two 8"s in a box...

[chris661]

Hi all

I'm (in the process of) making a subwoofer using two of these 8" drivers.

I decided to set up a new thread here because of the actual specs of these drivers... and the price (£16)

T/S parameters are...

Fs - 33Hz
Qts - 0.3528
Qes - 0.3964
Qms - 3.21
Vas - 56.8L
Sd - 0.0216
Re - 11.6
Vd - 64.93cm^3
Xmax - 3mm
Le - 0.59mH
8 ohm/coil
60W rms/coil
100W rms peak, with no damage
88.94 dB/W/m

I put these into winISD before buying the driver, got some very nice results...

Link to buy some is...

http://cpc.farnell.com/LS00415/audio...randed-55-1455

See what you think

Will post more on the sub I'm making later on...

[planet10]

I thot the part number looked familiar... this is probably the same woofer but local to the USA
http://mcmelectronics.com/product/55-1455

dave

[chris661]

Yeah - they're the same ones...

I really like them... there's decent low-end frequency response, and the higher end rolls off nicely

I'm planning on using 2 of them is a 42L cube, sealed with Linkwitz, to go to -3dB @28Hz

It says 3mm Xmax, but even after that there is only a little distortion.

I dare say there are better drivers out there, but not for that price.

[Bigun]

If it's of interest, I also used two 8's in a sealed box of about this volume. The results were pretty good - but ultimately SPL will be limited by the volume of air those drivers can move, being 'only' 8" and with limited x-max.


Altair Sub (2x TRIO8's)

[AndrewT]

Originally posted by chris661
I'm planning on using 2 of them is a 42L cube, sealed with Linkwitz, to go to -3dB @28Hz

how much LF gain is required to get down to 28Hz?

[chris661]

14.11dB

loses 1db per Hz down after that.

Sounds good in some bigger boxes - had to put bottles of water in to reduce int. volume to 21L/driver.

pics of the spreadsheet attatched.

red line = correction
Green = overall output
Blue = pre-corrected output.

For the driver size, and the simplicity, and the price, the speed and low-end bass guitar bits are damn good.

[chris661]

Interesting to note here - you can achieve v.high mid-bass SPLs using relatively small drivers...

Use harmonics (2nd, 3rd, to around 11th) and your brain fills in the fundamental.

I am fiddling with this concept to get huge SPLs without much Xmax being used...

Not what I'm after, though... may use it as an add-on later.

[AndrewT]

Hi,
do you realise that you are sending 25.7times the power to the pair of 8s compared to a flat signal sent to the remainder of the system. That's what +14.1dB of LF gain does.
Your total bass power handling is 120W.
Divide by 25.7 and that gives the maximum equivalent power you will send to the satellites. I would not be happy with a maximum power of 4.7W into my satellites. That's only +6.7dB of overhead above an average level of 1W. I look for at least +20dB of overhead to reduce the number of transients that get clipped.

My advice, investigate what can be achieved with +10dB of LF gain.

[chris661]

You forget - DVC woofers.

240w rms power handling.

The REALLY low bass on a CD is also typically around 10dB down, meaning there is only 4dBs more power required.

the idea of this project is to go low, not loud, but thanks for the concern.

[richie00boy]

No, you forget. The quoted power handling already takes into account both coils. Also it's a max rating, in reality probably 50-60 RMS.

What you are proposing is about 99% identical to my first major sub-woofer project, a good many years ago now. Build it, but don't think you will get any serious SPL from it. Your theory about the harmonics giving you extra apparent SPL is wrong, it just sounds like a cheap sub being thrashed.