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Old 15th March 2013, 09:03   #1
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Default Troubleshooting Infinite Baffle Install in a Zen

Hi,

I have the following setup Kenwood 8016BT , JBL 3501, JBL 1004, Front stage is Infinity component and rear fill is 6x9 Polk DB691 along with two Polk MM1040DVC. Each DVC is wired on 2ohm to each channel of 3501 . Two channels are there in 3501.

In 3501 I have given 12db boost and set HPF to 100hz.
On stereo HPF for front is at 70hz with 12db and so is rear 6x9.
The woofer LPF is at 80hz with 12db.

When I was running a 12 inch Infinity ref woofer in a box below the rear shelf (6x9 are installed in it) I had impeccable sound (with woofer doing what it should do). However due to space issues, I moved to two 10 inchers on the rear shelf itself (thinking IB will give me equivalent of what I had with one 12 inch in box ) . The sound now is precise but not deep.

What should I do?

Last edited by GTO : 15th March 2013 at 13:07. Reason: PM coming up
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Old 15th March 2013, 10:02   #2
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Default re: Troubleshooting Infinite Baffle Install in a Zen

Hello Trust_In_Thrust

Woofer needs a proper enclosure as suggested by company in their catalogue , woofer will sound best in a properly designed company spec enclosure . When the woofers were there in a box and it was air tight , woofer must be churning out deep bass. I would say please check the specs on company website and get the woofers installed back in the box for optimum performance .

Last edited by GTO : 15th March 2013 at 13:09. Reason: Quoted post edited
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Old 15th March 2013, 10:09   #3
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Default re: Troubleshooting Infinite Baffle Install in a Zen

IB installs need a lot fo work to get right. The chance of boom and resonance is great.

The 3501 is a mono amplifier. The input of both channels is summed and sent to both speaker terminals. The amp has a LPF that can be set from 32-320Hz and a HP EQ that can be set from 10-100hz. Since IB boxes do not have the damping that sealed boxes do you need to adjust the DBO (HP EQ) the resonsance frequency of the box - start at 10hz and slowly move up till you find the point where there is least resonance (the boost level should be aout 1/4 to 1/3) or tightest response.

The LPF and 1004 settings look ok.

Last edited by GTO : 15th March 2013 at 13:09. Reason: Quoted post edited
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Old 15th March 2013, 22:09   #4
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Default re: Troubleshooting Infinite Baffle Install in a Zen

Quote:
Originally Posted by navin View Post
IB installs need a lot fo work to get right. The chance of boom and resonance is great.

The 3501 is a mono amplifier. The input of both channels is summed and sent to both speaker terminals. The amp has a LPF that can be set from 32-320Hz and a HP EQ that can be set from 10-100hz. Since IB boxes do not have the damping that sealed boxes do you need to adjust the DBO (HP EQ) the resonsance frequency of the box - start at 10hz and slowly move up till you find the point where there is least resonance (the boost level should be aout 1/4 to 1/3) or tightest response.

The LPF and 1004 settings look ok.
I have the DBO all the way to 100Hz (with 6db boost) as anything lower say below 80hz the woofer excursion is going out of control (even at no boost, i start getting the phat phat sound) I really look forward to get the best out of it .As of now it looks i may have to move back to sealed box .The irony is i am not sure will it be better to go sealed with 2 10inchers or go and buy a new 12inch woofer again.

I will post pics tomorrow on the current setup .
I just want it to be excellent (which is not there now in lower frequency band below 80hz).
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Old 16th March 2013, 10:16   #5
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Default Re: Troubleshooting Infinite Baffle Install in a Zen

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Originally Posted by Trust_In_Thrust View Post
I have the DBO all the way to 100Hz (with 6db boost) as anything lower say below 80hz the woofer excursion is going out of control (even at no boost, i start getting the phat phat sound) I really look forward to get the best out of it .As of now it looks i may have to move back to sealed box ..
What is the Qts of the woofer?
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Old 16th March 2013, 20:47   #6
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Default Re: Troubleshooting Infinite Baffle Install in a Zen

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What is the Qts of the woofer?
Qts is .5. Attached is spec sheet of MM1040DVC.
I did few changes today in head unit front components set at 70Hz with 24db slope , rear coaxial at 70hz with 24db slope , woofer at 70Hz with 24db slope. The woofer setting for DBO high pass frequency is at 60Hz with boost of 4db approx.It sounds a lot better but still i feel it needs to better the single 12inch infinity reference i was running before in sealed box.Also the 3501 has two speaker output channels . I have wired each DVC as 2 ohm load to each channel separately.I somehow think to better the clarity and sound i need to seal the edges of the hatch around the parcel shelf(on which i have installed both DVC and 6x9 pair ) against the boot door , rear seat etc. If it can help any suggestions how ?

Also please explain what actually is DBO & how does it differ from simple bass increase ?
Attached Files
File Type: pdf MMsubwoofer_spec.pdf (33.6 KB, 220 views)

Last edited by Trust_In_Thrust : 16th March 2013 at 20:50.
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Old 18th March 2013, 11:56   #7
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Default Re: Troubleshooting Infinite Baffle Install in a Zen

Quote:
Originally Posted by Trust_In_Thrust View Post
Qts is .5. Attached is spec sheet of MM1040DVC.

The woofer setting for DBO high pass frequency is at 60Hz with boost of 4db approx.It sounds a lot better but still i feel it needs to better the single 12inch infinity reference i was running before in sealed box.

If it can help any suggestions how ?

Also please explain what actually is DBO & how does it differ from simple bass increase ?
General guidelines:
Qts < 0.3 = vented bxoes
0.3 < Qts < 0.35 = vented and sealed boxes (depends on Vas and Fs)
0.35 < Qts < 0.4 = sealed boxes
0.4 < Qts < 0.5 = large or lossy (aperiodic) sealed boxes
0.5 < Qts < 0.6 = IB and large or lossy (aperiodic) sealed boxes
Qts < 0.7 = IB (Vb > 5 times larger than the Vas)

The ammount of EQ you need is based on the Fs of the IB woofer. Remember in a really true IB IB system Fs is the knee (turnover frequency).

Yes for IB a seal really helps. It is painstaking process of eliminating one leak at a time when it comes to car hatches.

There is no significant difference between a DBO and a Bass boost - both are derivatives of "Parametric Equallization". Parametric EQ means controlling EQ via 3 parameters - aka the Fc, Q and Gb. This technology has been around since the 1950s (hence the terms I used are also that old). Fc is the control frequency (sometimes called the center frequency), Q is width of the bell shape curve of the EQ, the Gb is the Gain (in the bandwidth determined by Q).
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