@stv Got my organ composers mixed up. Lol
@YSDR Steep filters down low ruin phase linearity relative to the upper bass, unless I use linear phase filters in DSP. I'm trying to stay in the analog domain with the crossover. That's a reason why I'm trying to use alignments and tuning which provides some mechanical protection against over excursion and DC offset. I'm willing to risk some amount of overexcursion and the DC offset protection is set at 10V, so i feel comfortable with that. The thing people often oversee is how the low end rolloff and subsonic filtering stack up to cause more delay, so I'd like to stay out of the meat of the curve with the rolloff point. I have some adjustment capability around lower cutoff using the low end boost on the plate amps, which have a wide range of adjustment.
@cowanaudio I like some of the Beyma stuff. Their larger drivers tend to fill a void in applications from the other big companies. They're not as easy to get them here compared to other brands. The BMS 18 that is being discussed is the best choice of all the suitable drivers I've found. Its just crazy expensive for a pair, but a big plus is being available in 4 ohms with minimal TSP difference to the 8 ohm model.
@Pano Thats the series of drivers I was looking at here in this thread. I suspected they wouldn't be that extended up top, but I only need a few hundred hz extension at the most. The interesting thing about the 12" and 15" ferrite models is the large xmax. That may or may not be a plus depending on the available suspension travel. Sometimes the suspension doesn't have enough linesr travel to take advantage of the longer VC windings and presents a potential risk to the driver's durability. This would only be an issue for the surround, looking at the spider construction.
@phase_accurate You pretty much nailed it with your example. I'm looking for a more analytical quality of lower bass to identify poor low end in recordings and allow for accurate monitoring in that spectrum. This way there's less likelihood of doing something wrong or bad in the low end and having a mix translate better on other systems and media. Sometimes its necessary to cut some of the low end to make it sound better on certain compression algorithms, but for the most part I just need accurate and intelligable low end.
@YSDR Steep filters down low ruin phase linearity relative to the upper bass, unless I use linear phase filters in DSP. I'm trying to stay in the analog domain with the crossover. That's a reason why I'm trying to use alignments and tuning which provides some mechanical protection against over excursion and DC offset. I'm willing to risk some amount of overexcursion and the DC offset protection is set at 10V, so i feel comfortable with that. The thing people often oversee is how the low end rolloff and subsonic filtering stack up to cause more delay, so I'd like to stay out of the meat of the curve with the rolloff point. I have some adjustment capability around lower cutoff using the low end boost on the plate amps, which have a wide range of adjustment.
@cowanaudio I like some of the Beyma stuff. Their larger drivers tend to fill a void in applications from the other big companies. They're not as easy to get them here compared to other brands. The BMS 18 that is being discussed is the best choice of all the suitable drivers I've found. Its just crazy expensive for a pair, but a big plus is being available in 4 ohms with minimal TSP difference to the 8 ohm model.
@Pano Thats the series of drivers I was looking at here in this thread. I suspected they wouldn't be that extended up top, but I only need a few hundred hz extension at the most. The interesting thing about the 12" and 15" ferrite models is the large xmax. That may or may not be a plus depending on the available suspension travel. Sometimes the suspension doesn't have enough linesr travel to take advantage of the longer VC windings and presents a potential risk to the driver's durability. This would only be an issue for the surround, looking at the spider construction.
@phase_accurate You pretty much nailed it with your example. I'm looking for a more analytical quality of lower bass to identify poor low end in recordings and allow for accurate monitoring in that spectrum. This way there's less likelihood of doing something wrong or bad in the low end and having a mix translate better on other systems and media. Sometimes its necessary to cut some of the low end to make it sound better on certain compression algorithms, but for the most part I just need accurate and intelligable low end.
I may have an alternative if none of the above mentioned drivers work out. They call these the Revalator's cheap brother. I have 4 of these Peerless NE315W-08 woofers. TSP - Fs= 21 hz , Qts= 0.39 , Vas= 185 ltrs , xmax= 12 mm. They're not the most sensitive driver, but they'll go LOW and are a viable candidate for a QB3 alignment. They won't go that loud and in no way suitable for any pro use, but they're accurate. At least its a backup plan.
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Fit for purpose filtering don't causes any phase related problems. You don't need to use high-pass filtering down low, instead shelf and peak filters wich causes much less phase shifting and still can give adequate protection. But I don't want to fight against what you want (for some reasons), do what you think is good.
@YSDR Yes, that makes sense. My concern with HP filters is the phase shift starts earlier than the designated rolloff frequency, affecting phase even higher up above the actual HP corner frequency. Thats why I want to stay as far away as I can from that point or compromise the driver overexcursion protection. Only DSP will let me achieve linear phase filtering, which may or may not be available depending on the amplifier I choose to use.
Pretty much the same thing as YSDR's response in #36.
That said, I have no sonic reservations about using an Fb below a B&C woofer's Fs.
I'm presently using two cabinets with 8" B&C 8NDL64-8 (Fs 80Hz,Xvar 5.5mm, BL 17.5 Txm) as subs, their Fb ~25Hz, equalized to +/-3dB in room response from 19-60Hz.
Can definitely hear when there is something going on in the music down low!
https://www.diyaudio.com/community/...riend-with-focal-solo-be.408946/#post-7596244
The Peerless NE315W-08 look interesting, four of them should make for some trouser flapping...
Art
@YSDR No worries about fighting. You're being respectful of my intentions and not judgmental, trying to push me in a direction I dont prefer to go. I have used shelf filters before and struggled with nonlinear delay across the rest of the passband. The pre-ringing also has the potential to sour things. As long as any latency in processing is linear across the entire spectrum, its acceptable. I've seen and heard some strange things using various filters and haven't been able to draw any definitive conclusion as to the cause(s).
@weltersys Interesting application of the 8NDL64. This is a very good driver for its size with a big VC, although I'm weary of its suspension linearity and actual xmax.
On a side note, how much level are you getting that low down and what are the tuning parameters? How would it compare to the 8NDL51 for low end extension?
The Peerless woofers are unique. They don't have a huge motor and I don't trust their power ratings, being they have titanium formers with little heat conductance. They get pretty hot when pushing them with just 75 watts sine at minimum impedance. They do however have low THD across the board.
@weltersys Interesting application of the 8NDL64. This is a very good driver for its size with a big VC, although I'm weary of its suspension linearity and actual xmax.
On a side note, how much level are you getting that low down and what are the tuning parameters? How would it compare to the 8NDL51 for low end extension?
The Peerless woofers are unique. They don't have a huge motor and I don't trust their power ratings, being they have titanium formers with little heat conductance. They get pretty hot when pushing them with just 75 watts sine at minimum impedance. They do however have low THD across the board.
B&C 8NDL64-8 has less Xmax/Xvar than the 8NDL51, I'd think the 8NDL51 would have a bit more output above Fb, but less around Fb, due to the 8NDL64 having more power handling and higher Bl.
The 8NDL64 are in around 17L net, the exterior (undersized) ports using a variety of PVC plumbing.
https://www.diyaudio.com/community/threads/hot-rod-8-2-way-pa-studio-monitor.343215/
Adding 180 degree “U” (2x90degree) fittings to the 35 Hz tuning lower it to 28Hz, adding 5” pipe and 1.5 to 2” adapter dropped it to ~25Hz.
The Hornresp sim says 1/2 space response at 22volts (Xmax ~40Hz) for one cabinet would be 94dB at 19Hz, so 100 for two.
One of the subs is in a corner, the other under the Tannoy 6.5PBM tops, I'd estimate with room gain they can hit ~106dB down low using the 90 watt per side Fosi Audio V3 amp. Probably could do 110dB if
The ports chuff a bit when pushed, but the drivers don't seem to complain (much..) even below Fb. The suspension stays quiet up to Xlim (~11mm IIRC). Can't hear that over the baseboard heater rattling noise..
I hardly ever use the system higher than conversational levels, if I wanted to accurately mix I'd be looking for something like the BMS 18n862 or your Peerless NE315W-08, and a decent room to put them in 😉 .
Art
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Thank you guys! Especially Art, for the plethora of data. I came close to buying a pair of 8NDL64 but decided to go with 8NDL51s due to the cleaner impedance curve. I've used a whole bunch of 8NDL51s in customer builds and they have pristine midrange past 1.5k with the cleanest midbass I've heard from a pro driver. They're astonishingly accurate as well, even better than some 6s I've used. We're building a set of tops for this system with 2 of these and a PRV D260MYB ring radiator on STH100s crossed at 2.5k.
Its quite amazing how the 8NDL51 does with low end down to 40 hz in 25 ltrs with a slightly lower tuning. It's probably the most musical sounding pro driver I've come across for a compact 2 way PA speaker and its able to be used as a hifi driver. Theres nothing that can upset this midbass in terms of music. It responds well to EQ and never complains up to xlim. If the 8NDL64 is just as good in the midrange as the 8NDL51, it would be the bargain of the century.
Its quite amazing how the 8NDL51 does with low end down to 40 hz in 25 ltrs with a slightly lower tuning. It's probably the most musical sounding pro driver I've come across for a compact 2 way PA speaker and its able to be used as a hifi driver. Theres nothing that can upset this midbass in terms of music. It responds well to EQ and never complains up to xlim. If the 8NDL64 is just as good in the midrange as the 8NDL51, it would be the bargain of the century.