A big three way system based upon the Volt RV4564 18" Bass unit

[darkmatter]

As an exercise at this stage, I am assessing the possibility of designing a big three way system based upon the Volt RV4564 18" Bass unit.

The bass driver will be used in a large reflex cabinet probably around 300 litres, tuned to around resonance. Their datasheet alludes to this possible alignment.

I might even consider a TL, but that might follow as part of the assessment process.

Selection of midrange drivers and tweeters is next.

Crossover will be passive third order as I like these and prefer modelling with them.

Tweeter is likely to be a top Scanspeak or Seas such as the 29TFF/W H1318 or the high end Crescendo T29 or more likely one of the Seas 35mm domes. As a lower cost I like the Audax TW034X0 which is sensitive enough. I already have these. Equalisation as part of the design process or TL loading will mean the tweeters specified will be a fine match.

Now comes to selection of the midrange.

Crossover point will likely be 300 Hz so this might rule out the big Volt dome unit. So likely to consider a cone unit but which one?

Using a third order APC reverse polarity BP filter means one gets back ~2.5 dbs of bandpass gain so this means that cone units of around 90 d/bw would be a fit.

The Seas MCA15RCY H1262 is a possible fit having a smooth response with minimal work required, it can handle a 300 crossover point fine, it works down to 100 Hz.

So now looking for suitable midrange candidates.

Simon

 

[Tony L]

That is a very interesting driver, I’d never seen the back of one before and assumed it had a conventional basket on the rear!

I’ve nothing much of value to add about the rest other than a personal preference for infinite baffle or horn cabs and a liking for the widest possible mid-band. The one thing I really love about my La Scalas is the mid-horn covers a very wide range so in many ways they behave as a single driver as the crossover points are high and low. The closer you get to a full-range driver with a sub and supertweeter I suspect the more seamless and coherent the end result will be.

 

[martin clark]

Proper big, sensitive speaker build; I shall watch this with interest

 

[wow&flutter]

The 15” version has found a home in some pretty expensive kit. Must admit I never knew it was a Volt driver used in the big PMC.

https://pmc-speakers.com/products/consumer/se-series/bb5-se-active

 

[Vinny]

The 15” version has found a home in some pretty expensive kit. Must admit I never knew it was a Volt driver used in the big PMC.

https://pmc-speakers.com/products/consumer/se-series/bb5-se-active

And a mere £28K at that too! (For some seriously ugly speakers....)

 

[david ellwood]

The 18" volt has a sensitivity of 93db and an effective mass of 235g coupled to a reflex cabinet you are going to have enough potential output

to drive a mid size concert hall. the bass will wallow and boom but there will be plenty of it.

The 12" version in a sealed cabinet would be my choice with 1/3 the moving mass and still 91.5db efficient but much better at starting and stopping.

 

[darkmatter]

The 18" volt has a sensitivity of 93db and an effective mass of 235g coupled to a reflex cabinet you are going to have enough potential output

to drive a mid size concert hall. the bass will wallow and boom but there will be plenty of it.

The 12" version in a sealed cabinet would be my choice with 1/3 the moving mass and still 91.5db efficient but much better at starting and stopping.

Yes this is a paper exercise at the moment, I have a Krell 700cx which will be the prime amp for these, my last really big project was a system based loosely on the Wilson X1 but with superior midrange and tweeter drivers, my bass cabinet was larger too and achieved a better in room bass than the Wilson, so I was told!! I did not agree with Wilson's bass voicing and chose to do it how I thought it should be done!

They were featured in the April 2002 issue of HiFi News / Record review readers system section.

Get the bass alignment right, the 18" Volt will be fine and produce quite well timed bass. The main problem is many commercial speakers are compromises and don't always get the tuning right due to many factors, too small bass cabinets, poor design and incorrect tuning methods used.

Much fun ahead

 

[darkmatter]

That is a very interesting driver, I’d never seen the back of one before and assumed it had a conventional basket on the rear!

I’ve nothing much of value to add about the rest other than a personal preference for infinite baffle or horn cabs and a liking for the widest possible mid-band. The one thing I really love about my La Scalas is the mid-horn covers a very wide range so in many ways they behave as a single driver as the crossover points are high and low. The closer you get to a full-range driver with a sub and supertweeter I suspect the more seamless and coherent the end result will be.

Yes Tony, ultimalely my preferred alignment for bass duties is a low Q sealed box where Qtc in box is = to or less then 0.5, this bass alignment integrates well in room and provides a 'fast' well timed bass delivery, I am just interested to see what the Volt does.

I have also designed two other bass cabinets, incidently both low Q alignments just below Q=0.5 one using Isobaric loading with a pair of JBL 2245H woofers which models extremely well and funny enough the same 200 litre net enclosure with four KEF B139 bass drivers in Isobaric again two forward / two internal both produce close to 20Hz in room bass performance.

The beauty of Isobarik loading is it adds mass to the bass driver (two cones instead of one), reduces driver resonance, halves the required enclosure volume for a single driver (Vas halves) a small increase in power handling and improvements in linearity (double magnet shove) / distortion is also reduced.

 

[mondie]

Have you looked at Acoustic Elegance, one of the few modern manufacturers of high efficiency drivers?

 

[darkmatter]

Have you looked at Acoustic Elegance, one of the few modern manufacturers of high efficiency drivers?

Yes, wished they had a UK distributor.

 

[James]

It's great to see another loudspeaker designer here. I've retired from the hobby for at least 5 years, maybe longer. But I still have an interest in the latest crop of drivers and what design potential they hold. In your case, the biggest constraint is finding a midrange driver with both the sensitivity and range to pick up from the big Volt. I've used the Seas MCS15RCY before, and it's no great shakes. If you can find a pair of Seas M15CH001, you might get closer to a pure mid that has both range (300Hz - 3kHz) and sensitivity (90dB/2.83V). Failing that, you could try PHL drivers. They make professional-grade drivers that sound great, albeit they need a bit more contouring/correction. If you can't find a single midrange driver that'll do the job, how about a pair wired in parallel and oriented on an M-T-M array with a tweeter of choice? That should take care of voltage sensitivity to match the big Volt.

 

[darkmatter]

James, Hi.
Yes been a designer since my teenage and regret not doing it fully professionally, as I have had some great results
Useful feedback on the Seas midrange and looking at my design, a parallel or series pair of units makes real sense. Will check out the Seas M15CH001 unit, I also have four Scan Revelator units that can work well from 300-3k as well.
As I did in my last big project will mock up some midrange enclosures and get listening.
Simon

 

[Julf]

The 12" version in a sealed cabinet would be my choice with 1/3 the moving mass and still 91.5db efficient but much better at starting and stopping.

While I agree, I prefer stating it as "and can cover a wider frequency range". Speaker manufacturers specify frequency response or recommended crossover frequency, not "starting and stopping ability" (basically the same thing).

 

[darkmatter]

With the crossover topology I will be using, third order with nearer 3 dbs of bandpass gain, this driver will not require too much work

Volt BM228.8

However I will check which ScanSpeak Revelator midrange units I have in stock

 

[James]

Yes been a designer since my teenage and regret not doing it fully professionally, as I have had some great results
Useful feedback on the Seas midrange and looking at my design, a parallel or series pair of units makes real sense. Will check out the Seas M15CH001 unit, I also have four Scan Revelator units that can work well from 300-3k as well.
As I did in my last big project will mock up some midrange enclosures and get listening.

The Seas M15CH001 has not been produced for some years. You are likely to find only NOS or used examples, and even then they will be quite rare. For a short time, when I was promoting my E-IIIR build, Seas had a few units left for sale, but that was over 10 years ago.

I'm a big fan of Scan-speak drivers. Had I pursued my 11th design, I would have used the 32W/8878T00 woofer with the 18M/8631T00. The 32W is particularly suited to a sealed system that can produce adequate bass without resorting to EQ, a huge box or demanding lots of power and current. In my mind, I have already designed my tribute to the Yamaha NS-1000M, but I've not yet got past my own inertia that is rooted in my complete satisfaction with a pair of the real things.

 

[darkmatter]

The Seas M15CH001 has not been produced for some years. You are likely to find only NOS or used examples, and even then they will be quite rare. For a short time, when I was promoting my E-IIIR build, Seas had a few units left for sale, but that was over 10 years ago.

I'm a big fan of Scan-speak drivers. Had I pursued my 11th design, I would have used the 32W/8878T00 woofer with the 18M/8631T00. The 32W is particularly suited to a sealed system that can produce adequate bass without resorting to EQ, a huge box or demanding lots of power and current. In my mind, I have already designed my tribute to the Yamaha NS-1000M, but I've not yet got past my own inertia that is rooted in my complete satisfaction with a pair of the real things.

What tweeter?

I like the NS1000 as well particularly the crispness of the bass which is excellent in my view.

Fascinating as I had toyed with the idea of a modern take on the NS1000. The 32W/8878T00 was on my list as well!!, As a diversion from this I even looked at 15" units including one from SB Acoustics which modelled well in sealed enclosures, not a homage to the NS1000 in any way, but a large 3 way system with sealed box loading in its own right. For me Seas and Scan are more likely the way I will go for midrange drivers, but am not ruling out the Volt driver mentioned above.

I don't think the Volt VM752 could work with the 18" as it can't really be used below around 400Hz.

With a third order BP filter and with gain this could be made to work quite well. I won't rule out the Scan 18M/8631T00 or a parallel pair of 13M 8640 units (They sound very nice btw) though it may be an ask to transition from an 18" bass to a pair of these? Anyway I am busy modelling.

One design I have seen uses the 13M-8640 from around 250 Hz but nearer 400 Hz may be appropriate as it is a small cone, so maybe this one is not sensible.

Research continues.

 

[Tony L]

Have you considered horns for the mid and top? I have a feeling if I were going real cost no object high-end I’d be looking for a really good big 2” tractrix mid horn running as wide as possible maybe crossing to a ribbon super-tweeter, or if that presented too many efficiency issues another horn.

 

[darkmatter]

Have you considered horns for the mid and top? I have a feeling if I were going real cost no object high-end I’d be looking for a really good big 2” tractrix mid horn running as wide as possible maybe crossing to a ribbon super-tweeter, or if that presented too many efficiency issues another horn.

That is a real possibility for another project, I have been thinking about. I quite like the idea which I had been investigating, but not this one.

 

[darkmatter]

Here are a few thoughts / notes as part of the project evaluation process.

I am currently evaluating a large design based upon the Volt RV4564 18" Studio Bass Transducer.

The main issue that I have is to consider which midrange driver would be appropriate.

The 3 way 3rd order crossover will be passive at this stage. filter points of 300/2400 Hz approx.

The bass alignment will be 300 litres reflex tuned to around the bass Transducer's resonance (subject to experimentation)

Front Baffle size 1110mm x ~ 560mm

I have resolved which tweeter to use, but am currently looking carefully at midranges. Whilst the VM752 would work with the 15" I think it would be a bit of an ask for it to to work with the 18" as the crossover point for the 18 would be sensibly around 250-300 Hz

One unit I have looked at carefully is the Volt BM228.8 which has a smooth rolloff characteristic into the high midrange.

My only minor concern remains its sensitivity. It should work well if I used a third order APC (reverse polarity bandpass) filter which results in a bandpass gain of around 2.5 dbs. My target system sensitivity is around 92 dbs so there should not be any issues. It remains the favourite at this stage, it looks easy to work with. 3rd order APCs are fairly easy to design and work well, these are my favourite filter regime.

SJB Dec 17

 

[James]

What tweeter?

I like the NS1000 as well particularly the crispness of the bass which is excellent in my view.

Fascinating as I had toyed with the idea of a modern take on the NS1000. The 32W/8878T00 was on my list as well!!, As a diversion from this I even looked at 15" units including one from SB Acoustics which modelled well in sealed enclosures, not a homage to the NS1000 in any way, but a large 3 way system with sealed box loading in its own right. For me Seas and Scan are more likely the way I will go for midrange drivers, but am not ruling out the Volt driver mentioned above.

I don't think the Volt VM752 could work with the 18" as it can't really be used below around 400Hz.

With a third order BP filter and with gain this could be made to work quite well. I won't rule out the Scan 18M/8631T00 or a parallel pair of 13M 8640 units (They sound very nice btw) though it may be an ask to transition from an 18" bass to a pair of these? Anyway I am busy modelling.

One design I have seen uses the 13M-8640 from around 250 Hz but nearer 400 Hz may be appropriate as it is a small cone, so maybe this one is not sensible.

Research continues.

I have a soft spot for Hiquphon tweeters. I've used the OW-1 and OW-3, but I've also had great results from Seas, Scan-speak and Morel.

My last design entailed a very low XO between woofer and mid (circa 150Hz, actively filtered) to enable the mid to cover the full range of the human voice. But I think asking a mid to go that low compromises mid and upper bass impact. If I were to redesign that again, I'd cross at 300Hz or above. So your instincts on using the 13M from 400Hz upwards accords with my experience, and it's easy enough to use a passive filter without the fs resonance of either driver pair getting in the way.

I'm curious about your choice of 3rd order filters. I've used first, second and third order electrical filters but they are always targeted at even order LR2 or LR4 acoustic transfers. Are you referring to 3rd order acoustic or electrical?

You are getting me itching for another design.