Dual chamber ported sub?

[elambert]

I recently completed a sub using a Quatro 15 (ported tuned around 19hz) and it sounds really good however I have been bitten by this diy bug big time and feel I could do better on the second cabinet than the first one. So I have decided to build a second one for the same driver.

In researching all of the different design types, I found this (http://www.diysubwoofers.org/prt/dual_chamber.htm) but I hadn't seen any projects utilizing this type of design and was wondering about the actual sound quality of such a beast.

I like the really low tuning of my current box however on some movies and quite often in computer gaming, the driver is being pushed too far.

Anyone every used this type of box design? Input?

[Madmike2]

Pushed too far? Over excursion i am assuming. I dont see how if you tuned it to 19 hz . No game i know generates anything near that frequency.

And that box is a Dual chamber tri tuned. The two enclosures are tuned with ports tuning them and the back wave output. Very steep roll off Bandpass. You think your sub is getting beat up now ? Build that and see an inanimate object get tortured . Its also overly peaky with out something to EQ the peaks out.

[kelticwizard]

Claudio Negro built one, and goes into detail on it on his website, available in English version. He seems pleased iwth it:
http://paginas.terra.com.br/educacao...negro/english/

Here is a discussion on the box:
article about double chamber speaker enclosure

My guess is that if your driver seems to be pushed too far, see if low frequencies below 19 Hz are getting to the speaker somehow. Reflex designs, whether single or double chamber, have a sharp excursion rise once you go below the box tuning frequency.

[elambert]

Thanks for the replies, that thread has me doing some thinking. It has been suggested that it isn't the real low notes that are overdriving the sub but more of frequencies in the 30 - 40 hz range. I went back into WinISD and re-did the calcs and there is definitely a peak above xmax in that range.... don't know how I missed that the first time.

Well I'll chalk this up to experience and build another box. I'm just going to have to decide what setup.

[Madmike2]

Originally posted by elambert
Thanks for the replies, that thread has me doing some thinking. It has been suggested that it isn't the real low notes that are overdriving the sub but more of frequencies in the 30 - 40 hz range. I went back into WinISD and re-did the calcs and there is definitely a peak above xmax in that range.... don't know how I missed that the first time.

Well I'll chalk this up to experience and build another box. I'm just going to have to decide what setup.

Do yourself a favour and stay away from that design though. Its better for LF SPL and thats about it unless you build a BIG one and use it in a club with about 10 more.

[elambert]

Madmike, building big isn't a problem. Single and have a house to myself...

You said in an earlier post that it is bandpass with a steep rolloff. From the articles I have read, it is not that way but just basically adds a second tuning point 1 octave higher than where the box is tuned to. In my case the box is currently tuned to 19 hz which would mean that the second tuning frequency would be around 38hz which is about where the driver is having excursion problems.

In modeling some ideas in WinISD, with this box type it seems I could actually tune it lower than with a single reflex system because of that second tuning point helping to control over excursion.

If I was using a better driver with more X-max I wouldn't have this problem however funds are limited so I can afford the wood, just not another driver.

Btw, I wouldn't mind building a bigger box as I would like to replace the quatro in the future and have this box be "convertible" to change the inner volumes to match.

Ethan

[richie00boy]

Build the double chamber box, it is ideal for what you want. It is NOT a bandpass design nor does it have sharper roll off than a normal vented box. I think Madmike2 is getting confused with a bandpass box where the driver is actually hidden away inside a box within a box.

The only issue is that at the higher tuning frequency you get a slight dip in output. This can take a bit of punch out of the sound, but I think in your case with such low tuning you will be OK. Punch is usually 80-100 Hz.

However, you may also like to consider making a normal vented box but smaller. It sounds as though you may have oversized your box which is why the 40Hz excursion is excessive. Difficult to be sure though without knowing any details!

[Madmike2]

I thought the driver is Inside .... if its inside it is a dual chamber tri tuned band pass box ... if it isnt inside i apologize for misinforming you.

Edit : Just looked at the link again it is exposed. I just glanced at it briefly and snappped off a comment about it. I apologize. again.

[elambert]

Richie, thanks. I know the box I originally built was a bit oversized but I don't want to go any smaller as I love the low frequency extension with the 19 hz tuning. Heck, as I keep looking into the DCR box, I think I may just build it a hair bigger and tune to 17 hz. From the calcs I have done I should be ok on the excursion with the quatro there, and it would also translate to a Titanic or similar driver very well when I upgrade. Yes, I do enjoy doing sweeps and hearing all the doors, windows and light fixtures rattling in my house. Something satisfying about making a door shake in the next room...

Oh and the details about the original box. 6.0 cuft tuned to 19hz with nothing inside. Quite honestly this was my first real attempt at building something worth having and I rushed it a bit in the design stage. The bracing is insufficient and I haven't had the opportunity to test with wall coverings etc. I am highly considering just selling this box to a freind after a little more tweaking to buy an even more powerful sub for the next one... Titanic, Avalanche or something similar.

Madmike, no prob... we all have our days

[elambert]

Oh man, another question about this DCR deal...

The design calls for designing the box as you would a single reflex enclosure with two ports. I would really like to have more port volume than that, do you guys think if I desinged the box for 4 ports and put 2 in the top, 2 in the bottom and 2 connecting the chambers it would make any difference? I can't see logically how it would... but you never know. Or maybe even slot ports???

Just trying to hash out some ideas.

Ethan