I've tried to integrate full-range satellites with subs before with mixed results. With main speakers that have limited LF reach to start with, I can usually get a good blend. But for speakers that have lower frequency response (my Emotiva T2s for example), the overlap area is tough to tame. The subs I'm using have a 60 Hz. minimum setting on their plate amps, and this leaves a huge peak in combined frequency response between about 35 and 75 Hz. I could tame the peak with DSP, but I'd prefer to just use an upstream crossover.
The only fly in the ointment is that the Dahlquist used multiple MCM 4558 integrated circuits. These are discontinued. The majority of pin-compatible replacements (despite having order of magnitude better audio specifications) also consume about twice or more the current of the originals. The Dahlquist's power supply is inadequate to power the newer chips. I've emailed Digikey to see if they can recommend something that would work. Hopefully, I can get an equivalent IC and just throw in some sockets on the printed circuit board and be up and running. If further power-supply modifications are needed, the Dahlquist may not be cost-efficient to repair. In that case, plan B will be to use fully-passive Harrison Labs F-Mod filters for both the high and low-pass legs. These aren't elegant, but they're actually not bad sounding, and the four needed filters (for an unbalanced setup) would cost no more than $60.
Last Edit: Apr 2, 2020 13:56:57 GMT -5 by boomzilla
The sound of Harrison F-Mods really suck, in my opinion. They are functional, yes, and I have used them hundreds of times in car audio, but if you want good sound quality they are not preferred. A far better (if more expensive) solution for home audio would be something from a place like Marchand or something made for pro audio.
Thanks again, David - I wondered about the sound of the Harrison products... I'll check out Marchand, and if I can resist being cheap, maybe the MiniDSP.
I'd read some enthusiastic stuff on the internet about the Harrison F-Mods, but when I went back and checked, it WAS all car stereo stuff - not home audio. And after looking at the price of the Marchand crossovers, the Mini-DSP is starting to look a LOT better...
Last Edit: Apr 2, 2020 21:00:23 GMT -5 by boomzilla
Hmmm... I'd put a lot of crossovers above the LP1 but it was interesting design approach. Active LPF and passive HPF IIRC (store I worked back in college was a Dahlquist dealer, among others), and as noted target subwoofers but had a fairly high upper limit (adjustable over a decade, I think, 40-400 Hz?) Distortion was good but I seem to recall the LPF being a bit on the noisy side but may be thinking of something else. Back then ARC, SAE, Soundcraftsman, Bryston, Pioneer, bunch of pro companies (natch -- I still have a dbx 223 or 224) -- most everybody had a fancy crossover coming as the satellite/sub approach was just coming into its own, many much more flexible than the LP1 (IMO).
Back to the LP1, I piddled with one for a while but decided I wanted a steeper slope on the HPF. I was also alternating between a tube and SS amp and wanted to buffer the HPF section. I honestly do not remember if it was buffered or not; I don't think so, but am not sure -- I clearly remember the HPF was passive, however, because I had to swap Rs for some customers. I should have gone with an L-R but did 18-dB for the sub (LPF) and selectable 12- or 18-dB for the mains (HPF) in my little DIY servo-sub box.
All that said, I completely agree with you and DYohn about fixing what you have -- bird in hand and all that jazz. - Don
p.s. Marchand has been around a while and has a good rep. For an inexpensive analog L-R crossover my go-to for years has been the little dbx 223x or 234x pro unit. Fairly cheap, pretty flexible, good performance, and you can get XLR/RCA or TRS/RCA (depends on the dbx model) adapters.
Price-wise, you can get cheap passive inline 1st- and 2nd-order units for maybe $50, then the miniDSP for around $100~$200 and up, dbx at around $200 (for a stereo 2-way), Marchand around $1k or so, a variety of pro crossovers in the $1k range (analog or digital), the Bryston for around $3k (last I checked), etc.