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Radio install under glove box

Fresbone

Fresbone

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This pertains to a Jeepster, but is kind of a generic question about aftermarket plastic glove boxes.

I am installing a “sound system” in my Jeepster consisting of a Ghost Box 3.0, which is a “hidden head unit” that is essentially a Bluetooth receiver with an amplifier and a Retrosound 4x10 dash speaker which provides stereo output from one speaker. My goal is to have everything hidden using existing points of attachment. I will post more details as I go. Links to the products are below.

It looks like the ideal place for the head unit will be screwed to the bottom of the aftermarket plastic glove box (outside the glove box). This will be close to the speaker and power source, have good ventilation, not take up space inside the glove box, and not be too close to heater ducts. The head unit weighs 13 ounces. My question is whether the weight of the head unit would damage the glove box. I will either use fender washers or a 16ga plate to distribute the force of the four #8 machine screws used to attach it to the glove box.

Thanks in advance.


 
You control this unit via bluetooth and your phone?

Usually under-dash units are supported by a bezel that bolts to the bottom of the dash, and a backstrap.
The backstrap is typically like 14 ga perforated steel, which can be easily bent to reach a solid mount under the dash.

You can add a second backstrap, doubled or to another point, if one is not sturdy enough.

This is likely what I would do, rather than hang it from the plastic glove box shell.
 
It powers on with ignition and connects to your phone. Your phone does everything including the equalizer.

It’s not really an under dash. The market looks like it if for owners of small Japanese cars who want to look at a radio delete instead of a radio. I don’t really get that. The installation videos show people stuffing it behind the dash and zip tieing it in place.
IMG_8020.png
 
I have a hard enough time composing a simple text message on my phone, just standing still.
Hitting the touch screen buttons in my KL seems like a risky action when driving.
I'd be scared of having a wreck while I tried to manipulate the stereo.
No thank you.
Buttons, knobs: good.
JMO.
 
timgr said:
I have a hard enough time composing a simple text message on my phone, just standing still.
Hitting the touch screen buttons in my KL seems like a risky action when driving.
I'd be scared of having a wreck while I tried to manipulate the stereo.
No thank you.
Buttons, knobs: good.
JMO.
Click to expand...
Then add operating a stick shift…

My vision is start something when I turn the car on, leave it alone when I drive. Out in California, it’s illegal to goof around on your phone while driving.
 
So far, I am reasonably happy with this setup. Goals accomplished:
1. Completely inconspicuous. Other than 2 screws and a plate acting like a washer in the glove compartment, there is no evidence of a radio.
2. I have tunes via a very simple setup. This has automatically connected to my phone every time I start the engine. It takes about 10 seconds. I can select a playlist and drop the phone in my console and roll.

Here's what I don't like. It sounds ok at low to medium volumes. It sounds better when I monkey with the EQ on Spotify, but it is still tough to hear vocals and it lacks mid to mid-deep range. It also distorts (not sure if I am describing it correctly) when I max out the volume. I'm not expecting it to sound great, and I would say it has already almost med my expectations with respect to sound, and far surpassed my expectations with respect to installation, ease of use, appearance, etc.

Chat GPT says it might sound better boxed in and with a small format, high output amp. RetroSound (speaker manufacturer) says the speaers don't need to be boxed in, but they are generally made for a small compartment as you would see in a dash, not a completely open space like we have. I am waiting on some information from the head unit manufacturer before getting an amp. The head unit indicated 50W/channel, but I don't know if that is max or RMS. The speaker specs are
  • handles up to 90 watts RMS (160 watts peak power)
  • frequency response: 43-21,000 Hz
  • sensitivity: 87 dB.
For now, I am going to start exploring a box and see what that does. I will keep you all posted.
 
Fresbone said:
10 amp fuse.
Click to expand...

:(

At 10 amps & 14.5 volts the theoretical maximum power out is 145 watts RMS. In reality with 10 amps fusing you're probably not drawing more than 6 or 7 amps with the volume cranked to 11, at 100% efficiency that's a little over 100 watts, or 25 per channel. A class D amp is probably ~90% efficient at best, if the amp is based on older tech, i.e. class B, then it's going to be closer 35 to 40%.

So no, your amp is not 200 watts RMS. If they're dishonest enough to fudge the figures by at least 100% then they're probably dishonest enough to lie about it even more. I'm guessing the real output is probably well south of 15 watts/channel.
 
Audio amps typically have enough gain to go well into clipping (distortion!)
There is nothing to prevent you from overdriving the amplifier with a strong input.
Additionally, the best sound / least distortion comes from the lowest volume levels - that first watt.
I would connect a 'scope and look at the amplified output from a function generator.

Is 87dB the speaker rating?
There's a standard - the 87 dB is the SPL (sound pressure level) from a 1 watt input at 1 meter.
87 db is lowish-medium efficiency, typical for small home speakers.
Probably the easiest way to get more volume is to increase the speaker efficiency.
A larger full range driver (no crossover) if you can finagle it.
Crossovers reduce efficiency.
Larger will be more efficient - less power to move the same volume of air.

The seller probably treats the speaker as an infinite baffle configuration.
You can look it up -
One possble might be a ported cabinet with a more efficient driver.
Or if your small drivers are not distorting you could go to a more powerful amp.
I expect they exist - I imagine you'd need to have an inverter stage to increase the voltage ahead of the amplification.

As Howard points out, power equals voltage times current.
 
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I feel like I am starting to understand electronics, but audio electronics is just plain spooky! I have a lot of reading to do.
 
I went with a Pioneer Digital Receiver no tape or CD deck but it does have Blue tooth and input from a USB drive. Then a pair of Pioneer 6" 3 way speakers in boxes in the back of my hard top. It rocks out very nicely.
 
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My radio is long gone. Gonna steal my wife's bose tube if i need a stereo beyond my lantern speaker or ear buds.
 
timgr said:
Note rated 90dB efficient.
Decibels are logarithmic, thus this 3dB increase is twice the SPL of 87dB with the same input.
Just an example.
Likely the difference in dB is real, but the accuracy of the absolute numbers is suspect (like amp power).
Click to expand...
Note that the impedance (AC resistance) of the speaker also matters to the SPL produced.
Power can also be expressed as current squared times resistance (here impedance).
A speaker with an impedance of 4 ohms requires ca 70% (square root of 2) more power compared to an 8 ohm speaker.
Your evaluation of any replacment speaker needs to consider the impedance along with the SPL rating in dB.
 
Here is the update on this stereo. It sounds like trash. Absolutely no vocals, as in worse than dad’s old AM radio, which was my minimum standard I was trying to achieve. So, here is why I did:

1. Bought a pair of Polk Audio MM522 speakers for my CJ5 kick panels (borrowing ideas from Howard’s setup). My son 3D printed speaker housings. I connected them to the Ghost Box head unit and it actually sounded pretty good.

2. Had my son 3D print a speaker housing for the Retrosound 4x10. If actually made it sound worse, because it didn’t enhance the vocals and it killed the mid bass.

So, my conclusion is that the Retrosound 4x10 speaker is trash. I have no idea whether it is solely because of the speaker size or if it is because the speaker design/manufacturer.

Next steps:

1. I am going to get a Kicker KEY200.4 amp with a JL Audio MBT Bluetooth receiver for my CJ5 and hook up the Polk Audio speakers. If it sounds remarkably better than the Ghost Box, I will probably upgrade the Jeepster to that amp and Bluetooth receiver.

2. I’m going to try out some different speaker combinations to see what might fit behind the dash in the Jeepster. It may be that a pair of 4” speakers sounds better than the 4x10.

3. If that doesn’t work, I may need to bite the bullet and look into speakers on the transmission tunnel, in the kick spaces, or in front of the rear wheel wells.
 
Fresbone said:
I am going to get a Kicker KEY200.4 amp with a JL Audio MBT Bluetooth receiver for my CJ5 and hook up the Polk Audio speakers. If it sounds remarkably better than the Ghost Box, I will probably upgrade the Jeepster to that amp and Bluetooth receiver.
Click to expand...

That amp seems to be The Real Deal :)
 
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