small amp on four 15s will it overheat?

[Bazzheadnorway]

i have a relatively small monoblock JBL751ez and plan on hooking it up with four single voice coil 8ohm 15s in parallel = 2ohms right?

my question is, if i have this plugged in 2ohms will it overheat over time like a ticking bomb or will it only heat up when i turn it up and then i could turn it down again and let it cool down?

the amp is "stable" at 2ohms, says 2ohms minimum so //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Click to read more...

 

[Popwarhomie 5,000+ posts]

It is designed to run at 2 ohms. So no it will not had a issue. Just set gains correctly.

 

[Boomin_tahoe 5,000+ posts]

You should be fine.

 

[Buick_66]

I would say your main concern would be clipping. Adjust gains so the sound is not distorted and you'll be fine. Probably worth upgrading when you have the funds to move those woofers to their full potential. With this set up you are only getting 185 watts (max)to each sub (which I will assume can handle 500 each or more...give or take)

 

[bigblank69 10+ year member]

751's are underrated... the 500 series will produce around 800 watts clean (Mine did 864) so I would expect a 751 to get closer to 1k. The amp will be fine. What subs are you planning on using?

 

[Bazzheadnorway]

The subs that im using are cerwin vegas, they are from their XLS 215 speakers, kindof almost a pa woofer but actually more like a typical home audio woofer, deacent excursion and yes like Buick_86 said they can handle much more.

I currently have two of these in the car in a 5ft3 box tuned to 21hz and it works like a charm baring in mind that the woofers are more 50hz ish subs, it brings the lows well.

Anyway ithink im gonna try to add two more sometime soon, and seriously consider buying another amp or what?

 

[Boomin_tahoe 5,000+ posts]

Tuned to 21Hz?!?!?!

pics of said extremely low tuned enclosure...

 

[Bazzheadnorway]

Here it is, 4" wide and 30" (29,8ish) long x2

Think it is actually tune 20,5hz. Subs are inverted

 

[Boomin_tahoe 5,000+ posts]

Here it is, 4" wide and 30" (29,8ish) long x2
Think it is actually tune 20,5hz. Subs are inverted

Holy cow man....had trouble cutting that circle with the jigsaw?! http://www.partsexpress.com has a jasperjig to make perfect circles every time.

Those ports aren't that long....was expecting to see something insanely longer....lower tuning requires longer vent length.

 

[Bazzheadnorway]

Holy cow man....had trouble cutting that circle with the jigsaw?! http://www.partsexpress.com has a jasperjig to make perfect circles every time.
Those ports aren't that long....was expecting to see something insanely longer....lower tuning requires longer vent length.

Yeah first box ive built and i didnt have a jigsaw thats why its all messed up.

However the ports are 10cm wide and 75cm long if that makes more sence, about 4" and 29/30" in inches. The box is 5ft3 and remember those holes are 15" not 10 or 12".

Will post møre pics soon

 

[Bazzheadnorway]

Yeah first box ive built and i didnt have a jigsaw thats why its all messed up.
However the ports are 10cm wide and 75cm long if that makes more sence, about 4" and 29/30" in inches. The box is 5ft3 and remember those holes are 15" not 10 or 12".

Will post møre pics soon

Here you go //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif)

 

[Jeffdachef 5,000+ posts]

Holy cow man....had trouble cutting that circle with the jigsaw?! http://www.partsexpress.com has a jasperjig to make perfect circles every time.
Those ports aren't that long....was expecting to see something insanely longer....lower tuning requires longer vent length.

bro... Norway lmao gotta check their country before recommending USA based sh*t, gotta grasp the concept of what it would cost shipping and import/customs costs for people in other countries..

There's three ways to get lower tuning. Longer length is only one of them. More airspace is the other and the third way is shrinking port area. Looks like he's using 4 inch ports

 

[Jeffdachef 5,000+ posts]

Yeah first box ive built and i didnt have a jigsaw thats why its all messed up.
However the ports are 10cm wide and 75cm long if that makes more sence, about 4" and 29/30" in inches. The box is 5ft3 and remember those holes are 15" not 10 or 12".

Will post møre pics soon

usually a box for two 15s is around 6 to 8 cubic feet net and using a single 8 inch port or dual 6 inch ports. Tuning to 21 hz isnt doing you any favors output wise either, after a certain point you are just giving up output for zero gains down low as in if you were tuned to 25hz-28hz, you'll just be overall louder everywhere else and still be just as loud down low.

 

[Bazzheadnorway]

usually a box for two 15s is around 6 to 8 cubic feet net and using a single 8 inch port or dual 6 inch ports. Tuning to 21 hz isnt doing you any favors output wise either, after a certain point you are just giving up output for zero gains down low as in if you were tuned to 25hz-28hz, you'll just be overall louder everywhere else and still be just as loud down low.

Yeah im quite limited on space, it is in a nissan leaf haha, two 105ah batteries run in parallel behind the back seats hooked up to the JBL monoblock, had to remove the oem Bose "subwoofer" to free space for the batteries.

The plan with the box was actually to have four 4"/30" ports and tuning about 35hz, but i tried with just two at first and i was quite surprised how insanly low it played ..went on the pc and calculated (like the pic above) there was a big surprise when i found out that the box was actually tuned to 20.5hz with just 2 port (iknow why but still surprising) no wonder that the lows are almost a little louder then the 37++ hz. Yet another surprise when i found out i can hear all the way down to 17hz hehe.

The port velocity / port noise was not as bad as i thought, can barely heat them probaly becouse of where they are placed with the back seat acting as an absorber of some sort

But im allways looking for more output so ithink i'll try with adding just one more sometime in the near future. See if a little higher tuning + less port noise is the next "upgrade"

 

[Boomin_tahoe 5,000+ posts]

bro... Norway lmao gotta check their country before recommending USA based sh*t, gotta grasp the concept of what it would cost shipping and import/customs costs for people in other countries..
There's three ways to get lower tuning. Longer length is only one of them. More airspace is the other and the third way is shrinking port area. Looks like he's using 4 inch ports

Yes I see that he's in Norway....also says in his screen name. C'mon Jeff....I'm not that dumb, as others on here may have a different approach on that. Also he did mention he uses 4" ports.

He can also take that link I provided and search for that perfect circle tool in his country. Never was my intention for him to buy....