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In the Forum: Audio Discussions
In the Thread: Macondo’s MiniMe or about Pilot Acoustic Systems
Post Subject: How to teach the port do not sound like a portPosted by haralanov on: 9/18/2008
Principally there are many many theories and papers about ports and how they must be calculated/constructed/placed/used. But none of these theories explains the relation of port design to the SOUND.  That’s the reason why so many engineers get so horrible results with their speakers. We do not make ports and speakers – we build sound. That’s why everything should be tried in practice and the designer should listen to the results he/she achieves.

I personally very much hate ported designs, but it is not impossible to eliminate the nasty “port sound” and use the benefits of bassreflexes in terms of dynamic extension. In my experience the port sounds better if it uses side wall as an extension along it’s  length. I do not know what the real reason is but it sounds less ported this way.  If the port is placed in the middle of the baffle you get more of this damn “ported” sound. If the port does not have flaring, it sounds too aggressive and with some kind of strain, no matter how loud you listen music IMO. Something you should consider to be mandatory and of great importance for sound is to FILL the ports with natural wool. It suppress the midrange resonances inside the port and restricts the leakage of sound at higher frequencies. Here is a picture of my last design using big flare at the both ends of the port (removed the wool intentionally):

port before wool filling.jpg



LBJ, your theory is right, but I don’t think you get my idea of using ports. The method I described above consider using the port’s output, but only FRACTION of this output, just below the point where the port sound like a separate source of blurred bass, screaming “BUU, BUUU, Here I am, I’m a port, look at ME”….

In the graphic below there shown 3 different bass loadings using identical driver. The blue line represent excursion of the driver in sealed enclosure, the gray one represents the standard port loading, while the yellow line represent my idea (port with reduced efficiency) due to lowered output caused by internal port damping. My golden rule is with lowering the frequency the driver’s excursion must not be lowered at any point. That is the point where the “Port sound” takes over, polluting the Music:

port vs filledport vs closedbox.jpg

 Romy the Cat wrote:
Of cause we would like to drive the port’s resonance below the driver/enclosure resonance to get more bass out of the situation, without use of ultra low Fs driver and increasing the size of the box. Or cause we would have a sever driver reactance when the resonances “meet”. Aren’t they all the ideas of port use and isn’t it how it works in all bass reflex loudspeakers. I was under presumption that by embracing the horn idea we are by default let the amplification, filtration and other thighs to deal with driver “comforting” during the cone-flapping… If we keep the Fb above the Fs then why do we need to a port to begin with?

The tuning above driver Fs is used by the people in a very wrong way – they want to gain some extra bass of their drivers without overloading them. If some filling inside the port is used it stops acting like a port and this is the only way dealing with them. If this rule is applied there is no problem using very low port tuning.

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