W15gti

[emilime75]

New guy here. Been lurking for a while and finally decided to join.

I've got a pair of the W15GTI's currently being used as HT subs at home. I'm replacing them with something else and want to build 3 way towers with them once they're freed up. I know there's been some debate as to just how high these will play cleanly, some say 1k+ and others say 200 and down, if that. More importantly, even though this will be a fully active speaker system, I'd like to come close to matching up the efficiencies of all the drivers used and I'm having a hard time figuring out what the actual efficiency of these things is.

JBL specs say 92dB at 2.83v/1m. I know at 8 ohms that equals 1w/1m but, when a woofer presents either a 3 or 12 ohm load, what happens to that spec?

Thanks.

[honkytonkwillie]

A speaker's sensitivity spec is dependant on a whole lot of parameters, not just impedance. It's also important to know how a given sensitivity spec was measured. A common standard is to measure 1kHz at 1W/m, but often they're measured at a different frequency somewhere in their working range, or over a specific range using pink or white noise.

Using this speaker in a three-way, I'd take a slightly different approach. Some speaker designers measured/assumed/arbitrarily-decided that about half of the power in the spectral content of "most music" is below 300 or 400Hz, and the other half of the power lies in the higher part of the spectrum. So with the GTI, I'd aim for a crossover point in this region, and then figure out a way to measure sensitivity of that part of the system.

[emilime75]

Thanks, Willie. My original thought was to mate it with an Usher 8948a. Not sure if many of the folks here are familiar with the Usher brand but, it's a good hifi driver. According to Usher, it measures 88dB/1W/1M, ±3dB at 300, 400, 500 and 600Hz. The 8948a was used as the bottom in some of Usher's flagship speakers a few years back and it has a fantastic midrange. I'm guessing the 8948a and the W15GTI will have similar efficincies, although I plan on having double the power on the GTI's. In my head, I thought a crossover point somewhere between 100-150Hz would be ideal.

[Aaron]

I think using a higher sensitivity woofer like this will just about automatically make up for baffle step losses especially if you cross things over around where baffle step starts to take effect. How wide will your box be?

[emilime75]

Not sure what happened, but my IP got blocked from the forum for quite some time. Nevertheless, this is still a thought in progress.

The baffle will likely be as wide as is necessary for the 15" woofer, so about 17-18". Or, I can make these as 2 separate boxes, with the mid/high section narrower than the woofer enclosure. For what it's worth, I kinda like the idea of the wide baffle.

As far as woofer to mid crossover, I'll cross that bridge once they're built and I've had the opportunity to take measurements. I'm fairly certain I'll be able to find a suitable point where both drivers are content.

[toddalin]

You could run the W15GTi up to 800 Hz and cross it over to a 2425. The 15 is fairly linear up to ~1kHz. I do this with W10GTis and have already worked out the crossovers. They use the same motor asemblies and should perform similarly except you'll get a couple more dB and better bass extension.

[emilime75]

Todd: Yes, I've seen your posts touting the WxxGTI's ability to play up high...and the doubting responses. Not disagreeing, or agreeing with you, but a 3 way this still will be.

Aaron: Do you consider the W15GTI to be a high sensitivity woofer? I'm not seeing it as one, not when compared to "pro" drivers, like the 2226, for example.

[toddalin]

Definitely not high sensitivity.

When I made crossovers, I had to pad the 2425s/butt cheeks way down to use them with the W10GTis in my four surround speakers. These give up ~8 dB to the modified L200 cabinets (AlNiCo 2235 woofers) and I would expect the W15s to give up ~6 dB. Could be on the order of ~10 dB to a 2226.

[Aaron]

As far as home or car audio systems go I think it has pretty good sensitivity...most of the home subs I've built in recent history have been in the mid 80s. I kinda felt like the frame of reference was the usher midwoofer mentioned earlier and not pro stuff.