Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?

camplo

Member
2019-02-25 2:27 am
I've been on a quest to build my own own reference monitor. In that journey I've come to know the JBL m2. Maybe its highly prized for its flat response but all I see is another 2-way. There are already flat two ways on the market. So not sure what the hype would be around this speaker, beyond having accuracy and spl, making useful for far field as well as near field.
As a full-range solution if a 2 way that took care of sub bass, gets rid of another cross and thats cool. I've found a driver that could be used for the top

FaitalPRO HF146 - 1.4" Compression Driver

A woofer for the bottom can be found. The question is, how is a woofer that is going to be easily responsible from 30hz to ~1000hz going to behave? Lets say we are auditioning rap, edm, or some other deep bass reproduction that causes high woofer excursion, how is the top range of that speaker going to sound? It seems to me a 3 way is almost always better, but I'm not the finally say, the results are, anyone have a strong opinion on this?
 
If it needs to be high efficiency then it's going to be pretty big.

Does it need to be high efficiency or just able to hit 114dB @ 30Hz, in what I'm assuming is 4pi radiation.

So essentially you want to hit 120dB at 30Hz at one meter before any diffraction and cabinet effects come into it.
 
My horn system is much like what you are describing. I never would have expected a sub driver to cover up to 500hz, but it does nicely. The horn is very high sensitivity, but the woofer obviously is not. You get SET magic up top with real power down low. I love electronic music. Saw James Blake live and it's great fun to recreate the experience in my listening room, albeit with much better bass quality than live.

the "SPIEKER" my almost 20 year prototype finally done
 

camplo

Member
2019-02-25 2:27 am
I’m basically copying the jbl m2 specs. It’s just hard for me to accept that a woofer can play an 808 tuned to the 30s and handle lower to mid, midrange, at the same time, especially at a loud volume. It just seems the large excursion to create that bass would be a problem for the upper register duties. No one said anything about the top driver I suggested above so at least that part must be good to go. I couldn’t find any distortion figures����*♂️
I completely agree, for the task, a 3 way right? But then we have this jbl m2 that has an F3 of 30hz, crossed at 800hz...and everything’s peachy? Really? Even at 117db?
My 3way runs the mid naked crossed at ~150 & 2.1khz....a two way rids me of a crossover but then puts on in the middle of the midrange. I can’t tell who’s winning ����*♂️
 
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camplo

Member
2019-02-25 2:27 am
Well the FaitalPro driver I posted has a really nice frequency response. Does anyone know how to judge a compression driver beyond that cause I have no idea.

Any advice on search for a woofer to compliment my task? I’ve been told I can judge transient response by inductance. I’ve not come across a driver that play 30hz at high volume without an Xmax of 19hz. Maybe it’s just a matter of having a tuned port at desired lowest note? I have a balanced minidsp for crossover and eq. I’d like to have a linear response from 30hz and up.

Thanks for the help!
 
Maybe I should keep my opinions to myself since I haven't heard the M2, but physics does pose a few obstacles in a 2-way. If you're willing to tolerate a shortcoming here and there -- a touch of beaming in the woofer top octave, a little bit of FM when bass-heavy program material gets loud, allowing a bit of a roll-off above about 7 kHz improves the compression driver ruggedness since it has to get down to 1 kHz, then allowing a gentle roll-off in the bottom octave allows better efficiency from 60 to 150 or so. To overcome any of these exacts a penalty in overall efficiency.

JBL no doubt has plenty of clever folk on hand to tackle these issues, and they're certainly charging enough for the M2 to justify the effort, but they have the same laws of physics as the rest of us.

Best of luck.

Regards,
Rick
 
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Maybe JBL 4722 Cinema 2 way loudspeaker or similar design. Frequency range 30 Hz to 20 kHz. Frequency Response (±3 dB): 40 Hz - 19 kHz
System Sensitivity: 104 dB, 2.83V @ 1 m with passive XO. https://www.jblpro.com/ProductAttachments/SS4722_0509.pdf

I have a pair and really like them, especially for the money. I biamp them with digital XO at 630 Hz. Similar 15" woofer design to the M2. I switched out the stock 2432 3" CD to a large format 4" JBL 2453h-SL aquaplas Ti. It's a mod after user notnyt at AVSForum tried several CD's on the 2384 wavguide, including the D2 used in the M2. The 2453h-SL is a smooth CD for reasonable $'s.

To get to 30 Hz, you need a big space. The top octave isn't the smoothest with a 1.5" exit driver. But a full range, high SPL, low distortion 2 way system. Maximum SPL: 130 dB, @ 1 m (3.3 ft) 136 dB peak.
 
I can see two options here. One is high-sensitivity and will need a big box, the other can be done in a fairly compact design:

- Large-format compression driver on a big horn, crossed to a 15" PA woofer in the 600Hz range.
- 3-4" full-range driver, 12" HiFi subwoofer, crossover in the 2-300Hz range.

Lets take a look at your LF requirements. 120dB at 30Hz, 1m, groundplane, is quite an ask. A good 15" in a 150L ported box will just about do it, although you'll need something that'll manage 20mm p/p cone travel while staying linear. The top-end 15" PA sub drivers will manage that, and can play up to the 600Hz range just fine.

If it was mine, I'd use a pair of 15"s per side, and then find the biggest baddest compression driver I could. The RCF 4" diaphragm units would be on my list, as would the BMS coaxial compression drivers (only if you're willing to bend the rules - they are technically two drivers in one). I'd also go through all the 3" diaphragm units and find the ones that are happy running low. The EV DH1a would be up there, too, but only for a fixed installation. Those things are heavy.

Use the biggest HF horn you can find that still matches the dispersion angles you're looking for. The HF driver is going to have a difficult time at the bottom of it's passband, so give it all the help you can. You'd be looking at a finished cabinet volume of the order of 500L.

For the low-sensitivity option, I'd be looking at a Mark Audio Alpair 7.3, plus a pair of the aluminium-coned 12" Dayton sub drivers. Maybe sealed boxes, maybe ported and tuned to the lowest note you want to reproduce. See what Hornresp says.
You could probably have that done in 100L.

For all the systems, you'll need digital processing and a lot of clean power - a couple of kilowatts per side would be a start. I already have the amp on-hand, but a Powersoft T604 would be my go-to.

Chris
 
I’m basically copying the jbl m2 specs. It’s just hard for me to accept that a woofer can play an 808 tuned to the 30s and handle lower to mid, midrange, at the same time, especially at a loud volume. It just seems the large excursion to create that bass would be a problem for the upper register duties.

I have never heard any commercial recording that has 808 tuned 30s. Mostly 40-80Hz.