Trying be become more than an average consumer

[bretburrill]

I learned of Audioholics on youtube and have been watching the informative videos there. I'm mostly interested learning how to test subwoofers myself. I've been in to mobile audio for close to 30 years and will someday upgrade my home stereo to something nice, but for now I'm applying everything I learn to mobile audio. I realize this is not the place for this and understand that many of you might be biased against mobile audio, but I hope you will bear with me and just help me learn as much as I can.

The reason I came to this forum is because I have found it impossible to have a car subwoofer discussion where people back up their claims with factual information. I have read the Audioholics speaker review criteria on the web site and it gave me a big ole' headache. I don't have enough knowledge to follow a lot of it. I will spend time to understand it better but have to get some basic knowledge first.

I have looked at lots of response curves and have always assumed this was showing the loudness of a range of frequencies. This is usually the only graph based data given by car audio subwoofer manufacturers. What I'm equally interested in is the accuracy of the speaker, but nobody shows data for this as far as I can tell. When reading the Audioholic's test criteria I either skipped over the accuracy testing or maybe the name for it isn't 'accuracy,' so I missed it. Or maybe you don't test for accuracy. Please help me understand.

The reason I'm interested in this is because I have always bought the high SQ subs (15") and have found that the differing notes in the upper (50+Hz?) range all sound kind of the same. There are many variables that can cause this, so I can't be sure it's entirely attributable to the speaker's design. Now I have some 10" subs that seem to be very accurate in that range but don't play 30Hz frequencies with any authority. I understand porting and am not interested in about a discussion about enclosure design to tune to specific frequencies. I'm I interested in learning what makes some speakers more accurate than others. I've had countless arguments over this and people in the car audio world insist that speaker size has nothing to do with accuracy. Maybe they are right and I'm doing something wrong. I'm open minded. I hope this topic has not already been beat to death on here, I just joined and apologize if I'm bringing up an overly discussed topic. Thanks for reading.

Bret

 

[BoredSysAdmin]

https://www.audioholics.com/loudspeaker-design/subwoofer-measurement-part-1

 

[shadyJ]

I would say cone diameter has nothing to do with sound quality. If you want to know about sound quality in bass frequencies, here is an in-depth article for you. Regarding Audiholics testing for accuracy, almost all of the graphs published in the subwoofer reviews are tests for accuracy. They test for various types of distortion, and less distortion means more accuracy. If you want to know the meaning of a specific test, just ask here and we can better explain it to you.

 

[Bucknekked]

I would say cone diameter has nothing to do with sound quality. If you want to know about sound quality in bass frequencies, here is an in-depth article for you. Regarding Audiholics testing for accuracy, almost all of the graphs published in the subwoofer reviews are tests for accuracy. They test for various types of distortion, and less distortion means more accuracy. If you want to know the meaning of a specific test, just ask here and we can better explain it to you.

I'm with @shadyJ on this one. How large your speaker is doesn't correlate to how accurate the sound may be.
Shadyj is pretty sharp with subs and has a pretty cool thread you may wish to check out called SUBWOOFER CANDY.

If you want some tunes to test out your subs, check out his thread. Its got stuff to rattle your teeth, and it shows you the spectrographs of most of the songs so you can see what frequencies are actually getting played.

Just because its big, like a 15 inch, doesn't mean its any good. Just because its modest, like a 10", doesn't mean it won't bring the thunder. If it were that simple, well, audio as a hobby wouldn't be much of a hobby.

 

[TLS Guy]

I learned of Audioholics on youtube and have been watching the informative videos there. I'm mostly interested learning how to test subwoofers myself. I've been in to mobile audio for close to 30 years and will someday upgrade my home stereo to something nice, but for now I'm applying everything I learn to mobile audio. I realize this is not the place for this and understand that many of you might be biased against mobile audio, but I hope you will bear with me and just help me learn as much as I can.

The reason I came to this forum is because I have found it impossible to have a car subwoofer discussion where people back up their claims with factual information. I have read the Audioholics speaker review criteria on the web site and it gave me a big ole' headache. I don't have enough knowledge to follow a lot of it. I will spend time to understand it better but have to get some basic knowledge first.

I have looked at lots of response curves and have always assumed this was showing the loudness of a range of frequencies. This is usually the only graph based data given by car audio subwoofer manufacturers. What I'm equally interested in is the accuracy of the speaker, but nobody shows data for this as far as I can tell. When reading the Audioholic's test criteria I either skipped over the accuracy testing or maybe the name for it isn't 'accuracy,' so I missed it. Or maybe you don't test for accuracy. Please help me understand.

The reason I'm interested in this is because I have always bought the high SQ subs (15") and have found that the differing notes in the upper (50+Hz?) range all sound kind of the same. There are many variables that can cause this, so I can't be sure it's entirely attributable to the speaker's design. Now I have some 10" subs that seem to be very accurate in that range but don't play 30Hz frequencies with any authority. I understand porting and am not interested in about a discussion about enclosure design to tune to specific frequencies. I'm I interested in learning what makes some speakers more accurate than others. I've had countless arguments over this and people in the car audio world insist that speaker size has nothing to do with accuracy. Maybe they are right and I'm doing something wrong. I'm open minded. I hope this topic has not already been beat to death on here, I just joined and apologize if I'm bringing up an overly discussed topic. Thanks for reading.

Bret

We don't get into mobile audio much here. But actually the design of a car sub and a domestic sub is very different. The closest we get is when someone wants to use a car sub for his home audio, which is invariably a bad idea.

The whole issue of the difference revolves around cabin gain. Drivers for car subs are designed with a peaked response centered around 100 Hz. You want the response to fall below that point. As the small space of the car boosts the response a lot below that point. In general sealed options are best suited to car subs.

Now if you test a good car sub outside the car you will get a dreadful response.

Now the other issue is that all cars are different. So actually you do have to design the sub for the car.

This is one area where DIY is going to die. For one thing car audio is now integrated with the head unit, and altering it invalidates the warranty. The other issue is that high frequency digital voltage regulators running in the mega Hz ranges are keeping the vehicles electrical buses awash on high frequency RF. This means when you use your custom electronics all you are likely to get is a loud buzz, and very loud at that.

Now many car manufacturers have invested millions in vehicle audio. Audi has really led the way here. Other firms such as Pioneer, KEF Harmon International have invested millions also. That means that if you buy a higher end vehicle it is very unlikely you will improve it. The manufacturer can design the system to the cars electrical system and the vehicle acoustics.

I bought the top end Chevy Equinox, which comes wit the high end Pioneer system. It sounds very good indeed, with the rear sealed sub superbly well integrated. I'm certain I could not improve things in that cab environment.

So if you are going to test subs you will need to know how to measure the environment in which it will be located AND do your sub measurements in cab with the doors closed, with the sub placed where you intend to install it.

Bottom line good domestic sub drivers will have far too much bass in cab. Good car drivers will be very bass deficient in the home as a rule.

I encounter the problem here when people have already bought an expensive sub driver and ask it to be modeled for home audio. I can usually tell from the T/S specs it is a looser. I do the model anyway and end up finding the classic auto sub response, and have to tell the OP they have bought a driver unsuitable for domestic audio.

 

[rojo]

I agree with most of the above. Car sub drivers usually have a higher resonant frequency than home sub drivers. Car sub drivers are intended to leverage cabin gain to reproduce sub bass at audible levels, and so the anechoic response tends to drop sharply around 40 Hz. I don't necessarily agree that sealed subs are better than vented for a car, though. After all, vented subs are much more efficient, so you can often do more with less. I've heard very impressive vented 8's, but it certainly helps that they were in vehicles with small cabins such as pickup trucks and compact hatchbacks Sedans and SUVs do tend to benefit from slightly lower tuning I think.

Anyway, if you're looking to quantify your subwoofer sound quality, consider purchasing a calibrated measurement microphone such as the miniDSP UMIK-1 or Dayton UMM-6 and using a laptop to measure sweeps with the free Room EQ Wizard. You might also consider a miniDSP 2x4 and 4way Advanced software plugin to flatten the response of your subs, perhaps salting to taste with a 1.5dB / octave increase from 100Hz down to infrasonics; to flatten the response of your stereo mains; and to time align your subs with your mains at the driver's seat.

Regarding driver performance, the measurements on home subwoofers you see from Audioholics reviewers are always performed on subwoofer systems -- that is, subwoofer, enclosure, and amplifier. Not much is ever published about a sub driver's Thiele-Small parameters or other behaviors, such as its linearity between push and pull at different power levels. Fidelity of timbre often relies on these behaviors, but unfortunately not much literature exists to help you pick and choose drivers based on these criteria. In general, though, you get what you pay for. For example, a JL Audio 12w6 will get you a more linear BL(x) at power (and therefore, lower harmonic distortion) than, say, an MTX Audio 12". That's not to say the MTX sub would sound worse at lower wattage, assuming both JL and MTX live in proper boxes designed around their T/S params.

And speaking of T/S params, rather than trusting the manufacturer's recommended box sizes, try modeling your sub drivers using WinISD. For a car, shoot for a response that's reasonably flat down to 40 Hz. Cabin gain ought to take care of the rest. For vented subs, pay attention to the vent air velocity, and don't let it exceed 20 meters / second at 120 watts or so to avoid audible chuffing. Experience will let you fine tune your expected performance based on the models you create.

But someone who installs subs for a living would probably be better equipped to predict what sort of tuning works best in a hatchback versus sedan, versus SUV.

 

[bretburrill]

Thank you all for giving such thoughtful answers, all of you. There is so much to respond to I don't know where to begin. I'm going to give this some thought and try to give a worthy response, but quickly I will say a few things. The resonant frequency of my 10's is 29Hz. I do understand that the space inside a car has a resonant frequency and the SPL guys tune their boxes to this and it is usually around 40Hz, if I'm not mistaken. With regard to sealed enclosures, many people do believe that sealed will give you the flattest response. The manufacturer of my 15" subs recommended sealed for a flat response. The 10's I have now could benefit from a ported enclosure tuned to 30Hz because in a sealed box they don't hit sub 40hz frequencies with much volume, so I would argue that they might have a flatter curve down to low frequencies in a ported enclosure. I'm definitely not an expert yet, so please don't take this as any disrespect. It's not clear to me why my 15's were so muddy, but there are so many variables involved I really might never know (cabin size and amplifier performance). They played crystal clear at very low (30Hz) frequencies.

I did suspect that distortion was what I was thinking of as inaccuracy. It makes sense that if a speaker doesn't play the frequency its given, accurately that would be defined as distortion, I just never thought of it that way before. I always assumed distortion was artifacts, which I see isn't the case.

I'm missing some points I know I just need time to think about this and respond later. Thanks for taking me seriously and responding despite being car audio related. I'm really happy to have a meaningful discussion for a change.

 

[Swerd]

I'm I interested in learning what makes some speakers more accurate than others. I've had countless arguments over this and people in the car audio world insist that speaker size has nothing to do with accuracy. Maybe they are right and I'm doing something wrong. I'm open minded.

Building sub woofers for home audio and for cars are really two very different things. It may be difficult, but you would do well to forget what you've learned about what works well in cars. Because of your previous experience, you may find learning about home audio bass comes quicker than if you had no experience at all.

It's not clear to me why my 15's were so muddy, but there are so many variables involved I really might never know (cabin size and amplifier performance). They played crystal clear at very low (30Hz) frequencies.

Usually, a muddy sounding speaker comes from a poorly damped driver, cabinet design, or both. When these under-damped woofers get a single short tone, they continue on and on for several milliseconds. It's loud but muddy sounding. This is often referred to as 'high Q'. The same driver, in a cabinet designed to provide enough damping (low Q),will produce a single short-lived tone. It's all about T/S parameters and designing a cabinet with low Q. I don't know for certain, but I think car sub woofer builders ignore much of that in a quest for the loudest sound.

If you want to measure sub woofer performance, you really should also understand the basic principles to designing a cabinet for a woofer or sub woofer. It's actually pretty straight forward. Buy or borrow a copy of Speaker Building 201 by Ray Alden and read the first 4 chapters. It involves some math, but is limited to high school algebra.

Once you know the T/S parameters of a driver, and decide what level of Q you want, it's a straight forward process. Q seems like it's mysterious, but it helps to think of it as a way to describe the low end roll-off curve of a woofer. Q is a ratio that has no units. You vary it by changing cabinet and port (if any) dimensions. A Q of 1 or higher makes for a loud but muddy sounding woofer. It often is used to exaggerate the performance of poor quality woofers. Q of 0.7 or less gets rid of the muddiness at the expense of loudness and low frequency reach. All this is clearly explained in Speaker Building 201.

And finally, welcome to Audioholics .