| masterp2 |
I have looked at various subs for a downfiring, small sealed actively EQ'd, stereo sub application for HT. I have considered Audiomobile Mass 12, Earthquake Magma 12 and other high excursion/low vas/power handling subs.
For the price ($119), the Audiobahn Alum12X (www.audiobahninc.com) seems to have an impressive offering, optimized for small volume: cast basket, rubber surround, aluminum cone, 16mm one-way, 3" DVC, 120oz magnet, 1000W RMS, and excellent T/S params for small sealed HT modeling.
Fs 20
Qts .4
Vas 90
Please help me.
What do these other USA subs have that China's Audiobahn doesn't? Do they justify spending 200% more. I'll be using 1 to 1.4 cubes for each sub with high power. My objective is SPL/SQ compromise. 60% theater, 40% music.
Does anyone know if 16mm is linear or excursion limit?
Michael |
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| Nonlethal |
| Well, for one thing I don't think any of the others mentioned have the excursion that the Earthquake does. |
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| masterp2 |
| You may be right, though the Mass is about the same, actually has more linear xmax I think. (And the wallet prompted the question) |
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| Nonlethal |
| If you feel comfortable shelling out the cash, go for the Earthquakes. They are very impressive. I have used them for car audio in the past and am in the process of making an enclosure for a magma 15 out of a Piece of steel pipe with the correct inside diameter... its very heavy... |
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| planet10 |
| quote: | Originally posted by masterp2
I have looked at various subs for a downfiring, small sealed actively EQ'd, stereo sub application for HT. I have considered Audiomobile Mass 12, Earthquake Magma 12 and other high excursion/low vas/power handling subs.
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Michael,
All these that you mention are auto-sound drivers. Ususally lots of flash, exaggerated claims, and not great value for the money.
You should have a look at the large number of medium 12" designed for the home sub market. I have Adire Shiva and find it very good. I'd like to sell these and replace them with Stryke SAE1204s (John uses %$^^ frames so if you want to get to his home page you have to delete everything after .com/ in the URL). If you can afford the extra tariff the Lambda woofers he has (and won't have more of at anywhere near the current price) cannot be beat -- these are hand-built by Nick McKinney and use all the motor tricks of the skanning/ScanSpeak/DynaAudio drivers. Their specs might not seem as stellar as other woofers but the quality...
dave |
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| masterp2 |
Thanks Dave for your suggestions. I see it this way. And correct me if I'm innaccurate.
Those subs won't reach serious spl's for HT at the 20HZ range in a small sealed enclosure. I'll blow'em. This application requires large (linear) swept volumes and higher power capability to EQ that response, yes?
This is why I seem to feel that some high end car subs may be the best candidate for a 1 c.f. HT subwoofer. The car sub has been optimized for this very application, i.e. high linear excursion, high power handling, tiny Vas. True, most of them have an early rolloff for optimum car gain use, so I am just picking from the ones with lowest Fs and reasonable Qts, and positive reviews for home use. Perhaps one with an F10 of 20 HZ, which the audiomobile, Magma and Audiobahn have. Equalization then takes over to flatten the curve, given enough excursion and power handling.
So please poke some holes in my plans. I don't want to make a big mistake. But I need to know why these subs would not do the best job, and not why someone else's favorite drivers (in another application) is recommended. I realize that small, sealed is not the usual route in the HT, but please bear with me, it is a concession I am trying to optimize.
Michael |
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| planet10 |
| quote: | Originally posted by masterp2
Those subs won't reach serious spl's for HT at the 20HZ range in a small sealed enclosure. I'll blow'em. This application requires large (linear) swept volumes and higher power capability to EQ that response, yes? |
Forget the specs. The Shiva or the Stryke (or the Lambda) will outperform the car woofers -- particularily in a home application. The Shiva is VERY popular for cars.
I have a big *** car woof down in the lab -- real pretty but you pay for pretty by sacrificing performance.
The common small box app is to put them in a cu ft and add a Linkwitz Transform EQ to them -- you did say you were going to EQ them.
And remember if you want your woofer flat to 20 Hz it has to start its modeled roll-off a lot sooner. Otherwise with room gain you will have way to much bass.
I currently have a single Shiva in a 1.7 cu ft box with 40 W (NAD watts) on each coil and it produces bass that can be feltand not heard -- i am working on a bigger box with two woofers in push-push so that i don't have to work them as hard.
dave |
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| masterp2 |
"I currently have a single Shiva in a 1.7 cu ft box with 40 W (NAD watts) on each coil and it produces bass that can be felt and not heard "
A sealed 1.7 box with, I presume 12 HZ, SPL at 40 W?? Please clear up my confusion. What is the SPL at 20HZ? EQ'd? |
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| ThingyNess |
I agree with planet10 - most of the autosound subwoofers are all glitz and no performance, with huge retail markups to boot.
The exception of the ones you mentioned is the Audiomobile MASS2012 - it still has a high price tag, but it has excellent performance as well, and is far superior to a Shiva. The Audiomobile MASS series is made by TC sounds - the same people who make the fearsome HE-15 sold by Stryke.
It should also be noted that the performance of the Audiobahn and the Earthquake have not been independently measured by a 3rd party such as DUMAX - for their "xmax' measurements, they are free to quote anything from one-way linear magnetic throw, to 2-way damage-limited suspension throw. Be wary of their numbers.
The Shiva and MASS2012 have both been DUMAX verified - they are both very honestly spec'd, and will do you quite well.
I personally wouldn't go anywhere near the Magma 12 for the price, I'd MUCH rather have the MASS 2012.
It should be noted that another incredibly well-performing contender has been left off the list - the one that I personally would buy if I had to do what you're doing.
The missing driver is Blueprint's BPD1203. At $219, it represents an incredible value, and is practically designed for your application.
It has gobs of linear xmag (over 25mm, DUMAX verified), and more xsus (suspension excursion) than *any* of the above mentioned contenders. The shiva weighs in at about 20mm, ditto with the audiomobile, but the Blueprint 1203 is in a class of its own at well over 30mm one-way!
Its near-identical cousin, the 1503 (which uses an identical motor) was DUMAX tested at 25.86mm xmag, and 36.18mm xsus. The 1203 will have an identical xmag due to the same motor design, but likely a little less xsus due to the limitations of the 12" basket as far as spider diameter and depth goes. I'd estimate it to have at least 30mm one-way though. The 1503 will happily handle 1000W or more (Blueprint has hammered their '03 motor with 2000W+ doing sine sweeps and other tests, and had them come out unscathed)
Basically, if you want ultimate EQ/transformed output out of a tiny box, but with massive power requirements, pick the 1203. If you want less output, less cost, and less power requirements, go for a Shiva or any of its cousins (Stryke SAE1204, Parts express 12" DVC, etc.)
- ThingyNess |
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| masterp2 |
Thanks for your help. Yes I did leave it off the list. When I modeled it, it rolled off so badly that it seemed to require too much EQ on the low end, more than I have anyway. And the power needed, I'm not sure I have that either.
I'm using a 12 band parametric (12dB limit) and NAD208. Keep in mind that I plan to drive a stereo pair. From the predicted curve, 15 dB is called for, that's got to be something like 2000+ W for full excursion and 105 dB. Even if I had the power, do I really want that kind of heat in a stuffed cubic ft? Am I on the right track?
Michael |
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| masterp2 |
| Where is the Dumax report on the 1503? |
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| masterp2 |
What I found is similar to the 1203. It really need the LT. At 20HZ (Q=.7) you need about 15-16 db of EQ and 4000W dynamic to utilize full Xmax (110dB at 20). Agree?
Anybody out there ever start a fire like this?
Conclusion, I'll never bottom out! More excursion than can be utilized (for practical purposes) without an LT. Sure it's nice to know it's there. But is there a downside to having an excursion you can't utilize? Just a thought.
I think I'd prefer something without as dramatic a rolloff. With half the power, I can still get 105 dB with the audiomobile, fully utilizing the linear (with another 10mm non-linear room to spare) excursion. Maybe someone would controvert my conclusion with practical application with the Blueprint?
Michael |
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| ThingyNess |
http://www.audiomobileinc.com/image...mass2012s24.gif
I don't know where you get your numbers, but the audiomobile doesn't have any suspension throw left at all when it exceeds xmax.
As a matter of fact, it's the suspension that limits the excursion on the MASS 2012, rather than the motor.
Note that the BPD 1503 has near DOUBLE the xsus of the audiomobile woofer, not to mention that if you look at the BL vs. X graph, the motor is still running smooth (albeit with less BL) way out past 35mm, with no steep drop-offs as you exceed xmag like underhung motors tend to exhibit.
- Rick
PS:
Note that if you get 5dB less output with half the power with the audiomobile, then the Blueprint would in theory be the better choice anyway - you only get 3dB for each doubling of power to the driver at the best of times, assuming no thermal compression at all. If what you said is correct, then at the same power, the BPD1203 would have a 2dB advantage over the Audiomobile. |
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| masterp2 |
How do you plan to EQ the blueprint? LT? Are you ok running that kind of power in a small box? I know it's done all the time. It might be overkill for me, using stereo subs.
What do you know about the SQ features of the Blueprint? |
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| masterp2 |
"Note that if you get 5dB less output with half the power with the audiomobile, then the Blueprint would in theory be the better choice anyway"
I didn't think about what I was saying. What I mean is, with my hardware, amps, eq's etc, 105 is all I'm gonna get, even if I have a driver capable of 110. It would be underpowered in my house. |
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| ThingyNess |
Even if you only have the amplifier power right now to hit 105, that doesn't necessarily mean you won't be able to get more later.
Also, it's good to get as much power handling as you possibly can in a driver, because thermal compression is a very real issue, and the further you stay away from the driver's max power rating, the better you'll be. Due to the BPD '03 motor's huge VC and huge top plate, it has more heatsinking capability than almost any other motor out there. The audiomobile on the other hand has a large top plate, but a relatively tiny voice coil - makes it much more difficult for it to dissipate the heat effectively.
As for the blueprint, a linkwitz transform would work well, as would a parametric or 1/3 octave eq - they're just different means to a very similar end.
Also, all other things being equal, it's always good to have xmax and xsus in reserve. The farther you stay away from (the dumax defined) xmax and xsus, the less distortion the driver will produce.
As for the BPD '03 sound quality, I haven't had a chance to own one myself (I had one on order, but had to cancel due to financial difficulties), but all accounts say that it sounds exceedingly good. To be fair to the Audiomobile MASS2012, all reports I've heard say the same about it as well.
In the end, subwoofer sound quality, more than anything else in the audio world, comes down to the alignment, enclosure used, and specs of the driver. We're not asking for huge amounts of bandwidth out of a subwoofer driver, nor are we operating them anywhere near their primary cone breakup mode, (assuming a 12/24dB/octave x/o near 80hz) so assuring a very large linear operating envelope is your best bet to achieving high sound quality. |
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| ucla88 |
i agree with dave and rick
in general, shy away from any autosound drivers that don't have dumax specs
the blueprint is a very good choice in a small sealed enclosure
this thread is worth reading from start to finish, though it's long. |
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| masterp2 |
Sounds like I have to make a decision. Thanks all.
P.S. Thingyness, the mass dumax report was an old one, there is a more recent one on their site. The Xsus does not indicate max suspension limits, rather it indicates where resistance to movement is 4X the neutral position. I found this out when phoning them. In their more recent report, even this number has expanded. It goes to a physical limit of 30. Regardless, it may be a mute point.
Good information, thank you. |
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| ThingyNess |
You are correct in that it does not represent the max suspension limits, but it should be used to represent the maximum usable suspension limits.
Keep in mind that Fs is inversely proportional to the square root of Cms - so that if your Cms quadruples (as is the case when you hit the DUMAX suspension limits), then at that finite point in time, your Fs is now double what it normally was. For the audiomobile, this would be around 44hz. That'll throw your alignment off pretty good, I'd think.
Also note that as the suspension stiffens, you'll get even less output with a given input power - as you approach even 200% of the suspension limit, it will start to compress the peaks in the material, and you lose dynamic range. As you hit 400%, this phenomenon gets even worse. This is why I like the Blueprint for your application, as even if you only plan to use 20mm of excursion, the Blueprint's Cms/Kms Vs. X curve is near ruler flat in that region. |
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| subwo1 |
Yes, ucla88, I find this thread very enjoyable. I like the thoughts Thingness expressed very much.
Has anyone noticed that the optimal woofer for a small sealed enclosure has a QTS of .40? Or do all ones with QTS of .40 or less generally do well? |
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| masterp2 |
Stuff I didn't know. More enlightened. Thanks. I may give in to this 1203. It is a good price per pound.
If only this were as easy as buying hamburger. |
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| masterp2 |
I think everyone agrees that a driver like the 1203 has an early rolloff. Other drivers with higher EBP values tend to not do this, hence the recommendation for large EBP in small sealed apps.
The question is, if I am using multiband parametric Equalization (like the BFD), which is prefered? a shallow early rolloff, like .5 Q, or a .707 optimally configured type?
The EQ is goin to have to attempt to approximate an LT. I may try to develop a spreadsheet that does this. Is there any interest (or maybe it's already been done). That will at least provide a starting point for tuning a room, given the model or even actual sweep measurements. I've never tuned (EQ'd) a room before with para EQ, bandwidth adjustments, etc. |
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| ThingyNess |
The 1203 does indeed have a relatively early rolloff in a sealed enclosure, due to its low Qts.
Having said that, the low Qts also buys you more efficiency, all other things being relatively equal, so the amount of EQ required may not be as bad as it sounds. If the driver had a Qts of 0.4/0.5 for a shallower rolloff, it would likely be down in the 84/85dB/W/M range. It may require less EQ, but as a whole, would likely give very similar amounts of acoustic output once EQ'd flat.
I personally prefer very shallow, relatively early rolloffs, because the room gain transfer curve of most rooms will serve to make this very close to flat in the average sized room - with no electronic EQ at all!
If you make your subwoofer flat down to 16hz anechoic, then in the average room, you're going to have a greatly exaggerated sub-bass region, as the room gain curve gives a heavy boost to the very low frequencies - many people fail to take this into account when designing a sub.
If you do indeed decide to go the parametric EQ route, the best route is likely to acquire a decent SPL meter or some other measurement device, set it up in your listening position, and calibrate your EQ for optimum flatness at your listening position.
When seeing the anechoic F3 of a Qtc < 0.5 alignment, many people are immediately scared off when they see 60 or 70hz - they think that there's no way that alignment could possibly produce any bass. Put it in a room though, and you'll likely see the in-room F6 be well down in the sub-bass range, and that's sans EQ.
- Rick |
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| masterp2 |
With my intention of stereo subs from one amp, my NAD can deliver 250 per side into 8 Ohms. Dynamic into a 4 Ohm load is 800W, and 1000W into 2Ohm.
Using a 1203 in a 40 L box, what kind of SPL can be expected at 20 HZ (per speaker, no corner loading)? My room is 15x30x8 with 2 hallways.
To estimate power requirements, I use linkwits spreadsheet. According to this, my amp will get 12mm excursion (RMS power) and 18-20 mm on the Dynamic end.
Do you agree with this?
Looking at the 1503 specs, it may be more efficient, yes? |
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| ThingyNess |
Download Unibox, and you can figure it out yourself (the SPL @ 20hz, that is)
http://www.danbbs.dk/~ko/ubdwnld.htm
The excursion calculations sound approximately correct.
However, you are indeed correct that the 1503 is more efficient, and the 1803 is even more so.
If you have the little extra money, and a little extra room for a slightly larger enclosure, ignore the 1203 and get the 1503 (or ideally) the 1803 - the extra efficiency really helps, as does the extra volume displacement.
Personally, unless I had to cross the woofer over relatively high (above 100hz), or unless I needed a *really* tiny enclosure, I'd never buy anything but the 1803 - it's so much better at minimal extra cost. :)
- Rick |
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| subwo1 |
I agree with Rick about not worrying about a low QTS. The problem I have seen is that woofers whose value is over .40 tend to muddy the output or boom. I think it is important for a small enclosure to select a driver with high excursion and power ratings along with a low QTS, and use a parametric EQ to compensate. I recommend using a sine wave generator to adjust the equalization by ear. These can be downloaded as freeware or easily built by a DIYer.
For my subwoofer, I modified an automobile EQ/amp to be able to boost/cut frequencies of 30,45,60,75,90,105,125 Hz. I chose values to complement the unequalized response of my subwoofer.
I also recommend using a lot of polyfill insulation in the enclosure, but be certain to give the woofers some breathing room.
I should also mention that I have added a low pass filter to the output of this EQ/amp. Then I run that output into a few hundred watt amplifier to drive the subwoofer. |
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| dice45 |
| quote: | Originally posted by subwo1
Has anyone noticed that the optimal woofer for a small sealed enclosure has a QTS of .40? Or do all ones with QTS of .40 or less generally do well? |
scanned through old-fashioned Bullock tables to proof this statement from a buddy who is speaker designer. He claimed that at a Q_ts of 0.4, the recommended enclosure volume reaches V_as as a minimum.
So if a driver has low V_as and Q_ts of 0.4, V_as is equal to enclosure volume, else (below AND above 0.40 ) the enclosure is bigger than V_as.
Have a small 2way vented speaker to prove this (can be used as closed speaker, too; parameters fit): true, measured 60Hz from a 4 litres enclosure. |
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| masterp2 |
The HE-15 was mentioned earlier. Is it a candidate for this application, keeping under 1.5 cf? Any reviews on this driver?
Sound Quality? |
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| ThingyNess |
The Stryke HE-15 driver sounds excellent and is almost bulletproof, but virtually needs either a 3000W amp, or a cabinet with many expensive passive radiators to really show what it can do.
For the price, I'd still much sooner have the BPD1803 - the Vd of the 1803 will be as much or more than the stryke, and the extra 3dB of efficiency really does help matters.
Also, consider that for the price of an HE-15 and PRs, you could get two 1803's - which would give you 3dB MORE efficiency, and a huge Vd advantage.
- Rick |
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| masterp2 |
I'v got to keep my volume under 2 cubes in each cabinet. I downloaded unibox as suggested. The 1503 (and 1803) would require more power (on paper) than the HE. And needs more volume. HE at 1.5-2 ohm load, 1503 at 4 ohm. The HE makes much better use of my NAD, even if it is slightly less efficient.
An 18 is out of the question for me, too large for the downfiring stereo cabinet footprint I have in my head. I think 15's are going to be more than enough anyway, remembering that I am integrating them with recycled paradigm mains, 6.5" plus tweet.
Thak you for hanging in there with me. |
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| masterp2 |
| The paradigm Minimonitors are capable of respectable 50HZ performance, but it is still only a .39 cf ported box. For a subwoofer compliment, how much swept volume should be considered "too much" to complement them for HT and music. |
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| ThingyNess |
First off, I should ask which NAD receiver you have, and how much power it will give to your subwoofers. I would ignore the "dynamic" power ratings that NAD publishes, as the power supplies in them are far too small for this kind of a load, and the power rails will collapse a ton under heavy load. While the dynamic power may be useful at higher frequencies, the low frequencies you plan to run through these require the amp to sustain its "dynamic" power output for a much longer period of time (as the length of each cycle of the waveform is MUCH longer), and the amp will likely end up putting out its full dynamic power for the first part of the cycle, and as its filter capacitors and power supply collapse, it will likely put out much less throughout the last part of the cycle - not the terribly best thing from a sound quality point of view.
Not to mention that the 1.5 ohm load presented by paralleling two coils of the HE-15 may be too much even for the NAD, and you'll may find the protection circuits activating more often than not. If this ends up being the case, you'll have to run them in series, giving you 6 ohms, which will end up being much worse from a power utilization point of view than the BPD drivers were.
Seriously though, I think you're underestimating the amount of power required to do the linkwitz transform justice. The suggested cabinet for an HE-15 is a 6 cubic foot passive radiator enclosure, which is way, way WAY more efficient than a tiny sealed box in the low end. Still, even with a ton of extra efficiency gained by this, many people were unsatisfied with 300, 500, 800, and even 1000W RMS! (Note that most of these figures were produced by amps that could actually put out that amount of power continuously - it wasn't "peak" or dynamic power.) Many people ended up buying something along the lines of a crown K2, which put out 2000W bridged into the HE-15. Even with THAT, the HE15 still wouldn't reach its limits.
(for reference, here's the K2 datasheet)
http://www.crownaudio.com/pdf/amps/131429.pdf
I'm not trying to dissuade you here, just trying to make you aware of the enormous *continuous* power requirements that are required for the linkwitz transform to be of any use at high volume levels.
I have a feeling that if you power these off a NAD receiver or integrated amp, it'll sound fine with any material over 40hz or so, but unless you have the volume nice and low, you'll push the amp so far into clipping as soon as you make use of the linkwitz transform (down around 20-30hz or so), that you'll be hearing more distortion products than actual undistorted output.
As for your question re: the paradigms - you might want to consider sealing the vents - with a 50hz vented rolloff, the sealed rolloff will likely start around 80hz, which is right around where most subwoofers are crossed. There's no point in having the vent active below your passband, as it just adds pipe resonances and other garbage that aren't needed. This will also provide a useful reduction in intermodulation distortion as the woofer cone won't have to move as much with any given input.
Also, there is NO such thing as too much swept volume - ever. The more you have, the less you need to use, and the more you have in reserve. The less you need to use, the lower the distortion's going to be. =)
- Rick |
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| masterp2 |
Thanks Thingyness.
Your post really summarizes what my concerns have been all along. I'd like to do the small sealed box, but using an alignment that minimzes the EQ needed for low 20 HZ extension. This has been my argument all along for trying to stay away from high EBP drivers, like the 1203.
The less EQ, the more realistic my amp is. I really don't want to get another amp. It is NAD208, very stable even at 1 ohm (from reading reviews). It may be underrated.
But paying attention to this now, may improve todays performance, even though I may get a bigger Amp down the road, especially after putting in mega hours into this project.
We're almost there. |
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| masterp2 |
According to NAD, the 208 puts out 300W Clipping into 8 Ohms.
Does anyone have a guess at what clipping power would be at 2 ohms? |
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| ThingyNess |
The clipping at 8 ohms is voltage clipping.
In theory, the nad could instantaneously put out 1200W into 2 ohms before voltage clipping, but internal current limiting, along with the collapse of the power supply rails will limit the output to far less than that in practice.
Luckily, your amp isn't as low-powered as I had feared - it may indeed provide decent performance with this setup.
Just know that in your quest for a very small enclosure, and ultra-extended bass, you have thrown efficiency to the wind and will require a ton of power - there's no way around it.
Also, ignore the amount of EQ needed - it's irrelevant. What's more important is the absolute power level required to put out a certain SPL at a certain frequency.
For example, let's assume the blueprint puts out 80dB at 20hz with 1 watt in your enclosure, and the stryke puts out 78dB at 20hz with 1 watt in your enclosure.
Now, let's assume the upper limit of its efficiency comes at 80hz, where the blueprint puts out 92dB with one watt, where the stryke puts out 89dB.
In theory, the stryke would then require 11dB of EQ versus 12dB for the blueprint. Does this matter? Not at all. No matter how much EQ you have to use, the blueprint will still put out more power at 20hz for each watt you throw at it than the stryke.
Imagine that we had a hypothetical driver that was horrifically efficient (say 120dB/W/M - which can't exist but is fine for our thought experiment), but started rolling off very early (say 200hz), and below 80hz followed the exact same rolloff as the numbers i've cooked up for the blueprint, settling to 80dB at one watt at 20hz.
With this theoretical driver, we now require 40db (!) of EQ, but this isn't a bad thing in the slightest. We still have the same efficiency on the low end, but we just need more EQ because our efficiency on the high end is so much better.
Drivers with high EBP's that you'd choose for this application tend to have a low Qts, since it's in the denominator for the EBP equation. A low Qts corresponds to a low Qes, becuase in almost all drivers (tweeters notwithstanding), Qes dominates the Qts since Qms is relatively high. Since Qes is low, and efficiency increases as Qes decreases, the efficiency of a driver with a high EBP tends to be high as well.
This will mean it tends to roll off sooner, but since it had a higher efficiency to start with, it may well indeed be more efficient down low as well, despite the earlier rolloff. This is what matters, *not* a simple dB amount of EQ that you have to apply.
If you like, you can think of EQ not as "boosting" the low end, but "cutting" the high end down to meet the low efficiency in the infrasonic region.
Pick the lowest frequency you expect your sub to produce, and pick that as your reference point, and pick a driver and enclosure such that you get the most output at this frequency with a given power level. Once you do this, you can think of your EQ as "cutting" the high end of the driver, and giving it *less* power as frequency increases. Looking at it this way, if you have two drivers and the low end efficiency is the same, then a greater amount of EQ is in fact *better*, since you now can "cut" the higher frequencies more, and have to output less power to the driver to produce them.
With our hypothetical driver that requires 40dB of EQ, this means that we need 40dB less power if we want the driver to produce 200hz! This means that if you're running the amp at a nominal 200W at 20hz, then the driver is getting in the milliwatt range at 200hz - certainly makes things much easier on the amp and driver, no?
- Rick |
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| subwo1 |
| Rick, you are definitely onto it. Keep up the good work! |
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| masterp2 |
Rick,
Right before I read that post, I was doing what you said. I have decided to just look at the 20 HZ SPL with 300W in my 2 cube box. Both are about 100 dB. The HE-15 just 1/2 dB better. The 1203 also comes in about the same, the biggest diff is that it is closer to the excursion limit, which makes sense.
In all the drivers alignments run from .5 to .6 for the specified volume.
Now in theory, doubling to 600W will present 3 dB gain. Yup, plug it in and sure enough.
Your argument is proven, explanation, excellent! Thanks for taking the time.
Now maybe another NAD will come my way.
Michael |
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| masterp2 |
Now the question remains for the 1503: What sealed volume will yield optimal SPL results down low from a modest power supply. The idea for me is small as practical, size is important but so is sound. I don't think distortion is going to become a consideration at these (relatively low) power levels, correct? What is a good volume tradeoff? I came up with 2 cubic ft stuffed, Qtc=.55
Michael |
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| ThingyNess |
Optimal volume?
Since you're using EQ and a sealed enclosure, the optimal volume is easy.
For *any* of these drivers, be it 1203, 1503, 1803, or HE-15, you want the largest enclosure possible. Can you spare 30 cubic feet? Great - use it. If not, make the box as large as you possibly can. The larger the enclosure is, the more efficient the subwoofer system will be in the sub-bass region.
As a matter of fact, in the sub-bass region, the size of the enclosure is far MORE important from an efficiency point of view than the subwoofer driver itself.
Moral of the story? Make it as big as humanly possible.
- Rick |
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| masterp2 |
Well, If I had room, we wouldn't have had this whole conversation, now would we?
So I guess I'll put the 1503 in 30 L sealed.
Michael |
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| Just kidding. see my point? |
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I have all but decided on the driver I'll use thanks to the help of many. Thomas W and Rick, thanks a lot.
BUT......I found this (15") driver, modeled it for an active EQ'd sealed box HT app and liked it for the extra SPL it presented, with linear excursions to match what has been considered up to now.
http://www.audiomobileinc.com/evo-rspecs.htm
A little bigger box, .65 Q, 78 liters and 106dB at 20. And a 2 ohm load that mates well with my amp. Is .65Qtc too high for this app?
It's new and yet unproven, but a very good TC Sounds product. Not trying to talk myself into it or out of it. I'll take suggestions/opinions.
Michael |
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