Hello, I've just left every experiment in DIY and bought one beautiful brand pair of speakers with dual chamber reflex:
Given my modest experience, it seems to me that reflex frequency is quite high, being speakers a bit boomy if not far from rear wall, and I would appreciate a suggestion to try lowering it. For my knowledge, a dual chamber reflex is made by a little chamber where is driver with a high frequency tuned vent opening in a big chamber with a low frequency tuned vent, opening out. So the first vent lets pass a larger band of frequency, after reduced by the second one.
My new loudspeakers seems to me exactly opposite: a large chamber with driver opening in a small chamber, so my questions are:
- how are the low frequencies filtered by the first low-pass vent able to pass through the second high-pass vent?
- where have I to work around to decrease the lower tuning frequency of cabinet, on the first or on the second vent?
Thank you very much.
Given my modest experience, it seems to me that reflex frequency is quite high, being speakers a bit boomy if not far from rear wall, and I would appreciate a suggestion to try lowering it. For my knowledge, a dual chamber reflex is made by a little chamber where is driver with a high frequency tuned vent opening in a big chamber with a low frequency tuned vent, opening out. So the first vent lets pass a larger band of frequency, after reduced by the second one.
My new loudspeakers seems to me exactly opposite: a large chamber with driver opening in a small chamber, so my questions are:
- how are the low frequencies filtered by the first low-pass vent able to pass through the second high-pass vent?
- where have I to work around to decrease the lower tuning frequency of cabinet, on the first or on the second vent?
Thank you very much.
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I was under the impression that both chambers in a dual chamber reflex enclosure are ported to the outside world, and that there is a connecting port in the partition between the primary chamber, where the woofer is located, and the secondary chamber.
All three ports have the same dimensions, but the primary chamber has twice the volume of the secondary chamber.
The primary chamber is tuned to f Hz, but at lower frequencies the two chambers act as one large chamber and the system is also tuned to f/2 Hz.
My information comes from 'Building Speaker Enclosures' by David Weems.
All three ports have the same dimensions, but the primary chamber has twice the volume of the secondary chamber.
The primary chamber is tuned to f Hz, but at lower frequencies the two chambers act as one large chamber and the system is also tuned to f/2 Hz.
My information comes from 'Building Speaker Enclosures' by David Weems.
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That's a double chamber reflex. A double bass reflex as described (a small driver chamber with an internal vent to a larger chamber which is vented to the room) is a variation popularised by Fostex.
This commercial job is similar to a hybrid of the two I did about a decade or so ago that reverses the DBR for loading purposes. If you want to tune it lower, you'll need to extend the vent to the outer room, same as any other vented box.
This commercial job is similar to a hybrid of the two I did about a decade or so ago that reverses the DBR for loading purposes. If you want to tune it lower, you'll need to extend the vent to the outer room, same as any other vented box.
hi - with David McBean's "hornresp" your case is called a "Double Bass Reflex" and assuming your speaker has the same inside construction as that cutaway picture, about a 3:1 ratio of the top to bottom chamber.
I think the lower /external vent, will have somewhat more effect on total system tuning when lengthened but the inner vent also has some influence.
You could try blocking some of the plastic vent's area which action should tune somewhat lower.
IF you had access (like being able to remove the plastic vent/difussor) then could add a bit of length to the bottom vent from "above" but I'd try lengthening the upper vent first - or placing some damping material across or "in" that vent.
The classic dual chamber bass reflex first (I think ??) described by George Augspurger, generally has a 2:1 chamber ratio, two external vents, and all three vents the same size and diameter.
Was there any literature with the speaker to show an impedance curve?
I think the lower /external vent, will have somewhat more effect on total system tuning when lengthened but the inner vent also has some influence.
You could try blocking some of the plastic vent's area which action should tune somewhat lower.
IF you had access (like being able to remove the plastic vent/difussor) then could add a bit of length to the bottom vent from "above" but I'd try lengthening the upper vent first - or placing some damping material across or "in" that vent.
The classic dual chamber bass reflex first (I think ??) described by George Augspurger, generally has a 2:1 chamber ratio, two external vents, and all three vents the same size and diameter.
Was there any literature with the speaker to show an impedance curve?
hornresp.exe certainly is a versatile tool when you get to know it.
@Galu, I'm surprised Weems doesn't mention the third option with the internally coupled box being sealed.
@Galu, I'm surprised Weems doesn't mention the third option with the internally coupled box being sealed.
He may well do in later revisions of his book, Allen.
Mine's an early edition!
And yes, he was describing a 'double chamber reflex'.
Mine's an early edition!
And yes, he was describing a 'double chamber reflex'.