I'm considering to replace a set of 8" JBL 2118 (one driver is defective) with a set of 6.5" Beyma 6MCF200Nd
The new, now smaller, 6.5" pair should blend with the 15" JBL 2226 low mid woofer (crossed at 850Hz). The treble is covered with a DE250
For different reasons it's rather common to combine 12" & 6.5" and 15" & 8" drivers
Has anyone experience with 15" + 6.5" combinations? For the mids from 850Hz on, it might that the 6.5" has less reach and coverage in comparison with an 8". Therefore the transition from the 15" isn't as seamless with a 6.5", sound becomes "smaller"... or maybe not? My JBL LSR32's have 12" woofer and 5" mids
Any thoughts and technical explanations are welcome
The new, now smaller, 6.5" pair should blend with the 15" JBL 2226 low mid woofer (crossed at 850Hz). The treble is covered with a DE250
For different reasons it's rather common to combine 12" & 6.5" and 15" & 8" drivers
Has anyone experience with 15" + 6.5" combinations? For the mids from 850Hz on, it might that the 6.5" has less reach and coverage in comparison with an 8". Therefore the transition from the 15" isn't as seamless with a 6.5", sound becomes "smaller"... or maybe not? My JBL LSR32's have 12" woofer and 5" mids
Any thoughts and technical explanations are welcome
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No problems doing that, except that you will need to match the sensitivity. That will mean picking a 15 which has low-ish sensitivity and a 6.5 which has high-ish sensitivity. Depending how much baffle step compensation you plan on building in and the crossover point, the 15 may be able to have 3-6dB higher sensitivity than the 6.5.
Ideally, the crossover between the midrange and horn tweeter should produce a smooth polar response. If your horn has a 90-degree horizontal polar pattern, the crossover frequency should be selected to the frequency where the 6.5" midrange polar is -6db at 90-degrees.
A 6.5" midrange will start to beam at a higher frequency than an 8" midrange, and you will need to raise the crossover frequency if you want the smoothest M-T polar response.
The woofer/midrange crossover is no problem. It's the mid and horn polars that will be the bigger issue.
My current test box consists of a 15" crossed to a 6.5" at 600hz.
I've been alternating between a hornless compression driver crossed to the 6.5" midrange at 1.5khz and an Eminence apt-80 crossed at 2.5khz. 48db active slopes all around with delays to achieve semi-linear phase.
Both sound good but I prefer the lower crossover hornless driver. Behaves like a point source with no lobing thus sounding bigger with much less variation at different listening angles.
My current test box consists of a 15" crossed to a 6.5" at 600hz.
I've been alternating between a hornless compression driver crossed to the 6.5" midrange at 1.5khz and an Eminence apt-80 crossed at 2.5khz. 48db active slopes all around with delays to achieve semi-linear phase.
Both sound good but I prefer the lower crossover hornless driver. Behaves like a point source with no lobing thus sounding bigger with much less variation at different listening angles.
Why replace the 2118 with something else? They're not hard to come by, and I think factory recone kits are still available.
I'm also wondering why you were x-ing the MB to the MR so high.
I'm also wondering why you were x-ing the MB to the MR so high.
EAW ( Pro audio stuff ) was quite successful with their FR153Z speaker ( which used a 6.5" mid and a 15" woofer, HF was a compression driver on a circular waveguide ).
- They had at least a couple of these 3-way ( cone-driven mids ) within their catalogues over the years.
- EAW used mostly European manufacturers as their parts suppliers over the years. Typically; RCF, B&C, and once in a while Audax.
That Beyma 6MCF200Nd looks to have some quite nice specs ( it's also not an inexpensive driver over here ).
Have you heard it ?
One comment, if one uses a mid like that up to 4 or 5K you might as well use ( for HF ) a smaller diaphragmed compression driver ( for better transient response ) > assuming sound quality is more important than over-all ruggedness.
🙂
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Thanks Gentlemen
Brett, I actually have a second set of new'ish 2118H (if anyone is interested). I like to try something different. The speakers are a set of JBL 4730A that I like to modify (drivers and front baffle cut-outs, mirroring). The original divers are JBL 2226H crossed at 850Hz to JBL 2118H crossed at 3.5kHz! to JBL 2404H
ATM I like to have the 2226 playing up to 850Hz (650 to 850 Hz range)
My idea so far is crossing the 2226 at about 850Hz into the "new mid-driver" and from about 2kHz into B&C De250 with Faital Pro LTH102 Tractrix (60 x 50 or turned to 50 x 60 )
I also consider the 6.5" AUDAX PR170M0 or the new 8" Beyma 8WR300 as a new mid.
Having the 2226 and the Mid-driver/(PR170M0)+De250-Combi on separate amps might be an option for equal loudness
EAW ( Pro audio stuff ) was quite successful with their FR153Z speaker ( which used a 6.5" mid and a 15" woofer, HF was a compression driver on a circular waveguide ).
- They had at least a couple of these 3-way ( cone-driven mids ) within their catalogues over the years.
- EAW used mostly European manufacturers as their parts suppliers over the years. Typically; RCF, B&C, and once in a while Audax.
That Beyma 6MCF200Nd looks to have some quite nice specs ( it's also not an inexpensive driver over here ).
Have you heard it ?
One comment, if one uses a mid like that up to 4 or 5K you might as well use ( for HF ) a smaller diaphragmed compression driver ( for better transient response ) > assuming sound quality is more important than over-all ruggedness.
🙂
Thanks for the info, fantastic : ) I would have a B&C DE250 for the high frequencies. I could also use the 'left-over' JBL 2404 on top of the DE250 (placed on top of the speaker cab) to make up for the decreasing top end of the DE250 up from 8/10kHz if needed
I have not heard the new Beyma 6MCF200Nd yet. It was a recommendation and I find the specs promising too
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Is there any particular reason for using a closed back midrange other than practicality ?
I always thought of them as inferior in regard to regular pro midranges. It is very hard to absorb the backwave, walls of the driver chamber are always some thin sheet metal and they can not be crossed low enough without a horn. Maybe i'm failing to see some advantage obvious to others.
I always thought of them as inferior in regard to regular pro midranges. It is very hard to absorb the backwave, walls of the driver chamber are always some thin sheet metal and they can not be crossed low enough without a horn. Maybe i'm failing to see some advantage obvious to others.
Zvu,
I do share your bias when seeing closed back mid-rangers.
OTOH, I'm slowly getting past that bias due to the work of the likes of Bill Waslo ( and all his Synergy designs using a Celestion closed-back midrange ) .
DIYSG also use a closed back Eminence 6" midrange in one of their designs.
I imagine that if one thinks the back-cap is likely going to offer problems from induced mechanical resonance > then one can address those with either a separate mid enclosure or plumbers putty .
🙂
I bought the Eminence years ago before I knew better, but it actually works quite well.
The higher end closed back midranges seem to be a different animal with an actual back chamber big enough for low midrange extension and damping material. Very power motors, large heatsink area, large voicecoils. Designed for horns but still have great efficiency without them.
I will be pushing this box hard at times and I'm aiming for very little power compression. Woofers will be fan cooled. The compression driver and midrange should be fine with their inherent efficiency.
Reports on all the highend Italian closed backs have been very positve. They just happen to fit my application well. For home use I would use a wider band mid like the AE TDM series.
The higher end closed back midranges seem to be a different animal with an actual back chamber big enough for low midrange extension and damping material. Very power motors, large heatsink area, large voicecoils. Designed for horns but still have great efficiency without them.
I will be pushing this box hard at times and I'm aiming for very little power compression. Woofers will be fan cooled. The compression driver and midrange should be fine with their inherent efficiency.
Reports on all the highend Italian closed backs have been very positve. They just happen to fit my application well. For home use I would use a wider band mid like the AE TDM series.
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