Double 10 and Horn

[Peter Morris]

Both speakers are excellent - FWIW I used the 8NW650 in my lined array - at the time it was slightly better than what B&C had on offer but B&C have some new drivers that can match it now.

The limiting factor for low frequency performance is usually Xmax and the speakers ability to remain linear and not have the cone's position bias in one direction when driven hard. Newer speakers tend to be much better in this respect as they have been designed with the help Kipple measurements.

My double 10 is crossed at 110Hz to the sub (double 18" 18NLW9601) and 650Hz to HF950/BMS4594 .... if you go any lower with sub crossover the 10" driver will be a noticeable limit on the systems max output.

This boxes has been one of the most useful speakers I have ever owned; the double 12 came about as a result of looking for something best describes as a super version of this box.

 

[Kristoffer Reiersen]

I have settled for 10nw650. The HE version was not available in time for my deadline (event coming up), but I managed to get my hands on a couple of regular 4594nd for this build, hope the difference is not night and day. Build is coming along nicely, aiming for the MTM alignment, just because of looks, I find it really appealing for some weird reason. Will post pictures in a while.

Also I have decided for a large slot port at the bottom. Maybe I will experiment with tubes if the unsymmetrical look bothers me, but I want to try to get the port as close to the ground as possible for stand alone use. Do you recommend stuffing or acoustic foam or similar?

 

[Grant Manson]

Hey I've been looking into building a "budget" version of this double 10. What do you guys think about using the RCF ND840 1.4" + Faital Pro 10FH520 (or) B&C 10MBX64?

I love Mikesound's design, do you think either of the above 10" drivers would work well in this design?

I know I would loose some SPL but all the above divers combined would cost around the same as a single BMS4594

The plan is to sit one of these above 2 or 3 THAM15's crossing over somewhere around 100/140hz.

Any advice would be much appreciated!

 

[Peter Morris]

I would suggest the RCF ND950 or a B&C DE1090TN with the HF950 ... doing that you can use a crossover frequency around 650 to 700Hz.

I think there are many 10's that will work very well including the 10FH520 or B&C 10MBX64, 10NW76, Beyma 10MC700ND, Eighteen Sound 10NW650, 10NW750, RCF MB10N305 ... you would just need to adjust the box volume and tuning.

My first version of the double 10 used an RCF ND850 with an EV HP94 horn. It worked well, but their were directivity and phase cancellation issues caused by having a crossover frequency around 1200Hz .... the latest version crosses at 650Hz .... and its soooo much better.

BTW RCF has just released a double 10 - the TT4a and its using a 4" diaphragm HF driver and a 3" VC 10"

Mikesound's design looks good, but to get that MTM idea to work well you will need a cross over frequency around 650 - 700Hz (as a guess) ... This is what I would do (or similar) if I was designing the box in 2020.

 

[Grant Manson]

Thanks for that info Pete! Very helpful

Out of interest, Looking at the Frequency charts supplied by RCF, It looks like the ND840 would go down to 650 (see attached) but obviosuly theres something i'm missing here Still relatively new to speaker building and trying to learn!

I assume you can mount the ND840 to the HF950 horn?

 

[Peter Morris]

Hi Grant,

One of the limiting factors with a compression driver is Xmax at the lower frequencies. A 4" diaphragm has 177% more cone (diaphragm) area than a 3" and can therefore produce more SPL especially at the lower frequencies we are talking about.

Normally a 3" diaphragm has better VHF performance, but in this case (RCF 850/840 Vs 950/940) the 4" diaphragm seems just as good if not a little better.

The double 10 design we are talking about has quite reasonable SPL capabilites, probably a bit more an RCF TT5a, TT4a etc.

I have not measured the ND840 or ND950 so I'm guided by what RCF are doing with the speakers above which all use a variant of the ND950, only the TT2a, 22a use a 3" diaphragm driver like the ND840. The double 10 is noticably more powerful than these 12' speakers.

 

[Grant Manson]

Pete, thanks for going into a bit more detail.

The larger diaphram probably explains why, based on rcf's charts, the ND840 has a much sharper fall off at the low end compared to the ND940.

Looks like i'll be going with the B&C 10MBX64 & ND950

 

[Peter Morris]

Hi Grant,

The roll off you see can also be a function the cut off frequency of the horn they used for the test. In this case RCF don't say but I suspect they used the same horn for both driver tests.

Here is the ND 950 on the HF 950 and the B&C DE1090

https://audioxpress.com/article/Test-Bench-RCF-ND950-Neodymium-Compression-Driver-and-HF950-Horn

https://audioxpress.com/article/test-bench-b-c-speakers-de1090tn-compression-driver

 

[Grant Manson]

Hi Guys,

I've started to build my dual 10" and plan on using the HF950 Horn for most applications.

In some specific applications I might need a 60° horn. Obviously the Eighteen Sound XT1464 horn would be ideal but this is much wider and deeper than the HF950 so i was wondering if any of the following horns might work:
- Eminence H14EA (loading to 600hz supposedly)
- Eighteen sound XR1464C
- RCF HF64

I know there will be a compromise using the more compact horns but i'm just looking for a bit of extra flexibility without having to build extra cab's.

Cheers,
Grant

 

[Peter Morris]

Hi Guys,

I've started to build my dual 10" and plan on using the HF950 Horn for most applications.

In some specific applications I might need a 60° horn. Obviously the Eighteen Sound XT1464 horn would be ideal but this is much wider and deeper than the HF950 so i was wondering if any of the following horns might work:
- Eminence H14EA (loading to 600hz supposedly)
- Eighteen sound XR1464C
- RCF HF64

I know there will be a compromise using the more compact horns but i'm just looking for a bit of extra flexibility without having to build extra cab's.

Cheers,
Grant

The problem when you use a narrower pattern horn is that it needs to be bigger - this new horn from Ciare http://oem.ciare.com/pdf_oriz_3.php?info=450 also looks interesting ... just a bit wider than the HF950.

I suspect you will get good results crossing over at 800Hz or less with a double 10" box .... I know there are issue once you go higher as the 2 x 10" speakers start to "phase cancel" as you come off the vertical axis.

 

[Max Warasila]

I've been playing with the 10MBX64 lately. It's a fantastic driver, but it doesn't go particularly low (it's a midbass driver so go figure). If you're going to be matching it with subwoofers anyway, I think it's a fantastic choice. If LF performance is more important, an alternate choice may be the 10NW76 or the 10NDL64 offerings (within the B&C product stack, anyways).

 

[Joris Wijgerde]

Quick question that I can't seem to find a good answer to.
When talking about center to center spacing it appears that the measurement is usually done from the center of the woofer to the center of the mouth of the horn.

Does that mean that this is where the acoustic center is supposed to have shifted towards? Does the same count for midrange drivers?
In this case I'm wondering whether this spacing trick would work the same if the midrange woofers were to be moved back about 30cm (1ft) in a simple straight horn, maintaining the vertical spacing when measured from both horn mouths.

Of course if the answer to this is yes, the question immediately becomes whether more vertical spacing can be permitted if the vertical directivity of the horn is manipulated. Are we simply looking at a good match between both vertical and horizontal directivity here?

 

[Peter Morris]

Hi Joris,

If a sound wave hits an object that is less than ¼ of a wavelength in size it goes around the object like it wasn’t there. Similarly if you place 2 sound sources within ¼ of wave length they will combine like they are one source. At higher frequencies they won’t combine and you will begin to get phase cancellation producing lobes in the coverage pattern.

The trick I’m trying use with the double 10 and the PM90/60 is to have a crossover point so that the 2 / 3 sources combine without any lobbing.

The problem at low frequency end of the horn’s operation is its directivity will not match the nominal coverage angle; it will be much wider and more or less controlled by its width and height, not the angle of its walls. If the low frequency driver is a similar size to the horns mouth its directivity will be similar to the horn.

When the horn has control of directivity at higher frequencies its mouth will be large with respect to the wavelength it’s producing and you will not be able to get the two sources to behave as one as mentioned above.

Because the HF horn and the 10” driver have some directivity at the crossover point it does help to reduced lobbing at the crossover when you model it compared to an omni source. What you find in practice with typical horns and drivers we use is you can get away with almost ½ wave length spacing and still get very acceptable results.

The obvious question is why not use a tighter pattern horn … well the horn has to be bigger to get the directivity control and then the driver spacing is increased and you have achieved nothing.

 

[Joris Wijgerde]

HI Peter,

Thank you for your explanation.

The relation between mouth size and directivity does explain a lot. I've noticed something similar when slot loading woofers, which seems to push the narrowing in directivity up higher in frequency but seems to be limited by the bandpass effect it creates.

In my case I have 8 pieces of the Fane Pro 300 driver which I would like to use and a bms 4592nd coaxial compression driver on the 2236 horn (lower cutoff of 500Hz, 60x40, 498 mm x 348 mm) which I have been experimenting with.

As you can see (and of course this is obvious when testing this combination) the horn is very big compared to the drivers which doesn't allow for a layout like the one you posted. I have so far tried to put 2 woofers side by side (which more of less matches the width of the horn) with good results, however I was wondering whether the size of the horn would permit me to put the woofers more towards the back of a trap cabinet, having a horn/waveguide whose mouth is as wide as the mouth of the CD horn.

The alternative would be to ditch either the horns and go for something like the xt1464 with a B&C464 (which would be ok for me since is actually 1/3 cheaper than the bms where I live) or pick a bigger woofer and cross lower (my least favorite option).

A second reason for having the coverage extend from the entire width of the baffle (if this makes any sense) is that these cabinets will be arrayed horizontally, playing from 180hz. I was planning to build trap cabinets which match the nominal directivity of the CD horn (30° in this case).

Any advice is welcome

 

[Peter Morris]

I suspect what you are planning to do will work. The concept will be different to my box. It was designed to be light, around 25 Kgs and small so it could easily be pole mounted on top of a double 18” sub.

 

[Grant Manson]

This one is for @Jaroslav Mikyska & @Peter Morris

I've just finished building a pair of dual 10's based on Jaroslav's design. So far so good!

As expeceted there is a peak around 300hz thats easily eq'd out using my DSP.

The issue im getting is that there is a big dip (-8db) at 450hz & 650hz from the dual 10's. I've not put any dampening material inside the box yet as I am waiting for it to get delivered, do you think this would solve my issue?

- I had the Tweeter turned off so i could see what the 10's were doing.
- Using a pair of Faital Pro 10FH520's. The volume and ports were slightly adapted to fit these.
- Testing was performed outdoors @1m. (see attached)

 

[Peter van Gils]

The issue im getting is that there is a big dip (-8db) at 450hz & 650hz from the dual 10's.

Probably because you’re measuring not close enough or not far enough from the ground. In other words: this could be caused by ground reflections and the difference in travel time between the direct sound and the reflections. Try to measure half space with the mic (and speaker) on the ground.

 

[Grant Manson]

Probably because you’re measuring not close enough or not far enough from the ground. In other words: this could be caused by ground reflections and the difference in travel time between the direct sound and the reflections. Try to measure half space with the mic (and speaker) on the ground.

Thanks for the suggestion. I tried it indoors, on the floor with the mic closer and it did reduce the notch at 450hz a little

The main issue is that there is still a large notch around 650-750hz which is right where I want to crossover

I'll try and get some graphs up for you to see.

 

[Grant Manson]

You can see the readings attached. Blue was the full range reading, green is just the 10" speakers.

I've also attached drawings of the adapted design. Only real diffrence is I simplified the bracing and adjusted the ports to match my driver.

 

[Peter van Gils]

You can see the readings attached. Blue was the full range reading, green is just the 10" speakers.

I've also attached drawings of the adapted design. Only real diffrence is I simplified the bracing and adjusted the ports to match my driver.

Did you put the box on its side on the ground? Can still be a travel distance between the two 10” drivers. Also put the mic exactly on-axis.