Cost-no-object replacement drivers for Prism 6.6?

nathanm · « **on:** 6 Feb 2003, 04:36 am »

I just bought some used Norh 6.6s on Audiogon for $600. First of all let me say that these are the most beautiful cabinets that have ever graced my living room, bar none. Absolutely beautiful piano black finish. I couldn't be more happy with the looks and the design of the cabinet.

Now the sound on the other hand...what is the deal? Now I'm beginning to worry. I think an evil faerie has stolen the bass from every Norh speaker that comes into my apartment!!! This is the worst, most non-existent bass response I've ever heard from a cabinet this size. Absolutely weak weak weak!

Okay, so I got the 3.0s first, didn't expect bass and got mostly no bass, but more than I thought. Really liked the speakers. Then I got marble 7.0s. Expected bass, got a little bit more, but nothing special. Started to realize the cabinet really wasn't all that big and well gee, it's just a bookshelf after all. Still in love with the Prism cabinets mind you...then I see a used pair on Audiogon. I snatch them up as quick as I can. I figure this one's got more volume and two woofers instead of one. Well, first thing I had to open them up to remount the crossover which had fallen off in shipping. Wow, these are some cheeeeap lookin' drivers! Whew! Made from plastic wouldn't ya know? Oh well, I'll give them the benefit of the doubt. After I got the crossover fixed I listened to them. Where the hell is the bass? Even worst first impression than with the 7.0s when I had them 36" off the ground! They sound dramatically different than the 7.0s, for sure but what is most vexing is the absolute lack of anything resembling low end. My friend's tiny Polks which are less than half the size have prodigious amounts of low end. How can the Prisms sound so weak!? This can't be right! The woofers are wired correctly, they're in phase, I'm running them with LeAmps...but completely weak bass. Is my room the worst room in the world? Sucks up everything below 100Hz like a sponge? I don't see how a floorstanding speaker can perform so poorly!

The SE-9 makes no major difference either. And no, a subwoofer is not the answer. A speaker this size should NOT perform this anemic in the bottom. I'm not expecting pipe organ fundamentals here, nor booming hip hop beats. I would bet that anyone would find these weak-sounding regardless of the music you played. Even Fleetwood Mac's warm, enveloping bottom could not inspire the 6.6s. What the heck!? Even cramming them in the corner did nothing.

So my question is; how do I fix this? Let's say cost was no object, nor sufficient supplies, nor any of the things manufacturers have to take into account when designing a speaker. Let's say I want to replace the drivers in this gorgeous cabinet with something that is going to actually KICK MY ASS!? Something with BASS!!! I don't care what they cost, they just have to fit in the holes. I'll change the port if I have to, I'll put in a different crossover, I don't care! Help!!!

As it stands these speakers would be fine if all I ever listened to was acoustic guitar or flute!

I'm not trying to slam Norh, but I am definitely trying to slam myself!!!

Tyson · « **Reply #1 on:** 6 Feb 2003, 04:47 am »

Generally, efficiency and bass do not go hand in hand. Also, perhaps you have a suckout of bass in your room.

As for swapping out drivers, you could do it, but you'll basically have to buy a steep electronic crossover (of high quality), or re-work the crossover between the new woofer and the old tweeter. A RTA will also help to make sure that levels are matched.

As for port tuning, get the volume of the box from nOrh, the T/S parameters for your replacement woofers, and the unibox box modeling program. Plug in the diameter of your port and the T/S paramters for your woofer, and it will tell you how long your port needs to be for a given tuning.

Jay S · « **Reply #2 on:** 6 Feb 2003, 06:57 am »

Nathan,

I am sorry that you're not happy with the bass response of your speakers and that I can't offer any constructive help... but I have to agree with you that the finish of the speakers is stunning!!!

MaxCast · « **Reply #3 on:** 6 Feb 2003, 12:51 pm »

Nathanm, what is the size of your room. If I remember correctly you have a square room???? I would suggest getting a test disc with frequency sweeps and see exactly what you are getting. If your results are way off from mfgs. specs. then you have defective speakers or a f'ed up room.

Marbles · « **Reply #4 on:** 6 Feb 2003, 01:13 pm »

Make sure that you did in fact hook the XO up correctly.

What are you comparing these speakers to that have more bass?

I had a pair in my (large) bedroom and they had a lot of bass for classic rock etc... I don't listen to electronica.

If your comparing them to car audio thumpers, then your right.

Do you have a test tone CD, and a RS SPL meter? I would love to see what the FR response actually is at your listening position and at 1M.

nathanm · « **Reply #5 on:** 6 Feb 2003, 04:02 pm »

I definitely should get an SPL meter because I am interested myself to see what's going on.

Even if I did hook up the one crossover wrong it would be screwed up on only one side, but both sides sound balanced.

I'm comparing these speakers to all speakers I've ever heard that have better bass response than these regardless of size! I'm comparing them to my internal judge of proper frequency balance! I don't care what they cost, it's not even a factor. Just pure physics! Hell, I've heard desktop computer speakers that had more bass than these. I may not have the most tuned room in the world and surely there are issues with the flatness of the lowest frequencies, however there's no way in hell these speakers are doing what I wanna hear. You can kneel down in front of them and know without a doubt they are not delivering the goods. It's very obvious. The drivers are crap and\or the crossover is crap, I can't think of any other explanation. There's twice the radiating surface of the 7.0s drivers, there's more cabinet volume, why should there not be more punch? It makes no sense to me. The size can't be the limiting factor, they make subwoofers with smaller cabinets than these!

I could take these speakers to any electronics store, set them next to the cheapo line of whatever mass brand they have on display, put a $900 price tag on them and I would be shocked and amazed if the store sold a single pair. The cabinet is worth the money, don't get me wrong! The cabinet eclipses anything you'll find at Circuit City, American, Best Buy or whatever. Easily. But these drivers strike me as extremely poor performance. I couldn't care less about efficiency at this point, I just wanna know what I could replace these low rent Vifas with.

Marbles · « **Reply #6 on:** 6 Feb 2003, 04:09 pm »

Something is definately wrong somewhere.

The RS SPL analog meter is under $40. The Stereophile test CD is about $10.

Both are definate musts.

I would love to see the FR of these speakers.

Is the port (on bottom) plugged in any way?

My 5.2's were plugged with foam when I first got them.

PJ · « **Reply #7 on:** 8 Feb 2003, 10:14 am »

If you miswire one of the crossovers, your speakers will be out of phase. If you miswire both of them, they wont be.

Try unplugging one speaker all together (ie just play one at a time), and see if the bass improves.

I am not sure how the speakers are wired internally, but make sure you have hooked the two woofers in each cabinet the wrong way around. ie, all 4 woofers are in phase.

mbarnes · « **Reply #8 on:** 8 Feb 2003, 02:41 pm »

I have a pair 6.6s in my bedroom. We have sold quite a few pair--particularly in Japan.

As for the drivers, these are made by Vifa. While you might think that the molded chasis is cheap. Actually, stamped steel is much cheaper. Vifa calls this a molded polymere chasis. These drivers are actually qutie popular. They are the bigger version of the drivers we use in the 4.0s and 5.1s.

The -3 dB point is 48 Hz. This is respectable but not wall shaking.

As for what is going on in your particular situation, I would guess you might have standing waves that are canceling out bass. The reason I suggest this might be the case is you didn't have a problem with the 3.0s.

We have had many customers who like the 3.0s very much because they work very well in rooms where other speakers don't work so well.

Bass notes are very long. In a smaller room or with the right reflections, the wave folds ance cancels itself out.

An equalizer can help fix this problem by you need to be able to take some measurements. Bass traps can also work. Sometimes, just moving the cabinets around will work.

The nOrh 7.0s can have good impact and slam with the right equipment. I use a pair of 7.0 marbles in my upstairs system. This is probably the sysetm I use the most as it doesn't bother anyone else.

My main speakers are the 9.0s.

Curt uses a pair of 6.6s and he said a friend of his really liked them very much. I heard the 6.6s with Curt's new preamp and Le Amps and the sound was really amazing.

The drivers are not cheap. They go for about $20.00 each. We choose this driver because it is very efficient. We have recently sold a lot of SM 6.1s that use one of these drivers. The comments have been very favorable.

As an experiment, try them in another room--like the bedroom. Power them with something cheap--like an old receiver. I think you will find they do a very nice job. They should sound very good with the SE 9s. Pan has a pair of 6.6s in her bedroom and she uses and SE 9 amp.

nathanm · « **Reply #9 on:** 9 Feb 2003, 02:55 am »

I've got an SPL meter on order and I will post what I find out. I am going to measure the Prisms against the 7.0s, against the 3.0s, against my friend's Polks and against my Mackies; any speaker I can find. I have all three Stereophile test CDs and I might be able to get a function generator from my friend. But fundamentally, I really and truly think that the blame falls on nothing except the speakers themselves. All that room stuff is very important, I don't deny that. But to blame the room for an obvious lack of bass response is kinda like saying the Mona Lisa would not be a good painting if you hung it in dorm room.

How could standing waves be to blame if I still hear weak bass when my head is a foot away from the drivers, and why is there no air movement felt coming out of the ports? (they are not blocked, I checked)

Mr. Barnes, if you could put any drivers you wanted in these cabinets which would you choose? (For MUCH better bass response, that is) Would the VIFA XG18WH00-08 woofers be an improvement? What about the Scan Speak 18W8531G-00? As the title of this post says, the cost is not an object. I don't care if I have to put $1200 worth of drivers in this $600 cabinet, I just want some slamming low end that doesn't need the VMPS New Larger sub to make it worth listening to. Crossing the sub at 120Hz and goosing the level seems to do the trick. But that doesn't make it right. That says to me the mains are not holding up their end of the bargain. The kick drums sound like they have been phoned in. It's incredibly thin even at high volumes.

If I didn't love these cabinets so much I would not be so upset, I'd just try to sell them and be done with it. I think such a gorgeous design deserves to sound much better, that's all.

nathanm · « **Reply #10 on:** 9 Feb 2003, 03:04 am »

Quote from: Tyson

As for swapping out drivers, you could do it, but you'll basically have to buy a steep electronic crossover (of high quality), or re-work the crossover between the new woofer and the old tweeter. A RTA will also help to make sure that levels are matched.

As for port tuning, get the volume of the box from nOrh, the T/S parameters for your replacement woofers, and the unibox box modeling program. Plug in the diameter of your port and the T/S paramters for your woofer, and it will tell you how long your port needs to be for a given tuning.

I should mention that I would plan on replacing the tweeter as well. At this point I couldn't care much about efficiency. So far my experience with high efficiency speakers is that they do an excellent job playing hum and noise from the rest of the chain! Heh!

I did find that Excel spreadsheet (quite a monster!) and messed around with it for a while. The parameters are so mind boggling to me. Sometimes the T\S specs list the required parameter but not others. Half the time I get stopped short because what the calculator is asking for the specs don't provide. It's only a matter of time before I become catatonic staring at it all. I have a deep respect for anyone who knows what any of this shit means!

wunderlast · « **Reply #11 on:** 9 Feb 2003, 04:11 am »

I noticed the same thing that high efficiency speakers play hum and noise better. But I fixed my system and cured the hum and noise. It sounds much better now.

nathanm · « **Reply #12 on:** 9 Feb 2003, 07:26 am »

What did you do to fix it? I've just noticed that my tube amps hum quite a bit. Doubtful that there's much to be done about that. But to be fair it isn't objectionable at a few feet away on the 6.6s. My Fostex FE206RE drivers on the other hand...yeeowza! Those are really noise enhancers! Whew!

I tried putting the 6.6s in another room. The bass was a indeed bit better, but still not quite what I'm looking for. The 7.0s in the same room seemed worse though, even weaker than usual. Weird. I wish like hell I could just knock down the wall separating my bedrooms. Give those bass waves less of an excuse to fold themselves.

I attempted to stick the tweeter from the 7.0s in there but the hole isn't quite large enough. Haven't tried the woofer yet. Those bolts on there have been to hell and back and soon I suspect they will be stripped. I do so dislike fine threads... *sigh*

Rocket · « **Reply #13 on:** 9 Feb 2003, 01:02 pm »

hello,

if you replace the drivers you will have to redesign the xover. this will cost a lot of money for this modification. a friend recently replaced his tweeter with a focal tdx120 tweeter and it sounded terrible, he had to put a resistor in the xover to pad the sound down.

may'be it would be better for you to replace the speaker with something that develops more bass for you or possibly a subwoofer. the speaker does look good tho.

anyway good luck.

regards

rod

jackman · « **Reply #14 on:** 9 Feb 2003, 04:13 pm »

Rod is correct, I would sell them and get another pair. Have you ever tried Dynaudio Response series? These speakers have great bass (especially the floor standing 72's, but the 52's and the older 50's also have great bass) and are very good sounding. They play rock, metal, jazz, heck, they play anything very good. They also have a great resale value and, if you can get a good pair used, you can usually sell them for what you paid. The Danes can take a beating and sound good doing it. If you are able to sell the nOrh's for around the price you paid, you can get a good pair of Dynaudio's that I'd be willing to bet would be more to your taste.

Jman

Tyson · « **Reply #15 on:** 9 Feb 2003, 07:28 pm »

Just get a sub, you're not going to be able to find a speaker for under $1k that gives you the type of bass that you want. With a good sub, you can adjust the level of bass to give you the type of impact you are looking for.

nathanm · « **Reply #16 on:** 9 Feb 2003, 08:19 pm »

Quote from: Tyson

Just get a sub, you're not going to be able to find a speaker for under $1k that gives you the type of bass that you want. With a good sub, you can adjust the level of bass to give you the type of impact you are looking for.

I do. I have a VMPS New Larger:

Quote from: nathanm

Crossing the sub at 120Hz and goosing the level seems to do the trick. But that doesn't make it right. That says to me the mains are not holding up their end of the bargain. The kick drums sound like they have been phoned in. It's incredibly thin even at high volumes.

Subs are supposed to fill in that very last octave. But instead they are prescibed to cure weak mains. That is what I don't want. I don't want to use a subwoofer as a band aid for poor performance mains. I don't like the acoustic separation of having the sub in the middle. I want a little bit more extension and a lot more amplitude in the bass that's all.

I understand where Rocket and Jackman are coming from, but damn - why is the advice always "Bah! Get rid of it and get something else!"?

I personally don't like rectangular speakers. The Prisms are about the closest thing to the design I have in my head. I don't intend to sell them - it will cost me more to sell them, taking a loss in the process and still more to buy and sell other brand speakers on a neverending wild goose chase.

So are you guys telling me that a 43-liter cabinet in this shape is a hopeless cause and that no matter what drivers I put in there it still isn't gonna make a difference!?

What other ingredients are there besides cabinet, drivers, port size and crossover? Why can't this cabinet be made to perform to my liking with different ingredients? I am not worried about the crossover, I'll use an active one. If subwoofers can be made to extend to 20Hz in tiny cubes then why should this cabinet not have the potential for bass? That's what I don't understand. To me that says that a different-sounding\performing driver might work better. My question is what kind of parameters should I look for?

tmd · « **Reply #17 on:** 9 Feb 2003, 08:44 pm »

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.

rosconey · « **Reply #18 on:** 9 Feb 2003, 08:58 pm »

why not give rick craig a call on the phone.its only a buck, pick his mind.
he might have an idea on different drivers.(bottom mount a dvc 8")
why is your sub crossed so high

i have large stand mounts 3.5ways that i cross at 90 with my vmps large sub and its pooyfect nyuk nyuk

i though bass became directional over 100.
shoot just bottom mount a 8" woofer and a side mount a passive radiator.

JohnR · « **Reply #19 on:** 9 Feb 2003, 09:20 pm »

Quote

Subs are supposed to fill in that very last octave. But instead they are prescibed to cure weak mains. That is what I don't want. I don't want to use a subwoofer as a band aid for poor performance mains. I don't like the acoustic separation of having the sub in the middle. I want a little bit more extension and a lot more amplitude in the bass that's all.

Simple answer: get a second sub!

Regarding weak mains... my impression is that, given your listening preferences, you won't be satisified with any mains using one or even two 6 1/2" drivers. There are physical limits to drivers. It sounds like you are using Unibox already; put in the parameters of some popular drivers and have a look at the excursion graphs.

JohnR