Zaph's Latest!

[Zaph]

Originally posted by outfitter
I'm in the progress of building this design with a twist. Being very new to DIY speaker building, I am always looking to learn and understand as much as possible with this hobby. With this design, I am building a 2 cu ft tower speaker, with removable baffle and movable shelf braces. My intentions are to try out a few of the different enclosure recommendations. I will be able to do the 1 cu ft sealed, 1.5 cu ft sealed, and the 2 cu ft selaed and ported. I am hoping to understand what sounds best to me in my listening room.

Nice looking build so far. You do your corner fasteners in much the same way I do. After some testing time, let us know what tuning option you like the best in your room, and what your room dimensions are.

[Loiti]

Hello Zaph,

I like your professional website, I guess it's the only place where I can have a look at professional measurements at all.

I am very interested in the new 7" Peerless speakers since they are cheaper than Seas' (especially my favourite CA18RNX) and as good as the Seas in the bass region.
If I ask politely, will you tell me when there is a chance that you measure some of these?

Greetings from Austria,
Loiti

[sdclc126]

"Well, I wouldn't call it problems with the DA175, just limitations of a lower tech motor design. The two types of distortion we're talking about here are thermal and BL. At lower levels, the DA175 performs on par with the Seas L18. As millimeters of Xmax get used up, the DA175's generic flat and straight pole piece causes BL distortion to accumulate faster than some better motor designs that have better BL curves.

Thermal is simply the driver's ability to maintain it's measurements at higher levels as the voice coil and suspension heat up. This can be easily seen in response and impedance curves that are increased in incremental levels. For example, starting at 90 dB/1m, then running response and impedance plots in increments at levels 5 or 10 dB higher to observe the changes.

This kind of testing is still somewhat important, but I usually don't do it due to time constraints. Soundeasy can do Volterra Series Expansion, which is more of an estimate of a BL curve rather than an actual Klippel-style measurement, but still useful. Some day I'll post a set of measurements so you guys can see what this looks like. I'll use the L18 and DA175 too, as these drivers really point out the difference that motor design can make. People want to just add up the Xmax, calculate out the volume displacement and use that to determine how loud a speaker will get, but it's not that simple. A single L18, through most of it's bandwidth, will play louder with lower distortion than two DA175's. Make no mistake that the DA175 is a great woofer, but the higher price of the L18 does get some performance improvements in this case...."

John - do the Dayton RS series woofers have the same limitations as the DAs, or is their motor design more sophisticated, allowing higher SPLs without as much power compression?

[keyser]

Originally posted by sdclc126
"...I'll use the L18 and DA175 too, as these drivers really point out the difference that motor design can make. People want to just add up the Xmax, calculate out the volume displacement and use that to determine how loud a speaker will get, but it's not that simple. A single L18, through most of it's bandwidth, will play louder with lower distortion than two DA175's. Make no mistake that the DA175 is a great woofer, but the higher price of the L18 does get some performance improvements in this case...."

John - do the Dayton RS series woofers have the same limitations as the DAs, or is their motor design more sophisticated, allowing higher SPLs without as much power compression?

Your answer is in the part you quoted.

[sdclc126]

Originally posted by keyser



Your answer is in the part you quoted.

I only see references to DA175 & SEAS L18, but not RS. ??

[Zaph]

Originally posted by sdclc126
John - do the Dayton RS series woofers have the same limitations as the DAs, or is their motor design more sophisticated, allowing higher SPLs without as much power compression?

The RS woofers have a more advanced motor. The pole piece is undercut which always makes for a better BL curve. There's a single faraday ring mounted outside the voice coil on the inside of the magnet.

The DA woofers just have a generic plain straight and flat pole piece. Still, the performance is good for $18 each.

Honestly, I like the DA175 cone better than the RS180 cone. Much more controlled in the upper midrange, and a less harsh breakup without the twin peaks.

[sdclc126]

Originally posted by Zaph


The RS woofers have a more advanced motor. The pole piece is undercut which always makes for a better BL curve. There's a single faraday ring mounted outside the voice coil on the inside of the magnet.

The DA woofers just have a generic plain straight and flat pole piece. Still, the performance is good for $18 each.

Honestly, I like the DA175 cone better than the RS180 cone. Much more controlled in the upper midrange, and a less harsh breakup without the twin peaks.

Interesting! More advanced motor, more expensive, yet somewhat inferior performance. Well, that convinces me - I'm gonna abandon the RS idea. Back to the BAMTM. Since they'll start out in my bedroom and eventually go to a small apartment I'm sure they'll have all the SPL I'll need for the forseeable future.

Thanks John.

BTW - do you have any idea of the weight of the magnets on the DA175s? I'll need to video shield them. PE doesn't even know, but I'm guessing they're around 15 oz.

[keyser]

Originally posted by sdclc126


I only see references to DA175 & SEAS L18, but not RS. ??

My bad

[JonPike]

Well, I wouldn't call it problems with the DA175, just limitations of a lower tech motor design. The two types of distortion we're talking about here are thermal and BL. At lower levels, the DA175 performs on par with the Seas L18. As millimeters of Xmax get used up, the DA175's generic flat and straight pole piece causes BL distortion to accumulate faster than some better motor designs that have better BL curves.

Yeah... "problem" isn't really what I meant, more like at what volume level/power input level do the distortion and compression begin to become noticeable. I've also been thinking about high (clean) dynamic range lately.

I would guess as we get close to Xmax distortion would build up at some increasing rate, and that would be fairly predictable... but I don't have much of a SWAG feel for how fast the thermal builds up. Never have seen a thermal dissipation coefficent published for a speaker's voice coil...

Honestly, I like the DA175 cone better than the RS180 cone. Much more controlled in the upper midrange, and a less harsh breakup without the twin peaks.

Hmmm... could be some potential for the future, if PE redesigns the DA175 motor or adds the cone to a RS series motor... loose the stamped frame... It won't be a $18 woofer anymore, but might end up a different and worthy entry into the RS series...

Now should it get the black anodizing job, or stay silver?

[sreten]

Originally posted by Zaph


At this point, I've done at least 1 or 2 of just about every type of loudspeaker.

Hi,

Well just a suggestion:

A proper 3-way design. Not a fully BSC'd speaker with a sub added.
Possibly an unBSC'd mid/treble with BSC provided by the bass units.

But for a proper design you can choose relative amounts of BSC,
e.g. mid/treble has 2dB BSC upper mid, bass units provide another
3dB lower mid.

The reasons for this ?
Decent efficiency from a good midrange driver.
A good explanation of the issues involved in 3-ways.
Some of us don't have HT recievers, just stereo amplifiers....

Slim tower wise I'd go for high twin side mounted bass units
mounted resiliently in force cancelling mode, mid treble built
into a triangular section in the top.

/sreten.