RBH Sound has done some cool things with the third generation of their Impression series, which has always been their entry-level loudspeaker series. They moved production largely in-house instead of outsourcing manufacturing to China. They have chosen to use more premium components and materials, like better drivers and stronger enclosure construction. And they have also broadened the range of speakers in the Impression series, which is made easy by the fact that they build them in-house, so they have something to fit a wide range of circumstances. I looked at their third-generation Impression series in my review of the
85-i floor-standing speakers, which I quite liked. However, since the Impression series now has such a wide range of speakers, I wanted to look at something very different. The
85-i was great for situations where users wanted a modestly-sized full-range speaker so they could have deep bass without needing a large-footprint speaker or the addition of a subwoofer. But what if you weren’t so constrained by not using a subwoofer and wanted something that was made to be used with a sub? Enter the 55-ir LCR bookshelf speaker.
READ: RBH Sound 55-ir Bookshelf Loudspeaker Review
Shady, your speaker reviews are always fascinating.
That is clearly not a bad speaker but compromised.
The first point I would make if that frequency dips are far better tolerated than peaks. If that notch in the mid band was a peak of that magnitude then that speaker would sound awful.
Now a word about the BBC smiley with was not as deep, and broader, than the one you documented. It was intentional in their smaller monitors. That is because the speakers were used in small monitoring rooms and especially in studios within vans, actually what we call semis here. So the engineers were always close to their monitors. What the smiley did was create a more recessed image behind the plane of the speakers. This helps create a more realistic balance for reproduction in larger space (home living rooms). I did the same for monitoring live broadcasts in small rooms off the concert stage.
However this, dip is narrower and deeper. My guess is that it is related to the fourth order crossover. These are really tricky due to resonances in the multiple inductors and capacitors. Also there is an inevitable delay as the woofer is a whole cycle behind the tweeter at crossover. This gives the speaker a slightly "slugged" sound. So I, if I had to use a fourth order, filter, would always keep the crossover out of the speech discrimination band which means keeping out of the 400Hz to 4 KHz frequency band, which restricts them to three way speakers. You also can run into all kinds of electrical resonances.
There seems to be a likely cabinet resonance at 750 Hz by that notch in the impedance curve.
The other issue is metal cone drivers. Their advantage is that they generally reach the first break up mode higher then a lot of other materials. The problem is that when the do reach break up, it is sudden and violent with a huge peak in the FR. Having said that, I like metal cone drivers, but you have to be able to deal with the violent break up mode. The usual method is as here to use a high order crossover or notch filter.
I got lucky with my SEAS metal drivers with a 2.5 KHz crossover. I managed to use a second order crossover, and make the crossover for the FR divide also the notch filter for the fierce break up peak at 3.5 KHz. It actually worked, but I think a bit of luck was involved.
So, given the design challenges posed by speakers like this I think although the design not perfect, it is not an unpleasant speaker as you found out.
