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Old Audiophile
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Speaker Design

I know virtually nothing about speaker design and didn't do that well in Physics, to boot. That being said, I'm wondering what advantages and disadvantages there are to speaker designs incorporating bottom-firing bass ports, versus rear-firing and front-firing designs. Advertising literature from manufacturers and reviews generally don't go into much depth on this. Hence, my curiosity. From a layman's approach, it would seem to me that pushing air out the bottom of a speaker cabinet, straight down at the floor, would pose more design problems than the other two design approaches if this is, indeed, what a port does. By way of example, I offer this:

(I won't mention any name brands here so as not to risk offending delicate sensibilities.) I recently spent considerable seat-time with two different pairs of speakers both incorporating bottom-firing bass port design, from the same manufacture, under relatively well controlled critical listening conditions (e.g. similar sound rooms; similar source components; same music; similar speaker placement; etc.). The pair that was one step above the other in this same model line sounded absolutely divine, to my ears. I did not A/B these with any other speakers. I listened to them only.

In another sound room, I then A/B'd the pair one step below that same model line with a pair of comparably priced contenders, in a comparable model line echelon, from another manufacturer that incorporates a front-firing port design. I and a friend I was with concluded the pair with the front-firing ports performed a tad better in bass response. We both thought the bottom-firing design speakers were a tad bit more muddy, less accurate, less detailed and just a smidge more boomy in low bass. Both sound rooms involved had thin carpeting on top of either hardwood or plywood subfloors. Both speaker manufacturers involved are highly regarded, have won many awards and have graced the pages of this and many other audiophile publications for years.

Relying exclusively on audio memory, I'd have to say the upper model line speakers from both competing manufacturers sounded absolutely wonderful in every way. I thought they both performed outstandingly well in bass response. Since I did not A/B these in the same room, with the same equipment, etc. there's no way I could honestly say if my ears might have preferred the front port design, however slightly. That would be pure conjecture. Again, I have no clue what the function of a bass port is. I'm assuming the purpose is to either push air or expel residual sound waves from the cabinet, out into the sound room. If so, there have got to be advantages and disadvantages to bouncing these sound waves off the floor, a wall behind speakers or expelling them straight out into a sound room. All things being equal, is this just something that comes down to targeting listener preference? This is very intriguing, to me.

Thoughts?

Kal Rubinson
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My only thought is that your

My only thought is that your experiment falls short of being useful information. It is simply anecdotal. Even if one accepts your observation that the two speakers actually differ in their bass performance (not due to room conditions), there is no reason to presume that such a difference is a consequence of the position of their ports.

Of course, we all try to make that sort of inference but, really, we shouldn't. I am currently listening to two pairs of speakers of similar size and price and, although they are both bottom-ported, their bass performance is quite different (heard and measured). Since it ain't due to port placement, could it be the tuning of the ports with respect to the drivers and enclosure? If your pairs were measured, the FR and the impedance and phase curves would be informative.

BluesDog
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Speaker Port Designs

Whether it is rear, front. downfiring (or a combination!) approach, some of this is using certain types of pressurization to augment the other inherent capabilities of a given speaker. Down firing port designs seem to have been well perfected by Focal with their Aria 926 and, even more so, with their Aria 936. The 936 provides a full court press with DUAL front ports AND a downfiring bass port. The bass port approach kind of reminds me of a sealed downfiring subwoofer but in a more compact, less powerful package within the speaker cabinet. It seems to rely on pressurizing the floor (and rear wall) as a way of augmenting bass pressurization in the room. Recent efforts by the PSB T600 and the Paradigm 100 Founder have been interesting about downfiring port approaches. A fairly expensive but effective speaker design.

A more familiar, effective and less expensive rear port idea is well executed in the Martin Logan 60XTi. With rear port designs, they work well but proximity to the rear (and sidewalls) wall needs some consideration as it relies on boundary gain from the front wall to augment the inherent bass capabilities of the speaker. Too close to the front wall can create boom and other problems. Too far forward and you lose optimum benefit. This is a much less expensive speaker approach that has been utilized in many modest priced speakers.

A front port addition to the drivers of a speaker design (in my experience) provides much flexibility regarding speaker placement in terms of reduced affect from rear and sidewalls. Revel has done an outstanding approach with the front port augmentation in their Revel Performa3 F206 and F208 designs. More expensive then a rear bass reflex approach but maybe less expensive then bottom ports?

All 3 port styles work very well but present different planning issues. With all 3 speaker designs, other factors such as flooring (wood, industrial carpet of a basement or carpet), wall construction (sheet rock, wood, brick), ceiling height, room dimensions and distance to the listener all come into play. Thought should be given as to what design can work well in your room. You are often better off going to actually listen to speakers in a shop that replicates your home conditions (distance to front wall, distance to listener) as feasible. Try to listen to amplification as close to what you currently have to more accurately gauge what you are hearing from the speaker as opposed to hearing the effects of an uber amp beyond what you have at home.

Kal Rubinson
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Considering the frequencies

Considering the frequencies involved, all port placements will be fraction of a wavelength from any wall. So, unless you put a rear-ported speaker nearly flush up against the front wall as to pressure-load it, port placement is not an issue with regard to room boundaries.

Old Audiophile
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Yes, of course!

Yes, of course! My idle musings were never intended to be useful information, per se, or scientific by any means; merely a quest to broaden a virtually non-existent knowledge of speaker design. I guess I should have pointed that out more clearly.

I find speaker design, in general, especially the use of ports, fascinating. Then again, I have the type of mind that finds lots of innocuous things fascinating.

Here's a little audiophile nostalgia. Many moons ago, as a fledgling audiophile, I was told by more than one salesperson that my ears tended to gravitate toward sealed and/or acoustic suspension speakers, versus bass reflex designs. This would be large bookshelf speakers of the late 60's & early 70's; all I could afford in those days. Haven't got a clue why or even if speaker designers used ports in those days. Similarly, I have no idea if EPI, AR, Advent and Ohm bookshelf speakers were sealed and/or acoustic designs back then but I do remember really liking those. Dollar for dollar, under controlled conditions, they always seemed a little clearer, crisper and more accurate, to me, than what I was told were bass reflex designs. The alleged bass reflex designs, comparatively, often seemed a little more muted, less distinct or less detailed. In those days, I was listening to a lot of acoustic music. Maybe that had something to do with it?

I don't know what this might say about my considerably younger ears of that era or, for that matter, what it might say about speaker design but Bose 901 and Ohm F were all the rage for a good long time, back then. One afternoon, a friend and I wandered into Tech HiFi in Cambridge, as we were wont to do in the good old days. Foot traffic was uncharacteristically slow. After a while, a salesperson noticed us snooping about and asked if he could be of assistance. We were quite honest and quickly replied that we were just spending free time kicking tires with no intention of buying anything of consequence. Since this very personable salesperson really had very little to do, we talked about music, audio gear, dream systems and so on. Eventually, he asked if we'd be interested in doing an A/B with the Bose 901 and Ohm F and sharing our opinions, just for fun. He didn't have to twist our arms! I can't honestly recall, precisely, which amplification source was used, which turntable or any of those particulars. However, I'm relatively certain amplification was courtesy of either a McIntosh or Phase Linear powerhouse. A couple of minutes was all I needed to conclude the Ohm F sounded better, by far. My friend, on the other hand, was a little more torn. Now, I know, or think I know, that the Bose 901 and Ohm F are completely different design concepts. Regardless, I can't help but wonder if what those salespeople told me years ago has any validity (i.e. that some people have a predilection for one design over another).

BluesDog
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Tech Hifi Was Da Bomb!

Tech Hifi, back in the day,
Where all great components came to play.
What immortal eyes or ears
could frame thy awesome inventory?

Places like Tech Hifi in MA were where the Audiophile hook was set deep in the children of the Greatest Generation in the 60’s and 70’s.

bierfeldt
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Port placement

As someone who has designed multiple speakers, ports are just one element of a very complex system. Everyone makes different choices around placement based on the cabinet size, drivers chosen and what they want to accomplish.

Secondarily, room placement is enormously important and you can make generalization about porting but there is no absolute. Every speaker behaves differently. At the moment, I have four speakers here from different companies. One is rear ported, one is bottom ported, one has dual side ports and another is front ported. They range in price between ~$6k and $18k at retail.

The hardest speaker to place and the one that needs most room from the front wall is the front ported speaker. I can show you rear ported speakers designed for near wall placement. Sealed speakers that need at least 5’ of space from the front wall for the image to come together. Speakers with side firing woofers and ports that are fine in a corner and other that need 5’ of space.

Every speaker needs to be looked at individually and there is certainly no wrong approach unless of course the speaker is poorly designed.

Stereophile rules require me to disclose that I am the owner of Verdant Audio Inc, a manufacturer or speakers, importer of equipment and retailer of lots of products in every post.

Kal Rubinson
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bierfeldt wrote:
bierfeldt wrote:

As someone who has designed multiple speakers, ports are just one element of a very complex system. Everyone makes different choices around placement based on the cabinet size, drivers chosen and what they want to accomplish.

................................................

Every speaker needs to be looked at individually and there is certainly no wrong approach unless of course the speaker is poorly designed.

Amen!

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