3 Way crossover details...

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Loren42

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Joined 2008
Lambo240z said:
Too bad I am not in Miami anymore, I could have given you the Speaker :(
Anyway here is a comparison of both in 1 drawing.
So the area between 30 and 60 Hz is the big deal, I see, it gets to be up to 4 dB higher and that is pretty noticeable right?
Ok I will try to see another possibility, and bug you 1 more time to model it. If it doesn't show that I can go smaller without compromising the quality at low frequencies, then I will have to start designing something with the 150 Liter one.
Thanks Loren.
Leo

An externally hosted image should be here but it was not working when we last tested it.
Click to expand...


Box size is the only parameter that will give you the bass. 150 liters seems to be the sweet spot and more than that gives diminished returns.
 
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Loren42

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Joined 2008
mitchyz250f said:
50 cm is about 20 inches. A 15 inch woofer is about 16 inches diameter, and the Audax' is about 8 inches diameter. So; 16/2 + 8/2 = 12 inches Center to Center IF the outside of the speakers are touching.

Which means the mid and woofer can only be about a 8 inches apart.
Click to expand...

Theoretically, no more than 8" edge-to-edge for the crossover frequency used in Lambo240z's design.

If you change the crossover frequency, the center-to-center limit changes, too.

I'll guess that the recessed mid is to align the acoustic center of the mid with the woofer for time alignment.

More important is the time alignment between the mid and tweeter.
 
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Lambo240z

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Joined 2010
Ok some more questions, how important is that dip and peak around the 500Hz? Can it be smoothed or controled maybe with an equalizer? Also it is pretty much where the crossover starts working so will it be noticeable?
Also that dip, is it better if it shows at a lower frequency or a higher one?
Also are there any important differences between having a square vent against a round one?
Thanks.
Leo
 
L

Loren42

Member
Joined 2008
Lambo240z said:
Ok some more questions, how important is that dip and peak around the 500Hz? Can it be smoothed or controled maybe with an equalizer? Also it is pretty much where the crossover starts working so will it be noticeable?
Also that dip, is it better if it shows at a lower frequency or a higher one?
Also are there any important differences between having a square vent against a round one?
Thanks.
Leo
Click to expand...

That did looks like an internal resonance to me and has more to do with the box size and shape. You can throw fiberglass filling at the problem or reshape the box. It's too early to get too worried about the glitch until we settle box size and shape.

If the dip was present it would ripple into the final frequency response to one degree or another, but it is too early to get worried about that.

As far as port shape goes, rectangular are usually preferred for subs because you want to get as much cross sectional area as possible to counter port compression and chuffing. Subs have very large Xmax and consequently move a lot of air when the bass gets deep.

In your case the Peavey does not move a lot of air, so a large vent is less of a necessity. The high tuning of 40 Hz will not move large volumes of air, so you can get away with a smaller cross sectional area without having port compression.

For a given SPL level the amount of air displacement goes up as the frequency goes down. That is why a little tiny tweeter can produce ear shattering volume and a woofer's cone is seen to displace a lot of distance when making the same volume.

The disadvantage of a rectangular port is making adjustments. They are hard to make longer and hard to trim to length for fine tuning.

Round ports are easy to tune because you can buy ABS port ducts of all sizes and even buy flares, which help reduce port compression on their own.

For your design I would recommend 4" ID round ABS ports. They are cheap and easy to change the length and easy to employ in any box.
 
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Lambo240z

Member
Joined 2010
Ok cool Lauren, thanks. That gives me an option regarding the shape of the vent.
I have a couple more possibilities with boxes of 120 liters. Thats the smallest I was able to do them without having that big difference in the lower frequency.
If you are kind enough and whenever you have time, please run them in LEAP to see if they look ok.
First: 120 liters ( 830mm by 512mm by 317mm) with Vent: Round 200mm diameter and 270mm long
Second: 120 liters ( 808mm by 500mm by 309mm) with Vent: Rectangle 150mm by 150mm by 140mm deep.
Also I was reading something that said that if you use the vent with both ends flush sometimes it reduces slightly the Fb ?
In that case if it is true, then you can try them without the depth dimension.
Thanks.
Leo
 
L

Loren42

Member
Joined 2008
Lambo240z said:
Ok cool Lauren, thanks. That gives me an option regarding the shape of the vent.
I have a couple more possibilities with boxes of 120 liters. Thats the smallest I was able to do them without having that big difference in the lower frequency.
If you are kind enough and whenever you have time, please run them in LEAP to see if they look ok.
First: 120 liters ( 830mm by 512mm by 317mm) with Vent: Round 200mm diameter and 270mm long
Second: 120 liters ( 808mm by 500mm by 309mm) with Vent: Rectangle 150mm by 150mm by 140mm deep.
Also I was reading something that said that if you use the vent with both ends flush sometimes it reduces slightly the Fb ?
In that case if it is true, then you can try them without the depth dimension.
Thanks.
Leo
Click to expand...

Actually, two 4" vents was what I meant to say. The ABS comes in standard sizes and the actual ID is 3.95". I would recommend two ports like that.

I'll run a sim later and post the results. I was also going to take the Audax free-air driver response tonight. However, it is Friday, there is fine imported beer in the refrigerator, and our enclosed pool is a balmy 94°, so you have a few strikes against you. :D
 
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Loren42

Member
Joined 2008
Audax PR170M0 Data

Here is the data I collected using Woofer Tester 2. Sorry about being late with doing this.

The files are in three formats, ASCII, LMS, and FRD.

I did four runs to determine if the measurements are stable. I think they are.

I did not measure VAS due to time, but I figured that was not as important as the impedance and phase data.

All were measured with the driver affixed to a wooden stand without a baffle (open air) 4 feet off the floor in the center of a room.

An externally hosted image should be here but it was not working when we last tested it.


If you can't download these, private email me and leave me your email address so I can send these as attachments.

http://www.mdbq.net/audax/audax_001.log

http://www.mdbq.net/audax/audax_001t.log

http://www.mdbq.net/audax/audax_001.frd

http://www.mdbq.net/audax/audax_002.log

http://www.mdbq.net/audax/audax_002t.log

http://www.mdbq.net/audax/audax_002.frd

http://www.mdbq.net/audax/audax_003.log

http://www.mdbq.net/audax/audax_003t.log

http://www.mdbq.net/audax/audax_003.frd

http://www.mdbq.net/audax/audax_004.log

http://www.mdbq.net/audax/audax_004t.log

http://www.mdbq.net/audax/audax_004.frd

I have a friend in Orlando that has a music store that I might see if he has a Peavey 1502-8 that I can test in the same manner. That may take awhile to get done, but I will keep you informed.
 
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