RL-P15's, Choose D2 Ohm, or D4 Ohm?

[Chris in Dallas]

What are the criteria for choosing between the dual 2 ohm and dual 4 ohm versions of the RL-P15's? The numbers are different on the drivers, but are those numbers representative of all circuit config of the voice coils? Or, do they represent the coils wired in series, for 4 ohm and 8 ohm loads, respectively?

I just want to build what seems to be the standard sonosub design here: a 15" driver with 260 net liters, and a 14 hz tune. I have a Crown Macrotech 1200, which is very stable (and probably under-rated for power) putting out 700 wpc into 2 ohms. I'd like to build a pair of sonosubs for it.

Are the two subs mentioned effectively interchangeable?

[bonehead848]

Each coil is 2 or 4 ohms respectively.

If you are just planning one sub per channel get the D4 and wire each in parallel for a 2 ohm load on each channel. If you are wanting to bridge it use the same configuration just wire the two subs in series.

[Chris in Dallas]

Thanks, bonehead. But do the technical specs have any impact on the results? That is, what about the different listed Fs, Qts, etc, as seen here: http://www.soundsplinter.com/rlp15_s...formation.html

[Chris in Dallas]

Well, however it works, I hope I can get the dual 4 ohm models to perform to their potential. I say that, because I have just picked up two of them, and I am quite excited about it.

20" x 12' Sonotube (brand) at the local supplier, CMC Services: $93.48, or $7.79/ft.

Anyone know about the Precision Port Flares and tubes? I think I could piece together everything for a 34" 6" port with 2 flares for well under $100 (sorry, I don't have enough time to make my own flares).

Are the precision ports, etc., quality equipment?

[Mike P.]

I've used the 4 inch Pecision Ports extensively and they are excellent quality. I would imagine the 6 inch model would be the same.

[Chris in Dallas]

Thanks for the reference. That's how I'll do it, then.

[Warmon]

Chris in Dallas wrote:

Well, however it works, I hope I can get the dual 4 ohm models to perform to their potential. I say that, because I have just picked up two of them, and I am quite excited about it.

Strange that the D2 version has certain specs that are better suited for home use than the D4 - especially Fs. From what I've read, any driver can be used, but EBS type enclosures work best when Qts is <.35. D4 is certainly better for most HT wiring situations.

I wonder if they model the same..

[mlstrass]

I ran 2 of the D4's in my car and moved them into the HT last year. Each one is in 10cubes tuned around 18Hz. Only getting 400watts each and they sound amazing for music and movies. I know they model a little differently, but in the real world I imagine it makes little difference.

My two fav demos are: Godsmack dualing drum solos & depth charges in U-571. One shakes the house to death, the other punches you in the chest with the kick drums.

I personally don't care for super low bass that just beats up the house, so I didn't do an LLT.

[Chris in Dallas]

mlstrass, did you use a ported design? Was it sealed? How does yours model?

[Bent]

Unibox suggests a sealed box for the D4's

[Chris in Dallas]

Bent wrote:

Unibox suggests a sealed box for the D4's

What do mean that it suggests that? Does it literally suggest it?

[Mike P.]

Warmon wrote:

Strange that the D2 version has certain specs that are better suited for home use than the D4 - especially Fs. From what I've read, any driver can be used, but EBS type enclosures work best when Qts is <.35. D4 is certainly better for most HT wiring situations.

I wonder if they model the same..

Good question:


Red-RL-p15 2ohm
Green- RL-p15 4ohm

[Chris in Dallas]

I would guess, looking at those graphs, that a little equalization would make them about the same. Question: How much does the wiring config affect the curve? Does wiring in parallel create different sonic specs than when wiring in series? Also, if you want a two-ohm nominal load, do you have to choose the D4 and wire in parallel, or is there a way to make the D2 produce a nominal 2 ohm load?

[mlstrass]

Each one is in 10 cubes tuned around 18-19Hz. Someone else modeled it for me. I went with a little higher tune for a little more SPL and a little less real low stuff, just the way I like it.

[Warmon]

I came across some information that JBL puts out saying that transient response is degraded when wiring subs in series. It was pretty technical, but the jist of it had to do with delays from one sub to the next - like #2 had to wait on #1 before it could do its thing. At the time I was thinking about buying some NOS GTI's.

I have three 4ohm Polk DVC's wired in series and I can't say that I notice anything lagging or anything. Chris, in your case I would think you'll want to wire the coils in series and the subs parallel and run your amp bridged.

From the graph, looks like the D4 has sacrificed a little on the mid-bass to get more output <20. D4 is a little lower. D2 is a little louder.

If Unibox suggest a sealed box, that would mean EBP is closer to 50 than 100, right?

[Chris in Dallas]

Warmon wrote:

I came across some information that JBL puts out saying that transient response is degraded when wiring subs in series. It was pretty technical, but the jist of it had to do with delays from one sub to the next - like #2 had to wait on #1 before it could do its thing. At the time I was thinking about buying some NOS GTI's.

I have three 4ohm Polk DVC's wired in series and I can't say that I notice anything lagging or anything. Chris, in your case I would think you'll want to wire the coils in series and the subs parallel and run your amp bridged.

From the graph, looks like the D4 has sacrificed a little on the mid-bass to get more output <20. D4 is a little lower. D2 is a little louder.

If Unibox suggest a sealed box, that would mean EBP is closer to 50 than 100, right?

First, what the hey do you mean by EBP? Second, thanks for the wiring suggestion, which sent me back to the Crown reference section. As it turns out, running in regular bridged mono at the four ohm load, that would result from a series/ parallel circuit as you describe, would yield the amp's highest 20 Hz output: 1475 watts, which I suppose will be 737.5 seriously under-rated watts (that's Crown's policy) per driver. Sweet. That should do it.

I have asked SS directly about the effect of the specs on the sub performance, and why someone might choose one or the other. I'll get back with the response.

[Warmon]

Chris in Dallas wrote:

First, what the hey do you mean by EBP?

EBP is the Efficiency Bandwidth Product - a number derived from dividing Fs by Qes. The resulting number is used to determine whether a particular driver is better suited to a sealed or ported alignment. Closer to 50 - sealed, Closer to 100 - ported.

D4 is 27.487 / 0.508 = 54.11
D2 is 23.426 / 0.363 = 64.53

[Chris in Dallas]

Warmon wrote:

EBP is the Efficiency Bandwidth Product - a number derived from dividing Fs by Qes. The resulting number is used to determine whether a particular driver is better suited to a sealed or ported alignment. Closer to 50 - sealed, Closer to 100 - ported.

D4 is 27.487 / 0.508 = 54.11
D2 is 23.426 / 0.363 = 64.53

I'm sorry, but shouldn't that be "Efficiency Bandwidth Quotient?"

How's that for picking a nit?

[Warmon]

Chris in Dallas wrote:

I'm sorry, but shouldn't that be "Efficiency Bandwidth Quotient?" How's that for picking a nit?

Hey Chris, what does SS say about your question?

[Bent]

If the EBP < 50, the speaker should be used in a closed back cabinet.
If the EBP > 90, the speaker should be used in an open back or ported cabinet.
If the EBP is between 51 and 89, the speaker may be used in either cabinet.
This is a rule of thumb only. Your results may vary.

Dug this up somewhere.

[Chris in Dallas]

Warmon wrote:

Hey Chris, what does SS say about your question?

No response, yet. Must be busy making speakers.

[atledreier]

I asked the same thing. Mike basically said 'it depends'...

His answer in full:

In so far as voicecoil configuration, it seems that most home theater users who build a box similar to yours (260l, 14Hz tune) end up going with the dual 2ohm configuration, however if you have a power supply that work better with the dual 4 ohm configuration, I would suggest thet the different configuration will by no means 'make or break' your system.

[Chris in Dallas]

I checked for a response from SS among my spam mail, and there, tucked in-between 50 offers of methods to enlarge my "unit" (how did they know?) was the response from Mike:

There isn't going to be a whole lot of response variance between the
different coil configurations. The decision between which coil
configuration to purchase should rest primarily on which amplifier (if any)
you already own or have in mind, so that you can match the nominal impedance
of the driver to the amplifier for the most appropriate power feed. For the
RL-p15, you should be aiming for between 750 - 1000 watts RMS for optimal
performance.

From that, I can say that I am on the right track with my Crown amp.

[Chris in Dallas]

I just got my 15's in, and SHITE!! These are monsters! As soon as I clear a little space in my garage, construction begins!

[Chris in Dallas]

Quick update for pricing: Another Sonotube supplier in Dallas, White Cap Construction (they are located nationwide) sells the 12' x 20" for $75.86. That's a good deal.