saxon

Alright here comes big post about my sound system design. I’ve spent months researching car audio and coming up with a design for the system, I’m gonna do a brain dump of the whole process, but the end result is this: Tweeters: SB accoustics SB21SDCN-C000-4 Midrange: Morel MM2 Midbass: Studio Integrity TM8 Sub: none Amp/DSP: Helix V Eight MK2 Head Unit: Sony AX5500 I love music and all things audio and set out to design the best sound system I possibly could for the Datsun. To make a sound system in a car sound good, rather than just loud, there’s a bunch of issues that need to be overcome that aren’t present when you listen to 2 speakers in a room: Time alignment (listener is not equal distance from both speakers) Many sound reflections causing EQ issues Directionality - music is designed to come from in front of you, but there is not much space in a car cabin in front of the driver for speakers The first 2 of these issues can mostly be solved with something called a Digital Signal Processor (DSP). A DSP a little computer that processes the music signal before it’s sent for amplification, and it does this separately for each individual speaker. This allows each channel to be EQ’d separately, and certain channels to be delayed in time so that the sound arrives at the listener from all speakers at the same time. The other thing that the DSPs made by Helix allow you do is a “2 seat tune” which is a way to make the music sound good for both driver and passenger, rather than tuning the whole system around the driver. The general concept of this is for the center information in the music to play out of a dedicated center speaker, rather than being a combination of left and right playing at the same time (which doesn’t work well cause time alignment can’t be done for passenger and driver at the same time). 2 seat tune was a really important thing for me cause since my partner is allowing me to spend all this money on a sound system, I want it to sound as good as possible for her too, not just myself. The third issue to be overcome is that music is designed to come from in front of you and often each instrument has a distinct placing on this “sound stage” in front of you, from left to right, and close and far. This is hard to achieve in a car cause there is limited space for speakers in front of you. Door and kick panel speakers are an improvement over speakers in the back, but are still a big compromise to sound quality. There is one factor working in our favour though and that is that humans can’t perceive direction in sound below around 200hz. So we can design a split system where the above 200hz information plays out of a speaker pod in the dash or attached to the a pillar, and the low frequencies play from anywhere else. And this is indeed what high end audio builds do. So with that in mind, I had 3 options: Cut the dash to put speakers in (ugly) Build a dash or a pillar pod for the speakers (not really possible with the sharp slope of the windscreen and also ugly) Put the speakers in a sub optimal position like doors At this point you’d probably wonder, why bother? And especially why put a good sound system in a 3.1L stroker Z which already sounds insane and is pushing legal Db limits? Reason is… for science. I wanna push the envelope and see what’s possible. So I was coming to terms with having to cut big ugly holes in the dash for my midranges. Then I came across a very special speaker, the Morel MM2 midrange. Although these don’t quite go down as low as the target 200hz, they’re absolute tiny for a midrange, so small that they fit into the dash cowl area up front near the windscreen. So the idea became - mount the speakers into the dash cowl. After some testing, keeping the dash cowl in one piece wasn’t possible, it’s hard enough getting that thing in and out already, with speakers mounted in it would be impossible to install without removing the windscreen. So I decided to cut up the dash cowl and make mdf speaker panels for the sides so everything fits. Lachlan’s shop helped do the cuts to the cowl for me and got the circles for the speakers perfect. While I was at it, I also made a speaker pod for the center. Photos attached for how these ended up looking. I think these turned out okay given I have zero prior woodworking experience. I’m mostly just happy everything fits and works cause it was playing with fractions of a millimeter trying to get it all to work. But I’m not completely happy with them and I’ll have another go again some time and make them nicer. For the tweeters, I went with sb accoustics SB21SDCN-C000-4. Reason being crazy good off axis peformance, aesthetics, rave reviews, and low price. For the low end, I’m going with a stereo integrity tm8 8 inch midbass, which will run from ~60hz to 500hz. These will be mounted into the riser behind the seats and will be mounted in an “infinite baffle” setup. I decided to go with 8 inches rather than traditional 6 inches in a 3 way setup cause 8 inch covers the frequency range I need <500 Hz way better, and the car audio forums are going crazy for these speakers. I’m going to try this setup first without a dedicated sub woofer cause I’m thinking I’ll be getting more than enough low end from the 8 inchs for the type of music I listen to. Other goodies being added in Sony touch screen head unit with apple car play Reverse camera Helix controller for volume, tone, and preset selection (1 vs 2 seat tune) Next step now is to get the professionals to install it all. I’ve reached the end of the road in terms of what I’m comfortable doing myself and I don’t mess with electrical stuff.

Been busy working on the car recently, some updates: new steering wheel new CF door cards new carpets wheels repaired and new tyres new tail lights Sound system and LSD are coming up next.

I’ve been working on sound treatment on the Z and I’ve been planning from the start to hit the tail light area with sound absorbing foam. Reason is that due to the shape of the car, sound frequencies will accumulate there and project straight back out at the driver like a trumpet horn. Especially low level frequencies that contribute to droning. So I have cut out a piece of acoustic foam and stitched it onto the tail light cover panel with acoustically transparent fabric. The idea is that troublesome droning frequencies will be funneled down there by the shape of the cabin, pass through the fabric, and then get absorbed rather than project back out. I took it for a test run today and I swear it make a huge difference. Prior to adding the foam, the engine getting very woofy at around 4.5k rpm. Like it would go RrrraaaaaaaaaaWWWWHWHWHaaa. I know it’s not to do with the exhaust or engine cause the woofy sound isn’t there from the outside. Now with the foam it goes Rrraaaaaaaaaaaaaaa all the way up. Pics here of what I did, execution can be cleaner, I need to iron it and tighten it up but there it is.

Yeah my quarters look something like this but I probably won’t put foam in my doors though, due to potential for it getting wet and growing mould. I’ll load them up with butyl rubber only.

Possibly! Much of the body is in primer right now but might bring it anyway. And yeah I’ll be treating the doors too, giving myself a whole weekend to do doors cause I got no clue what I’m doing. There’s a bunch of other stuff I need to do in there like rubber. I got a bunch of other plans to kill resonance inside the car, like using sound foam in the roof, and acoustic fabric rather than normal roof liner, so sound waves can pass into the foam and get absorbed rather than bounce off it. And make a bass trap of some sort at the tail light area, my plastic interior tail light cover is all cracked up so I have no issues butchering it into something that absorbs sound.

It’s been a long time between posts here, it’s been interesting looking back and seeing the journey I’ve been on with this car, so an update is due so I can continue to look back on this story in the future. There has been much progress over the years. Most notably, the Z now has a Les Collins built 3.1L stroker with triple webbers. And an engine bay make over. Speedhut gauges are in too and a bunch of rust repairs and body touch ups from Lurch’s shop. I’m over the moon to have the car at this point and it puts a huge smile on my face to drive. The sound is glorious. And it’s great to have the power to match the aggressive styling choices I’ve made. The car needs a repaint now but other than that, I consider the original vision I had for this car is more or less complete. Thing is, I’m no longer a young man and the vision has changed. I can’t really deal with no ac so that’ll need to be addressed. I’ve found inspiration from what MZR have done and where the restomod scene has gone recently. So an interior make over is now on the cards. And I’ve been putting a lot of thought into how to get a nice sounding sound system into the car. Browsing the forums, some people say getting good sound quality can’t be done, so just put speakers in the back or the kicks somewhere. I take that as a challenge and I have some crazy ideas cooking up. Luckily the interior stuff is more within my limited capabilities so I’ll be more involved with that. I’m half way through stripping out all the interior and doing 3 stage sound treatment - butyl rubber + closed cell foam + mass loaded vinyl. With only the back done the difference is big, engine still roars but I can have a conversation while cruising without having to yell. Lots of work to do, I have a list that feels like it’ll take another year to get through. I’ve hit many points where I’ve thought that financially I can’t keep up and the car will need to be sold, but feels like those tough times are done and I’ve got this car for life now. That’s it for now I think, I’ll try post more updates as I go.

Another pic

Cheers Bruce, will bring it to a meet once this craziness has passed

Coilovers in, drives much nicer now, doesn’t feel like it’s trying to kill me anymore. old springs and top ends available for free pickup in thomastown if anyone is interested just let me know.

Yeah I agree that something is clearly missing, but I just dont think those panels solve the problem, still looks like something is missing and then patched over in a way that doesn’t quite blend in. Even if 100% colour matched it’s still not a look I like. I think it’s due to the indicator, it should bulge out entirely or not at all, but half way between is weird. I saw this yesterday, I like this look the best, looks clean and functional.

Yo yeah I’ve been thinking of what to about the bumper delete situation. I’m not a fan of those either though as it moves the colour change up which looks weird to me. i think the solution is to stick matte black plastic circles over the holes, it would look cleaner because all the holes would then look same size, and would give the illusion that they are all doing work to hold the front spoiler on.

Cheers ☺️ I took her out last night, here’s how she’s looking.

It’s been a long hiatus but my zed is up and running again. I took it into Nissco /dat1600 workshop and they did a great job fixing up a decent list of things for me and getting it going again. I couldn’t find much in the way of forum reviews on them but decided to give them a go and couldn’t be more happy with that decision, they’re very professional, have great communication, and know these cars well. Plans are going ahead to build a 3.1L or 3.0L stroker. And I have a little list of cosmetic stuff to work on in the mean time. Right now I’m finding it a real pain to find a steering column cover, if anyone has a spare let me know

And pics of the triple weber kit and P90 head being sold separately.

These goodies included in the 25k asking price. Exhaust includes pipes all the way through. And other bits and pieces for an engine rebuild I was going to do.