DIY 2225J, 2445J, 2405 Build Help

[danvprod]

Hi Folks --

I recently acquired the following JBL components and am hoping to put together a new playback system. Looking for some help and guidance here, I've been reading up on some of the great systems you folks have put together and have been inspired.

The JBL Components I have to work with are:
2 2225J 15" Woofers
2 2445J 2" Compression Drivers
2 2405 Alnico Slotted Tweeters

In addition, I have 2 250 Hz Tractrix Horns -- the stereo lab ones -- https://www.stereo-lab.de/EN/spheric...trix-horn.html. I'll mount the 2445Js in there.

As far as my current system. I mainly listen to vinyl. I have a Decware preamp, and two Monoblock 300b tube amps, a Rotel 1050b SS amp and a miniDSP to do the active x-over. I do plan on bi-amping here. The Rotel for the 15" drivers, and the 300b amps for the Compression drivers and super tweeters. For the super tweeter, it came with a 12 dB/octave x-over at 10k. I may just let the feed off the tube amp as well, or perhaps get a t-amp to power these so I have some control of the 'sparkle'.

So my big system design questions are:
1) What enclosure to build for the woofers? JBL recommends 4 cu ft BR tuned to 40 Hz. Is this a good plan?
2) Should I consider a folded bass horn? Or will that not play up high enough to integrate with the 2" midrange?
3) What frequency to cross the 15" to the 2"? I should be at least an octave above the cutoff of the horn, correct? So I am looking at 500-800 Hz?

Any help and guidance would be appreciated. I will update this thread with pics and measurements as I build this system up. Thanks!

[more10]

JBL 4530 cabs. If you get Radian diaphragms for the 2445 they will go down to 300 Hz. You will need a miniDSP HD, the small ones are not good enough. The miniDSP can handle the uneven frequency response of the 4530.

If you mount the tractrix horns on a baffle they will go as low as 400 I believe. If you have the specification it is easy to find out the cutoff using Hornresp.

This will be a great system!

[danvprod]

Thank you!

My other thought re: DSP would be to get a DriveRack DBX PA+, but the MiniDSP HD is a good idea as well.

For the horns, here are the specs:
2 in throat, cf 250 Hz. Length 40cm/15.8 in/ Outer diameter 45 cm/17.7 in, insulation thickness 1cm, Weight 3.6 kg. Made of artificial granite.

Is this the MiniDSP that you are thinking of?
http://www.minidsp.com/products/mini...inidsp-4x10-hd

I did find a nice replica project of the 4530s that you recommend:
http://www.audiocostruzioni.com/r_s/...0/jbl-4530.htm

You think scoops like this will perform better than the BR enclosure?
What are the frequency issues that I would have to iron out with DSP?

Thanks!
Dan

[more10]

Since the scoops are backloaded you will have cancellations from the front side of the driver. It can be seen in the spec sheet, the first at 150 hz. You will also have two impulses, one from the front side, one from the horn. The horn has good slam though. I preffer a horn over a BR any day of the year because I am a bass junkie :-). I would buy backoaded horns, not build them. Front loaded horns are worth building.

The tractrix horn will beam at higher frequencies. A rule of thumb is that a horn doesn't work properly over more than 3 octaves. Your horn will work well from 400 to 2500 Hz using this rule of thumb. If I where you I would swap the slot tweeter for a bullet or put in another 1500 Hz tractrix with a one inch driver.

This is the minidsp I was referring to.

[danvprod]

Thank @more10. I do see that cancellation in the frequency response. I did not realize that was the behavior of rear horns. I'll keep an eye out for the cabs. I may in the short term build some 3-4 cu ft. boxes just so I can start listening.

Thanks for the suggestions on the frequency range and beaming on the 2". Good idea to cross to a 1" driver > 2500Hz. That may have to come in the future. I've seen some other nice wood waveguides that are a bit smaller to work > 3k.

I really like this system, and may do something like this to start:
http://www.audioheritage.org/vbullet...-project/page4

[more10]

The Edgar midbass horn works well I believe. Look for 2220 and 2227 for these, 2225 are useable but not as good. But you will need something below it.

[ivica]

Thank @more10. I do see that cancellation in the frequency response. I did not realize that was the behavior of rear horns. I'll keep an eye out for the cabs. I may in the short term build some 3-4 cu ft. boxes just so I can start listening.

Thanks for the suggestions on the frequency range and beaming on the 2". Good idea to cross to a 1" driver > 2500Hz. That may have to come in the future. I've seen some other nice wood waveguides that are a bit smaller to work > 3k.

I really like this system, and may do something like this to start:
http://www.audioheritage.org/vbullet...-project/page4

Hi danvprod,

Owing to the JBL data for 2225H, it seems that it can be used almost up to 1kHz, so I would suggest you to
make 5ft3 BR box, and apply crossover around 700~800Hz. I believe that 2445 can be used up to about 9kHz, and the rest of the response would be 2405 duty.

Regards
Ivica

[danvprod]

Here is the boxes I think I am going to build for the 2225s. All look good?

[Lee in Montreal]

The 2445 compressor is very efficient. Would you consider using TWO 2225 woofers per side? As suggested, I would up the individual volume to 5cft if possible to push the bottom end. That would be 10cft for two woofers. With two woofers per side, you gain 3db because you added a driver and 3 more db from the coupling. That would be nice. You can do a 10cft enclosure from a single sheet of 4'x8'

Think roughly a 35" wide x 23-1/2" tall x 23-1/2" deep = 10 internal cft

Also, you will not get deep bass from the 2225. NO matter what. So in order to boost the audible bass, I would perhaps tune a tad bit higher. Did you try 45Hz?

[danvprod]

Thanks for the suggestion. Unfortunately I don't think I can spare two 10 cu ft. enclosures in my listening space. Here is my listening space and current open baffle speakers that are going away. The horns and base cabs will go between my rack. I have a closest to the right of my right speaker, which limits the width I can put in there. About 24" is the max.

Good idea about tuning to 45Hz. I will try modeling that.

[Val]

The JBL Components I have to work with are:
2 2225J 15" Woofers
2 2445J 2" Compression Drivers
2 2405 Alnico Slotted Tweeters

In addition, I have 2 250 Hz Tractrix Horns

You have a good set of components and this project sounds like it has a lot of potential. I agree with Ivica's suggested 2225 crossover point of 700-800. The lower the crossover point for the 2445, the more honk in the horn. So it think you want to run the 2225 as high as you can as long as it sounds good. This will avoid the 2445 honky range. Have you considered a smith horn for the 2445 instead of the Tractrix for a warmer sound and wider dispersion?

Good luck with this project!

[ivica]

You have a good set of components and this project sounds like it has a lot of potential. I agree with Ivica's suggested 2225 crossover point of 700-800. The lower the crossover point for the 2445, the more honk in the horn. So it think you want to run the 2225 as high as you can as long as it sounds good. This will avoid the 2445 honky range. Have you considered a smith horn for the 2445 instead of the Tractrix for a warmer sound and wider dispersion?

Good luck with this project!

If 2445 used over 800Hz, for home listening levels, may be horn-combo [ HL93] == 2311+2308 can be candidates, too.
http://www.audioheritage.org/vbullet...l=1#post227207


Regards
Ivica

[danvprod]

Progress...

Thanks to some vacation time from work I was able to bang out the bass cabinets this past weekend, yesterday and today. I just was so excited to see how everything sounded. I will finish up the cabinets once I get everything built and nailed down system-wise.

Cabinet design went pretty well, construction was a bit challenging. I've not built anything this big before. I've also not worked with MDF much before. But I was happy with the way that the subwoofer builder/boxnotes construction scheme and instructions went. Dealing with the 1.5" baffle and the Jasper jig was a challenge as well.

Note to self, buy a right angle jig for my drill for next time so that all of my driver holes and port guide holes are straight. Lesson learned. Also 4" PVC is a challenge to cut with just a back saw. Built the cabs with just a circular saw, router, nail gun, drill/driver, brad nailer and some clamps. Rest was hand tools. Not perfect, but came out better than I expected. A mitre saw would have been helpful for the braces and whatnot, but I was able to manage with a mitre box.

For some reason, the cab came out a bit smaller than I expected. Only about 4 cu ft after accounting for bracing, ports and the driver. Ports are tuned to about 44 or 45 Hz, depending on if you count the round over in the front. I've not measured the impedance yet to verify the resonance. Wired everything up and made sure everything was working -- it was.

Just did a quick setup on the MiniDSP with a 800 Hz LR4 x-over point. Wow! Dynamics and dynamic range. Unlike anything I've heard before. I have about 20 dB more headroom vs. my previous setup (which is to be expected, given the sensitivity difference in the components).

Pretty heavy in the midrange currently from the 15". I suspect after I line the cab with some fiberglass, that will help. Ended up just shelving it down a bit in the mini DSP. I'll make some more measurements later this week when I have some more time. First impressions is that this system has a lot of potential!

Next on the build list is a bracket to help stabilize the compression drivers, and some way to mount the super tweeters so they clear the midrange horns. Any ideas?

Here are some quick shots:

[Lee in Montreal]

Good work. In the Spring, you can sand the cabinets a bit more and slightly round off all the corners, then paint them. I am looking at the woofers. Are they 2225 or 2226? The long slanted tinsells tell me they are 2226. Or are they aftermarket recones? ;-)

Yes. You probably have a generous midrange. Especially with a smaller enclosure. You can shelf the woofer between 80 and 100Hz, either with 6 or 12db low pass filter depending on the bass you like. All combinations are worth trying.

[danvprod]

Hi Lee --

Thank you very much. Yes, I am planning on finishing up the enclosures once it gets a bit warmer. They do need some sanding and TLC, but they will work for now. Yes, the woofers are 2226Js. The seller had thought they were 2225, but when they arrived they were 2226, which I was pleasantly happy about.

Working on some measurements right now, good idea on the lp filter. I will give that a try.