LXmini Clone

[MrHifiTunes]

I try to make a clone myself using a Dayton sig180 woofer (6.5"-91db) and a Dayton PS 95 (3.5" 85.5db) just try to learn the concept of the design a bit better

 

[olieb]

How loud can you play before you reach Xmax?
If the idea is to linearize the FR from the full range driver then assume the woofer isn't part of the equation right????
I can help it but 13-14 boost seems a lot for me.

The LXmini has been reviewed. https://www.erinsaudiocorner.com/loudspeakers/linkwitz_lx_mini/
Distortion at 96dBSPL shows that the SEAS full range is not yet at its Xmax limit at all.
The Peerless/Vifa driver Jokerbre uses has even more displacement volume (and lower distortion).

The idea of the filters in miniDSP is to linearize the drivers (both full range and woofer) in the passband and somewhat beyond and then apply a LR2 crossover.
The boost (6dB/oct) has to bee seen together with the attenuation from the high pass of the crossover.
The boost therefore is max around crossover frequency (≈700 Hz). Below the attenuation from the high pass takes over.
700 Hz is a frequency where the full range has quite some reserves.

I checked with VituixCAD. The highest excursion of the full range with these filters will be around 200 Hz and Xmax=2mm will be reached at about 107 dB.
But for this SPL you would have to provide around 500W at 800Hz. So max SPL is limited by amp power before reaching Xmax at least with normal source material.

 

[laserluxxer]

This is the final signal send to the tweeter. Maybe it helps.
olieb is spot on with everything he is saying.

 

[MrHifiTunes]

The LXmini has been reviewed. https://www.erinsaudiocorner.com/loudspeakers/linkwitz_lx_mini/
Distortion at 96dBSPL shows that the SEAS full range is not yet at its Xmax limit at all.
The Peerless/Vifa driver Jokerbre uses has even more displacement volume (and lower distortion).

The idea of the filters in miniDSP is to linearize the drivers (both full range and woofer) in the passband and somewhat beyond and then apply a LR2 crossover.
The boost (6dB/oct) has to bee seen together with the attenuation from the high pass of the crossover.
The boost therefore is max around crossover frequency (≈700 Hz). Below the attenuation from the high pass takes over.
700 Hz is a frequency where the full range has quite some reserves.

I checked with VituixCAD. The highest excursion of the full range with these filters will be around 200 Hz and Xmax=2mm will be reached at about 107 dB.
But for this SPL you would have to provide around 500W at 800Hz. So max SPL is limited by amp power before reaching Xmax at least with normal source material.

I did some simmulations in WINISD. The results are inline with what you mentioned. I didnt realize so much power is needed. When I compare my PS95-8 with the SEAS en Peerless/Vifa full range, i see that the Peerless/Vifa around 2 db less sensitive then the SEAS and Dayton. The Peerless and SEAS can handle more power then the Dayton (around double). Maybe the Dayton wasn't the best choice. Then the Sig180 I have is 91db sensitve iso 85 of the SEAS woofer. Will this alter the transfer function?

 

[olieb]

I did some simmulations in WINISD. The results are inline with what you mentioned. I didnt realize so much power is needed. When I compare my PS95-8 with the SEAS en Peerless/Vifa full range, i see that the Peerless/Vifa around 2 db less sensitive then the SEAS and Dayton. The Peerless and SEAS can handle more power then the Dayton (around double). Maybe the Dayton wasn't the best choice. Then the Sig180 I have is 91db sensitve iso 85 of the SEAS woofer. Will this alter the transfer function?

The original driver for the LXmini is FU10-04. According to SEAS sensitivity is 85dB/2.83V.

https://www.seas.no/index.php?option=com_content&view=article&id=377:h1600-04-fu10rb&catid=53:prestige-fullrange&Itemid=466

For PS95-08 Dayton gives about the same (85.5dB/2.83V).

https://www.daytonaudio.com/images/resources/295-349--dayton-audio-ps95-8-spec-sheet.pdf

The cone is somewhat smaller but the Xmax probably higher, displacement volume is approximately the same (7.1 vs 7.7cm3).
I do not see a problem there. The FU is not the best driver in terms of distortion (2 1.4 kHz peak see erinsaudiocorner) and FR is not great at all.
TC9FD might be the best choice for a very good price. TG9FD perhaps even a little bit better. These Vifa/Peerless have very nice FR and need little EQ.
And my LXmini can play more than loud enough with 125W (4Ω). 100 dBSPL at 1kHz is earsplitting.

 

[MrHifiTunes]

The original driver for the LXmini is FU10-04. According to SEAS sensitivity is 85dB/2.83V.

https://www.seas.no/index.php?option=com_content&view=article&id=377:h1600-04-fu10rb&catid=53:prestige-fullrange&Itemid=466

For PS95-08 Dayton gives about the same (85.5dB/2.83V).

https://www.daytonaudio.com/images/resources/295-349--dayton-audio-ps95-8-spec-sheet.pdf

The cone is somewhat smaller but the Xmax probably higher, displacement volume is approximately the same (7.1 vs 7.7cm3).
I do not see a problem there. The FU is not the best driver in terms of distortion (2 kHz peak see erinsaudiocorner) and FR is not great at all.
TC9FD might be the best choice for a very good price. TG9FD perhaps even a little bit better. These Vifa/Peerless have very nice FR and need little EQ.
And my LXmini can play more than loud enough with 125W (4Ω). 100 dBSPL at 1kHz is earsplitting.

I try to digest all the information. I came across the LXC website which got a lot of information. Seems the woofer reach xmax before the full range does. Does the more sensitive Dayton SIG180 help there? (91db vs 85db for the SEAS). I could probably add a -6db on the woofer and use a linkwitz tranform function to compensate in the low end.

 

[olieb]

I try to digest all the information. I came across the LXC website which got a lot of information. Seems the woofer reach xmax before the full range does. Does the more sensitive Dayton SIG180 help there? (91db vs 85db for the SEAS). I could probably add a -6db on the woofer and use a linkwitz tranform function to compensate in the low end.

If you want to play louder (or have less distortion) it is not so much the sensitivity you should be looking at for a woofer. In low frequency you will probably always max out because of excursion or more precisely because of displacement volume.
That said the SIG is certainly not a bad choice (displacement is about the same as the Seas L16). The Dayton needs somewhat less power, on the other hand the benefit of the Seas being the compact basket with a diameter of 146mm. A larger woofer/baffle will have more directivity around 700-1000Hz when the woofer is still contributing. "On axis" for the speaker is 90° off axis for the woofer. The "baffle" in the LXmini is 165mm. With the SIG this will increase at least by 10%. Whether that is relevant, idk.

 

[MrHifiTunes]

If you want to play louder (or have less distortion) it is not so much the sensitivity you should be looking at for a woofer. In low frequency you will probably always max out because of excursion or more precisely because of displacement volume.
That said the SIG is certainly not a bad choice (displacement is about the same as the Seas L16). The Dayton needs somewhat less power, on the other hand the benefit of the Seas being the compact basket with a diameter of 146mm. A larger woofer/baffle will have more directivity around 700-1000Hz when the woofer is still contributing. "On axis" for the speaker is 90° off axis for the woofer. The "baffle" in the LXmini is 165mm. With the SIG this will increase at least by 10%. Whether that is relevant, idk.

I was thinking more in the line of lowering the sensitivity of the woofer and bring it in line with the full range. The woofer has 91db, the full range 85db. I assume the woofer will roll off already before 100Hz in this overdamped pipe. If I lower the sensitivity from eg 80Hz (measurement will tell at which frequency the sensitivity is 6db down from 91db level) and higher frequencies withhigh shelf. This way I hope to avoid bottoming out the woofer and achieve the max output possible. Is this the right approach?

 

[olieb]

I was thinking more in the line of lowering the sensitivity of the woofer and bring it in line with the full range.

I do not understand, this is an active design. No need to adjust the sensitivities of the drivers.

The woofer has 91db, the full range 85db. I assume the woofer will roll off already before 100Hz in this overdamped pipe. If I lower the sensitivity from eg 80Hz (measurement will tell at which frequency the sensitivity is 6db down from 91db level) and higher frequencies withhigh shelf. This way I hope to avoid bottoming out the woofer and achieve the max output possible. Is this the right approach?

Linkwitz LXmini Speaker Review

Linkwitz LXmini Review

www.erinsaudiocorner.com

The LXmini has -3dB at approx. 50 Hz in the small tube of the (≈6,5l) - probably with EQ.
From TS-parameters -3dB would be more around 60Hz (without EQ).
Erin measured at 96dB and that is about SPLmax around 50 Hz for the LXmini (10% distortion).
From TS-parameters the SIG will roll off earlier (≈80 Hz) unless you increase the volume. Alternatively you can EQ of course.
If you want to play louder you need more displacement volume. The SIG180 has about 10% more than the Seas L16, that translates to about 1 dB more SPLmax. That is, IF the SIG is as good a woofer as the L16.

 

[MrHifiTunes]

I do not understand, this is an active design. No need to adjust the sensitivities of the drivers

Maybe I didnt use the right terminology. What I tried to say : I add a high shelf of -6db (91-85)around eg 100-120Hz. So actually reduce the signal level to make the output level equal to the full range driver. This to make f3 lower. I try to use the higher sensitivity of the woofer in such a way that I can avoid the need to EQ boost the lower frequenties which will bottom out the woofer faster.

 

[olieb]

Maybe I didnt use the right terminology. What I tried to say : I add a high shelf of -6db (91-85)around eg 100-120Hz. So actually reduce the signal level to make the output level equal to the full range driver. This to make f3 lower. I try to use the higher sensitivity of the woofer in such a way that I can avoid the need to EQ boost the lower frequenties which will bottom out the woofer faster.

What I do not understand: If you selectively change the sensitivity in some range by adding a shelf to the woofer signal you will not have a flat FR any more. Why?

And on the other hand regarding driver sensitivity: The 91dB are measured on an infinite baffle. In a tube with minimal baffle you will have a monopole radiation pattern and loose 6 dB.

 

[MrHifiTunes]

What I do not understand: If you selectively change the sensitivity in some range by adding a shelf to the woofer signal you will not have a flat FR any more. Why?

The high shelf is put at such frequency that FR stay flat. Actually it is equal to a gainsetting of -6db plus a linkwitz transform function.

And on the other hand regarding driver sensitivity: The 91dB are measured on an infinite baffle. In a tube with minimal baffle you will have a monopole radiation pattern and loose 6 dB.

True, but in the original design woofer and full range habe same sensitivity so I assume some adjustments need to be made with a higher sensitive woofer. Just to make it easy, I just look at the 2,83v/m sensitivity.

 

[olieb]

The high shelf is put at such frequency that FR stay flat. Actually it is equal to a gainsetting of -6db plus a linkwitz transform function.

OK, now I get it. It was too easy for me to understand ;-)

True, but in the original design woofer and full range habe same sensitivity so I assume some adjustments need to be made with a higher sensitive woofer. Just to make it easy, I just look at the 2,83v/m sensitivity.

The Seas measurement is not on infinite baffle but in (small) 10l-box. So the 82dB from the graph are monopole pattern already. I do not think there is significantly more than 3dB difference in sensitivity between SIG and L16 and this is mainly due to 4Ω versus 8Ω.

In any case here is Linkwitz himself explaining in full detail what and why and how he did it in LXmini.

Issues-7

Check heading F2.

 

[MrHifiTunes]

OK, now I get it. It was too easy for me to understand ;-)

No problem, it's not easy to explain properly as a newly.
Thanks already for time and effort you send on this topic. I think I can learn a lot from this design.

The Seas measurement is not on infinite baffle but in (small) 10l-box. So the 82dB from the graph are monopole pattern already. I do not think there is significantly more than 3dB difference in sensitivity between SIG and L16 and this is mainly due to 4Ω versus 8Ω.

This I don't understand. Both sensitivities are specified at 2.83v/1m. (Seas 84db/2.83v/1m Sig 91db/2.83v/1m)

In any case here is Linkwitz himself explaining in full detail what and why and how he did it in LXmini.

Issues-7

Check heading F2.

I didn't saw that one. Thanks

 

[olieb]

No problem, it's not easy to explain properly as a newly.

I was thinking to complicated.

This I don't understand. Both sensitivities are specified at 2.83v/1m. (Seas 84db/2.83v/1m Sig 91db/2.83v/1m)

You are right, my guess was off big time.
I did what I should have done for a long time. I took the formulas from Thiele-Small-Theory and calculated the efficiency.

Thiele/Small parameters - Wikipedia

en.wikipedia.org

Excerpt with little modification for room conditions.

Formulas for half space (infinite baffle) of a perfect piston in the far field for big wavelength.

With published specs the efficiencies are
SIG180: 0.350% (formula with BL, Mmms and Re) and 0.355% (formula with Vas, fs and Qe)
L16: 0.167% and 0.165% respectively. That is a difference of 3.2dB.

For sensitivity at 2.83V one gets SIG180: 90.8 dBspl/1m - L16: 85.5 dBspl/1m. This is a difference of 5.3 dB.

That is way more than I expected from eyeballing the parameters (one should not do that) ;(
The result for the L16 is about 1dB more than calculated by Seas (≈84.5 dB). I have no clue why.

All the above is in half space.
For the LXmini design with monopole radiation (full space) the sensitivities are about 6dB lower.

Thanks for the impetus!