Hi All,
Big update!
Slight change of plans with regards to the sub, and I decided I didn't want to lose the boot space, so cancelled the order for the Match sub and went for a custom-fit enclosure & Focal RSB-250 sub. Focal don't make a grille so the bars were just a cheap job from Amazon.
Didn't get any pics of the enclosure, but the quality is amazing, and it arrived within a few days from Poland for a sniff over £90.00...don't know how they do it, but here's the link for anybody interested:
https://www.ebay.co.uk/i/173036155328?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=173036155328&targetid=908661247816&device=c&mktype=pla&googleloc=1006636&poi=&campaignid=10199631325&mkgroupid=103626356284&rlsatarget=pla-908661247816&abcId=1145987&merchantid=101742229&gclid=CjwKCAjw57b3BRBlEiwA1Imyts1hpIWvKJCveT81B7VLG6OKFD4-50S3p1VHdB9Q1K4WEHNoE5HvPRoCCQQQAvD_BwE
Dual voicecoil wiring to bring the impedance down to 2 ohms:
Some Dynamat on the rear panel - a bit of wadding also went in as the driver's meant for a 20 litre enclosure, but the enclosure's on 15 litre. You can also see where I removed the terminal panel and used some silicone sealant to completely seal it; the front panel is made from two sheets of MDF, so also needed a tiny bead of sealant along the edges, and speaker gasket foam tape around the lip:
Driver in, and grille on, and the job's done:
I was lucky to get the use of a friend's carport over the last week, which was great as it meant I could work on it in the rain, and not have to worry about rushing to put it back together in a hurry, so now was the time to work on sound-deadening the rear quarter panels and wheel arches.
Pay attention to the two pieces of grey foam behind and next to the seat belt reel, as these are obviously there to block noise from the void entering the cabin. Neither of these were seated correctly on either side so weren't really doing anything; I wonder if this could be the problem for those suffering with a boomy boot? There's also another piece inside the area of the wheel arch and outer panel quarter skin, again these weren't seated correctly. I'll add this info to the thread on the main Octavia 3 section.
Getting there:
And the final touch; Hobbycraft's finest "soft toy filling" to fill the voids:
I didn't get any pictures, but also put Dynamat on the inside front of the wheel arches, and filled the space with soft toy filling; this is the area covered by the big plastic trim in between the doors and the rear seat backs.
Also thanks to @JohnnyType2 for the great idea of running the sub cable down the centre console and cutting a hole in the carpet to run it down the transmission tunnel and pop out under the rear seat bench - very easy, and much nicer than trying to remove all the trim around the bottom of the doors I'm sure.
Not content with just doing the inside, my buddy had a few sheets of Silent Coat left over from another project, and as there was the space and a set of axle stands kicking about, the rear wheels and arch liners came off, and the outer arches also got some treatment:
The difference this has made is crazy...there's virtual silence from the rear of the car at 30-40mph, and sooooo much quieter and serene at motorway speeds. The only problem is that it now sounds like the engine & road noise from the from the front has increased 🤣 Considering how easy it was to deaden the rear arches, I'll do the front sometime soon.
And all back together; my buddy had some sorbothane (isolating material) washers, which work by being under compression, so there are two of these at the bottom of the sub between it and the mounting points, and then at the top of the sub where it clips into the car trim - we cut the washers into section, straightened them and pushed them into the space - the sub is extremely rigid in there, but also decoupled so doesn't rattle at all!
The pic isn't very forgiving with the difference between the original carpet and that on the sub, but it doesn't look that different in the flesh...and it's in the boot, so I don't care as I'm not going to be looking at it 😉
The only thing I have to do now is sort a couple of rattles in the front doors; both doors are doing it in the same place at the top, near the back where the door card is split and stuck together where the LED lights trip is. I think some hot glue and foam padding should cure that, as when I push that area with my hand the rattles stop.
Having the sub in has allowed me to roll the low frequencies off form the front speakers, which has opened them up considerably. I've currently got the crossover point set at 100hz, after playing about with it at 80 & 120hz.
I've also experimented with muting the rear speakers and just going with the fronts + sub, which sounds so much better. I think due to the position of the rear speakers (the tweeter's much closer to your head than the front speakers and points backwards), then it smears the image and sounds all phasey - I've checked and double-checked the wiring, and flipped phase live in the amp's software and it just doesn't sound anywhere near as good with the rear speakers enabled.
This isn't a problem, as I hardly ever have rear passengers, and it also gives me the ability to remove the passive crossovers from the front speakers, and configure the amp to run them actively with all four channels. I'm probably going to remove the rear speakers, pop the originals back in just to fill the holes, then I have a spare set of Focals just in case...this system goes loud now 😈
I think in the short term, I'll do some measurements with the mic and real time analyser and tweak the amp's EQ settings and see how it goes from there!
If you've made it this far, then thanks for reading!
Nick