KHA does an SPL build - 1996 Astro Van

[keep_hope_alive Premium Member]

So you all know me for my preference for accurate musical reproduction (SQ).

I've helped with SPL focused competition vehicles over the years.

Now comes a hybrid for a long-time friend (25 years and counting). We'll call him "The Brian".

A van that will be SQ for most of the time and SPL for some of the time.

Equipment is as follows:

Head Unit: Clarion C500

Front Comps: JL Audio C5

Front Amp: Boston Acoustics GT-475

Sub: Fi 18BL

Sub Amp: Massive Audio N4

AGM battery up front, AGM battery rear, 1/0 wiring.

originally, the HU and comps are installed. I will redo them totally.

I put in a new amp rack and wired up the N4 already.

I loaned The Brian a sub (Vega 124) in an enclosure - one i normally use for my HT.

We have the 18BL.

The GT-475 is on it's way.

So, the first thing with a hybrid SPL vehicle is determining where the vehicle will peak - this can be mathematically determined or empirically determined. We did both.

Before we get into math, let's start with the testing (done last night).

I created a 20Hz-100Hz sweep with a total duration of 5 minutes.

I used TrueRTA, a ECM8000 mic, and a SoundDevices USBpre to measure response in real-time.

I placed the mic at the passenger windshield corner - isolated with foam.

I removed bass boost and EQ, and removed crossover and minimized subsonic filtering.

Using the HU, amp, and Vega124 in a "sealed" enclosure (vent was closed off) I played the sweep.

I measured peak SPL on the RTA in an insulated garage with a low noise floor.

I repeated the measurement with a few sub locations (both driver and passenger rear corners) - Magenta and Yellow lines.

I then removed the sub from the van, placed it on sawhorses, and measured the response near-field (1 meter) - Blue line.

The graphs below are the results:

We can see the blue line follows the typical closed box response curve.

In the van, we get a peak at 45Hz.

Click to read more...

 

[neo_styles 10+ year member]

Glad to see you're using the GT475. I've been pretty happy with my 2125 so far and really hope more people get a chance to put these Bostons in their lineup before they aren't available any more.

 

[keep_hope_alive Premium Member]

Some of you may remember me talking about a concrete enclosure plan. This is that vehicle. But phase 1 will not be concrete. Instead, 1.5" to 2.25" thick enclosure walls. The enclosure will be a slanted front prism with a slot port tuned to 45Hz.

I'm working the enclosure plans up in Google SketchUp and AutoCAD. I'll share them soon.

Here are some quick pics of the current progress.

I'll make a beauty panel to cover up the amp rack

rear battery is fused

front battery is fused and big 3 grounding done

the Fi 18BL

 

[keep_hope_alive Premium Member]

Glad to see you're using the GT475. I've been pretty happy with my 2125 so far and really hope more people get a chance to put these Bostons in their lineup before they aren't available any more.

We almost went with the GT-2200. it's the same price right now (only $200!!!) and would be great for the front comps. But given the size of the van and The Brian wanting encompassing sound - we'll get some rear speakers in also and want them amplified.

 

[keep_hope_alive Premium Member]

Further, the van will be setup with removable baffles to turn everything rear of the C-pillars into a giant horn. This will alleviate a lot of concern with losses and flexing in the rear half of the van. I will have sketches of this as well.

 

[neo_styles 10+ year member]

We almost went with the GT-2200. it's the same price right now (only $200!!!) and would be great for the front comps. But given the size of the van and The Brian wanting encompassing sound - we'll get some rear speakers in also and want them amplified.

Fair 'nuff. I've been trying to convince a couple people to go with the 275 or 475 as well who aren't able to have their speakers keep up with their subs. That 275 and the 2125 as well are just so small! The more I talk about this, the more I realize I need to start strapping cash away for another 2125. Especially since I'm having more and more trouble trying to eke out a more powerful midrange from the Kenwood I've got on speaker duty ATM.

 

[Durango03 10+ year member]

In for the win!! KHA's work always leaves me in awe.. truely one of the best on CA

 

[04murdalanche]

In for the win!! KHA's work always leaves me in awe.. truely one of the best on CA

SQ wise probably THE best.. looking forward to those CADs and sketches!

 

[itsblown 10+ year member]

cant wait to see this

 

[mlstrass 5,000+ posts]

Will this van be at any IL/WI/IN shows this year?

 

[DB-Audio 10+ year member]

looks promising

 

[keep_hope_alive Premium Member]

i'm about halfway done cutting the wood for this design

longer section is tuned to 28Hz, the shorter section to 45Hz. Wood plugs will be used to switch between ports.

this is how my angles are coming out (the bottom two are the faceplates where the sub will mount). i'll have two layers on top (one more to the left).

all using a circular saw and guide

 

[keep_hope_alive Premium Member]

Will this van be at any IL/WI/IN shows this year?

I would like it to make it to Bloomington, IL on April 28th.

A buddy of his is having a local sound-off next Sunday. I don't think it'll be done setting up by then. i want to start gluing tomorrow, but we'll see.

I made the faceplate (where the sub mounts) shorter to make wood conservation work out (we have 48"x48" pieces of 3/4" MDF). originally i was looking at this layout where each port was side-by-side, but ran into a physical mounting conflict with sub depth

 

[mlstrass 5,000+ posts]

Not sure if I'm doing bloomington yet as that's a long haul. If I do make it down I'll be sure to look you up....

 

[keep_hope_alive Premium Member]

Not sure if I'm doing bloomington yet as that's a long haul. If I do make it down I'll be sure to look you up....

if there is anything around Chicago we may be down for making that trip as well.