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Argh!!! Choosing Drivers


Deadeye
(@deadeye)
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I've known for a while exactly how my DIY speakers will look - in every way.  I know what I want them to sound like and I know the first song I'll play when I demo them to my friends. I'm eve 10% of the way to having the first clue how to build a crossover.  I know I want 3-way.

How in god's name do you go about choosing the drivers!!!???

Pretty sure the tweeter will be the Morel Excel - in my opinion, the tweeter is the most important to get right.

the rest? pff, I must have built 30 frd files and still none the wiser.

 

I know 8" is the biggest I can go and from my car subwoofer box building days (25 years ago) I prefer a couple of smaller drivers than 1 big one for more "punch".

 

Passive Radiator? Port? Sealed?

 

These will probably be crosseded over at 80Hz anyway so why agonise so much!?

 

How do you choose your drivers?


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TVOR-Ceasar
(@tvor-ceasar)
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This is a highly personalized part of the hobby. Some want to only look at the highest of the high end, some are open to the mid priced stuff, some look to find a real bargain or diamond in the rough, and others are looking to see if they can at least make costume jewelry out of canine feces.

There are a couple of ways to go, but really, you should start with assessing the equipment you will be hooking the speakers to (amp power/ohm capability), the room size (LxW) or nearfield / desktop use, and overall general acceptable size of the speaker for it's intended placement, so you can get a rough idea of internal volume you have to work with. 

Obviously, the amp's power needs to be considered when choosing a driver. Too low of a driver power rating and you run the risk of frying the voice coil. So keep that in mind, and especially for the lower frequency drivers.

The bigger the room, the more SPL you'll need to fill it, so higher sensitivity or higher power handling. Nearfield and desktop don't generally need as much power or sensitivity.

Overall maximum size will be important when doing rough calcs to see if a bass or midbass driver will be able to be used in that box. Try to stay a bit flexible here.

Now that you have a few key parameters, you can go to a site like Parts Express and dial them in to narrow the search. Remember to give yourself a range to look for, otherwise you might miss that one driver that would possibly be "the one."

For me, I end up with several QBasic windows open and my old programs running to help narrow down the choices. The absolute minimum you need for both sealed and ported is Fo/Fs, Qts, and Vas. Transmission Line uses Driver Diameter (equivalent if not a round driver) and Fo/Fs. I can run a calc in less than 10 seconds to see if it's worth considering. Then I can download the full info and files for something like WinISD to run a better analysis.

For crossover info, you'll need to look at the resonant frequency of the driver that will be the next in line (up frequency), double it, and see if the driver below it will work with it.

So say you have a woofer that goes from 30-2000Hz, a mid-range that goes from 800-6000Hz, and a tweeter that goes from 2400-22000Hz.

As you can see, 800x2=1600Hz. This "fits" within the 2000Hz limit, but you may want to consider a mid-range that goes a little lower to better fit the overlap. Now the tweeter at 2400x2=4800Hz, so you are fairly good there, but may still consider a tweeter with a slightly lower Fs. Ultimately, you'd need to chase down the graphs, FRD and ZMA files to put in a XOver software, just to make sure, but this will give you a starting point.

Don't forget to keep an eye on the SPL ratings. They are easiest to compare when they are of the same impedance and designation, like 1W/1M or 2.83V/1M. If you have questions about this, please ask. I've gone over it a few times, but I don't mind doing so again. Mixing differing impedances makes it harder to easily match levels and tends to make the XOver design more complicated, though it can be done. 

The more you do it, the better you'll become. And maybe, just maybe, you'll find that jewell you never knew you were looking for.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Deadeye
(@deadeye)
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Thans for this, it's so tricky choosing.

 

I really like the Seas Excel stuff but it's expensive and I don't know yet if what I build will be any good.

I am tempted to just use the drivers Nick used in the uglies.  I'm 80/20 films and a 2-way is easier than 3-way.  Maybe

 

Thing is, I'm supposed to be building speakers that are better than my PMCs.  The PMCs are amazing.

 

I've got an Arcam recevier with Dirac Live for room correction and I'll have enough power to drive whatever I build.  I have a JL Audio E112 sub with 1500watt built-in amp so that can keep up with anything and break your house. I might even build new ones to match my mains.

 

I need to choose quickly as I've had my templates waterjetted in 6mm aluminium (I'm building the cabinets from sandwiches of 18mm MDF) so I need to know volumes to pick which sandwiches to make.

 

I didn't really want to port the cabinet so I would be putting the Tangbands W8s in a sealed box which according to the part-express website would tun to 75Hz which is great as I'd probably still cross them at 80Hz for movies.


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123Toid
(@123toid)
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Posted by: @deadeye

How in god's name do you go about choosing the drivers!!!???

 

I know 8" is the biggest I can go and from my car subwoofer box building days (25 years ago) I prefer a couple of smaller drivers than 1 big one for more "punch".

 

Passive Radiator? Port? Sealed?

 

These will probably be crossed over at 80Hz anyway so why agonize so much!?

 

How do you choose your drivers?

This is a really good question.  There is no real wrong way to do this, but I will give you my advice.  And the basics of what I do.

 

First, I would start with the woofer or mid (assuming two or three way).  Make sure that whatever alignment you choose it will be able to go to the frequency you want it to.  So if you want it sealed and crossed over at 80hz, you will want to find a driver that can do that. 

Once you have this narrowed down, not it's size.  Ever driver will start beaming by a certain point. That means that the driver will start to deviate from it's on axis response. this is completely dependent on the driver size chosen. For example if we take a look at an 8 inch woofer were going to see that it starts to deviate from its own axis around one kilohertz. And it starts getting a lot worse around 3 KH. that means that if we take this driver and crossover during this area, are off axis response will suffer. So you typically want to crossover closer to the one kilohertz with a 8 inch driver. That doesn't mean you can't go later, just means that you're off axis myself for a little.  Another thing you wanna look at when you're looking at the driver is it cone break up. you're gonna notice that with some pretty sharp peaks in the response. this should be well after your usable frequency range. you wanna make sure to get that down as far as you can come and see don't get distortion in your final build.

Once you have the woofer or mid picked out you want to move onto your tweeter. you'll notice I didn't start with the tweeter, because I didn't know where I would want to crossover yet. If I have the idea of doing a 2 way with an 8 inch driver, I'm gonna need a tweeter that can crossover relatively low. so I probably don't wanna crossover any later than 1500 Hertz if I can help it. for this wanna take a look at 2 things. I wanna check the sensitivity of the tweeter and I want to check out it's FS. Typically a good rule of thumb to follow is not to crossover any higher than 2 times the FS of the tweeter. so you'd be looking for a tweeter with an FS around 750 Hertz or lower. You would also want to look free tweeter that is more sensitive then the woofer or mid that you've chosen. let's do the fact that you wanna be able to attenuate it to match the mid. You do not want attenuate the mid in a 2 way build.

What I have mentioned are basic rules of thumb.  But it should help as you learn.

https://www.youtube.com/123toid


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Deadeye
(@deadeye)
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@123toid

The W8s in the uglies are the first 8 inch drivers that go that low. Why wouldn’t they be good for music?

or would they ideally need a mid between them ate the tweeter?


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123Toid
(@123toid)
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@deadeye

They are good for music.  I listen to music with them all the time.  The reason I used the Peerless Corundum was in part due to the fact that I could cross it over low enough not to worry about the off axis response in the crossover region. 

https://www.youtube.com/123toid


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Deadeye
(@deadeye)
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@123toid

 

have you thought about what mid you might use if you would go 3-way?

I’ll start a build thread tomorrow

(I’m in England) 

I finally got PCD to work thanks to you videos and with those two drivers in the uglies have a good flat response but I can’t help think a good mid in between would finish things off nicely.

morel do a big soft dome mid like the mid in my PMCs. 


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Deadeye
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123Toid
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@deadeye

The Uglies don't' need a mid, so I have never looked or thought about it. But that is only due to the fact that both drivers can integrate well together and keep distortion down. You could add one if you wanted to.  I just haven't thought about it. 

https://www.youtube.com/123toid


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