Bass Quality in Sealed Speakers

[mike7877]

If you have speakers of sealed design, you know, first hand, their bass.

The control compared to their ported brethren...

The extension isn't there, but the bass that is there, is great!!
(Actually, the shallower roll-off of sealed speakers can create the effect of lower extension, but that's not the point right now)

Recently, I decided to extend the bass of my sealed speakers - their -6dB point is 56Hz. This means, that the mid-high 30Hz range, is their -12dB point now...
(Consider the room gain, and that-6dB is really 30something Hz, but like before, that's not the point right now)

So what I did was, I found my speakers' total Q (woofer in box), and matched it in an EQ (+12dB low shelf centered on 56Hz (the +6dB point...))

What did this make? Effectively, a speaker with its roll-off exactly one octave below. Bonus? The +1.3 dB bump that would normally be centered (and covering) the 34-60Hz range is removed. Why would there be a bump there? Because normally, there is a bump in the 76-120Hz range, and that would be moved down without correction.

This new-found bass?

First of all, it's very nice to have a nearly full-range speaker. At times, though, it can be very annoying having a [nearly] full-range speaker.
But I got used to it... Then I made an equalizer preset to cut the bass when listening to songs/albums I found to be too "bass heavy" when the entire audible spectrum was reproduced.

Then I did a lot of listening. Then I moved around a lot to determine that I was hearing what I was hearing, and not the room.

The newly added bass was different. I'd describe it as looser, almost ported. After training, I'd say the difference is most noticeable in the 20Hz to 53Hz range. When you're listening to music with bass notes all over the place in the 40-100Hz range, everything above 60Hz or so is imperceptible from perfect (ie. a 60Hz tone seems to have the start and stopping power of a 130Hz tone, which is the same as a 300Hz tone, but starting from about 53Hz, the tone takes on a looser characteristic, that is the only way I can think to describe it. Maybe it's overhang, maybe it's a delay starting. Maybe it's both! I still don't have enough experience to say for sure what the change is that's causing my perceived change in quality. I've moved far enough away from the source to know it's not level related (level is definitely flat).

Does anyone else do this with their sealed speakers? It's really great... I don't think I could recommend it enough. You might think it will get your woofers moving too much, but depending on where roll-off is (the one dictated by physics, not the new one), you're boosting frequencies that aren't usually very high in level to begin with - cone movement isn't extremely exaggerated. Of course, there's a lot of music with just as much bass energy in the 30/40Hz as the 60s - 80s, and you'll have to be more careful with those - but most often, I'd say, you're not losing anywhere near all the all 12dB you boosted - it's more like 3-4dB. The 50-60Hz range you're only boosting about 6dB, and under that things are usually quieter anyway. I'm lucky in the potential/accidental damage regard because the x-mech of my woofer is 40mm, and its voice coil is 8mm high, magnetic gap 20mm... so even in an absolute worst-case accident, I wouldn't be introducing the back plate to Mr. Coil Former... If you do have woofers that can bottom out, and you want to do this, I'd say be extra careful at first, and always know the LF content of what you're putting on before turning it up real loud. I swear some producers are a-holes on purpose, so don't just fast-forward a minute and listen for 15 seconds at -8dB, you have to know your music!

Has anyone else extended the frequency response of their sealed speakers? How did you like the results?

 

[ppataki]

If you have speakers of sealed design, you know, first hand, their bass.

The control compared to their ported brethren...

The extension isn't there, but the bass that is there, is great!!
(Actually, the shallower roll-off of sealed speakers can create the effect of lower extension, but that's not the point right now)

Recently, I decided to extend the bass of my sealed speakers - their -6dB point is 56Hz. This means, that the mid-high 30Hz range, is their -12dB point now...
(Consider the room gain, and that-6dB is really 30something Hz, but like before, that's not the point right now)

So what I did was, I found my speakers' total Q (woofer in box), and matched it in an EQ (+12dB low shelf centered on 56Hz (the +6dB point...))

What did this make? Effectively, a speaker with its roll-off exactly one octave below. Bonus? The +1.3 dB bump that would normally be centered (and covering) the 34-60Hz range is removed. Why would there be a bump there? Because normally, there is a bump in the 76-120Hz range, and that would be moved down without correction.

This new-found bass?

First of all, it's very nice to have a nearly full-range speaker. At times, though, it can be very annoying having a [nearly] full-range speaker.
But I got used to it... Then I made an equalizer preset to cut the bass when listening to songs/albums I found to be too "bass heavy" when the entire audible spectrum was reproduced.

Then I did a lot of listening. Then I moved around a lot to determine that I was hearing what I was hearing, and not the room.

The newly added bass was different. I'd describe it as looser, almost ported. After training, I'd say the difference is most noticeable in the 20Hz to 53Hz range. When you're listening to music with bass notes all over the place in the 40-100Hz range, everything above 60Hz or so is imperceptible from perfect (ie. a 60Hz tone seems to have the start and stopping power of a 130Hz tone, which is the same as a 300Hz tone, but starting from about 53Hz, the tone takes on a looser characteristic, that is the only way I can think to describe it. Maybe it's overhang, maybe it's a delay starting. Maybe it's both! I still don't have enough experience to say for sure what the change is that's causing my perceived change in quality. I've moved far enough away from the source to know it's not level related (level is definitely flat).

Does anyone else do this with their sealed speakers? It's really great... I don't think I could recommend it enough. You might think it will get your woofers moving too much, but depending on where roll-off is (the one dictated by physics, not the new one), you're boosting frequencies that aren't usually very high in level to begin with - cone movement isn't extremely exaggerated. Of course, there's a lot of music with just as much bass energy in the 30/40Hz as the 60s - 80s, and you'll have to be more careful with those - but most often, I'd say, you're not losing anywhere near all the all 12dB you boosted - it's more like 3-4dB. The 50-60Hz range you're only boosting about 6dB, and under that things are usually quieter anyway. I'm lucky in the potential/accidental damage regard because the x-mech of my woofer is 40mm, and its voice coil is 8mm high, magnetic gap 20mm... so even in an absolute worst-case accident, I wouldn't be introducing the back plate to Mr. Coil Former... If you do have woofers that can bottom out, and you want to do this, I'd say be extra careful at first, and always know the LF content of what you're putting on before turning it up real loud. I swear some producers are a-holes on purpose, so don't just fast-forward a minute and listen for 15 seconds at -8dB, you have to know your music!

Has anyone else extended the frequency response of their sealed speakers? How did you like the results?

I have been designing sealed speakers only in the last 4-5 years partly because of the reasons you mentioned above
I have had like 15+ builds now, you can see all of them here on ASR

The reason you hear the added bass being similar to ported speakers is that when you use a low-shelf filter or a Linkwitz Transform filter to boost the lows you will not only boost in the frequency domain but also the group delay. The elevated group delay will give you the sense of a somewhat 'sluggisher' bass

Try using a linear phase low-shelf boost filter - that will not increase the group delay and you will find that added bass less similar to ported sound
See my post about this with measurements here

 

[Penelinfi]

Buchardt A10 for eg.. And many other active speakers EQ sealed or even ported speakers.


I also add a little more low end to my speakers since I don't listen too loud

 

[Tell]

Yeah I've done it with my computer speakers, a pair of Tangent Evo E4, they have a 4" woofer in a 3-4 liter sealed box with a -3dB at around 70hz. I did a quite aggressive EQ where I lifted I think it was 30hz with around 30dB which gave them a VERY impressive sound considering the small size. Was listening in nearfield and not at blasting levels of course so it sounded really good for what it was.
I had a quite bad room mode though at around 80-90hz which still made them sound a bit "hollow", so I instead connected my 6" tapped horn which took care of the bass instead which sounded even better while also playing quite a bit louder.

So yeah if you have x-max to take from and enough power in your amplifier you can EQ the bass quite a lot!

 

[mike7877]

Buchardt A10 for eg.. And many other active speakers EQ sealed or even ported speakers.


I also add a little more low end to my speakers since I don't listen too loud

Ah, yes, I didn't mention that - I add bass too sometimes, usually it's just 1.5-2dB, sometimes up to 3-3.5dB. Just because the low end is extended to the very bottom, doesn't mean there's enough in the 50-100Hz range (especially at lower levels)

 

[mike7877]

Yeah I've done it with my computer speakers, a pair of Tangent Evo E4, they have a 4" woofer in a 3-4 liter sealed box with a -3dB at around 70hz. I did a quite aggressive EQ where I lifted I think it was 30hz with around 30dB which gave them a VERY impressive sound considering the small size. Was listening in nearfield and not at blasting levels of course so it sounded really good for what it was.
I had a quite bad room mode though at around 80-90hz which still made them sound a bit "hollow", so I instead connected my 6" tapped horn which took care of the bass instead which sounded even better while also playing quite a bit louder.

So yeah if you have x-max to take from and enough power in your amplifier you can EQ the bass quite a lot!

You reminded me - I've also done small speakers - my Realistic SM-7 (I think they are called - 3" woofer, 1" dome, aluminum box that's maybe 1.1L. I didn't quite give them 30dB, but 24dB. I think their first -6dB point is around 105Hz. I made the first 12dB shelf 105, then the next 52 (or something... Q of ~1.35)

 

[mike7877]

I have been designing sealed speakers only in the last 4-5 years partly because of the reasons you mentioned above
I have had like 15+ builds now, you can see all of them here on ASR

The reason you hear the added bass being similar to ported speakers is that when you use a low-shelf filter or a Linkwitz Transform filter to boost the lows you will not only boost in the frequency domain but also the group delay. The elevated group delay will give you the sense of a somewhat 'sluggisher' bass

Try using a linear phase low-shelf boost filter - that will not increase the group delay and you will find that added bass less similar to ported sound
See my post about this with measurements here

Nice! Thanks for the tip - I will definitely try linear phase for that purpose. Is there a specific detriment to using linear phase?
15 builds is a lot, I'll check them out

 

[Sokel]

12dB in the most power consuming point can be quite a task for an amp even at low levels,and that adds to the rest of the EQ applied.

Did you applied equal amounts of negative gain?How that affected gain structure,SNR,etc?Did you measure the chain before-after?

 

[ppataki]

Is there a specific detriment to using linear phase?

If you check the post that I linked above you will see that the main drawback of using LP filters is the elevated pre-ringing
Now if that is audible that is a different question... the amount of pre-ringing depends on the filters you use (Q value mainly) and the implementation of the linear phase plugin

Another drawback is the time delay but if you are just listening to music that is a non-issue (given that you apply the same LP plugin on all the channels ensuring equal time delay for all). And even if you watch movies there are players (like Jriver) that will automatically delay the video to sync to the audio - so again, no issue

Basically you can boost the lows of a sealed speaker until you reach either the xmax of the driver and/or the power output limit of the amp
I ensure no clipping in the digital domain by using 64-bit digital volume control upstream (=volume control is the first DSP item in the chain) in Jriver

 

[voodooless]

I'd describe it as looser, almost ported

As @ppataki says, that's not surprising. You changed the frequency response, therefore the Q and consequently group-delay of the system. They will inevitably be closer to a traditional ported system.

Given that frequency response is king when it comes to SQ, the best thing you can do is make sure you have a flat in-room response and have it extend as low as possible. That will deliver the best group delay, and shift the group delay bump as far down in frequency as possible. Usually, it's more efficient to do this with a ported system, and it elevates the need for a linear phase filter, which for bass, @ppataki already mentioned the drawbacks for.

 

[ppataki]

Just one more thing I would add which is totally subjective:
For some systems I do prefer to use normal min-phase low-shelf filters to purposefully add that group delay - it gives that 'meaty' bass sound that sounds pleasing
(whereas I do not prefer that with some other systems)

 

[bmc0]

The reason you hear the added bass being similar to ported speakers is that when you use a low-shelf filter or a Linkwitz Transform filter to boost the lows you will not only boost in the frequency domain but also the group delay.

There is no more group delay than you'd get if your speakers simply had a lower corner frequency. Being minimum phase, a Linkwitz transform exactly compensates both the frequency and time response to be identical to a system which natively has the resulting frequency response. See this, from Linkwitz himself.

 

[gnarly]

There is no more group delay than you'd get if your speakers simply had a lower corner frequency. Being minimum phase, a Linkwitz transform exactly compensates both the frequency and time response to be identical to a system which natively has the resulting frequency response. See this, from Linkwitz himself.

Quoting Linkwitz from that fine link, thx ...
"This allows to extend the response of a closed box woofer to lower frequencies, in the above circuit example from 55 Hz to 19 Hz, provided the driver has adequate volume displacement capability and power handling."

Adequate volume displacement capability has been the wall I've run into whenever applying a Linkwitz transform.
I've had to either put in a high-pass to protect from over excursion, or limit the sub's overall SPL by the amount of the LT boost.
The high-pass makes the sealed LT sub behave/sound more like a ported, ime.

Whereas with no high pass, I'm OK with overall limiting, other than needing to double up on subs to get back to starting SPL.

With no-high pass and no limiting ....sooner or later = bye bye sub. (for me, being a SPL and bass junkie)

 

[voodooless]

Adequate volume displacement capability has been the wall I've run into whenever applying a Linkwitz transform

There is one major flaw with these nice mathematical transformations: your not listening to the sub alone. The room plays a major part. When you apply an LT, more than likely your bass boost is way too much, leading to higher groupdelay, and unnecessary high displacement.

It’s much better to just forget about the silly math, get out your microphone and EQ your sub to a flat in-room response looking at the resulting EQ boost to make sure it will be okay for the driver physics. And if possible, enable a frequency dependent compression limiter to shave off the worst of the offending low frequencies. And if you must roll off, make it gentle. It’s way less audible and can make quite a difference.

 

[gnarly]

It’s much better to just forget about the silly math, get out your microphone and EQ your sub to a flat in-room response looking at the resulting EQ boost to make sure it will be okay for the driver physics. And if possible, enable a frequency dependent compression limiter to shave off the worst of the offending low frequencies. And if you must roll off, make it gentle. It’s way less audible and can make quite a difference.

Yeah, I gave up on the miniDSP LT biquad spreadsheet using openDRCs, after a few sealed-sub tries. Just plain too much low end boost.

I do measure to setup subs, but not indoors. I go out on driveway to make ground plane measurements and tune DIY ported subs for maximally flat to designed f-3 corner.
Then indoors, if I measure room gain (which is always a good bit less than models predict),..... I EQ the room gain out.

I've played with frequency dependent limiting. It can allow nearly flat phase / no group delay, at lower SPLs. But then at higher SPL it behaves just like a regular fixed filter.
Pretty cool really, but a PIA to implement because so far the only way I've found is to measure amp voltage under limiting.

Also spent a big amount of time, reducing the phase rotation of the low end roll-off via FIR....it's a tug of war between group delay and pre-ring potential. Presently I kind of use enough phase flattening to split their negative effects equally.

 

[DVDdoug]

I think it was 30hz with around 30dB which gave them a VERY impressive sound considering the small size.

+30dB is 1000 times the power!!!!

You are clipping your amplifier and hearing bass harmonics/distortion. If your amplifier had enough power you'd burn-out the little woofer.

Every 3dB represents a doubling of power (approximately):
+3dB = X2 power
+6dB = X4
+9dB = X8
+12dB = X16
+15dB = X32
+18dB = X64
+21dB = X128
+24dB = X256
+27dB = X512
+30dB = X1024

...And because power is equal to the square of the voltage, +6dB represents a doubling of voltage. 30dB is sort-of a "magic number" where 30dB of gain is a voltage gain of about 30X.

 

[DearSX]

Buchardt A10 which I own are decent with bass, but every time you half the frequency, like 40hz vs 20hz, you need to move 4 times as much air. a 6.5 inch mid-bass can only do so much at 40hz and below. So the A10 is better for listening at 80db or so full range.

The KH310 (sealed 8" woofer) can probably output more than the A10. KLH model 5 is a sealed 10" woofer. I have a sealed 10" DIY 3-way and it can get to 30hz with good punch, but it uses big cabinets.

 

[Sokel]

+30dB is 1000 times the power!!!!

You are clipping your amplifier and hearing bass harmonics/distortion. If your amplifier had enough power you'd burn-out the little woofer.

Every 3dB represents a doubling of power (approximately):
+3dB = X2 power
+6dB = X4
+9dB = X8
+12dB = X16
+15dB = X32
+18dB = X64
+21dB = X128
+24dB = X256
+27dB = X512
+30dB = X1024

...And because power is equal to the square of the voltage, +6dB represents a doubling of voltage. 30dB is sort-of a "magic number" where 30dB of gain is a voltage gain of about 30X.

I already pointed out that,and only for 12dB boost.
I made some calcs,with a typical 88dB sensitivity speaker one can get away with an NC1200 or an 1200as for a typical 75-78dB average without excessive peaks like in classical if the speaker can handle it.
Or else,a great amount of attenuation and way lower levels.

 

[pogo]

Useful extensions can be found in this database (not only sealed designs): Link

 

[Tell]

+30dB is 1000 times the power!!!!

You are clipping your amplifier and hearing bass harmonics/distortion. If your amplifier had enough power you'd burn-out the little woofer.

Every 3dB represents a doubling of power (approximately):
+3dB = X2 power
+6dB = X4
+9dB = X8
+12dB = X16
+15dB = X32
+18dB = X64
+21dB = X128
+24dB = X256
+27dB = X512
+30dB = X1024

...And because power is equal to the square of the voltage, +6dB represents a doubling of voltage. 30dB is sort-of a "magic number" where 30dB of gain is a voltage gain of about 30X.

I know how a clipping amplifier sounds like and tihis wasn't that. Mind you I didn't play especially loud, just at comfortable levels at around half a meter from them.