[JohnR]

Having said that, I have another suggestion. Since you're planning to use an active crossover anyway, leave the drivers in the cabinets and set yourself up with the crossover and four amps using those drivers. Then add baffle-step compensation to fill out the bottom end, it's a simple shelving filter centered at I would guess around 300 Hz. Or just use an eq to get flat response. That might provide you with subjectively better balance, although it won't play any louder. Then you could decide whether you wanted to spend the $$ on different drivers. The parameter you're most likely looking for is a good Xmax. Off the top of my head the Scanspeak 8545 is one such driver.

[nathanm]

why is your sub crossed so high

I can cross it anywhere from 44Hz and up if I want to, I chose 120 cause they needed more help in the living room.  I usually have it at 60Hz.  It depends, I'm always tweaking it based on the music.

Would any of the VMPS bass drivers fit into the cabinets? I have no idea if the calculations work for the size of the cabinet but can't you play around with stuffing to 'alter' the cabinet volume? I would say the drivers in my 626's hammer out some serious bass.

There isn't much stuffing in the cabinets.  There's half inch thick polyfill type padding on the walls.  I would think that adding more would result in less bass overall. If the bass was 'boomy' or 'flabby' that might work, but the opposite problem is occuring.  I just went and looked up the 626 on the website.  If those little things can "hammer out some serious bass" then I assume I am not crazy for expecting more umph from a relatively small cabinet volume!  Heh! The VMPS woofers certainly would be a visual compliment I think.

Thanks JohnR, good ideas. The Scan Speak 8545s are what's in my marble 7.0s.  I think I might have to cut the hole in order to fit those in.  I know the 9700 tweeter doesn't fit at least.  Hmmm.  Worth a try though.  The 7.0s are in the same room right now right next to the Prisms and they have even less bass response, although I think the overall sound quality of those is superior to the Prisms, which aren't as clean and open sounding.  

Lots 'o work to do...

[markC]

I'm still stuck on the comment that you made about ..nothing comming out of the port. In a bass reflex design driven to moderate  to high levels, there most certainly should be some "good wind" happening. For example, a b.r speak driven to 2/3 to 3/4 it's capable spl, (max volume),  should easily blow out a bic lighter from 3"-4" from the port opening. Not that I know what I'm doing, but I built a pair of speaks over the holidays and the model program spit out an F3 of 47 hz. They have taken their place in my second system, and I am quite pleased with the results. An F3 of 47 hz will not rumble your liver, but it does get your attention in the "feel the bass" area. When playing at moderate to high levels, can you see the drivers moving back and forth? It seems that something is not right.

[nathanm]

That's always been my experience - you could put your hand over the port and feel at least a little breeze coming out.  With these it's rather faint in comparison.  Maybe the bottom-firing nature of the port is working against itself?

*goes to check the visual excursion of the woofers*

I dunno folks, maybe I am just crabby...They are performing better in the spare room than they did in my living room.  Perhaps the only thing "wrong" with the Prisms are that Mr. Barnes and I don't have the same views about the voicing of a speaker.  I think that becomes clearer and clearer with every Norh product I buy.  Ha!  If I crank up the bass TONE CONTROL on my NAD 3225PE I can make air puff out of the port, but at flat it isn't quite so breezy.  (plus this doesn't really add any bass definition, it just sounds wooly and a bit obnoxious)  Maybe it's an XMAX thing?  Dunno...  I think these might benefit from some drivers with some more pumpin' action on the 'ol surrounds.  The cones move for sure, but not terribly much.

(off topic)
I tell ya, I wish Tang Band made bigger full range cones; those 'lil drivers on the 3.0s are so damn good!  The majority of the spectrum sounds so natural through them.  If they had more power handling and more extension on the top most and bottom most octaves they'd be awesome.  They just have a woody, natural tone to them.  If the sound of the 3.0s were put in guitar terms I'd say they sound like a great set of worn-in strings as opposed to brand new ones!  

What I thought would be cool would be a wooden 'subwoofer\bass bin' drum the size of the 7.0s or 9.0s with like a 10" or 12" woofer taking up the entire front baffle with a little platform on the top to place the 3.0s on.  That would rock I'd bet.  An array of Norh drums stacked on top of each other would be like a poor man's B&W Nautilus in a way. (You'd have to make the bass drum out of a giant redwood! Har!)

[markC]

Unfortunatley, adding more drivers driven by the same source will not increase the spl unless you have an unlimited supply power amp and you wire them in parrallel. I think

[MaxCast]

nathanm, have you tried other similar sized speaker/drivers in your rooms besides the 7 and 6.6?
What is the size of the rooms and what is the speaker placement in those rooms?
I think after you do a frequency sweep you will at least be able to rule out a couple culprits.

[mbarnes]

Unfortunatley, adding more drivers driven by the same source will not increase the spl unless you have an unlimited supply power amp and you wire them in parrallel. I think

I am trying to figure out why you wouldn't have bass. I own the 6.6 and listen to it every day. I have a Proton 60 wpc integrated hooked up. Rotel had the same unit with their logo on it.

The sound is very full and the bass is quite good.  As I said earlier, Pan has a pair of 6.6s with the SE 9s.  The sound is also quite good. We have sold many of these to Japan and the comments have been quite good.

I use this cabinet for testing. We have been looking for a perfect speaker. We thought of using the 18W/8531G00.  If you were to put two of these in the cabinet and tune for 30 hz, the -3 dB point will be 46 Hz.  

If you use the woofers we use in the 6.9s, then the -3db point will be 45 Hz.

The 18W-8545 drivers we use in the 7.0s would get down to 47 Hz.

When you use two drivers, you increase the efficiency you need more volume for the woofers.

I thought of another possible problem.  Is it possible one of the woofers is wired out of phase. If that is the case, you would have not bass what-so-ever.

[wunderlast]

In another thread expectations were mentioned. Could it be that he expects wall shaking bass at moderate volume level? Maybe has bad acoustics.

[nathanm]

I wish I could invite you all over to hear what I'm talking about.

Could it be that he expects wall shaking bass at moderate volume level? Maybe has bad acoustics.

Maybe he expects realistic bass at ANY volume level.  Why is it that when I say the bass is lacking people jump to the conclusion that I am looking to rattle the nails out of the walls playing gansta rap? Weak bass means weak bass, it doesn't mean "bummer, why can't I make the neighbor's dishes fall out of the cupboards!"

Maxcast: my living room dimensions are 14x12x7.6'  But those are not entirely accurate because there are three openings in the room that open into the kitchen and hallway, so add another 10 feet onto the width.  This is a problem in itself overall, but not so much that I think the room is doing the speakers a disservice.  The bedroom is a bit smaller and narrower. I'd have to measure it, but it's approximately 10x14x7.6'  I have concrete floors, so maybe that is weakening the sympathetic vibrations.

Well anyway, thanks for all the suggestions.  I will stick some different drivers in there and see what happens.  Perhaps the 6.9 cabinet would be better.  I'm still curious why the visually smaller 6.6 has 10 liters more volume than the 6.9.  Is the site info correct Mr. Barnes?

[mbarnes]

As I stated, I use the 6.6s in my bedroom. I could  use any of my speakers but these work very well for me. My amplifier isn't all that different than yours so I won't say it is electroncis. I have a Proton 60 watts per channel integrated.

My room is about 15 x 12.  In this room, I have a full sound with what I would say is respectable bass.  

I believe you said that the pair you have are used.  It is hard for me to come up with a specific problem.  Saying that there is no air coming through the port is confusing.  Did the previous owner remove the ports ports?  

I don't think changing out the drivers with another brand will give you bass.  Almost every computer model that I run with two 6 or 7 inch drivers in a 43 liter cabinet gives you about 45 to 48 Hz -3dB.  That isn't to say that these drivers all sound the same -- only that they would have the same amount of bass energy.

Xmax is most likely not an issue with a modest amplifier.  I seriously doubt you are driving the drivers beyond their phyical limits or into non linearity.

As I stated before, if any of the drivers are wired incorrectly or the wiring from the crossover is incorrect, the drivers might be out of phase witn one another. This would cancel out any bass response.

The cabinet for the 6.9s is about the same height as the 6.6 but more narrow.

One more consideration is that the 6.6s are 4 ohms.  Some amplifiers can not properly drive a 4 ohms speaker.

I wish I could invite you all over to hear what I'm talking about.

Could it be that he expects wall shaking bass at moderate volume level? Maybe has bad acoustics.

Maybe he expects realistic bass at ANY volume level.  Why is it that when I say the bass is lacking people jump to the conclusion that I am looking to rattle the nails out of the walls playing gansta rap? Weak bass means weak bass, it doesn't mean "bummer, why can't I make the neighbor's dishes fall out of the cupboards!"

Maxcast: my living room dimensions are 14x12x7.6'  But those are not entirely accurate because there are three openings in the room that open into the kitchen and hallway, so add another 10 feet onto the width.  This is a problem in itself overall, but not so much that I think the room is doing the speakers a disservice.  The bedroom is a bit smaller and narrower. I'd have to measure it, but it's approximately 10x14x7.6'  I have concrete floors, so maybe that is weakening the sympathetic vibrations.

Well anyway, thanks for all the suggestions.  I will stick some different drivers in there and see what happens.  Perhaps the 6.9 cabinet would be better.  I'm still curious why the visually smaller 6.6 has 10 liters more volume than the 6.9.  Is the site info correct Mr. Barnes?

[nathanm]

Well I got my Radio Shack SPL meter and here's what I measured.  This is a C-weighted measurement taken from my listening position.  I used the Stereophile Disc 1 warble tones tracks #20 through #31.  I set track 20 which is 1KHz to read 80db on my meter and went from there.  Red line is with the subwoofer on and the green line is just the Prisms by themselves.  SE-9 volume was cranked and level was made with volume control on the Shanling CD player.



I've since ordered a pair of parametric EQs to try to flatten this out.  Hmmm.  I think I will also make a test tone track in Sound Forge that has finer steps.

I wish the meter had more range.  I suppose the digital one might be better.

[Marbles]

The microphone on the RS isn't perfect, you need to use the following chart to correct for it.

10Hz add 20
12.5Hz add 16.5
16Hz add 11.5
20Hz add 7.5
25Hz add 5
31.5Hz add 3
40Hz add 2.5
50Hz add 1.5
63Hz add 1.5
80Hz add 1.5
100Hz add 2
125Hz add .5
160Hz add -.5
200Hz add -.5
250Hz add +.5
315Hz add -.5
400Hz add 0
500Hz add -.5
630Hz add 0
800Hz add 0
1kHz add 0
1.25kHz add 0
1.6kHz add -.5
2kHz add -1.5
2.5kHz add -1.5
3.15kHz add -1.5
4kHz add -2
5kHz add -2
6.3kHz add -2
8kHz add -2
10kHz add -1
12.5kHz add +.5
16kHz add 0
20kHz add +1

Two other things, one, you are giving us the readings at your listening position, room reflections included.  This may or may not be representitive of the speaker, just how it sounds at your listening position.

To appropriatley measure the speaker you should measure it from 1 meter.

If you have a camara tripod, this is better than hand held at either location.

It looks like you have a peak around 40hz which is reinforced for a bigger one around 80hz, this is most likely a room problem.

[nathanm]

Two other things, one, you are giving us the readings at your listening position, room reflections included. This may or may not be representitive of the speaker, just how it sounds at your listening position.

To appropriatley measure the speaker you should measure it from 1 meter.

Exactly!  What else matters?  This is a real world measurement.  Why wouldn't I measure it from where I am sitting?  It's a measurement of what these speakers sound like in my room.  Anything else is pretty meaningless to me.  If I had an anechoic chamber out back then hey I'd love to go in there and check it out, but I don't.  I only care about what I hear from where I'm gonna be sitting.  I don't think these are supposed to be nearfield speakers are they?

Plus, the disc indicates that the warble tone is supposed to negate room interactions. And erm, since I always listen to my speakers in this room I guess it's perfectly realistic to assume I am going to have to listen to room interactions no matter what.

I always though that chart was something a technician could plug into the thing electronically, but it's a do-it-by-hand thing, eh?  I will have to futz with that later.  Thanks!

[Marbles]

Just wanted to know what your objectives were....

If you wanted to measure the speaker, then it would tell you if new drivers might help....guess your not interested in that anymore...

Can't remember, did you try a SS amp to see if that would give better bass than the tube amp?

[nathanm]

Ahh, I see what you're saying.  Okay, so I did a quasi-anechoic-through-not-really measurement by piling most of my LENRD bass traps around a single Prism and measuring it from 1 meter in an otherwise mostly empty bedroom (except for a chair, a LeAmp and the CD player).  Scientific?  Nope. But as good as it gets for now.  Here's what I got:



The purple line represents my 1 meter fake-anechoic, just-one-speaker measurement.  To me it looks like the living room is boosting 160-80 but the speaker is still dropping off like a rock after that, with that little bump at 40Hz.  Now, granted this is not done in a room with a wire floor and 3 foot fiberglass wedges covering all the walls.  I wish I had a digital camera handy to illustrate this concoction.

Anyway aside from the test, I felt they sounded a bit worse with the LeAmps and the NAD I think.  But I would rather hear a LeAmp that hasn't been tinkered with.  Still, I don't believe an amp can account for the general  frequency balance of a speaker, especially its bass abilities.  To me it's that character is always self-evident the first listen.  Everything after that is micro adjustments.  That's been illustrated to me on a few occasions.  Cranking up the bass knob on the NAD just made them sound muddy.  No punch.  To me a 17 decibel drop from 80 to 50 hz just MIGHT explain some of that.

Still, I have grown to like them more, even though the bass is so reserved.  Placement has helped, but as I said, they are still very thin-sounding for a floorstander IMHO.  What I cannot grasp is how I've heard smaller speakers produce better bass than these.  That's why I'm so confused.

[nathanm]

Oh yeah, this plot is made without the corrections for the meter, but really, with only 1.5db deviations or less the curve wouldn't look too much different than it does now.

[Curt]

nathanm,

I believe I read in your old signature file that you had some "gain tweak" in your MB-100s.

Just wanted to let you know this does cut your bass response down a bit and also adds some lower bass distortion. It is not a huge difference  but, it is easily noticable.

The guys that were doing this only changed one resistor to bump the gain up but, it so happens that resistor and a capacitor, in that circuit, form a bass cutoff filter.

So, what they wound up doing was increasing the gain a little and also cutting back the bass as well.