8 ohm/4 ohm = rarely use amp's full potential

[agedhorse]

My friend I usually find your posts very informative, but I have to disagree with your characterization of 3 dB as the “minimum we hear clearly”. That is 1 dB, which is precisely why decibels sound pressure were defined the way they were.

dB: What is a decibel?

At lower frequencies and at higher volumes, most folks have a difficult time identifying clearly a 1dB difference IME.

 

[ThisBass]

Sounds like you're saying that most cabs that have 2 x10 or 2x12 are 4Ω cabs and that's just not so. I have a 210 cab that is 8ohm myself and there are a LOT of 210 and 212 cabs that are 8 ohm. They typically use 16Ω speakers wired in parallel to get an 8Ω cabinet. Or perhaps I am misunderstanding what you are trying to say?

The big majority of all produced cone loudspeakers worldwide are 8 Ohm loudspeakers.
Some companies such as Eminence and Faital (and others more) do also produce 4 Ohm variants of some of their 8 Ohm models but, the majority of their product range are all 8 Ohm loudspeakers.
And some companies such as Eminence do also produce a small product range of 16 Ohm loudspeaker models.
Companies such as Eminence and Faital (and others more) do also produce OEM drivers which (of course) may show a nominal impedance that equals 16 Ohm, or even 32 Ohm loudspeakers that are intended to be used in the fridge (4 Ohm cab).

To me its not surprising nothing at all that most of all 210 and 212 cabinets you can buy from elsewhere and from any company then do show an impedance that equals 4 Ohm.
Some of those "twin loaded" cabs are different and may show 8 Ohm or even 16 Ohm but, those cabs are nothing but an exception to the rule.

edit:
the OP asks explicitely for "single" cabs rather than for "single driver loaded" cabs. That's the very difference.

 

[agedhorse]

Most 210's these days are now 8 ohm cabinets because there are very few 4 ohm 210 cabinets that can safely handle the output of today's higher powered amps. By and large, the majority of the higher quality 8 ohm 210's use 16 ohm drivers wired in parallel.

 

[ThisBass]

AFAIK 8 ohms for 210 and 212 cabs has become more and more common.

I'd say in the meanwhile there are more 8 Ohm 210 and 212 cabs available than it was (may be) about 10 years before or so.
But I don't see these were more common in the meanwhile.

There are still plenty of 4 Ohm 210's and 212's available from any company and also from any custom shop cab builders.

 

[ThisBass]

The OP does NOT ask for a distinct driver format. If the cab shall be rather small yet "move" some air, a 4 Ohm 210 might be the right way to go.

 

[Wasnex]

max safe SPL is nowhere near as simple as Efficiency + power.

...and yet this is exactly what most companies appear to publish.

AFAIK: Max calculated SPL is the Sensitivity rating + the decibel change from power. Power is the lower figure of: 1. Max power the amp can push into the speaker(s), or 2. How much of the available power the speaker(s) can handle. From what I have seen, companies tend to publish calculated figures based on their cab's RMS rating more often than actual measured figures. As I am sure you know, measured SPL will be a bit lower due to power compression.

Example:​

-The Subway 210 lists Average Sensitivity of 98.1dB 1W/1m from 50hz-1kHz.
-The Average Thermal Power rating is 600W RMS
-Average Mechanical Power Handling from 50hz-1khz is 500W
-Minimum Mechanical Power Handling is 425W at 81.3hz.
-Max SPL from 50hz-1khz is listed as 126dB/1m.

The 126dB Max SPL figure appears to be calculated rather than measured.​

-The decibel difference between the listed Max SPL and the 1W sensitivity rating is 126-98.1=27.9dB
-An online calculator tells me the decibel change from 1-600W is 27.7dB. My guess is the 0.2dB difference can be attributed to rounding errors.

I am sure you don't need this--Calculator Ref: Watts to dBm conversion calculator (rapidtables.com)​

So Mesa's Max SPL appears to be calculated off the cab's RMS rating and not its lower mechanical limits. My understanding is this is due to the way bass guitar distributes energy across the audio spectrum....I.E. bass guitar produces a relatively weak fundamental. Still if you like to really boost the low end, it would be unwise to hit the cab with 600W. Obviously some discretion and common sense should be used.

​

 

[Wasnex]

I'd say in the meanwhile there are more 8 Ohm 210 and 212 cabs available than it was (may be) about 10 years before or so.
But I don't see these were more common in the meanwhile.

There are still plenty of 4 Ohm 210's and 212's available from any company and also from any custom shop cab builders.

Here's a sampling of the first brands I thought of.

Gallien Krueger Neo IV
210 8 ohms
212 8 or 4 ohms.

Mesa Subway
210 8 ohms
212 4 ohms
215 4 ohm

Genzler
210T 8 ohms
BA210 8 ohms
212T 4 ohm

Eich
210M 8 or 4 ohms
210XA 8 or 4 ohms
212M 8 or 4 ohms
212L 8 or 4 ohms
212S 8 or 4 ohms

Fender
Rumble 210 8 ohms

Ampeg
PN210-HLF 8 ohms
PF-210HE 8 ohms
210AV 8 ohms
210CL 8 ohms
212AV 4 ohms

It does appear that the majority of 210s are 8 ohms.

 

[ThisBass]

My friend I usually find your posts very informative, but I have to disagree with your characterization of 3 dB as the “minimum we hear clearly”. That is 1 dB, which is precisely why decibels sound pressure were defined the way they were.

if I remember correctly then it was Mr. Bell himself (the inventor of the dB scale) who referenced 3dB in difference of SPL as threshold of perception.

edit:
some folks may need 4dB of difference just to rcognize a noticable difference in loudness level, while other folks just 2dB or even less.
The "average" is referenced to 3dB, no more and nor less

 

[ThisBass]

Here's a sampling of the first brands I thought of.

Gallien Krueger Neo IV
210 8 ohms
212 8 or 4 ohms.

Mesa Subway
210 8 ohms
212 4 ohms
215 4 ohm

Genzler
210T 8 ohms
BA210 8 ohms
212T 4 ohm

Eich
210M 8 or 4 ohms
210XA 8 or 4 ohms
212M 8 or 4 ohms
212L 8 or 4 ohms
212S 8 or 4 ohms

Fender
Rumble 210 8 ohms

Ampeg
PN210-HLF 8 ohms
PF-210HE 8 ohms
210AV 8 ohms
210CL 8 ohms
212AV 4 ohms

It does appear that the majority of 210s are 8 ohms.

yeph, it looks like as if you are totally right with the 210 stuff.
I have to admit, I had mainly the 212's in my mind.

Damn, it looks like as if the OP has to stuck with 212 rather than 210.
Doesn't matter too much, the OP didn't ask for a distinct driver format.

How about 215's ? (just kidding)

 

[Ekulati]

Results: If the amp doubles power, but the 4-ohm cab has a 2dB lower sensitivity rating than the 8-ohm cab, you only gain 1dB which is not enough to hear.

This is the right answer, case closed. Trust in the Was.

I use one or two cabs, depending on the gig. 8ohms or 4ohms, I get my amp's "full potential" either way.

 

[micguy]

Most 210's these days are now 8 ohm cabinets because there are very few 4 ohm 210 cabinets that can safely handle the output of today's higher powered amps. By and large, the majority of the higher quality 8 ohm 210's use 16 ohm drivers wired in parallel.

As you stated previously, 4 ohm drivers typically have lower sensitivity. What that means (I'm not sure people get this) is that, while the 4 ohm driver will "utilize the full potential of your amplifier", it's not using it to produce more sound - it's creating about the same amount of sound, and converting the extra power that it draws (compared to an 8 ohm driver) into heat. So, it's harder on your amplifier but doesn't produce more results. It's also more likely to fail because it's getting hot from the wasted power.

Think of it this way: You need an oil change for your car. You have $100 in your wallet. One place (the "8 ohm" oil change place) will do your oil change for $50. Another (the "4 ohm" oil change place) will do it for $100. Yes, the 4 ohm oil change place is "fully utilizing the power available in your wallet", but....is that the real thing you want to optimize?

 

[ThisBass]

So, it's harder on your amplifier but doesn't produce more results. It's also more likely to fail because it's getting hot from the wasted power.

At the other hand side a 4 Ohm amplifier is designed to run safe over time under 4 Ohm load conditions.
Of course predicted "life time" of an electronic device depends on operating temperatur of all of its components. But I wouldn't bother too much with a device that was intentionally designed for 4 Ohm operation.

If I was nit picking enough I might also claim that operation of an 4 Ohm amplifier was "more safe" on a 16 Ohm load versus 8 Ohm load due to reduced operating temperature, thus expected less fail of the amplifier.
In any case, it would be the safest mode to NOT swich on the amplifier anyway!

edit, typo

 

[Snert]

...and yet this is exactly what most companies appear to publish.

Because it's easy, gives a big number, and as most people don't understand at all anything about electrical engineering, they go for the biggest number. It's also technically true as that number doesn't specify the conditions under which it was measured, but it is not really the useable limit of the driver/enclosure. That is something far more complex to determine and trying to explain that to a typical non engineer is going to get you an eye roll and lost interest.

 

[micguy]

At the other hand side a 4 Ohm amplifier is designed to run safe over time under 4 Ohm load conditions.

Safe is a relative thing. One of the key threats to electronic gear is heat. If you have an 8 ohm cabinet that produces comparable output to the 4 ohm one, but with half the current draw, that creates less heat - both in the speaker and in the amplifier. Will the amplifier have a decent lifetime running flat out into a 4 ohm load? Maybe. Will it last longer into an 8 ohm load? Absolutely.

So, let's say your car has a 200 horsepower engine, and it's rated to pull a 5000 pound trailer. No matter what, it will break down faster pulling a trailer all the time than if you use the motor to pull just the car. Rougher service is rougher service.

Your amp is rated for 4 ohms MINIMUM load - that's means it's "OK" to do that. It doesn't mean it's ideal.

 

[Tommy TGrip]

How accurate do you suspect your conclusion is that “most bass players are only going to use a single cab”?

75.44 per cent accurate. Close enough for rock n roll

 

[Rip Van Dan]

The big majority of all produced cone loudspeakers worldwide are 8 Ohm loudspeakers.
Some companies such as Eminence and Faital (and others more) do also produce 4 Ohm variants of some of their 8 Ohm models but, the majority of their product range are all 8 Ohm loudspeakers.
And some companies such as Eminence do also produce a small product range of 16 Ohm loudspeaker models.
Companies such as Eminence and Faital (and others more) do also produce OEM drivers which (of course) may show a nominal impedance that equals 16 Ohm, or even 32 Ohm loudspeakers that are intended to be used in the fridge (4 Ohm cab).

To me its not surprising nothing at all that most of all 210 and 212 cabinets you can buy from elsewhere and from any company then do show an impedance that equals 4 Ohm.
Some of those "twin loaded" cabs are different and may show 8 Ohm or even 16 Ohm but, those cabs are nothing but an exception to the rule.

edit:
the OP asks explicite ly for "single" cabs rather than for "single driver loaded" cabs. That's the very difference.

Well that's a big surprise to Eden since they've been making their 210's with either 8 ohm or 4 ohm impedance all along. It would be particularly short sighted to only make a 4 ohm 210 because usually a single 210 is not enough for large venues and adding a second one gives you a defacto 410.

Eden offered a D210T, a D210XLT, and a D210XST in both 4 ohm and 8 ohm. They currently offer the EX-210, the TN-210, the D210XLT, and the D210XST in both 4Ω and 8Ω impedance. Those 8Ω cabs can use either 4Ω speakers wired in series (4+4=8) or 16Ω speakers wired in parallel for 8Ω. You can't make an 8Ω 210 using 8Ω speakers. And since Eminence has been manufacturing Eden speakers since before David Nordschow left Eden in 2009 to start his new company DNA, Eminence has been making those speakers too. Took them three tries to get the Eden speakers right but they nailed it! And no you can't buy Eden speakers from Eminence. You have to go to Eden to get them. DNA also has all of its cabs available in both 4Ω and 8Ω.

Mesa, Ampeg, Aquilar, Gallien Krueger, Fender, Hartke, MarkBass, Peavey, Darkglass, Ashdown, and acoustic all make 8Ω 210's and then I stopped looking. They are not rare at all.

And here's a shot of speakers that I put up on the Eden forum for Uriah Duffy (Whitesnake) when he was trying to sell them back when the Eden forum was still around. It's a mix of both Eden in-house and Eden by Eminence speakers. They are all 10" speakers and they come in 8Ω, 16Ω, and 32Ω.

 

[Raoul_Duke]

So buy a lower powered amp or a four ohm cab? Honestly, watts are so cheap right now that you might as well get an amp capable of pushing two cabs even if you feel like you won’t need to. Using multiple speakers has advantages outside of volume.

 

[agedhorse]

Subway cabinet’s maximum SPL is calculated based on RMS thermal power rating and average sensitivity from 50Hz-5kHz because a typical bass guitar signal is comprised of ~50% fundamental and 50% harmonics.

The mechanical power ratings apply to single frequencies across the specified spectrum. Most companies do not provide this data, but it was asked for by TB members so I expanded it with the hopes that others would follow our example… which they didn’t.

It takes a fair amount of time to generate this data, it’s useful data to the knowledgeable user. Many speaker’s mechanical power handling is as low as 50% of the thermal power handling, which may explain at least some of the reluctance.

 

[Tim Skaggs]

The 3dB rule is a standard assumption in audio work.

The key word is "clearly"

Under controlled circumstances perhaps you can hear a 1dB change, or even less. Probably not in the middle of a loud band stand.

No idea how accurate this is, but here's a test for you:
Blind Testing a 1 dB Level Difference (audiocheck.net)

How to take the test:
Select the dB difference for the test at the top, left of the page (Click a link next to the heading "Change the target here". Click the buttons under "Files being tested" so you can hear the examples.

Scroll down to the "Test" heading and click the question mark on the left.

I got 9/10 at 1db, but I had to put in both earbuds and listen to the tone a few times to detect the change. That’s an interesting site to compare changes in sound levels. I definitely couldn’t detect changes of any less than 1db, and doubt I could even detect the 1db change in a noisy environment.

 

[Killing Floor]

Ohms and Watts aren’t units of sound pressure. Easy to make that assumption.