Choosing subwoofer size based on speaker size - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 16 Old 07-20-2019, 01:07 PM - Thread Starter
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Choosing subwoofer size based on speaker size

I just read at Crutchfield that choosing your sub size is based on your speaker size. It says if you are using satellite or bookshelf speakers, you should choose a 8" or 10" subwoofer. I've never heard this before. Do you guys agree with this ?

I have Infinity Primus P163 bookshelf speakers(6.5" woofers) for fronts, and am looking for a new sub.

Thanks.
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post #2 of 16 Old 07-20-2019, 01:10 PM
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post #3 of 16 Old 07-20-2019, 01:11 PM
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Quote:
Originally Posted by Jim McC View Post
Do you guys agree with this ?
Nope. Not at all.

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post #4 of 16 Old 07-20-2019, 01:16 PM
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That was the short version but guess for very very small speakers it might not be so great to spend 10-30 times the money for a nice sub with lacking speakers that need a very high crossover.

Others will probably have more and more complete information.


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post #5 of 16 Old 07-20-2019, 02:21 PM - Thread Starter
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Thanks. I assumed the guy at Crutchfield knew what he was talking about It's a short article about how to choose a subwoofer. But he does also say that if it's a large open area, you may need a larger sub.
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post #6 of 16 Old 07-21-2019, 08:04 AM
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Quote:
Originally Posted by Jim McC View Post
Thanks. I assumed the guy at Crutchfield knew what he was talking about It's a short article about how to choose a subwoofer. But he does also say that if it's a large open area, you may need a larger sub.
Can you post a link to the article?

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post #7 of 16 Old 07-21-2019, 02:19 PM - Thread Starter
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post #8 of 16 Old 07-21-2019, 02:52 PM
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Choosing subwoofer size based on speaker size

Quote:
Originally Posted by Jim McC View Post


That was an interesting read, guess he sets the bar low to appeal to the widest possible consumer base. Its a nice enough guide for those who are after small and somewhat inexpensive and only have a single place set out for a sub. He only has a single klipsch 112sw so unless hes been around a lot of other bigger systems his experience is pretty limited. I dont remember him even mentioning how important placement is for subs.


Edit: P.S. This text read a little more negative then i intended, its good to have easy to read guids for every level of consumer, the more ppl who have home theaters the better for all of us. Mentioning placement should be mandatory though

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post #9 of 16 Old 07-21-2019, 09:10 PM
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Telling people that the spot they have picked out for the subwoofer may not be a good spot would lessen sub sales. Thus, it is not mentioned.
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post #10 of 16 Old 07-21-2019, 09:23 PM
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Quote:
Originally Posted by Jim McC View Post
I just read at Crutchfield that choosing your sub size is based on your speaker size. It says if you are using satellite or bookshelf speakers, you should choose a 8" or 10" subwoofer. I've never heard this before. Do you guys agree with this ? I have Infinity Primus P163 bookshelf speakers(6.5" woofers) for fronts...
Therefore, according to my calculations, you need a 9.2" subwoofer. Ha ha. Eh...I see where Crutchfield is coming from but no I don't agree. Because if you have tiny speakers, then *maybe* a smaller sub could "go higher" but then it will tend to be more noticeable as a separate speaker plus most folks won't adjust the crossover so it won't be high enough anyway.
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post #11 of 16 Old 07-22-2019, 12:22 AM
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Originally Posted by RayGuy View Post
Telling people that the spot they have picked out for the subwoofer may not be a good spot would lessen sub sales. Thus, it is not mentioned.


I know, thats true but they could angle it a little more positivly like «more optimal» or something so customers think anywhere is fine but can get even better for free if they want.


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post #12 of 16 Old 07-31-2019, 06:51 AM
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Quote:
Originally Posted by Leeliemix View Post
That was an interesting read, guess he sets the bar low to appeal to the widest possible consumer base. Its a nice enough guide for those who are after small and somewhat inexpensive and only have a single place set out for a sub. He only has a single klipsch 112sw so unless hes been around a lot of other bigger systems his experience is pretty limited. I dont remember him even mentioning how important placement is for subs.


Edit: P.S. This text read a little more negative then i intended, its good to have easy to read guids for every level of consumer, the more ppl who have home theaters the better for all of us. Mentioning placement should be mandatory though

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You can always reduce the subwoofer level but if your sub is too small, there is no way to get more bass.
I used nothing more than 5 inch 2way book shelf speakers with a 12 inch sub for years and the sound was outstanding.
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post #13 of 16 Old 08-01-2019, 11:40 PM
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I believe the idea/theory here is that smaller subwoofers are going to have better transient response due to their smaller size, allowing them to blend better with small woofer satellites/bookshelves at the higher frequency crossover levels they typically require. Larger subwoofers with slower transient response at higher frequencies can lead to localization and worse integration with smaller speakers. I think if your speakers are large enough to at least achieve an 80hz crossover (the generally accepted level where subwoofer localization is difficult), subwoofer size isn’t as much of a consideration.

Someone with more knowledge can chime in, but this is how I understand this from my research.
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post #14 of 16 Old 08-02-2019, 12:33 AM
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Originally Posted by rbt192 View Post
I believe the idea/theory here is that smaller subwoofers are going to have better transient response due to their smaller size, allowing them to blend better with small woofer satellites/bookshelves at the higher frequency crossover levels they typically require. Larger subwoofers with slower transient response at higher frequencies can lead to localization and worse integration with smaller speakers. I think if your speakers are large enough to at least achieve an 80hz crossover (the generally accepted level where subwoofer localization is difficult), subwoofer size isn’t as much of a consideration.



Someone with more knowledge can chime in, but this is how I understand this from my research.


100Hz is considered difficult. 80Hz even more so. Even at 120Hz its not supposed to be easy. Distortion and noise from cabinet or ports will often go higher in frequency and are the main culprits in localizing a sub.
If you are in Home Theater In a Box territory with 150/200Hz crossover then size might be a concern but then its not so much a sub-woofer but a woofer. I’m splitting hairs I know but apart from a few exceptions a bigger sub would be preferable in most cases.


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post #15 of 16 Old 08-02-2019, 09:46 AM
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Originally Posted by Leeliemix View Post
100Hz is considered difficult. 80Hz even more so. Even at 120Hz its not supposed to be easy. Distortion and noise from cabinet or ports will often go higher in frequency and are the main culprits in localizing a sub.
If you are in Home Theater In a Box territory with 150/200Hz crossover then size might be a concern but then its not so much a sub-woofer but a woofer. I’m splitting hairs I know but apart from a few exceptions a bigger sub would be preferable in most cases.
Transient response has to do with many things, not the size of the driver. One of the sayings of AVS is "Welcome to the rabbit hole" and there is plenty of rules of thumb out there that do not apply. Sometimes complex questions don't have simple answers, transient response has many factors to it and the bus to the rabbit hole is about to board!

Wouldn't it be great if there was a website that tested, built, modified subwoofers and tested them outside in an open field with a 20 KW amplifier to give pages and pages of results? There is! It is called data-bass.com and they do just that. You get distortion readings, transient response, frequency response, polar charts, efficiency ratings, power compression charts, maximum power testing, impedance and inductance charts and so on at a click of your mouse. They also provide educational advice of how these things work. If you so choose, there are designs there that will blow the windows out of your room, crack the grout in your tile and can cause damage to the structure of your house.

Here is some information and mythology surrounding subwoofers--many of the myths started in car audio and have legs. A good place to start and you can compare many different subwoofers and their performance quite easily.

https://data-bass.com/#/articles/5cb...d0ec?_k=leqh8i

As far as "helpful advice" from companies that sell audio gear goes--they are trying to help people that have no clue what is going on. Crutchfield sells audio gear at MSRP, there is plenty of useless audio products they sell so be aware their "information" will not negatively effect profits. That is the nature of the beast, they have to eat also! Be aware that most "helpful hints" offered by retailers help them first and maybe you eventuallly. They do give you a very basic clue to what specifications mean but it is aimed at people that need to know the basics. Once you get that, then continue in your education and learn why things work the way they do. This is much harder to do and requires much more in depth training. I'm sure the person that goes to Crutchfield does not want to read hundreds of pages of text, math, physics and anatomy/physiology to purchase a pair of speakers. They would probably lose a lot of sales if they did.

A poor analogy but I've never been "taught" about valve overlap of car engines, the effects off too much VS not enough from a car salesmen. Most people don't want to hang around at car dealers all day learning about things like that so the valve overlap salesmen would be out of a job quickly. A weak analogy I know--but along the same lines.

You can also "learn" why $10,000 power cords "matter" or why you should put green marker on your CDs and DVS to "improve the sound" from PS Audio There is a lot of audio BS out there and it is a proud traditon dating back well into before we were born. Some BS has legs, it was wrong at the beginning, it was wrong 20 years ago and it is still wrong now. Part of the reason is basic human failings, we tend to memorize small amounts of information and repeat it instead of diving into the books. Teenagers are good at that, the giant wings on the back of their FWD cars complete with tail pipes the size of sewer pipes. That madness tends to vanish as we get older, wiser and such...or if we still care about car performance.

I can't blame Crutchfield for putting out very basic information to help people that don't understand the specs--we all have been there. I also can't blame them for providing information that is not complete so to negatively effect their bottom line--they need to make a profit, keep the lights on and the taxes paid. It is really hard to write educational material for an unknown audience--you might both confuse the fresh nwe faces and offend the intelligence of the more educated in the group. A tough balancing act as anyone that had to provide training for a large group of people.

However, if you really want to know--that information is available on the internet. To help guide you, start off with "third party" training where they are not trying to sell something. Data-bass is great because the guy is not selling anything, spends a ton of money on test gear (measurement sensor is $2,000 alone) and tells you why he does such things. Some manufacturers will provide accurate information and it will become adopted by AES (Audio Engineering Society) plenty of Harmon Internation research is in their technical library for that reason. If you want to see how deep the rabbit hole goes, start reading technical papers from AES... woooo! They get very technical so be forewarned.

Enjoy the read, take a look at some of the more insane subwoofers out there--all part of the fun. Good luck!
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post #16 of 16 Old 08-02-2019, 11:14 AM
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The reason I can think of for pairing smaller sub drivers with smaller speakers is related to bandwidth, which does affect transient response, but not really relevant... "Transient" stuff happens well above subwoofer frequencies.

Larger cones generally break up (have modes in the driver's surface) at lower frequencies than smaller cones, and as a result (partially, anyway) have more limited upper (to avoid "high") frequency response. An 8" sub might be able to handle 250 Hz whilst a 24" may not, and a larger sub probably specs a lower high-frequency cutoff (e.g. 150 Hz for a 15" instead of 250 Hz for an 8" just to pick a couple I quickly Googled).

But these days most all subs should handle the LFE bandwidth of 160 Hz (IIRC) or so, thus unless you are adding a sub to your 2" mini-speakers that roll off below 250 Hz, sub size with respect to the main speakers does not matter. If your crossover is at 80~100 Hz it is a non-issue. A good sub is a major purchase that should last for years so I'd get the bestest, biggest I could. Chances are many other things will be changed or "upgraded" before you need to replace the sub again.

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