47 replies to this topic

[shizzle]

Heya,

I am going to be installing a JBL GTi 15" in an IB setup in the boot of my car, with some Oz Matrix mids up front, and some Dyn tweeters.

Now, I plan on crossing the 15" really low, probably around 50hz or so, will have to fiddle once it is in.
I can play the Oz's down that low, but they will not perform that great on the lower frequency's.

I have the advantage of being able to fabricate (somehow) a box under the dash.
I want to put a small sub in there, and use it to fill in between the sub and the mids (probably cross it 50hz to around 150hz or so, again, fiddle once it is installed).

Does anyone have any advice on this? Is it a good idea, or does it have flaws. Are there better ways of filling in. I know Gary Biggs did this to much success, also using GTI's (2 off) that played REALLY low (I think he crossed his at 15hz or something) and used a 10" up front to fill in between the mids and sub.

Also, any advice on drivers? I was looking on some of the Morel Elate (9" or 10" drivers). I suppose Peerless and the like should also be looked into?

Thanks in advance, any help is appreciated.
Cheers,

Edited by shizzle, 28 March 2009 - 07:33 PM.

[SydJazz]

you will want a smallish subwoofer for that point between the midbass and super low sub-bass. common-size midbass drivers are good for midbass as long as they are good quality and properly sound deadened. so getting a larger midbass driver to get lower may only get you a few more hz lower. it really depends on your crossover points and if there are any gaps in the frequency spectrum. am i thinking correctly in what youre trying to achieve? what mids specifically are you using?

Edited by SydJazz, 28 March 2009 - 09:32 PM.

[shizzle]

heya,

the mids I am using are the Oz Audio Matrix Elite.
My thinking is if I am crossing my sub at abound 50hz or so, in IB, it is going to play LOW.
My mids would not be able to really do any frequencies below 80hz any justice, hence the need for something inbetween.

Hope that came across ok, just had 3/4 bottle of vodka

[SydJazz]

yea you may be looking for maybe a 8-10 inch sub. keeping the enclosure sealed to reduce its size. the enclosure could then be tuned to a higher frequency to match what you need. you basically need to say "how low can my midbass play cleanly" and "how low do i want the 15 to play". then you can look at the range you need to fill in.

are your midbass woofers in sealed sound deadened doors? they can help with the lower frequencies. a small sub for between 50hz and 80-100hz shouldnt be too much of a problem. just make sure to get the numbers right. and also get the crossovers correct, as you have two parts to your sub-bass now.

[shizzle]

yo!

My mids will be in kickpanels, but with no 'enclosure' to speak of (ie, not a defined volume).

I think the best would be to install my 15", and my 6.5"';s and see from there if I need some fill. Perhpas the mids could surprise me, I will be feeding them 200w of clean power, so they may actually soind real good

Thanks for the reply .

[Pulse-R]

a 5" or 6" mid will only really play down to 150Hz or so in a "non-enclosed" space before cancellation or the rear-wave becomes a problem.

in a 2-way set you need to get the mid a fair bit on-axis for best results, or you lose tonality pretty quick.

an 8" or 10" will need about 20+ litres to play down to 50Hz properly (and have a Fs ~1 octave lower than that!) which really limits your options for an enclosure and a woofer.

I think you'd be better off to get a good 4" or 5" mid to do 150Hz+ and then have a dedicated midbass.

but hey! just do it, and see what happens - practice and experimentation will give you the most accurate advice.

[shizzle]

thanks for the reply Pulse-R.

I can quite comfortable fit a 20L enclosure under my dash (you have to love old cars, so little behind their dash's )

Unfortunately I already have my mids, and will have a spare amp to run a 10" nicely, so the cheapest option could be to just get a 10" and try it.

Thanks for the advice though, always appreciated.

[Pulse-R]

easy-peasy then

[broadz]

drifte has a pair of elate 9s, and i have a single elate 10 if suitable

[shizzle]

yup, they are the 2 I have in mind mate, with yours being top of my list

[br85]

The peerless SLS8 WOULD be great (if not the absolute best, and at a FREAKING awesome price too), but it would definately need all 20L (and some if possible) and some rockwool or higher than R10 fibreglass insulation to get to 50hz without a good eq. Pretty much the s4!t if you don't need it to play higher than 250/315hz. With most other options you're going to pay money for the ability to play something you don't need it for i.e. waste. SLS8's slam.

[Gonadman2]

br85, on Mar 29 2009, 11:07 AM, said:

SLS8's slam.

Not really, they are ok but they aren't great. I have a pair at the moment and they are too easy to pole in free air. I will be trying sealed enclosures at a later date and hope they play lower with more control than free air.

[Luke352]

Personally I'm of the opinion you will need a 10" or preferably a 12" to fill in between 150hz and 50hz, think of it like this if two 6.5" drivers struggle to get far below 80hz then how is a single 8" driver that in most cases has less cone area then the combined cone area of two 6.5" drivers going to be any better then two 6.5" drivers. Yes the 8" will most likely have more xmax but your still down cone area.

So a pair of 8's can generally get pretty low so we'll call that our min target performance, two 8's will have a combined cone area of around 420-450cm sq, a 10" driver is generally between 360-400cm sq so we are still down in cone area compared to our min target performance but we probably regain some, if not all that lost cone area due to the most likely (not definite) extra excursion the larger driver is capable off.

So a 10" driver will do it but a 12" driver (480-520cm sq) if you can fit it would be great as you know it will have plenty of reserve output so you won't be driving it too hard.

As the SPL boys say, "Cone area is king" and it's true!

Edited by Luke352, 29 March 2009 - 01:02 PM.

[hoogstehond]

Pulse-R, on Mar 29 2009, 09:15 AM, said:

a 5" or 6" mid will only really play down to 150Hz or so in a "non-enclosed" space before cancellation or the rear-wave becomes a problem.

Bollocks.

Ask anyone who has heard this.

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[shizzle]

I think if you are going for all out SPL, cone area IS king (with xmax and other things being a hge factor of course).

I am looking more for linear frequency response, and am not too worried about output. As long as the speaker can get to mild volumes within the freq. range I am after, I am quite happy.

A 12" probably would be better, but I recon a 10" would be just as good for this application, especially seeing as though I can't put a 12" under my dash

But I will look more into it (including the SLS8), and do some research to see what the best option would be.

Thanks again for the replies, always helpful.

Cya