3-Way/Side-Firing Woofer - Measurements for XO Design

[jhollander]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Robert I assume the tweeter was measured on the tweeter axis so the 0,0,0 is OK. Now if the woofer and mid were measured on the mid axis why isn’t the X, Y offset the same for the mid and woofer?

Did you derive the z offset for the mid? The +.35 inches means the acoustic center of the mid is forward of the tweeter in PCD.

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Sure and your sim graph if possible. There are some very talented people here who might have suggestions. I'm not necessarily one of them, but am curious what made you give up on this.

I'll post the additional stuff when I get a chance. Primary reason for giving up is parts cost. I see no way to get the capacitor values under control -- see the xo when I post it. I think it would be cheaper to use a plate amp for the woofer. But maybe someone smarter than I will have a solution.

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Robert I assume the tweeter was measured on the tweeter axis so the 0,0,0 is OK. Now if the woofer and mid were measured on the mid axis why isn’t the X, Y offset the same for the mid and woofer?

Did you derive the z offset for the mid? The +.35 inches means the acoustic center of the mid is forward of the tweeter in PCD.

No, all measurements are on the mid driver axis. The mid driver acoustic center is 0.35" behind the tweeter but, since all measurements were on mid axis, the tweeter is 0.35" in front of the mid. I came to this value using the impulse delay in MLS measurements between the drivers and a bit ..of geometry. It may be off a bit but should be close enough.

[jhollander]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Robert, OK thanks. The offsets make physical sense if the tweeter is below the mid.

If all the drivers are measured from the same point you, did you use the measured phase?

I will not use offsets if the time of flight is already in the measurements.

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Robert, OK thanks. The offsets make physical sense if the tweeter is below the mid.

If all the drivers are measured from the same point you, did you use the measured phase?

I will not use offsets if the time of flight is already in the measurements.

No, I always use minimum phase. It's necessary when combining NF & FF data.

I'll get the xo posted in the morning.

[michiganpat]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

I'll post the additional stuff when I get a chance. Primary reason for giving up is parts cost. I see no way to get the capacitor values under control -- see the xo when I post it. I think it would be cheaper to use a plate amp for the woofer. But maybe someone smarter than I will have a solution.

wouldn't think it was capacitors driving cost, but inductors....cap wise, frankly, IMHO anything over 20 uf or so, just go to NPE.....I'd use NPE's (maybe with a small film by-pass cap on the HP) between the woofer and mid....and as far as inductors, if you don't mind iron core, watch ebay--there's some passive sub XO's on there that if you assume they use textbook 2nd order butterworth LP's have a pair of 10mH iron cores each, and you can pick 'em up for $17 shipped

[jhollander]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

It's my experience that the FR data is not accurate if you measure the drivers from the same point then extract minimum phase.

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

wouldn't think it was capacitors driving cost, but inductors....cap wise, frankly, IMHO anything over 20 uf or so, just go to NPE.....I'd use NPE's (maybe with a small film by-pass cap on the HP) between the woofer and mid....and as far as inductors, if you don't mind iron core, watch ebay--there's some passive sub XO's on there that if you assume they use textbook 2nd order butterworth LP's have a pair of 10mH iron cores each, and you can pick 'em up for $17 shipped

Well, I hadn't considered NPEs. That puts the project back in the realm of the possible.

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

It's my experience that the FR data is not accurate if you measure the drivers from the same point then extract minimum phase.

I've had good success with it -- XO mock-up measurements have always tracked very closely to simulations. But even if measured phase is better, the mid and woofer in this project must be tagged with NF responses so there is no valid measured phase. Or am I missing something?

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Ok, here are the XO and modeled results. I'm not saying that this is a great XO, it's simply where I stopped. Minimum impedance remains close to 4 ohms. The drivers are in good phase in the bandpass regions. However, inductor losses are not yet included.

Note that the low end roll-off would likely not be as bad as it looks due to room gain and the side-firing woofer. (That is, the woofer measurements were taken on mid axis which puts the woofer significantly further from the mic and 90 deg off its axis.)

[taloyd]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

The NHT 3.3 and 2.9 both used 100 Hz. as a crossover point between the side-firing and floor-loaded woofer, and the midwoofer. Ken Kantor is a very competent engineer, and so whatever data can be had about those speakers might prove very relevant for this project. (That said - a plate amp is a good idea - esp. driven by high-level inputs. Perhaps the midwoofer could even be sized such that it rolls off on its own w/o an electrical high-pass network... but I'm just thinking out loud).

Cheers,
-Tal

[michiganpat]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Perhaps the midwoofer could even be sized such that it rolls off on its own w/o an electrical high-pass network

that's how I'd design it, or such that it's natural roll off could be enhanced with a first order electrical crossover (single cap) to achieve a 4th order summed roll-off

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

In case anyone is following this project and using any of the measurements that I've posted, I've done a bit more to capture the correct Z-offset of tweeter relative to mid. The mid appears to be closer to 0.8" rearward of the tweeter. Also, the mid/tweeter y-offset is actually 5.125", not 5.25". Just fyi.

[fatmarley]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Hi Robert,

Just wondered what mid and tweeter you are using? I'm planning on using the same woofer, side firing, but would like to use it sealed and put it near the floor for boundry gain. I'd also like to cross low (around 100Hz) but i'm not sure if my mid and tweeter are sensitive enough?

The mid is the Aura NS6 pdf and the tweeter is the Seas 29TFF W

[Robert Dunn]

Re: 3-Way/Side-Firing Woofer - Measurements for XO Design

Hi Robert,

Just wondered what mid and tweeter you are using? I'm planning on using the same woofer, side firing, but would like to use it sealed and put it near the floor for boundry gain. I'd also like to cross low (around 100Hz) but i'm not sure if my mid and tweeter are sensitive enough?

The mid is the Aura NS6 pdf and the tweeter is the Seas 29TFF W

SB Acoustics SB15NRXC30-8-UC 5" woofer. Hiquphon OW1-Fs 3/4" tweeter.