Building a really great stereo - LotusTalk - The Lotus Cars Community
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post #1 of 9 (permalink) Old 07-08-2019, 07:23 AM Thread Starter
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Building a really great stereo

Yes, an Elise is a loud car. Yes, an Elise is a car where every pound counts. Yes, an Elise is about driving first and foremost. With that out of the way, let's talk audio.
This 2005 is going to be my daily commuter 365 days a year and I like music. I'm an audio nut and love a challenging installation (last car was a '68 Corvette convertible where it had to look stock and I wanted to cut no metal or fiberglass). For the Elise, the goals will be a good audio environment (i.e. everything doesn't buzz and rattle at full volume), decent output (I can hear and understand it on the highway with the top off), the best sound stage and "proper" response I can get (I have a house curve I try to target once time alignment and staging are set), and as little interference with the "Lotus" experience as I can get (meaning, mainly, the least weight gain possible).

I've been working for about 3 weeks on this and have been lax in taking pictures and (obviously) posting. But I thought I'd put the information out there so any other interested people could find it. Just for fun, I used my calibrated mic and REW ("room eq wizard" is a program that takes all kinds of audio measurements) to measure response of the stock system before I tore into it. The attached curve is the "best" response I could get with the stock audio. It's bass all the way up and treble halfway. As you can see, there's basically nothing below 100 Hz. This is no surprise given the size of the speakers. There are a couple of big holes in the vocal region and virtually nothing above 12k. Of course, there's no sound stage either. None of this is surprising to anybody who has listened to the stock system. I just thought it would be fun to post.

The first component in any installation is sound deadening. There are a couple excellent threads on this topic, so I won't rehash. Very briefly, sound deadening has a four main components.

1. Eliminating squeaks/rattles/buzzing. Many people skip this because it is a true pain in backside. But we can't skip it in these cars.
2. Eliminating panel resonance. This is the dynamat world. The goal is to take big panels that resonate and move their resonant frequency down so that the noise doesn't interfere with the "good" noises.
3. Decoupling surfaces. We want to isolate each surface from the ones in contact with it with some cushion so sound (aka vibration) doesn't translate from one to the other.
4. Sound blocking. This means using some layer that actually blocks sound. Note that this is not "dynamat" type materials. It's usually some kind of "mass loaded vinyl." It only works when decoupled from other surfaces and uses mass to block sound waves. The frequencies blocked are dependent on thickness of the material.

In this case, I'm going to go big on steps 1-3 and pretty light on step 4. The reason being that to do step 4 properly takes full encapsulation of the interior and adds a lot of weight. I decided I wanted to add less than 10 pounds of deadening and there's no way that would happen with enough mass-loaded vinyl to make the car "quiet." An Elise will never be a Lexus (or, let's be honest, a 15-year-old Civic) in quietness.

For step 1, I disassembled the interior. Dash, doors (meaning window mechanisms and latch), and all panels. I used Hushmat Quiet Tape to wrap wires, and felt-backed tape between all surfaces (

) and SecondSkin butyl rope in a few places. The doors are major sources of rattles and took the most time by far. The biggest rattle comes from the latch rod which runs in a channel from the interior handle to the latch. I had to pull that apart and line the inside with felt. Then it's just a matter of finding every place where anything touches anything else and figuring out how to (a) keep the things from touching or (b) cushion them if you can't keep them apart. As a side effect, the doors shut with thunk instead of rattle now. Also, I had the undertray and rear diffuser off, so I remounted them with rubber washers (after using dynamat on them for resonance as per some of the other threads' suggestion). Now, the car doesn't rattle at all when driving. When I got the stage of putting the panels back in, they got the same treatment.

For step 2, I used Dynamat did the same thing as detailed in other threads. The whole back wall and floor got about 40% coverage. I skipped the doors since the fiberglass won't really resonate and I'm watching my weight. Since I removed the big, heavy insulation that goes along the back wall, I was still down from stock weight at this point. Only by a pound, but I'll take it! As I said, the goal isn't a silent car. It's an acceptable environment for a stereo.

For step 3, I ended up using 3 different materials. For the back wall, I used a closed-cell foam with a heavy foil backing. There's enough room to get away with the thickness (thicker is better for all this stuff) and any heat-rejection will be a welcome thing in the summer. Under the seats, there's very little room for anything, so I used this Noico product:

. For the other places (back in the "wings" above the ducts behind the seats and in the front floorboard), I used SecondSkin Overkill.

While I was at it, I made some custom panels for the sills and used the foil-backed closed-cell foam insulation on them. The panels are made from corrugated plastic signboard and covered with black leather to match the seats. The goal of this is to insulate from the hot oil lines, not noise.

Finally, I used the mass-loaded vinyl. I ended up covering the rear wall and floor with it to cut down on road noise and the less-pleasant engine noise (the mlv will block the higher frequencies associated with engine clatter and harshness).

The end result was a weight gain of 6 pounds. I couldn't resist seeing if I had made an improvement, so I put the driver's seat back in and took it for a drive. Even without the stereo, I'd have done all this. It makes the car sound and feel so much more solid. No rattles, vibrations, and squeaks. It's still pretty loud (I have Top Speed Pro 1 exhaust, which is by far the biggest source of noise), but the sounds are good sounds.

Next up - components and installation!
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post #2 of 9 (permalink) Old 07-08-2019, 07:54 AM Thread Starter
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After lots of research and modelling (using Winisd if you're not familiar with audio modelling), here's what I settled on:

Head unit: Pioneer DEH-80PRS. This is one of the best head units ever made for sound quality. It has a complete suite of signal processing capabilities built in and I was originally planning to use it for processing. But I can't resist a separate DSP, so I ended up with a MiniDSP 2x4. Meaning I'm not fully using the head unit's goodness, but it still has all the other high-quality components.

Amplification: I usually end up with 3 amps, but space/weight constraints dictate that I stick with 1 in this car. I settled on an NVX VAD11005. It has 4 80 watt channels and 1 600 watt for the sub. This meant I can't run full active crossovers if I ended up with components for the dash, but that's ok. I'd really like something closer to 180 watts for the 6.5" in the rear wall, but we'll see how this sounds first.

Processor: MiniDSP 2x4. This will handle the midbass (in the rear wall) and dash components. For the sub, I'm going to use the head unit to set crossover and slope.

Dash: I found a good deal on a set of Morel Virtus 402 components. They are a 4" mid with a separate tweeter and very nice passive crossover. As a bonus, the grilles look very stock. They will handle the 80 watts just fine and are really incredible speakers.

Rear wall: Hybrid Audio "Legatia" L6SE. These are some of the best 6.5" drivers you can buy. They actually don't model great in this installation, so they may not make it into the final iteration. I had a new set on a shelf and love them, so I'll try them, though. With the volume behind the panel, something like Peerless SLS would be ideal, but we'll just have to see.

Sub: As everybody knows, this is the real problem in this car. I'm a big proponent of ported boxes, but there's just no way in these things without major fabrication and surgery. So sealed it is. When it comes to subwoofers, cubic inches matter (speaking, of course, in broad generalities). So I settled on this carbon fiber box off ebay. It has .6 cu. ft. and is built for a 10" sub. This is much better than any of the footwell options (which have about a third of that volume). For the sub, the ideal unit is a Dayton HO. The Dayton is a very well-respected SQ sub and needs exactly .55 cu. ft. for the best response. It also happens to handle 600W just right. It's only downside is that it's 1/4" too deep to fit in the box, so I ended up making a 3/4" MDF baffle for it.

For the installation, I ran 3 channels of RCA from the head unit (2 to the dsp, 1 to the amp for the sub), 7 channels of speaker wire, the amp turn-on, and the USB for the MindDSP through the grommet in the firewall and through a hole I drilled in front of the battery. All wires go in loom. All connections are soldered. I mounted everything on a rack between the tail lights. For the rack, it has a bar on the top that ties into the top mounting stud on the inner brake lights and a piece of aluminum angle on the bottom with a mount through the floor (you can reach above the license plate between the lights to put the nut on). I ended up not having room for the fuse block, so it's on a separate little "wing" mounted at 45 degrees to the main rack.

For the dash speakers, I had to cut a hole for the tweeter, but once it was put in, I was really happy with it. Looks pretty much like it belongs there! The 6.5" drivers in the rear panel require a little trimming to fit, but mounted fine. Last night, I got to the final assembly and powered everything up. Since I don't have any crossovers set yet (besides the passives to the tweets), I just turned it up loud enough to make sure everything works. Next will be the fun part. Tuning!
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post #3 of 9 (permalink) Old 07-08-2019, 11:02 AM
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This is looking great!!!

2005 Elise- Katana II Supercharged and other fun bits
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post #4 of 9 (permalink) Old 07-09-2019, 10:56 AM Thread Starter
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I got the initial tuning done last night. The first thing to note is that, despite all my attempts at deadening the interior, firing up the sub for the first time sounded like the kazoo band from hell. Lots of rattles, still, from the back panel. I pulled it back apart and mostly covered any area that touched anything with Quiet Tape. Then I used the butyl rubber rope to couple loose parts to solid parts (mainly the plastic piece that runs along the top of the firewall). You just shove some of this really sticky rubber between the surfaces to keep the loose one from vibrating. I also used the butyl around the biggest offender - the rear light. That thing sounded like an angry horsefly at about 60Hz.

Then I used the Noico stuff on the back panel itself where the box sits. This, I reasoned, would keep the plastic and carbon fiber from buzzing against each other.

I put the box back it and it was... better. But I could still hear it. I don't want to hear anything but clear, clean bass. Buzzes drive me crazy. I noticed when I tilted the box forward, the buzzing went away. So I put a little more padding at the top. But leaning the box back still made a racket. Finally, while playing a test tone, I pulled the box out and noticed the whole back was vibrating a TON. There's just not enough mass in that big flat surface in the back of the sub box to damp it. So I pulled the sub out. Then I epoxied a stiffening brace across the back of the box and used 3 layers of dynamat (all on the inside). Once the epoxy dried, I put it back in. Viola! Nothing but the actual sound I want.

As far as the rest of the tuning, I won't bore you with the details. I got time alignment dialed in, individual driver levels, and crossovers. I'm currently crossing the midbass/dash at 250Hz, which screws up the soundstage (ears can localize sound below my 250Hz crossover). I'll move that down as I play with it. Supposedly, these Morel 4" can go as low as 160Hz safely. I'm just very conservative with my equipment... Right now, I'm overlapping the sub/midbass by 10Hz with a 24db LR. But that will probably get adjusted as well. After a quick pass through EQ on the midbass, my current response is below. A little cleanup to do (need to bring the tweets up, knock down some high spots, and do the mids), but it already sounds pretty good. My only fear is that I'm really not going to have the midbass I want. The 6.5" may be the weak point. If only I had a little more power to feed them...
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post #5 of 9 (permalink) Old 08-18-2019, 03:04 PM
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I love what you've done. You're the audiophile I wish I had the space and motivation to become. Not having a garage makes clean interior work difficult. Working on the 60 year old driveway just doesn't cut it for fine work. I read this post often, have picked up a few tips. By coincidence we picked up the same front speakers.

I put a 600 Hz cut-off on the fronts hoping to lower the dash buzz. What do you think this is doing to my overall audio?

2006 Yellow Elise, BOE Torque 250, Katana II
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post #6 of 9 (permalink) Old 08-19-2019, 05:50 PM Thread Starter
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Yikes. Working in a driveway SUCKS! I lived in an apartment for 2 years during college and had my Miata torn apart many nights in the parking lot. Never again... I admire trying to do anything outdoors.
I'm curious about the rest of your system. My current project is an extreme "budget" stereo in my pickup (hard limit of $300 for everything), so I'm looking for ideas and options (sub stage is 4 Peerless SLS in a ported box with 300W, but still need a front stage and head unit).
But if you're buying Morel stuff... maybe not. Personally, I don't see a reason to cross the dash as high as you're planning, unless you're feeding them insane power (north of 150W per side). I don't know that there will be that much buzzing in the dash. You'll have to pull the dash top anyway, right? Might as well take care re-assembling, then you can drop that high-pass to whatever the drivers will handle. I just did a little extra work and I've had zero problems with dash noise.
Technically, for staging purposes, you really want to keep as much sound in front of you as possible. But (that being said) one thing I've learned over the years is that audio is completely listener dependent. If it doesn't bother you to have sound that clearly comes from behind you, then there's no reason to spend big money on perfecting a "proper" front. Or if you're of a "certain age" where you can't hear frequencies above 12k (ahem...), who needs fancy tweeters?? For all the time and money I've spent getting things "right" from somebody else's perspective, I've decided that the most important thing is that I enjoy in with my music. And I'm finally getting there with this car.

I should have been keeping this thread updated, but the big challenge has been the stupid rear wall. I've pulled it completely apart (seats out, rear wall out) 3 times since my last post to fix buzzing and think that this time I really have it fixed. But, wow, there was a lot of vibration to fix when you have enough midbass and sub bass to feel it in your chest. I also pulled the single amp and went with a 2 amp setup for a couple weeks so I could feed the 6.5's 180W. Meh. For me, it was more annoying than beneficial to have so much of that frequency coming from there. I'm happier with the original setup. Also, I changed to a 1/2" MDF baffle on the sub since I had problems with it hitting the seats at 3/4". Wow, it's tight in there...
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post #7 of 9 (permalink) Old 08-20-2019, 02:15 AM
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seems overkill to me [car and audiophile aren't compatible words!] but good to see anyway.

i dynamatted and dynalined my doors, floor and bulkhead [have got full carpets]. replaced the head unit with a mechless pioneer and a class D amp which both fit into the space of the alpine. speakers are 5.25" pioneer components on the dash [very neat tweeter, looks oem] and the same in the bulkhead just without the crossovers and set on the head unit as subwoofers.

100x improvement over stock for under a days work and sub $300 for the audio
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post #8 of 9 (permalink) Old 08-20-2019, 03:54 AM Thread Starter
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That’s the fun thing about car audio as opposed to home audio, in my thinking everybody has to work around the inherent weaknesses of every install. And everybody has a different set of priorities, so every one is unique. In the “proper” audio world, it’s an equipment and tuning game. In car audio, you have to make so many compromises and decisions that I think there’s more room for creativity. That’s why I post car audio builds, but never home audio. If you’re happy with 4 5.25 speakers, rock those things. For some of us, if it’s worth killing, it’s worth overkilling.
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post #9 of 9 (permalink) Old 08-20-2019, 08:39 AM
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very nice! A good stereo system should not be attempted without a good DSP.

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