Hello,
I'm looking to build something similar to the Linkwitz LXSub4 Dipole for use 50-400Hz (see image). I have 4x 15" drivers (Faital 15PR400) and each pairing would be driven by a MiniDSP 450W amplifier with DSP EQ/Crossover.
The plans are available to purchase, which is great, but the drawing is for 10" drivers, and I'm not wholly invested in the idea. I am looking for a quick proto to assess, before moving on to something more traditional if it doesnt work out.
If anyone can please advise: are precise dimensions required for this to work properly, and by extension, therefore also required for a 'scaled up' version?.
I did try to extrapolate from the internet drawing, and I am almost certain this drawing is not 100% accurate - no surprise as they require you to 'buy a license and then the plans'.
Hopefully someone has been here before with this design, or something similar, and can advise.
Thank you
I'm looking to build something similar to the Linkwitz LXSub4 Dipole for use 50-400Hz (see image). I have 4x 15" drivers (Faital 15PR400) and each pairing would be driven by a MiniDSP 450W amplifier with DSP EQ/Crossover.
The plans are available to purchase, which is great, but the drawing is for 10" drivers, and I'm not wholly invested in the idea. I am looking for a quick proto to assess, before moving on to something more traditional if it doesnt work out.
If anyone can please advise: are precise dimensions required for this to work properly, and by extension, therefore also required for a 'scaled up' version?.
I did try to extrapolate from the internet drawing, and I am almost certain this drawing is not 100% accurate - no surprise as they require you to 'buy a license and then the plans'.
Hopefully someone has been here before with this design, or something similar, and can advise.
Thank you
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It is all open for dipole radiation it can be readily scaled up for sub duty; there the wavelengths are so long that the cab does not interfere with radiated sound pressure waves. However, to get it to work as a midbass up to 400Hz the cab starts to matter. At cab width about half the wavelength wide at xover freq you may run into standing waves and such. Just thinking out loud here...
Koja is right, you will definitely have to worry about standing waves and cavity resonance using a 15” driver like this up to 400hz. The existing 10” design would have problems by 400hz too.
The good news is that Linkwitz laid out all of the math behind his dipole filters on his website, not just in the paid plans, so if you read carefully you can recreate the method. It will be helpful to be able to do ground plane measurements. I think that perhaps if you make the faces of the drivers close enough together similar to Nelson Pass’s open baffle experiment you will be able to go higher in frequency. Alternatively you can just do a flat baffle and miss out on the force cancellation.
The good news is that Linkwitz laid out all of the math behind his dipole filters on his website, not just in the paid plans, so if you read carefully you can recreate the method. It will be helpful to be able to do ground plane measurements. I think that perhaps if you make the faces of the drivers close enough together similar to Nelson Pass’s open baffle experiment you will be able to go higher in frequency. Alternatively you can just do a flat baffle and miss out on the force cancellation.
Technically there is no force cancellation in a design like this but also no force summation 😉
Thanks for the replies.
I mentioned 400Hz as an arbitrary number not realising upper mid bass is likely problematic. To be sure, it will operate to less than 300Hz, likely ~260Hz and with steep filter.
Are standing waves and cavity resonance likely to be an issue at <300Hz?
From responses, it seems upscaling the above plan is viable, great. I’ll try drawing it up.
Thanks again
I mentioned 400Hz as an arbitrary number not realising upper mid bass is likely problematic. To be sure, it will operate to less than 300Hz, likely ~260Hz and with steep filter.
Are standing waves and cavity resonance likely to be an issue at <300Hz?
From responses, it seems upscaling the above plan is viable, great. I’ll try drawing it up.
Thanks again
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Koja, Thanks.
As in NP slot loaded baffle with 6 drivers per side? If so, yes. If this trial works out then more toward the following with 4x 15PR400 per side Revelation - status of the project - Bert's WWWboard
If this OB is not quite to my taste, then to single 15 in straight or folded horn, and not too many surplus drivers - hence just trial with 2x 15" per side for now. From above, and to the comment of flat baffle, 2x 15"s sit too high for 55cm dia horn on top, Linkwitz is good in this regard.
There is also NPs OB 15" augmented with a second slot loaded 15" down-firing below that, the height could also be acceptable - is this likely to be a less compromised plan than the Linkwitz with 2x 15's?.
Cheers.
As in NP slot loaded baffle with 6 drivers per side? If so, yes. If this trial works out then more toward the following with 4x 15PR400 per side Revelation - status of the project - Bert's WWWboard
If this OB is not quite to my taste, then to single 15 in straight or folded horn, and not too many surplus drivers - hence just trial with 2x 15" per side for now. From above, and to the comment of flat baffle, 2x 15"s sit too high for 55cm dia horn on top, Linkwitz is good in this regard.
There is also NPs OB 15" augmented with a second slot loaded 15" down-firing below that, the height could also be acceptable - is this likely to be a less compromised plan than the Linkwitz with 2x 15's?.
Cheers.
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Could it be worth spending some time in hornresp to model freq and dB output? You could model different configs so quickly eg one 15" in a small baffle OB firing straight to the listening position to cover say 90 - 500Hz and under that use a sealed sub for the other 15" to cover about 35 -120 Hz. The sealed sub can be down firing in a low height config with volume extended out the back.
You should read about resonances of the different OB-baffle types and calculate usable frequency range based on that. For example here:
OB Theory
260Hz or 300Hz should be easily doable with a flat baffle and small wings (U-baffle) but that is only an estimation on my behalf.
You should simulate the 2x15" on a flat baffle with a SW like Basta or so to see how far you get and if cone excursion is within limits for your wanted SPL.
Although the said driver´s Qts is one the low side for OB and thus not optimal, you should be able to produce ample bass output with 4x15" as you can always "slightly" compensate the fall-off towards f_res with your minidsp.
It´s easy to give it a try and I don´t think you will regret it.
I´m using a single 12" per side with higher Qts though but much less volume displacement compared to you. It is plenty of bass for me although I don´t even boost/EQ.
Bass is clean and tight and no room resonances.
Using a steep highpass at 35Hz though to limit excursion towards fs.
Just an example for a flat baffle:
Lautsprecher Shop | Power Trio 1772 Bausatz - High End | Lautsprecher Selbstbau
OB Theory
260Hz or 300Hz should be easily doable with a flat baffle and small wings (U-baffle) but that is only an estimation on my behalf.
You should simulate the 2x15" on a flat baffle with a SW like Basta or so to see how far you get and if cone excursion is within limits for your wanted SPL.
Although the said driver´s Qts is one the low side for OB and thus not optimal, you should be able to produce ample bass output with 4x15" as you can always "slightly" compensate the fall-off towards f_res with your minidsp.
It´s easy to give it a try and I don´t think you will regret it.
I´m using a single 12" per side with higher Qts though but much less volume displacement compared to you. It is plenty of bass for me although I don´t even boost/EQ.
Bass is clean and tight and no room resonances.
Using a steep highpass at 35Hz though to limit excursion towards fs.
Just an example for a flat baffle:
Lautsprecher Shop | Power Trio 1772 Bausatz - High End | Lautsprecher Selbstbau
Thanks Joensd, flat would be fine if it were not for the height of the two drivers on a flat baffle.
Thanks Kazap, I'm not really a speaker guy so the intuition that you guys have is not something that comes naturally ie. hornresp etc.
However, if consensus were that the Linkwitz with 15's is too compromised for 50-300Hz then I'd start looking more closely at other OB schemes (incl. the links which joensd provided above).
Thanks Kazap, I'm not really a speaker guy so the intuition that you guys have is not something that comes naturally ie. hornresp etc.
However, if consensus were that the Linkwitz with 15's is too compromised for 50-300Hz then I'd start looking more closely at other OB schemes (incl. the links which joensd provided above).
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OK. Don´t know your "restrictions" towards height so if you want it small you could try a single woofer on baffle with EQ or alternatively a small sealed box with a single driver as a stand for the "rest". A "max flat alignment" in a sealed enclosure is only 45l (1 driver) and should give clean and articulated bass.
f-10dB would be "only" ~50Hz (disregarding room gain) but with the minidsp you can always boost some. If you can/want you could go up to 80l in size for a slower roll-off in bass output.
If I wanted compact I´d go for sealed with a single driver for sure.
If you wanted to make use of all 4 drivers, I´d go with kazap´s suggestion.
1x15" on the baffle, one sealed although I don´t know if that makes sense with the rest of your system.
f-10dB would be "only" ~50Hz (disregarding room gain) but with the minidsp you can always boost some. If you can/want you could go up to 80l in size for a slower roll-off in bass output.
If I wanted compact I´d go for sealed with a single driver for sure.
If you wanted to make use of all 4 drivers, I´d go with kazap´s suggestion.
1x15" on the baffle, one sealed although I don´t know if that makes sense with the rest of your system.
Thanks joensd, prefer to use all four drivers, yes. Looking to try 'open baffle', so sealed box isn't top of my list for now. With the kazap idea, ok but the mid/hf horn is 650mm in length and needs to be supported somehow, and 'sitting it on something' is too convenient to ignore.
Thanks Warrjon, very encouraging that the 12s can work without issue at 300Hz, is that likely to be the same for 15s?.. that would make it the least compromised approach for me at this time.
Cheers.
Thanks Warrjon, very encouraging that the 12s can work without issue at 300Hz, is that likely to be the same for 15s?.. that would make it the least compromised approach for me at this time.
Cheers.
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