1400Nd Vs 1200Fe (2- way with 1.5 horn)

[Didier]

Hi Ian
My idea was to fit the 1400Nd on the En5 instead of the 2234H in order to have an idea of the low frequency. I don't want to modify the box!
Someone knows the volume of the S7500?
Didier

[Ian Mackenzie]

Based on available information 4.1 cuft3

[Didier]

Based on available information 4.1 cuft3

I thought M9500 was 4.1. And it seems bigger than the S7500 .

[hlaari]

I thought M9500 was 4.1. And it seems bigger than the S7500 .

The enclosures in the M9500 are bigger than the enclosure in the S9500
S7500 use the same bottom enclosure like S9500

I have only found the volume size for the M9500 not for S9500

[Ian Mackenzie]

http://www.allegrosound.com/JBL_K2_M9500.pdf

http://www.cieri.net/Documenti/Catal...)%20(2000).pdf

http://dl.jehandleiding.nl/new/exter...eSC=M&direct=1

[Didier]

Thank you Ian, the Pdf confirm the M9500 is 115 liters (4.1 cu ft) 28 Hz tuning (lower LF)
The S7500 might be less but I don't find the datas

[Ian Mackenzie]

http://www.audioheritage.org/vbullet...light=K2+M9500

There is a post on the port dimensions in that thread.

I would do a search as there is some interesting threads on this system including bi amp operation

The manual confirms the s7500 is the bottom enclosure of the S9500

But l would not read too much into what might or might not have been incorporated into the M9500
It had an outboard crossover and was no compromise with parts.

I think 4.1 cuft3 is a safe bet
Read the manuals in full. I found the comments on the tuning of the enclosure and room placement quite telling of the simulations. Try and keep with what Jbl did with the woofers

Your project has the makings of an excellent loudspeaker

You’ve chosen top notch drivers.

Are you looking to bi amp?
Passive crossover design is quite difficult for the audio diy audio person at home to get right.

If you can tune an active crossover for a particular project it’s a more effective approach and sonic improvement is very good.

In the thread there is detail of biamp crossover settings.
The dx1 Jbl crossover is no longer available. (See my comments below)

That information would be very useful for the woofer low pass design.

Your horn is different but l would study the s9500 passive crossover schematics for clues on how to blend your horn. The filters are 3rd order and are customised for the characteristics of the drivers.

There are other members like Deiter in Germany who have explored this system so l would send a PM

If you require specific help on the crossover send me a PM?
I am rolling out soon a commercial audiophile active crossover that can be set up in my Lab for a variety JBL systems.



http://www.audioheritage.org/vbullet...l=1#post379049

[Ian Mackenzie]

The enclosures in the M9500 are bigger than the enclosure in the S9500
S7500 use the same bottom enclosure like S9500

I have only found the volume size for the M9500 not for S9500

That could well be the case

Jbls manuals and brochures have had mis prints before!

[Didier]

Thank's Ian.
I added 252G in the win isd similation. It's seems to be a good driver also. Better LF than the 1200Fe in 60L !?
What about it vs 1400Nd in the midrange?

[RMC]

Hi Didier and Rob,

As indicated in an earlier post, here is the second part of the "Step-Down Mode" information, this time from D. B. Keele(1).

Keele started with different driver types modeled them in conventional LF alignments (e.g. B4, Qb3, C4, closed box) and also simulated new pseudo-sixth-order alignments to compare results with those. He adds that all the new alignments have coincident F3, Fb and maximum boost frequencies (p. 354).

Though Keele talks about a "modest amount of lift" (+ 6 db at the peak boost frequency in the bass range, 1.07 times F3), doing this requires four times the amount of power. What would otherwise be driven with 25 watts now requires 100, and what would otherwise have taken 100 now requires 400 Watts. Not really modest in my view, however today the cost of Watts can be pretty cheap.

Keele also says "It must be stressed that these alignments represent only discrete selections from a continuum of possible alignments." (p. 355) So there's a lot more than meets the eye (e.g. E-V's).

Keele says its not driver Fs that's important but Fs/Qt which indicates how low a driver will go. Adding for a desired F3 in the 25-50 hz range, Fs/Qt can be from about 80 to 160 hz. Drivers with that ratio would be likely candidates for B6 alignments. BTW the Fs/Qt ratio for 1400 ND stands at 106, therefore within the range.

Talking about a system aligned for a B4 response (F3= Fb=40hz) that is converted to a pseudo-B6 alignment, (F3=Fb=28hz, boost @ 30hz )Keele mentions "The net effect on the system response is one-half octave extention of low-frequency response with only about 3 db less maximum acoustic power output capability in the passband." (p.356) Three db is a notable quantity and represents half the power. The lower tuning and EQ boost will return the response back to a roughly flat condition according to Keele. That conversion "... somewhat reduces the maximum acoustic output capabilities of the system in the 35-70 hz range, but greatly increases the maximum output below 35 hz" (p. 357)

In his concluding summary, Keele mentions using these "... alignments offers real advantages in providing maximum useful low-frequency acoustic output while minimizing driver diaphragm excursion both in and out of the systems operating frequency range." (p. 357).

In another quasi-sixth-order (QB6) box he simulated (Fb=Faux=F3= 26 hz), the 6 db peak boost from auxiliary circuit happens at 1.07 times Fb = 28 hz (p. 358). (Faux is the frequency of the auxiliary peak boost, as I understand).

Note that in the simulations Keele did, when the new Fb was at 26 hz the 6 db boost was applied at 28 hz, for Fb 28 hz it was applied at 30 hz and for Fb 43 hz it was applied at 46 hz. Not exactly at Fb...

Also interesting to note that for a 4 cu. ft. box Keele used about 20% overvolume to compensate for box losses, while using 30% overvolume to offset box losses for a 7.5 cu. ft. box. More overvolume for larger boxes and less for smaller ones appears to agree with Leach (2) who suggests to use lower QL number for larger boxes and higher QL number for smaller boxes. That means larger boxes are more lossy than small ones. In the computer design process, entry of a lower QL will lead to a larger volume (Vb), and entry of a higher QL number leads to a smaller box. Unfortunately, Leach did not mention which higher or lower QL to use, but he did mention the initial design process with QL 7 is correct, and QL 7 good for 2 to 3 cu. ft. boxes. I would probably use QL 5 for larger boxes and QL 10 for smaller ones.

I have some issues with Keele's article and also with some E-V Step-Down Mode items which I'll cover in part 3 in the near future.

Richard

(1) A New Set of Sixth-Order Vented-Box Loudspeaker System Alignments, JAES, 06-1975, P. 354. This can be found on his Website, dbkeele.com, AES papers, item # 8.

(2) W. Marshall Leach Jr., Vented-Box Loudspeaker Design with a Given Driver, 2001, P. 1, available on Net.

[hlaari]

http://www.audioheritage.org/vbullet...light=K2+M9500

There is a post on the port dimensions in that thread.

I would do a search as there is some interesting threads on this system including bi amp operation

The manual confirms the s7500 is the bottom enclosure of the S9500

But l would not read too much into what might or might not have been incorporated into the M9500
It had an outboard crossover and was no compromise with parts.

I think 4.1 cuft3 is a safe bet
Read the manuals in full. I found the comments on the tuning of the enclosure and room placement quite telling of the simulations. Try and keep with what Jbl did with the woofers

Your project has the makings of an excellent loudspeaker

You’ve chosen top notch drivers.

Are you looking to bi amp?
Passive crossover design is quite difficult for the audio diy audio person at home to get right.

If you can tune an active crossover for a particular project it’s a more effective approach and sonic improvement is very good.

In the thread there is detail of biamp crossover settings.
The dx1 Jbl crossover is no longer available. (See my comments below)

That information would be very useful for the woofer low pass design.

Your horn is different but l would study the s9500 passive crossover schematics for clues on how to blend your horn. The filters are 3rd order and are customised for the characteristics of the drivers.

There are other members like Deiter in Germany who have explored this system so l would send a PM

If you require specific help on the crossover send me a PM?
I am rolling out soon a commercial audiophile active crossover that can be set up in my Lab for a variety JBL systems.



http://www.audioheritage.org/vbullet...l=1#post379049

I think at 4.1 cu/ft would be good volume for 1400Nd

I think at Guido did use at least this volume size with good results
http://www.audioheritage.org/vbullet...-the-USA/page3

[Ian Mackenzie]

Thank's Ian.
I added 252G in the win isd similation. It's seems to be a good driver also. Better LF than the 1200Fe in 60L !?
What about it vs 1400Nd in the midrange?

It’s used in the LSR 32 monitors. 2 of those per the s5500 would be interesting.
I’ve never compared either driver so l can’t comment. There’s a lot a simulation won’t tell that your ears will tell you

Some drivers are fabulous and others are so so. Transducer design at that level is a Black art


http://www.audioheritage.org/vbullet...12-quot-Woofer

http://www.audioheritage.org/vbullet...ght=252g&pp=15

http://www.allegrosound.com/JBL_K2_S5500.pdf

[RMC]

Hi Didier,

Seems to me you have lost sight of your initial objective:

"My first idea was to build some enclosure with the same volume as the M9500: 115 liters (4.1 cu ft) 28 Hz tuning (lower LF), but if it's possible to get the same (or better) result in a smaller box: - it's better for my living room"

It would be interesting to hear what your living room space will tell you with a 4.1 cu. ft. box (NET volume as is usually given) considering the following:

As can be seen in my post # 55, Keele overvolumed about 20% to compensate for box losses with a 4 cu. ft box and Leach suggests a QL lower than 7 for boxes larger than 3 cu. ft. With only 20% overvolume, the box is already close to 5 cu. ft. (4.92 cu. ft.).

Then you must add overvolume for space taken in the box by the driver, good bracing and vent... (JBL used the "liberally braced" expression in M9500 Owner Manual). Seems to me you would end-up with a box gross volume around 6+ cu. ft. (to get to a 4.1 net Vb) when everything is calculated and considered as it MUST be. That's getting further away from your initial objective...

JBL did not publish figures for space taken by driver for 14" models, but 12" models are given at 0.15 cu. ft. and 15" models at 0.20 cu. ft. This driver (1400 ND) being a neo model magnets are usually smaller so the real number is probably somewhere between 12" and 15" drivers (maybe closer to 15" for safety).

BTW I have in front of me the JBL M9500 Owner's Manual (9/95 edition) as I write this, and I must say I'm not "thrown to the floor" by the VLF performance. With ground plane measurement, at 40 hz the LF level is already at - 3 to -4 db (figure 6), and frequency response is quoted as "35 hz to 20 khz (half-space)" with NO mention of + or less db...

EDIT: In the manual these are given as "Typical System Performance Measurements".

Richard

[Ian Mackenzie]

Hi Didier

When you get around to a practical evaluation the manual explains the optimum placement for bass.

We don’t know how you propose to place the enclosures but the below extract of the manual is a guideline.

http://www.allegrosound.com/JBL_K2_S7500.pdf

Guido previously built a impressive project with a single 1400nd

If he is still around he might comment

[Ian Mackenzie]

Maybe I was not very clear in my first message (probably) but I was wondering if it was possible to do something so good as 1400nd in 115L, with 1200fe in a smaller box... for example 60L?
I'll try to do a simulation with winisd.
I will use an active crossover Didier (Dn92) probably my yamaha SP2060...
Bye!
Didier

Read the above.

Richard,

Have you modeled up the 252G drivers mentioned earlier yet?