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Subwoofer module

Tangband

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So I don't think I want to do a ground up plan for the woofer module... I was thinking of using Jeff Bagby's design or the CSS woofer module design and skip the passive crossover section. I was reading Jeff's white paper and he said he found his CSS woofer module didn't work well for the kairos, but great for the continuum. He felt his woofer module with the sb29nrx worked better with the Kairos. Either way, I'm leaning heavily toward a passive radiator built. I don't want sealed and I want to avoid port noise.

Jeff also made a comment about his crossover affecting the impedance of the Kairos... I really don't know how it will affect the LS50 meta... I'm worried it will drop it's impedance too much.

1. Is there any reason to use the passive crossover or can I simply use a minidsp 2x4hd and 2 stereo amplifiers to cross the LS50 meta with the module?

2. Would the CSS sdx10 or SB29NRX be a better choice for a woofer module?
Just some points :

1. A passive radiator is NOT better sounding than a proper bass reflex with a flared ( on both sides ) tube .
The opposite is true . A passive radiator is only usable if you want a really small box .

2. If using a passive filter as I suggested , there are some benefits .

A mini dsp gonna delay the signal and the delay is bigger if using high order crossover topology . Crossing at 100 Hz with minidsp and 24 dB linkwitz Riley filtering with no HP filtering for the metas gonna delay the signal to the subwoofers and you will hear it . If you want to cross the Ls50 with minidsp and use HP filtering with minidsp and thus avoid the delay, the minidsp is not transparent enough .

The passive approach that I suggest ( one big Aircoil for each subwoofer, one capacitor in series with each Kef ) is working really good If you use the subwoofer as a stand to each ls50 , and If you have a separate power amplifier in stereo for the separate subwoofer stands .

You can get inspiration from KEFs own R3 .
 
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DanielT

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Hm ... can something like this be part of the solution? I have in mind that miniDSP is not so good when it comes to HP filters. Please see it as a question and not as a statement.

 

Tangband

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Hm ... can something like this be part of the solution? I have in mind that miniDSP is not so good when it comes to HP filters. Please see it as a question and not as a statement.

That analog active LD crossover is probably better soundwise than minidsp, but dont have any eq options and may have a less good HP section. We dont know.

For best sound result , the passive crossover inside the ls50 meta would be taken out and the whole speaker redesigned for active crossover 3 way, with a subwoofer as a stand to every Ls50 Meta. You then have to have measurement skills to be able to outperform the Kef analog crossover. An analog active crossover like LD is not good enough because you cant equalize the response. And the HP section of the LD crossover is probably not transparent enough, soundwise.

A really good 3 way dsp crossover is unfortunately 1000 dollars or more . The dbx pa2 ( I have it ) is inferior soundwise to the dsp crossover thats inside my Genelec 8340 , and a good passive subwoofer solution for the ls50 may be the most cost effective way to improve the sound.

The minidsp is not playing in the same field , soundwise, as the ls50 meta with its analog crossover. Its not good enough.

If the goal is to maximize soundquality thats already very high in Ls50 meta, for not a lot money, its best to look at Kef r3 for inspiration, but maybe set the crossover somewhat lower at 100-125 Hz and use a real subwoofer driver.
The picture below shows a passive 6 dB crossover at 125 Hz for one loudspeaker , if the drivers are 6 ohm.
The capacitor can be connected at the + terminal of the ls50 meta.
ADF5CDE6-E840-4730-BC37-49C02FB4C71A.png
 
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DanielT

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That analog active LD crossover is probably better soundwise than minidsp, but dont have any eq options and may have a less good HP section. We dont know.

For best sound result , the passive crossover inside the ls50 meta would be taken out and the whole speaker redesigned for active crossover 3 way, with a subwoofer as a stand to every Ls50 Meta. You then have to have measurement skills to be able to outperform the Kef analog crossover. An analog active crossover like LD is not good enough because you cant equalize the response. And the HP section of the LD crossover is probably not transparent enough, soundwise.

A really good 3 way dsp crossover is unfortunately 1000 dollars or more . The dbx pa2 ( I have it ) is inferior soundwise to the dsp crossover thats inside my Genelec 8340 , and a good passive subwoofer solution for the ls50 may be the most cost effective way to improve the sound.

The minidsp is not playing in the same field , soundwise, as the ls50 meta with its analog crossover. Its not good enough.

If the goal is to maximize soundquality thats already very high in Ls50 meta, for not a lot money, its best to look at Kef r3 for inspiration, but maybe set the crossover somewhat lower at 100-125 Hz and use a real subwoofer driver.
The picture below shows a passive 6 dB crossover at 125 Hz for one loudspeaker , if the drivers are 6 ohm.
The capacitor can be connected at the + terminal of the ls50 meta.
View attachment 169871
Thought maybe in combination with miniDSP, so it gives opportunities to EQ.:)

Although that combination may not add anything. Even if it had been a 3 way active filter.
 

Tangband

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Thought maybe in combination with miniDSP, so it gives opportunities to EQ.:)

Although that combination may not add anything. Even if it had been a 3 way active filter.
The only thing that option will bring is probably more noise and worse sound.
 
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muad

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Just some points :

1. A passive radiator is NOT better sounding than a proper bass reflex with a flared ( on both sides ) tube .
The opposite is true . A passive radiator is only usable if you want a really small box .

2. If using a passive filter as I suggested , there are some benefits .

A mini dsp gonna delay the signal and the delay is bigger if using high order crossover topology . Crossing at 100 Hz with minidsp and 24 dB linkwitz Riley filtering with no HP filtering for the metas gonna delay the signal to the subwoofers and you will hear it . If you want to cross the Ls50 with minidsp and use HP filtering with minidsp and thus avoid the delay, the minidsp is not transparent enough .

The passive approach that I suggest ( one big Aircoil for each subwoofer, one capacitor in series with each Kef ) is working really good If you use the subwoofer as a stand to each ls50 , and If you have a separate power amplifier in stereo for the separate subwoofer stands .

You can get inspiration from KEFs own R3 .
So I'm going to go with a port. It seems implementing a PR properly might take some trial and error and seems to require more considerations.

I was planning on high passing the metas and essentially crossing over with the sub, effectively creating a 3 way. So delay won't be an issue? Which aspect of using the minidsp is audibly an issue? Seems like noise and distortion is 100db down.
 
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muad

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I've decided to just build one of the two Jeff bagby woofer modules and use the passive crossover in the vented configuration. Does anyone have any opinions regarding the css sdx10 vs the sb29nrx75 woofers?

I was also wanting to make the cabinet taller, so I have to adjust the port length probably. Which is the most recommended sim to model the cabinet volume vs port dimensions? I assume the current crossovers would work the same with a different port tuning?

Sorry for all the questions.. I'm pretty new at this
 

gy-k

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Using a coil/cap in series with the sub/speaker is going to change the FR of both. Probably not in a way you want in either case. You could load the impedance curve of the sub/speaker into Vituix, add the coil/cap and see the FR change.

If using a separate amp for the subs, knowing the input impedance of the amps, making passive line level filters could be an option as well. An RC filter for low-pass for the sub and a cap for high-pass for the speaker. The speaker's roll-off will be then the product of the speaker's natural roll-off and the 1st order roll-off of the high-pass cap. If you could get a response for the speaker out of this that is like a low-Q 2nd order roll-off, that summed with 1st order roll-off on the sub would result in a FR of the system that has a pretty big dip, but in theory that could be restored to flat with a PEQ boost. I've attached a pic of what I mean. (The dotted lines are responses without the global PEQ, the solid lines are the resulting responses. Notice that through the EQ boost the speaker isn't rolled-off at 100Hz. So I guess it depends. It is rolled-off 10db at 50Hz though. Plugging the port would be worth trying to see if that helps achieving a workable response.)
 

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Tangband

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So I'm going to go with a port. It seems implementing a PR properly might take some trial and error and seems to require more considerations.

I was planning on high passing the metas and essentially crossing over with the sub, effectively creating a 3 way. So delay won't be an issue? Which aspect of using the minidsp is audibly an issue? Seems like noise and distortion is 100db down.
You need to finetune a port to . Just putting in a specific length of port is probably not gonna sound good . And computer programs are almost always innacurate
 

Tangband

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I've decided to just build one of the two Jeff bagby woofer modules and use the passive crossover in the vented configuration. Does anyone have any opinions regarding the css sdx10 vs the sb29nrx75 woofers?

I was also wanting to make the cabinet taller, so I have to adjust the port length probably. Which is the most recommended sim to model the cabinet volume vs port dimensions? I assume the current crossovers would work the same with a different port tuning?

Sorry for all the questions.. I'm pretty new at this
Passive crossover and only one sub is a very bad idea soundwise Im afraid.
You need a steep filter with only one sub . More than 36 dB oct.
 
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muad

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Passive crossover and only one sub is a very bad idea soundwise Im afraid.
You need a steep filter with only one sub . More than 36 dB oct.
No, I meant either the sb29 or css sub modules :).

I definitely want two subs. So the best thing is to build them to a different height but keep the internal volume the same?
 
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