Bert's 150 bass filter - Thanks (Oris Horns)

by Tom Russell , Tuesday, March 13, 2007, 13:48 (6252 days ago)

Bert

I want to thank you for the filter values. That thread went on a bit so I decided to start over here. I've had a chance to do an initial evaluation and I have some results. I made the bass filter using the exact values you gave and the overall system tonal balance is very good. I don't think there is a need to adjust any of the values at this time. There is plenty of bass gain. I turn the linear pot down about 1/8 of a turn and things are about right. The overall gain of the system, however, is noticeably less when compared with using the active filter.

The biggest change I experienced is in the sound quality. As you know, I use a specially built amp to drive the 150s directly. This amp rolls off the lows so I use no filter in the horn signal path. I had been using a Rane active crossover as a low pass filter to drive the bass amps and then the BD Reference cabs. I use an interconnect with a simple Y at the source to supply the horn amp and the bass filter. Before, using the active crossover, I was OK with the bass sound. Mostly, I didn't think much about it much and I thought that was a good thing. It didn't intrude into the mids. It reminded me of a slightly warm sounding LaScala. Now, with no other change but replacing the active filter with the passive filter, the bass is much more dynamic, much more felt. It's the best of both worlds with a bigger, warmer, punchier, lower, nicer sound but there are no problems with bass overages interfering with the lower mids. It is a vast difference and it's all for the better. When I decided to go with the Oris system, I knew the horns would be OK. My main concern was with the bass. I have full range electrostats and they will make one very sensitive to multiple drivers and crossovers. Either on their own or as part of the system, I have no problems with the performance of the Reference cabs. They are far better than I imagined they could be. Thanks!

Even more notable, since the installation of the passive filter the sound coming from the horn is vastly different. I am aware that I have used vastly twice. If anything, calling these changes "vastly different" is conservative. Before the passive filter, the system sound was certainly good but the horn system fell short of the electrostats in resolution, inner detail, soundstaging, imaging - less good on a lot of little things. Now, all of these parameters are essentially commensurate with the stats plus I get the dynamics and the vibrant tonal color of a horn. A very good deal! I'm not sure how the bass filter, located in it's own local circuit, can effect the sound of the horn to such a large extent but it certainly did in this instance. I wouldn't think that the changes I experienced are indicative of active/ passive filter comparisons in general but the changes I experienced are real and quite substantial. Maybe reading this could help someone else at some point. If you're having a problem with the sound but everything seems to be working up to spec and you can't figure it out, don't assume, as I did, that this part here can't possibly be effecting that part there. It ain't necessarily so.

Bert, This is the sound I was after when I decided to go to the trouble of assembling a new system. This is the sound I expected when I went off the beaten path with a specially built amp. This is, on any terms, really, absolutely, first class sound. Thanks again!!

Tom

BTW, there has been some discussion in other threads about the value of amplifiers specially designed to drive horns. Obviously, I think a dedicated amp is the way to go. The advantages of doing this are usually said to be lessening the load on the driver, by not making it handle low frequencies, and not having any device in the signal path that would effect the purity of the audio signal. True on both counts but there is another plus that is just as significant, especially if we are talking about an SET amp. The big SET design problem is the output transformer. If you make it large enough for full range lows, it is sluggish in the highs. If you optimise for the mids and highs, the lows are not so good. Asking an SET to do a full range signal into a speaker load is too much to ask. Most SET amps do the best they can to balance this but they necessarily end up with both soft bass and not much top end bandwidth. If you design an amp so it does not have to deal with the low frequencies, it allows for an optimised design of all the other performance parameters and the bandwidth goes through the roof. It sounds good, too!

Tags:
0