Single sub quest…

Hi folks. I swear I searched, but can’t find an answer for my question…

My current sound system isn’t bad, but my subs do not perform well.

Quick details:
JVC KW-Z1000W head unit
Kicker CXA660.5 amplifier
Alpine R-Series 6x9 separates front doors
Alpine R-Series 6.5” coax rear doors
(2) Kicker Comp RT 8” in a small sealed box.


Amplifier is dialed and tuned with some oscilloscope type instrument that showed where distortion started. Gains set accordingly. Signal from my HU is really clean, all the way to full output.

My door speakers do everything I want. They’re tight and clean as loud as I ever want it.

The subs, however, cannot come close to keeping up. They do pretty well in the mid to upper range, but they ain’t gonna dig deep at any decent level. I would like to fix this…


First thought that comes to mind is ditching the RT 8s and going with a good single 10” or 12” sub in a ported enclosure. Ideally, I’d like a 12” JL 12TW3-D4. I’d also like a box that is tuned to ~33hz. 31-36 would be acceptable. Looking for 1.0 to 1.25 ft3. With my amplifier delivering 300w at 2-ohm mono, I think I’ll be fine with this driver. Worst case, I add a dedicated sub amplifier, but I’d prefer to keep what I have if it’ll work well.

Does anyone know of such an enclosure? Or will we be building one?

 

https://www.mtiacoustics.net/all-en...-Seat-Enclosure/p/355304464/category=76059029

 

Thanks for the link. That looks like a fantastic fit, but sure adds up in a hurry! I’d be in the $450 range with shipping calculated. I may give them a call and see what frequency it’s tuned to. For that kind of coin, it would need to be right for me.

 

Gately audio would be another option. Both companies make some really good stuff. Skyhighcaraudio usually has some good Black Friday deals. Had free shipping on my Gately box from them. It was around 600 dollars but a beast of a box.

 

I am in the same boat and have been considering this Alpine sub/box unit, no experience with it, but looks like it should meet your specs. Also it is a 2 Ohm unit. Reviews on Amazon show that it fits behind the seat of a Crewmax.

https://www.crutchfield.com/p_500SBTS10V/Alpine-SBT-S10V.html

 

Curious what the tuned frequency is on that box.

 

Yeah, I looked for that as well and couldn't find any info.

 

I’m not good at much, but comparing the looks of the port and seeing the dimensions of the box, something doesn’t look quite right. Without some real data from the manufacturer stating what the performance specs are, it looks like one to pass on.

I can see the 3/8” MDF for the sides, top, and bottom since the pieces are small enough that I bet deflection isn’t a big deal. The front is 3/4”, but I can’t believe the biggest panel (the back) is 3/8”. I’d imagine that will flex all over the place.

 

If you look at other pics, see the 3D view in Amazon, the back looks like 3/4" as well. I found the spec if you go to the sub manual, F3 = 31 Hz and Fb = 34Hz @ 1.02 ft^3 ported, which is what I calculated the volume of this box as, and I can't imagine Alpine did not design the box to match this sub's specs exactly.

https://pdf.crutchfieldonline.com/ImageBank/v20140923111700/Manuals/500/500SBTS10V.PDF

I think I am going to give this one a go, on sale now for $240, the sub alone is $220.

 

Give it a shot and please report back on how it performs! Would be a really nice package if it works as well as you’d hope.

 

Chad



In a Crewmax.
If you want loud there are really 3 options.

option 1 take back seat out and throw in 4 12's result will be stupid loud.

option 2 fiberglass enclosure from T A C O tune. A little on the high side for just the box.

Option 3 Gately audio They will sell just the seat brackets I think they are just over $500 for the hardware that will make it to where you can build an enclosure that you can get the air space needed to get loud. If I change over from my current sub setup this is the option I am going to go with.

It takes space and power to make bass. No way around it.


Before you spend any money on new gear. There is nothing wrong with the Kicker comp RT8 you have now. You just need to give it some air space to work with.
Build a box for just 1 of them in about 1cf net space with the box tuned to around 36hz and see what it does. It might get you what you want for just a little time and less than $40 in material. Many videos on YouTube on how to build a Basic wedge box.

I watched someone flex the roof on a SUV with one gbw 8inch Blaupunkt $30 sub from Walmart in the correct box. I think he had it in about .7 cf at 34-38 hz if I remember correct.

You can go to subbox pro and design some basic calculations and port tuning.


If you want more than the kicker 8's can do.
Sound box makes a dual 12 inch box for the crewmax. online for $144 on Amazon
They also make a single sub option for around $85 on ebay.
The pioneer ts-A3000ls4 12 inch sub seems to work well in this enclosure. You can get the pioneer for $110 each online, walmart, amazon, ebay.
If you go the dual 12's you will need more power than the kicker amp you have now.

 

Thanks for the great response!

More than loud, I’m wanting range. My pair of 8s gets plenty loud, but the enclosure is stupid.

I’ll look into the options you’ve listed. Thanks again!

 

James @ tech12volts has probably done more JL's in Tundra's than anyone...... i'd surely contact him..... he did my enclosure for 2 10s and even sent 2 JL 10s for me to compare to the Arc 10s I wanted so i could see if i liked one over the other..... the Arc's won out for me...... he sells both

 

Been trying to reach him via email, without success.

 

Phone call might be better

 

Tried that too. My quest continues, as I’m losing faith in James. I’ll give him a few more days to answer a couple simple questions, but not much more.


From what I’m gathering, his enclosure is in the 1.1 ft3 range. I’ve asked, but haven’t got an answer. More than volume, I want to know what his ported box is tuned to. In my humble opinion, it’s pointless if the tuning isn’t what I want. That doesn’t mean it’s bad! This is a somewhat subjective deal, and what sounds good to me may not be for another.


Really hoping to hear back, as I know he’s got a solid following on here. I know it can be tough to answer all the questions, but it’s frustrating that I took the time to generate an email with a short list of questions. All I’ve received back is a quick one or two sentence response that provided an option that he sells, but no answers to my questions…

Sorry, rant over.


Edit: Well, I did hear back that the box is tuned to 34hz. No volume info, but looks like it’s about as big as you can get without a formed fiberglass enclosure.

 

The soundbox is on the dual 12 inch I think is 1.98 cf. only problem is the box is limited to shallow mount subs

The Gatley Audio option I feel is better than the fiberglass option.

I would buy just the seat brackets from Gately Audio, build the box yourself if you can.

When I get tired of my dual 8,s I will make the change to gatley setup. probably run three tens ported in decent air space ported low

 

So… 99% of the time I am a fan of vented boxes. I’ve built piles of them for home and car audio, measured even larger piles of drivers’ TS parameters, and modeled a bazillion drivers in WinISD, SoundEasy, etc. Usually, a modern driver wants a vented box.

However, neither my car nor my home theater utilize vented subwoofer enclosures currently. Weird, I know. Vented boxes are more efficient and get you an additional octave of extension as the resonance of the vent is what’s producing bass below the drivers natural rolloff. Above that vented frequency, the sub behaves as if it’s in a sealed box.

They also come with some inherent issues like the vent itself creating it’s own unwanted resonance elsewhere in the audio spectrum, and phasing issues. The former became a problem with my home theater sub which is tuned to an f3 of 17 hz; the vent length and size required was producing a resonant peak at 110 hz even though the amp filter was set at 80 hz. That clashed with a room resonance at the same frequency and overpowered the listener at the frequency, causing the low bass to actually seem quieter. I fixed it by rebuilding the enclosures to a sealed box and tuning them passive radiators (most of which don’t actually provide useable TS parameters). The box enclosure volume dropped in half and the overall enclosure size decreased by almost a third due to the large vent. And I was able to keep the same f3 tuning of 17 hz without the resonant peak OR phase issues. My DSP changed dramatically and I was able to cut the power in half to get the same output. My Crown XLS laughs at me now. And the subs laugh at the Crown…

My truck, on the other hand, was having the other issue - due to the extremely small cabin space, the vented enclosure was causing such bad phase delay issues that the lower bass was extremely inconsistent and seemed almost non existent at some frequencies. I tuned a pioneer shallow mount 12” to 25 hz in a ~1.2 cu ft enclosure. I fought it for months; the upper bass was too powerful and almost droned. I had to turn the low pass to 63hz or even 50 hz to get it to flatten out. I was baffled.

A vented enclosure has extra meat below the driver’s sealed in box tuning frequency (most drivers in a car sized enclosure are going to be around 50-60 hz) so an octave below that is 30 hz. Perfect. Plus, you get cabin gain, which is basically a free bass boost below a certain frequency depending on the size of the cabin. In a truck, it’s usually around 80hz. So the bass should get louder as it gets lower. More perfect. But my truck system sucked.

A neighbor kid asked me to help them build box and install a sub in their RAV4, so I obliged. They wanted something slim in the recessed floor space. Originally, we were going to go with a vented 8 but I had another pioneer shallow 12 on the shelf that at one time I was planning on adding to my truck but ran out of space, so I decided that would be the ticket. For simplicity sake, I went with a sealed box I spec’d from my own WinISD models (not too far off of factory spec) with some good bracing. That thing THUMPED!! I was blown away!

That night, I went back to my shop and sealed up the very same box I was using vented (that modeled with an extra 2-3 db of bass from 25 to 50 hz than the sealed box). And guess what - it THUMPED! It was awesome! The vented box was shifting phase so much that I was getting destructive interference between the subs and mains.

A short while later, I finally swapped in a mono amp to power it rather than using two channels of my 4 channel amp to power it and found that the Pioneer didn’t like th extra wattage. So I went rummaging through my pile of subs to see what would fit under the seat.

After three subs, two wasted prototype boxes, and a pile of sawdust, I defeatedly pulled out the old beater sealed box that previously housed my Pioneer flat 12 and reworked the opening to fit an NVX SMW12. I didn’t have high hopes for the lowly NVX after trying to shoehorn the likes of Kenwood and he at hitter Subdown Audio into the truck, but I plodded on nonetheless. I wired the single sub to 2 ohms, pushing an extra couple hundred watts from my class d mono amp, thinking if I accidentally blew that sub, it wouldn’t be the end of the world. I just needed some decent tunes. I wired it up a and fired it up and…

WHOAH. That’s an NVX sub? A FLAT nvx sub?? It sounds great with better musicality than any of the other flat subs I had tried (as a side note, I generally don’t like flat subs except as a last resort, as I’ve found very few that sound musical instead of sounding like a farting tuba in the deep end of the pool). This thing was totally different. And in a simple sealed box, nonetheless. I’ve also cranked it up pretty loud and it hits hard and deep.

So what wa star pint of all that blathering? For $100 and a little bit of time (if you can build a simple sealed enclosure) try adding some displacement via a larger driver. Usually I recommend the opposite, as a large driver in a small box generally sounds worse than a small driver in a correctly sized box. But in this case, then numbers worked in my favor. And it was simple - almost shamefully simple - as here is what my better home theater boxes look like inside…

 

sometimes the things that make no sense surprise us...... there's a few shallow subs that no they "aren't the same" but can be very surprising..... the Arc Audio are good but more than double that NVX... Stereo Integrity BM's but WAY more than your NVX..... there's a few Dayton offerings that might come closer to the NVX in price and performance for said price..... I'd love to see if a single 12 Adire Audio Koda could be shoehorned behind the seat..... GOOD SQ level shallow subs get pricy QUICK

 

All good choices. I haven’t heard the Arc Audio but it wasn’t available in the configuration I wanted when I was shopping. The price on the Daytons have gone up. Adire gear is awesome but definitely gona be a struggle to fit it. And as for the SI BM… well, he’s had my money for almost a year and still no Bm11

 

good to hear the Adire name.

they are some of the best units out there.

 

That a bummer on that BM..... i was under the impression they are "now in stock"...... I actually live about 5 miles from SI and Sundown....

 

just went and checked looks like eta is now Dec......

 

Yup. Wouldn’t be surprised if it gets pushed to March. Unfortunately.

I really was surprised by the NVX. I expected very little from them and bought a pair on a whim because they modeled ok. Though, honesty, a lot of their subs have surprised me. These hit harder than I expected AND sound good.

At one point I had aspirations to shoehorn a couple of Dayton Epique 7” subwoofers in to the truck. I was going to have them rear firing but was having issues with magnet clearance. Basically, the motor structure is pretty much the same size as the driver cutout. They are clean and take way more power than they should above 30 hz.

 

I just got an email from Stereo Integrity yesterday; ‘Your Order Has Been Received!’. Hopefully that means they will be shipping the BM 11 soon cuz that order was place many moons ago. Website still says preorder, though.

 

Chad, I had another thought as I read through your post again. Sub amps are often set 3db past distortion level. Depending on what tool you are using to set your gains, you may be simply under powering those 8’s. I know that sounds funny to purposely run them to clipping, but there are a few reasons why that’s acceptable and often industry practice.

First, our ears are less sensitive to bass tones, meaning bass needs to be louder to sound ‘as loud’ as everything else. Typically, we use four or more times the power for the subs as we do the main speakers; double the total power to the rest of your speakers is often a balanced sub. Of course, this depends on the sensitivity of efficiency rating of the driver.

Second, because our ears are less sensitive to those regions, distortion can be higher before we even hear it.

Third, most music isn’t recorded and full signal; most sound recording utilized a fair amount of headroom to produce dynamic bursts and crescendos. Honest RMS power vs Peak power ratings means the peak is literally double the RMS power because any descent and honest driver motor design allows for those peaks to feed double the power to the coil without harm to the speaker.

Last, most people don’t listen to music at full blast even though we tune the amps to handle full signs from the head unit (or close to it if we’ve measured the head unit pre outs for distortion. So we can cheat and turn the amps up a little without breaking any rules or detrimentally affecting sound quality.

So you might just need some more gain…

 

Excellent points. We did dial in closer to 6db overlap on the sub channel for exactly the reasons you mentioned. Without that, the subs didn’t do much at all.

I’m not overly disappointed with the maximum achievable level of my current subs. They get plenty loud for my use! It’s the lack of low frequency response that I’m displeased with. To be honest, it’s terrible.

Could I get more out of these two Comp RT 8s? Almost certainly, with a different enclosure. And I just may do that in our Jetta trunk to compliment the OEM gear. Maybe a pair of ported enclosures in the rear corners of the trunk that are tuned in the low to mid 30s.

 

Good to know. I just thought I'd walk through it one more time in my head. Looks like you should have the amp setup correctly, though one more thing I did think of if your amp has a subsonic filter; they aren't a brick wall filter but usually a 12 db/octave filter. That means that if it's set to 20 hz, you still 6 db down at 30 hz. I usually set them between 12 and 15 hz 15 hz puts you 5db down at 22.5 hz and 0 db down at 30 hz.

I'm still surprised that the RT8's are giving decent low end performance. I installed some older model Kicker 8's in a friends Super Duty a while back and they flat out surprised everybody. He didn't believe me that I installed 8's and not a set of 10's or 12's. I'm tempted to order one and measure it just to see what's going on. I really have become a fan of 8's in cars when space is limited.

What size sealed box did you end up with for the Kickers? I think they recommend as small as .2 cu ft per driver, but I've not found an 8 that gives any sort of satisfactory low end with less than .3-.5 cu ft, and often requiring a touch of boost down low.

Ok, one more one more thing I though of. Running a 5 channel amp (or 4 channel amp with two channels bridged), you can sometimes run out of juice on the sub channel when the other channels demand power. The lower the bass, the more juice is required from the amp (well, kind of, as it really depends on the shifting impedance load of the subwoofer, but generally the impedance drops until you get to the drivers Fs, then swings up wildly). I've had some four channel digital amps behave strangely when running a sub off the same amp. When I switched to a separate mono amps supplying the same power, the sub had more go down low.

 

Subsonic filter on my Kicker CXA-660.5 is not adjustable and is at 25hz, if I remember correctly. I also thought it was 12db/ octave, but would need to confirm.

My current box measures out to 0.62 gross ft3 total for the two subs. It is within spec for volume, but I bet they’d do a lot better with more space. I also bet it would be better if the idiot that built the box spent more than 13 seconds sealing it…


Edit: Just checked and the subsonic filter is 25hz with a 24db/ octave slope. Should be like a wall…

 

I would be interested how one of the 8,s would sound in 1cf tuned at 38hz

per kicker website .8 to 1.2 cf is what is recommended