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Josh Ricci just uploaded a pile of data on the X21 cabinet from WW-Speakercabinets I designed with the B&C 21DS115-4 mounted in the cabinet. I sent him an iNuke 3000DSP with the modeled filters loaded in to show what it can do with modest power, and he tested this case along with his big 20kW amplifier.

Of course Josh is an over-achiever, so he jumped on the idea he suggested in this thread where plugging one port drops tuning to about 14.5Hz and tested again with each amplifier. The single 6" flared port results were interesting enough that I came up with some generic filter settings that would work with any DSP that has high/low shelving filters and can set a high pass down to 20Hz (= iNuke DSP compatable).

For the 21DS115-4 as tested with 14.5Hz 1 port tuning I have the following filters recommended:
1. BW 12 / 2nd order high pass at 20Hz (2nd order Q=0.7 filter)
2. A 2nd order Low Shelf at 20Hz boosting 6.0dB
3. A 2nd order High Shelf at 90Hz cutting 14.0dB

This gives a response that is +/-3dB from 14-200Hz, and should be useful to around 12Hz in-room. Here is what I modeled up where this is just generic, so the exact shape may vary by a smidge:



I'm going to look into some options for port plugs and it is always possible to have WW eliminate one port as they are all built to order. We could also have WW offer rear panel cut-outs for the SpeakerPower plate amps, and SpeakerPower could load the recommended filters in any of the HT series amplifiers. Since the last posts here the price has been brought down a little further. A fully assembled cabinet this large and with this type of construction will never be cheap, but it's certainly interesting for those who don't have the work space required for such a large build.
 

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Josh Ricci just uploaded a pile of data on the X21 cabinet from WW-Speakercabinets I designed with the B&C 21DS115-4 mounted in the cabinet. I sent him an iNuke 3000DSP with the modeled filters loaded in to show what it can do with modest power, and he tested this case along with his big 20kW amplifier.




I'm going to look into some options for port plugs and it is always possible to have WW eliminate one port as they are all built to order. We could also have WW offer rear panel cut-outs for the SpeakerPower plate amps, and SpeakerPower could load the recommended filters in any of the HT series amplifiers. Since the last posts here the price has been brought down a little further. A fully assembled cabinet this large and with this type of construction will never be cheap, but it's certainly interesting for those who don't have the work space required for such a large build.

congratulations mark. strong showing in the third party validation of your x21.
 

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Wow impressive numbers Ricci got from this test to. Glad I bought 4 of these drivers.
congratulations mark. strong showing in the third party validation of your x21.
Thanks guys. For those interested in seeing how the filters work out, I added the filter parameters above the graph in my last post. I hope some find it interesting to see how the visualization of the graphs are affected by simply flattening the frequency response as was done with the iNuke in standard operation. I didn't have time to dial in any limiting before I sent it to Josh, but a little bit of playing would add quite a bit of increased playback level and tolerance for the amplifier to not overload as audibly nor possibly cut out. Of course we're talking about a $279 amplifier with DSP included. There are quite a few options between there and a Josh's K20. :)
 

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Have you thought about making a revision with longer ports for a lower tune without sacrificing compression on the low end?
Until you go to a driver like the Focusworks/Funk, or other higher excursion woofer, it's hard to say that we are really giving up that much in the way of compression. On the highest sweep before the driver or amp started significantly giving out we only see about 3dB of compression. Compare that to many other subs measured by Data Bass. Even the Cap 4000ULF shows more compression around port tuning despite higher output elsewhere from the much larger box.

For many reasons I have already looked into a deeper tuned cabinet, and one of the strengths here was getting the tune as low as practical without having to bend the port. It is certainly possible to tune lower in this cabinet, but only if you have a suitable bend for the 6" port. This design needed to use readily available parts, and once you try to bend a 6" diameter port, you either can't use the PPI flares or you don't have a simple way to bend the port. The easiest way to tune lower is to make the cabinet deeper, but 32" was about as deep as I felt comfortable with for this type of product. Getting too deep and leaving the sub forward firing starts creating boundary interaction issues with the front wall distance, and gets even harder to place in a room. A shallower enclosure with lower tuning but still the big, free-flowing vent, is something I may pursue with one of my own products with the required custom parts.
 
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Until you go to a driver like the Focusworks/Funk, or other higher excursion woofer, it's hard to say that we are really giving up that much in the way of compression. On the highest sweep before the driver or amp started significantly giving out we only see about 3dB of compression. Compare that to many other subs measured by Data Bass. Even the Cap 4000ULF shows more compression around port tuning despite higher output elsewhere from the much larger box.

For many reasons I have already looked into a deeper tuned cabinet, and one of the strengths here was getting the tune as low as practical without having to bend the port. It is certainly possible to tune lower in this cabinet, but only if you have a suitable bend for the 6" port. This design needed to use readily available parts, and once you try to bend a 6" diameter port, you either can't use the PPI flares or you don't have a simple way to bend the port. The easiest way to tune lower is to make the cabinet deeper, but 32" was about as deep as I felt comfortable with for this type of product. Getting too deep and leaving the sub forward firing starts creating boundary interaction issues with the front wall distance, and gets even harder to place in a room. A shallower enclosure with lower tuning but still the big, free-flowing vent, is something I may pursue with one of my own products with the required custom parts.
Good point, I was just looking at the graphs quick from the K20 and saw about 5db of compression on the vent... but wasn't paying close attention that there was also that much on the top end... no real point...
 

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Got two pieces of new 8NDL64 for some development purposes. I´m again quite disappointed by the noise coming from the magnet and "cooling system". It´s significant even at mathematical Xmax of about 3mm, and gets worse towards datasheet value and even Xvar, where it´s really excessive. Like, worst I´ve encountered to date. Somebody mentioned this for 12" version, and I didn´t believe. Got caught too.
Anyway I´ll try to mount it to the supposed enclosure in hope it will cease or disapper as it happened to me with some other B&C drivers.

//Managed to find out that it´s the spider itself. It´s single piece without silicone "injection" and air probably goes trough it a little bit, which makes the noise. Now the driver is generaly exceptionally good. I see no substitute for the money. So here goes madness.
I have three choices what to do:
1) Sell it and use another, less suited driver. Err, I don´t want to, and this one exactly is best for my purpose. Soooo....
2) Mod it - add something to the spider so it gets quieter - of course, it will change speaker parameters, and will not be easily repeatable.
3) Mod it, and actually take out some parts of the spider. Again. Will change parameters, and might change power handling (worse).

Soo, what do I do...
 

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I would wait to see how it sounds in enclosure. After that I would mod it if it were me. I tend to buy things very slowly because of bad drivers I have gotten over the years. I havent had any problems with BC products but I dont buy a LOT of products. I will be buying some BC mids in the next month though.
 

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Yes, that will be the first thing to do. Maybe it will get better. This is the first driver from B&C where I consider the amount of noise as a serious problem. Time will tell ( as I´ll find some time for the box development). I´ll get back once I try these in the box. Don´t hesitate to buy B&C products because of my experience though. They do mostly awesome stuff....
 

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Managed to find out that it´s the spider itself. It´s single piece without silicone "injection" and air probably goes trough it a little bit, which makes the noise.

Perhaps paint the spider with silicone caulk/sealant.

Given how soft it is and how stiff spiders are, I doubt that it would lower the compliance significantly.
 

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Yes, I was thinking about that one. But if it is even possible, one has to be quite careful, as every piece on the speaker, and it´s properties, has its reason. I might "alter" and ruin some of that. Also this speaker is already very stiff and has high Fs. That one would propably go even higher, which is no good for my purpose. So one has to know what he´s doing, or one has to have enaugh money to develop the mod too (until it works as intended). The problem is, that there is no stock of these drivers around. I have already bought last pieces, and next batch will probably come in MONTHS.
The noise coming from the speaker is very loud. It might also be, that when I seal it, It stops, but some other similarly loud sounds will remain, as these might be caused by other pieces of the driver, and masked by the current "problem". It´s not straight forward to mod a speaker...
 

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Got two pieces of new 8NDL64 for some development purposes. I´m again quite disappointed by the noise coming from the magnet and "cooling system". It´s significant even at mathematical Xmax of about 3mm, and gets worse towards datasheet value and even Xvar, where it´s really excessive. Like, worst I´ve encountered to date. Somebody mentioned this for 12" version, and I didn´t believe. Got caught too.
Anyway I´ll try to mount it to the supposed enclosure in hope it will cease or disapper as it happened to me with some other B&C drivers.

//Managed to find out that it´s the spider itself. It´s single piece without silicone "injection" and air probably goes trough it a little bit, which makes the noise. Now the driver is generaly exceptionally good. I see no substitute for the money. So here goes madness.
I have three choices what to do:
1) Sell it and use another, less suited driver. Err, I don´t want to, and this one exactly is best for my purpose. Soooo....
2) Mod it - add something to the spider so it gets quieter - of course, it will change speaker parameters, and will not be easily repeatable.
3) Mod it, and actually take out some parts of the spider. Again. Will change parameters, and might change power handling (worse).

Soo, what do I do...
I suspect the noise you are describing is in fact airflow noise between what looks to be narrow vents between the top plate and basket and the back plate/VC gap vents on the rear. Airflow noises are largely concealed in an enclosure, more so in a sealed enclosure, and almost certainly a non-issue for pro use. In a quiet home it will depend on the box design and if there are large open ports. Fortunately airflow noise doesn't get coupled to the cone body well, and is more easily contained in the box. Lead ticking and noisy/scraping spiders are mechanically coupled and can be heard even in a sealed box.

Test it in a box before you dismiss it.
 

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Mark, thank you very much for valuable informations. For testing purposes, it should be relatively easy to block those holes/vents you speak about. I'm afraid that from the broadband spectrum of sounds it does, it's rather the spider itself, even when I cannot confirm that for sure for now. I'm thinking exaclty that - sound tranfer trough the speaker basket or cone, tot the front. That would be bad. Anyway, I'll try everything and report back. Leads are out of discussion. They're well executed, the sound doesn't change with different shaping or evn tension, and there is no way it could do so much distorted noise.... Vents or spider. Nothing in beteen.
 

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Hey folks,

The 8NDL64 uses an inside slug magnet, which keeps weight and cost down considerably. It also means the central pole is blocked, so all cooling airflow must go around the outside of the magnet structure - whereas in a ring magnet configuration we can pump air through the middle as well. This generally results in higher noise. In-box this can be controlled with padding and vent placement, but every design is unique. Some woofers are dead silent in one design and quite loud in another.

Anyway, as Mark suggests, please try this woofer in your box to see whether it will work for you.
 

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Hello Bennett!
Thank you for detailed description. You always bring valuable data and details which are not very obvious from datasheets. 8NDL64 didn't look like cheaper choice to me in this respect, but now after your description, I know better how to choose from B&C products. That alone is totally worth the speakers price I paid for. Everything bad is good for something. I bought just two pieces because with "one man in a garrage" development, the project might easily end up as failed. So no surprise and general disappointment here. Just bad decision and compatibility with my expectations. As a good customer, I've been even offered to get these back for full price, but as the speaker really is awesome for its price (except for those noises), I cannot easily run from this problem and pick different model.
I might have some chance to alter the box to help this issue. Speaker/vents padding and vents positioning might be possible. Also I would rather require this quiet/hi-fi performance at moderate output levels, and at max SPL, there might be some additional noise allowed. Four pieces for midtops pair might still do the job without issues. I'll continue on the box development to see how it ends up.
Best regards.
Petr.
 

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@bennettprescott What is the best way to ask you some questions on BC products? I sent you a PM but wanted to add one more question to what I already asked. Thanks either way.
Hey Chrslygsdfkjh,

Always best to email me: [email protected] Then I can easily get technical responses from Italy and get back to you.
 

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I might have some chance to alter the box to help this issue. Speaker/vents padding and vents positioning might be possible. Also I would rather require this quiet/hi-fi performance at moderate output levels, and at max SPL, there might be some additional noise allowed. Four pieces for midtops pair might still do the job without issues. I'll continue on the box development to see how it ends up.
Hey Petr,

The 8NDL64 is a crazy good deal, probably our highest performance 8" and almost our cheapest as well. Just hits that convenient sweet spot. Anyway, for hi-fi applications I normally recommend something wider bandwidth like the 8MBX51 or the 8BG51. The NDL series is designed for line arrays, so full range enough but light weight and high power first of all - and assuming subwoofer support.
 
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