Side mounted woofer x-over freq

[vapor602]

Just wondering if I were planning a slim MTM or MTMW actually and wanted to mount a woofer on the side, what is the highest I should cross from the woofer to mids. I was originally just thinking along the lines of a subwoofer but if I'm using small mids the woofer might need to go a little into the lower 'midrange' frequencies. So I'm wondering if the are any dos and don'ts as far as mounting a woofer on the side of an enclosure. Or is it just a bad idea in general? Are there any phase issues or anything else I should be thinking about?

[killersoundz]

Just wondering if I were planning a slim MTM or MTMW actually and wanted to mount a woofer on the side, what is the highest I should cross from the woofer to mids. I was originally just thinking along the lines of a subwoofer but if I'm using small mids the woofer might need to go a little into the lower 'midrange' frequencies. So I'm wondering if the are any dos and don'ts as far as mounting a woofer on the side of an enclosure. Or is it just a bad idea in general? Are there any phase issues or anything else I should be thinking about?

Uhhhh...If it's a sub (80hz and below) than OK mount it on the side, any higher crossover NO. I would not go there.

[auracle]

Uhhhh...If it's a sub (80hz and below) than OK mount it on the side, any higher crossover NO. I would not go there.

There have been a number of well received designs like this one,

http://www.stereophile.com/floorloud...nht/index.html


that have crossed over from 100 - 150hz. It's a matter of human ability to localize low frequencies. We're not all created equally in this regard but if you stay below 150hz, you have a reasonable expectation that most of the people listening to your speakers will not experience a noticeable degradation in imaging and tonal balance. Technically, you're still in the bass region - not midrange.

[kduggan]

I have heard designs crossed at 200Hz with a 10" woofer, firing toward the center of the room I liked them but if the driver was bounced off the wall it just didn't seem right, when the crossover point was lowered to 160Hz it was great either way.

[Paul Carmody]

This question seems to come up regularly, and never gets much of an affirmative answer.

In theory, below 200 Hz, everything's omnidirectional, so it shouldn't matter where you place the woofer on the cabinet: front, side, back, whatever.

However, there haven't been too many DIY designs using a side-firing woofer, so the verdict's still sort of out there. (The commercial world seems to have embraced it more; but reviews are sort of all over the place) One of these days, I'd like to do my own 3-way with a side-firing woofer so I could make my own conclusions.

In the meantime, I think it's "whatever works."

[johnnyrichards]

Paul, I wonder if side firing woofers are not common in the DIY world because of troubles getting them measured properly?

[m.a.c.]

I owned a NHT Xd system and it had a set of side-firing woofers crossed at 120Hz. One of the main reasons I no longer own that system was due to the poor integration it had between the woofers & satellites. I believe much of what I did not like about the system was due to the side-firing, bipolar nature of the woofers. YMMV.

[killersoundz]

There have been a number of well received designs like this one,

http://www.stereophile.com/floorloud...nht/index.html


that have crossed over from 100 - 150hz. It's a matter of human ability to localize low frequencies. We're not all created equally in this regard but if you stay below 150hz, you have a reasonable expectation that most of the people listening to your speakers will not experience a noticeable degradation in imaging and tonal balance. Technically, you're still in the bass region - not midrange.

I do understand at 150hz the polar response is still relatively omnidirectional but that is a very important midbass region where "warmth" can be defined. I would not want to skimp in that area. There are going to be a lot of other anomalies going on if you go past 80hz with a side mounted woofer in my opinion. With that said I have NO experience with side mounted woofers this is just what I predict. Assumptions are often wrong and I have been wrong plenty of times so I don't know for sure.

[killersoundz]

I owned a NHT Xd system and it had a set of side-firing woofers crossed at 120Hz. One of the main reasons I no longer own that system was due to the poor integration it had between the woofers & satellites. I believe much of what I did not like about the system was due to the side-firing, bipolar nature of the woofers. YMMV.

Yeah I just assume that if you had a side mounted woofer crossed over any higher than 80hz, the separation between the woofer and the midrange is going to be distinct. That's not something you want to stick out like a sore thumb.

[MagicO309d]

With four 10" woofers and only one Mid, I'll bet the KEF Blade concept has a relatively high W/M crossover frequency. Check out how they configured the side mounted woofers and make a "pointsource" claim for the design: http://www.kef.com/gb/conceptblade

[Zero the Hero]

Yeah but the KEFs have the woofers on both sides...

"High performance sound reproduction requires the drivers of a multi-way loudspeaker to generate very similar individual soundfields, especially at the crossover frequencies where the acoustic output switches from one driver to another. This is the reason why the bass drivers in Concept Blade are arranged in symmetrical pairs and are side firing. This way their combined acoustic centre can be arranged to coincide with those of the midrange and tweeter drivers"

[m.a.c.]

Yeah but the KEFs have the woofers on both sides...

So does the NHT Xd.

[xavier]

"So does the NHT Xd."

<playing devil's advocate here>

yes, but the Kef bass drivers are arranged symmetrically around the midrange driver. I'd also wager that their crossover point is a lot higher than the NHT system.

Most of the things I've read about single sided (woofer on only one side of cabinet) side firing systems is that the preferred listening arrangement is with the woofers facing inwards. The NHT sub mentioned above is just the opposite. <shrug>

It's also been my experience that two subs [I]in different locations[I] sound better than one. But that's a whole other can of worms.

[Froste]

I built a MTMW with a sidefire 10" (TL) and crossed at 255hz.
I had no problems with measurements or have the bass localized.
As long as they are 2' or more from a side wall they sound very nice, get them too close to a side wall and the bass can get a bit much.

They did win the Dayton Class at the 2010 MWAF, so I guess they sound OK.

[stinems]

I always think in terms of wavelengths. At 200hz, a wavelength is nearing 6 ft long. I'm going to be generous and get worried about distances greater than HALF a wavelength (lets say 3 ft). If you want to do a third of wavelength, go ahead. Remember that a wave isn't really disturbed by things much smaller than its wavelength. So what do we have to think about?

1. Distance from woofer to mid - This dimension could get close to 2ft or even 3ft. But if it exceeded, it wouldn't be by much, and certainly nowhere near a full wavelength.
2. Size of woofer (ie, inherent directivity of the driver due to its size) - Not a concern. I'd guess ten inch woofers usually start exhibiting appreciable directivity due to cone geometry until 500hz (my gut).
3. Size of the baffle on which the driver is mounted - Unless your side baffle is 2 to 3 foot deep, you're not going to get any directivity due to baffle loading. A 200hz wavelength is going to wrap right around a 16" deep box with an 8" wide front baffle.

So yeah, I'd feel comfortable using a 10" woofer at 200hz, and probably to 250hz if you used a slope of at least 12 or 18 db/oct.

Room boundaries are a notably different issue. Depending on where you intend on placing the speakers within your room, and depending on if you are going to integrate subwoofers on the floor, you may want to slide the woofer up the side instead of down on floor. Or you may not.

I don't know whether the "150hz rule" is based on psychoacoustics or relative to the Schroeder frequency (maybe our psychoacoustic development is related to the phenomenon that the Schroeder frequency describes??), or merely marketing. But I really wouldn't worry about it in this situation. Its not like you're placing the woofer across the room. It should easily be correlatable to the mid if its tucked just a foot or two underneath the mid.

Also, the woofers on BOTH sides of the enclosure....cool idea, but it has nothing to do with the localization of the woofer(s). @m.a.c. - subjectively what bugged you about your XD system? That sub was NOT exhibiting any actual bipolar acoustic behavior if it was operated within its intended frequency band. Are we sure that NHT sub didn't use a passive radiator anyway?

Cheers,
Sam

[auracle]

I do understand at 150hz the polar response is still relatively omnidirectional but that is a very important midbass region where "warmth" can be defined. I would not want to skimp in that area. There are going to be a lot of other anomalies going on if you go past 80hz with a side mounted woofer in my opinion. With that said I have NO experience with side mounted woofers this is just what I predict. Assumptions are often wrong and I have been wrong plenty of times so I don't know for sure.

Actually, I have recent experience building a side firing woofer tower with outboard crossovers. That setup made it easy to hook up my BBE DS48 and play around with crossover points. Back in the late 90's I built a similar sized tower - also with a 12 inch woofer - although with a much longer transmission line that didn't perform nearly as well. From my experience, you can readily cross over as Paul indicated up to 200hz - depending on the slope. I generally use 24 db/octave slopes but if you go to 12db/octave - you may have to reduce the crossover point. As the crossover point is increased however beyond 150 hz, I've experienced variability in output while walking in close proximty (within 5 feet) between the speakers. Keep in mind, the half wavelength for 150hz is 45 inches. The half wavelength for 80 hz is 85 inches. This helps explain why noticeable unevenness can be experienced at frequencies as low as 175-200hz.

As far as I'm concerned, the side firing sub produces the best bass in the average listening room (rectangular in shape). I've found that locating ports and sub drivers at 90 degree angles to the longest room dimension is least likely to excite room resonances. And I'm not alone with this sentiment. Check out Sandy Gross' stuff or the new Blade from Kef. Side firing subs are where it's at.

[johnnyrichards]

Are we sure that NHT sub didn't use a passive radiator anyway?

Cheers,
Sam

Dual driver, fully active with butloads of EQ. And I agree, any problems with the bass was not due to the physical arrangement of the subwoofer.

[auracle]

I built a MTMW with a sidefire 10" (TL) and crossed at 255hz.
I had no problems with measurements or have the bass localized.
As long as they are 2' or more from a side wall they sound very nice, get them too close to a side wall and the bass can get a bit much.

They did win the Dayton Class at the 2010 MWAF, so I guess they sound OK.

Nice job Ed. Are the sub drivers meant to point outward or inward on your build? I've never tried outward (tweeters are offset so my design is mirror imaged like NHT's) in any of my builds. I looked at the NHT's back in the 90's and more recently at the big Rockports. I figured both were set up with the sub facing inward to boost pressure at the listening position so I followed suit.

[m.a.c.]

Dual driver, fully active with butloads of EQ. And I agree, any problems with the bass was not due to the physical arrangement of the subwoofer.

And you base that on having owned a set?

Like I said, they didn't suit me and the integration with the sats was a sore spot. I had two of the Xd woofers (4 drivers) and as I mentioned they operate in bipole mode.

My experience with the Xds "side-firing" woofers was enough to sour me on the entire concept. Perhaps I would have preferred a non-bipole implementation. And in any case, YMMV.

@sam - Two problems. There was a noticable suckout that I could not eliminate with placement or phase reversal; and the bass just sounded "phasey". The visceral impact in the crossover region was lacking. All drivers in the XdW are active - no PR.

[auracle]

And you base that on having owned a set?

Like I said, they didn't suit me and the integration with the sats was a sore spot. I had two of the Xd woofers (4 drivers) and as I mentioned they operate in bipole mode.

My experience with the Xds "side-firing" woofers was enough to sour me on the entire concept. Perhaps I would have preferred a non-bipole implementation. And in any case, YMMV.

@sam - Two problems. There was a noticable suckout that I could not eliminate with placement or phase reversal; and the bass just sounded "phasey". The visceral impact in the crossover region was lacking. All drivers in the XdW are active - no PR.

I see the Xd as having more in common with a dual driver bass cube than a side firing tower - the baffle size among other things making all the difference in the world. The cabinet height contributes a few things - volume, increased distance pressure wave travels inside enclosure, and increased focusing/concentration of energy (reduced energy loss from wavefront wrapping around cabinet) In a word, the bass I've been able to extract from a single 12 inch sub mounted close to the floor on the side of a 30 inch by 68 inch cabinet is phenomenal. I can see that cutting baffle height in half for this case would have a drastic impact on performance.