My diy Subwoofer – I didn’t see (hear) anything worse

[vytas]

This is my first subwoofer and it is very unsuccessful! It’s no wonder because I did it without any rules or calculations, and the results are very sad. Can you tell me what to do my case? Is it possible to reform the situation or should I forget this box?
Some facts:
The driver is very good! I heard it in right box, sounds impressive (not audiophile is more industrial ).
The box is sealed.
I’m sure that I hear sub harmonics described in page http://www.arcavia.com/kyle/Equation...26SubHarm.html
Or it can be standing waves.
So is it possible to make it sound better?
Is it possible to avoid standing waves and subharmonics?

[richie00boy]

Telling us something about the construction of the box and implementation would be useful...

There will not be any standing waves unless your box is has extremely strange dimensions, or your low-pass filter is rubbish. Harmonics indicate a very nasty drive unit or driving the unit into over-excursion or with an underpowered amplifier.

I would say that as it's a sealed box there is nothing much you can do that will change sound substantially, so time for a new design. If you put up the Thiele-Small parameters of the driver then people can help you.

[vytas]

Thank you, richie00boy, for your advices. I forgot the picture of my subwoofer. Some parameters of box: internal volume v=142.2 litres or 5.02 kub. Ft3; with foam rubber inside.

Driver’s parameters: Power handling: 600 watts RMS; voice coil diameter: 4"; nominal impedance: 8 ohms; frequency range: 45-1,200 Hz; magnet assembly weight: 15 lbs. Fs=52 Hz; SPL: 92 dB 1W/1m; Vas= 2.2 Ft3; Qms= 4.5; Qes= 0.34; Qts= 0.32; Xmax= 7.5 mm; dimensions - overall diameter = 12-1/4", cutout diameter: 11", mounting depth= 5". Effective moving mass 65 grammes. That’s all I found.

I don’t use any filters inside, I just connect an amp throughout the low pass crossover and the sound is not musical at all… it’s like bellow or bump I don’t know even how to describe it… By my opinion it is low subharmonics. One more moment, if I will make this box vented, is it possible to improve the sound?
I would like to ask some more questions:
Can you tell me is it mater what kind of shape is box, or the main thing is to hold the volume of subwoofer? (I mean right calculated volume, not my case )?
And how much percentage deflection in volume is tolerated?
Is it true, that I can compensate the volume with special foam?

[richie00boy]

OK those details make things a lot clearer. I can tell you straightaway that is never going to be much of a subwoofer as Fs is far too high.

As it is at the moment, your box is far, far too big. The good news is that you can add a vent to that box and it will improve matters, but it's still far too big. Half that size would be in the right ballpark although still a little on the large size.

I think the bad sound you are getting at the moment is because you are expecting bass out of a poor woofer, and the box is far too big so you're overdriving it at some frequencies. I also suspect your low-pass filter is too shallow slope.

Box shape is of little importance for subwoofers, but at the moment yours is so big it might have a small influence.

Depending on the density of the foam rubber you have used, it may be good or bad to have inside.

My personal opinion is that you should write the project off as a learning experience and start again with a more suitable drive unit. I appreciate that this might be difficult for you in your country or with how much money you have, but you will only ever have a mediocre result if you continue with what you have. Trust me, I have been there and learnt already.

[phase_accurate]

I wouldn't call this one a poor woofer but a poor subwoofer. If you want to use this one for a speaker that goes loud but only down to 60 Hz then Bob's your uncle.

Regards

Charles

[Notax]

Khm....
You did it all wrong.
Make bass-reflex box, parameters:

Vb=55 L (1.94 cu.ft) (netto volume)
Fb=52-54 Hz (53 Hz) (tuning frequency of bass-reflex tunnel)
Dt=140 mm (diameter of BR tube)
Lt=180 mm (BR tube lenght)

Good luck.

[mashaffer]

At first blush it looks like it might do very nicely as a TL or horn sub.

mike

[Cloth Ears]

Hey, the box might not be a throw-away article. There's plenty of subs out theere looking for about 140-150 litre sealed boxes, so getting a new driver might be an option as well (depending on your budget, of course).

There's a couple of woofers at Zalytron that would fit the bill at under $100US (Vas over 200l) - but I'm not sure what you've got available locally.

[richie00boy]

Yes get a new driver and try and use the existing box, with an added vent.

[richie00boy]

Originally posted by mashaffer
At first blush it looks like it might do very nicely as a TL or horn sub.

mike

I have to disagree, with Fs as high as it is, it will never produce anything other than not-really-very-deep bass.

For all the time and effort and materials expended building a TL or horn, it will get slaughtered by a simpler, smaller vented box with a better drive unit.