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In the Forum: Audio Discussions
In the Thread: A quest for a better monitor.
Post Subject: What makes a good monitor?Posted by Romy the Cat on: 6/10/2006

I would like to think a little about the monitors. A monitor is kind of bogus name but useful. I usually call a loudspeaker that is not floor standing as a monitor. Sometime they called bookshelf but I hardly image any loudspeaker on a bookshelf…

In my mind any monitor must not be ported. Reflex-loading is absolutely not acceptable, regardless the theories, design objectives and implementations. Ported design is juts completely wrong sound unless a speaker does not goes down 200-300Hz. It is possible, if the speaker made VERY accurately and very sensible to tune the design that the port would not be destroying Sound. However if it made properly then the speaker will not have the LF benefits from the port and the design will sound almost like open baffle.

A key for a good 2-way monitor is a combination of correct enclosure and correct, properly used bass driver.  This relation between the capacity of the bass driver and the capacity of the monitor’s enclosure could not be understated. Let look at this subject deeper.

There are very few bass drivers that would have correct T/S characteristics in sealed enclosure and in the same time:

1) Perform correct in context of first order filter
2) Have correct tonal performance
3) Do not require any frequency or impedance normalization
4) Have low dynamic compression

The first order filter with no resonance optimization is absolutely mandatory. Let pretend that a monitor has a crossover point somewhere at 3kHz-4kHz it means that the bass driver need to perform correctly at least 1.5-2 octaves higher. The very same driver should handle 150Hz well (75Hz-80Hz in the box), to have high sensitively, maintain the dynamic and transients characteristics across it’s range and be able to deal with the enclosure properly. It is very very very demanding role and it is very very difficult to find such a driver or to make the available drivers to walk. If you did it then 85% of the monitor is done but it is very very difficult.

The same come with the enclosures. It is very very difficult to make the enclosure sensible sounding relative to the given LF driver. Many companies claim some crazy researches and magnificent successes in this area. In reality it is very common that the result it is not as glorious. The Wilson Audio CUB with, a pair of SEAS 6.5" helped-paper woofers, had an expansive composite proprietary and well built enclosure but sonically those enclosures are VERY auditable. I think Wilson shoot itself in foot but going for that foolish LF extension with it’s dummy bass reflex-loading. If the CUB did not do down to 45Hz but were sealed and roll off at 80Hz-90Hz then they might be worth attention. Dunlavy SM-1 were very properly implemented: sealed, first order but unfortunately with resonant enclosures and notoriously cheap and bad performing drivers. Revel’s Gem created a lot of noise stating that they make own custom driver for their own custom enclosure. They told a lot about use of lasers for reading the enclosure resonances but in reality it turned out to be juts marketing BS, as the Revel Gem’s are very auditable during listenings.  I am talking about the expansive monitors. If we look at the less expansive monitors then the situation with sound of enclosures even more grim.

I was suggested to try Celestion SL-600 that reportedly is free from any “enclosure sound”. The SL-600 are sealed,  employs some completely off the wall plastics woofers that looks like was specially made for this speaker. There is a lot of attraction in the SL-600 and also there are some wrong things in them (sensitivity 82dB, HF zobeling and so on…) but I decided to try them. In the worst case, if the SL-600 do not sound good, it would be interesting to play with it’s aluminum enclosure.  The speakers employ the standard 6.5” woofers and it would be always easy to put in “good” 95dB sensitive drivers, go for first order and see what happens… I have in my storage JBL P650 and GTO603, Focal Utopia 165A that I used in my car… there are of course more interesting drivers… like the Zellatrons...

I will be reporting the findings…

Romy the Cat

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