Reference Compact Bass Filter (Oris Horns)

by Cappy @, Wednesday, December 06, 2006, 12:17 (4062 days ago)

Bert,

So I recently moved and got my system out of storage after a 1 1/2 year hiatus.

Looking through the forum, I notice that your recommended parameters for the bass filter have change, at least I think so...

Here is the message I found:

http://www.bd-design.nl/forum/index.php?id=9561

My first resistor is 1.2k instead of 1.3k. That is pretty close. But the first order cap is quite different, I am using 0.47 uF instead of 1.5 uF.

The other parts are the same as the shown filter (second cap 0.082 uf/82 nf).

It would be easy enough to add 1 uf of capacitance and see for myself, but I would like to hear your thoughts on the differences between the filters. I am assuming the Basic and Compact use the same filter?

The bass integration and response in my previous excellent room was superb. Of course, I'll take improvements anyway :)

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Reference Compact Bass Filter

by Bert @, Wednesday, December 06, 2006, 23:20 (4062 days ago) @ Cappy

Hi Cappy,

Sorry but I seem to have missed this one.... :)

My first resistor is 1.2k instead of 1.3k. That is pretty close. But the first order cap is quite different, I am using 0.47 uF instead of 1.5 uF.

The bigger cap results is some more deeper bass which some rooms/people seem to like better. That is basically all that the change is doing. The resistor change is doing a little bit the same but not by much (hardly audible).

There is another filter in the making though which is a bit steeper and therefore less disturbing in the lower midrange.

Ciao,

Bert

--
BD-Design - Only the Best!

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Reference Compact Bass Filter

by Cappy @, Wednesday, December 06, 2006, 23:39 (4062 days ago) @ Bert

Thanks Bert.

If the filter you mention is the higher order one similar to the Ultra newer filter, which preserves phase, I'll take it :)

Regarding 0.47 uF vs. 1.0 uF, when you say "deeper bass", do you mean that the bass will go lower, in Hz? Or that there is more bass energy at the existing frequencies. I would be interested in lower bass, but not necessary more of what I already have.

I need to learn more about filter theory to understand how this works, so I don't bug you any more. Any good references that you know of?

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Reference Compact Bass Filter

by Gasper, Thursday, December 07, 2006, 08:36 (4061 days ago) @ Cappy

Hi Cappy,


The theory:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
http://www.phys.unsw.edu.au/~jw/RCfilters.html#low

The calculator:
http://www.muzique.com/schem/filter.htm

I'm using 1kOhm/3,2(1+2,2)uF + 10kOhm/0,15uF filter - deep bass
:cool:

Regards,

Gasper.

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Reference Compact Bass Filter

by Cappy @, Monday, December 11, 2006, 00:28 (4058 days ago) @ Gasper

Thanks Gasper for the links. They raise more questions than they answer in my mind though.

For example, I am interested in how the cascaded RCs in a higher order filter effect the frequency response. I may well have missed that, but I haven't been able to find the answer to that, or a formula. It is clear that each cascaded RC increases the slope by 6dbs, but the values of the R and C obviously have some impact too. What is that impact?

I am also interested in knowing how the input impedance of the bass amp effects the frequency response of the filter.

Going back to the two filter versions we were discussing, the one I am using with a 0.47 uF cap, and the newer one with the 1.5 uF cap:

My filter if I understand correctly (I may not) has a knee frequency of about 260 hz. The newer filter knee is much lower, in the 80s. So with the newer filter the volume can be turned up, since there will be much less overlap at higher bass frequencies. This results in more bass energy at lower frequencies. However, the slope is still -12db in both cases, so the filters act quite differently around the bass/horn crossover point.

So if I understand this correctly, I see how there is much more bass energy at lower frequencies. It seems like there could more of a "gap" in the bass/horn crossover frequency though. Is this correct?

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Reference Compact Bass Filter

by Bert @, Monday, December 11, 2006, 00:43 (4058 days ago) @ Cappy

Hi Bill,

I am also interested in knowing how the input impedance of the bass amp effects the frequency response of the filter.

The cascades 6dB filter have influence to each other. The lower the next resistor the lower the Q of the filter and the less steepness behaviour of the filter. In principle the following resistor should be 10 times higher than the one in front to have the least influence. A low impedance amplifier acts as a relative low resistance as shown by the filter and that has negative influence to the filter in front it.

So if I understand this correctly, I see how there is much more bass energy at lower frequencies. It seems like there could more of a "gap" in the bass/horn crossover frequency though. Is this correct?

Yep, that is how it works. More deeper bass and filling the gap by increasing the volume. If there is too much deeper bass (or the gap is too wide) then lower the value to lift the higher bass frequencies.

Ciao,

Bert

--
BD-Design - Only the Best!

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Reference Compact Bass Filter

by Cappy @, Monday, December 11, 2006, 01:15 (4058 days ago) @ Bert

Very good. Thanks for the learning assistance.

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by Bert @, Thursday, December 07, 2006, 09:41 (4061 days ago) @ Cappy

Hi Cappy,

If the filter you mention is the higher order one similar to the Ultra newer filter, which preserves phase, I'll take it :)

It is another one, this one is close:

[image]

I would be interested in lower bass, but not necessary more of what I already have.

That is what it gives. More lower bass as in more gain at the deepest notes without changing the higher bass level...

Ciao,

Bert

--
BD-Design - Only the Best!

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Reference Compact Bass Filter

by Cappy @, Sunday, December 10, 2006, 23:07 (4058 days ago) @ Bert

That is great news that you are making progress on the higher order filter. I look forward to the Oris 200 version.

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by Bert @, Monday, December 11, 2006, 00:44 (4058 days ago) @ Cappy

Hi again Bill,

That is great news that you are making progress on the higher order filter. I look forward to the Oris 200 version.

It will still be a tuneable version to optimised for your room...

Ciao,

Bert

--
BD-Design - Only the Best!

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Reference Compact Bass Filter

by jdunham @, Tuesday, December 12, 2006, 15:13 (4056 days ago) @ Bert

Hi Bert,

I hope all is well with you.

I was interested to see that you are using a 4th order passive filter now. Having you experienced any problems with insertion losses with this? I ask because many people quote the use of PLLXO for higher orders as not practical so I never tried one.

I gave up with my third order one PLLXO (your original 150 filter), and now use a 4th order active device. But as I now have a good undertanding of which frequency cut-off to use for my set up, I'd like to go back to passive if possible.

Have you ever experimenting with a passive shelving filter to give a bit of bass to the lowest frequencies?

Kind regards,

Jonathan

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Reference Compact Bass Filter

by Bert @, Tuesday, December 12, 2006, 16:18 (4056 days ago) @ jdunham

Hi Jonathan,

Having you experienced any problems with insertion losses with this?

I am using it with a high sensitive bass system (which helps the gain) and a suitable amplifier for the bass (the BD30's). I even use a PLLXO with the Qausar MkII.... Problems are not that hard to create with PLLXO's, simply by using an amplifier with a low input impedance (< 20k) and gain becomes an issue...

Have you ever experimenting with a passive shelving filter to give a bit of bass to the lowest frequencies?

If you have enough gain in the system then you could make a passive line filter at the input of your main amplifer to boost the bass... or if the amplifier for the bass is sensitive enough you could even implement this within the PLLXO.

Ciao,

Bert

--
BD-Design - Only the Best!

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by jdunham @, Saturday, December 16, 2006, 13:33 (4052 days ago) @ Bert

Hi Bert,

Thanks for that. I was just wondering whether it was only the gain that was problem. My the bass amp set-up certainly does have enough gain. But maybe I need to check the input impedance of the ICEpower amps, that could be why I didn't have so much success with the passive cross-over.

Regards,

Jonathan

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