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

[jhollander]

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

IMO I think it's a better utilization of a decent driver, certainly many more options. Should be fun.

[Robert Dunn]

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

Thus far, all of the acceptable XO sims have priced out over budget. The primary issue is the need to roll off the mid below 100-150Hz which requires large inductors (and caps) to eliminate the impedance hump and a notch filter around 1kHz.

So I'm setting this prototype aside for now and trying a different configuration. (This is the third prototype and I'm definitely getting tired of construction and measuring.) See pics below.



I'm hoping that putting the woofer back on the front baffle will let me cross the woofer/mid higher and, maybe, just maybe, not need to deal with impedance humps, etc., in the XO. Wish me luck.

[Robert Dunn]

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

Thanks Richard. Looking at your post (#7) With boundary gain perhaps the SB29 woofer would work out ok?

I'm pretty sure that it will. I'm still messing around with the prototype trying to find an acceptable XO.

[fatmarley]

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

Thanks Richard. Looking at your post (#7) With boundary gain perhaps the SB29 woofer would work out ok?

[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.

[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

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.

[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

[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

[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.)

[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

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.

[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.

[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

[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.