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In Reply to: Re: Xover frequency for biamped Quad ESL 57s? posted by drquad on November 16, 2006 at 17:59:16:
Hey Sandro,70-85Hz. Got it. I remember your site. Awesome! Perhaps you have time for another question: Of the available designs, do you have a recommendation for a subwoofer type that would keep up with the Quad's? I've heard transmission line...
Follow Ups:
I don't think that rolling off the low frequencies below 70-85 Hz by
introducing a passive crossover in the form of a capacitor is a good idea. It only introduces some phase shift which you dont't need.
Just run your ESL57 full range and roll off the high frequencies from
your subwoofer above 50-60 Hz. I know from personal experience that this is by far the best solution.
IMO, the phase shift introduced by the two caps I recommend is the much lesser of two evils. The Quad's penchant for buzzing bass panels is a well known fact among Quad owners & is rather simply mitigated with the insertion of a couple of small value caps at the main amplifier's input. I have conducted several a-b tests and, without exception, the bass panel roll off produces cleaner midbass & the bass panels don't sound like a small but angry bee hive on heavy bass notes!Sandro
'a small but angry bee hive'Great description! I agree with your observations. The series input cap is the way to go on the Quad amp. What ever negative there might be to this approach is swamped by the positive benefits. The speaker plays cleaner in the bass region and plays a bit louder. For the head bangers in the crowd(me) every little bit helps.
Of course we can all understand a more purist approach too. At volume levels below which the bass panels don't buzz (pretty low, IMO) that scheme has value. But there's one other issue: when a sub is employed without an accompanying hi-pass filter there is measured excess energy where the speakers overlap. In my main listening room that hump gives a pleasant midbass fullness (cellos, piano, guitar, etc.) but it isn't accurate.Sandro
Well the sub I've heard that integrates best with the Quad 57 is the Gradient SW (dipole design) but it has at least three problems: 1) a less than satisfactory active crossover design which imparts a harsh quality to the the Quad's otherwise exemplary midrange; 2) the bass doesn't go down as low as other subs with more conventional designs; and 3) it's been discontinued for quite some time.You might check one of my web pages (below) for other choices. Otherwise, email me privately.
Sandro
Hello Sandro,I just bought a set of US Monitor ESL 63's with Gradient SW63's. It is my plan to incorporate them both with my ESL 63's, and also with stacked PK rebuilt '57s (a friend and I are gearing up for a planar shootout in December). I have several questions for you:
1. Would you say the same crossover point suggestion of 70-85Hz applies to stacked '57s, or would you go deeper? Would you tend to use the lower end of that range due to the added surface area?
2. Since I already have the SW63's, I would like to use them. If Gradient's crossovers are the problem, is there another outboard active crossover out there which does not impart hardness to the midrange?
3. While we're on the topic of crossover points, what would you recommend as a '63 USM crossover point?
Thanks,
Hi Paul,1. Might go a little deeper but trial & error in the listening room will decide that.
2. Don't know about other active units but there is additional frequency contouring in both of the Gradient models, and the 63 version is somewhat different from the 57.
3. Sorry but I don't have any experience adding a sub to the 63. Kentaja may be able to help you in that dept.
Sandro
1. I agree with Dr. Quad. A bit lower might be in order, but this will largely be determined by your room and your tastes. When I was running stacked ESLs I crossed over around 40-50Hz.2. You will need to use the Gradient crossover for the subs since the contour is required to make the dipole nature of the sub work correctly. Scrap the hi-pass section; it is a sonic nightmare.
I would not use any active filter on the Quad. Instead, insert a series capacitor on the input of the amp running the Quad. You will need to invert the speaker leads on the either the Quads or Gradients to maintain the correct phase thru the crossover point. The Gradient low-pass filter is 12dB/octave. The series cap would be 6dB/octave.
3. The stock Gradient crossover point is 115Hz as I recall. Higher would be better IMO, but the low pass filter is fixed. Set the high pass filter on the Quad at 115Hz.
Any active crossover will work to drive the Gradient as long as you can provide a 6dB/octave boost to the low pass filter. This compensates for the dipole cancellation effects and maintains flat frequency response on the sub. Given the nature of the ESL63 I would prefer to crossover higher than the Gradient 115Hz. More like 150-200Hz. Again, depends on your room and your tastes. I find the mid-upper bass region of the ESL63 to be on the thin side and a bit more boost in this region is in order IMO.
Let us know the results of the comparison between the stacked ESLs and the Gradient/ESL63.
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