I'd being interseted to see what Steve says at sumpthump.com. It's clear on the site that it will work for both. Yet, I will have to agree, it may work, but may be smaller than the .6 advertised, hehe.

 

How loud do you want to be? If you want to be as loud as the peak at 100hz, but with more low end, it isn't going to happen with those drivers. The enclosure you have is extra efficient at producing that narrow frequency range at the expence of the rest of the range. When you put them in a box that will produce a relatively well ballanced bass frequency range, you will sacrifice the efficiency at 100 hz, thus less midbass, but you will have more low end bass. With speakers, it's always a trade off.

If you want that midbass loudness with the rest of the low frequencies brought up to appropriate levels, I would strongly recommend different drivers.

If you would be content with a little less midbass volume with good low bass, you can use the RF drivers but not with your current box. You would need to build something else to house them, I have a couple ideas if you want to go that route.

If you want to use that enclosure, you will need different drivers if you want to get decent low bass out of it, And if you are willing to mount the drivers magnet out, that will give you some additional driver options, although I think that kinda defeats the purpose of that enclosure. If you want me to help you here I will need some measurements and some pics to get a better understanding of what can be done and what will fit. I would also highly recommend an eq or dsp to attenuate that peak at 100hz (or where ever it ends up with the new drivers and maby a tuning adjustment, I guarentee you will still have a largish peak somewhere).

Your budget for this upgrade would also be a good thing to know for anyone trying to help.

 

A quote from subthump.com:

"Driver's side stealth enclosures are not intended for a convertible. A convertible has a hydraulic pump that operates the top and it sits right where this box would fit. The passenger box is what you need. See below!"

 

I'd try to build a new box with a "removeable" back panel, then play with an aperiodic membrane back panel setup using a square MDF ring, and some aluminum mesh pieces sandwiching some fiberglass insulation. Play with the density of the fiberglass to obtain the tuning you need. Before listening to it, I'd make sure you have a high-pass filter on it at like 20Hz to prevent tearing up a woofer. This setup will take more time to tune it properly, But I think it may be able to net you the best performance in such a small area.
Here's a link I found: http://www.audiogearreviews.com/tech...c_membrane.asp

Maybe Mike will chime in, as he may have experience with these.

 

This is a good Idea, but if you are only listening to the membrane, you will not be happy. You will need to either:
A) fire the drivers into the cabin.
B) open a reasonably large (6"x6" or larger) opening between the trunk and the cabin.

In either case you will, at best, approximate the sound from a properly dimensioned sealed box (not that that is a bad thing). The output of 3 woofers in a slightly larger aperiodic enclosure will be within a couple db as your 4 drivers in your current box if you block the vents and turn the woofers around and move the box away from the passthrough enough to let the sound into the cabin. If you like the way that sounds, build a box the way Snootch suggests (it should have a little bit more low bass) which will fit on the passthrough ledge. If you find this arrangement extremely lacking, then a sealed alignment is not for you with these drivers, period.

 

Ported boxes usually require lots of air space. I like sealed boxes best, but hey thats my opinion. I know you can put poly-fill (Cotton) in a sealed box and this lures the sub into believing there is more air space in the enclosuer, but not 100% sure for a ported enclosure. What are the subs, you are running?

 

Snootch's suggestion sounds way out of my league. Anything "I" do has to be limited to simple wood work, driver, wiring, or fiberfill mods. I'm not a fiberglass guy and that is way out of my area.

TA guy, I would like the enclosure to be at the level of a single, decent quality 10" properly set up in a coupe. My frame of references are:

- A 2002 Trailblazer with a single RF 12" sub, 02 model, powered by 150 watt sub channel of an Alpine V12 5 channel. Mounted in a 1.0 cuft sealed box.
- A 93 hardtop Formula that had both a dual 10" bandpass (Orions) and 200 watts rms (crappy) going to them. Eventually replaced by a single 10" JBL power sub driven by the same Alpine V12 type of 5th channel.

I think all three of these setups had similar sound quality and levels capabilities. Not enough to boom around and be heard for blocks, but enough to play any type of music at balanced levels, loud enough for almost anyone who wanted to listen to it for a long time. The most showing off I do of a system is to use the car as a boombox while outside drinking or whatever. Other than that I want it to sound good to me - I don't care about people outside.

My original thoughts were that 4 8" subs, driven by a real 400 watts RMS, should be well able to meet the sound balance and levels of the above single 10" / 12" setups.

I do realize 100% that dropping the top down is going to kill 90% of the bass output. My statements are not being skewed by that, they are including that as an assumption. So, I don't think I have unrealistic expectations, but I can tell you, when I sealed the box up this weekend, all of the output to the cabin, was gone. I mean just gone, even with the top up.

To some extent, you could "feel" that the subs were there, but almost none of the sound was making it up front. I suspect this is for a couple of reasons, mostly that the trunk doesn't reenforce sound well (all carpet), and there isn't a lot of path for the sound to make it to the cabin.

So this is my source of frustration. Sure, the box is really pretty loud at 80-100Hz, but I didn't go through the hassle of getting this much of a setup to not pick up 40-80hz range. I mean at this point I think I would've been a lot better off going ***** to the wall with my door drivers and their power, if that is where most of the actual sound is going to come from.

I ordered a set of infinity 952.7i's last night, along with a dynamat xtremem package for the doors. $130 shipped. I did this because I think the Apline 170's have a very harsh tweeter, and my doors are already rattling a little. I went with the infinities because they have a very smooth tweeter, are oversize, and are 2 ohm to take advantage of the memphis amp. I know they will solve the tweeter harshness, and am hoping the extra power, cone size, sensitivity, and sound deadening will really kick up my front midbass levels.

Components and kick-pods are beyond what I want to do with the car, so I think the infinities are a good fit for me from a price/performance perspective.
I am considering running the 4 memphis amp channels bi-amping them, and driving my rear Alpines off the head unit, if my sub box cannot be improved.

I have a lot of money tied up in the sub box and may well dump it if I can't figure something else out to make it carry it's weight.

I only dropped about $120 on the four rockford subs, so yes, I am willing to replace them. I also got the memphis amp off ebay for less than $150, so I could sell the whole setup off and be well ahead of the game.

I would still like a strong sub setup, whatever I do is somewhat limited by:

- The memphis 5th channel needs a 1 ohm load for good power. Only 200 watts into 2 ohms. 400 into 1 ohm.
- I'd like them to be usable in this box setup, with some light modding. I am willing to mount the drivers magnet out because that doesn't really impact the usable trunk space too much. But it is not preferred.
- I'd expect, with the top up, that the end product sound like a properly set up 10" in a coupe. I should be able to get plenty of 100hz on up volume from the front doors for my tastes, so I need the box for 40-80Hz.
- With the top down I have no real requirements but I'd like to be able to still hear a good difference vs. no subs. The way it is right now I have really almost nothing under 60Hz or so. Though above that it is nice and punchy.
- Maybe $75 per sub budget.

 

first off, with regards to aperiodic membrane.. AP needs to be treated like free-air. The membrane needs to vent outside of the vehicle, or into a large space that is completly sealed from the listening cabin. Very difficult to achieve this without major mods to the car.

It is correct that 4 8" subs should out perform or atleast keep up with a single 10" or even a 12" sub. But not if the box is not properly designed. Your subs need more air!

There are several things I can think of to get real bass in a convertible. Most involve alot of fabrication work.

The easiest route I would suggest is to remove the spare tire and jack, and use a 12" sub box there. Then built a little shelf for the top to rest on when it's down, keeping it out 2" off the rear deck of the car. This will give you a little bit of space for the sound to enter the car.

Other options include installing subs in the back seat area, in the doors, or kick panels.

 

I actually thought about the "lift" concept for the top. The problem is, when the top is fully down, there is quite a good bit of pressure forcing the glass down firmly on the shelf area. In order for this to work I think you'd have to limit the hydraulics with hard stops somehow, because as it is, the thing is really forced in place. I guess I can't say for sure, but if you put even a 1" spacer down I think you'd be putting the glass in danger. Have you tried this before? Maybe my top is a little off adjustment or something. Any links or images would be great!

I do appreciate everyone's feedback.

 

When you did this, did you pull the box out of the passthrough so that sound from the trunk could reach the cabin? If not, try that first, just let the box sit down in the trunk for this test, let me know haw that sounds to you. It will be missing the large peak so you will not have that punchiness with the top down, but it may provide adequate top up performance. It should have more low bass than before, especially in the sub 50hz range. If you are happy with the way that sounds, you will be able to mod your box to work.

The trunk will give you a good amount of sound reinforcment, not as good as a hatch of course, but it is not non-existant. You just need to be sure there is plenty of room for the sound in the trunk to reach the cabin.

I do know of some high excursion 8's (fitting your budget too) that wouldn't run out of excursion like the ones you have, but you would still have a peaky responce unless you eq it. If you choose not to eq it, the low end will still sound lacking because of the disproportionately loud midbass.

If you don't like she sound of the sealed box, and you have basic wood working skills and tools I would strongly suggest you build a different enclosure. Those RF drivers would soung great in the right rear seat delete ported box with the top up or down. A trunk well box would also work ok, of coures top down won't be as good, but you would still gain over 6db at 30 hz.

 

When I did the sealed box evaluation I pulled the sub box out and used the mounting cables I have to let it hang over the trunk well. So there was enough room to jam your arms in the opening and wave them around into the cabin area. The entire opening wasn't clear, but probably half of it was, about 2 square feet, at least. I figured this would be enough.

When it was installed like this, with the ports sealed up, very little output made it to the cabin. You could open the trunk and stand back there and it sounded pretty good, but literallly nothing made it back up front, or at least not enough that it wasn't overpowered by the damn alpines. It was quite ridiculous, I thought. The idea of having all that hardware back there and having to strain to hear it really irritates me. At least ported I get the monster punchy bass, which is ok for rock and stuff.

Maybe I should pick up a dB meter to work with, so everything I'm saying isn't so subjective.

I don't know about doing a rear seat box. I think I could live with a very small one, in place of the driver's side rear seat lower cushion, but I don't think that is enough space to work with, either. I think I'd be more inclined to give fabbing up a set of kick panels a shot. Can you fit 8" subs in modified kick panels?

I rented a mustang for a week that had the mach system or whatever with 8" woofers in the doors. That was actually pretty nice. The bass was artificially boomy, but if they can get that with factory stuff, using good aftermarket drivers and power would have me thinking 8" in the kicks could be good nuff.

I park the car all the time with the top down and I'd like to keep the attractions like that to an absolute minimum. Sometimes you mod a car so much you end up losing utility or the ability to enjoy it. I've made that mistake before and am not looking to repeat it. This car is strictly a toy, don't want to be worrying about it.

 

So new drivers and/or new enclosure it is. 2sqft is definitely adequate.

A rear seat delete box for those subs won't be super small, you would need .5-.6 cuft per sub minimum by the time you factor in driver displacement and port volume. If you want I will run the numbers later.

A trunk well box could be done easily enough, it is easier to build, and can be removable for when you need the space. Your current drivers would work well so you can do it on the cheap. It would also be hidden from view as an extra bonus.

The easy solution is a passenger side stealth, but I wouldn't ever use one due to having to sacrifice my spare, I'm just too old for that.

 

I have that 12" sealed enclosure from my Trailblazer. I'll try sitting that down in the trunk well and see how it sounds with the memphis amp and the divider removed.

When I first got the car I tried it and wasn't impressed, but come to think of it I probably left the divider in and had unrealistic expectations. Am I gonna have to dynamat the deck lid if I go this route?

I also can't live w/o a spare. There's no way in hell I'm leaving my car on a Detroit highway, lol.

 

Hey - tried following this, not sure what your current woofer size is or their quality. Presuming you still have the four 8" woofers and you apparently do not mind the cost of wood, screws or silicon, why not load them isobaric.

Put a box together that has a divider in the center with one 8" in a sealed configuration, in the "outer" woofer - you face it toward the 8" which is facing outwards and you have the other facing inward (you should be able to see the back of the outer woofer. Think of it as a giant piston of two woofers.

What this does? Gives cost you 3dB automatically. It also allows for space savings. It also gives you double the power handling. It also retains the quality of a sealed enclosure.

However, as far as the loss - take a look at this:

"Providing that you have enough power, two isobaric systems, which would take up the same amount of space as one single woofer, would have 3dB more output due to the increase in cone area. This can be used to your advantage when standard enclosures will not give enough SPL, by quadrupling the input power and quadrupling the number of drivers, you can attain 6dB more output." - http://www.mtx.com/caraudio/educatio...sureDesign.cfm

http://www.caraudiohelp.com/custom_c...udio_boxes.htm
http://www.audiogearreviews.com/tech...n/isobaric.asp
http://www.raysmith.co.uk/lets_make_bass.php

 

I would go with a 5th order band pass only using 2 - 8" in the correct airspace for maximum db response. If you MUST run 8 subs the only other configuration due to your lack of airspace would be a piggy back isobaric enclosure.

I would never do a free air enclosure. IMO they sound horrible and are a waste of time and money.

 

Woot, I'm glad you checked, I forgot too.

 

free-air setups can sound good, infact, they can sound very good. But you need to build it right, making sure the front of the speaker and rear of the speaker is completely sealed from the back, and that the back of the speaker has a large enough volume of air to vent into, either a large trunk, or outside of the vehicle.

Simply mounting a sub to a board and attatching the board somewhere in the car is not a free air setup.


yes, 8"s will fit in the kickpanels... But not without cutting some metal.

I know a guy with a LT1 Trans Am with 8" drivers in the kicks, and they are free-air to boot, they vent through the unibody, outside of the car. You don't need to do too much fiberglassing, but you do need to cut a good bit of sheet metal, which is a deal breaker for many.

mike

 

A sealed isobaric box is not a good option here, not for the output he is looking for. He would lose 6db (3 for the iso loading as he does not want to buy a new amp, so he would not be increasing the power to the drivers, and 3 for halving the radiating area, he would go from 4 to 2 drivers essentially). Even given the increased apparent volume of air seen by the woofer, the drivers would still be excursion limited in his current (or slightly modified) box at moderately low frequencies (~50hz). In a standard sealed box, the frequency responce below 70-80hz is essentially the same as his current setup so pretty much the same senario i have described above applies, except he would lose the huge peak too.

In any isobarically loaded system, the increased power handling is essentially useless as the system efficiency drops by the same amount, the net rusult being that you need twice the power in an iso loading to reach the same SPL as a standard loading (either ported or sealed).

Also he has already established that he dosen't care for these woofers sealed, so he would need a new ported box, which does present some options, You will still lose ~14db around your frequency peak, tapering to only a 1 or 2 db loss by 40 hz (at low power, you will gain volume at higher power levels due to the ported box not being excursion limited) It may even be possible to mod your existing box to accomplish this... maby... I would need some measurments and pics to get a better Idea of the feasibility of doing that. Or you could build a new box that would fit your passthrough ledge and accomidate this alignment. Definitely an option.

 

To my ears a free air setup sound terrible mainly because the lack of low end bass and a much higher resonant frequency. Also the Qtc is way too high making the sub sound uncontrolled or 'sloppy' because of the lack of control. It may be ok for some but defiantly not for the seasoned ear.

 

Then you have not heard a proper setup. My reference point is a home IB install, not automotive, but the same principles should apply. I agree that the average automotive sub will sound poor in an IB install, but using the right sub, it can sound beautiful. I don't dobut you have a seasoned ear, I'm just saying you haven't heard a setup put together by someone who knows what they are doing.