JBL 4645C

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JBL 4645C

Post by Music Lover » 2016-05-21 22:51

We need a thread for the sub, some of the 3677 owners intend buying.
Personally I'm waiting on delivery date confirmation.

Stay tuned...
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Re: JBL 4645C

Post by fatjulio » 2016-05-22 00:09

I was looking at the JBL subs, and trying to work out the differences between the models. This is the top one, is there much difference to the lower models? The specs don't give away much.
What crossover solution are you going to be using?

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Re: JBL 4645C

Post by Music Lover » 2016-05-22 10:15

It's a Xover from the speaker designer Ingvar Öhman, the man behind INO and Guru.
http://guruaudio.com

short interview
https://www.youtube.com/watch?v=52fFfHHRj5o
The speaker he mentioned in the video is INO Pi60, that later expanded into many INO models and finally went commercial as Guru.
The filter I intend using is really a INO subwoofer filter, specially designed for INO speakers. So not a commercial product as Guru is.
= Not perfect but we all wait on the Lejonklou filter :)

In this thread you can see some examples of INO speakers and on the third pic, you find the Xover.
The pic after illustrate some subwoofer models.
http://www.faktiskt.se/phpBB3/viewtopic.php?t=41458

As most designers in this business, Ingvar has some VERY strong views on the hifi business, electronics and speaker design.
Some that I agree on, some not...
He is a believer in analogue X-over, and very keen at preserving phase. That's good.

NOTE
1/ I haven't heard the filter, so it's a gamble
2/ Ingvar will not sell and send filters. We have different views on some hifi-related stuff but over the years we have built mutual respect and this is a favour from him. So please don't try contacting him. If anyone consider the filter, send a PM to me and I check what's possible.
3/ If anyone like to discuss Guru speakers please start a new thread to keep this clean.
It's all about musical understanding!

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Re: JBL 4645C

Post by ThomasOK » 2016-05-24 04:05

As my previous speakers were Aktiv Isobariks and the ATC 100a, it probably comes as no surprise that I'll be getting a JBL 4645C as well. I haven't ordered it yet but intend to do so soon. From the work jajo has done with it this would seem to be the right one.

The big question for now is what to do for a crossover until Fredrik makes one (hint, hint). I have come up with another possible alternative that looks good - at least on paper. This is the Dahlquist DQ-LP1 electronic crossover designed for subwoofer(s). This is a design from the late 70s that is still held in high regard today. The man who designed it still uses the same circuit in his $289,000 speakers (not that this is any guarantee of musical quality).

What makes me feel it is likely a good interim choice is the following: it can be used for stereo or one or two mono subwoofers with internal summing, it can adjust the rolloff of the sub anywhere from 40Hz to 400Hz continuously, and it has an eq knob giving up to 5dB boost at 20Hz - something that is recommended by JBL for the most extended response from the 4645C (they actually recommend 8dB at 22Hz but that's pretty close). Also it uses a compound rolloff curve that is supposed to reduce phase distortion.

In addition to this it does have the ability to rolloff the low end of the main speakers which is accomplished passively to reduce noise and distortion. This is done by fitting the correct caps or resistors. I expect I will run the mains with no filtering. It also appears to be a relatively simple circuit that could possibly be improved with modern parts. Finally, this unit holds its value so well that it sells for more now than it did new. They are almost always available on eBay and generally sell for $200 to $400 depending on condition as long as they work. Therefore, if it doesn't work out (or if and when it is superseded) it can be resold for little or no loss. While there aren't any on eBay just now, they show up all the time and I just purchased one last week. So now all I need is the subwoofer and I'll be up and running.

Anyone who would like to know more about this device will find a wealth of information here:

https://sites.google.com/site/mpbarney/ ... ist-dq-lp1

I have not listened to one of these in a number of decades and certainly not in with this combination of components so I can't really say how musical a device it is. It just seems like something that could work.
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Re: JBL 4645C

Post by Music Lover » 2016-05-24 11:47

Congrats, have you received the filter yet?
My filter is probably handed over in person on June 7th. As I mentioned, he doesn't like sending them and since I now got delivery confirmation on the sub (3rd-4th week in June), no need to send it anyway.
ThomasOK wrote: I haven't ordered it yet but intend to do so soon.
Please check delivery dates asap. Few of these huge subs are sold on a daily bases (and mainly for public movie theatres) so normally it's custom order. (mine was 6 weeks)
ThomasOK wrote:
...it can be used for stereo or one or two mono subwoofers with internal summing, it can adjust the rolloff of the sub anywhere from 40Hz to 400Hz continuously, and it has an eq knob giving up to 5dB boost at 20Hz
If I understand the review (following the link) it's a 18dB/octave roll off in low pass to the sub. What is the high pass freq and roll off?
Based on Jajo and Fredriks test in jajo's sysrtem, it seems the HP freq was the most important, with the LP freq following. Then the roll off on both freq.
(only talking about the signal to the sub)
ThomasOK wrote:
In addition to this it does have the ability to rolloff the low end of the main speakers which is accomplished passively to reduce noise and distortion. This is done by fitting the correct caps or resistors. I expect I will run the mains with no filtering.
No filtering is likely best but please try both alternatives. I'm going to.

Thomas, this will be huge fun!
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Re: JBL 4645C

Post by ThomasOK » 2016-05-24 18:06

Yes, I did receive the Dahlquist filter. It is very clean and seems to be functioning properly. I haven't checked on the sub as I wasn't aware there was a delay on these. I will have to see what the word is on them.

I'm not sure if I am following your questions regarding the filtering fully. The Dahlquist DQ-LP1 has a rolloff of 18dB per octave at the top of the sub band. However, additional reading indicates that the filter is a staggered one that starts at 6dB per octave, then becomes 12dB per octave and finally 18dB. It is said that doing it this way preserves the bass transients better. The high pass filter for the mains is passive and is 6dB per octave. It is normally set for 60Hz to 80Hz but could be set anywhere desired with the right parts.

If you are asking about high pass filtering for the sub itself, I don't know if it has any. I haven't seen it mentioned anywhere.

I will indeed try it with the filtering on the mains. This should indeed be fun. If the sub can extend the things that the 3677s do down close to 20Hz it will be very impressive indeed (although Debbie thinks I am crazy for selling the ATCs).
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Re: JBL 4645C

Post by Music Lover » 2016-05-24 21:32

I'm sure your wife going to be thrilled when the sub is properly integrated with the 3677's
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Re: JBL 4645C

Post by lejonklou » 2016-05-24 23:05

ThomasOK wrote:If you are asking about high pass filtering for the sub itself, I don't know if it has any. I haven't seen it mentioned anywhere.
Too bad. In Jacobs system, the high pass frequency for the sub is, as ML mentioned, the most important setting for sound quality. Best at around 22 Hz (and 18 dB/oct). Massively better than no high pass at all, although the music played likely didn't contain anything below 20 Hz.

The second most important parameter is, again in Jacobs system, the low pass frequency at 80 Hz (and 24 dB/oct which was slightly better than 18).

I find it very interesting that high pass filtering has such a profound effect. Also in electronic circuits, this is a crucial parameter. Sometimes steep filtering is needed and sometimes operation all the way down to DC (0 Hz) sounds best.

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Re: JBL 4645C

Post by ThomasOK » 2016-05-24 23:57

Well then, you better get working...
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Re: JBL 4645C

Post by lejonklou » 2016-05-24 23:58

All work and no play makes Jack a dull boy.

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Re: JBL 4645C

Post by tokenbrit » 2016-05-25 00:43

lejonklou wrote:All work and no play makes Jack a dull boy.
If Jack works on the crossover, and it works, Jack can play with what plays music, which should make Jack (& ML, & Tom, & others) happy, as their bass will be anything but dull ;)

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Re: JBL 4645C

Post by ThomasOK » 2016-05-25 17:01

lejonklou wrote:All work and no play makes Jack a dull boy.
You mean this isn't play for you? ;-)
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Re: JBL 4645C

Post by ThomasOK » 2016-05-25 17:26

In the meantime, having been looking through endless forums for more information about the Dahlquist crossover (like whether or not it has a subsonic filter built in), I found a couple of recommendations for Marchand electronic crossovers which some found to be more "transparent". They do seem to put a lot of work into electronic crossovers and have a multitude of options as well as individual modules that can be built into custom crossovers. Looking over the units there are a few that might be made to work but the one that looks most like it would work best for our application is the XM66, although it has more than we actually need being a full-on stereo 2 way adjustable crossover. However, spec wise it comes very close to what Fredrik has found optimal. It has a 24dB per octave filters for both low pass to the bass and high pass to the mains (which could just be left unused if desired). The frequency is continuously variable from 20Hz to 5000Hz with a resolution of 1Hz in the lower part of the range. There are also level controls for both low and high on both channels and a damping control that changes the frequency behavior at the crossover point. Two important features for our usage are a summing switch that combines the two channels for use with a single subwoofer (or two mono subs as both outputs get the same signal) and a switchable subsonic filter at 20Hz. I have not been able to find the curve of the subsonic filter but I expect it would be fairly steep. The unit, of course, claims low distortion and high S/N ratio and seems to be well made, which is no guarantee of musical quality as we all know. But it does seem to be an interesting possibility that is readily available and not too expensive at $800US.

Here is a link to the page on the unit with a lot more information and photos:

http://www.marchandelec.com/xm66.html

I should mention that they have a 30 day return guaranty if not happy with the unit but the customer pays shipping both ways. They will also do custom modifications on request.
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Re: JBL 4645C

Post by ThomasOK » 2016-05-25 18:45

A little addendum. I sent an email to marchand when I was writing the last post and just received an email back from Phil Marchand with my answers. He seems quite easy to work with. I had asked about the subsonic filter and also customized versions and received the following reply:

"Thank you for your message.
Indeed the subsonic filter is 18dB/oct and 20Hz at -3dB.
Also , there is no point leaving out the high pass section because it is only a small part of the circuit.
We could build a special unit for you, without the 2 front panel controls for the high -pass and two RCA on the rear panel..
In all, It would save you $50.
If you like, we can adjust the subsonic filter to be at 22Hz; no charge for that.
Hope this helps"

So it has, or easily can have, the ideal subsonic filter as well as having the adjustability needed to work with the JBLs. Interesting that there is a currently produced alternative that won't break the bank.
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Re: JBL 4645C

Post by Music Lover » 2016-07-12 12:53

Update.
During some days I have tried out the optimum placement of the sub.

Step 1: sub laying on it's side between my 3677's (now on "Ofil stands")
In my room distance to back wall 14.0 cm. I then found the best positioning sideways to finally focusing on the height 13.0cm. Each half of mm is important!

Step 2: sub standing up, still between my 3677's
Ended up in a VERY interesting position!
Same distance to back wall. (no big surprise but good to have it verified)
Height 9.6cm.
When measuring the bass element position, it has exactly SAME position in the room as laying down!!

Step 3: standing vs laying down
Both are good but they excel (sound-wise) at different things. However, standing is more musical.

We believe this is an universal distance so Linnofil can hereby start constructing Sub "Ofil stands". :)


Step 4 (in the making): standing, outside my right speaker.
Stay Tuned

PS
Lessons learned.
It's paramount that you use SAME IDENTICAL books (whatever items used) under each of the four sub corners, to try out the height. If not, no possibility to get stringent results.
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Re: JBL 4645C

Post by Music Lover » 2016-10-02 21:12

Music Lover wrote:Step 4 (in the making): standing, outside my right speaker.
Stay Tuned
I forgot to report back on step 4, it's better!
The 4645 is best the longer to the left it is placed, so now it's quite close to the 3677.

I have also adjusted the filter (phase, amplitude, EQ - and then again fine tuning the amplitude)
Now is VERY good indeed :)
Very integrated with great timing, slam and musical flow. The sub can't be heard. The 3677's just sound bigger and with added low end grunt.

This is how it now look.
The TV is normally on the wall as you can see on the fasteners on the wall. One of these fasteners hold a small painting as an interim.
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Re: JBL 4645C

Post by matthias » 2016-10-02 22:10

What are the three panels at the wall behind the speakers?l

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Re: JBL 4645C

Post by Music Lover » 2016-10-02 22:18

Acoustic panels, going to be adjusted. Likely the one behind the racks going to be removed.
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Re: JBL 4645C

Post by matthias » 2016-10-02 23:21

ML,
I have some further questions:
What is the XO you use for the sub?
What is the price of the sub XO?
What are the setup parameters you use for the sub XO?
Am I right that you drive the sub with one TM?
Thank you.

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Re: JBL 4645C

Post by Music Lover » 2016-10-03 08:53

matthias wrote: What is the XO you use for the sub?
What is the price of the sub XO?
I paid about 600€, designed by a local constructor and not officially for sale. If interested, please send a PM and I check the availability. I think he has a few of them left in stock. If not I need to convince him to make more...
You find more info in post three in this thread.
matthias wrote: What are the setup parameters you use for the sub XO?
Am I right that you drive the sub with one TM?
I use 3*TM 2a for 3677 and 4645C.
The sub low pass freq is 80Hz.
The signal to the 3677's is NOT filtered.


The filter is tuned by ear with switches on the front panel in combination with adjusters on the circuit board. Roughly +8dB in amplitude compared with 3677. Phase 0 degrees and a bit EQ (reduced low freq amplitude and increased high freq amplitude = a tilt function)
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Re: JBL 4645C

Post by Music Lover » 2016-12-11 13:34

Ofil visited me yesterday with two sub stands (legs pointing out front/back and left/right) and four middle frames to test out.
The design use the know-how from the 3677 Ofil stand development.

We had a whole day assigned due to the time consuming task to modify the stand between each test.
You can say that we by now are good at deadlifting 4645C's...

Test #1
basic stand designs: legs pointing out front/back was best, clearly!
The "left/right"-stand was not used hereafter.
As a side note, the improvement from the present support was huge. (a pile of bibles in each corner)

Test #2-5
middle frames tested in the "front/back"-stand: it was dead easy to pick the winner. The differences between these were very big. It's a bit hard to believe how small pieces of metal can affect the performance THAT much.

FW a few hours and we then adjusted the sub filter, increasing the amplitude.
Now it's VERY good!
The musicality took a healthy jump. Unbelievable that a sub can contribute that much to the musical understanding.
The bass notes are now SO clean, crisp and deep. The live feeling is tremendous.
I tend to increase the volume more now.
And the SLAM and power is just fantastic. :)

Well done Ofil, the stands are half the performance of the speaker !!!
All of you with 3677's, you should REALLY consider the sub and Ofil stands. It's a no brainer.


PS
JBL that has the measurements on the spec sheet a bit off so Ofil going to make an adjustment.
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Re: JBL 4645C

Post by matthias » 2016-12-11 15:32

ML,
what do you think about having TWO subs and PASSIVE filters for them?

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Re: JBL 4645C

Post by Music Lover » 2016-12-11 16:21

matthias wrote:ML,
what do you think about having TWO subs and PASSIVE filters for them?

Matt
That is the goal but unfortunately I haven't the space needed on the front wall. It has to be positioned on the left side wall and that isn't a solution that is optimum.
But I like to test of course.
My present active CR80 filter support two subs, so that's no issue. On the contrary, the constructor INSISTS on using two.
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Re: JBL 4645C

Post by matthias » 2016-12-11 17:29

Music Lover wrote: That is the goal but unfortunately I haven't the space needed on the front wall.
In my case the WAF for even one sub is VERY low so I stay with the 3677s.
I will get my Ofils for Christmas.

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Re: JBL 4645C

Post by lejonklou » 2016-12-11 19:05

Thank you for a very exciting report, Music Lover and Ofil!

I think I understand the differences between the bottom frames. Same length of the legs pointing out? It seems logical that the front/back pointing legs should be better, as that's the direction the bass unit is pushing the enclosure.

What were the differences between the three middle frames?
Music Lover wrote:My present passive CR80 filter support two subs, so that's no issue. On the contrary, the constructor INSISTS on using two.
You meant "My current active CR80 filter", no?

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