How high should a subwoofer play?

[exipnos]

Hi there,

How high can the subwoofer play without the listner being able to localise the bass? I belive the THX spec calls for speakers to go as low as 80hz and then the subwoofer takes over. At this frequency the bass is not "localizable".

I will be building some NSB line arrays that will be OB. I therefore don't expect them to play low and definately not down to 80Hz. Do I need to consider adding additional woofers making each speaker a 3way? I would rather stay with 2way OB if its possible to combine with a subwoofer in a way that will work for HT.

I was thinking of doing dipole bass for the subwoofer. Then maybe a boxed subwoofer for the very low frequencies.

Please advice.

Regards,

Exipnos

[Rademakers]

80 Hz would be the rule of thumb.

It depends on the subwoofer, placement, roomacoustics, distance between sub and tops, distance from sub, etc.

The highest I could ever cross a subwoofer without localizing was 120 -130 Hz and only in downfire position.
Which crossover frequency do you think you're going to use?

The higher you cross, the closer you should place the tops to the sub(s).

Wkr Johan

[exipnos]

Thanks for the reply.

I don't know the crossover yet, but I doubt that the open baffled NSB will play as low as 120-130!

What do you mean with subwoofer should be placed close to the "tops"?

The more I think about it the more I see a need for 3way if I will do OB. If I go ported then I can probably go lower with the NSB and stay with 2way.

[Tweeker]

Im planning to cross my nsb array to the $10 12" woofers PE is selling, also mounted OB, though shipping probably makes that untenable for you. It would be a three way.

[exipnos]

Hi Tweeker.

I won't get the PE 12" but I can probably find something similar over here.

How many 12" are you going to use per tower? How many NSB per tower and what tweeter are you using?

Cheers,

Exipnos

[Rademakers]

What do you mean with subwoofer should be placed close to the "tops"?

The tops would be the speaker or set of speakers you use above your sub frequency-wise. In this case the OB.

By placing the woofer and mid close together you prevent having a "gap in the sound image". Close would be within 1/4 wavelength of the frequency you cross at.

Johan

[Mark Techer]

just an FYI but 80Hz was chosen by THX because it was the best compromise found by playing a variety of sources. In the end, it turned out a recoding of a male humean voice revealed limitations of crossing over any higher and the playback seemed to lack any lower.

On a lot of other forums, the members are crossing at 50Hz. I use 80hz but also designed my speakers (Sub/Sat) around that frequency...

Mark

[exipnos]

I've see mentioned here and there that THX made some misstakes when setting their specifications. If I was to design the speaker/subwoofer combination whats the best compromise in todays world? Should I design HT speaker to go lower then 80 and then the subwoofer to be crossed over at that frequency?

So the general concensous is to cross 80 or lower. I guess that forces me to investigate woofers to complement low end on my line array.

Cheers,

Exipnos

[Mark Techer]

I've see mentioned here and there that THX made some misstakes when setting their specifications.

I wouldn't exactly call it a mistake, but a compromise. It works for the majority of program, with some program needing a lower crossover and other stuff wanting a higher frequency. In the end though, your ears will determin wat is right for you. What crossover (to the sub) will you use, and is it built into an audio visual receiver or it an external device?

Mark

[Tweeker]

./ 1 12 and 3 NSBs per panel. 3/8" dome Onkyo buyout tweeters to be
/ replaced with planars when I can afford to. Panels aimed to converge
| near the far end of the room so as to not have ultranarrow sweetspot.
|
|
\
.\