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Why Are Ported Speakers the Dominant Design?

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Ron Texas

Ron Texas

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Thread Starter #121
@watchnerd you are focusing on "ludicrous" from a different perspective than I have. It's true that double binding posts are visible, and what's inside the box is not, but photos can show what's inside the box. That buyers believe dual binding posts add value is ludicrous.

I find it ludicrous that a $600 (or more) speaker has a toy crossover whether it's visible or not. No wonder the DIY guys are replacing them.
 

watchnerd

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@watchnerd you are focusing on "ludicrous" from a different perspective than I have. It's true that double binding posts are visible, and what's inside the box is not, but photos can show what's inside the box. That buyers believe dual binding posts add value is ludicrous.

I find it ludicrous that a $600 (or more) speaker has a toy crossover whether it's visible or not. No wonder the DIY guys are replacing them.
Well, a lot of the DIY crossover mods are also pretty ludicrous in terms of actual sonic impact.

See: Audiophile Capacitors snake oil
 
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Ron Texas

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Thread Starter #123
Well, a lot of the DIY crossover mods are also pretty ludicrous in terms of actual sonic impact.

See: Audiophile Capacitors snake oil
That doesn't make them all bad. Why are you putting a negative spin on everything I write this morning? I'm not running for office, so be nice.
 

digitalfrost

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I think using a sub and rolling off a ported speaker, say down 6 db @ 80 hz with a 24 db/octave filter should help as it reduces the output of the port. Measured FR in my room is the same for the port plugged and with -6db @ 90 hz unplugged.
I run my KEF LS50 with DIY subwoofers. I tested various crossover frequencies with the LS50 ports plugged and open. In the end, I preffered the LS50 with the ports open, despite using a highpass. I cross them over at 100hz with 24db/oct, pretty close to your 6dB down at 80hz. LS50 are tuned to 55-60hz port resonance.

Also, the Wilson Audio Watt/Puppy uses bass reflex for the satellites. I understand Wilson Audio might not be the best argument when it comes to a scientific perspective, but I think limiting excursion for the midrange unit, especially when supported by a crossover that removes the negatives of bass relfex below the tuning frequency could be benefitial.

That said. Bass reflex is a cheap - probably the cheapest - solution to a problem that in 2019 you really shouldn't have anymore. Getting good bass can be solved in a lot of ways, it's not that expensive either, at least from an enthusiast perspective. Good bass will always be - has to be - active. If you're using passive speakers for your bass needs, you either have to get lucky with the speaker/room/placement interaction, or you're using DRC.

Active bass + DRC is the goldilocks solution. I remember a signature that read in some forum years ago:

"What's the price of a hole in the box?"

- "Good sound."

It is not true all the time, but I like the sentiment.
 
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@pozz
The displacement requirement makes going with sealed subwoofers questionable in a wide variety of scenarios. It might also ruin a good number of small bookshelves with woofers smaller than 7 inches.
As for the main speaker with a sub, you could forgo the port if the drivers were capable of meeting the subwoofers if sealed, and this would greatly simplify the design of the main loudspeaker. I don't see too much harm in a small, vented 3-way bookshelf type, which would be more likely to have a short vent.
 

Wombat

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Right.

And there is at least a chunk of the industry that earns a living catering to that obsession.

I don't have a problem with people buying audio jewelry from McIntosh, any more than I have a problem buying real jewelry from Cartier.

They're both fashion purchases designed to display status.

Even "engineering oriented" speaker makers like Revel offer bi-wire posts:




I don't think it's ludicrous of them to offer that if they think it increases sales with their target market.

Even if they know it's no more useful than VU meters on a McIntosh amp.....it's fashion.
Bi-wire is pretty useless but bi-amp capable is handy.
 

Putter

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I'll put forth the proposition that the easiest way to put together a high quality full range or nearly full range system on a budget is to match a 2 way acoustic suspension speaker with a woofer no larger than 6 or 7 inches and match it with a sub(s) ported or acoustic suspension, the former being more economical albeit at the expense of some loss of transient response.

This is not an original thought as a previous poster references Welti (of Harman and multisubs) as advocating this approach.
 

Cosmik

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...match it with a sub(s) ported or acoustic suspension, the former being more economical albeit at the expense of some loss of transient response.
But if ported had never been invented, you wouldn't even worry about it. Audiophile budgets are usually in the thousands of dollars, often tens of thousands. Speaker drivers start in the tens of dollars and might stretch to hundreds. MDF comes in huge sheets for $40. I don't see why it's necessary for the serious audiophile to be economical to the point of objectively damaging the signal. If they're not serious, and not worried about the "loss of transient response", why are they even bothering? There will always be a need for rumble boxes for a certain type of home theatre enthusiast, so bass reflex has its place. But why in serious hi-fi?

I think the OP refers to the way supposedly serious manufacturers use ports without thinking. I saw in one forum where a manufacturer (can't remember which) was responding to criticism they were using bass reflex and they responded with "Why do you think we do it? Why do you think all the other manufacturers use bass reflex, too? ". But they didn't answer their own question!
 

KSTR

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A ported speaker cannot be considered time invariant....
You clearly have not understood the concept. *ANY* speaker which is operated within its limits is only weakly nonlinear and almost perfectly time-invariant, so very close to a true LTI system. This has nothing to do with the underlying principle of construction: open-baffle, sealed, ported, transmission line, horn, ...
 

Cosmik

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You clearly have not understood the concept. *ANY* speaker which is operated within its limits is only weakly nonlinear and almost perfectly time-invariant, so very close to a true LTI system. This has nothing to do with the underlying principle of construction: open-baffle, sealed, ported, transmission line, horn, ...
I never mentioned linearity - it's basically linear.

Are you claiming that the driver chained with a resonator - that has to go through a delayed undershoot before it becomes in-phase - is minimum phase?
 

KSTR

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Are you claiming that the driver chained with a resonator - that has to go through a delayed undershoot before it becomes in-phase - is minimum phase?
Yes, definitely. If you calculate the minimum phase version of a magnitude response (via Hilbert Transform) and compare the phase to the input data, it is exactly the same, empirical proof. Analytical proofs exist as well.
Most any mechanical/electrical system is minimum phase anyway -- but of course combined systems with minimum phase crossovers don't have a minimum phase total.
Sidenote: even reflections are minimum phase by the way. The mag/phase frequency response of a reflection is a comb-filter and if you duplicate this comb-filter with a bunch of cascaded notch filters (which sure are minimum phase) you get the exact same doublet in the impulse response. If the notches are not infinitely deep (== there is an amplitude difference between original and reflected sound), an inverting filter can be made and the response can be rectified...
 

Cosmik

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Yes, definitely. If you calculate the minimum phase version of a magnitude response (via Hilbert Transform) and compare the phase to the input data, it is exactly the same, empirical proof. Analytical proofs exist as well.
Most any mechanical/electrical system is minimum phase anyway -- but of course combined systems with minimum phase crossovers don't have a minimum phase total.
Sidenote: even reflections are minimum phase by the way. The mag/phase frequency response of a reflection is a comb-filter and if you duplicate this comb-filter with a bunch of cascaded notch filters (which sure are minimum phase) you get the exact same doublet in the impulse response. If the notches are not infinitely deep (== there is an amplitude difference between original and reflected sound), an inverting filter can be made and the response can be rectified...
You're wrong.
...if minimum-phase LTI systems are connected in series, the overall system remains minimum phase. The similar property does not hold in the case of systems whose responses are added
In the case of a bass reflex speaker we are not merely cascading responses, we are adding them - we hear the speaker driver and the output of the port. Intuitively, we can't correct the sum of the two (make it into a single transient impulse) because the port 'echoes' whatever we do with the cone - possibly with a larger output. Even with a complex model, we can't invert the system because the result is unstable, needing to provide larger and larger corrections.
 

KSTR

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Oh come on, you're not going to lecture someone like me about linear systems and loudspeaker theory. As they say, you're entitled to your personal opinions but you can't have your own facts...
I will stop here and not engage in endless discussions with you, given your typical style of using Eristic Dialectic.
 

Cosmik

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Oh come on, you're not going to lecture someone like me about linear systems and loudspeaker theory. As they say, you're entitled to your personal opinions but you can't have your own facts...
I will stop here and not engage in endless discussions with you, given your typical style of using Eristic Dialectic.
I'm not even slightly interested in who you are. I'm only interested in ideas.
 

Wombat

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Ideas, postulations, unsubstantiated opinions, posits or whimsy? It can be hard to tell at times.
Thinking.gif
 

anmpr1

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Some historical remarks..

- In 1954 Villchur introduced closed box (acoustic suspension) which gained popularity in slowly growing hifi market. Response 50-10 000Hz. This cult has revived best in Britain (BBC heritage).

- in '70s electrostatic panel speakers didn't get much popularity.
The popularity of the acoustic suspension speaker was due to size restrictions. Hitherto, any reasonable semblance of bass response required a largish box, or an even larger horn-type enclosure. The trade-off was that the acoustic suspension speaker was not very sensitive, requiring more power than the 'average' amplifier of the day could provide. Bob Carver's Phase Linear company was one of the first to provide suitable domestic oriented power amplification that could make the AR3 and it's ilk actually 'come alive'. Things quickly progressed, and by the late '70s watts were so cheap you could buy all in one receivers from any of the major Japanese brands sporting 150 watts/ch, and more. By then, however, the acoustic suspension engine was almost a thing of the past--you'd never find the Maxell 'blown away' guy sitting in front of an AR3a.

The earliest US electrostatic speakers were often smallish box hybrids (sealed woofers) or separate, add-on electrostatic tweeter panels, such as the Janszen. KLH and Infinity had a go at it--both were monsters and costly. Quad was more or less reasonable, price-wise, but never had much of a US presence. Bud Fried imported them for a while, however I've no idea how many he sold. Really, they just didn't fit the American listening style. Gordon Holt complained about their lack of power handling; Peter Aczel owned them several times, said they were excellent, but only for low SPL, single listener use (due to beaming). In order to overcome some of their limitations, Mark Levinson stacked them, added a monstrous subwoofer and tweako tweeter, all in the hopes of pushing out some decent SPL. Then he raised the price to oil sheik levels, and shortly thereafter went out of business.

I think the company that did most to popularize electrostatics was Jim Strickland's Acoustat organization. Acoustats were relatively affordable, relatively indestructable, required a relatively powerful amplifier, but offered relatively pleasant and relatively loud sound. My guess is that Acoustat sold more electrostatic speakers than anyone. But even they couldn't make a go of it, lasting a little while longer as a subsidiary of David Hafler's company, subsequently absorbed by car speaker outfit Rockford. I heard the brand was later sold to some Italians (that is, a company in Italy) who sold it to an outfit in Guangzhou China.
 
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Ron Texas

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Thread Starter #139
I think the OP refers to the way supposedly serious manufacturers use ports without thinking. I saw in one forum where a manufacturer (can't remember which) was responding to criticism they were using bass reflex and they responded with "Why do you think we do it? Why do you think all the other manufacturers use bass reflex, too? ". But they didn't answer their own question!
Not exactly, but I wonder why there is a scarcity of other designs at all price points and cabinet sizes especially considering how many speaker manufacturers are out there.
 
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