Need help tuning

[Ajkub]

I have four Infinity 1262w subs. There will be two in each cabinet in parallel. The cabinets volume is 3.7 ft3. I'm using two 3" ports because I feel they will reproduce tighter sound verses 4" ports. I need some one to plot them for tuning frequency for lowest and tightest responce.
Revc 7.2
Levc 1.1
SD 82.3 ft2/531 M2
Bl 10.8
VAS 2.83 ft3/80.14 L
CMS 199
MMS 203 g
MMD 196 g
FS 25
QMS 6.84
QES .49
QTS .46
HAG .314 in/8 mm
HVC 1.34 in/34 mm
XMax .512 in/13 mm

I know this seems lazy but, all I have for internet is iphone.
Thank you for any help

 

[tb46]

Hi Ajkub,

Assuming that you have a free internal volume of 3.7ft2 [104.77L] go w/ a sealed box for 2ea. Infinity 1262W.

The box is not big enough, and 2ea. 3" ducts do not have sufficient cross-section.

For tightest response go sealed.

Regards,

 

[Ajkub]

Venting buys me around another 3 db. As I'm seeing it, the sensitivity of the woofers is 90 db 1 watt/ 1m. Two subs sharing the inclosure bumps it up to 96 db. I want tuned as low as possible for home theater sound without using a ton of power. So, how low can they go?

 

[revboden]

The T/S specs listed are not usable. Cms could be .199, the Sd is unlikely 82f^2. you may want to have the driver tested to see what the actual T/S specs are.

Without accruate specs you cannot model a proper ported box. I would put two of them in a 2.5cf sealed box and use EQ.

 

[tb46]

Hi Ajkub,

I'll attach a Hornresp simulation for a single 1262W in a 3.7ft^3 vented box @ ~Xmax. The port particle velocity is already too high. Anyway, I recommend you stay w/ sealed for two drivers in this size box.

Regards,

 

[Ajkub]

Eq is out of the question. My ports are firing to the rear, so I'm not worried by port noise. But, if I went with two four inch ports would it be better? Since cabin gain isn't a factor I'd just as soon tune them at 23 Hz or lower. The response plot above doesn't look bad. What was the tuning frequency?

 

[tb46]

Hi,

Here is the tuning for the single 1262W vented enclosure. Hornresp is really easy to use for simple vented alignments, so is WinISD.

Regards,

 

[Inductor]

Eq is out of the question.

I find it strange nobody's mentioning the full design of the speaker, just details. Tuning and size of ports. Obvious the driver is best with sealed but not bad with reflex enclosure but length of tube/ports.
3.7ft³ = 104.8L (each enclosure/2x drivers)
12" INFINITY 1262W, for each driver: 1.85ft³ = 52.4L*
*less the space for ports and drivers

 

[Ajkub]

The cabinets are well built MTX AAL 212 speakers. They are low buck speakers. From the factory they are loud 38 - 22K Hz but, sound horrid. So, for home theater, I bought four subwoofers, two 6.5 fiberglass mid-bass w/ phase plugs and two 8" planar tweeters. Crossover points are 250/ 5000 respectively. I've got around $800 into drivers and DIY crossovers, all purchase at wholesale. This will improve the sound drastically, though not to audiophile standards. But, plenty good for front channel of my home theater system.
My surrounds are all Cambridge Soundworks that get 80 watts RMS each. Front channel right & left get 160 RMS @ 4 ohm. No need for a separate sub with these large floor standing front speakers.
So, I've got plenty headroom for BD play back. I just want to tune these cabinets as low as possible.
Also, I may be looking into finding a used 4 ohm stable integrated 2 X 200+ amp to drive my home brewed floor standing cabinets. But, that's something for another forum.

 

[tb46]

Hi Ajkub,

Can you provide the outside dimensions of the target enclosures, and would you consider adding the duct as a shelf duct below the box?

Regards,

 

[Ajkub]

Outside dimensions are 38" H 15" W 15" D. I'd prefer to keep them rear ported. Sub frequencies from ports will be delayed. But, there is something to be said about corner loading those low frequencies. Right? As it is the only source that will have those frequencies is Dolby digital true HD Sources. The Infinity subs are wired 8 ohm and parallel to a 4 ohm load. Harman Kardon says their sensitivity is 96 dB @ 2.83 v. Which they're rating at 2 ohm. So, with some quick figuring they're more like maybe 90 dB @ 8 ohm 1 watt/ 1m. I guess some people may have fell for that. But still they're really respectable drivers. Better specs than most high end home stereo woofers that cost a lot more.

 

[tb46]

Hi,

I'll take a look at what I can come up w/ from those dimensions.

Regards,

 

[Ajkub]

Thanks Oliver! Just keep in mind that they could be used as PA type speakers and handle over 400 watts RMS. They will usually be driven with under 200 watts RMS. So excursion will be Minimal, so not too worried about port velocity. I can use 4" ports. I'm concerned that I'll loose a lot damping of the woofers.
Does this stuff make sense to you? Or am I wrong? I thinking with 4" ports and a Fs of 25 Hz it will act like a infinite baffle.

 

[tb46]

Hi,

I'll take a look at it, just to be correct on the dimensions, is the attached the speaker you are starting with, and are the quoted dimensions correct? Also, do you have an idea about the wall thickness, e.g.: 3/4" or 5/8" MDF?

Regards,

 

[Ajkub]

Bare box is 3.86 Ft3. Minus .22 Ft3 for midrange enclosure. So 3.64 Ft3 not counting woofers displacement. The SD is 82.3 in2, I think there was a typo on my part.

 

[tb46]

Hi Ajkub,

Got a little behind today, sometimes it feels like work never stops.

I finally decided to look @ dual 3"Dia., dual 4"Dia. and single 6"Dia. ports using the same Hornresp simulation as in Post #5. As tuning points I picked 22, 25 and 27Hz. I'll attach a list of the respective port areas and length. My pick would be the 25Hz tuning w/ the dual 4"Dia. ports (as stated before, my preference would be sealed, or a larger box.). This should work fine. The 3"Dia. 25/27Hz tunings would work w/ straight pipes out the back, for all others you need to bend the pipes (PVC plumbing Ls...). As an alternative you could elevate the box, e.g.: put feet on the bottom corners, and use straight pipes out the bottom (that works fine too).

Add some bracing to the inside of the box if you can, use ample fiberfill stuffing. Seal whatever corners you can get to w/ some silicone, and seal the backs of the midrange and the tweeter.

Regards,

 

[Ajkub]

MTX built them well with epoxy. They're more then sealed. As they are now they have two 2.75" ports tuned at 30 Hz. With the infinity woofers they sound much better than before. Hopefully tuning to 22-25 Hz will give them the tactile seat of your pants feeling that's needed for theater sound. Thank you for all your help. When I'm completely finish I'll send you some pics and maybe video of stuff vibrating across the floor and off the walls. Lol

 

[tb46]

Hi,

I always like to look at build pictures.

One thing I should add is to flare the inputs and outputs of the ports, that will make them more efficient:

Flare-it - Free Speaker Design Software

Regards,

 

[Ajkub]

.375 radius router bit, easy enough. You should see system in my Jeep. All Kappa separates powered my MBquart SQ amps with a Clarion Pro Audio head unit. I win sound quality contest with it. So I guess I'm kinda a audiophile. Lol
Without testing each driver all that fancy software means little in a world of 10+% tolerances. LMAO

 

[Ajkub]

I've decided to add 8" to the bottom of the enclosures. Which changes them by .775 Ft3, making them 4.481 Ft3. I took your shelf idea and expanded on it. Now, should I port to the front or rear? Still thinking of using two 3" ports tuned @ 22 Hz. Your thoughts please