HIFICRITIC audio review magazine
HIFICRITIC FORUMS
New Issue: Vol 8, No 1
HIFICRITIC
Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

3 Pages123>
Share
Options
Go to last post Go to first unread
Offline frank23  
#1 Posted : 16 July 2009 22:10:52(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
In my introduction I mentioned that I have designed, built and tweaked my own speaker. As I have used some unusual components I will elaborate on these so my experience on using these in a hifi home setup can be used by others.

At first an introduction about JBL pro drivers in general. There has been a giant pro driver catalogue for decades, but you probably know JBL only as a consumer brand. Forget the consumer JBL's for this thread, there is no link between the pro-drivers and the 250Ti and such, they do not use compression drivers and horns. Right until now there has always been a special line of consumer speakers (mostly sold in Japan, some not even available in the USA) that did use these pro-drivers and horns.

In the 70's these pro-consumer JBL's were domesticated copies of their large studio monitors, like the L300 Summit:

UserPostedImage

Here is a cutaway of the mid driver / horn combination in the L300, it is the one behind the plastic diffuser (which functions in controlled delaying pressure waves thereby creating a shaped wavefront):

UserPostedImage

In the 80's the direct link between the studio monitors and these domesticated consumer speaker was broken when the consumer version got specific horns, but they still used the pro-drivers. A current example is the K2-S9800, favourably reviewed in Hifi Critic (left in this pic):

UserPostedImage

And the biggest (and baddest) is the current DD66000 (those are two 14" or 15" neodymium woofers per side), I don't know if it is any good though...:

UserPostedImage

But I digress, because what I wanted to give you is a small guide to using JBL pro drivers and horns in the home.

When you want to use compression drivers it is good to know that there a lot of differences between them (only JBL these):
- there are 1", 1.5" and 2" drivers (as they are named after the diameter of the throat outlet)
- different magnets (alnico, ferrite and neodymium)
- different diaphragm materials (aluminium, titanium and beryllium)
- different coatings (no coating or aquaplas)
- different surrounds (radial, diamond and kapton)
- "old skool" long throats and recent short throats

Here is a small overview of JBL driver history with a nice cutaway pic of a 2" throat alnico driver: http://www.audioheritage...may/technology/435be.htm

Most important I think is that the combination of driver / horn / crossover is what does it, you cannot readily substitute parts in a balanced setup, although at JBL pro almost everything physically bolts together, acoustically it will not always work.

I have not tried all drivers, but some of them from different era's. To cut it short, my favourite compression drivers for using them as a tweeter above 1.500Hz are the 70's JBL 2420 1" alnico drivers with original aluminium radial suspension diaphragms.

UserPostedImage

These are the sweetest without a doubt. Although I have not heard a diamond surround alu diaphragm (can be put in the same magnet system), it is said that they are a little less sweet than the radial surround version. And the diamond surround version is very expensive to replace. So better stick to the radial surround aluminium versions.

The 2" drivers don't make it to 15kHz, and the titanium diaphragms sound harsher than the aluminium ones. I also have the 2440 (2" alnico) with more modern replacement JBL titanium diaphragms and I have the 2435 beryllium / neodymium 1.5" driver.

Should you want to go incredibly loud and still keep the quality and be able to cover 1kHz - 20kHz with one driver, the 2435 (1.5" neodymium) is the one to get. The consumer version in the K2-s9800 is called the 435be and is a little different in that it has the damping aquaplas coating and a larger backcap with fins (which seems to be all show as the pro version will be used at much much higher levels as they are in the Vertec stadium speakers and it has no need for those). 1.5" horns are not as common as 1" or 2" horns though so there is less to choose there. And the 2435 have very expensive beryllium diaphragms, so you'd better keep them in one piece: http://www.speakerrepair...0-287&Category_Code=

There is also an aluminium version, the 2431, but I haven't read anything about it being sweeter sounding, the replacement parts are a lot cheaper though: http://www.speakerrepair...0-263&Category_Code=

But the 2420 with aluminium is the sweetest sounding and is capable of functioning in a 1st order crossover setup in my living room. Later I will go into horns and crossovers for the 2420 and will add things I overlooked now. For all indepth information visit www.audioheritage.org or search google for obsolete specsheets which are available for almost all JBL drivers (only those for the 2435 are not found easily as they are hidden somewhere on the audioheritage website...)

Any questions?

ps. as I just started typing this it might look a little "all over the place", but I will come to a conclusion after a few posts and will come to horns and crossovers later...

Edited by user 17 July 2009 09:01:39(UTC)  | Reason: Not specified

User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#2 Posted : 16 July 2009 22:38:12(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

Very nice, bravo! Could you direct us someplace with measurements, e.g. waterfall plots, harmonic distortion plots and the like?
Sumer is icumen in!
Offline frank23  
#3 Posted : 16 July 2009 22:48:45(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
zonepress wrote:
Very nice, bravo! Could you direct us someplace with measurements, e.g. waterfall plots, harmonic distortion plots and the like?


I will go in to the specifics of the horns later and explain some curves, but for distortions I only know these curves of the 4430 studio monitor that these drivers were used in (at first, later version used the ferrite / titanium 2425 driver). This is tehn of course the distortion of the whole speaker including crossover, drivers and horns.

These distortion curves are raised 20dB, crossover is 2nd order around 1.000Hz. Don't look at the wattage, but at the SPL as the speakers are quite efficient, the above is at 100dB, the second at 110dB.

Later I will explain the working of this horn as it requires electronic compensation in the crossover, raising the signal from 4kHz towards 15kHz to keep response level, maybe adding some distortion in that section obviously but giving other things in return that I will explain later.

I also have these 15" bass drivers (the 2235H) and looking at these distortion figures up to 1.000Hz, I should be using them instead of having them stored!

[img]http://www.thevintageknob.org/AJW/JBL4435/JBL4435-fig15a[/img]

[img]http://www.thevintageknob.org/AJW/JBL4435/JBL4435-fig15b[/img]

And more in depth info about the 4430 speakers (that use the horns I will say more about later) can be found here:

http://www.jblpro.com/pub/technote/tn_v3n01.pdf

Edited by user 17 July 2009 09:08:28(UTC)  | Reason: Not specified

Offline frank23  
#4 Posted : 17 July 2009 14:06:45(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
After the driver introduction I will go in to suitable horns for the 1" drivers for home use.

The choice in horns for 2" drivers is quite big as historically there have been 2" drivers since 1930's or something. And because they have maintained the same horn flare and bolt standard, all can be use in combination, across brands.

I have not experienced specialist horns like they are used in high end myself, I have stuck to using standard JBL pro parts and this is what this thread is about.

For 1" drivers JBL I suggest the following home applicable horns:

==============

- 2391 (pro part number) see page 3 in this PDF for curves: http://www.jblpro.com/pu...coustic_lens_family1.pdf
- hl91 and hl92 (identical, but consumer part numbers): http://www.lansingherita...logs/1976-comp/page5.jpg

The above actually consist of the 2307 horn and 2308 acoustical lens, a longer version of the 2307 is the 2312 that can be used with the same 2308 lens

The 2307 horn is easily available on ebay, but the 2308 lens has become sought after as they are made from plastic and the corners break of easily. As this stuff is 35 years old, and has been used in pro environments, not many are left in perfect condition. The lens transforms the wavefront and makes it a 80x45 horn. As the efficiency of compression drivers falls away at higher frequencies, high frequency beaming is designed in to maintain the on axis response. It will beam vertically, but not as much as the 2370 (see below) as it is a short throw acoustical lens (up to 9 metres) and is therefore applicable in the home. It has been a while since I last used this combination, but to my memory is sounds unstressed, but it is said to have quite some distortion.

==============

Later JBL made the 2370 plastic horn available, it is cheap, but I cannot recommend it for home use as the vertical beaming is severe. It only has a 21degr coverage angle at 16kHz, which means 10degr above and below axis in which it stays within 6dB! Not too good for home use, but of course pro-conditions are different wanting to throw the sound in a controlled manner.
- http://www.jblpro.com/pub/components/2370a.pdf

==============

My recommendation for home use is the 2344A horn that was used in the 4430 and 4435 studio monitors. This was not available separately so it is not available in great numbers, but can be found on ebay and 2nd hand pro sites every now and then. Jammin jersey now quotes 175$ each for the 2344A: http://www.jamminjersey....s.php?prod=jblcomp#Horns

- spec sheet: http://www.jblpro.com/pub/obsolete/2344a.pdf
- speakers that used it: http://www.audioheritage...profiles/jbl/4430-35.htm

UserPostedImage

The 2344A was a true biradial horn, like the 2360 2" series. The 2370 1" and 2380 2" series were also marketed as biradial, but were only so horizontally and not vertically. And this one of the things that makes the 2344A special.

The essence is that the 2344A maintains a coverage angle of 100x100 degrees from 1kHz up to 16kHz horizontal and 12.5kHz vertical. This means that all frequencies are radiated equally loud within those 100x100 degrees, which is something I think no other speaker does.

When you move off axis (either horizontal or vertical), all frequencies attentuate in the same manner, so 1kHz is attenuated just as much as 10kHz, maintaining the complete energy spectrum off axis within the 100x100 coverage angle (so 50degr either side on axis). This probably does nice things to the room energy, but I am no expert on that.

Nothing comes for free of course, so unlike other horns, this one does not maintain its on axis response by beaming higher frequencies. The raw on axis response falls by about 10dB between 4kHz and 10kHz, so this has to be compensated for in the crossover. Luckily compression drivers and horns are very efficient drivers, so when combining these with normal high efficiency woofers, there is still enough headroom to make the compensation and still have an overall efficiency of about 93dB for 2.83V

When compensated this is what the response looks like (above is compensated in passive crossover, below is uncompensated):

UserPostedImage

These are the distortion figures (uncompensated it looks like):

UserPostedImage

==============

In my next posting I will go into the crossover I have used for my home application.

Edited by user 17 July 2009 14:08:40(UTC)  | Reason: Not specified

User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#5 Posted : 17 July 2009 15:42:41(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

You do realize that these distortion figures are not really good, don't you? They hover around 1%, which is quite high by direct radiator standards. Part of it is unavoidable and intimately connected with high efficiency. Air can be very effectively loaded inside a horn, and local vibration amplitudes become very large, the consequence being that inherent air non-linearity then becomes manifest. The horn seen above also presents sharp discontinuities and the concomitant change in load inevitably causes secondary sound emission.
Have you looked at the AX2 horn, designed at the University of Southampton?
http://www.nutshellhifi...._1995_Sound_of_Horns.pdf
Sumer is icumen in!
Offline ashleym  
#6 Posted : 17 July 2009 16:12:24(UTC)
ashleym


Rank: HIFI God

Joined: 02/02/2009(UTC)
Posts: 1,071
Location: uk

Thanks: 1 times
Was thanked: 3 time(s) in 3 post(s)
I ended up on the Heritage site a little while ago for some reason. It piqued an interest and I missed out on buying a Nova88 for not much. Which is why it went so quickly. I really havent heard pro-JBLs but there must be a fascination for a reason. Will it turn out to be like a lot of the stuff collectors go for or something that is still fun today a la Klipsch? Are the tv screen sound bars todays version of the mighty Paragon? Has anyone heard a Paragon?

Frank- can you give us some impressions of the sound please? Really interesting stuff and not something that gets covered anywhere I have seen
Offline frank23  
#7 Posted : 18 July 2009 19:23:27(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
zonepress wrote:
You do realize that these distortion figures are not really good, don't you? They hover around 1%, which is quite high by direct radiator standards. Part of it is unavoidable and intimately connected with high efficiency. Air can be very effectively loaded inside a horn, and local vibration amplitudes become very large, the consequence being that inherent air non-linearity then becomes manifest. The horn seen above also presents sharp discontinuities and the concomitant change in load inevitably causes secondary sound emission.
Have you looked at the AX2 horn, designed at the University of Southampton?
http://www.nutshellhifi...._1995_Sound_of_Horns.pdf


I am not too informed about what distortion figures say. In the last Hificritic they were mentioned for the Wilson and for the Meridian systems and I think the figures from the 4430 are not too far of. Compared to the numbers for the Meridian DSP 7200 the distortion of the JBL 4430 system at 500, 1000 and 5000Hz is about double. But the measurements of the Meridian are at 96dB and those of the JBL at 100dB, so perhaps the difference is slightly less. Not too bad for a system designed over 25 years ago I'd say. And how are these figures for off axis? As this is where the JBL 2344 horn in the 4430 is special.

But it isn't my goal to defend JBL parts here, just to give some insight in how JBL pro components may be used in the living room.

The PDF is really interesting. Even more so in that the two JBL horns that were researched among others were the 2307/2308 combination and the 2370. You can read above what I have said about those, the 2370 not being applicable for home use in my opinion and was never intended by JBL to be used in studio monitors anyway. It also drops about 4dB above 4kHz and I don't think they made compensation filters for that in the research project as you would do when designing it into a speaker.

On page 31 they say that their investigation shows that the 2307/2308 (combo 11, JBL horn with the Emilar driver) was more alike a direct driver than the 2370 (combo 16, JBL horn with a JBL 2426 titanium / ferrite driver), so that possibly means I am not all deaf! BigGrin

What concerns me in the research project is that for most horns they used an Emilar driver that turned out not to have the right throat expansion rate as they conclude themselves on page 33. Measurement with a TAD driver that did have the right rate showed far better results, even with the researchers own designed AX2 horn. So what would it have done to the research outcome if they had been using a driver with the right throat expansion rate in the first place in the case of the combinations that were tested with the Emilar (see page 34)?

As part of the conclusions on page 33 they say "the two horns having minimal mouth reflections were not identified as horns, and did not sound similar to the direct radiating reference". I don't understand this, what do they want then? Not sound like horns = good I guess, but they still don't sound as the direct radiating reference. As what then?

I'll read it again though as it is very interesting.

Edited by user 18 July 2009 19:27:28(UTC)  | Reason: Not specified

User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#8 Posted : 18 July 2009 19:50:31(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

I'm glad you liked the paper. The rule of thumb WRT distortion is an easy one to remember: -20 dB is 10%, -40 dB is 1%, -60 dB is 0.1%, -80 dB is 0.01% etc (each 20 dB fall equals a tenfold reduction in distortion percentage). Top-quality drivers can be around -70 dB for certain frequency and loudness ranges.
Sumer is icumen in!
Offline frank23  
#9 Posted : 18 July 2009 21:05:05(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
zonepress wrote:
I'm glad you liked the paper. The rule of thumb WRT distortion is an easy one to remember: -20 dB is 10%, -40 dB is 1%, -60 dB is 0.1%, -80 dB is 0.01% etc (each 20 dB fall equals a tenfold reduction in distortion percentage). Top-quality drivers can be around -70 dB for certain frequency and loudness ranges.


I've read it again, I like the research. A lot of questions remain, but there are some nice statistical valid results. And thanks for the rule of thumb distortion values.
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#10 Posted : 18 July 2009 22:54:57(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

One thing to bear in mind when studying the behavior of horns, is that, as I said previously, any abrupt change in the load presented to the propagating sound wave results in secondary emission from this point. Imagine a ray of light hitting a flat glass surface. The ray "bends" as it enters the glass (because glass presents a different "load" to light) but there is always a reflection: part of the beam bounces back as if the glass surface were partiallly a mirror. So let's go back to sound now. Inasmuch as this reflection goes back towards the horn, it will then be modified by the horn in an asymmetrical (and often unpredictable) way, because it no longer comes from the center of the horn where the driver is. Inasmuch as this reflection is directed towards the listener, it will be a distorted image of the original signal, because its frequency content has been modified by the load boundary. It will also be time-delayed as compared to the original signal, because it has not travelled in a straight line. Now imagine all these reflections from all points of load change ("boundaries") interacting with one another. The frequency-related aspects of all this mess can be measured in steady state measurements like the ones you quote. The time-related shifts and delayed images cannot. It is in the latter domain that cepstral analysis can help to a degree. Have you ever seen cepstra in any consumer-oriented mag? Because I haven't. It's the kind of equipment that magazines cannot afford and almost all magazine writers are not qualified to use and interpret. The authors of the paper have access to sophisticated equipment and facilities by virtue of their academic affiliations, and they are using them to good effect. Our ears are a fine piece of equipment, but they are fallible, and no substitute for measuring properly. It's like photography: if one cannot measure light, one cannot take good pictures and sure as heck they cannot design and make cameras. Even Ansel Adams would concede as much.
Sumer is icumen in!
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#11 Posted : 19 July 2009 00:11:47(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

zonepress wrote:
air non-linearity then becomes manifest
For some math-heavy analysis, see: http://www.nutshellhifi....2002_Horn_Distortion.pdf
Sumer is icumen in!
Offline frank23  
#12 Posted : 19 July 2009 13:38:49(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
ashleym wrote:
I ended up on the Heritage site a little while ago for some reason. It piqued an interest and I missed out on buying a Nova88 for not much. Which is why it went so quickly. I really havent heard pro-JBLs but there must be a fascination for a reason. Will it turn out to be like a lot of the stuff collectors go for or something that is still fun today a la Klipsch? Are the tv screen sound bars todays version of the mighty Paragon? Has anyone heard a Paragon?

Frank- can you give us some impressions of the sound please? Really interesting stuff and not something that gets covered anywhere I have seen


Well I think they are still fun today, but not as a high resolution home speaker. I think a lot of their fame has to be seen in the position they had over home speakers in the era that they were used. I think home speakers have evolved quite a lot the last decades whereas large studio monitors like the JBL pro's hardly exist anymore. Even JBL doesn't build them anymore.

But of course, there is no substitute for square inches when wanting to make an impact and have the speaker control the room.

I have owned a pair of JBL 4333B 3-way studio monitors in very good condition and found them very analytical, but not too musical. It was like listening to the mixing desk instead of the music. I ended up selling them on because I found my own application of JBL components more satisfying.

This is a pic from the internet, not my stereo, that shows the size of the 4333B 150litre cabinet:
UserPostedImage

You should not forget that these studio monitors were built for studio monitoring use. Crossovers were partly designed to keep drivers in their right frequency area (allways a good thing) and prevent them from overload (a much smaller problem in a home).

The crossovers were also designed to be flexible. You could flick a switch in the 4333B to go from passive to active and if I remember correctly there were 11 switching points in the crossover that then switched from the passive to the active position, and all of them a few decades old en not gold plated. Not high end in any way I'd say to have 11 switching points in speaker level signal routes.

Of course in the living room you don't need all that and that's why I started this thread because I think the components are better quality wise than their application sometimes was. The compression drivers and horns are sufficiently revealing to show the difference in all previous components like cables and capacitors, so I think they deserve better than 11 signal line switches in their crossover.

You can still rent the 4333B though: http://www.rentcom.com/c...Full_Range_Speakers.html

Edited by user 19 July 2009 13:45:01(UTC)  | Reason: Not specified

Offline ashleym  
#13 Posted : 24 July 2009 20:46:46(UTC)
ashleym


Rank: HIFI God

Joined: 02/02/2009(UTC)
Posts: 1,071
Location: uk

Thanks: 1 times
Was thanked: 3 time(s) in 3 post(s)
Thanks for this information. I dont think we should knock speakers for using PA or professional drivers. Look at Aspara Acoustics using Fane drivers, PMC using Volt and Naim using PD and all this JBL stuff. Plenty to ponder......
Offline frank23  
#14 Posted : 11 October 2009 19:32:27(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
should you be interested how my 3-way active system using JBL pro drivers turned out, go here and scroll down a little to post #42: http://audioheritage.org...d.php?t=26151&page=3

oh, be prepared, it is an ugly looking system!

Edited by user 11 October 2009 19:33:26(UTC)  | Reason: Not specified

Offline ashleym  
#15 Posted : 12 October 2009 12:00:02(UTC)
ashleym


Rank: HIFI God

Joined: 02/02/2009(UTC)
Posts: 1,071
Location: uk

Thanks: 1 times
Was thanked: 3 time(s) in 3 post(s)
Far from ugly. Well done. All you need now is some of the corn blue paint for the front baffle. I wonder how much your "modern" cabinet construction methods have made the best of the classic driver?
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#16 Posted : 12 October 2009 12:45:09(UTC)
zonepress


Rank: HIFI God

Joined: 18/09/2008(UTC)
Posts: 1,013
Location: Greece

frank23 wrote:
oh, be prepared, it is an ugly looking system!
It will look better with some paint and grills. Aren't you concerned about beaming at the 1400 Hz crossover point? The HF and MF drivers look a bit too far apart from each other for comfort.
Sumer is icumen in!
Offline Hartmut  
#17 Posted : 13 October 2009 09:07:24(UTC)
Hartmut


Rank: HIFI Newbie

Joined: 30/07/2009(UTC)
Posts: 2
Location: Germany

Hi,

I don't want to takeover this thread, just some remarks, I heard the 4430 and the 4330 in home environments, and also heard the latest D66000 at a hifi-show.

I had the 4430 for some weeks, I never liked it, it lacks detail and air, and early reflections from the ground and ceiling kill any presision. Bass is too soft, too.

However, I liked the 4330 much better, this was playing alive, and was a lot of fun listening rock music. Ten years ago a friend and I discovered a restoration object 4330, did all the repairs on drivers and enclosures, and then sold this for good money. We had extended listening before selling. The only thing I didn't like was the sharpish playing bullet tweeter.

The D66000 is good in bass only, and is veiled in midrange+treble. It was played against the biggest Backes+Muller active "hifi" loudspeaker. The Backes+Muller was much better.

Since I have played with high-efficiency stuff for nearly 15 years now, this is what I have currently:
- bass Altec 414-16A, in 150L enclosure without back (open baffle style)
- midrange Altec 802A into "Le Dauphin" horn
- tweeter Goto SG-06-16
- XO at 700+7000 with Alto maxidrive 3.4 (sounds much better than any Behringer, no modifications needed)
- amps: bass: DIY transistor, mid DIY tube, high DIY tube
Without any room correction or eq-ing I have 40-20k flat, which is enough for my 20sq-metre room with solid walls.
To use most of the bits of the active XO, all power amps are set for gain around 2..4, and my line stage is working at a much higher output level.

I tried JBL 2344A, 2370, 2345 with 1"-drivers for midrange, and also JBL 2360 with TAD4002, but all these I did not like soundwise.
Some honk, some have plastic sound, some sound veiled. Horn sound getting right is sooo difficult.
The LeDauphin was the last horn I wanted to try before closing the chapter, and going back to "hifi" drivers.
The LeD. is a sand-filled horn in Altec 511 style with thin wooden walls. With the Altec driver it has a near flat curve 500..7k, no overshoot, no nasty ringing.
It is DIY, and the plans are on the web.

best regards, Hartmut
Offline frank23  
#18 Posted : 13 October 2009 12:44:11(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
ashleym wrote:
Far from ugly. Well done. All you need now is some of the corn blue paint for the front baffle. I wonder how much your "modern" cabinet construction methods have made the best of the classic driver?


I think original JBL PRO cabinets (even those for studio use) are constructed more for staying in one piece, than for acoustic optimization. They never used non-parallell walls for instance, except for some home versions, but I think that was more because of the looks than because of the acoustics. It is refreshing though to see them using straight standard basreflex ports etc., their cabinet recommendations for their drivers are very straightforward. Just use xyz ft3 of cabinet with dimensions relating abc to each other and use 2 standard x diameter ports of y lenght.

My cabinets are not too special either. The bass cabinet is a standard JBL cabinet. It is braced and heavy, but acoustically it is rather lively as the panels are large and not damped. It is 5ft3, so of course harder to make acoustically inert than a mini monitor. It could benefit from panel damping, so I'll probably glue some bitumen in once.

The mid and high cabinet is a work in progress. I am trying different fillings and panel dampings and although it is square outside, because of the horn / driver / corner wood, there are no large parallel panels inside.
Offline frank23  
#19 Posted : 13 October 2009 12:50:03(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
zonepress wrote:
frank23 wrote:
oh, be prepared, it is an ugly looking system!
It will look better with some paint and grills. Aren't you concerned about beaming at the 1400 Hz crossover point? The HF and MF drivers look a bit too far apart from each other for comfort.


I can't get them any closer than this. Of course, these are no near-field-monitors, a suitable listening distance is required. The center-center distance of mid and high drivers is 27cm. Their polar response at the cross over frequency is near identical. The only small problem I see is that the acoustic centers are about 2cm apart (the compression driver magnet polar plate is about 2cm further back than the mid driver), but I still have to measure the impuls response, it might be fine, but I don't know how to measure this without Clio etc.
Offline frank23  
#20 Posted : 13 October 2009 12:58:04(UTC)
frank23


Rank: HIFI Guru

Joined: 12/07/2009(UTC)
Posts: 367
Location: the netherlands

Was thanked: 2 time(s) in 2 post(s)
Hartmut wrote:
Hi,

I don't want to takeover this thread, just some remarks, I heard the 4430 and the 4330 in home environments, and also heard the latest D66000 at a hifi-show.

I had the 4430 for some weeks, I never liked it, it lacks detail and air, and early reflections from the ground and ceiling kill any presision. Bass is too soft, too.

etc...


Thanks for sharing. It seems like you have listened to quite a number of horn/drivers. Your system is interesting too. This thread was not meant to promote JBL PRO speakers as you can read above that my findings were not all positive either. But I think most of it is due to cabinet and cross over problems (e.g. 11 switches in the 4333B crossover for switching to biamped modus can never be called high-end), and you can do very nice things with the drivers themselves in different setups.
Users browsing this topic
Guest
3 Pages123>
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Follow HIFICRITIC Email HIFICRITIC follow HIFICRITIC on Twitter Follow HIFICRITIC on Facebook