Bass cab 4ohm vs 8 ohm

[nitro bass]

Hi and happy new year to everyone.Would anyone here explain to me what differences are between four and eight ohms cabinets with same 350 watts range?I mean-some of them would sound louder,any sound quality "drop" and etc?Talk for Peavey 410 TVX for my Tour 450 head and just to mention that not intend to buy second cab.Any explanation will help.Thank you very much

[jeremy c]

A 4 ohm cab will pull more watts out of your amp and therefore will be a little louder.

 

However, if you use two 4 ohm cabs, you might blow up your amp.

 

If you're going to get two cabs, they should both be 8 ohms.

 

Someone else will give you a more scientific explanation, or you can go study the relationships of ohms to watts and how to add ohms together.

[The Geoff]

The tour 450 puts out a max. of 450W into 4 Ohms. You'd be better with an 8 Ohm cab (4x10) - you'll get a bigger increase in perceived loudness by adding a 2nd 8 Ohm cab than by using a 4 Ohm cab solo.

 

Yes, you could use a 4 Ohm cab, but it leaves you nowhere to go if you later decide you need more.

 

The Tour will deliver between 250 - 300W into a 4x10 8 Ohm & many gig with this kind of power/rig quite happily.

 

http://forums.peavey.com/viewtopic.php?f=20&t=3196

 

G.

[lug]

If you are sure you won't use a second cab, 4 ohm is fine. If there is a chance of a second cab, 8 ohm will serve you better. The sound level difference is just a bit noticable but not overwhelming. As said above, adding a 2nd 8 ohm cab would yield a very noticable difference (+6dB in theory). Tonewise, you shouldn't notice any real difference.

[jcadmus]

However, if you use two 4 ohm cabs, you might blow up your amp.

Unless your amp is rated to run at 2 ohms. My Eden WT550 amp is, and doesn't even breathe hard at 2 ohms. And my previous Peavey T-Max head ran just fine at 2 ohms.

[Tenstrum]

My "full rig" is two 8 ohm and one 4 ohm cabinet. And yes, its incredibly stupid loud.

However, when I play out, I just use the one 4 ohm cabinet as that is plenty because I'm pushing 800 watts into it.

[rumpelstiltskin.]

in most cases, even though a 4O cab will draw more current from the amp, it isn't any louder than an 8O. the whole more power = more loudness thing has very tight limits to its applicability. if you need to play louder (and add low end) you're way better off using two cabinets, and to be sure you're compatible with just about any amplifier on the market, they may as well be 8O. there might be some amps that can source enough current to 2O loads that two 4O cabinets will be noticeably louder than two 8O cabinets, but that's pretty academic. if you're not loud enough with two cabinets, you probably need drastically more power. and roadies. and an entourage.

[TimR]

What you are asking then is whether you should get the 4ohm or 8ohm version cab to go with your head.

 

The head is rated at 500w into 8ohms and 700w into 4ohms.

The cab is rated at 350w RMS 700w peak.

 

Get the 8ohm as you'll not be able to get the full 700w into the 4ohm cab without adding another cab.

[Ross Brown]

This cool... thanks guys... I had the same question.

[rumpelstiltskin.]

What you are asking then is whether you should get the 4ohm or 8ohm version cab to go with your head.

 

The head is rated at 500w into 8ohms and 700w into 4ohms.

The cab is rated at 350w RMS 700w peak.

 

Get the 8ohm as you'll not be able to get the full 700w into the 4ohm cab without adding another cab.

 

disagreed. a 700W amp is *the best* match for that cabinet. a good rule of thumb to follow is take whatever the RMS rating of a cabinet is, and use an amp that is double that power. otherwise you have no hope of fully utilizing the output the cabinet is capable of producing. bass guitar signals are very dynamic and won't come remotely close to 350W RMS if using a 700W amp, even if the 700W amp is truly capable of producing 700W RMS for long periods of time (most aren't).

 

i use a pair of bergantino 112s. they are rated at 300W each. my amp produces 490W into 8O per channel, and they do just fine. no worries.

 

now, since every amp and cabinet are different, and rated differently, it would be a good idea to test the two together before buying, particularly at gig/rehearsal volume. listen carefully for sounds of stress from the cabinet. i do not expect any problems, particularly since peavey rates very conservatively.

 

also, let's clear up how speakers work. the numbers given in the OP are, essentially ,impossible. it's either 350W RMS or it's 700W peak, but it's not both. quick research on the intertubes shows the 700W rating to be "program", which is essentially an amplifier power recommendation. if peavey had given a peak rating, it would probably be 1400W.

 

the way the numbers work in calculating RMS values is that for a sine wave (the test signal used) the RMS value is approximately 70% of the peak value of that waveform. so a 350W RMS signal peaks at 495W instantaneously. now, consider that music signals are way more dynamic than sine waves. (in terms of real science, this is described as crest factor, the ratio of peak level to average level. a sine wave has a 3dB crest factor. most music is 10dB at least, but more likely 12dB. for every 3dB increase in voltage, you double the power, meaning 12dB music has peaks of 8 times the power of the average. so if the peak power is 800W, you can expect the average power to be 100W. for average music. bass guitar has even higher crest factors than that, unless it's heavily distorted and compressed.) basically the dynamic nature of music means that a speaker designed to withstand 350W RMS and 700W peak is very badly designed. it's either way too robust thermally to be a complete POS, or it's not nearly capable of the peak power one might expect a 350W speaker to be capable of withstanding.

 

the meaning of these ratings is based on real physical limitations, but ones that are very different. the RMS rating is a thermal rating. if you exceed the RMS rating, you will melt a voice coil and the speaker will need to be reconed or replaced. the peak rating is based on the maximum excursion (i.e. how far the cone can move) before mechanical failure. if you exceed the peak rating, many different things can happen from tearing the cone or surround to bottoming out the voice coil former on the pole piece in the magnetic gap. the resulting damage may or may not render the speaker completely useless, but it's bad practice nevertheless.

 

so all of that is hand-waving to show that 700W is not the peak rating of the peavey 410TVX, a venerable and very heavy cabinet, and that a 700W amplifier is a perfect match for a 350W RMS cabinet.

 

all that said, though, i'd still get the 8O version. there is really no difference in SPL (sound pressure level, i.e. loudness), and it's more versatile if you want to add another cabinet to your tour 450.

[TimR]

I see the pdf i downloaded had both the 450 and the 700 which confused me. The 450 is 300w into 8ohm and 450w into 4ohm

 

So really he would be better off with the 210tvx into an 8ohm at 175 continuous and 350 program with that amp?

[TimR]

It's also odd the way that cabs and amps are marketed. My amp is 500w into 4ohms. All the marketing pics show it on a 1x15" and 2x10" ministack which according to their specs add up to about 800w. I run it into a single 2x10" rated at 400w. I'm still to get it up to it's limits.

[rumpelstiltskin.]

it's always helpful to remember signal flow. the bass provides a small signal to the amp which provides a large signal to the speaker cabinet. in other words, the rating on a speaker is about what it can handle, not necessarily what it will draw.

 

in my previous post i stated that a 700W amp is the *ideal* match for a 350W RMS (700W program) speaker cabinet. however, amps with less output power than that (e.g. the tour 450 at 300W) can still drive such a cabinet perfectly well. it won't be able to wring every last drop of capability out of the cabinet, but if it's loud enough for your needs, there really isn't a problem with that. you can also exceed the 700W "suggestion", but there is a very real possibility you could exceed the peak rating and cause severe, perhaps irreversible damage. but used judiciously, there really isn't a problem.

 

amps are marketed to sell stuff. of course they picture it on a full stack, so that your image of a "proper" bass amp is a full stack, and not the 210 that is perfectly suited to your needs. the OP may well need the extra SPL a 410 can produce (all other things being equal) over a 210.

 

i'll sum it up thusly: the best match is the cabinet that meets his tone and loudness needs without being blown up by his amp.

[TimR]

So the next question to ask is:

 

Is the 210 as loud as the 410 with the same amp settings and same bass. Do we get "free" volume purely from having more drivers in the same cab? or would we still need to turn the amp up to get more volume? Essentially does adding more drivers only allow us to get louder if we turn up or does this happen due to the mechanical properties.

[rumpelstiltskin.]

Is the 210 as loud as the 410 with the same amp settings and same bass.

 

no.

 

Do we get "free" volume purely from having more drivers in the same cab?

 

no. it's bigger, heavier, and costs more.

 

Essentially does adding more drivers only allow us to get louder if we turn up or does this happen due to the mechanical properties.

 

adding drivers increases SPL (volume) without increasing power output from the amp (turning up). this is physics. you will always get louder from adding another cabinet than by drawing more power from the amp by using a lower Ohm-rated load (i.e. 4O instead of 8O).

[_Sweet Willie_]

ohms and watts and SPL and cabinet matching, oh my!

 

it seems like this topic comes up regularly (maybe more often than any other technical question), and often rumplestizzy and others reiterate things that they've posted before. it makes me wonder if one of those older threads should be elevated as a sticky with a clear title like "ohms, watts, and amp/cabinet matching." these are important things for us to know about, and the basic concepts aren't too hard to wrap one's head around. other topics within that proposed sticky thread might include parallel vs series wiring and what happens to resistance when combining cabs of various "ohmages," and other amp specs that might be of interest to us (e.g., damping).

 

just a thought. perhaps i'm wrong, but in my time here, i think this particular topic has come up regularly and frequently enough that such a sticky might be valuable. i'm also sensitive to the slippery slope of too many sticky threads crowding out the "live" or current discussion threads...

 

peace.

--sw

 

ps: oxymorons can be exciting.

 

 

[TimR]

Except every 4 or 8ohm thread is different. I quite like them. Not everyone takes the time to read the question being asked before chiming in. (or even to fully read the pdfs )

 

This one is specifically asking about what 4x10s should go with a particular amp. The answer isn't as straight forward as "The 8ohm one". It never is.

 

Often its the first question someone new to the forum asks and I think its quite a good way to get introduced into how everything works than trying to wade through pages of stuff. After all ask a direct question and someone eventually should give you a direct (and possibly correct, for you) answer.

[Ross Brown]

ohms and watts and SPL and cabinet matching, oh my!

 

it seems like this topic comes up regularly (maybe more often than any other technical question), and often rumplestizzy and others reiterate things that they've posted before. it makes me wonder if one of those older threads should be elevated as a sticky with a clear title like "ohms, watts, and amp/cabinet matching." these are important things for us to know about, and the basic concepts aren't too hard to wrap one's head around. other topics within that proposed sticky thread might include parallel vs series wiring and what happens to resistance when combining cabs of various "ohmages," and other amp specs that might be of interest to us (e.g., damping).

 

just a thought. perhaps i'm wrong, but in my time here, i think this particular topic has come up regularly and frequently enough that such a sticky might be valuable. i'm also sensitive to the slippery slope of too many sticky threads crowding out the "live" or current discussion threads...

 

peace.

--sw

 

ps: oxymorons can be exciting.

 

 

You're an oxymoron....

[_Sweet Willie_]

Except every 4 or 8ohm thread is different. I quite like them. Not everyone takes the time to read the question being asked before chiming in. (or even to fully read the pdfs )

 

This one is specifically asking about what 4x10s should go with a particular amp. The answer isn't as straight forward as "The 8ohm one". It never is.

 

Often its the first question someone new to the forum asks and I think its quite a good way to get introduced into how everything works than trying to wade through pages of stuff. After all ask a direct question and someone eventually should give you a direct (and possibly correct, for you) answer.

 

Fair points, indeed. I guess I didn't mean to suggest that we try to eliminate these threads from existence, but rather that there does seem to be a set of basic information that would be at the very least a useful reference. In such a case, discussion could still go on, but information could be linked to or pasted from such a reference thread.

 

Peace.

--SW

 

[rumpelstiltskin.]

i might start working on that again. since i'm an engineer, it might be a little math heavy. but i think i can explain it in layman's, too.

[TimR]

Alex's site has a very good section on practically everything:

 

http://barefacedbass.com/technical-information.htm

[nitro bass]

Thank you for your answers.I have ordered TVX 410 8 ohm.Thanks god i have found company to send to my this cab abroad.At first i had option for same can but four ohm and that is why posted this tread.Thank for your help

[rumpelstiltskin.]

did you order a roadie, or at least a wheeled cart, with your TVX? those weigh like 110 pounds. they're made of MDF, which sounds really good and is really heavy. the newer stuff like the IPR notwithstanding, this is what peavey is famous for:

 

http://img703.imageshack.us/img703/3285/satirelogo.jpg