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2 x 12" + 2" part 2

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bmwkid View Drop Down
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    Posted: 18 May 2017 at 7:34pm
Llo all,

I've been busy choosing the drivers and making first designs.
Here a picture of what it is atm :p


I went for 2 x  RCF MB12N301 speakers to accompany the RCF N980 HF Driver.

I'm just having trouble tuning the cabinet for these speakers.
De manufacturer says to tune at 60Hz, but that gives this result in WinISD



Tuning at 95Hz gives a peak at 100Hz.


I need some help here on what to do before i finisch upthe design.

All suggestions are welcome :-)

Kind regards.



Edited by bmwkid - 20 May 2017 at 8:23am
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bob4 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2017 at 8:12pm
close the gap between the upper 12" and your hf horn, you don't want to have even one mm more distance between them than necessary. Also I would definitely avoid creating any kind of peak in tuning. The extended bass with a -3 dB shelf for 60 Hz tuning is perfectly fine. You can EQ it a bit if you need more bass. The 100 Hz tuning would be totally useless, boomy at 100 Hz, but nothing below it. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luton_soundman Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2017 at 2:15am
My x2 12" + 2" built by Ultimate sounds
Sound Hire/Sales new/used equipment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bmwkid Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2017 at 6:09am
Thx for the info Bob. Tuning them @60Hz will probably reduce the vent size so i can lose the upper vent.

@Soundman
Are those tuning vents at the back of your nice build?

Regards,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2017 at 3:38pm
Originally posted by bmwkid bmwkid wrote:

Llo all,

I've been busy choosing the drivers and making first designs.
Here a picture of what it is atm :p

I went for 2 x  RCF MB12N401 speakers to accompany the RCF N901 HF Driver.

I'm just having trouble tuning the cabinet for these speakers.
De manufacturer says to tune at 60Hz, but that gives this result in WinISD


Tuning at 95Hz gives a peak at 100Hz.

I need some help here on what to do before i finisch upthe design.

All suggestions are welcome :-)

Kind regards.


First of all, do you already have the drivers? If not; check availability, as I think they're discontinued.
Second, I agree with Bob4 upthread about getting the Horn and mid drivers as close together as possible.
Third, you may not need to make it as big as 100l - making Vb smaller would actually help limit how peaky it gets if you use a tuning slightly higher than your first graph. Even if you're committed to certain outer dimensions for the box, if you need the internal volume to be smaller you can always install a separating panel between the mids and highs to reduce Vb - this will also help stiffen the box. Granted, it won't reach as low as the larger box, but assuming you're going to use it with some kind of subs then losing 10Hz or so of extension may be a valid tradeoff to get a smoother low end.
HTH,
David.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bmwkid Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2017 at 4:57pm
Hi David,

I have the drivers. Made an error in the firts post. It's the RCF MB12N301 http://www.rcf.it/products/precision-transducers/neodymium-low-frequency-transducers/mb12n301

I can reduce it to approx 70L with a panel between the HF and mids. Tuned at 68Hz gives this plot in WinISD:




Gone use them with subs and crossover at about 100 or 120Hz.

What is the benefit of placing the drivers close together?

Greetings,

Kris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2017 at 11:30pm
does anyone use 2.5 way crossover on boxes like this? should give loads better vertical pattern that way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bmwkid Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2017 at 9:43am
Updated design. Getting somewhere Smile




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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2017 at 12:37pm
Does the 2" driver need it's own separate compartment?

Originally posted by bmwkid bmwkid wrote:



What is the benefit of placing the drivers close together?


You reduce the distance between the acoustic centres of the 12" and HF drivers, minimising the chances of cancellation/dispersion issues around the x-over point.

Snowflake - do you simply mean to take some HF out of the lower 12" driver, or is there a more elegant way?


Edited by darkmatter - 20 May 2017 at 12:39pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bmwkid Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2017 at 1:03pm
Quote Does the 2" driver need it's own separate compartment?


It was a suggestion from David. And it makes good sense.

Quote Third, you may not need to make it as big as 100l - making Vb smaller would actually help limit how peaky it gets if you use a tuning slightly higher than your first graph. Even if you're committed to certain outer dimensions for the box, if you need the internal volume to be smaller you can always install a separating panel between the mids and highs to reduce Vb - this will also help stiffen the box. Granted, it won't reach as low as the larger box, but assuming you're going to use it with some kind of subs then losing 10Hz or so of extension may be a valid tradeoff to get a smoother low end.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2017 at 1:19pm
Fair enoughSmile I haven't compared the 70l @ 68Hz vs 100l @ ~65Hz sims so it's hard for me to judge.

It's probably silly for me to comment without seeing impedance / displacement / port velocity too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 20 May 2017 at 3:23pm
Its midbass with high excursion displacement isnt important.
Originally posted by bmwkid bmwkid wrote:

Does the 2" driver need it's own separate compartment?



No. You can remove it.
If you use midbasses with higher qts the response will be smoother(wont have this valley and mountain at bottom). You can make smoother response with this driver making smaller rear chamber, but smaller rear chamber will give higher vent resonances(winisd dont show them). Eitherway building relativly big enclose is way to do mid basses as it can be cut above group delay mountain of vent.

Originally posted by darkmatter darkmatter wrote:



You reduce the distance between the acoustic centres of the 12" and HF drivers, minimising the chances of cancellation/dispersion issues around the x-over point.

Snowflake - do you simply mean to take some HF out of the lower 12" driver, or is there a more elegant way?


http://www.riken.jp/~/media/riken/research/rikenresearch/RH_2014/hi_7787.jpg

Keep in mind with 2way you have 3 sources, in 2.5way you have 2

Edited by gen0me - 20 May 2017 at 3:25pm
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