Dahlquist DQ-1LP crossover owners
Good decision. You get not only the Rythmik dipole-cancellation compensation shelving circuit, but a great sub power amp, x/o, and other controls (phase, damping). The Rythmik plate amp is available in a couple of iterations: 370 watt, 600 watt, and dual-channel 400 watt. It is also available in both single-ended/RCA and balanced/XLR form. |
Hi bdp24, I have just received an email from a First Watt dealer. He said that the B-4 is a two-way crossover. If you want to have three-way active crossover system, you will need two B-4’s and connect them in a cascading fashion. A “6 dB boost” of sorts can be achieved by attenuating the top-end(s) and having a linestage preamp with more gain (if needed) or power amps with more sensitive inputs (if needed). The B-4 and set up is complex. I agree with Nelson Pass who has said that with active crossover a person “needs to know where they are, where they are going, and when they’ve arrived.” Crossovers with millions of combinations are not for everyone. I agree with him after reading the owners manual. I will go with the Rythmik OB. Happy Memorial weekend. Cheers. |
Horacio, I just looked it up on the First Watt website, to refresh my memory. The B4 is a regular x/o, but there is a special version of it---the B5, made especially and specifically for full-range drivers with woofers in open baffles. Go to the First Watt site for all the details. Regarding the Dahlquist DQ-LP1 and the Magneplanar Tympani-IV and IVa loudspeakers, I remember why the Tympani requires the 3rd order (18dB/octave) low-pass filter that the DQ-LP1 provides rather than the 1st order required to compensate for the 6dB/octave roll-off caused by the dipole cancellation found in all open baffle woofers: It is to create the correct relationship between the Tympani’s woofer panels and it’s midrange/tweeter drivers, in terms of phasing. By the way, the T-IV requires a 1st order-6dB/octave high-pass filter at 500Hz, but the T-IVa a 2nd order-12dB/octave h-p filter at 400Hz. The Dahlquist provides the former, but not the latter. That’s one reason I got the First Watt B4---it provides 1st-2nd-3rd-4th order filters, both high-pass and low-pass, from 25Hz to 3200Hz, in 25Hz increments. Incredible! |
Yeah Horacio, the GR Research/Rythmik OB/Dipole Sub isn't exactly cheap, though it is worth what it costs. And the First Watt B4 x/o for dipole subs is about the same price as a pair of those subs, $1500 list, discounted to about $1200. Rodman, the Dahlquist is actually perfect for use with Tympani IV and IVa bass panels, as they require exactly what the DQ-LP1 provides---a 250Hz, 18dB/octave electronic filter. But that is in addition to the acoustic roll-off of the speaker, which is not textbook dipole (for some reason). |
Thanks chaps for the info about the Dahlquist. I was planning to buy one to use with a pair of Gradient W-63 OB clones using two 12" Peerless 830500 drivers per side, it is very similar to the prototype built by Sigfried Linkwitz. The problem with the crossover is that the sub needs a 6dB/octave boost because it is a dipole and I would guess most off-the-shelf solutions don't offer this. The subs will be connected to my pair of QUAD ESL-63. I would also like to use my spare QUAD 405-2 for the subs. I considered the Rythmik OB kit using two GR SW12-8FR and one A370PEQ Servo amplifier) but the dual driver configuration costs $1,200. I am retired, with a fixed income and the price is a little bit stiff. The price of the Gradient project would cost $252 for the drivers, plus the price for a crossover. I will build the enclosure myself, I have plenty of baltic plywood left from other projects. Best regards, Horacio |
Good thought, rodman, but what f456gt is in need of is not a set boost of 5dB at 20Hz (or any other single frequency), but rather a 6dB/octave slope to counteract the dipole cancellation of his subs, adjustable for different x/o frequencies. THAT is exactly what the dipole "shelving" circuit in the Rythmik plate amp provides. The only separate x/o I know of that provides that is the special version of the First Watt B4, made especially for open baffle speakers, which also of course exhibit dipole cancellation with decreasing frequency. |
I used a modded DQ-LP1 for better than two decades and wish I hadn’t sold it. I’m not certain if a 5dB boost at 20Hz is enough for what you need, but the DQ-LP1 does offer that, via it’s EQ setting. Mentioned under, "controls and adjustments" on page 3 of the manual. If you need the entire Bass level increased, you could adjust in favor of the bottom, via the Level settings, which offer 15dB of gain. Manual here: (https://sites.google.com/site/mpbarney/home/dahlquist-dq-lp1) |
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The Dahlquist DQ-LP1 provides an 18dB/octave (3rd order) active low-pass filter, and a 6dB/octave (1st order) passive high-pass filter. So no, the DQ-LP1 will not give you the 6dB/octave boost you need to counteract the dipole cancellation in your subs (I know because I have dipole subs and speakers, and a DQ-LP1). However, Rythmik Audio, in conjunction with GR Research, has designed an OB/Dipole sub, and the plate amp included in the sub kit DOES include a 6dB/octave "shelving" boost circuit---specifically to compensate for dipole cancellation. The plate amp is available separately, a mono 370 watter with a lot of great features and controls specifically designed for subwoofers. The x/o frequency is adjustable from 40Hz all the way up to around 300Hz---very versatile. Look on the Rythmik website for more info. |
