clive

The fold-down centre armrest and tray in the rear seat makes a perfect aperture for a large sub. I think I'll install a 12" high power driver, (one I can get locally that has a huge magnet is the 'Kickass' range). There's plenty of used amps like Nakamichi 200W class D's, with built-in crossover, on the local market. I'll take whatever is the published capacity for the trunk, and use that to design the port. Have to cut at least a 5" aperture in the parcel shelf between the existing Bose units to accomodate the port tube.

machinehead

i think it's best to have the port and the sub on the same plane.

Robert_J

It will give you a very slight increase in SPL but it's not a big deal unless you are competing.

Why don't you just install the sub in an IB alignment? I'm planning on an IB for my '95 Max with either a Soundsplinter RL-p 12" or a Vamp Audio (aka Adire Audio VP-12) 12".

Magnet size is not the best determining factor if a sub is 'kickass'. What sub is it? At least post the T/S parameters.

-Robert

clive

An 'IB alignment'? What's that?
The 'Kickass' is a brand. Costs $60 locally, it is a very heavy unit, dual voicecoil. No parameters available as yet because I have not taken the time to measure it. (Try asking Bose for parameters. They won't say) Unfortunately my daughter just exploded the last Kickass 12", using a 1KW amp with her bass guitar. Until then it was great.

Robert_J

Infinite Baffle or as it was called years ago "free-air". It's basically a large sealed enclosure. Once the size of the enclosure is 10 times the size of the sub's Vas, then the enclosure has no affect on the sub. The size of the enclosure can be as small as 4 times the sub's Vas and have minimal affect on the sub. The larger the enclosure, the closer the Qts of the sub gets to the Qtc of the system. The sound of the sub is not influenced at all by the box.

Never heard of it. Got links to any more information about them?

Do you do your own T/S parameter measurements with something like Woofer Tester 2 or do you send it to get it DUMAXed or Klippled (sp?)?

That's because they don't want anyone to compare them to "real" speakers. Those home systems with the tiny cubes have less than $1 worth of parts but sell for $500. I know $400 of that is for marketing (aka brainwashing).

Can you give some details of the enclosure the sub was in when it exploded?

-Robert

machinehead

It's good for sq as well.

clive

Let's see. First I apologise for posting an incorrect price, the Kickass 12" cost me $60. Thanks for clarifying the IB. I guess the Max trunk would be plenty big enough for an IB, it's just that I like designing ports to give that extra kick at the low-low end.
Details on the Kickass brand driver: Type is BM-W12, the 'maximum power' (obviously not RMS) on the box is 900W. It has a Kapton 2" dual voice coil (2 x 4 ohm) and a Strontium magnet weighing 80 ounces. Sensitivity is given as 91 dB/W/m. It's made in China needless to say...
Parameter measurements: I do them myself using the PC, some software I forget the name of because I don't use it much, and some bits and pieces of testgear.
Regarding the enclosure, it is a labyrinth that I built about 6 months back using one of the design programs. Actually I built it with the intention of having the zero point at 40Hz but I forgot to adjust for end-effect and as a result the 0dB point came out at 35Hz. At 40Hz it is +3 and at 50Hz it is +7 (!) after which it drops back down again. This driver, measured on-axis, wasn't much use above 300Hz.
FYI, the internal labyrinth is the full width of the box and is an average of 59" in overall length as I recall. The cab itself is 19" wide by 15" deep and 36" high. The width was made 19 so as to facilitate a pair of rack mounts on top for the bass amp. When I was testing it with the sweep gen all the furniture started leaping about as it approached 40Hz, and the dog and cat fled the house. I've decided to recut the baffle for a 15" Kickass as a replacement, and I'll buy a new 12" for the car.
Here in Monterrey there is a fabulous selection of speakers, literally many dozens of brands, but you rarely find anything that is recognised in the USA. I did find some Infinity brand 12" speakers for which I have a full set of params, but they were horrible! Had a small magnet and a corrugated paper cone surround.

Robert_J

The Qtc of the sytem should be close to the sub's Qts. Depending on the sub, that could be around .3 which would give you a VERY shallow low frequency roll-off. You should have plenty of low end (again depending on the sub). The only problem is that the sub relies on it's suspension only to control cone motion. You can easily push an average sub to its limits with very little power when its in an IB install.

As for Chinese made subs. The quality could be there. More often they though they are just a POS. I'll hold off judgment on your sub until you can post the T/S parameters. You posted the features of the sub which don't help when we try to model the response in Unibox or WinISD.

And don't get hung up on magnet size. The Sonicraft 12 has a small but extremely powerful magnet.

-Robert

clive

"The only problem is that the sub relies on it's suspension only to control cone motion. You can easily push an average sub to its limits with very little power when its in an IB install."
- Yes, that must be true. I noticed that the drivers in my labyrinth boxes can handle lots more power than in an IB setup without the cone flapping to the point of wrecking the suspension. My first labyrinth design was an experimental 6.5" unit designed with the help of WinISD. I tested it to destruction and over two hours the voice coil became a carbonised chunk, but the suspension was still ok. I assume the loading factor of the labyrinth increases the stiffness of the mechanicals. I also noticed the bass seems 'tighter', better controlled.
I know what you mean about the Chinese speakers. Many are total junk. It's possible to spend as little as $15 on a 12" driver here, but I would never expect anything but garbage for that! Some of the elliptical speakers cost a pile of money, though.