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Multi-Way Conventional loudspeakers with crossovers

4 Way Mid Bass Driver
4 Way Mid Bass Driver
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Old 20th December 2016, 08:31 PM   #1
crash999 is offline crash999
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Default 4 Way Mid Bass Driver

I have constructed a 4 way system using JBL speakers, JBL 2245, JBL 2123, JBL 2405, and JBL 2405.
With the recent change of DAC to a Level 4 Lampizator the sound is good but I feel the JBL 2123 is the weak link in the chain.
Iím looking for mid Bass drivers to cross from the 2245s at 160Hz to the JBL 2450s at 800Hz.
These crossover points are flexible but I donít want the JBL 2450 going lower than 800Hz they are on an E-JMLC 300 horn.
The driver could be 12Ē or 10Ē.
After trawling through the Forums this is my short list:
Beyma 12P80ND
JBL 2250J
PHL 3451
Volt BM2500.5
Same old problem with a limited budget I need to get it right I like the idea of the Beyma it gets consistent good reviews but I have never heard one.
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Old 20th December 2016, 09:15 PM   #2
scholl is offline scholl  United States
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Hi

What size room are these in?

How are they stacked up?

Scott
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Old 21st December 2016, 02:03 AM   #3
Brett is offline Brett
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My experience with the 2123 is that they're excellent; selling my 4 was one of the few regret sales I've made. I never ran them below 250-300Hz though.
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Old 21st December 2016, 07:20 AM   #4
crash999 is offline crash999
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Scott the room I use is a dedicated listening room on the upper floor of an extension to the house measuring 20 feet by 35 feet. It has a wall across at 20 feet with an 8x8 foot opening and goes right up in the roof space. The roof has 40 tons of stone slates on it. The speakers fire across the room 20 x 20 feet with the roof dropping down above almost forming a large horn.
The speakers are aligned vertically as tight as possible without allowing the E-JMLC to impede on the JBL 2123.
I love the sound of the two JBL 2245s I cross them at 260Hz up to the JBL 2123s.
Following Brett’s comments I might try the 2123s in a 10L ported box and see if that improves the sound.
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Old 21st December 2016, 07:48 AM   #5
mayhem13 is offline mayhem13  United States
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From your posts, it sounds like you're having an issue with lower midbass impact?.....which might have more to do with your room and XO than it does with the drivers. Do you have a nearfield bass response measure to share?
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Old 21st December 2016, 08:27 AM   #6
crash999 is offline crash999
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Crossover is Marchand XM 44 3 way. I run the 2245s off a Crown XLS 2500 using the internal crossover.
The JBL 2123 is in a 7 Litre sealed box.
The graphs on the Lansing Heritage site show the bass dropping off.
Field Guide to the JBL 10 inch Midbass driver 2121 2122 2123

The JBL 4716 uses them in a ported box down to 100 Hz I must try it before changing speakers them.
I have very little measuring equipment or software in fact thats where I also need help.
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Old 21st December 2016, 10:43 AM   #7
LineSource is offline LineSource  United States
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The JBL 2123H is an excellent 10" midbass. The JBL 2012H is a newer upgrade design with a larger Xmax for your 18" woofer demands, both are excellent.

BUT...
You use the 36" wide E-JMLC 300 horn driven by the 2450H 2" compression driver(with a 4" titanium dome) which would have a better marriage to a 12" - 15" midbass. The E-JMLC 300 is often used with special 15" midbass drivers(GPA-416, AES-TD15M) with 800Hz crossovers.

SO...
My favorite is the sealed box AES TD15M. Very low Le. Flat at 800Hz. Easy 160Hz sealed bass.

ALSO...crossovers are very important...
Your woofer-mid crossover will need to handle baffle step and room effects.
You need both mid-tweet crossovers, plus time-delay(alignment) support which could consume the XM44.
Your super tweeter might need to use a passive crossover.

XM44 Electronic Crossover Network
"Optional plug-in modules are also available for special features like delay, bass boost(Linkwitz transform), baffle step compensation and notch filter. "

A great deal to figure out before you spend money.
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Old 21st December 2016, 01:35 PM   #8
crash999 is offline crash999
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AES TD15M nice driver but expensive and I could find none in the UK.
Just too much for my budget, all my drivers are second hand.
For sound wave, wavelength (λ) in Air is nearly 2.145 meter at 160 hz so could I eliminate baffle step by making the baffle say .5 meters wide?
Possibly the Beyma 12P80ND would be a match for the system. another problem is the vertical height of the stack needs to be kept within a reasonable size.
I Time Align by physically aligning the drivers using the crossover points as a reference. I find the simpler the system the nicer it sounds.
I will try the cheapest solution, a 10 litre ported box for the JBL 2123 and see how that sounds.
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Old 21st December 2016, 05:31 PM   #9
POOH is offline POOH  United States
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The 2123 is weak in the low range unless horn loaded. As a direct radiator they uaslly start to turn on at 350 cycles.

I highly recommend the JBL 2204 - I have a mint pair if you are interested. I'm in USA - The 2204 is even better for hifi low mid than the newer JBL drivers.

https://www.google.com/url?sa=t&rct=...42059868,d.amc
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Old 21st December 2016, 07:11 PM   #10
mitchba is offline mitchba  Canada
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Agree with a few posters... before changing anything you may want to baseline what you have now. Purchase a measurement mic and use REW or other donationware software to measure the frequency response of your system. This will allow you optimize levels and XO points to yield the smoothest frequency response.

Next look at the time alignment of drivers. Note the Crown XLS series of amplifiers with DSP introduces a measured delay of ~1.25 milliseconds. Depending on the other amps in your setup may mean that the sound from the woofers are delayed by a millisecond, which is the same as if your woofers were physically a foot behind the rest of your speakers. This is going to have an impact on sound quality and may be what you are hearing, in addition to above.

Check out these time alignment measurements on a 2 way JBL 4722 with a Crown XLS 1502 running the woofers: Just purchased a pair of JBL 4722n speakers. - Page 198 - AVS Forum | Home Theater Discussions And Reviews This will give you a sense of what is being described above and how it may impact your 4 way system.
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