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So closed box speakers are pretty much a dead?

Putter

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NHT , KLH, Yamaha and some Sony's are examples. One alternative which give the advantages of a ported speaker in terms of efficiency and a lower 3db response with the advantages of a sealed design avoiding midrange leakage and port resonances are passive radiators of which Def Tech is best known but there are many others.
 

echopraxia

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Are there any other inherent disadvantages to closed speakers other than SPL efficiency?

Given that even some of the most highly regarded speaker companies in the world still sell high-end speakers with audible port-related issues, it's certainly plausible (at least) that modern closed designs may have notable benefits (if only due to the different way they interact with room placement).
 
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Koeitje

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Are there any other inherent disadvantages to closed speakers other than SPL efficiency?

Given that even some of the most highly regarded speaker companies in the world still sell high-end speakers with audible port-related issues, it's certainly plausible (at least) that modern closed designs may have notable benefits (if only due to the different way they interact with room placement).
You also need bigger enclosures and woofers to reach the same low end.
 

bigx5murf

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http://linkwitzlab.com/frontiers.htm

" I am not certain what happens in the range below 100 Hz and I have strong suspicions that this is the region where delay distortion is audible. It is also the region where delay really accumulates via vented and bandpass woofers, and the great numbers of dc blocking capacitors in the signal chain from microphone to speaker terminal. "

From my interpretation, a sealed box's benefits are most noticeable at under 100Hz. Which might explain why lots of modern subwoofers are still available in sealed designs.
 
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Koeitje

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http://linkwitzlab.com/frontiers.htm

" I am not certain what happens in the range below 100 Hz and I have strong suspicions that this is the region where delay distortion is audible. It is also the region where delay really accumulates via vented and bandpass woofers, and the great numbers of dc blocking capacitors in the signal chain from microphone to speaker terminal. "

From my interpretation, a sealed box's benefits are most noticeable at under 100Hz. Which might explain why lots of modern subwoofers are still available in sealed designs.
Most reflex speakers have sealed sections for their midrange (if they have a seperate woofer for the low end) and tweeters. Because you don't need the reflex port for the extension there.
 

gene_stl

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Passive radiators have resonances just like ports. They don't huff like some (not all) ports.
All ported enclosures have bass overhang. At least one cycle worth and usually more. With amplifier watts kind of as cheap as computer memory , hard drive space, and bandwidth not to mention DSP and other wonderful methods of EQ available (also almost free) why would anyone use anything other than a sealed box. (acoustic suspension or infinite baffle)
The fact that they may be "out of style" for the moment, does not mean they are dead.
 
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echopraxia

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http://linkwitzlab.com/frontiers.htm

" I am not certain what happens in the range below 100 Hz and I have strong suspicions that this is the region where delay distortion is audible. It is also the region where delay really accumulates via vented and bandpass woofers, and the great numbers of dc blocking capacitors in the signal chain from microphone to speaker terminal. "

From my interpretation, a sealed box's benefits are most noticeable at under 100Hz. Which might explain why lots of modern subwoofers are still available in sealed designs.

And ironically, it seems the primary reason for ports (or passive radiators) is to increase efficiency/SPL in these lower bass frequencies without increasing cabinet size — which if you’re right, is precisely the frequencies where the distortion will be most audible.
 

sfdoddsy

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Depending on the volume you like to listen, sealed subs make sense because you can EQ them to give real depth, whereas ported subs go a bit crazy below the port frequency.
 

DownUnderGazza

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Sealed subs all the way!
Apply a Linkwitz transform to both blend with room gain (@12dB/octave) and lower the Qtc towards 0.5 for critically damped (most accurate time profile) response. Er, provided the sub is designed to handle it of course.
Check out the excellent research papers at MangerAudio.com
 

Juhazi

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Magicos are sealed too https://www.magicoaudio.com/

ebc7953cc9c99fa9d012d0599eaf195d.jpg


Many subwoofers too
https://www.svsound.com/blogs/svs/75367747-sealed-vs-ported
 
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Koeitje

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Turns out they are not dead, just very expensive :D.
 

Wombat

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Consumers are not so discerning re the sealed vs ported thing. Side-by-side the BR seems to give more LF oomph for size and money. A no-brainer for them.

Meanwhile on forums, the(minority) audio intelligentsia are still trying to work this out.
Don't%20tell%20anyone.gif
 

617

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Some graphs of a very typical 8" woofer. Sealed is blue, vented is green.

First graph shows the frequency response at low levels. The sealed box produces less bass from about 15hz on up.
TF.png


Next is excursion at 30W - the sealed woofer can handle that 30W no problem, but at low frequencies the vented woofer is past its xmax. Not a good thing.

excursion.png


Next, the maximum SPL:

max SPL.png

The sealed woofer simply does not have the kind of output the vented one has, even at 50-100hz it is quieter. Note that equalization of the sealed box doesn't help much - no matter how much you boost the signal (via PEQ or Linkwitz transform), the woofer cannot actually play louder than this in a sealed box. Sealed subwoofers can have a bass boost because they generally have a lot more output capability than is needed, so throwing away ~10db of bass may not be an issue in a subwoofer that has 18mm xmax and can handle 750W.

In this case, the vented box is 1.5 cubic feet, and the vented box is .8 cubic feet. So, the sealed box is about half as big. To put that in perspective, the vented box would be a cube about 15 1/4" to a side, and the sealed box a cube 11" to a side.

Passive radiators are basically equivalent to vented systems, although they are preferable for other reasons.


Finally group delay:
GD.png

Group delay is the result of the high pass behavior of the driver itself, but due to the steeper roll off of the vented (or PR) system we have more at higher frequencies, in this case, 20ms at 30hz. I am not aware of a consensus on audibility of LF group delay, but I would argue steady state response is much more important below the schroeder F of your room (100-200 hz). I believe zero group delay could be achieved with special digital filters or, alternately, a woofer that can produce 0hz (they exist, sort of.)

Note that vented designs are quite flexible, however, and if you lower the tuning frequency you can effectively lower the group delay.
See this article for an interesting discussion on manipulating the size of vented boxes:
http://speakerdesignworks.com/Sealed_v_Vented_2.html

So are sealed designs better? They have a lot of advantages, but for a commercial speaker used without a subwoofer, the huge (up to 10db) advantage in bass output from a vented design generally outweighs the costs of increased LF group delay and cabinet size. Consequently, most drivers today are really optimized for vented enclosures, with very few (Scanspeak 8535, Dayton RS270) really doing well in a sealed box.
 
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Frank Dernie

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The 8C’s are not sealed, they have side vents, with clever engineering to make the rear-firing bass cardioid.
The side vents are connected to the mid range enclosure and are the mechanism (or part of) that creates the mid cardioid radiation.
Bass is sealed but I must say since they use DSP correction which can't work properly to lower bass in a vented enclosure the Kii, D&D and Grimm are hardly similar to any passive closed box...
 

dc655321

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Good post, @617.
For reference, here is what may be possible at normal listening levels (< 85dB SPL) using a so-called Linkwitz Transform (afaict, he did not invent this) on a 10" Dayton RSS265-HF in a 30L (1 cu.ft) sealed enclosure. I moved the -3dB cutoff down to 20Hz and shifted the Q to 1/sqrt(2).

Python:
import numpy as np
import scipy.signal as sig
import matplotlib.pyplot as plt


# Exploring a so-called Linkwitz Transform filter for subwoofer response tailoring
fs = 44100
fn = fs//2 # Nyquist
fc = 36.95 # corner freq of closed-box system in Hz
Q = 0.803 # Q of close-box system (aka Q_tc)

b = [1,0,0] # zeros
a = [1, (2*np.pi*fc/Q), (2*np.pi*fc)**2] # poles

w = np.linspace(5, 2*np.pi*fn, num=fn+1, endpoint=True)

w, Ho = sig.freqs(b, a, worN=w)
plt.figure()
plt.semilogx(w/(2*np.pi), 20*np.log10(np.abs(Ho)), label='Original System')
#plt.xlim([1, 150])

fc1 = 20 # desired corner frequency of close-box system in Hz
Q1 = 1/np.sqrt(2) # desired Q of closed-box system # np.euler_gamma #
lt_b = a
lt_a = [1, (2*np.pi*fc1/Q1), (2*np.pi*fc1)**2]
w1, H1 = sig.freqs(lt_b, lt_a, worN=w)
plt.semilogx(w1/(2*np.pi), 20*np.log10(np.abs(H1)), label='LT Filter')

bt = np.convolve(b, lt_b)
at = np.convolve(a, lt_a)
wt, Ht = sig.freqs(bt, at, worN=w)
plt.semilogx(wt/(2*np.pi), 20*np.log10(np.abs(Ht)), label='LT + Original')

plt.axhline(-3, color='grey', linestyle='--')
plt.axvline(20, color='grey', linestyle='--')
plt.xlabel('Freq [Hz]')

plt.legend(loc='lower right')
plt.ylim([-30, np.max(20*np.log10(np.abs(H1)))+2])
plt.xlim([5, 1200])
plt.grid(b=True, which='both', axis='both')
lt_rs265.png
 

Soniclife

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First graph shows the frequency response at low levels. The sealed box produces less bass from about 15hz on up.
index.php
I think a lot of the sealed appreciation comes from how those two curves interact with real rooms, particularly small rooms with solid walls. I've noticed I often end up using DSP on ported speakers that isn't that far from what sealed would do. Plus you can tune the bass a bit with distance to wall, where they like the wall support more than ports do. Basically I'm convinced it's at least 90% frequency response that people respond to between the systems, as with most off hifi.
 
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Ron Texas

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A very popular setup is a pair of reflex mini monitors rolled off starting at 100 hz with the lows handled by a sealed sub. This minimizes port output.
 

vin63

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I have own lots of ported speakers, but last year i bought my first sealed speaker. A ATC scm19, i really like it, it makes me want to save up for the scm40. I added a sealed subwoofer to get the bass i wanted. I have own some really good ported speakers and some bad. I think a good speaker manufacture can make either design work.
 
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