one beef I have with that software is that, even though the program installs and works from the hard drive, you actually have to load the CD in order to use it !! So, if you can't find the CD, you're screwed. I've bought it twice now.
Anyway, I'll get back with you tonight.

Dave

[deiseldave]

hi
My cab is based on HAD 1x12 ported. Looks like it has 2x 100mm ports.
507X405X266mm (external) 19mm pine. 15mm ply baffles 210mm apart(internal).
thanks nick

Nick,
I'm home and found my E.D. CD, however, I don't understand the 15mm baffles 210mm apart in a 1X12. It doesn't make sense to me. Please elaborate.

[deiseldave]

Just to give you an idea of tuning port length effects using the 1X12 outside dimensions & ply you gave (no baffle), no acoustic filler, loaded with a Blackbird and (2) 100mm ports:
Port(s) lengths
300mm: F3 = 97.41 Hz, Fb = 62.23 Hz
200mm: F3 = 97.41 Hz, Fb = 69.39 Hz
100mm: F3 = 97.41 Hz, Fb = 81.6 Hz

Time for dinner. I'll wait to get clarification from you, regarding the baffle question.

Dave

[nickm57]

thanks Dave that really helps.
Thought that this place to discuss, as HAD was working with tuned port guitar cabs.

The baffles are the front and back panels. They sit 210mm apart not 266mm
one is inset for the front grill thus decreasing the volume of the box.


266mm
|-----------|-
| 210mm
|
|
|
|-----------|-

looks like a low Fb (300mm) is not possible on this size box, with these size ports.
To me, the cabs I have seen photos of, are tuned to around 80hz.

[deiseldave]

quote="nickm57"]
266mm
|-----------|-
| 210mm
|
|
|
|-----------|-

.[/quote]

I understand. I wasn't sure if you had confused a 2X12 with a 1X12. Anyway, the port lengths that I gave you will be a bit off, because I forgot to load the speakers displacement.
I have all that loaded now, so we can play a bit.
While I was waiting on your clarification, I kicked around the 2X12 design I would probably build with that driver.
I basically let the software pick the optimum high output golden ratio design for the driver, and then keeping the volume, and tuning pretty much the same, tweaked the layout so everything fits, and the design works. Then I round off to easy to work with measurements.
Note: I did the cab in inches, and then had the software transpose to millimeters, so you may need to round a bit yourself.
I don't have a scanner, so I screen printed into Word. See attached.
I'll do up your HAD 1X12 now.

[deiseldave]

Sorry, I forgot to include the box and port parameters for me suggested 2X12. Here they are.

[deiseldave]

Jensen BB -> HAD 1X12 e/w (2) 100mm X 100mm round ports.

[deiseldave]

same Jensen BB HAD112 e/w with 150mm port lengths

[deiseldave]

Nick,
You probably already noticed, but E.D. does not configure insets, overhangs, etc. Or, I just don't know how to. So I did your box dimensions as 405mm X 507mm X 210.
So you will have to add your desired overhang to the top bottom and sides, cut out dimensions.
Dave

[deiseldave]

Funny, I've been abbreviating Eminence Designer as E.D., wondering "where have I heard that acronym before ?". Then it came to me... Erectile Dysfunction.
Kind of ironic, because cabinet modeling is what gives me a boner.