Multiple Small Subs - Geddes Approach

[mat02ah]

Originally posted by markus76

I was talking about max. SPL, as shown here:

[gedlee]

You guys seem to be very defensive about your "local" products.

This speaker, to me, is classic in that all efficiency seems to be sacrificed for extended LF response. Exactly what I don't do. The LF extension is very good for an 8" loudspeaker, but the MAX SPL indicates that this extension is not very useful as it comes with a lot of nonlinearity (and I'm not saying that this is audible only that the VC is obviously coming out of the gap at medium SPL levels). It would be difficult for me to use this speaker in any of my applications. As a near field monitor, which it was probably designed for, it would be OK, but not in a home situation. You would have to HP filter this speaker to get any kind of SPL level in a listening room. But then all that work to extend the LF would be wasted - you'd end up with low efficiency AND no LF extension.

I am not sure who you are trying to impress with the axial frequency response. With an active system thats a no-brainer, but also not that important. And the price! Wow!

[markus76]

Thomas, I wasn't aware of the very low max. SPL at low frequencies. You have to take the frequency response into account as Earl already pointed out. That's why I posted the diagram. The O300 is one of the best nearfield monitors on the market. But it's exactly that - a nearfield studio monitor. Most people think that nearfield is 2 m or more. That's incorrect. In a studio a nearfield monitor is placed much nearer. And that's what the O300 is designed for. Hope you don't use it otherwise.

Best, Markus

[mat02ah]

Originally posted by gedlee
You guys seem to be very defensive about your "local" products.

I am not defending anything or anyone.

Originally posted by gedlee
You would have to HP filter this speaker to get any kind of SPL level in a listening room.

So we agree on that. Fine. "Any kind of level" of course depends on the room, your preferences, the neighbours ...

Originally posted by gedlee
I am not sure who you are trying to impress with the axial frequency response. With an active system thats a no-brainer, but also not that important. And the price! Wow!

I am also not trying to impress anyone. K+H presents lots of other data, much more data than you present.

Originally posted by gedlee And the price! Wow!

They are selling complete, active loudspeakers that work out of the box. Not a kit.

To summarize: The "Geddes approach to multi-sub placement" is not very suitable for small speakers with some LF-extension. You'd have to HP filter them and "waste" their LF-extension. You need "big" mains with some LF extension and high SPL capability for this approach. That's pretty much the answer I expected.

Regards

Thomas

[markus76]

Thomas, you sound rude. The "Geddes approach to multi-sub placement" works even with your speakers, but it can't compensate for the limited level capabilities of the O300 at low frequencies. They will produce a lot of distortion at low frequencies with or without multiple subs.
If you look at Klein + Hummels subs then you'll find that they use a high pass exactly as Earl suggested.

Best, Markus

[mat02ah]

Originally posted by markus76
Thomas, I wasn't aware of the very low max. SPL at low frequencies.

I was. What kind of miracle do you expect from a 8" woofer in a closed box?

Originally posted by markus76
Most people think that nearfield is 2 m or more. That's incorrect. In a studio a nearfield monitor is placed much nearer. And that's what the O300 is designed for. Hope you don't use it otherwise.

Quote from the K+H O300(d) manual:

Most Common Application: Near-field monitoring
Minimum Distance: 0.75 m (2.5’)
Recommended Distance:1.0 – 2.5 m (3’ - 8’)
Maximum Distance: 6 m (18’)

Regards,
Thomas

[markus76]

What are you trying to prove? It depends on your level requirements (and in a nearfield situation on the dispersion). You can even place them at 10 m distance if you don't want to play them loud. You have to decide for yourself how much distortion you allow for.
I'll repeat: If you look at Klein + Hummels own subs then you'll find that they use a high pass exactly as Earl suggested.

[gedlee]

Originally posted by mat02ah

To summarize: The "Geddes approach to multi-sub placement" is not very suitable for small speakers with some LF-extension. You'd have to HP filter them and "waste" their LF-extension. You need "big" mains with some LF extension and high SPL capability for this approach. That's pretty much the answer I expected.

Regards

Thomas

I would say it this way:

"The Geddes approach requires a total system design which encompasses the room, multiple subs and mains wherein each subsystem is optimized to work as a whole."

What you are asking is how to "modify" a subsystem that was not designed to work with multiple subs. As Markus points out you can do that, but it will be less effective than if you had taken a full systems approach which would have not have sacrificed efficiency to extend the LF response.

The Abbeys, assembled, sell for far less than the K&H system. Performance of the Abbeys is hands down better than what you have shown.

[mat02ah]

Originally posted by markus76
I'll repeat: If you look at Klein + Hummels own subs then you'll find that they use a high pass exactly as Earl suggested.

You "repeat"? Funny ... We started this discussion in a german forum (casakustik.de) where you repeatedly stated that HP filters are not needed, because you didn't think of limited SPL. Now we seem to agree that some filtering is needed. Were's the problem?

Thomas

[mat02ah]

Originally posted by gedlee
"The Geddes approach requires a total system design which encompasses the room, multiple subs and mains wherein each subsystem is optimized to work as a whole."

That's what I thought, too. Markus presents this method on his website as being more universal.

Originally posted by gedlee
What you are asking is how to "modify" a subsystem that was not designed to work with multiple subs.

I am not thinking about modifying a subsytem, I am thinking about adding subs to existing O300 speakers.

Originally posted by gedlee
The Abbeys, assembled, sell for far less than the K&H system. Performance of the Abbeys is hands down better than what you have shown.

Abbeys, assembled, per speaker, without power amps: $1600+shipping+~5%duty+19 % tax=$2046=EUR1530

O300 with power amps and two years warranty:
~EUR1850, shipping and taxes included.

That's not really "far less".

It was not my intention to discuss all this. I simply wanted to find out how to make a 'Geddes multiple sub setup' with small speakers. So the answer is:

(i) You don't need HP filters to make the principle work but

(ii) if you want more SPL you will need HP filters.

I was sure about (ii) but not sure about (i).

Thomas