Voicing a System: To colour or not to colour? - Page 18

I think there are three 18 inch dynamic drivers behind each horn.

See ya
Steve

Strange! BTW, I had a classical or unamplified jazz concert in mind. And I still think the wish for colorations instead of a neutral presentation with a home stereo system arises from imperfections of the system other than frequency response, primarily of the sound transducers (particularly in terms of spatial presentation, but also transient response), which take a lot of the liveliness away, and the colorations may serve as compensation for this lack.

No. That's a new aspect. So mids and highs are covered by conventional transducers? Such as...? (I think it was clear that I assumed a speaker system equipped with midrange and treble horns -- also you were talking of a «horn system» yourself in another thread.)

As mentioned, I haven't much experience with bass horns. The ones I've gained and the audition of the Klipschorn have shown me that a bass horn has many of the qualities you describe (punch, attack), also extension if the walls are used as extension of the horn mouth, creating sort of infinite horn length and mouth area. Apart from the inevitable inner reflections and resonances a bass horn would seem a usable and attractive variant if space is no issue. But there's one thing that bothered me: As controlled and tight the Klipschorn bass was, it didn't sound natural with acoustic instruments to me: not clean and round enough, there was an omnipresent edginess and woodiness. It's not hard to guess where it comes from: The horn walls are made of fairly thin wooden or chipboard plates, and they resonate as hell. So I don't think a bass horn made of wood of justifiable thickness can work properly at all for high sonic demands. Considering that even the massive wooden horns I used for my midrange drivers (Fostex and own designs) had a slight woody tendency.

Well, I don't think the extensive excursion into horn phenomena has done any harm anyway, even if the system in question isn't concerned by them. After all it has shown the importance of time phenomena.

Sorry for the confusion. I've always been talking about the horn in relation to the bass response. There's no advantage to putting a tweeter behind a horn. High frequencies are already very directional, and the main advantage of a exponential horn is to extend the bass frequencies down into the subbass region.

The idea is that a single speaker would not be able to handle the huge excursions required to reproduce frequencies below 30Hz at any kind of volume level. Moving back and forth three inches each way 30 times a second would rip up most speakers. Using multiple drivers, you divide the distance of the excursion among the number of drivers, reducing it for any single driver. However, multiple drivers have problems with phase error, so you put them behind a horn so they all work together as a single unit.

A true exponential horn with a mouth six to eight feet across is able to reproduce all the way down to 20Hz without using walls or floor. That's what the system I am talking about is set up to do. Space isn't as much of an issue, because the horn is divided into quarters, each quarter being a separate functional unit on its own. Depending on the size of the venue, you can use 1, 2 or all 4 units. Each unit has a dolly built into the cabinet, so a single person can wrangle the cabinets alone. When all four are stacked and bound together, it forms a full size exponential horn.

The cabinets are as solid as a rock. I saw the sheets of 1 inch plywood he was making them out of, and they were top quality and solid. The outside of the cases are carpeted. I have no idea how he got the perfect curve to the horn, but my friend's a pretty amazing carpenter. He mentioned that he devised a system of bracing inside the cabinet that eliminated vibration around the horn. The sound from them is solid and punchy with no hollow or woody sound at all.

I'm not sure what the system uses for mids and highs. I'll ask and find out. I think he plans on creating a slightly different setup for the full installation, but he says that the mids and highs are much easier to deal with than the bass. Current speaker technology is great at reproducing the upper end, it's the bottom that always seems to be problematic.

Live rock shows are usually horribly equalized with massive spikes that can easily cause hearing damage. The mixers travel with the band and work in a different stadium every night, and they rarely take the time to really understand the acoustics of the room. They just slap a stock eq curve up and blame any bad sound on the room. I don't know why there hasn't been more lawsuits against promoters for hearing loss.

See ya
Steve

One particular instance in memory is when I saw the Michele Camilo trio at the Palace of Fine Arts in SF. This is a piano/drums/electric bass trio. The articulation of Anthony Jackson on bass was inaudible. Only the lower frequencies of his playing came through. This was one of the cases where I can see his fingers moving but all I hear is "bluuuuhh". It upset me that in a trio setting one player's contribution was reduced to mud.

I went to the sound man during intermission to request that the high end on the bass be boosted, but there was already someone there venting at the soundman for the same reason. The soundman said that Michele had asked for it that way becuase if he boosted the bass that the onstage sound became too boomy. I tried to explain that I don't want an increase in the low end, I want the upper frequency range boosted so that I might be able to discern the individual notes being played by Mr. Jackson. The soundman couldn't grok the concept. I think he was in defensive mode after what the previous guy had told him.

Anyway it's an example of an instance where I would have eq'ed the show differently than the soundman, and not for the purposes of introducing "color" but rather for overall clarity. My comment came from the fact that I would often eq a show differently than the guy running the board that particular night.

For acoustic music I see your point.

-Dan

Really?


Sorry, nothing of this is true. High frequencies aren't directional by themselves, the dispersion characteristic is defined by the membrane geometry. So usual 1" dome tweeters have a semi-spherical radiation up to 6 or 8 kHz, above they become more and more directional, smaller domes correspondingly later. Horns can compensate to some degree for the arbitrary unevenness of directionality in that they create directionality also with lower frequencies. A welcome side effect of this feature is increased efficiency. The advantage of constant directivity is less coloration due to frequency-dependent fluctuations of the reflected sound in the listening room. It's true that horns also tend to increase lower frequencies more than higher frequencies, so they can be used to extend the frequency response of bass speakers, but save for arrays which integrate the corner into the horn geometry, bass horns don't generally offer lower bass than conventional bass systems (rather the opposite!). In fact typical horn drivers have very low Q factors and relatively high resonant frequencies, that's why the horn's bass amplification effect is even essential for a flat frequency response.


I don't see any phase problems in the frequency area 18" drivers are capable of working properly without horn. In turn you get extreme runtime errors between the horn-loaded bass drivers and the naked midrange driver. The advantage offered by the horn is increased efficiency and load capacity. But why the hell three 18" drivers per channel plus horn amplification!? Are we really talking about music reproduction in an apartment, at home?


O.k. -- but why renounce the horn extension provided by the walls and waste so much material and space for the same effect (if at all)? Plus the need for equalizing (because you get inevitable jumps with acoustic impedance between horn mouth and walls).


Of course low frequencies offer most problems in a normal listening room, but high frequencies are more important for a natural reproduction, and the latter is still an issue, even with today's technology and independent of the driver principle.

You haven't been reading carefully.

See ya
Steve