nht oem replacement drivers

[k mier]

Hello all, seems I have a problem with one of my NHT 2.5i's. After demo'ing a Yamaha, Dennon, Pioneer, I bought a Marantz. New reciever in the system = set everything from scratch. While setting levels with pink noise I noticed the left speaker had more treble energy than the other. I switched channels from the reciever, switched the speaker cables around and back, changed to different speaker cables, used a carver pre amp with acurus amp, even moved the furniture around, same results. I'm not sure if it could be the drivers or some part of the crossover. The area seems to be, as best as I can tell, right around the lower/mid treble, maybe even something amiss in the upper passband of the mid? I would guess this is why my center image made a shift next to the left speaker. I've Googled the net and so far have come up empty for replacement parts. Any ideas. While I've got it open, ideas on higher quality crossover parts/wire? If I stick with oem values will that be right?

[ThomasW]

Hard to say without measuring if it's the tweeter or something in the crossiver.

If the tweeters aren't soldered on swap them and see if the problem reverses. That will tell you if it's in the tweeter or the crossover

[Ten 99]

Did you move physically swap both speakers for one another? One other option, could your right ear be suffering some hearing damage that is just being amplified by your setup (environment) and making it more noticeable?

Sounds really strange. If it isn't your ears, then it seems like Thomas' idea is as good as it gets. Isolate the driver or the cross-over as the culprit!

[k mier]

No, I didn't switch the speakers, they have the angled front baffle and the eight inch woofer is mounted on the inside panel, and to boot, the dang things are kind of heavy. :roll: Maybe I can lure a buddy over this weekend to help. Believe it or not, I wondered on the ear thing. I listened with one ear at a time, same result. Leveled and realigned them. I have measurements on the floor, level, square to butt on the face, and a lazer pointer, together I usually get them close the first time. Same result. I am going to switch them though, just to be sure.
Thomas, if you only knew how many speakers I ruined with a screwdriver. :M No matter how hard I try,..I think it has a mind of its' own. Yes, I need to swap them around, but, before I get the screwdriver near them, I would like to find replacement parts. Just incase....

[k mier]

With the extra time off for the holidays I was finally able to tear into my NHT's. Here is what I found. Tweeter made by Seas, 25TAF/D-NHT, H 858, 6 ohm. 6 1/2 mid, Peerless, cat. no 830301, 8ohm, (1-11-046-1 internal tracking number?) 8 woofer, Peerless, cat. no 830302, 8 ohm, (1-11-047-1) The 6 1/2 looks a lot like the csx line of drivers in the Parts Express cat. but I couldn't find the exact model number. Same goes for the 8 and tweeter. Looked through Madisound and came up with some that seemed real close, but not a complete match. The drivers that I did find were a lot cheaper than the ones advertised as replacements on another website.
Since the 2.5i's have an angled baffle, I resorted to swapping out the drivers one at a time. Sarting with the tweeter, no difference. Mid, no difference. 8, no difference. Center images are still drawn close to the left speaker. I then resorted to moving everything. I have a hump around 100hz I worked on also. After a week of dragging and tugging I wound up with a location out from the back wall 8 inches farther, closer to the side wall by 6 inches, with 4 bales of cellulose insulation in a diagonal pattern near each cornor and speaker. In some locations just the bales of insulation mada a 6db difference! Overall I wound up with better sound and imaging, but the center still pulls to the left. That leaves me with the crossover. Just how hard would it be to build a crossover with high quality parts? I don't have the smarts to design one. If it was just a simple parts swap, with better quality parts, I might be able to do that, but I wouldn't have a clue if I got on the wrong track. Is there some one or some where I can get a quality crossover built, or get the parts list and a how to put it all together paper.
Oh, I even switched speaker cables. Home made cat5, to some low priced Tara Labs, to Nordost Red Dawn. There was a difference in sound with each cable, but the center image remained leftish.

[Dennis H]

I think you're on the right track that it's the room-speaker interaction rather than anything wrong with your equipment. Have you tried absorbers at the reflection points on the side walls? Try pillows or sofa cushions or something like that to test it.

[k mier]

Weather permitting I will finish my short absorbers today. I will start with the same positions I have the bales of cellulose in now and go from there. I wanted to finish them before I started on the corner and sides.

I have wanted to upgrade the crossovers for some time. Is it possible to just use the originals as a template and start building new ones from scratch copying the values but with better quality parts? Or would this be more difficult than say starting with a newly designed one?

One more thing of note. Looks like the NHT's were not built as a pair. They have different dates stamped on the inside, same year, four months apart. Also, some one forgot to put gaskets on all the drivers on the left side. At the price I expected better quality control.

[ThomasW]

Designing a XO from scratch means making accurate frequency response measurements and impedance measurements of each driver operating in the baffle. I'd bet NHT did that when they designed the original XO's.

Then you must actually know how to properly design a new XO, starting with the measurements you made. The computer programs don't design the XO's for you. They just make it easier to design for those with the existing knowledge.

The safest thing to do is upgrade the existing components, but doing that doesn't guarantee better performance.

You can replace caps just use the same values.

Inductors pose a bit more of a problem. You'd need to measure the DCR of each one and make sure any new ones have the same resistance.

[k mier]

Agreed, Thomas. NHT knows more about making crossovers than I ever will. When time allows I would like to start at replacing the caps. I know NHT, like others, have a price point to consider when designing, even if the caps make a small improvement I think it would be worth it. Heck the cables I am using now cost about a grand for a small improvement. Improving some of the crossover parts and internal wiring would seem like a bargain.

Just a thought, but Behringer ultradrive digital crossover. I usually think less = more, would it add it's own signature with the extra conversion processes? Should it sound better than the passive crossover? Would it be flexible enough to do what I would need to do? comments???

[Dennis H]

Heck the cables I am using now cost about a grand for a small improvement.

No offense but YIKES! Spend some small fraction of a grand fixing your room for BIG HUGE GIGANTIC improvements. Get that image locked dead center. Then sweat the small stuff like caps and wires if you're still inclined.

[ThomasW]

You'd need to have the same measurement data to design a XO using the Behringer as would be needed to make a passive XO.

[k mier]

No offense but YIKES!

No offense taken. The bottom of the line Tara Labs sounds better than the home made cat5, the Nordost Red Dawn may not be a perfect match for my system, but it does sound better than the others. I work for a living so I kind of see it as the law of diminishing returns, I could not buy this cable new. From time to time the local dealer comes across a trade in. I go in just for a look around, wind up taking something home for a demo. Sadly, I have kept a lot of those...demos. :B
Working on the room. Finished two out of four small panels today. Two large ones for the cornors and two more for the sheet rock wall behind the speakers are next.

You'd need to have the same measurement data to design a XO using the Behringer as would be needed to make a passive XO.

Doh..
It still makes me wonder since they were manufactured over four months apart and the left speaker was missing all the gaskets that there might have been a variance in the production run or a quality issue.

[ThomasW]

The missing gaskets is an assembly issue, I doubt that there is a similar issue with the rest of the components. If there are air leaks that will certainly impact perfromance.

Most people's ears are not as closely matched as modern driver's tolerances. So in the unlikely situation that there was a running production change, that would be the only reason to suspect differing performance between the two speakers

[Dennis H]

Working on the room.

Since you're experiencing extreme lateral shifts, the most likely suspects are the side walls. As a guess, I'd say the side walls aren't symmetrical, e.g. speakers closer to one wall than the other or different materials on the two walls. Absorbers at the side-wall reflection points should help that. Front and back walls are less important.