Home Theater Forum and Systems banner

1 - 20 of 57 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter · #1 ·
Hi Folks,

I wondered if you could give me some advice here.

I decided to build 2 x sealed enclosures for 2 LMS ultras that I brought.

I used 50mm mdf to give me the least hassle building two layers and due to lack of tools/clamps etc.

The boxes are around 3.5 cubic ft but (taking the magnet/ cone and wood) are 2.3cubic ft internal volume.

To power these I purchased a fp1400 clone which has so far worked well. I have been running it on a 13amp plug 240volt. I read that this amp needed its own supply but figured I would try it out and if worst come to worst the 13amp plug would blow?

I wired both subs to 4 ohm. They sound terric and blend in with speakers perfectly even without eq. Crossover is set to 120hz on subs.

The other night I was doing some sine tests. About 2 minutes in on 20hz (was loud but no amp clip) both subs at the same time made a cracking noise and gave up the ghost. No over excursion (probably 20mm) and no mechanical sound was present.

I was clearly gutted and understand I was to be honest me being an idiot but its no different to tests that I have done in the past with other subs.

I am going to get two more baskets and be real gentle this time.

Besides the obvious i.e Not play sine's at high volume etc. What other things can I do to ensure this does not happen again? and can anyone comment on possible causes?

Really appreciate any advice.





Thanks
 

·
Plain ole user
Joined
·
11,121 Posts
At what level were you driving them? You said loud but not clipping but what exactly does that mean?
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #3 ·
Hi,

Sorry I am trying to attach pictures from photobucket but will not let me.

I meant the amp clip light was not engaged.

Cheers
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #5 ·
Hi,

Would it help engaging the volt limiter? I wonder what level to set it too?

I did not think this matter as I guessed if the amp pulled more than 13amps the fuse would go on the plug? 13 amps 240 volt is equivalent to around 3000 watts so thats only 1500 a side or does it not work that way?

Thanks
 

·
Registered
Joined
·
114 Posts
I'm still wondering how you melted the coils as these drivers can take alot of stick.

You say loud but what volume are the subs run hot more than 75dB.
 

·
Premium Member
Joined
·
19,397 Posts
About 2 minutes in on 20hz
Sine waves are a constant voltage to the coils, something they were never designed for, and you burnt the coils. 15 seconds is long enough for a sine wave when played loud, with time between tones for the coils to cool down.

With a ported enclosure you can smell the coils heating up from the ports and can back off, with sealed you have no warning.
 

·
Registered
Joined
·
114 Posts
Sine waves are a constant voltage to the coils, something they were never designed for, and you burnt the coils. 15 seconds is long enough for a sine wave when played loud, with time between tones for the coils to cool down.

With a ported enclosure you can smell the coils heating up from the ports and can back off, with sealed you have no warning.
Missed that bit, thanks.
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #9 ·
Hi Guys,

Thanks for your comments. Guess its as mike said and I was just a fool. the svs ultra I had before never had any issues with sines but I guess it had the ports to cool the coil + a lot less power.

I was playing at around 120db in room volume.

Thanks
 

·
Premium Member
Joined
·
15,054 Posts
Hi Guys,

I was playing at around 120db in room volume.

Thanks
Yup, that would do it. 120db is way to hot for a constant 20Hz tone.:hsd:
 

·
Premium Member
Joined
·
15,054 Posts
Nice looking boxes, Hopefully you will be up and running again soon.
 

·
Registered
Joined
·
26 Posts
Discussion Starter · #15 ·
Guys, Is 2.3cubic internal volume too small for these subs? I was really trying to save space.
 

·
Registered
Joined
·
248 Posts
Sine waves are a constant voltage to the coils, something they were never designed for, and you burnt the coils. 15 seconds is long enough for a sine wave when played loud, with time between tones for the coils to cool down.

With a ported enclosure you can smell the coils heating up from the ports and can back off, with sealed you have no warning.
Indeed at the dutch forum i am a member i seen this before,sub,s were note build to take the heat from 20 hz or below as a sinus.
10a 20 sec wil do the job,and you did.
Some members still wanna try, result burn,t voicecoil.
 

·
Registered
Joined
·
248 Posts
No chance of warranty then! I thought these where bulletproof... Guess nothing is.
I never blown a sub ,so i must say if you do it right,and know what to do NOT.
There will never be a probleem.
I also never overpower my sub,s ,my amp give,s RMS what the sub,s can take RMS.
 

·
Premium Member
Joined
·
5,869 Posts
WOW 2mins at 20hz.....thats rough. Just try music next time at 120dbs for 2mins. Can be any type of music. Although some music is very hard on subs but still not near as hard as sinewaves. But I still say you have the correct amount of power for these speakers. Just make sure you have the limiter set correctly also.
 

·
Registered
Joined
·
1,633 Posts
Guys, Is 2.3cubic internal volume too small for these subs? I was really trying to save space.
The size is fine, the only thing that worries me though if there is enough space behind the woofer for it to vent properly. If the motor can't vent properly it will over heat faster than normal. I usually like to have at least 3" from the pole vent to the back. A smaller box will get hot faster as well, normally not a problem with most material but a 2 minute 20hz sine wave can turn it into an oven.
 
1 - 20 of 57 Posts
Top