2 x 12" + 2" part 2
Printed From: Speakerplans.com
Category: Plans
Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
URL: https://forum.speakerplans.com/forum_posts.asp?TID=98559
Printed Date: 19 April 2024 at 9:34pm
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Topic: 2 x 12" + 2" part 2
Posted By: bmwkid
Subject: 2 x 12" + 2" part 2
Date Posted: 18 May 2017 at 7:34pm
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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. |
Replies:
Posted By: bob4
Date 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. |
Posted By: luton_soundman
Date Posted: 19 May 2017 at 2:15am
My x2 12" + 2" built by Ultimate sounds ------------- Sound Hire/Sales new/used equipment. |
Posted By: bmwkid
Date Posted: 19 May 2017 at 6:09am
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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, |
Posted By: DMorison
Date Posted: 19 May 2017 at 3:38pm
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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bmwkid wrote:Posted By: bmwkid
Date Posted: 19 May 2017 at 4:57pm
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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" rel="nofollow - 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 |
Posted By: snowflake
Date Posted: 19 May 2017 at 11:30pm
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does anyone use 2.5 way crossover on boxes like this? should give loads better vertical pattern that way. |
Posted By: bmwkid
Date Posted: 20 May 2017 at 9:43am
Updated design. Getting somewhere    |
Posted By: darkmatter
Date Posted: 20 May 2017 at 12:37pm
Does the 2" driver need it's own separate compartment?
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?
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Posted By: bmwkid
Date Posted: 20 May 2017 at 1:03pm
It was a suggestion from David. And it makes good sense.
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Posted By: darkmatter
Date Posted: 20 May 2017 at 1:19pm
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Fair enough 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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Posted By: gen0me
Date Posted: 20 May 2017 at 3:23pm
Its midbass with high excursion displacement isnt important.
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.
http://www.riken.jp/~/media/riken/research/rikenresearch/RH_2014/hi_7787.jpg" rel="nofollow - 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 |
Posted By: snowflake
Date Posted: 20 May 2017 at 5:03pm
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2.5 way crossover usually seems to be implemented by having the woofers in parallel and putting an inductor in series with one of the woofers so it has a LPF at the baffle step frequency. bass is increased by 3dB giving a flat response through the baffle step region. alternatively you could wire the woofers in series and put a capacitor across one of them to implement the LPF. the response woudn't be flat but you would have the extra power and excursion capacity to get flat response with eq. would lose 3dB of headroom on the amp but the higher impedance load at bass frequencies would help. the hf crossover is between the tweeter and the top woofer, rather than all three drivers. the midrange is covered by one driver rather than two, and at bass frequencies the two woofers are close enough that they act as a single source anyway. |
Posted By: nickyburnell
Date Posted: 20 May 2017 at 5:12pm
Bloody marvelous explanation  ------------- It's everything, not everythink! |