Strange speaker design

[thewinelake.]

Can someone explain to me the logic behind the design of this bass speaker. Seems odd to me!

 

[davedotco]

It is a large reflex enclosure using 2 drivers and a single rectangular port.

*unknw*

 

[chebby]

Are these from that new hi-fi cafe you posted about recently?

Ah yes, they are ...

http://www.whathifi.com/forum/hi-fi/hifi-music-club

... you could ask the Living Voice people (or the dealer) who installed them.

 

[thewinelake.]

I was wondering why the port was that size and shape. I didn't really want to ask Kevin, but I could...

 

[nopiano]

I was wondering why the port was that size and shape. I didn't really want to ask Kevin, but I could...

I recall there are a couple of reliable tomes on loudspeakers design, that refer to established principles for various designs. The one I remember by Martin Colloms I see now costs £90 so maybe you can get one from a library. There may well be some more info on line too. The basics are here if that helps:-

https://en.m.wikipedia.org/wiki/Bass_reflex

You'd certainly need a big port to vent drivers of that size, however!

 

[steve_1979]

slot shaped rectangle ones that are the width of the enclosure are quite common.

 

[steve_1979]

I was wondering why the port was that size and shape.

Ports come in various shapes. Rectangle ones like that are quite rare but slot shaped rectangle ones that are the width of the enclosure are quite common.

So long as the dimensions of the port have been calculated correctly relative to the driver and enclosure, the shape of the port isn't hugely important. Round and flared ports do tend to have less turbulence than square or slot ones though.

 

[davedotco]

For those interested the big Living Voice systems were originally based on the Vitavox Thunderbolt, a compact portable PA system from the the 1970s.

Early versions featured the superb Vitavox S2 compression driver, one of the finest such units ever produced.

Take a look here.

http://website.lineone.net/~empson/featuring_Vitavox.html

 

[thewinelake.]

That one with the pics looks like a kind of transmission line design. Having a ruddy great port in the middle seems (on a intuitive level) quite self-defeating!

I guess one needs to try these things out to get a feel for them. My underfloor subwoofers have stopped working - I think the speaker cones have probably been eaten by mice/rats - so I can't talk....

I'm really hoping that they get some acoustic mushrooms (or equivalent) to sort out the acoustics in that room, as the frequency response is obviously all over the place. I was also almost inclined to ask if they'd got the phasing wrong as the stereo imaging was non-existent, but manners got the better of me, and they're all rather exhausted from the sheer effort of getting the whole project off the ground, so getting it to sound good is going to have to wait. Having said that, lots of people who should know better (?!) seem to be saying that it sounds great as it is - I reckon that's a case of listening with their eyes ;-)

 

[chebby]

That one with the pics looks like a kind of transmission line design. Having a ruddy great port in the middle seems (on a intuitive level) quite self-defeating!

All I can see is the transmissiom line, the driver and the crossover/amp.

(Unless you are referring to the cutaway as a port.)

 

[thewinelake.]

My second sentence refers to the Living Voice speakers.

Obviously they do know what they're doing, but it just struck me as odd!

 

[steve_1979]

That one with the pics looks like a kind of transmission line design.

It's not a transmission line but it is an unusually long port that looks like one.

Here's a more typical example of a slotted port enclosure.

Here are some hifi speakers with slotted ports (Acoustic Energy 101).