8" high efficiency midbass driver suggestions

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#201
@Ro808 Thats a dramatic difference considering the cone diameter deficit, it's in line with my perception on the 8NDL51. The lower mids on up are musical, dynamic and highly resolving. This driver will take quite a bit of input before it starts to compress or strain. Very few mids can match the detail retrieval, even above the typical usage range. On top of that, as a range limited woofer with a bit of EQ on the low end, it will surprise in terms of how much air it can actually move in a ported cab. That's despite this enclosure type not sounding as snappy as a smaller sealed box in midbass applications.

A small mod that helps with lower level motor noise on the 8NDL51 is adding some 3/16 holes to the spider's sides. This decompresses the spider underside so the air being pushed past the VC gap isn't as audible. I wouldn't do this on a continuous very high output midbass application as it would compromise power handling, but in most situations its a non issue. A larger diameter, blunt tip on a soldering iron makes quick work of this. A total of 8 holes are all that's needed.

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#205
profiguy said:
@Ro808 Thats a dramatic difference considering the cone diameter deficit, it's in line with my perception on the 8NDL51. The lower mids on up are musical, dynamic and highly resolving. This driver will take quite a bit of input before it starts to compress or strain. Very few mids can match the detail retrieval, even above the typical usage range. On top of that, as a range limited woofer with a bit of EQ on the low end, it will surprise in terms of how much air it can actually move in a ported cab. That's despite this enclosure type not sounding as snappy as a smaller sealed box in midbass applications.

A small mod that helps with lower level motor noise on the 8NDL51 is adding some 3/16 holes to the spider's sides. This decompresses the spider underside so the air being pushed past the VC gap isn't as audible. I wouldn't do this on a continuous very high output midbass application as it would compromise power handling, but in most situations its a non issue. A larger diameter, blunt tip on a soldering iron makes quick work of this. A total of 8 holes are all that's needed.

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A proper indicator is the sound of the naked driver - full range without any filtering, mounted in a vented cab, tuned at (about) 60 Hz.
 
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#208
The only 2 way I've ever built with the 8NDL51 was with the DE360 on the ME20 horn as an MTM. I dont have crossover specs anymore being i designed it just before my last PC's hard drive crashed. I can tell you I crossed it at 2.5k 3rd order for a PA application. It had hifi clarity over 110 dB at 5 ft distance crossed to a sub above 100 hz. Fullrange with the box tuned to 60 hz, the low end was very surprising, almost unbelievable. One of these boxes would comfortably take 400W all day. The DE360 is a ring radiator and sounds like a large HF dome on the ME20 horn. There's only a small 3 dB peak at 3.6k on the 8NDL51 that needs to be flattened with an LCR to get the last little bit of clarity, but in MTM arrangement, the mid peak will shift depending on baffle width, so there's more fine tuning needed if you want the last word in flat FR.
 
#209
profiguy said:
@Ro808 Thats a dramatic difference considering the cone diameter deficit, it's in line with my perception on the 8NDL51. The lower mids on up are musical, dynamic and highly resolving. This driver will take quite a bit of input before it starts to compress or strain. Very few mids can match the detail retrieval, even above the typical usage range. On top of that, as a range limited woofer with a bit of EQ on the low end, it will surprise in terms of how much air it can actually move in a ported cab. That's despite this enclosure type not sounding as snappy as a smaller sealed box in midbass applications.
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You hit the proverbial nail on the head.

Your modification may be useful for some applications, but absolutely not necessary for 'hifi at home'.

In addition to the measurements, there's a deeper level at which a driver and the intended application can be considered.
 
#213
profiguy said:
The only 2 way I've ever built with the 8NDL51 was with the DE360 on the ME20 horn as an MTM. I dont have crossover specs anymore being i designed it just before my last PC's hard drive crashed. I can tell you I crossed it at 2.5k 3rd order for a PA application. It had hifi clarity over 110 dB at 5 ft distance crossed to a sub above 100 hz. Fullrange with the box tuned to 60 hz, the low end was very surprising, almost unbelievable. One of these boxes would comfortably take 400W all day. The DE360 is a ring radiator and sounds like a large HF dome on the ME20 horn. There's only a small 3 dB peak at 3.6k on the 8NDL51 that needs to be flattened with an LCR to get the last little bit of clarity, but in MTM arrangement, the mid peak will shift depending on baffle width, so there's more fine tuning needed if you want the last word in flat FR.
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that's sounds like an awesome speaker ! are you saying that you needed to be 5 feet away for the output frome the woofers and tweeter to combine properly ? could you angle the woofers slightly so it could be used at closer distance .
 
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#214
IamJF said:
How did you get those measurements? Nearfield? What mic did you use? What's the noise floor?

Cause that's exactly what I don't want to see from a driver - THD at lower levels keeps the same and don't goes down. Ist it H3 at lower levels or H2?

SB 10" woofer also behave that way (measurements in the forum) and 18Sounds 8NMB420.
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The nearfield distortion tests at 2.83V, 4V, 8V, 16V RMS were done by Scott Hinson.

He included a warning:
"Do not attempt to do nearfield distortion tests like this unless you understand how loud nearfield SPL measurements can/will be."

In this case the SPL at ~1/4" from the dustcap was in excess of 150dB.
A special purpose high SPL Josephson microphone was used (C725, US$ 10.250,00), capable of measuring 165dB @ 5% THD.
This was about 15dB under that so the microphone distortion should be under the noise floor of the measurement.

Scott also tortured the driver with 10 tone test signals in a 100°F (38°C) garage for hours and compared it to a 7" high-end woofer, probably something in the range of a Scan-Speak Illuminator or SEAS Excel:

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