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The musings and pains of a loudspeaker designer
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Offline Simon Briggs  
#21 Posted : 23 August 2019 09:32:45(UTC)
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I have been investigating alernatives, this one has been suggested to me as one to consider.

Visaton B200

I will be looing at others, but fullrange units as midranges offer a dynamic solution.
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Offline Shadders  
#22 Posted : 23 August 2019 15:10:33(UTC)
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Originally Posted by: Simon Briggs Go to Quoted Post
I have been investigating alernatives, this one has been suggested to me as one to consider.

Visaton B200

I will be looing at others, but fullrange units as midranges offer a dynamic solution.

Hi,
If you examine the maximum linear displacement (+/-3.5mm), it is lower than small mid range/woofer equivalents. If the lower crossover frequency is quite low, then it will distort the sound at higher SPL.

The Volt BM220.8 has +/-4mm, and the SB Acoustics SB17NBAC35-4 has +/-5.5mm. If you look at the Purifi driver - they only sell one (not sure of the price or availability) then it has an Xmax = +/-10mm. Not sure if this is a typo, as it is nearly 2x more than the same size unit from SB.

EDIT : The volt BM165.1, 6.5inch bass/midrange, has an Xmax of +/-6.3mm.

Regards,
Shadders.

Edited by user 23 August 2019 17:49:44(UTC)  | Reason: Additional info
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Offline Simon Briggs  
#23 Posted : 23 August 2019 21:09:14(UTC)
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Originally Posted by: Shadders Go to Quoted Post
Originally Posted by: Simon Briggs Go to Quoted Post
I have been investigating alernatives, this one has been suggested to me as one to consider.

Visaton B200

I will be looing at others, but fullrange units as midranges offer a dynamic solution.

Hi,
If you examine the maximum linear displacement (+/-3.5mm), it is lower than small mid range/woofer equivalents. If the lower crossover frequency is quite low, then it will distort the sound at higher SPL.

The Volt BM220.8 has +/-4mm, and the SB Acoustics SB17NBAC35-4 has +/-5.5mm. If you look at the Purifi driver - they only sell one (not sure of the price or availability) then it has an Xmax = +/-10mm. Not sure if this is a typo, as it is nearly 2x more than the same size unit from SB.

EDIT : The volt BM165.1, 6.5inch bass/midrange, has an Xmax of +/-6.3mm.

Regards,
Shadders.


Crossover frequency from bass to mid likely to be 250Hz with third order electrical filters. This means that excursons encountered at even fairly high outputs will be well within x-max.

I have looked at the Volts for other projects and have not totally ruled out the BM220.8, but it is likely that it will be less dynamic than the Seas as a midrange. The drivers mentioned are well below what I require for sensitivity, the Seas FR is within my target range.

I have even looked at the Faital Pro 6PR160 which is a 6 1/2 inch unit designed for excellent reporduction of the vocal range, this is a high power unit capable of 240 w programme and will certainly meeti my output requirements wit 95 db sensitivity and +/- 5mm x-max with the combination of a nice high QM and with a low moving mass, it is likely very dynamic. Just the ticket. The J8008 unit likewise also has a QM > 5 which will liley result in great timing.

I will be looking at others and users report that the Faital driver to be very well suited to some high end bespoke projects.
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Offline Simon Briggs  
#24 Posted : 23 August 2019 21:43:52(UTC)
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Looking at the Faital Pro catalogue they have some real nice looking mid units
Press release here

Edited by user 24 August 2019 13:29:09(UTC)  | Reason: Not specified
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Offline Simon Briggs  
#25 Posted : 24 August 2019 07:33:32(UTC)
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Must say that I am a fan of Volt drivers, very well made if I was looking at a three way with 88 -89 target senditivity the BM220.8 would be high on my list
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Offline Martin Colloms  
#26 Posted : 25 August 2019 17:11:52(UTC)
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This is a most ambitious project where the investment justifies exceptional mid and treble

HF could well be a Mundforf AMT 'ribbbon'

The mid, on a classic basis, could be a high power pulp cone Scan unit with neo magnet and an open frame, probably not the cut cone type as here the better damping may dilute dynamic expression.

A high order L-R Xover at 2kHz is eminently possible

Martin
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Offline Simon Briggs  
#27 Posted : 25 August 2019 18:23:55(UTC)
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Originally Posted by: Martin Colloms Go to Quoted Post
This is a most ambitious project where the investment justifies exceptional mid and treble

HF could well be a Mundforf AMT 'ribbbon'

The mid, on a classic basis, could be a high power pulp cone Scan unit with neo magnet and an open frame, probably not the cut cone type as here the better damping may dilute dynamic expression.

A high order L-R Xover at 2kHz is eminently possible

Martin


Martin, Hi

Looking through so many tweeters to look at

https://www.hificollecti...undorf-amt-tweeters.html

This one is sensitive and could work well with a transformer inductior 2nd order LR

https://hfc-fs.s3-eu-wes...fs-public/amt29cm1.1.pdf

Midrange?

Was already investigating Scan mids, is this the one?

https://www.scan-speak.d...range/?single_prod_id=27

Happy to defer to greater experience with other options within the ranges

ATB

Simon

Edited by user 26 August 2019 05:15:22(UTC)  | Reason: Not specified
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Offline Simon Briggs  
#28 Posted : 26 August 2019 13:06:04(UTC)
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Will be modelling with a few of the Mundorf AMT units, one of them has an excellent bandwidth and very suitable, not cheap but likely excellent as it also makes crossover design simpler.

The same for two units I have identified from the SB Acoustics Satori line.

They make for easy crossover design and simpler has to be better.

This one is particularly striking a nice high QM, a great magnet structure, cooling and airflow as well.

Why select drivers which make life difficult!!
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Offline Shadders  
#29 Posted : 26 August 2019 15:36:27(UTC)
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Hi,
The SB Satori range are a specific cone material.

If you use the other 6.5inch units, such as the CAC, CRC, NAC, NRX and MFC, which have the same mounting dimensions, then you can select which ever material is to your liking. The NAC has the optimal lowest distortion in the 4ohm version, and others will present a "character".

You can interchange the units depending on the sound signature preference.

Regards,
Shadders.
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Offline Simon Briggs  
#30 Posted : 07 September 2019 17:24:47(UTC)
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The beauty of this project is that the modules are interchangeable / mid baffles are too so that I can listen to different mid and treble units.

After investigation, I will be experimenting with the SB Acoustics Satori units, available in both 6 ½ and 7 ½ sizes they are the 4 ohm white cone models.

Two versions are available dedicated bass / mids and the 6 1 /2” in prime midrange units
I will be researching both, this one is very promising the Satori MR16PNW-4 6 ½” White Egyptian Papyrus Cone Midrange - 4 ohm with 92.5 dB/w sensitivity and a very flat response

https://www.madisoundspe...re.com/pdf/MR16PNW-4.pdf

The bass / mid version is this one. 6 ½” SATORI MW16PNW-4

https://www.madisoundspe...Satori_6in_MW16PNW-4.pdf

I am leaning towards the Satori MR16PNW-4 6 ½” They have properties which I find enticing.

The Scan mid units were also a possibility, but not the sliced cone models, which to my ears lack the last degree of dynamic expression.

The scan I considered earlier was the 15M/4624G00 but have now ruled it out.

Tweeters I have a few nice units to play about with, but do not rule out the high end Mundorf AMT units they have a real nice flat response like the 6 ½” Satori units have high sensitivity and flat responses great motors and likely high levels of dynamic performance.
This is going to be fun.

Edited by user 07 September 2019 17:26:16(UTC)  | Reason: Not specified
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Offline Shadders  
#31 Posted : 07 September 2019 22:01:22(UTC)
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Originally Posted by: Simon Briggs Go to Quoted Post
The beauty of this project is that the modules are interchangeable / mid baffles are too so that I can listen to different mid and treble units.

After investigation, I will be experimenting with the SB Acoustics Satori units, available in both 6 ½ and 7 ½ sizes they are the 4 ohm white cone models.

Two versions are available dedicated bass / mids and the 6 1 /2” in prime midrange units
I will be researching both, this one is very promising the Satori MR16PNW-4 6 ½” White Egyptian Papyrus Cone Midrange - 4 ohm with 92.5 dB/w sensitivity and a very flat response

https://www.madisoundspe...re.com/pdf/MR16PNW-4.pdf

The bass / mid version is this one. 6 ½” SATORI MW16PNW-4

https://www.madisoundspe...Satori_6in_MW16PNW-4.pdf

I am leaning towards the Satori MR16PNW-4 6 ½” They have properties which I find enticing.

The Scan mid units were also a possibility, but not the sliced cone models, which to my ears lack the last degree of dynamic expression.

The scan I considered earlier was the 15M/4624G00 but have now ruled it out.

Tweeters I have a few nice units to play about with, but do not rule out the high end Mundorf AMT units they have a real nice flat response like the 6 ½” Satori units have high sensitivity and flat responses great motors and likely high levels of dynamic performance.
This is going to be fun.

Hi,
The SB NBAC unit has effectively the same frequency response as the Satori unit - at half the price - same peaks at the lower frequencies - can be seen if you overlay the two.

The following website shows that the lower priced SB NBAC unit has a lower THD (4ohm unit) :
http://www.audioexcite.com/?page_id=4018

The Satori has 1mm extra linear travel - but if you are crossing over at a higher frequency - then you may not use the full excursion.

Regards,
Shadders.

Edited by user 07 September 2019 22:02:05(UTC)  | Reason: Spelling
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Offline Simon Briggs  
#32 Posted : 08 September 2019 19:25:53(UTC)
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Together with my Seas FR unit I will be making sub baffles for the 6 1/2" SB unit model Satori MR16PNW-4 6 ½” as well

I have a few tweeters to play about with as well including Audax TW034X0 and Scan Revelator 99000 units.

Others may follow
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Offline Simon Briggs  
#33 Posted : 25 September 2019 10:19:33(UTC)
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I have ordered a pair of SB Satori MR16PNW-4 6 ½” units

Should be fun
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Offline Simon Briggs  
#34 Posted : 25 September 2019 11:11:26(UTC)
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Crossover points will be nominally 250Hz between bass units and the mid and anywhere from 2 - 3 Khz between mid and treble, likely third order electrical slopes using T networks.

Next stage will be active between bass and mid same 250Hz point, with a passive mid / treble to allow for extra tweaking.

Might I go full active? remains to be seen
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Offline Simon Briggs  
#35 Posted : 30 October 2019 11:19:09(UTC)
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Winter project will be to build small test enclosure(s) for the mid / treble, whip up suitable passive crossovers etc. and then just listen.

Bass section some indecision remains, I really like the idea of using a pair of bass units in Force cancellation.

The kind of music programme I listen to generally has considerable LF bass content (Symphonic, classical Organ and electronic) and I can quickly bottom out 12" bass units!!, did consider sealed EQ route but have never really liked that and this will just make performance demands on the bass units greater I would probably test 15" units in this application.

So I have 4 number 18" JBL 2245H bass units, these need new surrounds do I go with them using two drivers per side or look for new more modern 18" units?

The point of indecision is the bass driver layout with two units per cabinet I can remain with the FC layout the sealed box to achieve the Q I want ~ 0.5 to 0.6 (depending upon drivers) is around 400 litres, I can house this in my room

One idea that has floated around for some time is to use the driver pair in an 'Isobarik' configuration. The cabinet will be smaller (not a quarter as I will use Q = 0.5) and will have to be deep to resist forward / back rocking motion.

The advantages will be reduced overall sensitivity matching mid and treble better and possibly greater bass extension?

In both layouts all drivers will be in three separate modules and decoupled from each other.

At the present time I am researching three or 4 alternative 18" drivers to the JBL units.

Crossover points will be 250 Hz Bass 2700 Hz mid to treble.

Simon
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Offline kengale  
#36 Posted : 31 October 2019 13:49:56(UTC)
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Originally Posted by: Simon Briggs Go to Quoted Post
Winter project will be to build small test enclosure(s) for the mid / treble, whip up suitable passive crossovers etc. and then just listen.

Bass section some indecision remains, I really like the idea of using a pair of bass units in Force cancellation.

The kind of music programme I listen to generally has considerable LF bass content (Symphonic, classical Organ and electronic) and I can quickly bottom out 12" bass units!!, did consider sealed EQ route but have never really liked that and this will just make performance demands on the bass units greater I would probably test 15" units in this application.

So I have 4 number 18" JBL 2245H bass units, these need new surrounds do I go with them using two drivers per side or look for new more modern 18" units?

The point of indecision is the bass driver layout with two units per cabinet I can remain with the FC layout the sealed box to achieve the Q I want ~ 0.5 to 0.6 (depending upon drivers) is around 400 litres, I can house this in my room

One idea that has floated around for some time is to use the driver pair in an 'Isobarik' configuration. The cabinet will be smaller (not a quarter as I will use Q = 0.5) and will have to be deep to resist forward / back rocking motion.

The advantages will be reduced overall sensitivity matching mid and treble better and possibly greater bass extension?

In both layouts all drivers will be in three separate modules and decoupled from each other.

At the present time I am researching three or 4 alternative 18" drivers to the JBL units.

Crossover points will be 250 Hz Bass 2700 Hz mid to treble.

Simon

Not a fan of Isobarik. Yes, it means that you can reduce the cabinet volume to a half for any particular performance for that driver, but at the expense of halving the load impedance, and no change in voltage sensitivity. And of course the implication that the trapped volume between the drivers experiences no change of pressure is not true, i.e. it's not isobaric.

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Offline Steveh100  
#37 Posted : 31 October 2019 13:57:05(UTC)
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For all Isobaric's potential disadvantages, it does seem to bring something to the party in the way of good bass with good rhythmic flow. Like all things hifi, in the end there is no substitute for experimentation.
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Offline Simon Briggs  
#38 Posted : 31 October 2019 14:00:14(UTC)
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Originally Posted by: kengale Go to Quoted Post


Not a fan of Isobarik. Yes, it means that you can reduce the cabinet volume to a half for any particular performance for that driver, but at the expense of halving the load impedance, and no change in voltage sensitivity. And of course the implication that the trapped volume between the drivers experiences no change of pressure is not true, i.e. it's not isobaric.



Sometimes it can be useful to reduce cabinet size and I don't like using the 'Isobarik' for anything else other than for bass duty, due to the 'springiness of the trapped volume, one can partly get around the impedance issue by selecting 16 ohm bass units.


I designed and built a two way Isobarik system years ago, and didn't like the mid performance. I hear the negative effects of the second driver nearly every time, even in modern systems

Edited by user 31 October 2019 14:28:16(UTC)  | Reason: Not specified
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Offline Simon Briggs  
#39 Posted : 31 October 2019 14:04:34(UTC)
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Originally Posted by: Steveh100 Go to Quoted Post
For all Isobaric's potential disadvantages, it does seem to bring something to the party in the way of good bass with good rhythmic flow. Like all things hifi, in the end there is no substitute for experimentation.


Particularly if the sealed box system is not half the volume of an equivalent single driver system, but say ~ 25% smaller with a resultant system Qtc nearer to 0.5

Edited by user 31 October 2019 14:10:12(UTC)  | Reason: Not specified
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Offline kengale  
#40 Posted : 31 October 2019 23:04:26(UTC)
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Originally Posted by: Simon Briggs Go to Quoted Post
Originally Posted by: Steveh100 Go to Quoted Post
For all Isobaric's potential disadvantages, it does seem to bring something to the party in the way of good bass with good rhythmic flow. Like all things hifi, in the end there is no substitute for experimentation.


Particularly if the sealed box system is not half the volume of an equivalent single driver system, but say ~ 25% smaller with a resultant system Qtc nearer to 0.5

All the speakers I have professionally designed have been active - and this was over 40 years ago! But I have been designing amplifiers and matching for underwater applications for the best part of 30 years and just take it for granted that the transducers will be designed for the best coupling to the environment, and that any changes in system Q for best response can be controlled not only by the matching circuits (the equivalent of passive crossover designs) but by changing the output impedance of the amplifier itself. And this impedance can be negative when one wants to lower the system Q in some part of the spectrum - but of course you can only do this when you know that the amplifier will always see the load it is designed for. At the bottom of the spectrum the lowest frequency band I have been involved in is 25Hz - 250Hz, 1 x 60kW, and the highest 5MHz-10MHz, 32 x 5W. I've been tempted to get back into speaker design but I really don't have the time, but if I did it would definitely be active with one amp per band and all band limiting/shaping, sensitivity matching, etc being carried out before the amps.
The real problem would how I would test/develope such a design: when I was doing loudspeaker design I had a pretty good semi-anechoic studio plus decent measuring equipment for most of the work, and for extreme bass responses I used real-world "free-field" - a large grassy field outside the studio with the speaker facing straight up to a microphone on a very long pole above. It was a bit weather-dependant though!
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