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Enclosure size confusion

Posted: Fri Jun 16, 2017 2:47 am
by Nissanrules
I have a pair of 15" Phoenix Gold Titanium Ti15D (each with 2x 4ohm) I bought new back in 2003. I'll feed them with a the pair of R500X1D Rockford Prime amps. I want to install them in a sealed enclosure. My main question is what volume does my enclosure needs to be? How does polyester filling is taken into account? Is there an advantage to partition the enclosure so each sub is separated? The Phoenix Gold datasheet states 1.25ft3 (musical) and 1.75ft3 (SPL). However, most subwoofer online enclosure calculators are giving me a volume of 6.5-7.0ft3 per sub. That a world of difference! I look forward good musicality (a lot of metal music Rob Zombie, Metallica, Korn). My parameters are FS 26.21Hz Qms 9.26; Qes 0.594; Qts 0.558; Vas 114.63 liters (4.0259ft3), Sd 792 cm2 (122.76in2). I install this into an '84 Fiero... kidding :mrgreen: , it's a 2006 Nissan X-Trail, so I have enough room.

Anyone help me point in the good direction?

Re: Enclosure size confusion

Posted: Fri Jun 16, 2017 8:20 am
by ttocs
something is wrong with the online calculators but I am not sure how your going about trying to find the recomended volume since it is given already. The calculators are more for ported enclosures if I am not mistaken? If you want SQ try to get as close to 1.25 if you want spl go closer to 1.75.

Re: Enclosure size confusion

Posted: Fri Jun 16, 2017 9:10 am
by Nissanrules
Ok good for the size. What about the poly filling and partition inside the box?

Re: Enclosure size confusion

Posted: Fri Jun 16, 2017 9:47 am
by ttocs
separating the enclosure is helpful if you blow a sub, one can keep playing in the correct airspace. The only time I have used polyfill was when I was not happy with out it sounded in hopes of correcting some error. Its cheap and easy to try and can change the sound, some like it and some do not.

Re: Enclosure size confusion

Posted: Fri Jun 16, 2017 11:08 am
by keith2728
Separate chambers for sure when using multiple channels. I think it makes it easier to tune. I have played with Polly fill. Never heard a difference. I think it's a myth.

Re: Enclosure size confusion

Posted: Fri Jun 16, 2017 11:45 am
by ttocs
I can't remember where I heard it and now wonder if its true but I thought I heard that it is slightly louder when the subs share an enclosure?

Re: Enclosure size confusion

Posted: Mon Jun 19, 2017 1:32 am
by Eric D
Most enclosure calculators are for use with subwoofers in a large room environment. When you put a sub in a small space like a vehicle, the calculation needs to be different. In this small space, the volume of the vehicle's interior becomes a large influence on what the subwoofer will do.

Re: Enclosure size confusion

Posted: Wed Jun 21, 2017 1:13 pm
by smgreen20
Also note, that back in those days PG was notorious for skewing their numbers, getting them crossed. I think that's the case here. Typically a smaller enclosure will be your SPL and a larger one for musical. I'm willing to bet those got crossed.

Polyfill mostly benefits sealed boxes, but does have some effect on ported.

With each sub having its own amp I would definitely go with separate chambers.

Back in the 90's I was told the same thing about being louder sharing the same air space.if it's ture or not, I've never noticed.

Re: Enclosure size confusion

Posted: Wed Jun 21, 2017 7:05 pm
by Nissanrules
Thank you very much for your replies. It's much appreciated. Based on your comments, I'll be using 1.5cu.ft. per sub; that'll make me fall in the middle of the SQ vs SPL volumes specified by PG and won't be an issue if PG crossed the values in their spec. I'll split the enclosure in two sepatated sections, the partition acting at the same time as a brace. I'm eager to get this built but it won't happen before a month or so. I'll post pictures of the results when I'm done!