Hi,
Iam a DIY nerd and i wish rebuild convert and old pair of pro speakers into an open baffle audiophile speaker.
i am doing this on the cheap and i am trying to get used parts.
I have seen those old speakers online with 4 JBL2225H in them and 2 selenium dh200e. I think that might be the ideal system for me but i wanted to ask opinions first on the forum.
the plan would be to recone the JBL2225H to JBL2235H as i have seen a lot people doing that. And maybe upgrade the horn with a 12 inch full range speaker.
Let me know if you have an concerns about this ?
The aim is to get to this result...
Iam a DIY nerd and i wish rebuild convert and old pair of pro speakers into an open baffle audiophile speaker.
i am doing this on the cheap and i am trying to get used parts.
I have seen those old speakers online with 4 JBL2225H in them and 2 selenium dh200e. I think that might be the ideal system for me but i wanted to ask opinions first on the forum.
the plan would be to recone the JBL2225H to JBL2235H as i have seen a lot people doing that. And maybe upgrade the horn with a 12 inch full range speaker.
Let me know if you have an concerns about this ?
The aim is to get to this result...
The main difference between 2225H and 2235H is the mass ring which adds 35 g to Mms (and additional 15 g from slightly higher coil etc). There is also foam surround, but it's not going to matter much in OB application. Bottom line, EQ will render 80% of the difference moot.
Anyway, both 2225 and 2235 are far from ideal for dipole application due to their smallish Xmax: pole height is 8 mm, winding height is 19 mm for 2235H and 16 mm for 2225H, leaving us with ±5.5 and ±4 mm.
I wouldn't seek old PA boxes for OB. Used (quality) car subwoofers suit cheapskate dipole much better, as they have 2 to 3 times Xmax compared to PA drivers and suitably high Qts from the start.
The Eminence Alpha-15A only has xmax of 3.8mm and it has been used with much success in OB.
Jeremy
Jeremy
It really depends on definition of "much sucess". Sure, it will play music, but dynamic capability and bass depth will be lacking. Let's presume we want 100 db undistorted peak level at 40 Hz at 2 m. Open baffle will have about 8 dB dipole loss compared to sealed box, so equivalent sealed box SPL will be 108 dB at 2 m, or 114 dB at 1 m. This will require 4 mm of one-way excursion from 4x15" drivers.
Well, less than I thought. Sure it will gargle and die under assault of Perturbator extra deep synthetic bass, but it is adequate for bass guitar and double bass.
Well, less than I thought. Sure it will gargle and die under assault of Perturbator extra deep synthetic bass, but it is adequate for bass guitar and double bass.
don't see point in di pole or d' appolito arrangement.
junk vertical and no bass, what every hifi should be.
need much wider baffle and then put high frequency
at ear level.
but very nice idea to find and use old JBL
is fun.
junk vertical and no bass, what every hifi should be.
need much wider baffle and then put high frequency
at ear level.
but very nice idea to find and use old JBL
is fun.
Thanks for all the inputs on this threads, you are bringing a lot of good points.
My aim is to get as close as possible to the Pure audio project Trio speakers.
They are using a woofer called OB-A15neo build by eminence, it is based on the Eminence Alpha15a.
Here is the info on this:
I am wondering if the JBL2235H would be a good enough replacement ? here are the specifications
There seem to be a big difference in the lower end, but it might be ok ?
My aim is to get as close as possible to the Pure audio project Trio speakers.
They are using a woofer called OB-A15neo build by eminence, it is based on the Eminence Alpha15a.
Here is the info on this:
I am wondering if the JBL2235H would be a good enough replacement ? here are the specifications
There seem to be a big difference in the lower end, but it might be ok ?
Of cource, OB-A15 is specifically designed for open baffle (hence OB in the model index), so it has Qts of 0.72, which gives it flat response in infinite baffle down to Fs. Also that measurement is clearly taken in a small/cheap anechoic room, so measured response is valid only to 100-150 Hz or so.
2235H is designed for bass reflex application (Qts 0.25), so in an infinite baffle it will have a drooping response.
Generally speaking, having Q of 0.707 provides flat response, lower Q results in drooping response, higher Q results in a peak at Fs. 0.6..0.9 can be considered good range for OB.
Those difference are somewhat moot when using sufficiently powerful amplifier, as any respone can be EQd to flat. Xmax becomes a paramount parameter.
Actual geometric Xmax - (winding width-pole height)/2 - is smaller in both JBL drivers, being 5.5 mm for 2235 and 4 mm in 2225.
8.5 mm is a somewhat inflated marketing statement, defined either in some arbitrary way like BL dropping by 20%, or by driver reaching 10% of distortion or even as geometric Xmax+20% (obviously not the case here).
8.5 mm is a somewhat inflated marketing statement, defined either in some arbitrary way like BL dropping by 20%, or by driver reaching 10% of distortion or even as geometric Xmax+20% (obviously not the case here).