Interesting Box design problem

That speaker is not happy in that box. I would try again. That relative gain graph really looks bad. What you should have is a smooth curve, and you don't. Vent velocity is a little too high. This box needs to be re-thinked.

It also shows excursion near its peak at 20Hz. Doesnt matter, if you have excursion problems at that frequency, your listening to noise. There is no music that low.

If you really need a peak at 30 Hz, get a 15-inch woofer.

The graph curve needs to be smooth

 

Excellent thought process, I do agree with you. The 10-inch woofer would be a much better idea. If your concerned with sound quality go with a sealed box. If you want a little more bass, then a ported box is your best bet.

Also retune your port to the middle 30s. You'll be much happier with the results. Also a 1.5 to 1.75 cu ft box will be a real good starting point for a 10-inch woofer

Keep us posted please

 

Here is the output for an Infinity 10 in a 1.75 cu ft box. The red graph is a box tuned at 38, the yellow is a box tuned to 32. Lets see what we have.

The F3 point for both tunings is pretty close. For the 38 HZ tuning we have an F3 point between 34 and 35 HZ. For the 32 Hz tuning, the F3 point is between 30 and 31 Hz.

The relative gain for the lower tuning is definately down. In fact its down between the 40 and 80 Hz range. Also the lower tuning box is peaking around 80 to 90 HZ. I really dont want my woofer to peak at that high a point.

The higher tuning has more gain (no suprise at all) at the lower frequency. Its response is smoother.

 

First there is NO music at 20Hz, let me repeat that, there is no music at 20Hz. A 20Hz signal is Noise. So we dont care.

Most speakers are ported because ported boxes are more efficient. Most people don't want a flat response, they like more bass. Be honest with yourself, you will also want more bass. Go with the ported box. Is the loudness feature on your radio on, of course it is. You wanted to extend the bass response. Bye Bye flat response. Did you turn you bass knob on your radio up? bye bye flat response.

Please be honest with yourself and you'll really enjoy your sound system.

By the way, None of you graphs show a response at 20Hz. Basically, ignore anything below the purple line.

Also I use BassBox Pro, its a really good program. Many installers use it because of its extremely accurate and realistic results. But mine and your results should still be a little closer.

Please post the thiele/small parameters that your using. I wanna see if I entered something wrong. Also, I'm sure you entered something wrong because an 8-inch woofer CANNOT play lower than a 10-inch woofer. Its physically not possible unless the 8-inch woofer has more surface area than the 10-inch woofer

 

ah Ranger......

good advice my friend.....


listen to this man.....we are on the same page in so many ways.

 

I think I want to help you understand what your seeing in that graph. And understand whats important. First, it sounds like you already did a little research so lets build on it.

First thing we need to realize is that we are dealing with a car, NOT a house. Also notice that in my graph properties I have the car checked. Here is why thats important. A car interior is much smaller than a living room. Much smaller. This is important because a 100 Hz wave is over 130-inches long. No problem in a house, but in a car it starts to be a problem. A 50 hz wave is around 270-inches long. We now have a problem. Our car is not 270 inches long. That wave cannot fully develope so sound starts to roll off. A 30 Hz wave is around 450 inches long. I know of no car with a 450-inch long interior. 30Hz in a car forget it. It won't happen

Many amateur box builders have no clue because they believe that tuning lower improves low frequency response. Those so called experts are idiots. Now, I'm no expert. I've only built around 300 to 400 boxes for people (an expert will be around 500 boxes or more). But I can tell you this. In a car we tune higher because we want more relative gain. NOT because we want it to hit higher. We want to try to force those lower fequencies to be produced.

Notice in my graphs that the yellow line is starting to decrease around 80 and 90 Hz, this is NORMAL for most cars. Now, I set car interior size to intermediate. So any wave longer than 150-inches was to long for the car. So the sound starts to roll off. So I want to increase relative gain, so I change the tuning from 32 to 38 Hz. It flattened the response.

Again, notice the F3 point (The -3dB point). In both cases its around 30 to 35 hz. So anything below F3 we ignore, its not important. So can we hear the difference between the 30 to 35 Hz roll off (F3). No, our hearing is not that good.

Many of the people I built boxes for always wanted to be the "loudest, lowest" hitters in town. For those people I built large boxes tune to 45 to 50 Hz. These boxes had NO problem playing any music the owner put in ther CD players. (except in ALL cases the CD player skipped when they really cranked up the volume)

A few examples




In both these examples the boxes are tuned around 45 to 50 Hz. I built these around 2002 and I never heard a complaint that it could not play the rap music they listened to.

This Honda Civic SI box is tuned around 55 Hz. This customer played rap, rock and country. Never one complaint. He could play any music he wanted to.



So why tune so high. The wall made the car interior much smaller, I needed a Ridiculous amount of gain. And it worked.

Opps, I'm 51 years old and its past my bed time

 

First false belief we have to fix, tuning lower DOES NOT mean it can play lower.

There is more gain because we create it by manipulating box size and tuning, in most cases gain improves LOWER frequencies

Lets look carefully at my graph
Both Boxes are 1.75 cu ft
Red Line..............Box tuned to 38Hz------------------------ Green Line.....0dB Flat Response
Yellow Line..........Box Tuned to 32Hz------------------------ Purple Line.....-3dB Point (F3)

First, notice that, regarless of tuning, both boxes cross the 0dB line at 40 Hz. Whether I tune the box to 20Hz or 50Hz this will happen. (If there is a difference it WILL NOT be more than + or - 2dB)Why? Because box size did not change. If I increase the box size it will cross 0dB at a Lower Point. If I make the box smaller we will have the reverse effect. In most cases Box size has more effect on how low it will play then tuning.




Now lets look at the yellow line. This line represents the 32Hz tuning. It looks like it peaks between 80 and 100Hz. Its a smooth graph so it would sound good in a car.

But now I tune Higher, from 32 to 38Hz. Look what happens. At the frequencies that matter its louder (more relative gain) The higher tuned box is louder at 50Hz, at 60Hz, at 70Hz and at 80Hz. Its louder at all the frequencies that matter.

Now the F3 point, anything below this point can be ignored. We cannot hear anything below this point so forget it. The F3 point for the yellow line looks to be around 32Hz and for the red line it looks to be around 35Hz. First there is only a 3Hz difference so who cares. If there was a 10Hz difference then I would look at it, but seriously, the sound is rolling off fast at this point.

Lets keep our attention where it matters. The frequencies above the 0dB line. Now both boxes would sound good in a car, the higher tuned box would play better and slightly louder at lower frequencies.

I wanna remind everyone who reads this, WE are talking about a CAR, NOT A LIVING ROOM

 

I want to add something. All this info is correct, but remember all woofers do not perform the same. But the differences in performance will will be minimal.

Lets look at the 8-inch woofer problem. First, Tuning has little effect on how low a woofer plays so we are gonna ignore port tuning. So how can the 8-inch play lower than the 10? If we put both the 8 and the 10 in a 1.75 cu ft box, the 8 is in a box larger than it would need. The software we are using just applies mathematics with out common sense.

In reallity the 10-inch woofer will be louder and lower than the 8-inch woofer regardless of box size and tuning. This will be true in any case.

zps2004, I will look ay your posted specs later

 

Only a few instruments actually reach the 30 and 40Hz range such as the pipe organ, contrabassoon and string bass. And this is at their lowest possible range. And mainstream bands do not use these instruments. Also we have trouble hearing anything below 30-35 Hz. So you are wrong.

I stand by what I've said, there is no music below 30 to 35hz. If you would please let me know what song I can find that has music that is lower. I do have the ability to look at the frequency range of a song.

 

zps.....Ranger is correct.

The lowest octaves in most music do not go below 40Hz. Period end of story....As I read through these posts I find that Ranger is guiding you in the right direction. I too was in the car audio industry for many years. And enclosure engineering was one of my specialties. For most any system that utilizes a vented design, in the mobile enviorment, A tuning of around 40Hz give or take was very typical. Sometimes even higher. The "transfer function" of the cabin will produce an effective gain typically in the range of 10-15 dBs. And besides, having the box do its job in the effective range of musical content will provide a much better experience.

 

I believe your choice of woofers is a good one. Why? Going from a 1.75 to a 1.5 has little effect on woofer performance. In fact in my earlier graph, where both boxes was 1.75, we saw little difference between tuning at 32 and at 38. In fact most people would not be able to hear the difference.

Anyway here is the 10-inch woofer, a 1.5cu ft box tuned at 35 Hz. Red Line

Behind it, is the same woofer, 1.75cu ft box same tuning (yellow line almost invisible)



The slight variation in size does not effect this woofer at all.

One thing I would like to bring up, if you are concerned about getting the lowest possible frequencies please consider a 12-inch or larger woofer. If you insist on staying with a 10 then consider a downfire box. Downfiring or firing the woofer into an object (2 or 3-inches away) loads the woofer and really improves low frequency response.

http://www.caraudiotalk.com/audio-forum/showthread.php?t=9678&page=2

I've really enjoyed this thread, PLEASE keep the questions and observations coming.

 

Wow, I've learned to much from this thread. I think it's definitely time to take another look at my own enclosure. I won't hijack this thread, though.