Driver (8/10 inch) for JBL 708-ish dimensioned 2-way
I am searching for a driver that can perform comparable to what is achieved with the JBL 708. The thing that is hard to get is described as: Low fs, relatively low Mms, low Vas (or a combination of T/S that makes a slightly higher Vas feasible). Or not in T/S: extension and mid-range capabilities in a small enclosure.
Speaking of which:According to 'sound on sound', the internal volume of the JBL 708P is 27 Liters, which does not account for the volume of the drivers and amplification tray: outer dimensions of the speakers of 441 x 250 x 312 mm, build from 12 mm plywood sheets. But the JBL owners manual does not give anything else than this. I was told in another forum that the driver JBL 728G is probably very close or identical to the model of the previous monitors 218F, apart from Impedance, while no specs are available for the 728G.
The specs of 218F are:
With moderate DSP-use of +3 dB gain at 42 Hz, Q of 1.67, an f3 of 42Hz is reached.
Now I know it is too much to ask to get that performance for a cheap price, but something in the region would be very cool. I am currently reducing the size of my 2-way project from 12-inch to either 10-inch or 8-inch (preferably the first) and an enclosure of 30 internal liters and I am still searching for alternatives that can do both: extend and play mids. So far, I have found the 8-inch Peerless HDS-P830869, but according to forum member Michael Chua, it does not behave as the T/S suggest: Link 1, Link 2. It needs a smaller enclosure and this is not so good. Then, there is a very basic 10-inch Beyma SM-110/N driver. That one simulates well, better than the Faital 10PR320 in the low end (I am using the 12PR320 atm), but no information on its performance can be found.
I have been scanning many manufacturers now, but maybe I have missed something. The final enclosure is thought to be about 60 x 30 x 25 cm (30 liters) and a waveguide will play on top of the woofer, crossed over at ~ 1.2 to 1.4k. Maybe you know about something!
Regards
I am searching for a driver that can perform comparable to what is achieved with the JBL 708. The thing that is hard to get is described as: Low fs, relatively low Mms, low Vas (or a combination of T/S that makes a slightly higher Vas feasible). Or not in T/S: extension and mid-range capabilities in a small enclosure.
Speaking of which:According to 'sound on sound', the internal volume of the JBL 708P is 27 Liters, which does not account for the volume of the drivers and amplification tray: outer dimensions of the speakers of 441 x 250 x 312 mm, build from 12 mm plywood sheets. But the JBL owners manual does not give anything else than this. I was told in another forum that the driver JBL 728G is probably very close or identical to the model of the previous monitors 218F, apart from Impedance, while no specs are available for the 728G.
The specs of 218F are:
Code:
fs: 45
Qts: 0.38
Qms: 4.2
Qes: 0.42
Vas: 26*
EFF: 0.55
PE: 200
Xmax: 15.7
Re: 1.8
Le 0.15
Sd: 0.215
Bl: 6.1
Mms: 31
*(must be liters, despite they say imperial cu ft, which does not make sense at all)Now I know it is too much to ask to get that performance for a cheap price, but something in the region would be very cool. I am currently reducing the size of my 2-way project from 12-inch to either 10-inch or 8-inch (preferably the first) and an enclosure of 30 internal liters and I am still searching for alternatives that can do both: extend and play mids. So far, I have found the 8-inch Peerless HDS-P830869, but according to forum member Michael Chua, it does not behave as the T/S suggest: Link 1, Link 2. It needs a smaller enclosure and this is not so good. Then, there is a very basic 10-inch Beyma SM-110/N driver. That one simulates well, better than the Faital 10PR320 in the low end (I am using the 12PR320 atm), but no information on its performance can be found.
I have been scanning many manufacturers now, but maybe I have missed something. The final enclosure is thought to be about 60 x 30 x 25 cm (30 liters) and a waveguide will play on top of the woofer, crossed over at ~ 1.2 to 1.4k. Maybe you know about something!
Regards
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- Seems to be tough to find an affordable driver in that range. I investigated comparable sized monitor systems. The driver of Genelec 1031a was produced by Peerless as the OEM P22WO03-08, it is affordable and fits the concept, but it is only available from 500 pieces on in b2b stores. Anyone has an idea if there is a way around that?
- With the Beyma, which is still the best simulating low Mms PA driver for the volume given, I am concerned about the high-Q hump of +6 dB at 500 Hz. Can this be a cone resonance? I could not find a measurement yet. Apart from that, how is the distortion?
- And if someone can contribute on the question of maximum Mms for mid range reproduction: The 9.5" SB Acoustics Satori WO24P-8 is not budget friendly at all, yet it performs. It's Mms is at 45g, which is heavier than most PA drivers I looked at: only 5g less than the 12" Faital currently in use. Could the WO24P still produce vivid mid range up to a crossover frequency of about ~ 1.3-1.5k?
I think NE225w is close-ish to the listed parameters. 20ish liters and F3 of 40-45Hz depending on exact alignment. They call it a subwoofer, but it's much closer to a woofer in reality, with good midrange performance that is suitable for a controlled directivity 2-way crossed in the 1.5-2k range. SB23NRX 4 ohm may work as well with some EQ massaging.
At that box size / tuning though, you have to make a trade-off on port chuffing or port resonance audibility... Looking at the ASR review of the 708, JBL does not avoid physics, and has resonance around 500 Hz only a few dB down from the woofer. This is the inevitable trade-off of a small ported speaker that plays low.
WO24P has a pretty huge linear breakup peak that you need to worry about suppressing, but it doesn't have too much accompanying harmonic distortion, so it's possible. It has been run in a 2 way. Jeff Bagby & Javad Shadzi designed the "Helios," which was using Satori drivers: WO24P and TW29BNWG beryllium dome in a waveguide.
Personally, I have made a ~20L sealed DSP 2 way using the Scan speak 22W discovery 8" 4 ohm with a SB26ADC in an augerpro waveguide and some EQ to get bass... It plays "low enough loud enough" at monitor volumes. Assuming you are listening to monitors reasonably close in a home environment, sealed is fine. Sealed with DSP avoids the need to find the driver that has the perfect tradeoff to accommodate your design goal, you can find one close-ish, then use the EQ to get to your desired point on the bass trade-off spectrum. You'll find that most well built drivers are very similar bass capability once EQ'd. I want to also try an NE225 / XT1086 + compression driver to compare, but not sure I'll do that. Sometimes my eyes are bigger than my weekend free time.
At that box size / tuning though, you have to make a trade-off on port chuffing or port resonance audibility... Looking at the ASR review of the 708, JBL does not avoid physics, and has resonance around 500 Hz only a few dB down from the woofer. This is the inevitable trade-off of a small ported speaker that plays low.
WO24P has a pretty huge linear breakup peak that you need to worry about suppressing, but it doesn't have too much accompanying harmonic distortion, so it's possible. It has been run in a 2 way. Jeff Bagby & Javad Shadzi designed the "Helios," which was using Satori drivers: WO24P and TW29BNWG beryllium dome in a waveguide.
Personally, I have made a ~20L sealed DSP 2 way using the Scan speak 22W discovery 8" 4 ohm with a SB26ADC in an augerpro waveguide and some EQ to get bass... It plays "low enough loud enough" at monitor volumes. Assuming you are listening to monitors reasonably close in a home environment, sealed is fine. Sealed with DSP avoids the need to find the driver that has the perfect tradeoff to accommodate your design goal, you can find one close-ish, then use the EQ to get to your desired point on the bass trade-off spectrum. You'll find that most well built drivers are very similar bass capability once EQ'd. I want to also try an NE225 / XT1086 + compression driver to compare, but not sure I'll do that. Sometimes my eyes are bigger than my weekend free time.
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Just a quick FWIW that the JBL 708 monitor was the inspiration behind my current speakers, but I went with a Seas H1252-08 for midbass duties. Crossover is around 950Hz-ish. I picked that driver because it has a hard aluminium cone, which pushes all the resonances (like the 500Hz hump you've mentioned on another driver) upwards, outside of the bandwidth of the driver. There's a useful amount of Xmax, but the voice coil is pretty inductive - it would've been nice to have some shorting rings etc in the motor.
Later, I added a second 8" driver close to the floor in a 2.5-way configuration, to improve the upper bass range by reducing floor/ceiling bounce.
These are my current living room speakers, and I suspect I'll be keeping them for a long time.
Chris
Later, I added a second 8" driver close to the floor in a 2.5-way configuration, to improve the upper bass range by reducing floor/ceiling bounce.
These are my current living room speakers, and I suspect I'll be keeping them for a long time.
Chris
I could not disclose the OEM source of the Genelec P26WP-01, too bad. At the moment, there seems to be no other ten-inch woofer then the SB acoustics WO24P-8 that could work a 27/30 liter box. And the Beyma could be used with EQ to shape it, but at what cost?
- The Beyma, is the amount of equalization still feasible? In 27 Liters @fb = 38 Hz, the two PEQs are needed to reach f3 of 43 Hz:
- At first sight, the SB acoustics does seem to need more space (box is tuned to 35 Hz and vent is already looong), but it could just be right for a flat response, given the far field frequency response that HifiCompass published: Satori WO24P-8 | HiFiCompass
Nowadays Genelec should be done by Tymphany, it used to be Peerless or Vifa before, if I am not mistaken?
For active EQ'ing, unfortunately the latest version of WinISD has some serious bugs.
Just to understand the picture a little better.
You're looking for a 8 or 10 inch woofers in combination with a horn or waveguide in around 27 liters?
Freq range will be the same as the JBL monitor, so around 40Hz -3dB ?
Or are you gonna add some subwoofers as well?
For active EQ'ing, unfortunately the latest version of WinISD has some serious bugs.
Just to understand the picture a little better.
You're looking for a 8 or 10 inch woofers in combination with a horn or waveguide in around 27 liters?
Freq range will be the same as the JBL monitor, so around 40Hz -3dB ?
Or are you gonna add some subwoofers as well?
Tell me more, please! I had implemented a 6th order vented assist to a 50 liter box and never did not reach the simulated response that my Faital Pro 12PR320 was supposed to give as per WinISD. In the end I applied more EQ and especially not only slightly above fb, which is in subbass territory, but especially in the 70-200 Hertz region where the respons sacked quite a bit. Is there a better program than WinISD for this or another workaround?
Yes. My preference is a ten inch woofer. I want a wide baffle anyway, the higher displacement is welcome, I can cross lower, match the pattern of the waveguide and directivity is controlled to lower frequencies. 8 inch only if ten inch fails.
The volume of 30 liters (minus amp tray, driver volumes, bracing and sidewall damping) would be a very good target and I figured a f3 of 40Hz wouldn't be to much strain on the woofer and acoustic properties, especially to limit the EQ-induced additional group delay.
That was an early discovery of mine, but someone here suggested that this driver has a nasty resonance which is still in the passband for a two way speaker: https://www.diyaudio.com/forums/multi-way/336739-faital-10rs350-suitable-2-a.html#post5766321
A cheap driver Test Lautsprecherchassis Tiefmitteltoner - Omnes Audio W8 Alu
it goes to 50 Hz in a 20 liter closed cabinet.
it goes to 50 Hz in a 20 liter closed cabinet.
Don't know, I have been using the good old Alpha version for many many years. In the newer version the LT doesn't work well, and I used to have issues with param EQ's.
Any idea about max SPL and budget?
The Dayton RS270-4 for example seems to fit right away.
30 liter tuned @ 30Hz
When going active I would rather use a different woofer, and squeeze in a subwoofer on the back or something (in the same cabinet)
I am coming from a high efficiency approach. I kept digging for opinions and substantiations, but could not overcome the existing disagreements on the importance of (all considering a two way):
The Omnes Audio and Dayton aluminium cone drivers actually look like very good poor man's 8 inch drivers for a small enclosure horn two way. They are said to distort at higher volumes, though. The crossover frequency of 1.2k for the Omnes Audio MW 8 2.0 was derived from climbing LE and falling frequency response, not a problem with an active system. I really cannot understand their distortion graphs Klirrfaktor - Seite 6 and how it compares to the Beyma SM-110/N, whose distortion is given some posts above in absolute numbers.
- Low Mms for midrange reproduction. I mean to remember Earl Geddes did not care, while Zvu had limits in mind, and mabat used the heavy Dayton driver, maybe the one that you suggested. For a ten inch driver I derrived 40g Mms compared to a midrange proven twelve inch woofer. But the disagreement ..
- Papercone or different diaphragm material. Many vow for paper.
- Efficiency. If it is good for the sound. I would not need it for SPL necessarily.
The Omnes Audio and Dayton aluminium cone drivers actually look like very good poor man's 8 inch drivers for a small enclosure horn two way. They are said to distort at higher volumes, though. The crossover frequency of 1.2k for the Omnes Audio MW 8 2.0 was derived from climbing LE and falling frequency response, not a problem with an active system. I really cannot understand their distortion graphs Klirrfaktor - Seite 6 and how it compares to the Beyma SM-110/N, whose distortion is given some posts above in absolute numbers.
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I had an eye on the Sica 10 SR 2,5 CP after I learned that the FaitalPro 12RS350 had issues with a resonance at around 700 Hz. Both drivers are close together concerning TS, but I still wonder if this Sica could be an option. The cone is not very light (Mms is 56), and it is still disputed which role Mms has in midrange quality, but it could be worth trying. Then I found it was used and measured for another project and the cone break up is significantly lower in frequency with these measurements (a bit down): Link. I will use LR4 @ 1.2k and the breakup is so much closer than in official measurements. I would EQ it but this does not mean it is inaudible, right. Do you have advice for me, if this is worth a try at all?
