Crossovers - Page 2 - Home Theater Forum and Systems -

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post #11 of 15 Old 05-15-06, 02:12 PM
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Re: Crossovers

I had always worked under the assumption that, if you didn't have to, you shouldn't let a speaker run full range, i.e., don't let it roll off naturally. If you cut off the lower (higher power stuff) your mids and highs are cleaner and you don't don't run the speakers at the lower ranges which they won't reproduce well any way. I really have no data/hard facts/etc to back up my assumptions, it's just what I had assumed based on the general info I've picked up.
I’ve always heard the same thing as well. Apparently, excursion from the woofer is the source of a driver’s distortion (so it’s probably the mids that improve, not the highs). Relieve the speaker of bass frequencies, and it no longer requires much cone movement, and therefore should deliver cleaner midrange. Or so the story goes – perhaps those more expert in loudspeakers could shed some light. Of course, one could debate whether or not the distortion added from cone movement is audible, but that’s another story.

As for a reasonably priced crossover, I found a used Rane AC22 for $150 on ebay. If you look a little longer, I'm sure you can find one for <$100. Granted, they are used, but for <$100, I think I'd take that chance. If you were going to go with a crossover, would this be a way to go?
If the price is right, it’s worth a try. However, I have had some issue with other Rane equipment in pro applications, adding audible to the signal that shouldn’t be there. Some of their gear also seems to be susceptible to picking up noise from powerful transformers, so you might not want to place it directly on top of or below an amplifier.

If you don’t get what you want from the Rane, try Ashly, they generally have a better reputation. Try to find one of their old XR-1000 crossovers (I think that’s the model number), which you can probably get for only a little more than the Rane. For one thing, they have a nifty “Response” knob that is useful for filling in the hole you get between the high and low filters.

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post #12 of 15 Old 05-15-06, 02:20 PM
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Re: Crossovers

I had always worked under the assumption that, if you didn't have to, you shouldn't let a speaker run full range
But there's the rub.

It depends on the situation and what you're willing to give up.

Are you willing to add the noise floor and possible distortion of a $100 device because you don't want to feed a set of full range speakers a full range signal? Unless reed.hannebaum has a set of speakers that specifically won't accept full range signals, I would rather take the cheap devices out of the signal chain and see how it sounds.

In a subwoofer chain, it doesn't really matter, so we can add cheap BFD's and crossovers and not be particularily concerned.

In a normal situation where the bass management is carried out in the digital domain, I have no problem - But reed.hannebaum is using analog crossovers, and he wants to do it on the cheap. That's good, but he has to get creative. I thought my solution might get him what he wants.

gsmollin seems to agree. hehehehe, we're both from engineering and understand thd and noise very well.

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post #13 of 15 Old 05-15-06, 11:09 PM Thread Starter
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Re: Crossovers

I appreciate all the good advise and sorry about not getting back sooner. I too have read of the benefits of limiting the cone excursion of drivers in order to decrease distortion as well as attenuating high frequencies away from large drivers to prevent cone breakup. And as Wayne cautioned, appropriately band-limiting the frequency to each drive can help prevent speaker damage. These are some of the reason why almost all multi-way speakers have a passive crossover; so that cone motion is an accurate pistonic replication of the input signal.

Another good reason for doing this is why waste low or high frequency watts on a driver that can’t produce it. This is one of the reasons why the guys with SET valve amps like to bi-amp their speakers. My main amp does a good job but is no Con-Ed when it comes to producing output. If my preamp simultaneously calls for 100 watts at 30Hz and 100 watts at 1000Hz my amp would send a much degraded version of each to speakers that can only turn the low frequency energy into heat. This is the main reason I have the X-30 between my receiver and the main amp. However, as Brucek so apply pointed out, none of this makes any sense if my Xover is going to destroy my signal. Also, I certain respect his opinion, so I am going try his idea of moving the X-30 to the output of the BFD.

I can certainly appreciate the some what delicate balancing act needed for minimizing quantization error. It’s a shame that most of our receivers have to turn a digital version of the LFE channel into an analog signal just to send it over to the BFD to get converted back to digital. Be that as it may, I totally agree that I don’t want to starve the BFD input for signal strength. But what I have failed to mention is that I am using an amp with separate L/R volume controls to drive my subwoofer(s). So I can trim this amp to balance my subwoofer(s) with the mains. This also allows me to turn up the gain on the X-30 to utilize the full dynamic range of the BFD ADC’s and DAC’s.

I find Wayne’s experience and advice with stereo subwoofers very helpful. My listening room is a real mixed bag. The asymmetry caused by a large opening into an adjoining room is not good, but fortunately that is in the back of the room away from my main speakers and primary listening position. Up front the room is very symmetrical. I casually listen to music about 50% of the time, seriously listen about 30%, and watch movies at the other times. In my previous post I stated that my main interest here is sound quality, not extreme SPL. In the back of my room I have an SVS 25-31 sourced from the LFE of my receiver to give me slam for movies. What I am looking for from the stereo subwoofer setup is a more immersive sound while listening to music either in 2-channel or 7-channel stereo.

I have seen the AudioControl Phase Coupled Activator once on EBAY (where I buy most everything). I will definitely look into this unit further, thanks. I have checked out the Rane AC22 and the specs aren’t bad, but if you Google deep enough, you will find more than its share bad user experiences. The Ashley and the dbx 223 crossovers do seem to fair better, but still there are some bad reports. I suppose you will always find somebody with a bad experience with any equipment, but I don’t see many people using these crossovers for serious audio either. However, I have not looked at all for the Ashley XR-1000, so I will check it out, thanks.

I think I have decided to roll the dice and implement the stereo subwoofer setup and see what happens. I will check out the suggested crossovers and if nothing else, I will go with the dual X30’s. At any rate, I will try both crossover insertion schemes and see which works best. My mains are on stands raising them just about the height of the dbx subs, so I have some latitude in moving them around along the front wall (the Quads sound best a couple of feet out front). I have a lot of experimentation ahead, but I’ve downloaded REW so I can eliminate the dreaded “I hear what I hope to hear” syndrome.

I thank everyone for their valuable input, but keep the cards and letters coming if you have more info.
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post #14 of 15 Old 05-16-06, 02:42 AM
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Re: Crossovers

At any rate, I will try both crossover insertion schemes and see which works best.
That, in the end, is I think the best advice I think anyone can give you. If you have the time and willingness to experiment, seeing what YOU like best is what it's all about.

Let us know what you find out.

Good luck and happy listening.

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post #15 of 15 Old 05-17-06, 05:11 PM Thread Starter
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Re: Crossovers


It seems like I am always late getting back to people, but thanks for you earlier comments and you words of encouragement.

As an update, I won an EBAY auction for another subwoofer and now I am on the hunt for a good crossover. Once I get everything together and adjusted, I will update everyone on the success or failure of this little endeavor.

By the way, I am not doing all that well with the WAF. She can't believe there is going to be another subwoofer in the house; she hates those things. Placating her will be more expensive than what I invest in the equipment!
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