article about double chamber speaker enclosure - Page 3

kelticwizard · 13th November 2002, 01:13 AM

Hari:

Well, I must admit that you have me scratching my head over that one, LOL. But anyway, that is the right way to test it-first wire them one way, then the other, and go with the way that gives the greater bass. So you must be doing something right.

Dustin Haug · 13th November 2002, 01:50 AM

Quote:

One little question - in a 6th order bp if the ports of the two chambers are placed on the same side of the enclosure will there be any cancellation of sounds coming out of them?

I have a sixth order bandpass sub with all the ports downfiring and I can say I've never noticed any cancellations, so I seriously doubt you'll run into any problems.

Opie · 6th December 2002, 04:34 AM

kelticwizard,

You wrote:

"Suppose a 12 inch speaker in a 2 cubic foot box is tuned to 40 Hz. In a double chamber reflex system, it would be tuned to 40 Hz AND 80 Hz. And the excursion advantages would apply to both frequencies."

My question is would the larger chamber be tuned to 40hz or would the smaller one?

thanks in advance,

Opie

kelticwizard · 6th December 2002, 04:46 AM

Opie:

I think if you check my posts of October 28, you will see that the entire enclosure is tuned to 40 Hz. That is the top volume and the bottom volume added together.

Please check the posts, and get back to me if there is any question.

Forget completely about tuning the two volumes separately. Put it entirely out of your mind. It doesn't work like that at all.

Weems said that at low frequencies, the small upper chamber joins the lower chamber to form one unit. At upper bass frequencies, though, it separates out and becomes a small speaker within itself. Hence, the two tunings.

Something like that.

I'll do a run-through with you tomorrow if the idea is not clear yet. Why not? We're snowed in under 10 inches of snow here in Connecticut-not that such a condition isn't something you guys in Wisconsin aren't well familiar with!

Wcoil · 6th December 2002, 06:53 AM

Hello Kelticwizard,
when you calculate a double chamber reflex, you can´t calculate the whole box for two vents and then put one in each chamber. That will go horribly wrong. You calculate for the whole volume and one vent. Then you put in two more of the same size. One in each chamber and one between them. You haven´t really built one have you? I have built at least 6 pairs of different configurations. The one that works best, has chambers of the same size and only one port facing outward form the chamber without the bass driver.

kelticwizard · 6th December 2002, 07:40 AM

Wcoil:

Nope, haven't built one yet, just read a couple of articles by Weems. That seems to be the way he advises.

Since you have built these, by all means let us know.

claudio · 8th December 2002, 02:56 PM

Well, things are getting confused here!

Kelticwizard did you find the original article? Would be helpfull to read it so we can come to just one interpretation.

Wcoil:

You said: "The one that works best, has chambers of the same size and only one port facing outward form the chamber without the bass driver."
But using just 2 ports instead of 3, is a different system, it's not a double chamber , I think.

Regards

Claudio

Wcoil · 9th December 2002, 08:50 AM

Hey Claudio, it is a doble chamber system. The upper chamber has got the bass driver and a vent connected to a chamber below. That chamber is in contact with the outside through a vent.
You calculate a normal bassreflex box. Add 30-40% volume. Calculate a vent for the total volume of the both chambers together. Use Fb= Fs or a bit lower. Try with both vents of the same size. Sometimes it´s wise to have a larger diameter vent on the inside. Then you have to recalculate the length of that one. Once again using the total volume. Hope it makes it clear.
This type of double chamber speaker has less ripple in the upper bass and sounds more like a TL.

claudio · 9th December 2002, 01:16 PM

Ok Wcoil , I understood your design method.
Now, since you have experience on double chamber speakers, let me ask you :

where do you position the inside vent? In the middle of the 2 chambers, or all the way inside the woofer chamber?

In your 2 ports system, how is the cone excursion compared to the Weems' one?

Do you still have the DIP in the frequency response?

Do you have some measured responses?

Regards

Claudio

Wcoil · 9th December 2002, 03:59 PM

Claudio, it doesn´t matter much where you put the vent,as long as it isn´t too near the bass driver. I have made measurements, but only manually. So I have no grafs I can send you. With this typ of speaker there are no dip. Other systems with two chambers that I have made had dips.

6th December 2002, 04:34 AM	#23
Opie diyAudio Member Join Date: Oct 2001 Location: UW Stevens Point Campus	tuning kelticwizard, You wrote: "Suppose a 12 inch speaker in a 2 cubic foot box is tuned to 40 Hz. In a double chamber reflex system, it would be tuned to 40 Hz AND 80 Hz. And the excursion advantages would apply to both frequencies." My question is would the larger chamber be tuned to 40hz or would the smaller one? thanks in advance, Opie

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13th November 2002, 01:13 AM	#21
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	Hari: Well, I must admit that you have me scratching my head over that one, LOL. But anyway, that is the right way to test it-first wire them one way, then the other, and go with the way that gives the greater bass. So you must be doing something right.

6th December 2002, 04:46 AM	#24
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	Opie: I think if you check my posts of October 28, you will see that the entire enclosure is tuned to 40 Hz. That is the top volume and the bottom volume added together. Please check the posts, and get back to me if there is any question. Forget completely about tuning the two volumes separately. Put it entirely out of your mind. It doesn't work like that at all. Weems said that at low frequencies, the small upper chamber joins the lower chamber to form one unit. At upper bass frequencies, though, it separates out and becomes a small speaker within itself. Hence, the two tunings. Something like that. I'll do a run-through with you tomorrow if the idea is not clear yet. Why not? We're snowed in under 10 inches of snow here in Connecticut-not that such a condition isn't something you guys in Wisconsin aren't well familiar with!

6th December 2002, 06:53 AM	#25
Wcoil diyAudio Member Join Date: Dec 2002 Location: Sweden	Hello Kelticwizard, when you calculate a double chamber reflex, you can´t calculate the whole box for two vents and then put one in each chamber. That will go horribly wrong. You calculate for the whole volume and one vent. Then you put in two more of the same size. One in each chamber and one between them. You haven´t really built one have you? I have built at least 6 pairs of different configurations. The one that works best, has chambers of the same size and only one port facing outward form the chamber without the bass driver.

6th December 2002, 07:40 AM	#26
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	Wcoil: Nope, haven't built one yet, just read a couple of articles by Weems. That seems to be the way he advises. Since you have built these, by all means let us know.

8th December 2002, 02:56 PM	#27
claudio diyAudio Member Join Date: Feb 2002 Location: Italy	Well, things are getting confused here! Kelticwizard did you find the original article? Would be helpfull to read it so we can come to just one interpretation. Wcoil: You said: "The one that works best, has chambers of the same size and only one port facing outward form the chamber without the bass driver." But using just 2 ports instead of 3, is a different system, it's not a double chamber , I think. Regards Claudio

9th December 2002, 08:50 AM	#28
Wcoil diyAudio Member Join Date: Dec 2002 Location: Sweden	Hey Claudio, it is a doble chamber system. The upper chamber has got the bass driver and a vent connected to a chamber below. That chamber is in contact with the outside through a vent. You calculate a normal bassreflex box. Add 30-40% volume. Calculate a vent for the total volume of the both chambers together. Use Fb= Fs or a bit lower. Try with both vents of the same size. Sometimes it´s wise to have a larger diameter vent on the inside. Then you have to recalculate the length of that one. Once again using the total volume. Hope it makes it clear. This type of double chamber speaker has less ripple in the upper bass and sounds more like a TL.

9th December 2002, 01:16 PM	#29
claudio diyAudio Member Join Date: Feb 2002 Location: Italy	Ok Wcoil , I understood your design method. Now, since you have experience on double chamber speakers, let me ask you : where do you position the inside vent? In the middle of the 2 chambers, or all the way inside the woofer chamber? In your 2 ports system, how is the cone excursion compared to the Weems' one? Do you still have the DIP in the frequency response? Do you have some measured responses? Regards Claudio

9th December 2002, 03:59 PM	#30
Wcoil diyAudio Member Join Date: Dec 2002 Location: Sweden	Claudio, it doesn´t matter much where you put the vent,as long as it isn´t too near the bass driver. I have made measurements, but only manually. So I have no grafs I can send you. With this typ of speaker there are no dip. Other systems with two chambers that I have made had dips.

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