Advice on Amp vs lower ohm speakers

[Paul Curtis]

Hi All,

So not an expert and I've just replaced all the speakers on a base audio X1 with Audison, with new tweeter pillars as well. The difference is night and day so very happy.

I'm still using the base head unit. I do have an audison amp as well which I have not installed yet because that looks like a huge job to me. So I'm thinking the improvement in audio is excellent as it is BUT there's not so much on an improvement in bass. This comes from underseat woofers which were changed from awful 6" versions to the audison 8" replacements.

I went for the 4 ohm versions because original they were going to be driven by bridged outputs from the amp, that would match the ratings.

But if I swapped these for 2 ohm versions would the difference in loudness be noticeable to the point where maybe I don't need the amp?

It's really difficult for me to tell because I can't compare. Perhaps the amp will just drive everything better plus I get the DSP tuning and all of that. So perhaps it's better to bite the bullet and install but a little part of me is... well is it worth it....

So any advice or opinion really appreciated,

thanks
Paul

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[Doxquzme Premium Member]

Hi All,

So not an expert and I've just replaced all the speakers on a base audio X1 with Audison, with new tweeter pillars as well. The difference is night and day so very happy.

I'm still using the base head unit. I do have an audison amp as well which I have not installed yet because that looks like a huge job to me. So I'm thinking the improvement in audio is excellent as it is BUT there's not so much on an improvement in bass. This comes from underseat woofers which were changed from awful 6" versions to the audison 8" replacements.

I went for the 4 ohm versions because original they were going to be driven by bridged outputs from the amp, that would match the ratings.

But if I swapped these for 2 ohm versions would the difference in loudness be noticeable to the point where maybe I don't need the amp?

It's really difficult for me to tell because I can't compare. Perhaps the amp will just drive everything better plus I get the DSP tuning and all of that. So perhaps it's better to bite the bullet and install but a little part of me is... well is it worth it....

So any advice or opinion really appreciated,

thanks
Paul

All things considered equal (same woofers make model and size), the theoretical difference is going to be 3 db (roughly 33% difference in volume) if dropping to the 2 ohm load makes the amp put out twice the power at 2 ohms than it did at 4 ohms. Since we're not talking about efficiency and essentially talking about more wattage either way. The ear perceives a doubling of the volume at around 9-10 db. In relationship to power, all things considered equal, an 8 to 1 ratio of increased wattage works as follows.

100 watts to 200 watts - +3 db (+33% in vol)
200 watts to 400 watts - another +3 db (total of 6 db or +66% in vol)
400 watts to 800 watts - another +3 db (total of 9 db or +99% in vol) or roughly a doubling of the perceived volume to the ear.

Important to note: Low impedance drivers don't play louder, the offer less resistance to the amp which in turn extracts more wattage from the amp (the amp must be rated stable at these lower impedances). The volume increase comes from the amp putting out more power.

When is comes to bass, wattage is king. Woofers are larger, heavier electric motors and they use power to function, lots of it relatively speaker-ing.

 

[Paul Curtis]

When is comes to bass, wattage is king. Woofers are larger, heavier electric motors and they use power to function, lots of it relatively speaker-ing.

Really appreciate the response.

So it sounds like really the amp will be the best next step. I don't know whether the head unit of this BMW would be rated to drive the woofers at 2 ohm. And in fact the signal is split at the woofer side with some dodgy cross over to the mids in the door and tweeters - so that power is spread even more.

One of the benefits of the amp is to drive these separately.

I have a feeling that the head is 25w and the amp is 8 x 65w, the speakers are rated at 150w. So bridging the amp gives 130w per underseat and that would be plenty... I hope..

Now to find some sample installs so I can learn!

thanks
Paul

 

[Doxquzme Premium Member]

Really appreciate the response.

So it sounds like really the amp will be the best next step. I don't know whether the head unit of this BMW would be rated to drive the woofers at 2 ohm. And in fact the signal is split at the woofer side with some dodgy cross over to the mids in the door and tweeters - so that power is spread even more.

One of the benefits of the amp is to drive these separately.

I have a feeling that the head is 25w and the amp is 8 x 65w, the speakers are rated at 150w. So bridging the amp gives 130w per underseat and that would be plenty... I hope..

Now to find some sample installs so I can learn!

thanks
Paul

The HU us likley 12-15 x 4 at best so yes, using an amp will be hugely beneficial, night and day. The HU us not going to drive a sub to any satisfaction levels at all.

 

[chipss36]

Lowering the impedance will also lower the speakers motor control, or damping, in physics no free lunch exists.
It’s all give and take.

 

[3toneEYZ]

Lowering the impedance will also lower the speakers motor control, or damping, in physics no free lunch exists.
It’s all give and take.

It also lowers the amps efficiency and raises the current draw.