Stereo or 2.1 - Which produces better bass punch?

[xitronics]

Hello everyone,


I had successfully designed and built my first 30+30W RMS amplifier about a year and a half ago with the conventional architecture consisting of Diff Amp - Voltage Divider - Driver Stage - Output (Class AB) and Global Feedback. Now I am looking to built something more powerful, let say, around 120-150W RMS in total output.

In the stereo design, I noticed a phenomenon in which the low frequency beats get canceled out to some extent in some parts of the room even when the polarity for both speakers is set correct. I don't know much about acoustics, but I presumed that the multiple sources of sound(2 speakers in this case) create some kind of an interference pattern which is destructive for low frequencies at some locations in the surrounding space.

My question is, should I go for a 2.1 channel amp with a hi-power sub-woofer amplifier to reduce this effect in my next design?

Also I am little curious to know as to why this canceling out thing becomes evident particularly in the low frequency spectrum.

Thanks,
Prasanna (Prax)

[h_a]

Hi,

that's the usual room acoustics problem.

In every air filled space resonances occur, at which frequencies depends on the shape of the room (the typical box type room being the worst type) and on its dimensions.

As bass is usually recorded as mono (due to human perception of bass), a 2.1 system will not improve that.

You can try to dampen your room acoustically, like add carpets, book shelves, curtains.

The more the merrier

Have fun, Hannes

EDIT: forgot, changing the position of the speakers can also help!

[Mr Evil]

Having a separate subwoofer can help with that, because you have more freedom in where you place it. I don't think you can definitively say that one way is better than the other though.

[xitronics]

Originally posted by h_a
Hi,

that's the usual room acoustics problem.

As bass is usually recorded as mono (due to human perception of bass), a 2.1 system will not improve that.

EDIT: forgot, changing the position of the speakers can also help!

Thanks.

But wouldn't two speakers producing the same monophonic audio from two different positions introduce more directionality than a single sub-woofer banging at the same relative power?

- Prax

[AndrewT]

I have not tried it, but there is a multitude of opinion on this Forum that says that distributed bass drivers have a better chance of sounding right/better than a single or even two bass speaker set up.

If 2.1 were to follow this route then one bass speaker reproducing the 0.1 bandwidth is the wrong way to go.
Maybe 4off 8inch drivers/boxes, each with their own amplifier spread around the room may give a better sound than a 2.0 (stereo) system.
Rather than mid/top satellite pair + one 15inch bass speaker.

This would be an ideal candidate for 6off chipamp monoblocks in tiny chassis.

[Wavebourn]

I prefer 2.2, since live recordings capture phase shifts on lows that add to perception of reality.

[h_a]

Originally posted by xitronics



Thanks.

But wouldn't two speakers producing the same monophonic audio from two different positions introduce more directionality than a single sub-woofer banging at the same relative power?

- Prax

Directionality is not a matter of the number of speakers, but of the music. 2 speakers have the advantage that they power different room modes (resonances), so in average that should give a more consistent bass in the room. Of course using even more speakers improves that to a point of diminishing returns, but is not really practical (equalisation necessary).

Still, it's easier to dampen the room, although that's not to everybody's taste.

Have fun, Hannes

[Melon Head]

I am a bass player and have never heard a 2.1 system that sounded better than a proper stereo set up.
So I agree with Andrew.
Have you ever listened to a subwoofer on its own?
Most sound absolutely crap. Why would you want to add that crap to your music.
The correct way is to start with really good stereo speakers, capable of the frequencies you need (Scanspeak 18W/8545 drivers are one of my favourite drivers for bass) , and amplifier with reasonable amount of damping factor, as well as power output.
Bass notes love powerfull amplifiers.

Edit: Just one other observation. Speakers with multiple bass drivers (eg 5" to 6") sound much more punchy than speakers with single bass drivers (regardless of size). That is it is better to have 2 x 6" drivers as opposed to a single 8" driver.
There are also other factors, cabinet alignment (box volume and port length) for vented cabinets or using sealed cabinets. All of this affects the bass performance.
There is much more than this also, but the things I have mentioned are the things that I have found in my experience make the most improvement.

[AndrewT]

Originally posted by thanh1973
Bass notes love powerfull amplifiers.

not the way I play my system.
The bass speaker gets about a quarter of the power input that is supplied to each satellite.
When I turn off the satellites, the bass is hardly audible.
When I turn off the bass and listen to just the satellites a lot is missing.

[Melon Head]

Hi Andrew
It sounds like you are using bi-amping, is that correct?

I should elaborate a bit further about power rating. Most of my experience relates directly to instrument amplification and speaker cabinets, although I have found the same rules seem to apply to stereo amplification.
When I first started out playing bass guitar (over 15 years now) I got myself a Fender Jazz guitar. I didn't know anything about amplification or speaker cabinets at that time. So I had a look at what my friend used (a guitarist). From memory it was 60W Messaboogie combo with a 10" driver.
Well I thought, I am a bass player so I need a big woofer right and if I can afford 100W then I am set.
Well I ended up buying a Fender BXR 100 (a 100W combo with a 15" woofer). Sure this thing played loud (loud enough to cause permanent hearing loss) but I found it lacked tone and punch, basically it was lifeless. I became confused and disillusioned why I couldn't reproduce the tone and punch of other bass players. I tried different EQ settings and affects peddles but nothing helped.
6 months later I walked back into the bass shop not happy, thinking it must be the guitar. I thought maybe I should buy a Musicman bass guitar. So I asked the guy in the shop if I could compare a Musicman to a Fender Jazz. I told the guy I had a Fender BXR 100 combo amp and would like to use that to make a fair comparison. Unfortunately he had sold out of the BXR 100 but he had a BXR 300 (exactly the same amp but with 300W of power). Anyway I plugged in the Musicman and started playing, my immediate impression was this sounds fantastic, alright I was sold. I was just about to trade in my guitar, but I thought to be fair I should play the Fender Jazz through the same amp. So I went ahead and played and then the bomb shell fell, the bloody Fender Jazz also sounds fantastic. What is going on. I asked the guy if he had any other amps with 100W power rating. Every 100W amp I played sounded crap in comparison to the 300W, and I am talking about playing at very quiet levels (much more quiet than you would listen to a cd).
I could go on but to cut to the chase after 15 years of trying out over 50 different amps and cabinets, I have come to the following conclusions:
- a 2 x 10" sounds better than a single 15" (ie multiple drivers over single drivers),
- and 300W or 400W amp sounds much better than a 100W amp.
And finally my favourite bass amps are the Trace Elliot AH500-12 hybrid (2 of the gain stages uses valves, mosfets at the output) amp the other is an Eden WT 550. These are 500W amps.
I mainly play jazz style music so I don't need 500W for the volume. I could probably get away with 40W and still I have ampple headroom in terms of volume but I challenge anyone to find one that sounds as good as the two mentioned above.

To sum up I am not saying you need 300W for your stereo set up (40W is probably adequate), but big powerfull transformers improve things quite substantially, so don't skimp in this area.

I realise there are so many other factors. But all things being equal these rules seem to be consistant.