A Couple Fi Q15 Questions ?

[Fish Chris]

First off, if I were to run a couple of Fi Q15's setup strictly for SQ {I mean so they would sound tight, and clean, with no ringing or boominess} what would your guess be, for the optimum cubic footage per sub ? Oh... and yes, ported for sure !

The Fi website lists the cubes for these subs at 2.8 to 4 cubes each, and tuned at 28hz to 33 hz. I think I can do 8 cubes for the pair if that would be best.

BTW, I really like the idea of that LOW tuning. The way I see it, for an SQ type of system, these 15"s will probably have more than enough output (a lot of SQ freaks would probably say TOO much) for the rest of my system to keep up with, anyway. But I like a lot of really low bass. In other words, I DO want my system to be really clean. But I'm not too concerned with whether some SQ freak thinks its not balanced ;-)

My other concern is, I can only give these subs 350 wts rms, or 460 wts rms each.... depending on whether I set them up to present a 2 ohm, or a 1 ohm load to my amp. I know this is a lot less than these speakers can handle..... But I am talking about 700 or 935 "real" watts (birth sheet ratings) from the sub channel of my RF Power 1000. I know of one guy who is running four 18"s off of the sub channel of this same amp, and he says it slams..... but without actually hearing it, who knows ?

Anybody ?

Thank you,

Fish

[Neel]

personally i would go with a single sub and fully power it then have a two subs that were under powered. I used to have a 12" Q and i gave it about 1200 watts with an Ed nine.1 and it sounded great in a box 2.4cu tuned at 34hz. Then i have also heard it on a sundown 1500 in a 2.2cu box tuned at 32hz and it got plenty loud. From my experience the sub will handle more then its rms power rating both thermally and mechanically. If you want it to be fairly tonal i would probably stick to the specs on the site and tune it around 32-34hz. You can always use an eq to tame the response of the sub , so dont think that once you have built the box your sub response will be set in stone.

[Fish Chris]

First off Neel, thank you for the response.

As for going with only one 15" sub.... I was afraid somebody might say that. Ya' see, the thing is, I already have two brand new ED 13Kv.2's (12") sitting right here in my closet. Those will be used with my initial setup. And who knows..... Maybe (just maybe) those will end up giving me even more ultra-low wind blowing bass than I even want..... but I'm kind of doubting it. I'm also thinking that even if they do give me enough ultra-low bass 'initially'...... I'm very likely to destroy them with some low bass test CD or something..... and then I will need a new sub(s) whether I had liked the ED's or not, anyway.

So my thing is, one 15" sub moves less air than two 12"s {given the same X-max}.... of course I know those Fi Q's have a fat 27mm's of X-max ! .....quite a bit more than the ED's, so maybe....

Anyway, I know I keep saying > SQ..... and I think going with only one sub, at twice the power might be a bit cleaner, but two subs with the power divided, will definately give me more air movement. Not sure of the cost in clarity.

I have heard that to double the power to 1 sub, will give you an increase of aprox 3 db's

While doubling the number of subs will give you an aprox increase of 6 db's..... oh but then your cutting the power to each in half ? Hmmmm.

I dunno.

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So, if 1 sub is superior, how about 1 Fi Q18 ? :-) .........I'm just still not completely convinced that it could play as tight, and clean as a 10" or 12" sub, regardless of the enclosure. Even if it sounds 'good' (which I know that it could) it would have to sound a little 'different'...... Hmmmmm.

Too many freaking choices :-)

Peace,

Fish

PS *IMPORTANT*

Neel, please understand that even if I went with two 15"s instead of one, I'd still be able to give "each" of the subs all the airspace they needed to perform at their best.

I have to believe that a LOT of people have run (just for example) two 15"s in not enough airspace, and they sounded like crap. So then they went with just one 15", with plenty of airspace, and it sounded great ! So then, they "mistakenly" took this to mean > one sub with twice the power, sounds better than two subs with the power divided..... When in reality, regardless of the number of subs, or the amount of power involved, any combination of the above will sound better in the right enclosure, and worse in the wrong enclosure.

[Moti]

You can possibly call fi on the minimum rms you can give to the woofer. Personally I think 400ish watts to a woofer wouldn't cut it.

I think your best option is to get a single woofer and feed it proper power. Oh an the 18's play low and sound amazing. If they're set up in the proper box, with a decent amount of power. People that typically complain put them into a minimum spec box with less wattage. You would only want to small box a 18 if you're going to be running more than rms. An a bigger box if you want efficeny at rms. Don't get it wrong 18's hit hard and tight.

Personally with 900ish watts. I would go with a Fi 15 or 18 SSD with a copper coil. If setup right they will knock pretty hard. You may want to put them in a bigger box, they will be a lot louder and efficient with that amount power you have.

[Fish Chris]

Right on Moti. I think I will have to talk with the guys at Fi here soon.

Yea', like I was saying, whether I went with one or two 15"s... or even one 18", I can give them all the space that Fi recommends. I have an F150 Supercab with the rear seats ripped out :-)

Hey BTW, I was turned on to this web page {written by guys who obviously know a LOT more than I do}

http://www.audiopulse.com/know-how/subwoof...out-subwoofers/

And I found it quite interesting when they said >

myth #14 It’s a bigger driver, then I need a bigger amp;

Often times larger drivers require less amplification, that’s sort of the idea. The concept of bigger woofers need more power is not always true and plays right into the ever progressing misconception of car audio. What you should consider is the efficiency of the subwoofer. Efficiency will literally tell you how much acoustic output you will get given an amount of power (assuming linear limits of course). If the driver is bigger, has a larger motor and has a higher sensitivity, there is no mystery about it, you are going to get more SPL with the same amplifier provided the impedance is similar and the amplifier can produce high voltage at impedance peaks when the driver naturally draws very little current for a narrow range. If a driver is more efficient and has a larger voice coil, well you just got your cake and you can now eat it. Not only will it be louder, but it will have less thermal compression and ultimately more sound provided all else is equal (but such is not usually not the case). It’s often difficult to make voice coils larger and increase sensitivity too. This usually requires very large motors and expense. Sensitivity is most easily achieved by weight reduction usually from the cone surround and voice coil. Sensitivity is often a trade off of xmax and thermal compression limits.

.....then, somewhere else I recently read (sorry, now I can't find it, but anyway) that a speaker which boasts of being able to handle 1000wts rms, will be only slightly less loud with 500wts, but will be much less likely to overheat, or completely fail. Also, that one might be amazed at how much solid. clean bass that same sub might produce with only 250 true wts rms.

It's the whole "theory of diminishing returns, in reverse" :-)

In any case, yes, I will talk with Fi and see what they think......

Peace,

Fish