New 15" Sub build - need feedback

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   I've got plans on building a new system with an emphasis on being 
portable and scalable. My current system includes two extended LAB Horns
 (12pi horns by Wayne Parham) - and while the performance is phenomenal,
 I'm tired of moving them.

Here's my design using a  PRV 15SW2000 in a 145 liter enclosure tuned to 40hz. Dimensions are 17.5" x 26.5" x 26.5" - to match up with Weltersys' Syntripp.
My
 goal is to be small+light enough to carry up stairs alone (I have two 
second floor venues in our town with no elevator) and also small enough 
to easily fit a pair in a mid-size SUV for smaller gigs. I plan to start
 with 4, but eventually build 8 boxes for a full stack for raves/dance 
events. I will also make port plugs to block half the slot port to drop 
the tune to 28hz for genres that need the extension.

I
 recently built a new compact amp rack with DSP and two CVR D-1004 
amplifiers. The D-1004 is rated to 89v RMS per channel, which will just 
push these 8ohm drives to their 1000w RMS rating and 12.5mm xmax. But 
PRV also makes the 15SW2000 in a 4ohm version. If I were just going to 
build 4 subs, I would get the 4ohm version so I didn't have to run the 
amps right up to their volt max to get 100% out of my subs, but if I 
decide to run all 8 subs, I don't know how well the CVR amps will do at 
2ohm (the amps are rated to 2ohm). I will split the subs between both 4 
channel amps (each amp runs 1 high, 1 mid, and 2 sub channels) so the 
load is evenly distributed on two circuits and two power supplies.

So my questions are:
Would you build 4 or 8 ohm cabs?
Does anyone have experience with their CVR D-Series at 2ohms?
Does anyone with CVR D-Series have experience running their amps right up the the built-in limiters?
Anyone have experience with PRV drivers? By their spec sheet, they seem to be an incredible value - almost too good to be true.

Thanks for any critical feedback!

Edited by jmorken - 02 March 2023 at 11:04pm

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jmorken Members Profile Send Private Message Find Members Posts Add to Buddy List New Member Joined: 29 July 2011 Location: United States Status: Offline Points: 5	Post Options Post Reply Quote jmorken Report Post Thanks(0) Quote Reply Topic: New 15" Sub build - need feedback Posted: 02 March 2023 at 10:56pm
	I've got plans on building a new system with an emphasis on being portable and scalable. My current system includes two extended LAB Horns (12pi horns by Wayne Parham) - and while the performance is phenomenal, I'm tired of moving them. Here's my design using a PRV 15SW2000 in a 145 liter enclosure tuned to 40hz. Dimensions are 17.5" x 26.5" x 26.5" - to match up with Weltersys' Syntripp. My goal is to be small+light enough to carry up stairs alone (I have two second floor venues in our town with no elevator) and also small enough to easily fit a pair in a mid-size SUV for smaller gigs. I plan to start with 4, but eventually build 8 boxes for a full stack for raves/dance events. I will also make port plugs to block half the slot port to drop the tune to 28hz for genres that need the extension. I recently built a new compact amp rack with DSP and two CVR D-1004 amplifiers. The D-1004 is rated to 89v RMS per channel, which will just push these 8ohm drives to their 1000w RMS rating and 12.5mm xmax. But PRV also makes the 15SW2000 in a 4ohm version. If I were just going to build 4 subs, I would get the 4ohm version so I didn't have to run the amps right up to their volt max to get 100% out of my subs, but if I decide to run all 8 subs, I don't know how well the CVR amps will do at 2ohm (the amps are rated to 2ohm). I will split the subs between both 4 channel amps (each amp runs 1 high, 1 mid, and 2 sub channels) so the load is evenly distributed on two circuits and two power supplies. So my questions are: Would you build 4 or 8 ohm cabs? Does anyone have experience with their CVR D-Series at 2ohms? Does anyone with CVR D-Series have experience running their amps right up the the built-in limiters? Anyone have experience with PRV drivers? By their spec sheet, they seem to be an incredible value - almost too good to be true. Thanks for any critical feedback! Edited by jmorken - 02 March 2023 at 11:04pm

Conanski Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 26 January 2006 Location: Canada Status: Offline Points: 2401	Post Options Post Reply Quote Conanski Report Post Thanks(1) Quote Reply Posted: 03 March 2023 at 2:01am
	I don't think 4ohm drivers have any benefit over the identical 8ohm version in most cases, unless you are doing a series/parallel arrangement inside a single cab but that doesn't usually apply to subs. A 4ohm driver uses more power to produce the same output SPL the 8ohm version would produce at that drive voltage, so from a system logistics perspective you need more current into the amplifiers which makes the system less electrically efficient overall. That may not be a gig deal on shore power but if you ever run on a generator it could be an issue. I think you need to take a close look at the specs for the drivers you are considering to know if this applies to them. Fundamentally loudspeakers are voltage responsive devices and the power dissipated is a side effect, and really the goal should to get the most SPL for the least amount of power. Edited by Conanski - 03 March 2023 at 2:05am

jmorken Members Profile Send Private Message Find Members Posts Add to Buddy List New Member Joined: 29 July 2011 Location: United States Status: Offline Points: 5	Post Options Post Reply Quote jmorken Report Post Thanks(0) Quote Reply Posted: 03 March 2023 at 2:45am
	I had not considered the current side of the equation like that! The 8ohm version requires 85 volts to reach 1000 watts, which ohms law says requires 11.23A of current. The 4ohm requires just 65 volts to reach 1000 watts, but requires 15.38A of current. Considering I'm mostly limited to 120v mains, keeping current down will probably keep the amps happy. Thanks!

Conanski Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 26 January 2006 Location: Canada Status: Offline Points: 2401	Post Options Post Reply Quote Conanski Report Post Thanks(0) Quote Reply Posted: 03 March 2023 at 3:53am
	Right but I think you will find that SPL follows voltage not power so 65v into the 4ohm driver won't produce as much SPL as 85v into the 8ohm,

Xoc1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 15 October 2012 Location: Devon UK Status: Offline Points: 338	Post Options Post Reply Quote Xoc1 Report Post Thanks(0) Quote Reply Posted: 03 March 2023 at 5:31pm
	So the PRV audio spec is 12.5 mm Xmax, 36 mm peak-to-peak excursion before damage So 18mm one way x-damage So your sims show up to 28mm one way - You have not shared your input screen so not so easy to run the sim to see what Hi-Pass filter you would need to run, but I would suspect that you are going to run out of excursion. You may find that you can raise the tuning frequency to gain efficiency - Or you could reduce the power and be limited by excursion. But as is I think the speakers may not have a long life span

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11696	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 03 March 2023 at 7:42pm
	The cabinet seems very large for a single 15". 145 litres is enough volume for some 18" drivers. The driver resonance is at 53Hz and although you can sometimes get away with tuning a cabinet slightly below that, it's not something I would generally recommend. Definitely not as low as 28Hz. I expect that in a slightly smaller cabinet tuned slightly higher, using that driver you will get a good general purpose bass cabinet, usable (not flat) down to around 40Hz. But, if you're looking for low extension, I probably wouldn't recommend it. I also find that WinISD is better for reflex enclosures than Hornresp.