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[Steve Garris]

Because you were the last person that posted, that's the way this stupid forum software works.  I wasn't addressing you specifically.


Why would anyone compare a single 18 with a double 18?  The double 18 rents for 25% more, doesn't matter if it doesn't work as well as RCF's single 18.  Nobody cares.

This is the lounge, and I care. To have a single 18" box that will perform as good or better than the double 18 JBL is something that I'm interested in. I have very limited space in my vehicle. Whether the cost is a reasonable expenditure is up to me, I suppose.

[Jay Marr]

This is the lounge, and I care. To have a single 18" box that will perform as good or better than the double 18 JBL is something that I'm interested in. I have very limited space in my vehicle. Whether the cost is a reasonable expenditure is up to me, I suppose.

Same here.

I thought the OP was a very reasonable question and I was interested in the answer for exactly what you stated above.
I bring a SRX728 to ever gig...could that be outperformed by a single 18" and save me some car space?  If so, I'd like to be informed.

Folks also will bring up - "well are you going to make more money if you buy this gear?  if not, keep what you have."
That's not advice I'm ever looking for.  I make my purchase decisions for my reasons.  It's almost never ROI (for me). 
I know very well how to manage my money.

I come here for pro audio advice, not business advice.

[Tim McCulloch]

Same here.

I thought the OP was a very reasonable question and I was interested in the answer for exactly what you stated above.
I bring a SRX728 to ever gig...could that be outperformed by a single 18" and save me some car space?  If so, I'd like to be informed.

Folks also will bring up - "well are you going to make more money if you buy this gear?  if not, keep what you have."
That's not advice I'm ever looking for.  I make my purchase decisions for my reasons.  It's almost never ROI (for me). 
I know very well how to manage my money.

I come here for pro audio advice, not business advice.

Those can't be separated unless you're solely and exclusively a hobbyist.  And if you're a hobbyist pursuing paid work in my market, expect your clients to be asking to be named as additional insureds on your liability policy, proof of commercial vehicle insurance, proof of workman's comp insurance, etc as I'll make sure they know to ask.  Yeah, it's that kind of thing, Jay - why should anyone give you information to help you compete against folks for whom this represents their income, not a hobby?

[Art Welter]

I'm curious to hear the responses and see the math/technical answer on this as well.  I would imagine that the dual 18 (JBL) would outperform the single 18 (RCF)  Since the RCF is a higher end model, would it make it more of a fair fight?  Someone once told me, there's no replacement for displacement.   Definitely looking forward to someone diving into this a little more in depth.

Matt G & V, Jay, Steve, Mike,

Yes, there is no replacement for displacement, but whether that displacement is achieved using one, two or more cones the end result is the same.

In terms of output, dual 18” bass reflex subs such as the JBL SRX728 or the SRX828SP can be equalled by a single 18” of half the size using a driver with double the linear displacement, the Xmax specification, measured in mm (millimeters).

Doubling excursion results in 6 dB more output, but also requires 6 dB more input. The additional power required, and the loss of 3dB sensitivity of double the cone area may result in more thermal compression from voice coil heating, which could prevent a straight 2/1 reduction.

The SRX828SP uses the 2242HPL driver, 7.47mm Xmax, the SRX728 uses the 2268, 8mm Xmax. 
RCF’s LF18N405 has 14mm Xmax, about double the displacement of those JBLs, it’s likely a similar driver is used in the RCF SUB8004AS.
JTR Speakers use drivers with as much as 33mm Xmax, another doubling of excursion.

The higher excursion, higher power drivers cost more to produce and power, so “you get what you pay for”, though JTR Speakers does offer a better “bang for the buck” than a lot of more well known companies that spend more on advertising and less on drivers..

If you are renting “sound by the pound”, and “nobody cares” about anything other than driver count, by all means stick with the medium or low output drivers.
If you want to maximize output and reduce transport/storage/deployment size and cost, then using cabinets utilizing higher displacement drivers should be considered.

[Jay Marr]

Jay - why should anyone give you information to help you compete against folks for whom this represents their income, not a hobby?

Great question - so my scenario (and who's to say the OP's isn't same as mine).  I provide sound for my band, and my band only (one of the descriptions of 'The Lounge' section of this forum).
I'm not competing with any sound professionals.  Me having a dual 18 vs. a single 18 has zero impact on anyone else....just my back and my budget.
My point being - when asking purely for audio advice, and me being in competition with nobody, I'm not sure why it's always accompanied by 'here are business reasons why not to purchase'.

[Scott Holtzman]

Same here.

I thought the OP was a very reasonable question and I was interested in the answer for exactly what you stated above.
I bring a SRX728 to ever gig...could that be outperformed by a single 18" and save me some car space?  If so, I'd like to be informed.

Folks also will bring up - "well are you going to make more money if you buy this gear?  if not, keep what you have."
That's not advice I'm ever looking for.  I make my purchase decisions for my reasons.  It's almost never ROI (for me). 
I know very well how to manage my money.

I come here for pro audio advice, not business advice.

Well it was somewhat of a lighthearted joke when I started as we seem to always have a discussion comparing some two random products in the same category.


I wasn't giving money advice, it was sub selection.  The answer is it doesn't matter.  If the RCF fits in your car then buy that one, if you like the JBL then buy that one.  Comparing nuanced differences in the sound and minor output changes is a waste of time.   


As you said this is the lounge, nobody will notice.  Maybe in some EDM, dance corner case but for the vast majority it's your obsession not theirs.


A whole bunch of people chimed in that I respect (that also took my post not in the way intended) and that is surprising to me that this much mentally energy is being spend on what Tim refers to as "lateral moves".  I didn't expect the seasoned hands to say anything because these comparison threads are usually started by someone who barely has business justification for the purchase and the purchase is a big one for them so they end up in this paralysis by analysis mode because they can't afford to spend twice.  That was the truth I was bringing up, that as part of your business plan the sub you purchase will not impact the success or failure of your business.


So Jay if it's not about business, it's not about money what is about?

[Miguel Dahl]

Great question - so my scenario (and who's to say the OP's isn't same as mine).  I provide sound for my band, and my band only (one of the descriptions of 'The Lounge' section of this forum).
I'm not competing with any sound professionals.  Me having a dual 18 vs. a single 18 has zero impact on anyone else....just my back and my budget.
My point being - when asking purely for audio advice, and me being in competition with nobody, I'm not sure why it's always accompanied by 'here are business reasons why not to purchase'.

I guess that it's because it's an pro audio forum, pro, people do it for a living. But heck. If it's that pro that we would need to "screen" the hobbyists from the people who live off of this, to answer them, this should be a closed forum.  It's an open forum as it is. So I find it strange to not to share the knowledge with people asking here, even if I see Tim's point. But there's more separation between pro and hobby (like he said with insurances and the like) than just "doing sound".

[Tim McCulloch]

Great question - so my scenario (and who's to say the OP's isn't same as mine).  I provide sound for my band, and my band only (one of the descriptions of 'The Lounge' section of this forum).
I'm not competing with any sound professionals.  Me having a dual 18 vs. a single 18 has zero impact on anyone else....just my back and my budget.
My point being - when asking purely for audio advice, and me being in competition with nobody, I'm not sure why it's always accompanied by 'here are business reasons why not to purchase'.

Fair enough.

[Scott Holtzman]

I guess that it's because it's an pro audio forum, pro, people do it for a living. But heck. If it's that pro that we would need to "screen" the hobbyists from the people who live off of this, to answer them, this should be a closed forum.  It's an open forum as it is. So I find it strange to not to share the knowledge with people asking here, even if I see Tim's point. But there's more separation between pro and hobby (like he said with insurances and the like) than just "doing sound".

Share what knowledge?  Endlessly comparing subwoofers for differences?  Buy the one you want.


That was my point, endlessly gnashing over which one to buy, seems like a waste of time.


I started it off lighthearted, clearly this is near and dear to folks.  I was just like "looky another sub thread, oh boy"  this really got legs. 

[Matt Greiner]

Matt G & V, Jay, Steve, Mike,

Yes, there is no replacement for displacement, but whether that displacement is achieved using one, two or more cones the end result is the same.

In terms of output, dual 18” bass reflex subs such as the JBL SRX728 or the SRX828SP can be equalled by a single 18” of half the size using a driver with double the linear displacement, the Xmax specification, measured in mm (millimeters).

Doubling excursion results in 6 dB more output, but also requires 6 dB more input. The additional power required, and the loss of 3dB sensitivity of double the cone area may result in more thermal compression from voice coil heating, which could prevent a straight 2/1 reduction.

The SRX828SP uses the 2242HPL driver, 7.47mm Xmax, the SRX728 uses the 2268, 8mm Xmax. 
RCF’s LF18N405 has 14mm Xmax, about double the displacement of those JBLs, it’s likely a similar driver is used in the RCF SUB8004AS.
JTR Speakers use drivers with as much as 33mm Xmax, another doubling of excursion.

The higher excursion, higher power drivers cost more to produce and power, so “you get what you pay for”, though JTR Speakers does offer a better “bang for the buck” than a lot of more well known companies that spend more on advertising and less on drivers..

If you are renting “sound by the pound”, and “nobody cares” about anything other than driver count, by all means stick with the medium or low output drivers.
If you want to maximize output and reduce transport/storage/deployment size and cost, then using cabinets utilizing higher displacement drivers should be considered.

Art, thank you for your time in explaining this.  The way you explained it helps me "see" the numbers more clearly and what you should be able to expect.

Well it was somewhat of a lighthearted joke when I started as we seem to always have a discussion comparing some two random products in the same category.

Scott, I had a very long day yesterday, and I took your response clearly not as you intended, my apologies.

 The brutal honesty around here is one of the things that I truly appreciate about this forum.  No sugar coating or unsincere "Yeah, you should totally do that".  Art was able to explain the science in a way that made sense, and I will be able to take that knowledge into the future and apply it as needed.

As I don't live in an area where I can easily demo products, first-hand experience is critical to my decision making. I'd rather hear from members of this forum than trust an online review where there is no accountability.  And while I have only met a few of the members on here IRL, I feel confident that most of what you read on here is accurate, because every member helps keeps everyone honest in regards to their posts.  I'm glad I came across this great resource!

[ProSoundWeb Community]