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Jim Rogers JR149 DIY build

I am leaning towards the Monacor SPH-145HQ / DT-19SU combination. Apart from anything else there is a crossover design avaviable. But it's this I really need some help with - some elements of it I understand and others I don't. I should say at this point I was, many years ago, an electronics engineer dealing with sophisticated control systems. The crossover looks like this.
Monacor_SPH-145HQ_Crossover by Robin Martin, on Flickr

For the Bas/midrange SPG-145 circuit
L2 and C2 form a 2nd order filter. But what is R2 for?
And C1, L1 and R1 I don't understand at all.

C1, L1 and R1 are for baffle step adjustment: basically at the low frequencies the sound "wraps" around the box. At a certain level the speakers start to beam and only radiate forwards. The result is loss of bass/ lower end of the spectrum and where the roll off starts depends on the width of the baffle. How much loss there is depends on how far out from the wall they are, if not implemented the speakers will sound like not having enough bass.

R2 is to tailor the phase of the driver at crossover frequency - if the two drivers are out of phase then strange things start to happen, "lobing" or even cancellation. Lobing means stronger in certain direction, you want the main lobe to be straight forward, not pointing at the floor or to the sky.

PS Kudos on the job with the car. I once started on something similar but health intervened and I had to give up.

PS2 I would give serious thought towards phoning Wilmslow Audio and see if they'll sell you the Dolce without cabinet but with crossover. It would surprise me if they said no.
 
back in the mid seventies, I was trying to use Kef B110s and T27s in a small box (I suppose similar to the BBC 3/5whatevers). I could not get them to work with any crossover within reach of my pocket (recently married, mortgage around neck, etc, then kids) until I tried the one for a KEF 104AB published in a HiFi Year Book. It worked extremely well even though the bass/mid range was for a B200. I could get within a foot of the 'speaker and still not tell I was listening to two drive units! Might be worth looking at.
 
back in the mid seventies, I was trying to use Kef B110s and T27s in a small box (I suppose similar to the BBC 3/5whatevers). I could not get them to work with any crossover within reach of my pocket (recently married, mortgage around neck, etc, then kids) until I tried the one for a KEF 104AB published in a HiFi Year Book. It worked extremely well even though the bass/mid range was for a B200. I could get within a foot of the 'speaker and still not tell I was listening to two drive units! Might be worth looking at.

Ypu cannot take a crossover and expect it to work with other drivers. Any change in driver requires a change in crossover. Tweeters are relative simple but mid/bass is darn hard.
 
Especially getting the baffle step correction right. No software out there is designed for this exotic cabinet shape and remember that the JR149 was voiced for a near wall mounting.
Basically you need to mount drive units in the cabinet, at your target wall spacing and measure to see what you need to correct
 
Did the JR149 use selected B110s, or just anything KEF sent them?
We don't think so, but variations have been spotted in crossover values, which might be an attempt to fix sensitivity variations between the two drivers.
The B110 had severe bextrene "honk", which the original crossover compensates. A modern driver won't need this.
 
I’d still love to know exactly what the BBC’s selection criteria for B110s was. I’ve never seen any graph showing what response or precise spec they were seeking, though I understand it was right at one end of the B110 tolerance bell-curve. My assumption is the JR149, being a later design, was designed around the normal B110 spec.
 
Does it have to be a sealed enclosure?

Finding a reasonably priced 5" midbass driver that will produce enough bass in a sealed box is the challenge. The Monacor SPH-135AD isn't bad in this respect, but the frequency response in the datasheet, although not easy to read, looks like it has a peak starting around 1.5khz and up. According to Willys-hifi, it's used in the Sterling Broadcast LS3/5a, and the bump at 2khz shows in the Stereophile measurements.

You could buy a pair of JPW mini or Gold monitors and remove the Peerless KO130 woofers. They were used with a very simple crossover, so should be quite linear in frequency response. Coupled with a nice tweeter, they could well make a surprisingly good sound.
 
I believe the JR149 used the B110 SP1057 (same one as used in the 11 Ohm LS3/5A). The 15 Ohm LS3/5A used the B110 SP1003 which had a nasty discrepancy higher up that had to be tuned out. Always only B110 is mentioned without specifying which one, there are several versions and B110 only refers to the size of the driver.

I would not buy any old drivers as the surround dries out (hardens) over time or disintegrates, in any case old ones are not up to specification after ten years or so.
 
I believe the JR149 used the B110 SP1057 (same one as used in the 11 Ohm LS3/5A). The 15 Ohm LS3/5A used the B110 SP1003 which had a nasty discrepancy higher up that had to be tuned out. Always only B110 is mentioned without specifying which one, there are several versions and B110 only refers to the size of the driver.

I would not buy any old drivers as the surround dries out (hardens) over time or disintegrates, in any case old ones are not up to specification after ten years or so.

Are you sure the JR149 used the SP1057 - According to TonyL, it used the SP1003 - (post #3) https://pinkfishmedia.net/forum/threads/just-thinking-kans.161566/

Modelled using the datasheet, the SP1057 bass rolls off very early in a sealed enclosure. That was certainly the case with my mk2 Kans. The SP1057 really needs a port to produce any bass.

Grey line, ported, Black line, sealed

9Kejrhx.gif


And compared to the Peerless KO130 - Grey line, Peerless KO130. Black line, Kef B110 SP1057. The area between 70hz and 200hz is far more important than the bit between 20hz and 50hz. Subjectively, My old JPW gold monitors had much more bass than my Linn Kan mk2.

HNxFfo7.gif
 
The JR149 crossover has a lot of BSC for a speaker intended to be a foot or so from the wall
70 Hz is a 4.3m wavelength, 200 Hz is 1.5m, so wall interaction would be important
 
Here's a comparison of the SP1057 and SP1003 in the same sized sealed box, with the same power applied. Grey is the SP1057 (Linn Kan woofer)

Z3fLoHg.gif
 
Over the years Ive tried many of the 'alternative' drivers for the JR149 in the original enclosure but nothing has the same voice as the B110 IMO. The Falcon FB110 replacement is a great product as it sounds as the original KEF unit. The original tweeter however IMO is prime for a upgrade and great rewards can be had here. The T27 is a tad harsh and I upgraded to a SEAS 19TTF after a long conversation with Falcon at the time (10 years ago!!)

I now run them active via DSP, with DSP you can tweak the speaker to sum correctly and null all the bad bits. This truly is indulgent for a pair of 40+ year old speakers worth £300 but they are stunning near field monitors.

MelD4eu5ib7fb8HU0SMeLlxNq65iI0s9Vt2gcO5o_cOFqdWAgeG5if6_1nKQD9VpsFGdknLp9lpB3MwPsi-zlINAMRB5aJk91nZ20VtXsnvvQkTCwHTyhYG0iDhaYNacyAGkvK3i2K7Zk0yfdOXqKJd2XZQ8qCGizrwg8Hod7AZ28KdXZ6MFKtKLwxX3PzdhHG2sduuwf746rxC5XUza6TAdg1EqS6K0t7tIGDPSAqnfaWLWlb14TeAjkpMDSscaAiDmSOneUZJZc4LXg0wUogg2sv0sKYYu8L-SVUsY_RHY49nMO6Dp9wm9lxwI9r3MrnmCR44qe9GYvRseYNLe_rH20UD0d9Q8lThEEgiRWQZOhQNzA6OAbqTbTeX2bpG_aW-zefvBS4XjEldPqelRIxSomPGlvLd6RXq4xIhnsSMx9DX1YpzynhBMY7IMOgJbq1dY5U6uhB45ccdnhdSuovghvphOyMvA1KtLSJHQnQQ-sXdY_aloJSFGiUjI6a8pT6fauunsQRNbgsMyiICWBxp7lpRl7MkyGj3upbA5R7fjVOyw9rWcQ9fVJfi_Q9l96WeYlX3Yc22f95wwC446QI3w4XWs8PYDvon35DVXMo3wSnGa-A2Q5Ab_UeamLWgofxdKxVr9jCzpzF89c13EvfoSjVAafM81oeN4u41N-Zo5ZaRwwu9ybjFEgR5q8WSD5yfBet8aNY8IXstVG9wDM7fN_RTKcIEj_vYkmMvl608ii9EW42mXXSk9x-nS-g=w832-h836-no


The Monacor SPH135 is not quite a straight replacement for the B110 as you will find the mounting holes and baffle cut out are slightly different. But this is a superb driver is used in a bespoke cabinet. Avondale used 2 of them in a later model of the Revaluation IIs replacing the KEF B110.

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Over the years Ive tried many of the 'alternative' drivers for the JR149 in the original enclosure but nothing has the same voice as the B110 IMO.
....
The Monacor SPH135 is not quite a straight replacement for the B110 as you will find the mounting holes and baffle cut out are slightly different. But this is a superb driver is used in a bespoke cabinet. Avondale used 2 of them in a later model of the Revaluation IIs replacing the KEF B110.
....
zpZi1SRRKC604k2gvg1fC5UXnNC647CRZoUk53Rm_QooxXhEW_xj9yXB23VAza0CdN-Enhhj2OaGtoWssSIkQeWLxd5-V7yPtzI1mb9_iqVnwJa2WvIwv2kc9LlQg7_K_IE2jMHHi0z6EwqdUPhCvE92GQxbkmXy4hbp4pamIZjGvR9bxEj_zGCs6xcm_XBO3s9Rcvme3gFFvfENKftY7YgEddsZFl3oL7lqz9SrXji4cZ2PG25lZ3ZxLb2vByF_tMEbKGzDURR21vAJExQMdqQbJosbQTZfeU3XWFMjjnZrBBmJouE-UYs3PJf9lmUye2izvH_9nGVD6Be6ke9aduEmzDeOh1Cf13hWSOiHzsEab_Ta3L8mq8HQJyrngagRkWOcBxNRm3FKq4uQYEJ7wRRlrL7rEW6pOvm6ZaC5VphfM7ykzwH3i0MGVU4kyTIrebN8I62VhwYfAqiTzojqD8JzBZrDXUhUG9mubuD3jj1jWk2LGRmNdia8eym8jc94SVrmr9GMV3wkU82Dvz9fkNRV-dVgYyFSmkfwWlUydUQwTBq_zvBIje0LkdIaqbWVAvQbr_xnMJI99UwYgfzCX7yuSxE2EZ5Q_TaaGtpF44RzIyFOvZXX-lMg_Je0-k48LiVNU6C7QVyjEG0Iw74Hu6GfOlLn3Uvulwjz4TO5weIGeKulemkk0wFVhTYH_O4tJUEL3PQ37ZoG4XFO7osyFAR0wqxyv5S1IsryMvCrs2FicMW-8vmtEgKihjG3DPsnuo9y28-J2lJHBWyHmFou_YktVV1g_s5mGPJBFSSxeTZMmdyI-8t9uaaTp_ICWitKWJXaTUpOzS83963q2MPN05RYvmLoVCk7eSdCyZoVMZGLjlKvzP9yqpKQSUJW5vWUtZTzBY2qEEMuAmdlhVHhyUuqDJh3MkvkEz-txNq4=w627-h836-no

Wilmslow Audio recommends Monacor SPH-130.

The relative unknown Monacor SPH-145HQ is the SPH130 replacement and is highly regarded (and under rated). It has different specifications and will need a redesign of the crossover and will not fit without surgery to the cabinet. (Monacor LS5/19)
 
You cannot take a crossover and expect it to work with other drivers. Any change in driver requires a change in crossover. Tweeters are relative simple but mid/bass is darn hard.

yep, understood, and agree, but at the time I was developing a complex crossover for a TL loudspeaker, and had lots of components. I put together the 104aB crossover, and it seemed to work a treat without messing about with it. Quite an eye opener, or should that be ear opener. Sometimes serendipity 'appens.
 
Progress is made. I have built the crossovers. A lightly modified version of that used in the Monacor LS 5/19 as previously mentioned. And before anyone comments I know the enclosure I am building is different to the Monacor LS 5/19 and will therefore have an effect on the crossover behavior. But to be honest my hearing is not that accute!
And I have obtained the driver units. Most of the crossover components and drivers came from Wilmslow Audio. Strangly enough I used Wilmslow when I built my previous speakers some 25 years ago!
ATM still struggeling a bit with building the JR149 like tubes but I am getting closer to something that would be acceptable to go in my lounge!

speaker components by Robin Martin, on Flickr

Robin
 


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