Why don't/can't we use our (sub) woofers from 0 to ~500hz?

[JinMTVT]

Why don't we use our subwoofers at higher frequencies?
I read about everyone cutting off their 12, 15 or 18" at the lowest possible freq wich is around 80-100hz ...

I know , i've read a few times that they aren't supposed to have good sonic qualities over 100hz ?? is that true ?
what makes a 12" or a 15" lesser capable of 200-500hz qualities than a similarly constructed 8" ?

Then what in the world is there in the 100-400hz range
in musical contents, that we compromise power for quality to the end of the scale ?

I can't see why a top quality 12"or 15" couldn't make accurate sound reproduction at 400-500hz, 500hz isn't that fast....

Also, using a subwoofer more up in the range leaves us with a better compromise for a "full range" or a combo of mid/tweet nah?

tell me if i got it all wrong please ,
is there a "universal or ultimate" call it whatever pleases you,
crossover point for SUB bass and mids ?
why do most choose 100hz ?


The continuing on the same path , how is the performance of mid woofers in the very low hz range?
i undertsand that we need lots of air movement to create same spl at lower frequency, but quality wise?
if the larger subwoofers don't perform equally to woofers
in the 100hz+ range, are the mi/woofers up to the notch at this point ?

thanks for any info

trying to sum it all before commiting to one design
based mostly on other's opinion ..

i want techical FACTS btw...

 

[pinkmouse]

80-100Hz is just about where the human ear loses it's ability to localise sound, so it's the highest you can go with a mono sub system. Go stereo, and with most drivers you can get up to around 200-300Hz. Higher, and you put a crossover right in the middle of the ear's most sensitive range, and most builders try to avoid that.

 

[ocaukrell]

Localization.

Do you really want the bass driver dictating where the sound image emanates from ?
Not saying it cant be done. It has been.

I have a pair of JBL 4311B studio monitors, consist of a 12", 5", & 1" every driver is paper (yes even the tweeter).
The 'crossover is a cap in series with the mid (1.5k) and a cap in series with the tweeter (6k).
The bass is allowed to run full range.
On spectrum analysis the bass goes up to 5k without any issues at all.
But my god it sounds terrible.
it needs to be crossed over at about 500hz, otherwise it interferes with vocals.
I've built a pair of Troels SP95's to replace the JBL's.
The 7" sspeak goes up to 2.5k, they sound incredable, BUT they really need to be cut off lower and have a midrange added (next project).

 

[JinMTVT]

What does STEREO subs will add then ?

I personally intented to use 4 15 to 18" in W-frame
( 2 on each side of course , under the rest of the drivers a la Orion one could say .. )

What do you define as the human earing most sensitive freq range? and what type of sound generates this freq ?

 

[ShinOBIWAN]

80-100Hz is just about where the human ear loses it's ability to localise sound, so it's the highest you can go with a mono sub system. Go stereo, and with most drivers you can get up to around 200-300Hz. Higher, and you put a crossover right in the middle of the ear's most sensitive range, and most builders try to avoid that.

Al,

What about 90% of 2-ways though with a crossover in the 1.5Khz-2.5Khz region. I've heard a few 2-ways that I've really liked despite this. Actually dismiss that comment because its hardly comparable to crossing at 500hz or so.

There's also the issue of directivity and beaming with large diameter woofers crossed over at say 400-500hz. Most true subs also have high inductance so that's a no no for decent upper range.

 

[johninCR]

What does STEREO subs will add then ?

I personally intented to use 4 15 to 18" in W-frame
( 2 on each side of course , under the rest of the drivers a la Orion one could say .. )

I use 4 12"ers per side in deep W baffles making them a hybrid W/U baffle. I use dividers so the maximum cavity height is 12", but I'm still unable to cross using a 12db slope much above 100hz before resonances rear their ugly head. They work great and make a sub unnecessary, however, there's just no way I can use them up to 500hz. It's not a driver limitation, it's a limitation of the alignment.

 

[filgor]

Why don't we use our subwoofers at higher frequencies?
I read about everyone cutting off their 12, 15 or 18" at the lowest possible freq wich is around 80-100hz ...

I know , i've read a few times that they aren't supposed to have good sonic qualities over 100hz ?? is that true ?
what makes a 12" or a 15" lesser capable of 200-500hz qualities than a similarly constructed 8" ?

Then what in the world is there in the 100-400hz range
in musical contents, that we compromise power for quality to the end of the scale ?

I can't see why a top quality 12"or 15" couldn't make accurate sound reproduction at 400-500hz, 500hz isn't that fast....

Also, using a subwoofer more up in the range leaves us with a better compromise for a "full range" or a combo of mid/tweet nah?

tell me if i got it all wrong please ,
is there a "universal or ultimate" call it whatever pleases you,
crossover point for SUB bass and mids ?
why do most choose 100hz ?


The continuing on the same path , how is the performance of mid woofers in the very low hz range?
i undertsand that we need lots of air movement to create same spl at lower frequency, but quality wise?
if the larger subwoofers don't perform equally to woofers
in the 100hz+ range, are the mi/woofers up to the notch at this point ?

thanks for any info

trying to sum it all before commiting to one design
based mostly on other's opinion ..

i want techical FACTS btw...

80-100Hz is just about where the human ear loses it's ability to localise sound, so it's the highest you can go with a mono sub system. Go stereo, and with most drivers you can get up to around 200-300Hz. Higher, and you put a crossover right in the middle of the ear's most sensitive range, and most builders try to avoid that.

The localisation issue is the key factor

A system that utilises a subwoofer for the very deep bass capitalises on the fact that our ears and brain cant localise sound at very low frequencies. If you crossover your sub well bellow 150Hz then your brain perceives that all the sound including the bass is coming from the midrange drivers that it can localise easily.
If you cross your sub at say 150Hz even with a 24dB/octave crossover your ears and brain will start to notice that the bass is coming from a different direction so you would have to place it between the stereo speakers, which is not normally a good position in terms of room acoustics.

Alternately you can set the crossover higher if you have 2 "stereo subwoofers" which may or may not be filtering their signals independently from the left and right channels. You would place them under or in the same cabinet as the midrange units.
It is a great idea but you may not be able place your subs specifically for bass response since they need to be with the mids. In this set up you are really talking about a bi-amplified stereo system, people generally only use the term "subwoofer" to describe an independently amplified bass unit if it is operated at very low frequencies and placed independently of your main speakers.


Going with a standard mono sub means that you can build a unit designed specifically to produce deep bass. It should be rather stocky in shape so that the air inside acts like a single simple compliance (air spring). For your main stereo speakers you might use tall and thin tower for good stereo imaging, aesthetics and ease of placement so you can put them where they produce the best stereo image. Without affecting the stereo image you can then place your subwoofer somewhere near a corner where it will produce the best bass response.

Using a sub also relaxes the demand for speaker size and amplifier power in your main or satellite speakers so that you can concentrate on perfect upper bass and midrange response.

In my opinion; stick with a mono subwoofer. Cross it over at 100Hz and build your main/Satellites specifically for 100Hz+ duty.

I usually use closed box satellites set at Fcb 100Hz and Qcb 0.7 (Butterworth alignment) give them a 12dB/octave high pass crossover at 100Hz
(My Denon Home Theatre Receiver provides an electronic 12dB/Octave Butterworth high pass when you set the main/satellite speakers as “small” on the set-up menu, I’m sure most modern receivers do likewise)
The bass roll-off of the Closed box plus the 12dB/oct crossover will form a perfect 24dB Linkwitz-Riley Transfer

Then use a 24 dB/Octave Linkwitz-Riley(Q=0.5) low pass for your sub.
(My Denon Home Theatre Receiver provides an electronic 24dB/Octave Linkwitz-Riley low pass on the subwoofer signal output, and again I’m sure most modern receivers do likewise. You can feed this signal into a simple full bandwidth power amp. If you use a purpose built subwoofer amplifier in this case you would set its crossover Frequency to maximum)

The result of this set up is a perfect integration between your subwoofer and main/satelites

You will not be disappointed.

 

[jimbob]

This is a question I've contemplated a bit. Seems the 100Hz is a nominal number that folks reckon is around about where our ability to perceive source direction goes out of the equation, hence single subs. To reach up into the 300-500 Hz range, would require two subs and some sort of consideration of placement relative to the mid and to the other sub. Have a look at http://www.geocities.com/adrian_mack/homepage.html to see an example of crossing over at 300 oddHz. THere are plenty of others and I think a number of Klipsh designs cross in the 450ish range. The drawback for these lowish crossovers when using passive components is the large inductors required.

Two further thoughts I've had are that the half power point for much music is in the 200-300Hz range as I understand it and that looks promising for using one conventional power amp per channel and active crossovers. The other point in considering crossover is how baffle step comes into the picture. Can we cross over at a point where we can boost the output of the bass driver to compensate a bit for the natural baffle step in the mid?

cheers,
Jimbob

 

[filgor]

Two further thoughts I've had are that the half power point for much music is in the 200-300Hz range as I understand it and that looks promising for using one conventional power amp per channel and active crossovers. The other point in considering crossover is how baffle step comes into the picture. Can we cross over at a point where we can boost the output of the bass driver to compensate a bit for the natural baffle step in the mid?

cheers,
Jimbob

I like your thinking Jimbob,

I have an example of Baffle step (Difraction loss) correction I ran on a simulation

If your mids were on a baffle in the order of say 190mm (7-1/2") wide (with nice rounded corners of course!).
It has a 6dB drop passing the -3dB point somewhere around 500Hz
You use an active crossover of 12dB/Oct Q=0.5 each side
Set the crossover frequency at 400Hz (not 500Hz)
Set the bass at 6dB higher in gain than the midrange

It cancells out the step rather nicely and although We could take it further and allow for the bass reinforcement fom floor reflection.. It gets complex!

The upper range in this case as you were motioning towards would be taking less than half the power.. Cool!

Even if I used this set up I would still be tempted to send sub bass to a mono subwoofer at say 80Hz. Its hard to beat a dedicated mono sub located in the corner!

I played around with this baffle step idea some time back but realised that I was spending more time building active crossovers and multi chanel power amps than listening to my system. I gave the idea away after I found out that Modern Home Theatre recievers have seriously high performance active crossover settings that they dont even advertise.

I compensate for baffle step in the speaker using Passives so that I dont have to use a specific amp with a specific speaker

 

[JinMTVT]

please let's keep this thread "crossover free "
we now have multiple ways ( ex. DCX2496 ... ) of dealing with crossovers, wich implies digitally, so no need for fancy electronic parts and everything can be adjusted to best posssible compromise ...

why not use STEREO SUBWOOFERS ?
it's true that we don't see that too often ..
almos everybody uses a powered sub box in mono

and then , we don't all use RECEIVERS ..
i can't have a stereo downmix to mono for my sub with the equipment i am using now ... would require me to do some sort of active filter downmix electronical gizmo ..

so ShinOBIWAN, please explain about the high inductance of subwoofers!! interested !


One other quetsion for you all ,

what do you think will play the best quality sound @ 100HZ :

- 4 stereo 18" of high quality ..maybe pro drivers, in some kind of dipole arrangement

- more than a few 6" to 8" drivers on each side ( aka array style)
with similar quality compared to the 18"

?????


What is the more important thing at 100hz?
power or quality ?
@ 200hz?
@300hz ?
when does quality takes over completly ?

 

[johninCR]

what do you think will play the best quality sound @ 100HZ :

- 4 stereo 18" of high quality ..maybe pro drivers, in some kind of dipole arrangement

- more than a few 6" to 8" drivers on each side ( aka array style)
with similar quality compared to the 18"

Same quality at 100hz. All are operating well within their range of pistonic operation and tonality is not going to come into play at 100hz. The problem with the small drivers in OB (as long as you have enough of them to move an equal amount of air) is that they generally aren't going to have a low enough Fs to easily reach flat down to 30hz. Small drivers simply aren't designed for that task.

 

[tade]

Sort of off topic in that it is a specific question;
I want to do a two way setup using a dayton hifi 12" sub down from 500 and from 500 up an altec compression driver. The altec dictates the crossover frequency and I intend to actively amplify them.
Should this sound reasonable?

Thanks