Ask an Acoustic Engineer (me)

[Pb82 Ronin]

If speaker orientation remains the same when on the highway as when tuning in the garage, wouldn't something other than orientation account for the difference?

I don't know...truth be told, output isn't that great even when sitting in the garage tuning. It just gets worse when road noise is present.

[erinh]

Eliminate variables. Pull the car out of the garage and park it in the driveway or in the street, away from any large buildings/house. Does it sound the same as it did when in the garage or does all the bass vanish?

If the issue happens once the car leaves the garage then I have to think there's something going on in your garage; like you're basically at the mercy of the room within a room effect.
If the issue is only while you're driving then it would seem the road/wind noise is canceling out the response.

Though, truthfully, both of those wiping out 60-500hz seems like a stretch to me.

Anyway, answer the first question. Then you'll know what path to take toward further troubleshooting.

[Pb82 Ronin]

It sounds close...but a minimal change is detectable.

[erinh]

Do you have an RTA setup you can use to test in garage vs outside garage? You could also test while driving but I’d recommend you get help with that and make sure to have them with you in both scenarios so the only thing changing is the driving aspect.

[Justin Zazzi]

All i can hear is from about 500 Hz and up, and 60 hz and lower. It's the strangest and most frustrating phenomenon ever.

So if ~60hz and lower is intact, your subwoofer seems to be working alright.

A hole between ~60z and ~500hz sounds like a midbass driver problem since that's the only speaker playing that range.

I would continue looking at the difference of just parking outside like Erin suggested. I don't think that'll be the fix-all, but it's a good thing to double-check.

Also, what is the other difference between the garage and highway? Velocity. Are you using any of the factory radio or amplifier? Is there any active noise cancellation built in to the car or is there any automatic volume control that adapts the volume to the vehicle speed? This sounds like it could be a dynamic filter fighting against you somehow?

What is the signal chain between your music source (phone?) and your speaker? Bluetooth to a factory radio? Phone straight to an aftermarket DSP? That might help us think it through with you.

Also, did this problem appear suddenly or has it been like this for a while? Has it ever worked right? If it did work right before, what did you change between then and now?

[mauian]

Hey Justin, this might be a dumb question but is it a bad idea to set gains on an amp or input sensitivities on a DSP with a sine sweep? I’ve just seen many methods using 40hz and 1000hz sine waves and a limitation as pointed out by Andy at Audiofrog is that this doesn’t cover the whole spectrum so you could have a boost at 30Hz (or pick any other frequency) that could be generating distortion that you might not be picking up on if only using a 40hz sine wave. Some people use multiple sine waves...

While it may be overkill, any reason not to use a sine sweep?

If it’s ok, I would think a linear sine sweep would be best (as opposed to logarithmic) for consistent energy across the spectrum (if detecting distortion with a DD-1 or LED light on amp/dsp)?

On a related note, could white noise be used too to send equal energy across the spectrum all at once?

thanks!


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[Pb82 Ronin]

Do you have an RTA setup you can use to test in garage vs outside garage? You could also test while driving but I’d recommend you get help with that and make sure to have them with you in both scenarios so the only thing changing is the driving aspect.

I believe this setup is slightly better than a single Mic/RTA (Courtesy of Darkridr)

So if ~60hz and lower is intact, your subwoofer seems to be working alright. It is...I wonder if the box is the butt-head here.

A hole between ~60z and ~500hz sounds like a midbass driver problem since that's the only speaker playing that range. Running the mids (6.5" KX2) from 85 -1100 Hz. We did do a quick function check to verify they're working.

I would continue looking at the difference of just parking outside like Erin suggested. I don't think that'll be the fix-all, but it's a good thing to double-check. We can try...not sure if the cords will extend that far...

Also, what is the other difference between the garage and highway? Velocity. Are you using any of the factory radio or amplifier? Is there any active noise cancellation built in to the car or is there any automatic volume control that adapts the volume to the vehicle speed? This sounds like it could be a dynamic filter fighting against you somehow?

Zero connections to anything OEM. On purpose...Bose is garbage. No noise cancellation stuff, or anything in the DSP other than the filters we choose.

What is the signal chain between your music source (phone?) and your speaker? Bluetooth to a factory radio? Phone straight to an aftermarket DSP? That might help us think it through with you.

Direct connect to HU by either 3.5MM jack (when tuning) or direct USB iPod connection. Even have FLAC files to play with.

Also, did this problem appear suddenly or has it been like this for a while? Has it ever worked right? If it did work right before, what did you change between then and now?

Been like this since we started tuning. Every time we have a great tune emerge in the garage, the sound quality goes away the moment I hit the highway. I think one of the main contributing factors could be wind/road/tire noise passively cancelling the mid-bass frequencies. I realize that's a stretch...but at this point we have HOURS of tuning in this setup and multiple tunes. Some sounded good, some sounded great, and some sounded awful. Obviously, we finish on the "great" sounding ones...then I go for a drive. Then...it all goes to crap wihtout making a single change. Poopiest feeling ever because my bro has helped me so many times that his wife probably hates me now. LOL!

Responses in blue (or pics...LOL)

[Fernpatch]

I honestly suspect you are having road noise masking some or all of the sound that goes missing on the road. I have battled a very similar issue in my car. my solution in progress is developing 2 eq presets. one for critical listening when parked and a second with some boosts applied to the problem areas while driving. it may not be the "correct" way to go about it but it is the best solution that I have found thus far for vanishing mid bass and lower mid range in my own vehicle.

[Justin Zazzi]

Hey Justin, this might be a dumb question but is it a bad idea to set gains on an amp or input sensitivities on a DSP with a sine sweep? I’ve just seen many methods using 40hz and 1000hz sine waves and a limitation as pointed out by Andy at Audiofrog is that this doesn’t cover the whole spectrum so you could have a boost at 30Hz (or pick any other frequency) that could be generating distortion that you might not be picking up on if only using a 40hz sine wave. Some people use multiple sine waves...

While it may be overkill, any reason not to use a sine sweep?

Not a dumb question.

I used to be super crazy careful about amplifier gain settings and I used an oscilloscope and everything. I realized a single sine tone can be hit or miss like you mention because there might be boosts or cuts all over the place. So then I did a sweep and looked for the hottest frequency (electrically at the speaker terminals) then I used that sine tone to set the gains.

Later I realized if you set gains, then tune, chances are you're going to make a lot of cuts and so your gain structure will not be what you thought it was. The system can wind up a lot more quiet than you intended.

How often has this happened: you set gains, you spend all day tuning until it's just right, you either share with a friend or you listen the next day, you realize it is not loud enough, you adjust the gains, you spend all day tuning until it's just right .... and round and round.

I like one of Andy's recent posts about setting gains last. I wound up with a very similar idea before I saw his post. In short it goes like this:
-if your system is not loud enough, increase gains.
-if you system has too much noise floor or hiss, reduce gains.

There are many ways to get fancy about finding the balance between loudness and quality but many of them are difficult or impossible with simple tools like REW. I find the ears are the best tool for the job unless you don't know what to listen for, then you borrow your friends' ears.

If it’s ok, I would think a linear sine sweep would be best (as opposed to logarithmic) for consistent energy across the spectrum (if detecting distortion with a DD-1 or LED light on amp/dsp)?

I'm not sure how the DD-1 works, but the C.L.E.A.N. gain setting lights on the Rockford amps I use are pretty reliable no matter what I'm doing. A linear sweep might not be a bad idea, but similar to above I think it's a bit overkill unless you have no other way to listen for it.

On a related note, could white noise be used too to send equal energy across the spectrum all at once?

You could, but setting gains is usually hunting for a threshold of clipping the input or output of a device and then looking for the resulting distortion to see when you found the threshold. White noise or any continuous noise would be a poor choice since distortion is much harder to see unless you have really sophisticated (read expensive) tools.

[Justin Zazzi]

I don't know...truth be told, output isn't that great even when sitting in the garage tuning. It just gets worse when road noise is present.

I think I'm with Fernpatch on this one. Driving on the highway, no matter how quiet your car is, will not sound the same as in the garage. I like the idea of two presets. I have been making use of the "bass" feature on my radio to make small adjustments as I drive. Not much else you can do unless you have access to a DSP with speed-controlled compensation.

You could get something like this Analog Devices demo board and craft your own DSP inside it complete with speed-sensitive filters, but you'd also need a speed sensor to feed it. You might use a CAN or OBDII interface to grab velocity signals. That would be a fun project.

https://www.digikey.com/product-deta...66Z-ND/7915254