A bass-boost circuit for OB

[Roushon]

The re-designed bass-boosts

The bass boost circuits (both the passive and the notch-filter one) are
re-designed to change its cut-off frequency so that it suits the OB.
The Linkwitz bass boost with notch filter circuit is designed using LME49740
and its PS is designed using LM4562 as in the application notes AN-1561.

At first I will try the passive one then go on to active.

Regards
Roushon

 

[Roushon]

Some more pcb

Not having access to my tool-box as everything packed to move to a new
apartment I am in front of my computer only and so designed some more pcbs
for the bass-boost and posting if it helps some readers....

Comments are welcome....

Roushon

N.B. The resistors under the 1uF cap may be soldered on the track side.

 

[Roushon]

passive tried

I managed to try the passive bass boost using the component values: R4(R9)=250K LOG,
C1(C3)=1uF, C2(C4)=470n. But I did not hear any bass getting boost. I simulated
the circuit by some program matching with the response curve in MJK's note.
I will trying by lowering the value of C2 significantly. Any suggestions?

Thanks and regards
Roushon.

 

[Roushon]

Not satisfied

Although not sure if anybody watching I keep reporting.
Reduced C2 down to 22nF but not satisfied. Simply do not
hear any bass improvement. The simulation shows
a huge boost. May be I made some mistake
or I have some ear infection. Got to try the active ones
now unless somebody reports some alternate way
of passiving......

I used the simulator for James tone control in the page TSC

Roushon.

 

[Roushon]

Final passiving

The attached circuit is the final and tested passive bass
boost circuit for the OB. I am very happy with its
performance. I think I do not need the active one anymore.

Roushon.

 

[tubob]

Hi Roushon,

Can you describe the improvement of the bass with the circuit?
Since it is passive where exactly the circuit can be placed, is it still between
the cd player and the amp or can be somewhere else?

tubob

 

[Roushon]

Hi Roushon,

Can you describe the improvement of the bass with the circuit?
Since it is passive where exactly the circuit can be placed, is it still between
the cd player and the amp or can be somewhere else?

tubob

Hi Tubob,

I measured by my ears only, there is no other method I have. I can hear the
Eminence more prominently now in low volume also. Of course the boost is
not too much as it can be with active one. But I do not need that much.

The circuit is in between the cd player (Marantz 5003) and the amp.

The resistors are 1/4W 1% metal film and the cap is 63v metalized polyester.

Regards
Roushon.

 

[Vix]

Roushon,

What is the input impedance of your amplifier?

 

[Roushon]

Roushon,

What is the input impedance of your amplifier?

The amp has a buffer using OPA627 and there is a 100k resistor
from the input pin of the OPA to ground and also there is an input cap (1uF).

Regards
Roushon.

 

[Roushon]

The circuit of the (one channel) amp is in this thread (post number 64).
The resistor 1k in the input is later replaced by 82R.

http://www.diyaudio.com/forums/chip...el-two-inverted-lm3886-buffer-dc-servo-7.html

Roushon

 

[Vix]

Thanks!

 

[hipanni]

hi this is kamal,
i need to best tone control for stk 4142 ic

 

[ben595]

The attached circuit is the final and tested passive bass
boost circuit for the OB. I am very happy with its
performance. I think I do not need the active one anymore.

Roushon.

A newbee question: what is an OB?

I want to boost the bass I'm getting from a gainclone kit from audio sector.com. Will this circuit help me boost the bass? I'm using it to amplify my PC sound card output.

Thanks.

 

[Roushon]

OB stands for Open Baffle. This is a speaker where the drivers are placed on
a piece of large baffle only. There is no box. These kind of speakers is a bit
shy of the low frequencies. That is why a bass boost is needed. Type Open
Baffle in google and you will see.

You can use the above circuit in your case also, but you need to change
the cap value depending on your amp and speakers. I have mentioned
somewhere in this thread some software to calculate this value.

Best wishes
Roushon

 

[kees52]

The attached circuit is the final and tested passive bass
boost circuit for the OB. I am very happy with its
performance. I think I do not need the active one anymore.

Roushon.

I did use it with the hybride tube/fet amp with martins H frames and now it is a lot better, input impedance is 2 k from the pot so it is after the pot on the input of amp.

thanks

 

[Roushon]

I did use it with the hybride tube/fet amp with martins H frames and now it is a lot better, input impedance is 2 k from the pot so it is after the pot on the input of amp.

thanks

Thank you for using the circuit and I am happy that you found it good for your setup.

Roushon

 

[CLS]

If the woofer is low-Q, you can try varible output impedance to shape the response:

http://www.passdiy.com/pdf/cs-amps-speakers.pdf

Variable Amplifier Impedance

 

[ashok]

In many cases a high Zout may not give the full required equalisation for an OB driver. Basically it needs an LPF filter with very low Fc, say 30 to 40 Hz and 6dB slope. With this the bass will still roll off again below Fs of the mounted driver and the HF end can be flattened out or rolled off with another filter as desired to achieve the desired response in the useable range.

A HPF filter ( at least 12db/oct) set at a low frequency like 20 Hz will protect the driver from over excursion and potential mechanical damage. This is a very real problem. I've seen an unprotected 12 in driver with it's spider ripped out !

 

[CLS]

In many cases a high Zout may not give the full required equalisation for an OB driver. Basically it needs an LPF filter with very low Fc, say 30 to 40 Hz and 6dB slope.

...

Yes, that's exactly what I do (in line level).

As to the low end protection, I use a 1/60 oct. -60dB notch filter @ 20Hz in digital EQ 😀

 

[ashok]

Did you really mean 'notch filter' or was that a typo ? Shouldn't everything below 20 Hz be cut off ? Just a high order HPF.