Lack of bass in NHT 3.3.

I recently failed to sell my pair of NHT 3.3's to a local(Dallas/Ft. Worth) buyer who remembered selling them circa 2000 and feel mine are not putting out enough bass volume. As you may know they are noted for the bass from the 12" side firing woofers. I followed a suggestion and removed the jumpers and connected just the subwoofer input and was able to verify signal. Since these are perhaps subwoors rather than traditional drivers I am not certain how loud they are supposed to play. My two part question is are there any 3.3 owners in the area willing to let me visit to hear your speakers and has any 3.3 owners run into a similar issue. Many thanks, LS

NHT 3.3s are very position specific ... according to the manual  you must place the back of the speaker 3 inches from the back wall  so the speaker and the wall create a corner ... the corner gives you a 3db boost in the bass region and this has been compensated for and built into the crossover  

If you pull the 3.3s out into the room as you would a normal speaker ...  they lose the boost or gain in the bass region created by the speaker/wall creating a corner and can sound lean or thin 

Unless they are set up this way ... they will definitely sound bass shy and tipped up or a bit bright in the treble ... eliminating the jumpers or bi amp-ing them is totally unnecessary but they do need some watts due to their some what lower 87 to 89db efficiency ...  150 watts of good clean power is all you would need to make them sing  

Your listening position should be 1.25 to 1.5 times the distance between the speakers ... my 3.3s are 7 feet apart and I sit 9 feet off the front baffles ... at 50 to 75 watts on my amp's meters I get 92db at my seating position with peaks around 97db ... if I turn the amp up a bit so it pumps out 100 watts or so  on it's meter ... 102db on the peaks are easily produced at my listening positon 9 feet off the speakers front baffles .. no problem  

With 102db peaks  they don't sound loud ... strained or in your face  but very authoritative with real life size scale ... narrow front baffles has them image and disappear like the best mini monitors  

The 1259 NHT part number for the woofer is also used in their 12 inch stand alone subwoofer and some other subwoofers of that era .. so you shouldn't have a bass issue ... you just don't have them set up correctly or are not feeding them enough watts 

This is all clearly detailed in the owners manual about distance to the wall and spread to seating distance measurements ... I'm sure I have my owners manual somewhere ... if you can get me your mailing address I'll send you a copy 

Just get a piece of wood exactly 3 inches wide and place it against back wall and push the speaker up against the wood ... now you're 3 inches from the back wall

Enter your text ...
Thanks Dave but they are positioned correctly and have 300 watts from a Bryston 4bsst. I am not convinced the output is low, the would be buyer is. Just want to make sure before selling that the speakers are indeed functioning as designed. May have to find another local pair and see how much output they have, again it is not an issue of how low they play, they measure and sound well, just not putting out the volume that the buyer hoped for. Not sure if my speakers are defective or his memory/expectations but thanks for reminding all of the power needs and the placement requirements. LS
Use a test CD with a bass frequency sweep and measure with a smart phone SPL app.
Thanks onwhy. Have the omnimic and can measure SPL with that. To my ears they seem to perform like my other subwoofer, the lowest frequencies are audible but do not have a lot of SPL. And what should the proper spl be for a sub woofer? The other drivers are certainly playing with robust volume. Not sure i have a cd with bass sweep, although it may be on the omnimic test cd but still not sure what the proper spl should be. Thanks, LS
Set your volume so that a 1kHz tone reads at 75dB.  Then measure the readings for midrange thru bass tones without changing the volume control.  There will be peaks and valleys, but the bass level should be strong down to at least 30Hz.
Thanks again onwhy. The omnimic shows a nice flat frequency response down to 20 Hz. My question is more about the spl levels I should expect from this 12 inch sealed subwoofer, as I have stated it seems to be about the same as my Martin Logan Grotto subwoofer, nice low frequencies but not a lot of SPL.
Onwhy, sorry if I did not read your instructions carefully. When you say strong down to 30 Hz I am guessing that this frequency area should have the same db reading. Will check it out if I can find an appropriate cd with the requisite tones. Thanks, LS
Onwhy I have run the test to the best of my ability and with the following info. Found an old mmg test cd(ultimate test cd). It starts with a 0 db test tone at 1khz and then offers tones at -10db of 20,30,40,50,60,100,..... Hz. The room the speakers are in, which does not offer optimal placement, though when they were auditioned at the buyers home they did have optimal placement, currently has a non weighted ambient noise level of  about 70 db. Ran the test tone at about 100 db and then ran the first few low tones. The Spl levels were pretty negligible till it got to 50 Hz. If the tests were done properly and if this result is not what the speakers were designed to produce, discounting the room and gear they are currently hooked up to, since there is no evidence of damage externally to the cones and since I have been told that crossovers should not be a problem, since both would have to fail and that the signal flows thru chokes which are not likely to fail. What other possibilities are there. I am guessing if they were both damaged i would hear some distortion and not merely a lack of volume. Sure hope there is an Agon member that currently has a pair that can weigh in. Thanks for your input, LS
For grins I ran the same test in my listening room which seems to have the same level of ambient noise and got slightly superior results. About what I expected, my martin logan sub is putting out a little bit more spl than the built in nht subs. Are the nhts defective for putting out low spls and if so what is the cause. If they are running as designed , then do I conclude the would be buyers 17 year old memory is defective. Any current 3.3 pwners out there that can weigh in? Thanks, LS