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Subwoofer suggestion for L`acoustic 108p

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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=94757
Printed Date: 29 February 2024 at 3:57pm
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Topic: Subwoofer suggestion for L`acoustic 108p
Posted By: 0krizia
Subject: Subwoofer suggestion for L`acoustic 108p
Date Posted: 15 February 2016 at 4:04pm
Hello.
 
Last november i invested in an L`acoustic 108p speaker,
this was a huge upgrade in my hobby and my 14 year old dream to own a speaker of this brand came true! 
anyways.... i noticed that this speaker is a speaker in its own league, i have never heard anything like it, the sound is so clear and detailed that it almost feels unnatural, but i have one problem. i can clearly notice that my subwoofer is mudding up the entire low end. If i set the crossover on the subwoofer at 80-100 hz, all the details in the drum and the lower  harmonics from upper frequencies is just mended into a muddy chaos. If i have the crossover at 50-60 hz it sound amazing but then i cant push the system so much since i like some extra power below 100hz and a 8" top speaker is not made for moving to much air below 80 hz.

so my question is: do any of you have a recomandation for a subwoofer driver that can match up to the L`acoustic 108p? i dont want to go bigger than 15 inch and my goal is to get a -3db at about 30 hz. 

the subwoofer i have now is BMS 12n630 in a 52L box with a 40hz tuning.



Replies:
Posted By: jacethebase
Date Posted: 15 February 2016 at 4:16pm
Get a DV-Sub they rock!

-------------
www.wedding-production.co.uk

www.stage2sound.com


Posted By: 0krizia
Date Posted: 15 February 2016 at 4:46pm
93 kg is to much weight and i cant buy their subwoofers without buying their amps witch make it reeeealy expensive.

L`acoustics company do not sell their passive speakers without L`acoustic amplifiers since their branding in the market it "exceptional sound quality" and they dont want bad sound equipment to mess up their sound.

i thinking more about buying a subwoofer driver i can build a Box to, buying new is way to expensive.


Posted By: krazyneil
Date Posted: 15 February 2016 at 5:57pm
i think that a cubo 15 or tham 15 would meet you 40hzneeds withouth being too big,
 
 
i think a 15"reflex sub would need to be fairly big to get near 40hz

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GOD TOLD ME TO DO IT !!!!!


Posted By: 0krizia
Date Posted: 15 February 2016 at 6:34pm
it does not have to be much louder than 120DB so i can trade some SPL for some better lows if that would help


Posted By: corell
Date Posted: 15 February 2016 at 10:13pm
Playing down to 30Hz -3db with a 12" or 15" and not sounding muddy wont be easy. The TSP which make chassis play low in vented enclosures are more or less the same that make them sound "slow". The ones that matter are : qts, Vas, fs and xmax to determine max spl.
You are looking for a qts of about 0,34-0,4 , a fs around 30Hz and as high xmax as you find. the only parameter you have a choice about really is the Vas. With a fixed fs, the Vas just depends on the mass of the cone (mms). A chassis with a high Vas is more likely to suit your needs, due to having a lighter cone, but will require a bigger cab...


Posted By: 0krizia
Date Posted: 16 February 2016 at 5:05pm
I though size didnt matter above 10" for bass/sub reproduction down to 30 hz ish.

what is TSP ?

what about 35hz - 3db ? 
I realy dont want a big box since im moving my sound equipment alot from place to place.




Posted By: DMorison
Date Posted: 17 February 2016 at 1:05pm
Originally posted by 0krizia 0krizia wrote:

I though size didnt matter above 10" for bass/sub reproduction down to 30 hz ish.

what is TSP ?
 
what about 35hz - 3db ? 
I realy dont want a big box since im moving my sound equipment alot from place to place.
 
TSP = Theile-Small Parameters - the characteristics that describe a woofer's behaviour in the box and allow it to be modelled.
 
Generally, the deeper you try and stretch a driver's response (by using a larger box and tuning it lower) the higher the "Group Delay" of the frequencies around the tuning frequency, hence sounding slower/muddier.
 
There is no hard & fast rule relating driver size to LF limit, because you also have to take into account other factors like how loud it needs to get and how big a space you need to fill with sound - a 6" hi-fi driver might get into the low 30's if you only need to play to 90dB max in a small room, but be completely useless if you try to get 110dB out of it in a large hall.
 
It is possible to get tighter response at the same time as going deeper but this relies on finding a driver that can easily be tuned well below the target low frequency limit while still staying reasonably flat down to that limit, which normally corresponds to a bigger driver. Not least because the lower you tune it the less control of excursion you have, so the higher the chance of distortion which further muddies up the sound. Using a larger driver that can shove more air for less excursion mitigates this to an extent.
 
HTH,
David.


Posted By: MarjanM
Date Posted: 17 February 2016 at 1:21pm
Whats wrong with your subwoofer?
You have a better subwoofers then your precious lacoustics tops.
I think you need to carefully time align the system and fine tune the dsp processing for the entire system.
Not change the subs.


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: 0krizia
Date Posted: 17 February 2016 at 4:25pm

i find it hard to belive that a 300$ subdriver is better than a 4000$ 8" speaker.

It might be the enclosure that is not good. i didnt follow the recommendation by BMS because i wanted more output from the driver so i built a bigger box and with higher tuning. Might be posible to get better result with another box but atleast now, it does not sound good at all compared to my top speaker.
if the top and the sub are stacked together do you think it has any time delay ? How would a DSP help me out? i have never used one. 

i also could not get more than 80DB out of the sub at 4m away with 700W and low cut at 40hz last time i used it. It was a 10X10m room with 5m under the roof ish. i was hoping i could get more out of it.
(mesured with "A" weight in SPLnfft app) 


Posted By: csg
Date Posted: 17 February 2016 at 5:32pm
The components in your 4000$ cost L acoustics an awful lot less than 4000$...possibly less than 300$

Im not saying either component is bad, i generally find L acoustics kit very well voiced, however you do have a very good and capable sub driver there and with a box that brings the best from it, coupled with sensible eq and processing you should be able to get extremely good results.


-------------
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”


Posted By: 0krizia
Date Posted: 17 February 2016 at 6:23pm
Thank you for this information David.

So if i wanted a clean sound down to say 35hz, i should tune it lower than 35hz in order to have less group delay. Ill lose alot of output in that way tho. guess thats where bigger driver comes in (-.-)
i was hoping i could get away with a small sub. 

But i dont think group delay is the problem when the muddy sound is not only below 60hz but in the whole spectrum the sub is capable of playing in.





Posted By: DMorison
Date Posted: 17 February 2016 at 7:51pm
Originally posted by 0krizia 0krizia wrote:

i also could not get more than 80DB out of the sub at 4m away with 700W and low cut at 40hz last time i used it. It was a 10X10m room with 5m under the roof ish. i was hoping i could get more out of it.
(mesured with "A" weight in SPLnfft app) 

OK, couple of issues coming to light now.

First, https://en.wikipedia.org/wiki/A-weighting" rel="nofollow - A weighting is used where you want to focus on mid frequencies so will always give poor results for sub - it's artificially reducing your 40Hz SPL by approximately 34dB! That means that you should really have about 114dB at 40Hz.
Always use unweighted for sub measurements.

Second, you may be driving that cone well beyond where it can stay linear, which would increase distortion and account for a lot of your muddiness.

Here's what WinISD thinks is happening at 700W. Yellow is your box, green is the same volume tuned down to 35Hz.
First graph is SPL, it predicts just a little bit higher than 114 at 40Hz, once you get rid of the weighting.
Second is Group Delay and you can see there where tuning lower to give a flatter frequency response gives less group delay over most of the band, at least until you get to the new low frequency corner.
Third is excursion, and it looks like with either tuning 700W is just a bit too much for this driver, so it will probably not sound at its best unless you back it down a few dB. Don't worry about excursion going off the scale below tuning - your HPF should take care of that, but it's still leaving a lot of excursion in the 45-70Hz range, which may result in excess distortion, muddying up everything for you. I didn't try to model the exact HPF as you didn't give the order & alignment I don't think.

Quote Thank you for this information David.

So if i wanted a clean sound down to say 35hz, i should tune it lower than 35hz in order to have less group delay. Ill lose alot of output in that way tho. guess thats where bigger driver comes in (-.-)

Yes, you can see that the excursion problems would get worse if you tuned lower (as well as losing a couple of dB of level around 40Hz too), which is why bigger/better drivers that can make up for that without going over Xmax would be beneficial if you really want to minimise GD.

Quote i was hoping i could get away with a small sub. 

But i dont think group delay is the problem when the muddy sound is not only below 60hz but in the whole spectrum the sub is capable of playing in.

There's a thing in speaker design called Hoffman's Iron Law - which basically means that you have to trade off box size, loudness and LF extension against each other, so if you want small at least one of the other two is going to suffer.

As can be seen above, tuning low can help Group Delay and give good extension but often at the expense of Excursion which can lead to distortion, which I think might be the most likely reason for your box not sounding good across it's whole range.

If you can live with running it on less power (about 3-4dB less should keep the excursion under control) you might notice the sound cleaning up, but then you might not feel it's loud enough.

Edit - wrong image (and diagnosis) posted earlier, now fixed.


Posted By: 0krizia
Date Posted: 18 February 2016 at 10:53am
i have read about a guy giving 1200w to the 12n630 with no problem with low cut at 38hz.
I think he was named Tony on this forum. so why does your graph show to high xmax at 700w?
http://forum.speakerplans.com/q12-12-sub_topic28555.html

I also dont get the spl mesuring. I have been on a metal concert where they played at 110db and that its crazy loud!!
That beeing said, i have experienced a Rammstein concert where they played 120db in avrage and that was unbearable, my eyes was blurring with the kick drum, i could even feel all my clothes vibrating and a pure sensation of mild pain in my ears.
I dont understand how a simple 12" can achive anything even close to those sensations. What am i missing?


Posted By: DMorison
Date Posted: 18 February 2016 at 1:30pm
Originally posted by 0krizia 0krizia wrote:

i have read about a guy giving 1200w to the 12n630 with no problem with low cut at 38hz.
I think he was named Tony on this forum. so why does your graph show to high xmax at 700w?
http://forum.speakerplans.com/q12-12-sub_topic28555.html

I also dont get the spl mesuring. I have been on a metal concert where they played at 110db and that its crazy loud!!
That beeing said, i have experienced a Rammstein concert where they played 120db in avrage and that was unbearable, my eyes was blurring with the kick drum, i could even feel all my clothes vibrating and a pure sensation of mild pain in my ears.
I dont understand how a simple 12" can achive anything even close to those sensations. What am i missing?
 
Tony's box was smaller, which always helps control Excursion, and he (usually) used EQ or boosted alignments to flatten the low end (that project was -6dB at 38Hz on its own), and the boost/EQ uses up a bunch of the stated power so he most probably did not have all that power dumped on the driver at the frequencies where excursion was highest.
 
(Excursion is low right near the box tuning frequency, so if you chose the shape of the boost carefully you can often throw more power at a driver at those particular frequencies to flatten the response without so much of a problem with distortion.)
 
Regarding overall SPL's, our ears are more sensitive to midrange frequencies, so 110dB for a full band mix will always sound a hell of a lot louder than 110dB just at 40Hz.
 
 
Edit: Tony's project was also tuned higher to start with, which also reduces excursion in-band.


Posted By: 0krizia
Date Posted: 18 February 2016 at 4:49pm
Is it the presure in a small box that makes it less prone to excution?

So what i need to match up against my top speaker is atleast 1 15 inch sub, since it can move more air with less excution? If so, any light weight recomandations?


Posted By: DMorison
Date Posted: 18 February 2016 at 9:11pm
Originally posted by 0krizia 0krizia wrote:

Is it the presure in a small box that makes it less prone to excution?

So what i need to match up against my top speaker is atleast 1 15 inch sub, since it can move more air with less excution? If so, any light weight recomandations?

Think about it like this:

If the speaker has a surface area of 500cm2, and you want it to move 1cm each way, then it has to compress the air in the box by half a litre extra, and stretch it out by the same amount for every cycle.

If the box is 50l, then that half litre is 1%, but of the box is 100l then that half litre is only 0.5%, so it represents less resistance to the physical movement of the speaker cone.

For light 15's, the big brother of your current one isn't bad, but does want a rather bigger box to get reasonably low.

You might also look here, another poster had similar goals: http://forum.speakerplans.com/ciare-punisher-sub-br011_topic87634_page2.html



Posted By: MarjanM
Date Posted: 18 February 2016 at 10:49pm
You have only one subwoofer?
If yes, then that is one of your problems. Ideal subwoofer/top ratio is 2:1. Not 1:2.


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: jacethebase
Date Posted: 18 February 2016 at 10:58pm
Originally posted by MarjanM MarjanM wrote:

You have only one subwoofer?
If yes, then that is one of your problems. Ideal subwoofer/top ratio is 2:1. Not 1:2.


The 108 is a very small box designed for small speech applications and install applications etc so 1 sub is probably about right for what it's designed for.

If your trying to have a "rave" with it then it's the wrong box for the job.



-------------
www.wedding-production.co.uk

www.stage2sound.com


Posted By: 0krizia
Date Posted: 19 February 2016 at 5:33am
i only have 1 108p box but sound is my hobby and i dont use it for anything else than small gatherings with friends and at home. this litte badass box can outplay my two 2 HK audio 12" pro top boxes in SPL before it distort, infact i have not managed to make the L acoustic distort yet. 
1 12" sub dont seem like it can keep up with it.



Posted By: jacethebase
Date Posted: 19 February 2016 at 6:55am
Timmy?

-------------
www.wedding-production.co.uk

www.stage2sound.com


Posted By: jammin75
Date Posted: 19 February 2016 at 8:00am


this one ? LOL

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feel the vibes !!!   "Who Feels it Knows it"            Strong like Lion              



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