Sealed vs Ported Loudspeakers: Which is Better?

[TLS Guy]

Yeah, but I think the answer is more complex than this, at least if I understand what you're saying. A system-level Q=0.7 is not the only way to "adjust" bass response. I much prefer a flat response like a Q=0.5 design will give you, but I think an overall, in-room frequency response that tilts up starting at about 100Hz and being about +3db by 20Hz, and is tilted down about 2-3db by 20KHz sounds most natural in a lot of home listening rooms. In other words, small listening rooms. IMO, simply saying the answer is a speaker or an overall system with critical damping isn't sufficient to get "realistic" sound.

Large concert halls generally have pretty consistent bass for any seats away from the walls, but medium-size venues as jazz is often played in have far less even bass response. The music sounds different depending on where you sit; there's no one "right" sound.

Obviously with pop or rock music there often isn't a performance you're reproducing in the classic sense, and I think the Q=0.7 speakers are mostly aimed at this market. Let's face it, it is the majority of the market, and I haven't even mentioned the totally contrived foley of movies.

You have made a good point. Small rooms are a problem, with lumpy bass response from reflected waves and cancellations. However the time element is important and low Q highly damped speakers with lack of hangover, don't feed into these room issues as much as undamped ones do.

You can easily demonstrate the time element of exciting a resonance with a weight on a spring. The longer you excite the resonance the greater the amplitude of the resonance. When it comes down to it, Q is very much about time.

 

[TLS Guy]

To be honest, I'm not seeing a massive difference in impulse response between the 20Hz and 15Hz modes, although the sealed mode is clearly cleaner. Actually, I'd say the 15Hz mode looks better to my eye than the 20Hz mode. For example, in 20Hz mode in that first set of positive spikes after the original impulse, you can see a spike bumping well above the 40% mark and then going down below -20%. Conversely in 15Hz mode, the spike just nudges above the 40% mark, and doesn't make it back down to -20%.



Suffice it to say, I didn't buy the PB13 with the intention of running in sealed mode, especially not for HT, but for what's basically a freebie, it seems to be a quite well executed one.

The ripple is greater in the 15 Hz mode and the impulse is more prolonged, so you can see the extended bass response has a higher Q which it always does.

I would bet in a double blind trial there would be preference among experienced listeners for the 20 Hz mode over the 15 Hz mode.

I will always trade bass extension to tighten things up.

You may have noticed a recent poster who built the design for the JL audio 8" driver. He particularly commented on the tighter bass compared to commercial ported subs.

 

[lsiberian]

I personally prefer sealed speakers and subwoofers. With proper damping they certainly fill the bill.

 

[Steve81]

The ripple is greater in the 15 Hz mode and the impulse is more prolonged, so you can see the extended bass response has a higher Q which it always does.

I'm sorry to be insistent, but I'm just not seeing it. I'm posting what I'm seeing, with the biggest differences highlighted in red, which indicate to me at least that the 20Hz tune is giving a bigger ripple. The dip between 50 and 100ms also looks lower in magnitude for the 15Hz tune, and I'd also note past 100ms I'm hesitant to say I see much of a difference at all.

 

[lsiberian]

I'm sorry to be insistent, but I'm just not seeing it. I'm posting what I'm seeing, with the biggest differences highlighted in red, which indicate to me at least that the 20Hz tune is giving a bigger ripple. The dip between 50 and 100ms also looks lower in magnitude for the 15Hz tune, and I'd also note past 100ms I'm hesitant to say I see much of a difference at all.

The 15 hz tune puts greater port compression on the driver because it has less area to breathe through. In my experience this reduces SPL and muddies bass. Also it requires great power to reach the same SPL at 20 hz in a 15hz tune which puts more stress on the driver and amp.

Aiming for low extension is based of LLT which is a Steve Callas concept that seeks to go as deep as possible(rotary sub anyone), but TLS and I do not agree with it's practice. We feel you should give your best at 20 hz and higher and not stress the lower reaches to their detriment. Audibility goes away below 20hz and most of the impact bass is actually higher in the track.

Obviously it's your sub and your choice, but we both would advise the 20hz tune nearly universally for the best sound quality and most headroom.

If you really want to go deep see Danley.

 

[Ricardojoa]

Well since building speakers are about trade offs, why not design a 3 way speaker with a 7 or 8 inch in sealed cabinet with Q around .7 then pair it with a sub tuned to 0.5 Q aligment. If one were to build a speaker with low Q, generally it will loose some punch . With two woofer, one small and one big we can achieved an overall more balance bass. I have an old pair altec lansing with dual 8 inches in a sealed cabinet and they must be tuned to high Q cause they are relative snappy, but when i integrated them with the rythmik( adjusted to low Q) the overall sound is that they sound pretty big with snappy bass.

 

[lsiberian]

Well since building speakers are about trade offs, why not design a 3 way speaker with a 7 or 8 inch in sealed cabinet with Q around .7 then pair it with a sub tuned to 0.5 Q aligment. If one were to build a speaker with low Q, generally it will loose some punch . With two woofer, one small and one big we can achieved an overall more balance bass. I have an old pair altec lansing with dual 8 inches in a sealed cabinet and they must be tuned to high Q cause they are relative snappy, but when i integrated them with the rythmik( adjusted to low Q) the overall sound is that they sound pretty big with snappy bass.

0.7 will give you a boomier response than 0.5 though. I suggest aiming for 0.5 qtc when designing a speaker. For a 3-way there is no need for multiple chambers since there are numerous sealed midranges on the market already critically damped.

 

[Steve81]

The 15 hz tune puts greater port compression on the driver because it has less area to breathe through. In my experience this reduces SPL and muddies bass. Also it requires great power to reach the same SPL at 20 hz in a 15hz tune which puts more stress on the driver and amp.

This I understand and is noted by Josh that some port noise could be triggered at the limits.

On the other hand, he also outright states "15Hz mode might be the best all around operational mode for the PB13-Ultra. It offers useful extension to 15Hz or lower in room and very low distortion coupled with a large amount of output headroom." Not exactly a damning rebuke of SVS's offering of the option.

I'm also still apparently blind to the problem in the impulse response. I don't mind eating crow if someone would show me the error of my ways

 

[GranteedEV]

I disagree with a lot of what's been said in this topic regarding Q, Extended Bass Shelfs, Impulse response overhang, etc etc.

I think power compression affects frequency response and subsequently so-called q. Most preference for "low q" is probably rooted in the fact that drivers used in hifi are inefficient and thus experience a rise in q. What was modeled as flat response becomes a bump in response at high drive levels which are to be expected in the bass. So that """resonant""" .707 Qtc box is now much higher and that non resonant .55 Qtc only becomes .8 - barely even half a db of response bump. Nothing is wrong with mid Q if you can address the issue of power compression.

I think preference for sealed over ported has to do with standing waves. Most ported speakers are not treated as Mass-Loaded Transmission Lines and thus exhibit aberrations which remained unsimulated. ML-TLs are ported boxes that are actually behaving as intended.

Yes a lower tune has a longer impulse. That's obviously because it represents a lower frequency -it SHOULD!!! We may as well strive for F3s at 100hz for the shortest impulse we can get. No bass = ""tight bass". Slow bass = deep bass. The key is for any one region to not be over emphasized. If your room has pressure vessel gain then your optimal alignment should work on conjunction.

Beyond that I am in my phone. can't type too much on android keyboard.

 

[Irvrobinson]

I disagree with a lot of what's been said in this topic regarding Q, Extended Bass Shelfs, Impulse response overhang, etc etc.

I think power compression affects frequency response and subsequently so-called q. Most preference for "low q" is probably rooted in the fact that drivers used in hifi are inefficient and thus experience a rise in q. What was modeled as flat response becomes a bump in response at high drive levels which are to be expected in the bass. So that """resonant""" .707 Qtc box is now much higher and that non resonant .55 Qtc only becomes .8 - barely even half a db of response bump. Nothing is wrong with mid Q if you can address the issue of power compression.

I think preference for sealed over ported has to do with standing waves. Most ported speakers are not treated as Mass-Loaded Transmission Lines and thus exhibit aberrations which remained unsimulated. ML-TLs are ported boxes that are actually behaving as intended.

Yes a lower tune has a longer impulse. That's obviously because it represents a lower frequency -it SHOULD!!! We may as well strive for F3s at 100hz for the shortest impulse we can get. No bass = ""tight bass". Slow bass = deep bass. The key is for any one region to not be over emphasized. If your room has pressure vessel gain then your optimal alignment should work on conjunction.

Beyond that I am in my phone. can't type too much on android keyboard.

As sometimes happens, you've gone way over my head with theory. I'm not seeing how a speaker capable of, say, 100db at 40Hz is suffering from power compression at a more likely 90db at 40Hz. What am I missing?

I'm also not understanding your standing waves comment. Standing waves where? In the cabinet? If so, then I think I get it.

 

[GranteedEV]

As sometimes happens, you've gone way over my head with theory. I'm not seeing how a speaker capable of, say, 100db at 40Hz is suffering from power compression at a more likely 90db at 40Hz. What am I missing?

I'm also not understanding your standing waves comment. Standing waves where? In the cabinet? If so, then I think I get it.

TS Parameters are for example often recorded at 1W. But due to heat, which is very real, at 100W your QTS has likely gone up significantly. If you model at 1W, Then your q = 0.707 is only true at 1W. Now you listen at 200W and hear a lot more punch than expected. You blame the q = .707 when really that's not the q you are hearing.

it's not compression yet, but it's thermal modulation of system resonance.

Standing waves inside ported boxes create quarter wave resonances and alter tuning and frequency response.

 

[Irvrobinson]

TS Parameters are for example often recorded at 1W. But due to heat, which is very real, at 100W your QTS has likely gone up significantly. If you model at 1W, Then your q = 0.707 is only true at 1W. Now you listen at 200W and hear a lot more punch than expected. You blame the q = .707 when really that's not the q you are hearing.

it's not compression yet, but it's thermal modulation of system resonance.

Standing waves inside ported boxes create quarter wave resonances and alter tuning and frequency response.

I see your standing waves point, if that is what happens (and I'm no judge).

I admit to still being a skeptic of the thermal issue in most home environments. Is 10W of heating - which is more likely with music in the bass than your 100-200W examples - really an issue considering the size and weight of modern voice coils?

 

[GranteedEV]

I admit to still being a skeptic of the thermal issue in most home environments. Is 10W of heating - which is more likely with music in the bass than your 100-200W examples - really an issue considering the size and weight of modern voice coils?

Even peaks contribute to heating - not just average levels.

Remember that thread where you said your salon2s were taking every bit of 600W on peaks? They have to dissipate that power... they are FAR from efficient. No imagine a third of the woofers, and a less ultra high end woofer. Realize that opinions are often formed from listening to inexpensive gear.

Your Salon2s have a lot of heat dissipation. Three 8" woofers... actually SUBwoofers with huge voice coils and lots of venting. I would not say that is the norm.

Your Velodyne is a dedicated and equalized sub. It surely has a lot of heat dissipation - it must also be a high q design by nature because it is extremely relatively small. If it were boomy sounding because of its q you would hear that. but equalization does correct q for a given SPL because q is related to frequency response.

And I'm not sure "modern" drivers is a safe assumption. At least a few people in this thread had their opinions on Q formed a long time before that...

By avoiding thermal modulation we avoid CHANGES to Q dependant on drive level. Without that control in place we should not judge "q" with broad statements. That relates back to why I don't follow the idea that q = .7 could be boomy. Of implies a nice flat frequency response - and the location of the rolloff knee is a function of fs NOt q. How that translates to boominess when our hearing at LF is a function of frequency response is what I disagree with. Thus I think thermal modulation is a strong explanation for what is often heard on these uncontrolled listening tests.

 

[Irvrobinson]

Even peaks contribute to heating - not just average levels.

Agreed.

that thread where you said your salon2s were taking every bit of 600W on peaks? They have to dissipate that power... they are FAR from efficient. No imagine a third of the woofers, and a less ultra high end woofer. Realize that opinions are often formed from listening to inexpensive gear.

Your Salon2s have a lot of heat dissipation. Three 8" woofers... actually SUBwoofers with huge voice coils and lots of venting. I would not say that is the norm.

I remember. An old man listening to a Beach Boys tribute band, albeit grandly recorded, too loudly. This thread, however, has been discussing general concepts about Q under more, ahem, normal circumstances, which is why I was leaning us towards a 10W discussion. I agree that the Salon 2s are not typical.

I'm not sure "modern" drivers is a safe assumption. At least a few people in this thread had their opinions on Q formed a long time before that...

By avoiding thermal modulation we avoid CHANGES to Q dependant on drive level. Without that control in place we should not judge "q" with broad statements. That relates back to why I don't follow the idea that q = .7 could be boomy. Of implies a nice flat frequency response - and the location of the rolloff knee is a function of fs NOt q. How that translates to boominess when our hearing at LF is a function of frequency response is what I disagree with. Thus I think thermal modulation is a strong explanation for what is often heard on these uncontrolled listening tests.

I see your point, and I admit I haven't heard a modern speaker I'd call "boomy".

 

[Irvrobinson]

Your Velodyne is a dedicated and equalized sub. It surely has a lot of heat dissipation - it must also be a high q design by nature because it is extremely relatively small. If it were boomy sounding because of its q you would hear that. but equalization does correct q for a given SPL because q is related to frequency response.

You know, I've always wondered what goes on inside that sub, so I plugged it into my $25 Pro Power Meter just for grins. After an hour of listening to contemporary jazz with a lot of subwoofer action (Four Play), the meter read 0.14 KWhr. Pretty modest power consumption. That says nothing about peaks, of course, but I expected more.

 

[TLS Guy]

I'm sorry to be insistent, but I'm just not seeing it. I'm posting what I'm seeing, with the biggest differences highlighted in red, which indicate to me at least that the 20Hz tune is giving a bigger ripple. The dip between 50 and 100ms also looks lower in magnitude for the 15Hz tune, and I'd also note past 100ms I'm hesitant to say I see much of a difference at all.

The amplitude of the prolonged over hang of the impulse on the 15 Hz tuning is significantly greater. Neither has an impulse signature that is very encouraging.

 

[Steve81]

The amplitude of the prolonged over hang of the impulse on the 15 Hz tuning is significantly greater.

I can see flipping back and forth between the images that the subsequent "waves" of the overhang in the 15Hz tune are longer (although GranteedEV mentions, it should have a longer impulse).

Nonetheless, it's also apparent (to me at least) that the actual amplitude of the overhang is lower in 15Hz tune. Another example of this is comparing the dip centered around 75ms in the 15Hz tune versus the rise in the 20Hz response centered around 85ms; the dip in the 15Hz tune graph is clearly of lesser magnitude in spite of the fact that it is occurring before the rise on the 20Hz graph. Can you address this portion of my comments in greater detail?

Neither has an impulse signature that is very encouraging.

How does the sealed compare in this regard by your reckoning? How big of a real world difference will this make given operation in a typical untreated room? As mentioned, I haven't heard much yet in the comparison with the sealed mode that's made me want to ditch 15Hz tune for music, although my testing is far from complete.

 

[Steve81]

Ps: I'd also be happy to take this to pm if you don't care to clutter this thread up anymore.

 

[Steve81]

Neither has an impulse signature that is very encouraging.

After a bit of thought on the subject, I figured I'd form some semblance of a response to your statement.

As mentioned, on the face of it, clearly the sealed mode of the PB13U has the cleaner impulse response. However, I'm unsure whether that's enough to damn the PB13U to being an exercise in "lousy engineering" as you put it.

Here's another pair of "less than encouraging" impulse signatures:

http://www.data-bass.com/images/measurements/29/dts10 impulse.jpg

http://www.data-bass.com/images/measurements/50/N fv15hp 2 ports impulse.jpg

and the PB13U in 15Hz tune

http://www.data-bass.com/images/measurements/55/N pb13 15hz impulse.jpg

Taken on its own, I'd suppose you probably want nothing to do with any of these subs, but I'd question the wisdom of that approach. An impulse response really only tells you so much data; it seems to me at least that a waterfall gives you a better idea of where the actual problems in the time domain are.

The Danley:
http://www.data-bass.com/images/measurements/29/E dts10 waterfall.jpg

Well clearly you'd want to take action about the ringing here; Josh mentions aggressive EQ to deal with the issue in his notes, though I'd probably utilize a steep low pass filter and let the Danley do the heavy lifting below 50Hz. Either way, I'd not write it off just yet...

The Rythmik:

http://www.data-bass.com/images/measurements/50/B fv15hp 2 ports waterfall.jpg

Clearly a lot better looking than the Danley overall. Obviously there is some delayed energy below 30Hz, but in the bands above which are arguably far more critical for most musical content, decay seems quite adequate.

The PB13U:
http://www.data-bass.com/images/measurements/55/B pb13 15hz waterfall.jpg

20Hz on up, the decay seems again to be quite adequate. There is obviously ringing around the tuning point, although not anywhere near the severity of what the Danley brings to the table. I'd also question how significant of an issue this is for 99.99% of material, given the general lack of content in this frequency range (especially with music), and our ability to perceive such content.

 

[3db]

This debate is analogous to direct drive verses belt drive on turntables. Either way, if prpoerly designed, its going to sound good.