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Matching av bassforsterker og -kabinett


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Denne guiden her, og to andre jeg har postet her, er skrevet av en bruker på Harmony Central sitt bassforum (HCBF), nemlig "Kindness". Han har veldig gode tekniske kunnskaper om både basser og forsterkere, og er en av de største bidragsyterene på HCBF når det gjelder spørsmål/svar om disse temaene.

Er det noe dere lurer på, så er det bare å fyre løs i tråden. Vil dere stille han spørsmål direkte, er det bare å registrere seg på Harmony Central-forumet og sende han en PM der.

Original URL til guiden:

http://acapella.harmony-central.com/forums...d.php?t=2067656

Kindness's Amp/Cabinet Pairing Thread

I receive a lot of private messages asking me about pairing amps and cabinets, some regarding specific pairings and some just looking for general guidance. I also have responded haphazardly to threads and posts where a fellow forum member may mention they are "pushing 3,000 watts into a "Brand X" 4x10. I figured I'd use this thread to consolidate some of what I've written.

First, no thread about amp and cabinet pairings would be complete without a discussion of "underpowering" a cabinet. The short story, there is no such thing as underpowering a cabinet. When someone uses that phrase, you need to question whether the speaker/writer actually understands the subject matter.

Agedhorse's thread in the FAQ regarding speaker failure explains the two mechanisms for speaker failure, both caused by sending too much power to a cabinet. If you haven't already, read and re-read this thread until you understand it. You don't need any technical background to understand the concepts as they are presented, so if you don't understand the entirety of that post, you may want to ask questions about where you are falling off track. Once you understand everything written in that thread, you'll be well equipped in understanding your gear.

Agedhorse's Speaker Failure Thread

Got it? Good.

One of the questions I am asked the most is some variation of this:

"I have "Brand/Model A" amp. What cabinet will handle the "X" watts from my amp?" The real question isn't what cabinet will take the wattage from your head, but which cabinet will produce volume/tone sufficient to meet your needs with your amp. You can have an enormously powerful amp and a cabinet that can't handle much power, but if you are achieving your desired tone and volume everything is just fine, you just might be carrying around more power than you need.

Speaking of more power than you need, what about the guys playing with huge power amps into standard bass cabinet? Does anyone actually use 2,000 watts into a typical 4x10? Nope. No one. There just aren't bass cabinets that can actually handle that much power. Remember from the FAQ post linked above, there are two limits to cabinets, thermal limits and mechanical limits. Nearly every commercial bass cabinet is actually displacement limited (mechanically limited) - not thermally limited. What the heck does this mean? Go back to Agedhorse's post and reread the mechanical limit section. In short, due to the mechanical limits of a cabinet, it is not uncommon for a bass cabinet to start farting out in the bass region at about 1/4 the published thermal rating of the cabinet. Your 1,000 watt 4x10 probably can't handle much more than 200-300 watts below 100 Hz. Crank the volume, boost the bass and bask in the flubbiness. :)

How am I going to know if I am exceeding the cabinet's mechanical limits? If you are listening to your cabinet you should be able to tell when it is farting out and you should dial the amp back. If it sounds good, it is. If you are interested in learning more about these limits, download WinISD and start modeling cabinets. If you have questions about that, post them and I'll help.

Then why do I need a 2,000 watt power amp to get sufficient volume out of my cabinet? Many bass specific preamps are incapable of driving the power amp to full power. Power amps have an "input sensitivity" which is the voltage required to drive the amp to full power. If the preamp cannot output sufficient voltage, you will not be making use of the full power of the amp regardless of volume/gain settings. Thus, if your components aren't well matched (and it is often difficult to even find published specifications to make the determination) you might think you have your 2,000 watt amp on full go, but you might only be driving 200 watts. If you put a mixer or preamp in front of the amp to boost the signal, you might find you've been carrying a lot more reserve power than you expected.

Lots of people want to know what equipment they need to be as loud as they want to be. Many know that doubling the power or doubling the displacement will give you a 3 dB increase in volume. +10 dB is generally accepted as "sounding twice as loud." In order to achieve a +10 dB increase, you need ten times the power or just over eight times the displacement (eight times the displacement is +9 dB). In other words, a 1x12 at 50 watts may be twice as loud as the same 1 x 12 at 5 watts. Similarly, eight of the same 1x12s may be twice as loud at 5 watts as the 1 x 12 at 5 watts. One of the reasons adding speaker displacement is generally a great way to boost volume is that most solid state amps will deliver more power to a lower impedance. Therefore, if you take a typical 1x12 on a solid state amp and add another 1x12, you have both doubled the displacement and (approximately) the power for a +6dB gain. +6 dB isn't double the volume, but it is a noticeable change. The other reason is power compression. Many speakers do not operate linearly within the range of power we use to drive them. In many cases the first 50 watts to the cabinet have a much greater effect than the next 50 watts. When you split the amps power into a greater number of drivers, you reduce the effects of power compression.

Lastly, a little something about sensitivity ratings. I sometimes get asked something like: Cabinet A is 103 dB/w/m and Cabinet B is 99 dB/w/m - this means Cabinet A is louder, right? Well... it means that even if the specs can be trusted that Cabinet A is louder with an input of 1 watt. It doesn't tell you anything about what happens when you turn up. Maybe cabinet A will start farting out at a much lower power level than cabinet B. So even though it takes more power for Cabinet B to get loud, it might be that Cabinet B has a higher maximum output. Then again, maybe not. The point is, those specs are more related to how power hungry a cabinet may be, not how loud the cabinet can get. (In practice they tend to connote how mid oriented a cabinet is. Generally speaking, the higher the sensitivity cabinet will tend to be more mid oriented.)

Hopefully these few short paragraphs are helpful in some way. They are just thoughts off the top of my head based on common questions I get and I would be happy to expand on any of them if anyone has questions.

Håper guiden kan gi folk litt innsikt i hva man må tenke på når man skal finne en fin kombinasjon av forsterker og kabinett.

Igjen, er det noe dere lurer på, så er det bare å fyre løs i tråden. Vil dere stille han spørsmål direkte, er det bare å registrere seg på Harmony Central-forumet og sende han en PM der.

Ta gjerne en titt på en av de andre guidene:

Setup av bass

Fret Leveling

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  • 4 weeks later...
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  • 9 months later...

Noen av dere som har erfaring med Orange bass amps og cabs??

Vurderer å kjøpe meg Orange OBC115 og Orange TB500H, da jeg i dag spiller med en Behringer BX600 (http://www.behringer.com/EN/Products/BX600.aspx) som nå omtrent kun duger til hjemmeøving og skriker om nåde på bandøvingene.

Begynte å spille bass for en tid tilbake, men har aldri satt meg inn i hvordan ting fungerer når det gjelder watt og ohm, dessuten har jeg ikke peiling på hvilke merker som duger i dagens samfunn;)

Spiller forresten i ett rocke band med trommis og gitarister med forsterkere opp til taket, så jeg trenger litt styrke i forsterkeren min sånn at jeg blir hørt;)

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  • 8 months later...
Ganske nybegynder spm, men, jeg har en hartke a100, kan den kobles til et større kabinet (for den er for svak for gigs as we speak) eller burde jeg skaffe meg separat head og kabinet når jeg først skal oppdatere?

Jeg ville oppgradert til separat topp og bunn med en gang. Etter min erfaring kommer man langt med et ålreit 2x10 og en 4-500W forsterker om man har begrenset med penger, så kan man heller bytte ut senere.

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