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To port or not to port

Hiya,

I have a dedicated 2 channel music only set up. (no HT) and currently have a pair of PSB Synchrony One B bookshelfs. I really like the speakers but sometimes percussive bass gets boomy and bass guitar has a resonant, for lack of a better term, droning quality to it. I feel the rear ports are the culprit. I've moved the speakers away from the wall in increments but it still remains. I've used every bass management crossover option on my pre-amp to no avail. PSB does not recommend stuffing the ports.

I'm thinking of going with a sealed design since I have a Rythmik sub to handle the low frequencies and a Parasound A21 amp to handle the lower sensitivity of a sealed box.

In the $2-3000 dollar range I've only come across 2 models.
The Vapor Audio Sundog and two from ATC, the SCM11 and SCM 19.

Would a sealed box "tighten things up" in the low end? And does anyone know of any other manufacturers making a sealed bookshelf?

Thanks.
mjm1124
14 responses Add your response
lowrider57's avatar
lowrider57
5,417 posts
 
I have used your PSBs, so first a couple of questions; what kind of stands
are you using and how far from the wall are the spkrs?
If you're not using isolation on the stands, the floor could be adding
resonance to the bass. The floor could cause loss of detail in the bass just
as much as the walls could. Also, PSB Synchs like to be 2-3 Ft. away from
the wall.
And most importantly, are you using any room treatments for absorption,
such as bass traps in the corner and behind the spkrs?
And yes, stuffing the ports will just take the life out of the spkr.
mjm1124 OP
25 posts
 
Lowrider,

Thanks for your response. I'm not using any room treatments, that would be a last resort. The speakers are about 3 feet from the wall and they're sitting on 23 inch custom made oak stands which aren't detached from the carpet with spikes but the speakers are detached from the stands with Mapleshade brass footers. Maybe I should try sand filled metal stands?
lowrider57's avatar
lowrider57
5,417 posts
 
The brass footers are fine, but you need to get the wood stands off the floor with some kind of footer that would dig into the carpet. I think the result would be a tighter bass. If you change to loaded metal stands, you would definitely need to spike them and they would be very effective for isolation.

Once again I'll mention how effective bass traps are, but I think the floor is your problem.
Post removed 
xti16
1,525 posts
 
If you think the port is a problem try stuffing it with dish cloths - socks - etc. If you so you will also want to cross the sub over a lot higher.

Just another thought.
ebm
9,311 posts
 
Not to port!!
don_c55
1,025 posts
 
Here is your answer!

http://www.stereophile.com/content/fifth-element-35-25-cheers-sealed-boxes
zd542
5,339 posts
 
"I really like the speakers but sometimes percussive bass gets boomy and bass guitar has a resonant, for lack of a better term, droning quality to it. I feel the rear ports are the culprit."

You may be right but there many things that can cause this type of problem. You may want to broaden your search and consider some other possibilities.
buconero117
2,311 posts
 
Depends, and yes it is complicated. Illustration, ProAc had one of their models, I forget exactly which one, that ported in the front. Ideal if you want to place them on a shelf. I have ProAc 140's, which are ported on the bottom. When I first got them, I installed two inch spikes to replace the small ones provide by ProAc, bass was okay. Next I put each speaker on a large, rolling plant stand, which added another two inches of height. I did this mainly to tune there placement and make them easy to move around the room. Base was significantly improved. So, I left them on the rolling plant stands. So, as all things in audio are, keep tweaking.
johnnyb53
3,510 posts
 
What? Not one mention of the amplifier involved or the crossover point to the sub, or the location of the sub?
tls49's avatar
tls49
1,351 posts
 

Agree with Lowrider57, stands need spikes at the floor.
ngjockey
1,042 posts
 
Too often I've seen commercial speakers using too small a box for the driver. Whether this is packaging or marketing, it leads to a peak in the bass. Are you actually using a high pass on the bookshelfs or just a low pass on the subs?

NHT makes sealed speakers.
lowrider57's avatar
lowrider57
5,417 posts
 
There are some good points raised; what is the output power of the amp into 4 ohms and have you listened to the PSBs with the sub removed? It would be interesting to know if the spkrs exhibit the same sonic problems in the bass.
mjm1124 OP
25 posts
 
Thanks for all your responses. After much fiddling I found that the sub was too close to the mains. After making some room and moving it to a corner I seem to have found the sweet spot.
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