Simming it in WinISD, the box volume doesn't affect max SPL too much. In a closed box, you're pretty much xmax limited and the 15PR400 doesn't have a lot.
180L only gives you a couple of dB's. You do get a nicer roll off.
You can still hit 105dB @ 50Hz in 80L. Depending on your situation, that might be more than enough.
180L only gives you a couple of dB's. You do get a nicer roll off.
You can still hit 105dB @ 50Hz in 80L. Depending on your situation, that might be more than enough.
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I read the whole thread and you seem to have big room and few subs as well, and experience of a sound you didn't like. I suggest to figure out all the ways you can think of to improve the previous bass box and then build a prototype that address all the issues and evaluate how well it works. Few evenings of work and you are progressing 
Think out how the whole system comes together as well, there migh be other reasons in system level why would you prefer smaller or bigger box. If you dont like it, few evenings more and you get another chance with another proto
I've found on a big three way speaker the bass equally hard as mids to get together, but I have a mono system only and could be other reason than the box so hard to say yet. Crossover and positioning for example, but I feel there is still sound of the cabinet as well. I have had problems with mids leaking through the port, cabinet sound, build difficulties and what not. Multiple prototypes have made progress but still not very good I have reduced the box size on every proto, not sure what next until rest of the system gets tweaked. At least the construction will be more high tech I think
Think out how the whole system comes together as well, there migh be other reasons in system level why would you prefer smaller or bigger box. If you dont like it, few evenings more and you get another chance with another proto I've found on a big three way speaker the bass equally hard as mids to get together, but I have a mono system only and could be other reason than the box so hard to say yet. Crossover and positioning for example, but I feel there is still sound of the cabinet as well. I have had problems with mids leaking through the port, cabinet sound, build difficulties and what not. Multiple prototypes have made progress but still not very good
I have reduced the box size on every proto, not sure what next until rest of the system gets tweaked. At least the construction will be more high tech I think
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Hmm, based on published specs + 0.5 ohm for wiring losses [~0.351 Qts'] its upper mass corner where T/S design theory peters out is ~200 Hz, so just using HR's Wizard, the box can be as little as ~40 L before it begins affecting its phase response > 250 Hz where the mid-range begins and of course increases peak power handling.
In short, it's the driver's mass controlled BW combined with the baffle/whatever loading, room modes that dictates its midrange intelligibility and since it's also the XO point, its design will dominate, so ideally 1st order.
I’m curious about the new Precision Design PD.153C002. The motor is stronger, the cone is lighter and Xmax is greater than 15PR400. It’s also a decade newer design and the price is right. However inductance is higher and the impedance peak and Qms are lower, plus vintage is seldom a good indicator of audio SQ
”The PD.153C002 Bass / Mid Range Driver offers excellent linear response and is well controlled down to 45Hz. Working seamlessly up to 5kHz with 101db sensitivity across its working bandwidth. Thanks to a copper shorting ring and copper CCAW wire the unit also offers impressive, extended high frequency performance. A very good solution for two way or multi way systems, the driver also excels when combined with Precision Devices 1-inch compression drivers. The driver has been carefully developed using the latest, high-quality component materials and state-of-the-art design tools. Further optimisation and verification has been performed with the use of the company’s in-house Klippel facility to provide system designers and audio engineers who seek no compromise solutions with significant, measurable performance advantages.”
FWIW some of the highest SQ 15" woofers ever are Altecs with 1.3-1.4 mH [Le], so assuming PD's specs are ~ accurate, then its inductance is low enough.
Speaking of which, though GPA/Altec doesn't list [Le], the PD's specs are very close to its 515-8G, a many decades proven high SQ horn driver: http://greatplainsaudio.com/wp-content/uploads/2016/06/515_G.pdf
Speaking of which, though GPA/Altec doesn't list [Le], the PD's specs are very close to its 515-8G, a many decades proven high SQ horn driver: http://greatplainsaudio.com/wp-content/uploads/2016/06/515_G.pdf
Yes they are very close as can be seen https://www.diyaudio.com/forums/multi-way/100392-beyond-ariel-1403.html#post4591991. I think it’s a very interesting driver.
[BTW what happened to the prices of GPA drivers?!? The 416-8B was $360 each when I looked into ordering sometime before the pandemic and now they’re like 3-4x that!! Might as well keep an eye out for the real thing instead of these clones now… ]
Re the importance of Le and what’s an acceptable level, John @ AE likes to argue that it’s most important thing with TD15M having as low as 0.2mH.
https://web.archive.org/web/20010810141852/lambdacoustics.com/library/whitepapers/bl_mms.htm
Bill was apparently going broke just basing prices on inflation from when Altec was selling who knows how many drivers/year plus the tooling he inherited was worn out and IIRC the vendors were increasing minimum orders over time, so no choice if wanting to stay in business, much less grow it, but the way I understand it from a 'long range' POV, so strictly a 'FWIW/YMMV', somewhere along the way he sold it with him keeping the repair business and apparently some of the new products with just the 604 being of interest to the new owners, i.e. specifically 'their' new 604E S2, plus set pricing.
Well, to accurately reproduce sound, the system must be able to replicate a square wave and to do that requires a flat amplitude and phase response, so yes, a zero inductance = flat impedance/phase is required and why Altec [among others] used impedance correction on their high speech intelligibility [SQ] systems.
Yes, been seeing some very [in some cases] reasonable prices on FB in recent weeks.
Well, to accurately reproduce sound, the system must be able to replicate a square wave and to do that requires a flat amplitude and phase response, so yes, a zero inductance = flat impedance/phase is required and why Altec [among others] used impedance correction on their high speech intelligibility [SQ] systems.
Yes, been seeing some very [in some cases] reasonable prices on FB in recent weeks.
I have had a pair of the TAD Berylium compression drivers in the past and I'm now using the B&C DE250 instead. I actually like the DE250 more. The TAD drivers were salvaged from an old PA set so they could have been a little worn out even though the PA was only used in a theatre, not in a concert hall or dance club.