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Post by mojave on Jan 4, 2011 9:34:00 GMT -7
I have four Eminence 15" subwoofer drivers that I just realized might work for an IB system in my home. I could purchase 4 more of the drivers for $79 each. I have an easily accessible crawlspace and could install two manifolds with four drivers each. I have never modeled anything before, but I tried to model these in WinISD. These have a modeled IB QTC of .336 which results in a shallow rolloff from 100 Hz and down. With 8 drivers and 1800 watts (225W/driver) it is still showing as having 122.5 dB of output at 20 Hz. However, when I look at the cone excursion it is over 13 mm at about 30 Hz with a huge increase below that. I have to lower the power to 200 watts (25 W/driver) to keep the cone excursion below 13mm at 10 Hz. Am I looking at this right?
My room is 2400 cubic feet, but opens to a kitchen and dining room (pocket doors can be closed to dining room, but are usually open)
Here are the driver parameters:
Re 3.04 Ohms fs 15.04 Hz Le 2.07 mH Mms 235.2 grams QM 6.62 Mmd 221.6 grams QE 0.34 Cms 0.476 mm/N QT 0.32 Rms 3.356 N*sec/m Xmax 13.02 mm Vas 458.9 liters Pmax 225 Watts SD 823.7 cm^2 Bl 14.08 Tm VD 1072.3 cm^3 Coil Diameter 2.50 Inches EBP 44.1 Gap Height 0.375 Inches Magnet Weight 112 ounces Efficiency 0.44% Winding Width 1.400 inches SPL 88.5 dB 1W-1m
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Post by chrisbee on Jan 4, 2011 14:37:50 GMT -7
You are looking at 2 litres of displacement per driver. You are ignoring room gain with your modelling software. 16 litres of displacement should protect you from over-excursion despite rather limited Xmax. You could add a high pass filter to protect the drivers from extreme excursions. At least until you gain experience and confidence in their VLF handling capacity. I would be hesitant about trying to watch action films with only four drivers. No doubt Thomas can find reasons not to go ahead with these drivers.
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Post by ThomasW on Jan 5, 2011 7:02:56 GMT -7
Will they work? Yes.
Are they the best driver for the job? No, they're designed for a ported box where their lowish excursion isn't a problem.
And yes your sims are correct, you'll start running out of excursion quickly at low frequencies.
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Post by mojave on Jan 5, 2011 10:35:08 GMT -7
Thanks for the replies. Yes, Thomas, the driver was designed for a ported subwoofer. It is custom from Eminence for AV123's MFW-15 subwoofer. I decided to model four drivers: Dayton Audio IB 15, Eminence MFW-15, Acoustic Elegance IB 15, and FI 18S2. For the Dayton and Eminence, I added a high pass filter at 6 Hz to reduce excursion. Because of the low QTC for the Eminence driver, I also added a Parametric EQ with a gain of 7 dB and Q=.5 at 10 Hz. Adding these filters would be no problem for me since I can go down to 1 Hz using GlissEQ on my HTPC. I then gave each set of drivers (eight 15" drivers and four 18" drivers) as much power as I could without going over their X-Max. Here are the results: Fi 18S2: 110.5 dB @ 10 Hz, 120.5 dB @ 20 Hz AE IB 15: 109.3 dB @ 10 Hz, 117 dB @ 20 Hz Dayton IB 15: 107 dB @ 10 Hz, 117 dB @ 20 Hz Eminence MFW-15: 106 dB @ 10 Hz, 114 dB @ 20 Hz Attachments:
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Post by mojave on Jan 5, 2011 10:36:07 GMT -7
Here is the SPL comparison: Attachments:
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Post by ThomasW on Jan 5, 2011 12:58:07 GMT -7
I would advise not to use 7dB of 10Hz boost with the Eminence drivers. Doing so is just asking for trouble...
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Post by mojave on Jan 5, 2011 15:06:23 GMT -7
Okay, I modeled it again without the boost and added more power to reach maximum excursion. I am building out a pair of GR Research LS-6 line source speakers for my mains. I should be able to crossover to the IB fairly low if needed. Both the AE IB15 and the MFW-15 eight driver system look like they have similar slopes from 20 Hz down. With room gain, they should be very similar down to about 10 Hz with the AE IB15's having a few more decibels of output. It looks like the increased efficiency (88.64 vs 85.67) of the MFW-15 helps make up for its lower X-Max. The real difference amongst the drivers seems to be from 10 Hz and below. The AE and the Fi can both play louder lower than 10 Hz because they don't need a highpass filter to prevent over excursion of the driver. With shipping, it would be about $356 for me to go with eight MFW-15 drivers (since I already own four). To use the AE IB15 drivers would cost about $1100. I think the Fi drivers would be a little cheaper. However, I do already own an Acoustic Elegance AV15X and really like it. Besides picking the drivers, I guess the next step would be talking my wife into letting me cut holes in the floor of our living room.
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Post by chrisbee on Jan 5, 2011 15:34:00 GMT -7
I don't know whether anybody else agrees but I have never sensed anything below 10Hz from any of my IBs. The cones are moving and I can see the figures on the Galaxy SPL meter but there is no physical sensation at all on 9HZ sinewaves and below.
AE has been having problems obtaining 15" surrounds. Whether AEIB15s are currently available I have no idea. There are relevant threads on the AE forums. Some customers have allegedly waited a year after paying up front for 15" drivers. This may affect your driver choices.
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Post by mojave on Jan 5, 2011 16:06:54 GMT -7
I've been waiting for over a year for more AV15 drivers to become available, but I never ordered/prepayed for one. The problem with the rubber surrounds only affected the AV series drivers. According to this post on Jan 3, there is about a 4 week lead time on IB15 drivers. If I go IB, I will no longer want or need another AV15 driver. Anyway, at the speed I go it will probably take me a year just to build the manifolds. ;D
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Post by mojave on Jan 6, 2011 8:14:49 GMT -7
I e-mailed Fi Car Audio yesterday for a quote on some IB drivers. Nick said they are starting a new company, Blueprint Drivers, that will be HT focused.
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Post by chrisbee on Jan 6, 2011 8:57:13 GMT -7
I e-mailed Fi Car Audio yesterday for a quote on some IB drivers. Nick said they are starting a new company, Blueprint Drivers, that will be HT focused. There's irony there in that performance engines are "blueprinted". So the car audio drivers should be called Blueprint. Not the other way around. Mind you, they can't call the HT stuff car audio either.
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Post by ThomasW on Jan 7, 2011 6:26:07 GMT -7
There's irony there in that performance engines are "blueprinted". So the car audio drivers should be called Blueprint. Not the other way around. Mind you, they can't call the HT stuff car audio either. Actually some of the first drivers marketed by people involved with Fi were named Blueprint. I built several subs using Blueprint 15"s. These were some of the first reasonably priced, high excursion drivers available to DIYers. Tubezilla was a rather compact tube sub with a BP 1503 at each end....
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Post by chrisbee on Jan 7, 2011 7:18:19 GMT -7
Thomas, I hope you've tidied your room by now? More seriously: I think what should come out of a thread like this is cautious optimism in relation to alternative drivers. Provided that displacement exceeds (say) a nominal 10 litres then other drivers will work in an IB. I think it would be a mistake to exclude all others than Fi or AE. These Eminence drivers have more potential than some others due to their low Fs. Limited Xmax can be overcome buy using many more of them to limit damaging excursions.
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Post by ThomasW on Jan 8, 2011 9:35:34 GMT -7
Thomas, I hope you've tidied your room by now? It's always cleaned up between projects. ....... ;D
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Post by mojave on Jan 11, 2011 10:32:50 GMT -7
I tried to get permission from my wife to go ahead with this. She listed off about 8 projects that I have to finish before I bring this one up again. I guess I'll have to get busy. Back to the drivers . . . I almost talked myself into using the AE drivers due to the low Qtc of the Eminence drivers. I then modeled using a Linkwitz Transform to extend the knee and was able to match the slope of the AE drivers, but with a little less output. The attached chart shows the output both with and without the L-T. If I can simulate an LT electronically, should I be able to match the modeled slope? I don't want to purchase a Marchand Bassis or similar because then I might as well spend the money on the AE drivers. The low Fs of the Eminence drivers allows the L-T to increase cone excursion in the 6-30 Hz area without ever exceeding the excursion of the driver without an L-T. The low Fs also allows this driver to then match the Qtc of the AE IB15 - a Qtc which should go well with room gain.
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Post by mojave on Jan 11, 2011 13:49:17 GMT -7
The MiniDSP is a relatively cheap way to add a Linkwitz Transform. On their forum they have a spreadsheet that allows you to design the L-R for the MiniDSP. The neat thing is that the spreadsheet shows it graphically as well as the SPL increases needed at each frequency. This allows me to model the L-R using the GlissIQ plugin that I use.
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Post by mojave on Jan 27, 2011 13:49:09 GMT -7
I just received four more of the Eminence drivers. I got them for about $268 shipped since they had some slight cosmetic damage to the gasket on the very outside of the driver. Eight of these will total 17.12 liters of displacement. With an L-T circuit with an F(p) of 22 Hz, these model identical in slope and output to the Dayton IB385-8, which I think are also made by Eminence. The drivers I bought are 4 ohm and have a 2 1/2" voice coil. I should be able to get an in-room QTC of around .7. Once I get my wife's approval I'll start a project thread (it might take a while ). Actually, I might start the project thread sooner.
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Post by mojave on Mar 7, 2011 19:34:33 GMT -7
I know its not IB, but there is a build thread at AVS for 4 dual opposed sealed subs using these drivers. Nice extension to 10 Hz!
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Post by FOH on Mar 8, 2011 6:39:36 GMT -7
I know its not IB, but there is a build thread at AVS for 4 dual opposed sealed subs using these drivers. Nice extension to 10 Hz! Extension to 10hz? With a broad 10db boost @ 20hz., as per the build thread. It'd probably be a good driver in large quantities, something like the Octagon. It's a very low tech, minimally built driver according to it's designer....Mark Seaton. He recommends a minimum of 4, and ideally more like 8 or 16 of them, in a small sealed alignment.
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Post by mojave on Mar 8, 2011 9:02:19 GMT -7
Extension to 10hz? With a broad 10db boost @ 20hz., as per the build thread. It'd probably be a good driver in large quantities, something like the Octagon. It's a very low tech, minimally built driver according to it's designer....Mark Seaton. He recommends a minimum of 4, and ideally more like 8 or 16 of them, in a small sealed alignment. If you read through the thread you will see that he forgot to load his EMC8000 calibration file for his first EQing. Actually the boost is only 3 dB. Post 30: I have also attached a correct REW graph. I am only using 3db of boost on the low end to get these measurements. After John at Acoustic Elegance said he might not have anymore IB15's for a while I contacted him. I purchased the last drivers and should have 8 IB15's delivered in a few weeks. Someone local wants to buy at least 4 of the MFW-15 drivers and I might use the other 4 for a sealed sub.
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