Better low end response from sealed enclosure?

[christof123]

Hello all.

Have been trying to design a sealed cabinet for mostly music uses, but very occasional movie use.

I've opted to use a dayton audio 10" driver as this seems to be highly recommended.
Dayton Audio RSS265HF-4 10" Reference HF Subwoofer 4 Ohm

Willing to fork out a bit more, if the quality will be noticeable.

I'm struggling to get a flattish response to extend the low end.

http://img193.imageshack.us/img193/2...sddayton10.jpg

As can be seen in the image, i've currently used a 70L cabinet, as any bigger than this it becomes too obtrusive for the room.

Any help on improving low end response or driver improvements will be greatly appreciated.

Thanks

Chris

[rvrazvan]

I think that a transmission line is better suited for this task. With a sealed enclosure ....you need a very big enclosure for movies.

[j.michael droke]

Originally Posted by christof123

Hello all...I've opted to use a dayton audio 10" driver as this seems to be highly recommended...Dayton Audio RSS265HF-4 10" Reference HF Subwoofer 4 Ohm ...I'm struggling to get a flattish response to extend the low end. .... i've currently used a 70L cabinet, as any bigger than this it becomes too obtrusive for the room. Any help on improving low end response or driver improvements will be greatly appreciated.
ThanksChris

Hi there: Ran your driver RSS265HF4 through a box program LCD7 design suite:
sealed: 2.5 cf, F3=44hz, Qtc=0.56, Watts=31, SPL=99 about same as your simm
0.95cf, F3=42hz, Qtc=0.72, Watts=126, SPL=105 slightly better F3, ok Qtc
ported 2.5cf, F3=21.3, Qtc- n/a Watts=56, SPL=99 could port your box 3"dim x12.8"
1.55cf, F3=26.3, Qtc- n/a Watts=130, SPL=105, better SPL,lower F3,
and port 3"dim x 15.7"
Do not see lots of improvement possible with sealed enclosure from various sizes I ran, ported enclosure looks like it would meet your requirements. Hope this helps you make a decision and you will post your construction, and listening results (measurements if you do some). ...regards, Michael

[chris661]

Hi,

ESP - The Linkwitz Transform Circuit

You can simulate a LT circuit in winISD - on the EQ/Filter tab, click Add, then choose Linkwitz Transform from the drop-down menu.
Set the two boxes on the right to the LF extension/rolloff you desire, and hit Add.

Now, go to (on the main drop-down menu) Amplifier Aparent Load Power (VA), and see how much power you'll need (keep an eye on excursion too). You'll notice at really low frequencies (sub 20Hz), you need a lot of power, and a lot of excursion. We need to cut that down, just in case something in a movie decides to wreck your subwoofer (and it will - the example I've just tried required 140x the nominal power at 5Hz).
Add a high pass at a low frequency, 2nd order minimum.

Hope this helps.

[christof123]

Hi, thanks for the responses.

I wanted to avoid the ported route as I haven't yet heard a good one, so going with what i trust.

Transmission line? Surely this would end up being larger than a sealed? Also by occasional movie use I mean once every few months, so am designing towards a musical set-up.

Linkwitz transform - this looks very interesting, yet complicated. Are these commonly used?

[SpinMonster]

Originally Posted by christof123

I wanted to avoid the ported route as I haven't yet heard a good one, so going with what i trust.

Ported designs sound excellent as long as you tune for max flat rather than a peaked up resonse at a higher frequency. Tuning hgher just like using too small a box for sealed subs, results in underdamped boom.

Tune deeper and its more damped. The best ported results are overdamped.

The distortion you will have pushing equalization to make up for the 44Hz tuning in a sealed box will outweigh any benefit. Keep in mnd that big power is needed to get a 10 to extend flat in room and even then, it will not make much bass being that its starting off down 12db at 25hz and having its rated power handling limit. Ported will require 1/4 the power in your case to extend to 20/25 and have a fraction of the distortion.

[kipman725]

If you look on Home theater shack there is some testing of LT subs of the same volume as ported using the same driver at the same output levels and in all cases the distortion from the LT is worse and in almost all cases the required power input is greater. It only makes sense to me if having a port would subtract significantly from the internal volume which in your case with 70L isn't the case. I would also investigate using two or more smaller subs as this works better in a given volume. If money is no object small isobarik equalized subs could be used.

[chris661]

Originally Posted by kipman725

If you look on Home theater shack there is some testing of LT subs of the same volume as ported using the same driver at the same output levels and in all cases the distortion from the LT is worse and in almost all cases the required power input is greater. It only makes sense to me if having a port would subtract significantly from the internal volume which in your case with 70L isn't the case. I would also investigate using two or more smaller subs as this works better in a given volume. If money is no object small isobarik equalized subs could be used.

Could you provide more details/a link about this test: it hardly seems a fair comparison to me.

I have used a Linkwitz Transform myself, thinking a pair of 8" drivers would be enough to hit 28Hz with any authority. I hadn't at that point discovered the Apparent Amplifier Load tab on winISD, and cheerfully chucked 14dB gain at them. The result was nice enough, but didn't stand being turned up. Power went up hugely (excursion followed), and the cheap amp probably didn't help.

IMO, take it for what it is. Provided you set off with sufficient driver/amp capability, you can get decent amounts of bass from cabinets that aren't huge.

Chris

[revboden]

The HiVi sp10 is designed to be used with a Linkwitz transform. If you got one of them you could build a sunfire 10 clone. SUNFIRE: True Subwoofer EQ 10 - TS-EQ10

If 70L is it, you'll need to go with a folded slot port to tune low enough (~14hz) to keep the group delay low in the audible regions, if you were to think about going ported, as a round port would be too long and you'd get pipe resonances...

[vacuphile]

I could not say it any better

Optimum frequency response curves in the bass range.

For me, the equation usually goes into the direction of vented. If well done, no boominess or slowness at all,

vac