Interesting - Could I ask what material you used and how did it improve the sound?
fatmarley,
The cone is a composite material that I developed. Doesn't exist anywhere else and is very different than any other composite cone on the market. The actually gained some bottom end as they did have a bit more mass and lowered the fs value and just were smoother than the original paper cone. I sill have a case of those speakers, some are modified and some still in the original condition. They are in my storage which I hope to get to soon.
The cone is a composite material that I developed. Doesn't exist anywhere else and is very different than any other composite cone on the market. The actually gained some bottom end as they did have a bit more mass and lowered the fs value and just were smoother than the original paper cone. I sill have a case of those speakers, some are modified and some still in the original condition. They are in my storage which I hope to get to soon.
No, I did not build yet. I will, by the end of June, in my intentions. Still looking for the nice wood. At least for the external parts I would like to use a 9 mm Baltic birch multilayer, or a marine one (the latter is heavier, though). Maybe 12 mm only for the baffle. I will heavily brace everything . A complete skeleton, even with 1" stuff is less than 2 Kg. In the worst case, if power not enough, I can biamp, getting some 3 db more, or even get a 24V battery, going closer to 6dB, but getting probably too close to the drivers limit. I´m better with electronics, than with boxes, I feel. Lower octaves, forget them. Too difficult outdoors, without a real , heavy sub.
What about my question on the ports? Large or deep?
Good. The reason I asked was I would suggest adding an extra Aura in parallel to get +6dB with the same amount of power - they are pretty cheap. Actually, I'd like to tell you to scrap that mid and tweeter all together and just add a good cheap tweeter that will cross lower to the Auras (this would maximize your use of box volume) but since you've already purchased them, I won't. But I really, really want to tell you to do that.
So you'll need to double your box volume to add the extra NS6 and since weight and size are important factors to you, I suppose that won't work if you want to stay vented. But you can do it if you go sealed. And going sealed solves the most important problem with your design - the Aura very quickly runs out of excursion at LF's with very little power when it's ported. See the first graph below. That's at 98.5dB with 10W in 14L (you need to account for the volume of bracing, port and driver etc) and Fb=45Hz. With musical content below 35Hz (not at all unlikely), the cone has far exceeded its excursion limits. If we raise the SPL's just a little to 101dB with 18W, xmax is now exceeded between about 65-90Hz where all kinds of musical content lies (2nd graph). Serious problem for trying to fill any semi-large public spaces I think.
But if you go sealed with 2 Auras in somewhere between 15L and 20L, and use 10W for 104dB, cone excursion stays within limits - 3rd graph. Fourth graph is the FR with this alignment. F3 is 74Hz. Not great but not too bad either.
Notice that right now your total box volume plans are 15L + 9L = 24L, whereas by just using 2 Auras and a tweeter sealed, you can do it all in 20L. See now what I was getting at above?
Now if you can high pass the vented version at about 50Hz, then it's a slightly different story but you're still SPL limited with just the 1 driver.
Attachments
jReave,
Your analysis is right on and I second the opinion and have been trying to say the same thing about using a nice dome tweeter rather than a midrange which is not necessary with the Aura and I question if those two other devices are going to sound nearly as good as the Aura speaker would without the mid range crossover and a bullet tweeter that I have always found very objectionable. Double Aura's would be a much nicer implementation and they are fairly inexpensive. I think I only paid about $6.00 per unit when I bought them by the case. The other limitation of the Aura besides the excursion limit is the very small voicecoil and fine wire used. I have burned up a few playing with them but I didn't really care, I just threw those away and put in another. If with two he could accomplish a low frequency output down to 60hz that always gives the semblance of low bass and is a trick used by many commercial bookshelf speaker to sound like they have true bass tone.
Your analysis is right on and I second the opinion and have been trying to say the same thing about using a nice dome tweeter rather than a midrange which is not necessary with the Aura and I question if those two other devices are going to sound nearly as good as the Aura speaker would without the mid range crossover and a bullet tweeter that I have always found very objectionable. Double Aura's would be a much nicer implementation and they are fairly inexpensive. I think I only paid about $6.00 per unit when I bought them by the case. The other limitation of the Aura besides the excursion limit is the very small voicecoil and fine wire used. I have burned up a few playing with them but I didn't really care, I just threw those away and put in another. If with two he could accomplish a low frequency output down to 60hz that always gives the semblance of low bass and is a trick used by many commercial bookshelf speaker to sound like they have true bass tone.
Thanks for the confirmation. I knew I was repeating what someone had already said but I couldn't remember who.
I was also thinking of suggesting some LF boost down around 60Hz but it was peaking instead around 150Hz in an smaller sealed box. I can get a nice 2-3dB peak centered around 68Hz or so but that's back to a vented design and in an even bigger box of about 30L per driver. Not suitable in this application unfortunately.
Thanks again for the very informative post.
I understand that I have made many mistakes, but I do not see a solution now.
So vented not feasible at all if I am tearing the woofer with only 18 W.
I will not get any other Aura. It looks is a crap woofer for what you are telling me, and at a transport cost of 60 $ I can spend better my money next time.
Lesson learned.
Any good priced neodidium 8" available in EU?
That said, before scrapping the whole project and buy a ready made chinese boombox, I would try to understand if sealed is a possible solution. Why everybody in PA is convinced that vented boxes push more on bass?
Then I do not see why if the sealed box would work with 2 x crap Auras it won´t work with the Aura + Celestion 5" Neo . That driver is only a couple of dB spl under the Aura and goes well up to 9K- I can make a removable baffle, so that would be my only risk at this point-I can scrap the bullets if they are really so bad, or cut them badly with a couple of Kohms and 2-5 uF.
I understand that I have made many mistakes, but I do not see a solution now.
So vented not feasible at all if I am tearing the woofer with only 18 W.
I will not get any other Aura. It looks is a crap woofer for what you are telling me, and at a transport cost of 60 $ I can spend better my money next time.
Lesson learned.
Any good priced neodidium 8" available in EU?
That said, before scrapping the whole project and buy a ready made chinese boombox, I would try to understand if sealed is a possible solution. Why everybody in PA is convinced that vented boxes push more on bass?
Then I do not see why if the sealed box would work with 2 x crap Auras it won´t work with the Aura + Celestion 5" Neo . That driver is only a couple of dB spl under the Aura and goes well up to 9K- I can make a removable baffle, so that would be my only risk at this point-I can scrap the bullets if they are really so bad, or cut them badly with a couple of Kohms and 2-5 uF.
Sorry AT, I don't think I explained myself well enough. Xmax is the excursion limit before the voice coil starts to go above and below the magnet so that's the point where sound quality starts to suffer. Usually the mechanical limit of cone excursion is larger but Aura hasn't given that spec so I don't know exactly what it is. When it's reached, it'll still probably take a whole boatload of power to tear the cone. Maybe the voice coil would fry first - I don't know, but either way it'll start sounding bad before that.
Here's the thing - I'm not saying it's a crap driver, but every driver has its limitations so you have to use it in the right application. It's actually quite a good driver if you use it for its midrange and not down too low and not at excessive SPL for a single driver. And the value ratio is also very good over here where it's selling for about $10, but for you at $60, well, not so much unfortunately. I wasn't aware that that was your cost.
A vented box will get you more bass but it means that the cone is going to have to be moving in and out a lot more and the driver needs to be designed for that. Xmax on the Aura is 4mm but 10 or 15mm would be much better in this application. Certain drivers are better for sealed boxes and others are better vented. The functionality of a driver is going to depend on how you want to use it.
Sorry, I was hoping you'd be able to understand from my last post. It will work with the Celestion but the 1 Aura still won't play as loud as you might need it down in the low frequencies. When you start to use multiples of the same driver, then each driver has to work less, so therefore, they can play louder. Since the Aura will play easily up to 3000Hz or a little above, and because space is at a premium for you, that makes the Celestion a bit of a redundancy. I was trying to show you that if you used just 20L (less than what you were planning before), and used 2 Auras sealed from 20Hz up to 3000Hz and then just added a regular tweeter for 3000Hz and up, that that would work better for you. It would be better still if you used 4 Auras and just a tweeter in about 40L.
But really, it's not such a good suggestion now that I know how much you have to pay for those Auras.
So, what to do?
Actually since you have everything there already, I would make up some cardboard test boxes, put the drivers in them, crank it up and decide whether or not everything I've just been telling you is true or not. Decide with your own ears whether or not it sounds good enough for you. Go ahead and try it sealed and vented and with 1 Aura and with 2. Proceed after that based on the outcome.
ATAUDIO,
The limitation on the Aura is the surround, that is what will limit that drivers maximum excursion. You will run out of physical motion before the voicecoil could possibly leave the gap, that it will never do, the magnetic gap is very long for that little driver. When it runs out of excursion you will know it as it will make very horrible noise for sure. All that being aside you can get them fairly load and I have used them in a ported box, just don't try and tune them below the resonant frequency they will not appreciate it. I think that the 16 watt limitation may be lower than reality, they will take a bit of power but just to be safe you do have to remember that it is really a small driver. If I had mine in hand I would just mail you another pair, but the customs and mailing anything to Austria is probably stupidly expensive. I sent my niece a package to Amsterdam and it cost me more to send it than what inside was worth! Don't dispare just yet. I would sell the mids and the bullets if you could and buy a pair of dome tweeters if at all possible if it was me.
The limitation on the Aura is the surround, that is what will limit that drivers maximum excursion. You will run out of physical motion before the voicecoil could possibly leave the gap, that it will never do, the magnetic gap is very long for that little driver. When it runs out of excursion you will know it as it will make very horrible noise for sure. All that being aside you can get them fairly load and I have used them in a ported box, just don't try and tune them below the resonant frequency they will not appreciate it. I think that the 16 watt limitation may be lower than reality, they will take a bit of power but just to be safe you do have to remember that it is really a small driver. If I had mine in hand I would just mail you another pair, but the customs and mailing anything to Austria is probably stupidly expensive. I sent my niece a package to Amsterdam and it cost me more to send it than what inside was worth! Don't dispare just yet. I would sell the mids and the bullets if you could and buy a pair of dome tweeters if at all possible if it was me.
Since you already have the drivers go ahead and build the boxes.
The fact that they will be used outdoors means that it will not matter that much if there is a slight peak in the frequency response.
A vented box will definitely give you more SPL in the bass.
You can build it and try different length ports to see what suits you best. You can't do that with a fixed slot so I do not recommend a slot port.
In a 20lt box you can try different 5cm round tubes with lengths from 11cm long (44Hz) down to 2cm (71Hz).
You can model different tube diameters in WinISD very easily.
IMHO the Celestion midrange driver is not needed and it will most likely not improve anything but if you have to use it put it in a very small sealed compartment (just enough to fit in) and cross it at 500-800Hz. You will also need an Lpad to adjust the sensitivity of the piezo to match the midrange.
An other option would be to get a suitable tweeter to match with the aura woofers and make a second pair with just the Celestion mids and the piezos in a very small enclosure powered by a second tAmp and use them as assistance or as monitors so they don't get wasted.
The fact that they will be used outdoors means that it will not matter that much if there is a slight peak in the frequency response.
A vented box will definitely give you more SPL in the bass.
You can build it and try different length ports to see what suits you best. You can't do that with a fixed slot so I do not recommend a slot port.
In a 20lt box you can try different 5cm round tubes with lengths from 11cm long (44Hz) down to 2cm (71Hz).
You can model different tube diameters in WinISD very easily.
IMHO the Celestion midrange driver is not needed and it will most likely not improve anything but if you have to use it put it in a very small sealed compartment (just enough to fit in) and cross it at 500-800Hz. You will also need an Lpad to adjust the sensitivity of the piezo to match the midrange.
An other option would be to get a suitable tweeter to match with the aura woofers and make a second pair with just the Celestion mids and the piezos in a very small enclosure powered by a second tAmp and use them as assistance or as monitors so they don't get wasted.
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Some updates:
I have given up with the creepy Aura/Celestion combi, as many here suggested.
Too much effort in building and not the SPL that I wanted.
I am now experimenting with a couple of Moancor 8" , 4 Ohm (SP202E).
They have no complete T/S specs, but they come cheap, have a good SPL and more than all are lightweight.
As tweeter I am keeping the previus Pyle piezo stuff, at least for the moment.
Ist order crossover or not at all.
The woofers will get about 20L of ported box each. Port Tuning will be done by listening, but I will stat with about 2" x 3", 3" deep . Any suggestion, again, very welcomed
I have given up with the creepy Aura/Celestion combi, as many here suggested.
Too much effort in building and not the SPL that I wanted.
I am now experimenting with a couple of Moancor 8" , 4 Ohm (SP202E).
They have no complete T/S specs, but they come cheap, have a good SPL and more than all are lightweight.
As tweeter I am keeping the previus Pyle piezo stuff, at least for the moment.
Ist order crossover or not at all.
The woofers will get about 20L of ported box each. Port Tuning will be done by listening, but I will stat with about 2" x 3", 3" deep . Any suggestion, again, very welcomed
Thanks for the suggestion. I opted for the Monacors sp202E for price&availability and also lighter weight.
Now they are arrived, and I am (re)designing the box. Things get simpler with a single 4 Ohm woofer. I can reach to some 30 or 33 l that would suffice if it would be a SP202 C.
Unfortunately I could not found T&S parameters for the SP202 E. However it looks almost the same and maybe the last letter is only and update commercial designation.
Anybody has experience with this drivers in a small ported box?
Now they are arrived, and I am (re)designing the box. Things get simpler with a single 4 Ohm woofer. I can reach to some 30 or 33 l that would suffice if it would be a SP202 C.
Unfortunately I could not found T&S parameters for the SP202 E. However it looks almost the same and maybe the last letter is only and update commercial designation.
Anybody has experience with this drivers in a small ported box?
I'm putting together a 2-way with this Aura, and it is very heavy on the low end, needs a wide long port to curb that, the bigger box the better. I'm using a 2.5" diameter pipe. If you can cross it at 500 Hz, that's great. Its midrange is not very good, loss of detail and a severe lacking in output between 1.5k Hz and 4.5k Hz. 4.5k Hz is a loud peak that only brings misery. I'll post the crossover and a youtube recording when I'm done putting the box together.
Some test on the go...
About 2 x 20 liters, rectangular ports made out from the bottom of the electronics/battery bay.
Light construction ("marine" okume' plywood 8 mm, with 20x20 mm skeleton).
All structural joins are glued and have screws, except for the baffle that has only (big) screws, making it removable. First baffle will go with the Aura then we will see.
About 2 x 20 liters, rectangular ports made out from the bottom of the electronics/battery bay.
Light construction ("marine" okume' plywood 8 mm, with 20x20 mm skeleton).
All structural joins are glued and have screws, except for the baffle that has only (big) screws, making it removable. First baffle will go with the Aura then we will see.
Attachments
Almost done! only a grid is missing.
At the end, looks like the best way to cross it over was with only the dampening resistor in series with the piezo (24 ohm used). I tried with more complicate ways (paralleling a low ohm and then a first order HP + LPAD) but the highs were always "muffled".
Now, SPL, plenty of it. At max volume the box hardly can't handle it and anyway the xmax limit of the Aura is reached a little bit earlier.
But until then the sound is full and robust, without appreciable distortion.
Much bass that I can feel "in my stomach" and crystal highs.
I do not know yet if I am going to try to make anoter baffle with the 8" Monacors...
At the end, looks like the best way to cross it over was with only the dampening resistor in series with the piezo (24 ohm used). I tried with more complicate ways (paralleling a low ohm and then a first order HP + LPAD) but the highs were always "muffled".
Now, SPL, plenty of it. At max volume the box hardly can't handle it and anyway the xmax limit of the Aura is reached a little bit earlier.
But until then the sound is full and robust, without appreciable distortion.
Much bass that I can feel "in my stomach" and crystal highs.
I do not know yet if I am going to try to make anoter baffle with the 8" Monacors...
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