4 Way Mid Bass Driver

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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.
I’m 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 don’t want the JBL 2450 going lower than 800Hz they are on an E-JMLC 300 horn.
The driver could be 12” or 10”.
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
I’m looking for mid Bass drivers to cross from the 2245s at 160Hz to the JBL 2450s at 800Hz.
I like the idea of the Beyma 12P80Nd it gets consistent good reviews but I have never heard one.

I believe that the best midrange sound comes from a sealed box with a cleverly shaped rear volume, and clever use of absorption material. (attached tapered tube sim).

In a sealed box the -F3 of the Beyma 12P80Nd_ver2 varies from 210-250Hz. A -F3 ~140Hz-160Hz might be better to crossover and baffle step to the 18" JBL 2245 in large bass cabinets. You would need to put the 12P80Nd in a ported box to achieve an -F3 in the 140-160Hz.
 

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The 15" Beyma 15P80Nd_version3 models to -F3 ~140Hz in a 1cuft sealed box, and shows a flat SPL past 1kHz in the Beyma datasheet. A center-horn ear level of ~42" = 18" woof + 15" mid + 6.5" horn center. The 15P80Nd_v3 uses the same motor, cone construction, and suspension as the 12P80Nd_v2. Beyma's SPL curves for the 15P80Nd_v3 look flat over the desired 160-800Hz region.

The 15P80Nd was used in the European "inConcert Miles" diy speaker, crossed to the Beyma TPL150H, with easy to find measurements and reviews.
 
Following Brett’s comments I might try the 2123s in a 10L ported box and see if that improves the sound.
I never ran them ported. I don't like ported midranges; IMO if you need to add a port to get the desired response, you've picked the wrong driver.

I disagree with the title of the AH thread; I never considered the 2123 as a midbass, but a pure midrange.

All my mids use a variation of the B&W tapered tube rear enclosure like LS mentioned.
 
Looking at the specs for the 2123, agreed...., not a midbass at all really and given its height in a stack a REAL problem with floor bounce cancellation right in the middle of where this driver needs the most bottom end help.

12-15" sealed midbass is where it's at between an 18" sub and a 2" CD.
 
The reason I like this forum is the expertise a basic DIY person has access to.
This is what I have so far picture on Lansing Heritage Forum site:
Work in Progress - My Photo Gallery
I must admit if I was going up to a 15" then I would try one of the JBL units some have been getting very good reviews.
Thanks for the info on the Crown amp I have been Time Aligning Physically and not noticed the delay you mention but it is only a crude method I use. I put a tone at the crossover point then move the speakers either max or min depending on if I have reversed one of the speakers using a Db meter.
At the moment I cross the JBL 2245/JBL 2123 at 260Hz. The JBL 2245 can still sound good at this frequency but I dont think its ideal. Yes the graphs show the JBL 2123 falling off rapidly in the bass region.
I have 160Hz cards for the Marchand XM 44 which is why that's the target.
 
Sounds like a fun setup.

I found 12s and 15s used from 60hz to at least 300hz positioned close to the floor give a satisfying sound in most rooms and outside. Lifting the bass off of the floor gives a suck out somewhere between 100 and 200 hz. Good old Alison proved that in the 70s. YMMV
 
The fact that the 2123H sits in such a small baffle might not help here.
Your crossover frequency is probably right were the baffle step takes place, making it difficult to measure and build an adequate crossover (which would of course require non textbook filters and EQs, which most probably implies a digital crossover, at least during the design stage)
 
P-Audio 12"

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.
I’m looking for mid Bass drivers to cross from the 2245s at 160Hz to the JBL 2450s at 800Hz.
>snip<

Alternative Candidate:

SD12-1000EL

About $200 USD

Regards,

WHG
 

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