Impedances

[mildmanofrock]

Hi there, can anyone help?

I currently have an:

* Ampeg SVT-6 Pro amp (with an output power rating of 1100 Watts RMS, 4 ohm load, 120VAC, 5% THD, and
750 Watts RMS, 8 ohm load, 120VAC, 5% THD - I copied and pasted this from the brochure)
* Ampeg SVT-410 HLF speaker cabinet (4 ohms impedance).

I'd like to add a bit more bottom-end welly to my sound. So, I thought about getting an Ampeg 1x15 speaker. However, the impedance on these in 8 ohms - which is different to my 4 ohms SVT-410 HLF.

Could I use an 8 ohms Ampeg 1x15 with my 4 ohms SVT-410 HLF speaker? Or does my choice of second speaker also have to be 4 ohms? If so, I was thinking about getting another SVT-410 HLF to make the most of my amp. Or is there a better speaker cabinet for getting some trouser-flapping rumble?

Thanks for your help folks - much appreciated.

Steve

Edited March 17, 2009 by mildmanofrock

[Paul_C]

[quote name='mildmanofrock' post='437065' date='Mar 17 2009, 11:45 AM']Hi there, can anyone help?

I currently have an:

* Ampeg SVT-6 Pro amp (with an output power rating of 1100 Watts RMS, 4 ohm load, 120VAC, 5% THD, and
750 Watts RMS, 8 ohm load, 120VAC, 5% THD - I copied and pasted this from the brochure)
* Ampeg SVT-410 HLF speaker cabinet (4 ohms impedance).

I'd like to add a bit more bottom-end welly to my sound. So, I thought about getting an Ampeg 1x15 speaker. However, the impedance on these in 8 ohms - which is different to my 4 ohms SVT-410 HLF.

Could I use an 8 ohms Ampeg 1x15 with my 4 ohms SVT-410 HLF speaker? Or does my choice of second speaker also have to be 4 ohms? If so, I was thinking about getting another SVT-410 HLF to make the most of my amp. Or is there a better speaker cabinet for getting some trouser-flapping rumble?

Thanks for your help folks - much appreciated.

Steve[/quote]

the way cabs are usually wired, you'd need 2 x 8ohm cabs to replace 1 x 4ohm cab - if you run a 4 and an 8 you'll dip below 4 ohms and risk blowing things up (assuming the limit is 4ohm)

[obbm]

[quote name='mildmanofrock' post='437065' date='Mar 17 2009, 11:45 AM']Hi there, can anyone help?

I currently have an:

* Ampeg SVT-6 Pro amp (with an output power rating of 1100 Watts RMS, 4 ohm load, 120VAC, 5% THD, and
750 Watts RMS, 8 ohm load, 120VAC, 5% THD - I copied and pasted this from the brochure)
* Ampeg SVT-410 HLF speaker cabinet (4 ohms impedance).

I'd like to add a bit more bottom-end welly to my sound. So, I thought about getting an Ampeg 1x15 speaker. However, the impedance on these in 8 ohms - which is different to my 4 ohms SVT-410 HLF.

Could I use an 8 ohms Ampeg 1x15 with my 4 ohms SVT-410 HLF speaker? Or does my choice of second speaker also have to be 4 ohms? If so, I was thinking about getting another SVT-410 HLF to make the most of my amp. Or is there a better speaker cabinet for getting some trouser-flapping rumble?

Thanks for your help folks - much appreciated.

Steve[/quote]

The minimum impedance you can present to your amp is 4-ohms. If you use an 8-ohm cab with your existing 4-ohm cab the total impednace will be 2.66-ohms which will blow the amp.

If you want two cabs then they must both be 8-ohms.

I'm sure this is all explained in the Wiki.

Edited March 17, 2009 by obbm

[chris_b]

You can't add any more speakers. You are at the 4 ohm limit of your amp.

[chris_b]

The spec for your cab is

LF Drivers: 4 x 10” Cast Speakers
Voice Coil: 2.5”
Magnet Weight: 56 oz
HF Driver: Horn/Driver
Voice Coil: 1”
Magnet Weight: 8 oz
RMS Power Handling: 600-Watts
Frequency Response (-3dB): 33Hz - 18kHz
Usable Low Frequency (-10dB): 29Hz
Crossover Frequency: 4kHz
Nominal Impedance: 4-Ohms
Sensitivity: 96dB
Maximum SPL: 124dB
Dimensions (W x H x D inches): 26.25 x 30.75 x 18.75
Weight: 128 Pounds

How are you NOT getting enough bass out of that rig? You must be able to dial more bottom end?

[mildmanofrock]

Thanks for your help folks.

Like you say, the answers are probably elsewhere, but I find some of the explanations a bit tricky for my addled brain - this is really clear though, thanks.

I know the cab's specification is pretty good but it just seems to lack bottom-end sometimes. Tis a shame I can't add another speaker - it looks like I'll either have to stick with what I've got or sell the speaker and buy a couple of 8ohms cabinets.

Cheers!

Steve

[Paul_C]

[quote name='mildmanofrock' post='437103' date='Mar 17 2009, 12:19 PM']Thanks for your help folks.

Like you say, the answers are probably elsewhere, but I find some of the explanations a bit tricky for my addled brain - this is really clear though, thanks.

I know the cab's specification is pretty good but it just seems to lack bottom-end sometimes. Tis a shame I can't add another speaker - it looks like I'll either have to stick with what I've got or sell the speaker and buy a couple of 8ohms cabinets.

Cheers!

Steve[/quote]

Two things you could try:

one, experiment with placement - close to a wall (and in the corner of a room) will make a difference.

two, get someone else to play through your rig and stand back and listen - quite often what sounds poor to you will turn out to be much different to those further away.

[mildmanofrock]

[quote name='Paul_C' post='437121' date='Mar 17 2009, 12:29 PM']Two things you could try:

one, experiment with placement - close to a wall (and in the corner of a room) will make a difference.

two, get someone else to play through your rig and stand back and listen - quite often what sounds poor to you will turn out to be much different to those further away.[/quote]

Thanks Paul, I'll give that a try.

Steve