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Alpine DIY Subwoofer Build for HT


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#1 of 61 BraveHeart123

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Posted November 24 2012 - 09:06 PM

Hi DIY experts. I have Crown XLS-1000 amp that is 550 watts x 2 @ 2ohms. I am only listing 2 ohms rating coz that's the load i will be using on the sub. I have some very to-the-point questions before I make the purchase for diy project;
  • Can I power a single DVC sub from 2 separate channels i.e. each amp channel powering each voice coil separately?
  • Related to point 1, shall I go for Alpine SWR-1243D (4 ohm) OR Alpine SWR-1223D (2 Ohm)??
  • How to correctly model the sub if I power both the voice coils separately as the simulation software assumes we are using both voice coils wired either in series or parallel??? I am using WinISD Pro Alpha
I think Alpine SWR-1223D will serve my goals best as I am not wiring the voice coils in parallel or series; rather I want to power them independently from two different channels of the same power source. I think I can get the max out of Crown xls-1000 down to 2ohms this way. Also, although it is a stereo amp but the signal it receives is already converted in mono in the avr (80hz crossover) and I plan to feed same signal to both channels using a y-cord. I can level match both the voice coils with separate level attenuators for both channels. Am I correct in my assumptions?? I need your expert advice before I buy the sub.

#2 of 61 BraveHeart123

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Posted November 26 2012 - 06:12 AM

Almost 24 hrs and not a single response??? Guys need your help

#3 of 61 Dave Upton

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Posted November 26 2012 - 06:27 AM

I'm confused as to why you want to run each channel separately? You can bridge your channels on the Crown very easily (this will be referred to as Bridged Mono in the manual), then follow this wiring method:





#4 of 61 Robert_J

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Posted November 26 2012 - 07:05 AM

Almost 24 hrs and not a single response??? Guys need your help

It's a holiday weekend over here and I took off an extra day. I've been painting a room in the house instead of working/surfing. 1. Yes. You must make sure that the phase is correct on each channel. If you can set the attenuators so that each channel outputs identical power, that would be even better. Getting close by setting the attenuators the same is fine also. 2. Either one will work. You just don't want to over power the sub if you get the 2 ohm DVC model. 3. It really doesn't matter. The only parameter that changes is inductance. It is halfed in parallel and doubled in series as compared to each coil independently.

#5 of 61 BraveHeart123

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Posted November 26 2012 - 03:54 PM

I'm confused as to why you want to run each channel separately?

So I can run the sub at 2 ohms (SWR-1223D). That will be same as running a 4 ohm DVC in parallel. The reason is; I have Crown XLS-1000 that is rated at 550 watts x 2 in stereo mode. In bridged mode it is rated at 1100 watts at lowest 4 ohms. And all these ratings are at 1 KHz. This model of crown has been tested at 221 wpc in stereo mode at 8 ohms, which is a tad over the 1 khz published specifications. So, I am assuming that even at 2 ohms it would achieve the published specs even below 100 hz.

#6 of 61 BraveHeart123

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Posted November 26 2012 - 04:58 PM

2. Either one will work. You just don't want to over power the sub if you get the 2 ohm DVC model.

Alpine states the SWR-1223D to be 600 watts. I hope that is 300 watts each coil. My reason for not spending extra money on XLS-2000 or XLS-2500 is that I think I can get more power from XLS-1000 if I power the voice coils individually. Coz this amp can do 550 wpc at 2 ohms in stereo mode if I run both the channels without bridging. OK let's not be over optimistic and assume XLS-1000 does 330 wpc at 2ohms (60% power at full frequency spectrum) and I power each voice coil individually, I still get 660 watts collectively. Alternatively, I can wire the sub in series (4 ohms) and run crown in bridged mode i.e. 1100 watts at 4 ohms (1 khz), which still equates to 660 watts at 4 ohms (60% power at full frequency spectrum). So, the only difference is the choice between running the sub at 2 ohms or 4 ohms. Is there any sonic benefit I get by running it at 2 ohms compared to 4??? If not, shall I stick with wiring the sub in series and run it off crown in bridged mode?? It will save me from cutting two holes to accomodate two sets of binding posts. Another very important question, shall I go sealed or ported?? I eventually want to get rid of Klipsch SUB-12, and add another DIY after this. Can I still achieve depth in sealed box i.e. close to 20 hz?? Can I get away with not using SSF if I go with ported design i.e. I tune the port below the lowest LFE in most movies?

#7 of 61 Dave Upton

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Posted November 27 2012 - 01:15 AM

Originally Posted by BraveHeart123 


So I can run the sub at 2 ohms (SWR-1223D). That will be same as running a 4 ohm DVC in parallel. The reason is; I have Crown XLS-1000 that is rated at 550 watts x 2 in stereo mode. In bridged mode it is rated at 1100 watts at lowest 4 ohms. And all these ratings are at 1 KHz. This model of crown has been tested at 221 wpc in stereo mode at 8 ohms, which is a tad over the 1 khz published specifications. So, I am assuming that even at 2 ohms it would achieve the published specs even below 100 hz.

If you look at the diagram I posted, that is for a 2 Ohm sub with dual voice coils. Following that wiring, presents your amp with a 4 Ohm load giving you the maximum usable power from your amp. There's no need to make this more complex than it seems.


#8 of 61 BraveHeart123

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Posted November 27 2012 - 01:21 AM

Thanks but is there any worthwhile sonic benefit between running the sub at 2 ohms and 4 ohms?

#9 of 61 Robert_J

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Posted November 27 2012 - 02:42 AM

None at all.

#10 of 61 BraveHeart123

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Posted November 27 2012 - 02:51 AM

Another very important question, shall I go sealed or ported?? I eventually want to get rid of Klipsch SUB-12, and add another DIY after this. Can I still achieve depth in sealed box i.e. close to 20 hz?? Can I get away with not using SSF if I go with ported design i.e. I tune the port below the lowest LFE in most movies? If you can guide me on the above, I will model the box and post it here.

#11 of 61 Dave Upton

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Posted November 27 2012 - 03:10 AM

Lower extension in a sealed box generally requires more power. Model it in WinISD and you'll be able to see the various options/results.



#12 of 61 BraveHeart123

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Posted November 27 2012 - 03:52 AM

Um posting my findings in WinISD below. It automatically calculated Xmax at be 17 mm and Z at 6 ohms. Whereas the publiushed specs are 20 mm and 4 ohms respectively. Doesn't let me change. Am I doing something wrong here?? The Transfer Function Plot shows T/S parameters. Pls have a glance at the graphs. For ported box, I've kept the port size to 3 inches dia and length to 12 inches. Box size is 3.5 for both box types; [ATTACHMENT=419]Plot.jpg (230k. jpg file)[/ATTACHMENT] [ATTACHMENT=420]SPL.jpg (194k. jpg file)[/ATTACHMENT] [ATTACHMENT=421]ConeExcursion.jpg (215k. jpg file)[/ATTACHMENT] [ATTACHMENT=422]Amp_Load.jpg (192k. jpg file)[/ATTACHMENT]

#13 of 61 BraveHeart123

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Posted November 27 2012 - 03:58 AM

Sorry, embedding images in the post here

#14 of 61 Robert_J

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Posted November 27 2012 - 06:09 AM

Based on your excursion graph, you are overpowering the driver. I make sure that I don't hit xmax above tuning on my ported boxes. I don't hit xmax on my sealed boxes until 10hz. Yes, you can easily play below 20hz with a sealed box. I do. My response is flat to 17hz with usable bass below 15hz. But I have to boost the low end (17hz filter) by about 4db. But since I use drivers with 30+ mm of excursion, they never come close to xmax.

#15 of 61 BraveHeart123

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Posted November 27 2012 - 01:48 PM

500 watts keeps the xmax within 17 mm, but how can i limit the crown to 500 watts?? Can you pls model a ported box in Unibox and validate my results?? the T/S parameters are mentioned in one of the graphs above. I'm not even sure I have done it right in WinISD coz it's my first time with it.

#16 of 61 BraveHeart123

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Posted November 27 2012 - 03:58 PM

Anyone using WinISD, can you pls model this sub in a ported box tuned to 20Hz wired in series (4 ohms) and also in a sealed box keeping in mind xmax value??? I am not sure if I modelled it correctly in WinISD Pro. Alpine SWR-1223D T/S Parameters Fs = 28 hz Vas = 43 L Qts = 0.47 Qms = 0.50 Qes = 8.5 Re = 1.85 ohms + 1.85 ohms Xmax = 20 mm Peak-to-Peak Excursion = 72 mm Sd = 480 cm sq Pe = 600 watts SPL = 85dB The parameters listed are taken from the manual and not derived from "Auto Calculate" feature in WinISD while inputting driver parameters.

#17 of 61 BraveHeart123

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Posted November 28 2012 - 02:52 AM

Anyone??? Pls bear in mind um on the flip side of the coin in terms of time zone between US and Pakistan and I wait for at least 10 hrs to see any reply against my posts. So it's sadening to see none thus far.

#18 of 61 Robert_J

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Posted November 28 2012 - 04:16 AM

It's my on-call week and this PC does not run Unibox since I use Open Office Calc instead of Excel. I'll do my best to run a simulation in the next few days. If you want faster response, the DIY section at AVS Forum has many more active posters than here.

#19 of 61 BraveHeart123

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Posted November 28 2012 - 04:32 AM

my on-call

We have something in common :) but I assign on-call duties to engineers. Anyway thanx Robert for blowing a sigh of relief. I will wait here. Btw I will recieve Alpine SWR-1223D by Friday....ordered it this eve. The closest Alpine dealer is 1100 miles away :(

#20 of 61 BraveHeart123

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Posted November 29 2012 - 02:38 AM

Hi Robert..... Till you get time to design sub box in Unibox, I have the following questions if u can help;
  • WinISD calculates net box volume. It doesn't factor in the volume taken up by the driver and port. How to calculate the driver volume?? For port, I want to use slot port coz it is easier to make. I want a front loaded slot design similar to the ones in Klipsch SW-112 and 115.
  • I will be using slot port inside the box in such a way that three sides of the box share the walls with the port. In this case how do I calculate the volume taken up by slot??
  • Can a use an FMOD (20Hz HPF) as a cheap alternative to SSF?? Or do I tune the port low enuf i.e. close to 15hz to avoid the sub bottoming out??





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