Ohms, Subs and amps ????

[ppentertainments]

Currently using active subs to negate the need to know the answer to these questions, but out of curiosity can anyone answer the following :
1. Using 2 subs and 2 tops both rated 8 ohms - what ohm rating is being used from the amp - 8 or 4 ??
2. Using 2 subs and 2 tops. Subs rated 4 ohms and tops 8 ohms. What ohm rating is fed into the tops and what is being used from the amp ??

Just curious as when looking at packages from various online stores I often feel the amp is not powerful enough to power the system advertised.

Might be a totally stupid question but someone has to ask

[Excalibur]

Currently using active subs to negate the need to know the answer to these questions, but out of curiosity can anyone answer the following :
1. Using 2 subs and 2 tops both rated 8 ohms - what ohm rating is being used from the amp - 8 or 4 ??
2. Using 2 subs and 2 tops. Subs rated 4 ohms and tops 8 ohms. What ohm rating is fed into the tops and what is being used from the amp ??

Just curious as when looking at packages from various online stores I often feel the amp is not powerful enough to power the system advertised.

Might be a totally stupid question but someone has to ask

Assuming in both cases that the tops are fed from the hi-out on the subs, according to Peavey, who I asked this question a while ago, regard the two separate boxes as one multi way enclosure, with the impedance governed by that of the sub.

[CRAZY K]

Assuming in both cases that the tops are fed from the hi-out on the subs, according to Peavey, who I asked this question a while ago, regard the two separate boxes as one multi way enclosure, with the impedance governed by that of the sub.

That is true Peter as we know, but possibly other makes dont have the Peavey High Filter gizmo?

That Class D bass speaker I was looking at that you own--- CD15N 8 ohms just has a speakon in /out. ( I think)

The best way as ever is to use matched equipment from the same manufacturer.

Having said that I have shot myself in the foot as im currently trying to find a single unpowered bass sub match for my 2 Peavey tops--as sometimes the two matched Peavey Subs are a bit of a problem in certain premises with access by stairs resembling the face of the Eiger.

I have looked at Spins powered DB ( thanks Matt) but it might be a bit heavier than I wanted and of course pricey.

The Class D passive small sub looks the ideal weight and price---well it will be if Peter can work out how I match it

According to Tony B who seems to know what hes talking about the 8ohm and 4 ohm together on one channel would give 2.67 ohms--not advisable.

CRAZY K

[DJ Jules]

Assuming in both cases that the tops are fed from the hi-out on the subs, according to Peavey, who I asked this question a while ago, regard the two separate boxes as one multi way enclosure, with the impedance governed by that of the sub.

The theory goes that if you have a high/low pass filter then as the pitch of the music rises you stop driving the sub, and start driving the mid-range speaker, meaning you never load the Amp with both speakers at once. This relies on you either using an external passive crossover which ensures both speakers aren't loading the amp at once, well matched speakers with internal hi/low pass filters, or driving the tops off a filtered output from the bass bins (effectively the same as the driving using an external crossover, it's just built into the bass bins).

If both subs and tops are rated at 8ohms then you don't risk overloading the amp anyway if you use poorly matched speakers (the worst that will happen is you'll get an odd bump in the whole systems response as you'll be driving both tops and subs at certain frequencies), but if you're using 4 + 8ohms or 4 + 4ohms, then you could conceivably damage your amp.

Hope that helps,

Julian

[ppentertainments]

BUMP - any more opinions as keep getting different answers, even from DJ/Speaker suppliers.

[TonyB]

Thats probably because there is no single answer - it depends on how the bass bins are designed. Some are designed so that, for example, adding 4 Ohm tops to 4 Ohm bass bins, the amp will still see 4 Ohms. Like wise 8 Ohm bins + 8 ohms tops the amp will still see 8 Ohms. Some are designed so that 8 ohm tops + 8 ohms bins, the amp will see 4 ohms. Whatever bass bins you use, you will have to either check the manual or the suppliers/manufactures for the particular make/model.

[ppentertainments]

Thats probably because there is no single answer - it depends on how the bass bins are designed. Some are designed so that, for example, adding 4 Ohm tops to 4 Ohm bass bins, the amp will still see 4 Ohms. Like wise 8 Ohm bins + 8 ohms tops the amp will still see 8 Ohms. Some are designed so that 8 ohm tops + 8 ohms bins, the amp will see 4 ohms. Whatever bass bins you use, you will have to either check the manual or the suppliers/manufactures for the particular make/model.

Cheers Tony, that seems the most logical answer. I am suprised at the lack of answers to this.

[Danno13]

Cheers Tony, that seems the most logical answer. I am suprised at the lack of answers to this.

Without meaning to be rude, it's probably because pretty much the same question is asked at least once a fortnight and people get tired of typing the same answers!

Generally, 2 8ohm boxes in parallel would be 4ohms. Some manufacturers employ some trickery (seeminly just to confuse anyone with basic knowledge of electronics) with alledgedly retains an 8 ohm load to the amp.

Although god knows why you'd want to do this.. as you'll draw more power at 4 ohm, and even budget amps are more than capable of performing reliably at 4 ohms.

My advice would be to stick a multimeter across the cable you'd connect to the amp.. you should get a balpark of what impedance you have (although it would of course only be a resistance, and not entirley accurate when your working with a d.c. meter)

[ppentertainments]

Without meaning to be rude, it's probably because pretty much the same question is asked at least once a fortnight and people get tired of typing the same answers!

I agree, but is a subject which, as far as I am aware has not produced any definitive answer.

[Danno13]

Ok.. definitive answer.. don't mess about with companies who don't stick to standard configs for speakers or risk only taking a single amp out on the road.

Get 8 ohm cabs, 2 bins and 2 tops. 2 amps sufficiently powered for the speakers you're using (ideally 1.8 - 2.4 x the rms rating of said speakers), then an active crossover, and you'd probably want a 6U wheeled rack to house this in.

Don't scrimp, buy the best you can afford from well established and renonwed brands. And of course whatever suits your tastes, or is ideal for your target market, after getting a few demos and reatailers or DJ events.

Wire the tops in stereo, run the sub amp in 4ohm mono brige (You'll have bought a decent amp that can cope with this..)

Keep the same great system for at least the next 10 years! This will of cost you less in the long run and provide a better quality sound that your not always wanting to improve on.