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Author Topic: Decent 2x18" subwoofer  (Read 8518 times)

Helge A Bentsen

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Decent 2x18" subwoofer
« on: May 25, 2016, 06:01:10 pm »

A few years back, if you wanted a decent 2x18" passive subwoofer, "everybody" seemed to agree on the JBL SRX728 as a good choice.

AFAIK it's now discontinued.

Has a new favorite emerged on this forum?

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Josh Rawls

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Re: Decent 2x18" subwoofer
« Reply #1 on: May 25, 2016, 07:14:53 pm »

I just got a JBL SRX828SP and I'm very happy with it. I bought a SRX818SP first and I sometimes couple them together.
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Josh Rawls

Spenser Hamilton

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Re: Decent 2x18" subwoofer
« Reply #2 on: May 25, 2016, 07:38:10 pm »

I just got a JBL SRX828SP and I'm very happy with it. I bought a SRX818SP first and I sometimes couple them together.

The SRX828 is tuned significantly higher, that probably doesn't matter to most people, but I don't think it stands up to the 728 based on that alone.
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Helge A Bentsen

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Re: Decent 2x18" subwoofer
« Reply #3 on: May 26, 2016, 04:20:00 am »

I just got a JBL SRX828SP and I'm very happy with it. I bought a SRX818SP first and I sometimes couple them together.

Thanks, but SRX828SP is only availale as a powered sub AFAIK.

 I'm looking for a passive one.
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Duane Macsymach

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Re: Decent 2x18" subwoofer
« Reply #4 on: May 26, 2016, 04:37:23 am »

« Last Edit: May 26, 2016, 04:44:51 am by Duane Macsymach »
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Scott Carneval

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Re: Decent 2x18" subwoofer
« Reply #5 on: May 26, 2016, 09:20:54 am »

Thanks, but SRX828SP is only available as a powered sub AFAIK.

 I'm looking for a passive one.

The powered SRX is actually LESS than the 728 used to sell for. If I was in the market for a 2x18 it would be at the top of my list. Another sub that compares favorably is the QSC GP218.

If you were in the market for a PAIR of 2x18's, I would pony up the extra cash for a TH118. Costs a little less than a pair of 2x18, and performs about as well as two of them. Overall you would spend less money, have the same or possibly a little more output, and have less to pack and carry vs. a pair of 2x18's.
« Last Edit: May 26, 2016, 09:22:57 am by Scott Carneval »
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John L Nobile

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Re: Decent 2x18" subwoofer
« Reply #6 on: May 26, 2016, 10:40:23 am »

Passive in SRX is available now
http://www.jblpro.com/www/products/portable-market/srx800-passive-series/srx828s#.V0a1KukjMUU

Another good choice 
http://www.jblpro.com/www/products/portable-market/stx800-series/stx828s#.V0a2zOkjMUU

Speaker specs give me headaches.

SRX 828S

System Type   Passive dual 18, subwoofer system
Maximum SPL Output   141dB
Frequency Range (-10dB)   30hz - 150hz
Frequency Response (- 3dB)   47hz - 150hz
Sensitivity (1W/1m)   96dB
System Power Rating   4800W Peak, 2400W Program, 1200W Continuous
Nominal Impedance   4 Ohm

Danley SBH 218

operating frequency range 34 Hz- 300 Hz -3dB
28 Hz - 400 Hz -10dB
continuous output 141 dB SPL peak output 147 dB
SPL sensitivity 117 dB SPL (2.83 Volts into rated Z, at 1 meter) measured in half space
Power Rating 3600 watts continuous
14,400 watt peak


How does a box that takes less power and a lot less sensitivity post the same output level? According to the specs, I should be able to get about the same level with a little less low end from the JBL.
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Scott Carneval

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Re: Decent 2x18" subwoofer
« Reply #7 on: May 26, 2016, 11:10:17 am »

Speaker specs give me headaches.

SRX 828S

System Type   Passive dual 18, subwoofer system
Maximum SPL Output   141dB
Frequency Range (-10dB)   30hz - 150hz
Frequency Response (- 3dB)   47hz - 150hz
Sensitivity (1W/1m)   96dB
System Power Rating   4800W Peak, 2400W Program, 1200W Continuous
Nominal Impedance   4 Ohm

Danley SBH 218

operating frequency range 34 Hz- 300 Hz -3dB
28 Hz - 400 Hz -10dB
continuous output 141 dB SPL peak output 147 dB
SPL sensitivity 117 dB SPL (2.83 Volts into rated Z, at 1 meter) measured in half space
Power Rating 3600 watts continuous
14,400 watt peak


How does a box that takes less power and a lot less sensitivity post the same output level? According to the specs, I should be able to get about the same level with a little less low end from the JBL.

There's a couple of things about those specs that can be misleading.

1. JBL gives a maximum output of 141db, but that is no doubt their peak number. Continuous output would be 135db if you subtract 6db from the peak rating. But with a sensitivity of 96db, and a gain of 30.8 db based on 1200 watts continuous power rating, according to my abacus that is 126.8 db. You could give them the benefit of the doubt that the measurement was taken in whole-space, and add 3db for real-world usage, but you're still at 129.8db.

2. Danley rates their sensitivity at '2.83v @ 1 meter'. While this is a more ACCURATE way to measure (because impedance varies with frequency, 1w1m is never really 1 watt), it can also be misleading when compared to the more common '1 watt @ 1 meter' measurement. The DBH218 is a 2 ohm cabinet, and 2.83v at 2 ohms is more like 4 watts. So to reference this to 1 watt would be more like 111db sensitivity, BUT because impedance varies with frequency that isn't really an accurate way to measure.

Rest assured, the SRX828 is not in the same ballpark as the DBH218 when comparing output.
« Last Edit: May 26, 2016, 11:19:29 am by Scott Carneval »
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Robert Piascik

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Re: Decent 2x18" subwoofer
« Reply #8 on: May 26, 2016, 11:20:49 am »


I've changed my thinking in that I don't care anymore if a box is (what is now) standard sub configuration: 2x18.

My Danley TH118 subs blow away most 2x18 boxes at a fraction of the space and weight. For my Lounge Level requirements they satisfy the requirement exceedingly well.
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John L Nobile

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Re: Decent 2x18" subwoofer
« Reply #9 on: May 26, 2016, 11:44:17 am »

There's a couple of things about those specs that can be misleading.

1. JBL gives a maximum output of 141db, but that is no doubt their peak number. Continuous output would be 135db if you subtract 6db from the peak rating. But with a sensitivity of 96db, and a gain of 30.8 db based on 1200 watts continuous power rating, according to my abacus that is 126.8 db. You could give them the benefit of the doubt that the measurement was taken in whole-space, and add 3db for real-world usage, but you're still at 129.8db.

2. Danley rates their sensitivity at '2.83v @ 1 meter'. While this is a more ACCURATE way to measure (because impedance varies with frequency, 1w1m is never really 1 watt), it can also be misleading when compared to the more common '1 watt @ 1 meter' measurement. The DBH218 is a 2 ohm cabinet, and 2.83v at 2 ohms is more like 4 watts. So to reference this to 1 watt would be more like 111db sensitivity, BUT because impedance varies with frequency that isn't really an accurate way to measure.

Rest assured, the SRX828 is not in the same ballpark as the DBH218 when comparing output.

Scott, you're the aspirin for my headache :)

I know they're at different levels but they sure do look close on the spec sheets. I'm trying to figure out if I have enough sub for the gig. The room we're in has had a total of 6 dbl 18" subs for bands and I'm hoping to get the same level with 2 SBH218's. I can't A/B them as I'd have to rent them to do that so spec sheets is all I thought I had to go on. They seem useless so I guess I gotta rely on faith.

Seems like I need to do a little research on electrical formulas.
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ProSoundWeb Community

Re: Decent 2x18" subwoofer
« Reply #9 on: May 26, 2016, 11:44:17 am »


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