Ile
New Member
Posts: 48
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Post by Ile on Dec 22, 2011 2:29:36 GMT -7
I'm in Europe and I'm looking for cheaper driver here in Europe for an IB install. Some cheap 15" "free air" car drivers is one option. JBL GT-5 -15 are around 100 euro JBL GTO1514 are around 130 euro 4 driver sets simulated with 6 m3 back space, both pushed to xmax excursion. I guess they gives only mechanical xmax in their spec sheet, so there would be pretty much distortion when pushed to this level.  |
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Post by exipnos on Dec 22, 2011 11:38:57 GMT -7
Again confused. Not because of you but because of other things I've found on the net. Since our driver comparison chart is not available at the above link I looked and found something else. forum.audiopsychosis.com/viewtopic.php?f=6&t=22Here he gives advice which driver is most cost effective (outdated maybe) and also explanation on how to calculate displacement. Also the whole xmax thing I find a bit confusing since different terminologies are being used and for a newbie it make is difficult. For instance what is point to point and what is one way. Look at this link for instance. www.stx.pl/product/attachment/99b5b71954ed6694014cbedd15658d25/pl_PL/SW-STX-15-4-1200-8-F-S-MC.pdf16mm xmax p.p for a 15" driver what does that give me? 1.368L 0.684L 2.736L Is this driver suitable in larger amounts per IB? |
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Post by ThomasW on Dec 22, 2011 12:16:09 GMT -7
Again confused. Not because of you but because of other things I've found on the net. Since our driver comparison chart is not available at the above link I looked and found something else. forum.audiopsychosis.com/viewtopic.php?f=6&t=22Here he gives advice which driver is most cost effective (outdated maybe) and also explanation on how to calculate displacement. The subject of that thread isn't drivers for IB subs. This is pretty elementary stuff Vd (volume displaced) is (Xmax times 2), (times Sd) (area of cone) Not a good driver for IB use due to accordion style surround. The topic of not using accordion surrounds discussed early on in the main FAQ page. The JBL car audio drivers Ile referenced are probably a best buy for those in Europe. |
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Post by exipnos on Dec 23, 2011 13:57:11 GMT -7
The subject of that thread isn't drivers for IB subs. This is pretty elementary stuff Vd (volume displaced) is (Xmax times 2), (times Sd) (area of cone) The JBL car audio drivers Ile referenced are probably a best buy for those in Europe. Thanks for clarifying and please bear with since I'm still learning about IB and how to read driver specs. In the above link, are the directions given on how to do the displacement calculations wrong, or do you need different displacement calculations if its for sealed, ported or IB design? In your calculation does the times 2 represent the in and out motion of the driver? Thus Xmax one way is used in your calculation? When it says point to point Xmax does that represent two way travel or one way travel? I'm now looking at other drivers since the stx ones are not suitable. Merry Christmas! |
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Post by chrisbee on Dec 23, 2011 15:19:07 GMT -7
Exactly! Xmax is one-way travel from the cone's rest position in or out to where the driver's performance is still linear.
Displacement is the swept volume of the cone from fully inwards to fully outwards. The safe total excursion may actually be greater than Xmax but should not be relied on for real programme material.
For convenience, displacement is calculated as twice the Xmax x Sd. Sd=the active area of the cone. Usually including half the width of the roll surround outer suspension.
As the cone radius is squared in our calculations, the area of the cone rises very rapidly with increasing driver diameter. As does the displacement of course. So a huge 18" IB driver with a large Xmax has a huge displacement.
Displacement measures the amount of air which can be physically moved by the driver cone. The lower the frequency and the higher the SPL demanded the more air must be moved. Large cones move a huge amount of air compared with smaller ones. Which is why the number of drivers required doubles with each step downwards in size.
IBs are displacement limited. The voice-coil will hit the end stops when the cones cannot move enough air to match the signal being fed to them by the amplifier.
There is no limiting air cushion to keep the cones from exceeding their safe excursion. So we use multiple, large drivers so the cones are never called on to make any risky excursions.
The lower limit is usually 2 x 18" or 4 x 15" provided the drivers are all long throw. i.e. Have a large Xmax. Preferably over 18mm.
Our problem is that driver prices do not go down as they get smaller. A pair of 18" IB318s offer the best value per litre of displacement. Since you need four 15" drivers they would have to be half the price of the 18" but usually they are not.
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Post by exipnos on Dec 23, 2011 20:25:51 GMT -7
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Post by ThomasW on Dec 24, 2011 7:34:34 GMT -7
If the published specs are accurate those drivers will work fine
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Post by exipnos on Dec 25, 2011 4:23:35 GMT -7
If the published specs are accurate those drivers will work fine I've been investigating a bit to see how accurate those specs are. I found some conflicting data in other sites. I eventually found the manufacturer site at www.audiodesign.de/produkte.htm They also have the thiele parameters at www.audiodesign.de/downloads/tsp/Crunch.pdf But I now realice that they are using the full travel for the xmax thus I should divide by 2 to get the equivalent comparison value. Thus the drivers could still work but not as good as I thought before. Edit by moderator to fix link. |
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Post by exipnos on Dec 25, 2011 22:36:45 GMT -7
I think I'm going with the Hifonics Atlas ASX 15. I'm thinking of getting 4 of these for a total of 22.5L of displacement.
Does the following values make make it suitable for IB?
Model ASX 15
D in mm 387
Xmax mm 70 (two way travel)
SD qcm 804
Mms g 223
Re Ohm 4
Fs (Hz) 27
Qms 4,5
Qes 0,42
Qts 0,39
VAS (L) 139
SPL (dB) 90
Le mH 1,5
VC mm 76
RMS (W) 850
Depth (mm) 189
Opening (mm) 352
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Post by exipnos on Dec 26, 2011 6:38:13 GMT -7
I installed bassbox and did some modeling but I'm not really sure if I am doing it right.
Following graphs are for 4 of the Hifonics ASX 15" subwoofers in an IB (20m3 box). First scenario is with 1200W power (one amp board of 300W for each woofer) and second one with 3400W power.
First scenario give me 116db at 20hz and 108db at 10hz with a cone excursion of 20mm at 10hz. Second scenario give me 120db at 20hz and 112db at 10hz with a cone excursion of 33.6mm at 10hz.
Does this look good? What does these figures really mean though. To little, enough, or to much? The extra amp power will cost a bit so is the difference of 4db going to be noticeable?
Attached Thumbnail
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Post by exipnos on Dec 26, 2011 12:27:45 GMT -7
Here are the attachments that did not go through before. Attachments:
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Post by exipnos on Dec 26, 2011 12:28:19 GMT -7
second one. Attachments:
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Post by ThomasW on Dec 26, 2011 17:51:09 GMT -7
Yes those will work but seem pretty $pendy from the prices shown.
I continue to think the JBL GTX are a good buy for those in Europe
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Post by exipnos on Dec 26, 2011 22:50:32 GMT -7
Cost per liter is the lowest of all drivers that I'm considering including the JBL. About 200E delivered per driver. With the JBL I would need minimum 5 drivers to get to 12L of displacement. Thus if I was using those I would have gone with 8 JBL. With the Hifonics ATX, 4 will cost me less then the 8 JBL and will give me more displacement.
Thomas - your advice is very appreciated. I'm about to make an order but want to be sure I'm doing the right thing. I've been told that these drivers might not gain anything from IB and that they will be happy with a small enclosure of 0.56m^3 and that they will have a qtc of .5 and that anything larger will overdamp the cones. Whats your take on it?
I'm assuming quality of sound will be better with the IB since it won't have the box coloration.
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Post by chrisbee on Dec 27, 2011 2:37:29 GMT -7
I have asked on the UK-based AVForums and people seem to be paying about £250GBP delivered for Fi IB318s from BladeICE.
Remember that you are getting 7 litres per driver. I can't imagine any (3.5 litre displacement) 15" driver being available at half that price in Europe. Which is the price they would have to be to match the price/displacement value of IB318s.
I have no idea where you are based so you would have to ask BladeICE for delivery prices to your own country.
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Post by exipnos on Dec 27, 2011 3:17:58 GMT -7
I'm in France and I could have 4 of those drivers for 800E delivered here. They are "supposedly" a quality driver with very good reviews on german car auto sites. If their specs are correct they will indeed be better value then the FI IB318s since these will cost me 300E and maybe more shipped to France.
I'm already stretching the budget by going up to 800E and thus could not consider the FI drivers.
The only thing holding me back right now is the supposedly low qts and a concern if they are suitable for IB. I will have only 300W per driver available.
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Post by moonfly on Dec 27, 2011 3:25:55 GMT -7
JBL also do a GTO15 driver available direct for £99 uk.jbl.com/jbl-product-detail-uk/gto1514-.htmlSlightly lower FS than the GTX from above and slightly cheaper. Still only about 2.5 litres displacement though to the Fi IB318's 7 meaning you would need 6 of these (£600) to match a pair of the Fi 18's (£500). There is then the hassle of trying to power 6 drivers vs only 2 which is much more straight forward, and if you need 2 amps for the 6 drivers cost will go up even more. I dont think going for cheaper drivers is always the way forward with IB's, as its usually offset by needing more of them. |
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Post by ThomasW on Dec 27, 2011 7:42:42 GMT -7
The only thing holding me back right now is the supposedly low qts and a concern if they are suitable for IB. I will have only 300W per driver available. The low Q means they'll require slightly more EQ, certainly not a deal breaker. As was pointed out earlier; IB subs don't require monster power amps since they use so many drivers, and since unlike other sub designs efficiently goes up as the frequencies being reproduced go lower. 300 watts/driver is plenty |
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Post by exipnos on Dec 28, 2011 11:50:25 GMT -7
Okay I completed the order. If the specs are correct then I don't think I will be disappointed. After all its 22L of displacement  The price delivered was 180E each. Its the lowest priced per liter that I could find here in Europe. Lower then the JBLs. I have high hopes on the quality since they had received good reviews. So it will probably take me a while before I have something ready to test but it will be interesting to see how well they work out. I'll start a project thread at a later time. Thanks for all your help. |
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Post by exipnos on Jan 2, 2012 6:29:29 GMT -7
I was feeling great about this purchase. I did my research and created a spreadsheet to see cost per liter including shipping. I found the specs and even though they said 70mm xmax I assumed it was for two way travel and I used 35mm in my calculations.
This woofer turned out to be the lowest priced and 4 would give me 22L of displacement. They received good reviews so I went ahead and purchased them.
Received the woofers! Now I'm angry!
The woofers are very heavy and they seem indeed to be of very high quality. The frame is very thick and everything was good. Then I saw that there was a small sheet with some thiele/small parameters. Well they where mostly inline with what was published on the site but the xmax was different.
They say xmax +- 35mm (peak to peak) and xmax +- 16.4mm (linear). If I understand correctly I'm to use the 16.4mm in the displacement calculations right? Well if thats the case they are then half as powerful as the published specs made me believe.
I have a call out with the seller who is checking with the manufacturer. Am I in the shits?
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