Nice curves... - Scan-Speak 15M/4624G

[GranteedEV]

Re: Nice curves... - Scan-Speak 15M/4624G

Troels Gravesen really looked into foam surrounds here

[Pete Schumacher]

Re: Nice curves... - Scan-Speak 15M/4624G

Hi,

Thanks for the input fellows, in terms of obtaining a constant power directivity requirements(from a separate thread) a 4" mid(10F) would be a better match to a ribbon tweeter like Fountek CD3.0 or Raal than the 5.25"(15M) mid. If that is the case what would be the best x-over point? The x-over point should be greater than 3Khz and less than 6Khz. If it is greater than 4KHz then 10F is a better choice.

We ran a 6" wavecor with the 70-10D, crossing around 3200Hz, and could probably have gone a little lower. Horizontal off axis response plots were pretty smooth to 45 deg. No doubt the 10F would be even better, but there's really no reason to cross much higher than 3000Hz with that particular RAAL.

[ttan98]

Re: Nice curves... - Scan-Speak 15M/4624G

Hi,

Thanks for the input fellows, in terms of obtaining a constant power directivity requirements(from a separate thread) a 4" mid(10F) would be a better match to a ribbon tweeter like Fountek CD3.0 or Raal than the 5.25"(15M) mid. If that is the case what would be the best x-over point? The x-over point should be greater than 3Khz and less than 6Khz. If it is greater than 4KHz then 10F is a better choice.

[Pete Schumacher]

Re: Nice curves... - Scan-Speak 15M/4624G

I agree, as long as this driver is used for its intended purpose and not crossed too low, its' HD distortion performance will probably not really need to be considered in the design. If both of these drivers were crossed from say 300hz to 2500hz, then I don't think you would be able to distinguish lower HD performance when comparing them.

I was just pointing out that the 15M will probably not have quite as low distortion as the 10F. Will anyone be able to tell? I don't think so, and if someone said they could tell, I would need it to be done in blind listening test to be able to believe them.

Chris

Well, driven to the same levels, the 15 will have a distinct advantage in that whatever displacement it does have, it will be significantly less than the 10, regardless the power level or frequency.

No doubt that either will make an excellent mid unit.

[czag]

Re: Nice curves... - Scan-Speak 15M/4624G

My opinion, and I'm sure many of you will disagree, is that there is an over-emphasis on absolute distortion numbers in evaluating drivers. It's what I might call "the latest and greatest syndrome". This is not to say that it doesn't matter, but everything has a point of diminishing returns. Give me a good driver/motor with smooth and extended response with good polar response in my intended bandwidth.

dlr

I agree, as long as this driver is used for its intended purpose and not crossed too low, its' HD distortion performance will probably not really need to be considered in the design. If both of these drivers were crossed from say 300hz to 2500hz, then I don't think you would be able to distinguish lower HD performance when comparing them.

I was just pointing out that the 15M will probably not have quite as low distortion as the 10F. Will anyone be able to tell? I don't think so, and if someone said they could tell, I would need it to be done in blind listening test to be able to believe them.

Chris

[dlr]

Re: Nice curves... - Scan-Speak 15M/4624G

I would bet the HD would fall somewhere in between that and the HD of the 18W8434 seen below since the 10F has a copper cap and this one only has an aluminum shorting ring. Now that is still a great place to be for a midrange under $100, much less the $55 this one goes for.

This brings up a point to make. This is a midrange unit and extra care must be taken to not over-drive it. But then this is no different than for any driver. Certainly the quality of the motor is going to contribute to how much output of the low end of the driver range is possible and for woofers and midwoofers it's a bigger factor. For any good driver with a good motor, except for the case where someone is trying to wring every last mm of displacement from a driver, the distortion is probably not nearly as important because most of the time, we aren't listening at max levels. I know that I seldom do. I probably have never come close to Xmax of any driver except when testing the limits of a system. With a 2-way, if I really need more extension, I'd add a subwoofer and highpass the 2-way. Then again, I likely won't be listening at levels high enough very often, so that 2-way won't be taxed excessively anyway. If you will be, different design considerations then enter. But I suspect that with most of today's good drivers, the T/S parameters are more of an issue than are the absolute distortion numbers.

If someone has a system that in regular use is approaching Xmax or maybe to the point where distortion really is entering the picture, either the system should be improved in any of various ways (better driver, larger driver, multiple drivers, etc.) or they're going to damage their hearing. In either case, I would not be spending any amount of time in a room with that level of SPL.

My opinion, and I'm sure many of you will disagree, is that there is an over-emphasis on absolute distortion numbers in evaluating drivers. It's what I might call "the latest and greatest syndrome". This is not to say that it doesn't matter, but everything has a point of diminishing returns. Give me a good driver/motor with smooth and extended response with good polar response in my intended bandwidth.

dlr

[czag]

Re: Nice curves... - Scan-Speak 15M/4624G

Here's the 10F from Zaph's blog. I've no doubt the 15M would be similar, if not better. This is superbly clean midrange performance.

I would bet the HD would fall somewhere in between that and the HD of the 18W8434 seen below since the 10F has a copper cap and this one only has an aluminum shorting ring. Now that is still a great place to be for a midrange under $100, much less the $55 this one goes for.



Chris

[Pete Schumacher]

Re: Nice curves... - Scan-Speak 15M/4624G

Hmmm. Nice woofer. Would like to see some distortion measurements.

Here's the 10F from Zaph's blog. I've no doubt the 15M would be similar, if not better. This is superbly clean midrange performance.

[sunandmoon]

Re: Nice curves... - Scan-Speak 15M/4624G

Hmmm. Nice woofer. Would like to see some distortion measurements.

[dlr]

Re: Nice curves... - Scan-Speak 15M/4624G

Everybody else saw: "foam surround" and decided to pass, I saw "foam surround" and I thought to myself: "ah, this driver is going to be good...".

Nothing wrong with foam. I noticed the foam surround when they first came out. That's a big part of the smooth response, I'm sure. The 21W/8554 used it, I've got a pair purchased used. They still look new. As a treated foam, they should last, from what I've read, maybe 30 years. Yet there are frequently those who post that they won't use a driver with foam because of a preconceived notion of it being inferior.

SS has been making drivers with foam that last 20-30 years for a very long time.

dlr

[ttan98]

Re: Nice curves... - Scan-Speak 15M/4624G

Hi,

This no follow up of this driver because no one that I know of have use this driver in their design. I am thinking of using it instead of the Discovery 10F which I understand is being used by a few designer incl. John K. This driver(4624G,92.4dB) has better sensitivity compared to the 10F(89dB).

Is there anyone out there who can contribute their knowledge on this driver confirming what Critofur had obtained?

Thanks in advance.

[tpremo55]

Re: Nice curves... - Scan-Speak 15M/4624G

Thans for sharing... I've had my eye on that one for a future project.

[Pete Schumacher]

Re: Nice curves... - Scan-Speak 15M/4624G

Flatter, yes, smoother, perhaps not. Now, with two crossover components, you might match the flatness, but will you have a design that doesn't need BSC?

Yes!!! Just use a real woofer to fix the baffle step problem!!!

[critofur]

Re: Nice curves... - Scan-Speak 15M/4624G

You think? Check scale . . . mine's on a 5dB/div, yours is on 10dB . . . ;)

Flatter, yes, smoother, perhaps not. Now, with two crossover components, you might match the flatness, but will you have a design that doesn't need BSC?

[Pete Schumacher]

Re: Nice curves... - Scan-Speak 15M/4624G

I've got no problem with foam surround as long as it withstands the test of time. Visual appearance is another thing of course. This driver, even with the foam surround looks pretty damn sexy. I haven't seen it in person, but it looks like they've color matched the foam to the cone pretty good.

Nice, beefy frame too.