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Discussion starter · #101 ·
Here is a markup of 3 subwoofers in the smaller box (amps mounted on box)...

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This one is already an accurate example of the slightly larger (net volume) enclosure:

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So what I'm seeing is that because of the high QTS and extremely undersized enclosures (by conventional thinking at least) is that the vented enclosures are coming out peaky, and lack a bit of low-end extension. This effect is not insignificant - between 2 & 5 dB in most cases. That said - my ears preferred the vented a decade ago, and if I'm going to end up with a sealed enclosure anyway, I may as well run with the high-excursion Skar woofers I already have.

I'll see if it's possible to arrange these any more efficiently, shorten up the port a bit, and figure out more efficient routing. But really so far, this enclosure - while unique - looks like a lot more work than the other one. It may come down to a question of aesthetics (oh, and the fact that my amp only bridges to 4 ohms, so there would be a bit of amp shuffling to get to something that can handle a nominal 1.3 ohm speaker assembly.
 
Discussion starter · #102 ·
Okay, bear with me on the math for a minute longer - or scroll past, I'll understand. I've had enough math for a while myself as well. I ran just a few corrections and I've posted the inputs here. This post supersedes my data from 100 and 101.

2 sub scenario, amps to side, 1.08 CF vented vs. 1.37 CF sealed. 1-2 dB difference in low end extension. This relies on moving amps to the side and deleting one woofer. (Sealed: Q=1.28)

Blue = sealed, red = vented, black = optimal in the middle of an open field, no room gain.

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3 sub scenario, 0.89 CF vented vs. 1.28 sealed. Q=1.45 (amps to side)
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3-sub scenario, original - amps on box (0.7 vented vs. 0.99 sealed)
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So, what does it all mean to me? In the context of this necessarily undersized enclosure, the sealed may have a 1-2 dB advantage in low range extension. Unless you are competing for SPL (news flash, I am not), I would pick the one that is more satisfying to your ears. I checked out the group delay curve - but I'm honestly not worried about that. No more than about 15 ms within the audible range on any of these vented enclosures, I've certainly dealt with worse, and only occasionally can I even hear it (and that's usually when it's on the recording and used intentionally - you'll perceive it as the bass lagging behind the rest of the music. To large extent, it can be overcome with time alignment anyway, so long as you don't mind being ahead of phase a bit in the 30-80 Hz. range... This is nitpicky stuff though.

On a whim, I plugged 1.06 CF (30 L) with a slightly increased port cross section, but shortened up quite a bit. 27" effective port length with 20 Sq In port cross section, yielding 41 Hz tuning. Now if I can figure out how to build such a box within my space constraints, we may have a winner. That peak means I'll have usable bass above the frequencies where cabin gain is helping. Check it out, I'll have to try this out against the Skar subs and see which route I need to go, and whether they can be pressed into similarly effective (and aesthetic!) service -

Maxed out on files, to be continued ---
 

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Discussion starter · #103 · (Edited)
As I was saying:

On a whim, I plugged 1.06 CF (30 L) with a slightly increased port cross section, but shortened up quite a bit. 27" effective port length with 20 Sq In port cross section, yielding 41 Hz tuning. Now if I can figure out how to build such a box within my space constraints, we may have a winner. That peak means I'll have usable bass above the frequencies where cabin gain is helping. Check it out, I'll have to try this out against the Skar subs and see which route I need to go, and whether they can be pressed into similarly effective (and aesthetic!) service -

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Winner winner chicken dinner. Now I apologize if I've bored you to death today. It was a rainy day, and I learned (or relearned) something about these drivers. As a QC & engineering type dude by training, I'd rather get through all the brainstorming sketches and run several scenarios in the virtual space before I commit to prototypes. And it was a rainy day, can you blame me?

That said, I need to get door cards back on my car soon, which means door speakers, so the next few posts should have some pictures and not just graphs.
 
Discussion starter · #104 ·
I've established a semi-final design. I reverted back to the 10s so that I don't have to replace the amplifier, and because they lended themselves to a more space-efficient ported arrangement. I'll need to test with a prototype before actually building, because as you probably know, ported enclosures can behave differently than anticipated based on which parts of the enclosure the speaker "sees" as box volume vs. port volume.

This is 100% optimized for space efficiency - form follows function. The amplifiers will be arranged however they fit best for a clean wiring job. I may or may not dress it up with amplifier covers, false floor, etc - this is just a proof of concept for the loudspeaker itself.

The red areas may require minor fiberglass or at least chisel work to fit the drivers.

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A little accidental pareidolia here 😐

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Total interior volume, excluding driver displacement adjustment: 1903 CI or 1.1. Assumed to be 1.0 with driver displacement.

Total port length, center of port: 24.25"

Assumed effective port length: 30"

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I like everything about these response and impedance curves. I will do a test listen against a sealed enclosure, but if the charts don't lie, and we pessimistically assume 12dB/octave cabin gain doesn't kick in until 60Hz, we are:

+1Db at 120Hz
+0Db at 60Hz
+6Db at 30Hz
+5Db at 15Hz (!) - though it may start to unload around 16Hz based on the impedance chart. An 12db/octave HPF at 25 Hz puts me at about +2Db at 20Hz....

So, again, if the chart doesn't lie, I'll have an in-room response of +/- 2dB from 20Hz to 120Hz.

Oh, and a little bonus, group delay never goes above 14 ms.

I think I have to build this one. No point drawing anything more unless this one fails in testing.

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Discussion starter · #105 ·
I did promise hands on, but first I needed to diverge briefly from mobile audio - but still audio audio.

eBay seller: speaker tested and works great, cosmetic issues only.

The speaker:



Okay but it's not worth the time for return shipping. Instead:





About 20 minutes work cleaning up the basket and cone and centering by hand. It's all cured up now, just tested and no rubbing.

Back on mobile audio soon.


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Discussion starter · #106 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

Textile samples arrived.






All the greens are too light or too bright, need something darker and more subdued.

Of these, K0943 "Aegean" and K0330 "Discontinued"... are the least offensive. I could go for Aegean dyed about 30% toward a medium charcoal gray, but that may be a bit too much to ask.

Unfortunately, my preferred accent color is no longer available, so I'll need one more round of samples. Will probably end up doing most of the box in Aegean if no closer option comes up on my radar. Could use that as the accent color elsewhere to tie it all together. Sometimes, a simple aesthetic is hard to pull off, but that's my objective - just like the car: function first. The form should disappear as nearly as possible, if I can manage it.


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Discussion starter · #107 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

Next round. I'll decide on my order from the previous batch and this one.

K0699 - Aqua plain velvet


K2834 Atlantic


E6320 Deep Teal Green Blue Vinyl


M9313 Blue and Green Plaid


E2860 Huron Blue Vinyl


K0495 Blue Plain Tweed


K0719 Evergreen Dark Blue + Dark Green Tweed


In a parking garage



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Discussion starter · #108 · (Edited)
Tweeter p0rn:

And a continuation of my eBay gambling adventure. Unsure if I will figure out how to make these work in a mobile application, or if I'll keep them for spares for my home stereo speakers - if I do use them here, it will be in custom kick panels.

I saw these on the dreaded auction site as "tested, working great"... all the photos included the temporary protective covers these speakers shipped with when new:



I reasoned that (1), the seller had not removed them, and that either (A), the original owner had never removed them and - rather stupidly - listened to speakers with the treble frequencies blocked, perhaps leading him to give up on the speakers entirely, or (B), the original owner had been meticulous about storing the speakers with covers whenever not in use. In either case, the notoriously hard-to-keep-clean sticky coating on the silk domes ought to be in decent condition.

Well, I'll let you be the judge:



Now, to immediately wrap these in plastic again and tuck them in the very back of the closet. I will start my build with some cheaper automotive silk domes, with perhaps slightly less ass than this:



Note, if I try to place them any closer to each other than this, they will literally scoot each other across the table with their magnetic fields.

So there is my reference, and if I can't achieve successful results from a conventional modern approach, my fallback as well.

Next, the humbler selections, but first, I have family dinner time to attend to.

(Edited to correct emphasis)

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Discussion starter · #109 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

Now, if you've made it this far with any degree of color blindness, I commend you. And I also apologize. A large part of my requirements for this build rely on believably OEM-looking material and colors. Here is my next round of textile matching. The following colors were missing from my order, I'm following up to see if they were sent separately:

M9313 Blue and Green Plaid

E2860 Huron vinyl

(Pictures of both shown in my earlier post).

Here are the colors I am judging today:




Of the vinyls, the smoky blue is a closer match. I'm not sure whether it's close enough to utilize here. The green is far too saturated, and I expect I will have the same issue with "Huron", which was missing from my order.



Color code for smoky blue for my records:



To be continued.


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Discussion starter · #110 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

Here are the accents. K2834 looks intention, is crisp and simple, yet very '90s. I'll roll with that one.



The greens are all too bright and too green. If I had to pick one, I'd K0484, but I think even that one would be out of place.



The blues give me a lot more options. From left to right, I like #1, #3, and #4. #2 (K0699)would be ideal with a solid blue interior.

#1 (KV888) has a bit of a grandma's couch [emoji934] vibe, and is a bit shiny, but it will look nice when detailed. That might work nicely for a subwoofer or amp cover.

#3 (K0943) pulls off the tweed look without being too obnoxious or out of place, and matches the carpet nicely.

#4 (K0719) looks lovely, but is too German to be used here. It belongs in an old e21 BMW 3 series, or maybe a VW Corrado.



Cars for reference (not mine) -






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Discussion starter · #111 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

My initial thoughts were as follows:



I thought I had it narrowed down to these, but I haven't yet been convinced that I'll need the vinyl. And then, as noted above, I decided the patterned tweed was too German for this car.





So here is where I'm landing for this order. I'll be ordering a couple yards each of -

K0943 tweed
K2834 pattern
KV888 velvet

The next trick will be deciding exactly where and how to use each, without being to obnoxiously ostentatious.


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Discussion starter · #112 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

(Edited to include color swatch of final selections)

I mixed it up on a whim, hope I'm right. Based on the naming convention, "Deep Sea" should match "Aegean" and "Atlantic".

$500 in textiles later...

(I'll have spares for later)

Pattern #: E1871 Deep Sea (Vinyl)
Price: $61.64
Quantity: 2.50 yards
Item Total: $154.10

-
-
Pattern #: K0943 Aegean (Chenille/Tweed)
Price: $74.09
Quantity: 2.50 yards
Item Total: $185.23

-
-
Pattern #: K2834 ATLANTIC (Accent)
Price: $62.37
Quantity: 2.50 yards
Item Total: $155.93

-
-
Subtotal of Items: $495.25


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Discussion starter · #113 ·
Slowly but surely, the audio begins.

View of interior of door panel:


View of interior of OEM door speaker grille:


View of interior of door handle / accent panel:


Note, on first glance, I assumed the accent panel was a separate piece: that it would be wrapped with fabric, then hog-ringed into place. Upon closer review, it is formed monolithically with the rest of the rigid cardboard / cellulose backer of the door panel, and the fabric is simply tucked into a groove.


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Discussion starter · #114 · (Edited)
Edit - to the extent you may be inclined to rely on this post as a recommendation for Kovi Fabrics, please see disclaimer here.

Testing two of the three textiles I ordered in the accent panel. TBD whether I replace the OEM velour, it is in good condition. That may be a project for down the road if the upholstery ever wears out.

I used a popsicle stick to tuck each fabric into the groove. The striped one (Atlantic) has a bit less natural structure to it, and try as I might, I always ended up with a wavy edge. The photo below is the best I managed.

So if I want to use the Atlantic pattern as an accent on the doors, I'll need to (A), laminate it to a structured backer cloth, or (B) run the stripes vertically or diagonally so they don't have such a long parallel edge. I think either (B) option would look odd in this contrast, and draw attention to the textile not being original.




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Discussion starter · #115 ·
Now, the most painful task I've had to undertake since I bought this car. The door panels went under the scalpel (literally - there was an X-Acto knife involved) to enable future modifications.

Reposting an earlier photo to illustrate how the door picket and speaker grille was fastened to the door card:



(There were little polypropylene tabs which were flattened with a heat welder in the factory to mechanically fasten the two pieces, "permanently". They underestimated my determination.)

An hour and a half later, having taken great caution to leave enough of the plastic tabs intact that I can heat weld the two parts back together, should it prove necessary. My objective, though, is to subtly space the door pocket away from door card by means of a fabricated spacer, potentially even a slender mid-bass speaker enclosure.

A plastic pry tool and patience were helpful here:


Pictured: the interior of the map pocket:


That's all for now folks. Progress has been slow - we are in the middle of a pretty oppressive heat wave and I haven't yet managed to get enough insulation in the garage to make it livable for more than a few hours at a time in the morning or late evening on these hot summer days.

Here's my progress on that front - I only have a reflective barrier in key places so far, but it is already making a difference. Between that, a small spot cooler, and a gable fan that kicks in above 85 degrees at the ridge of the roof, I can tolerate the heat until 2:30 PM most days instead of shutting down the shop at 11:00 AM.



Once I get all the rafters and gable ends shielded with reflective barrier, I'll put R15 mineral wool below that, leaving a little air space above and below the reflective barrier to vent condensation.


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Discussion starter · #116 ·
I mentioned trying some consumer-grade automotive tweeters. I'm a usually a sucker for silk domes.

Here's what I'll be trying, the price was right and they seemed well-reviewed. Chosen for their Neo motors, threaded mounting system, and relatively flat design:



My only ding cosmetically is that CT Sounds doesn't offer them in a generic black finish.

Today, I'll explore if and how I could mount the tweeter adjacent to a BMW midrange grille/housing and still have it look cohesive. If I fail, the options would be:

(1) Mount tweeter separately - not immediately adjacent to the mids,

(2) use an alternate tweeter that fits properly within a BMW midrange housing

(3) throw a Hail Mary and fabricate a custom grille for my a/d/s tweeters.

My starting point. This is a spare grille so I can mess around with it as a prototype:




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Discussion starter · #117 ·
Step 1: Scuff sand the outer lip, outer edge, and inner barrel with a rotary motion. I used a "medium" grit sanding sponge on the outside and a sheet of 120 grit by hand for the inside.

Thought is both to promote adhesion, and if it shows through the finish, to mimic the mill marks on the CT tweeter's aluminum trim.




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Discussion starter · #118 ·
Step 2 is a light-to-medium coat of Krylon Supermax Gloss Smoke Gray - which if you've followed my e46 build, when topcoated in satin, just happens to be a near perfect match for BMW Standard Gray interiors.

In this case, I'm using it as a plastics primer and will color change it ones it is cured to handle.




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Discussion starter · #119 ·
Since I went light on the primer, it cured quickly. Next comes a wet coat of POR-15 silver DTM topcoat - same stuff made an appearance on the rusty brackets I refurbished earlier this build.



Edited to add: those are drops of sweat, not paint. I somehow managed to not sweat on the part being painted.


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Discussion starter · #120 ·
The wet coat didn't quite pop the way I wanted, so here is a second wet coat while the first was still tacky. I expect dry-to-handle in 30 minutes, then finish with multiple coats of Rust-Oleum gloss acrylic lacquer.

(Yes, I'm just using what's on hand, but I'm also painting outdoors and this is a prototype, so forgive me).

I normally prefer a satin finish, but since I'm trying to match a bright aluminum part, gloss it is!




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