HIVI M3N - Noob question.

[mrsbadcrumble]

Hi All,

Is it me? I’ve found two different sets of T/S parameters for the same driver!
Not only that but they are both on the official swan driver website!

Overview M3N Full-Frequency_HiVi, Inc.
and
Overview of M3N Drivers_HiVi,Inc

I am a complete noob to speaker DIY and was hoping to use these in a John Krutke design as a starting point. After using the first set T/S parameters above, as listed on the Audio Europe website (where I got’em) in a couple of free speaker box design software packages (unibox, WinSID, etc,etc) and getting completely different recommendations/designs I thought I should get my head around what I am doing. The parameters didn’t appear to be complete so I thought I would check information from the official website and found two different sets!

My questions are:-
1. How critical are the T/S parameters? ( I realise actual measured parameters would be best but I am a noob)
2. Will the differences listed really make a difference to the final design/results?
3. Do different software packages always give such variation in suggested volume/design of enclosure?

Any help from this forum would be greatly appreciated.

Jeff

[digits]

Rob elliot has very comprehensive instructions on his website, for measuring many parameters manualy uesing a PC and a multimeter if must.

[blakkshepeaudio]

Strongly advise you to get a couple and measure them yourself. My recent experience (with B3N's) suggests that the factory T/S parameters bear little relationship to reality....

[bjorno]

Hi,

FYI: My :

b

[mrsbadcrumble]

Hi Bjorno,
Wow what a comprehensive response!!
Thank you for your time on this subject. You've put a lot of data into that post, I am going to need some time to understand what it's telling me. Can I just clarify what you've given me?

You've taken the two sets of T/S parameters from the swan driver website (given above) and extrapolated them to compare with the figures given by John Krutke for the B3S. Is that right?

Excuse my noob question but I can see you have started one calculation stream where Bl = 3 and the second stream where the Vad = 1.5 litre for each of the given T/S parameters. Why

I think Blakkshepeaudio is right. I guess I need to do some basic measurement of these drivers. I've made myself a nifty little microphone amp/wand arrangement as per various posts on this fine forum so I guess I can do the basics armed only with a PC.

Best regards
Jeff

[blakkshepeaudio]

Jeff,

My B3N T/S were much closer to Zaph's for the B3S than they were to the 'official' data. Very little change occurred after 100 odd hours of run-in.
These drivers, although I love them, don't model anything like the spec sheet says.

It really is a good policy to try and get trustworthy numbers before committing saw to wood. If you get the gear and the skills they will stand you in good stead for all your future DIY speakers !

[bjorno]

Originally Posted by mrsbadcrumble

..You've taken the two sets of T/S parameters from the swan driver website (given above) and extrapolated them to compare with the figures given by John Krutke for the B3S. Is that right?

Hi Jeff,

Yes, I used the same box volume of 3.35L..as for the B3S suggestion.

Excuse my noob question but I can see you have started one calculation stream where Bl = 3 and the second stream where the Vad = 1.5 litre for each of the given T/S parameters. Why

I consistency checked the the two given sets of T/S in two rows and calculated the impact on the resulting slightly varying closed box parameters.

First I checked if if the given BL factor returned a Vas value that was consistent with the other data then further down I did the same for the given Vas value.

Cross-calculating will show if the data is consistent and not been rounded off to be useless.

If the given BL and Vas values are correctly rounded off all the other data should be very similar to each other and not vary too much.

By the way..
I think both sets of data are in order,It seem that HiVi is distributing different but valid T/S to different retailers.

I think Blakkshepeaudio is right. I guess I need to do some basic measurement of these drivers. I've made myself a nifty little microphone amp/wand arrangement as per various posts on this fine forum so I guess I can do the basics armed only with a PC.

There still might be large variations if random drivers are tested separately:

Yes, I too think Blakkshepeaudio is right.

I believe the best HiVI BN3:s are cherry-picked from the factory batches and saved for speaker manufactures that demands a more precise tolerance of the T/S, the remaining BN3:s having a larger parameter spread after factory QC is shipped to retailers that only sells drivers directed to occasional DIY buyers...

Pity, this degeneration of advertised claimed driver T/S is more common than one think it would be in the reality.

The DIY'er must rely on his own measurements, if not, a possible upcoming speaker performance disaster might be the only result despite all good intension's.

Because of Zaph's chosen Vb for the B3S or the B3N to be more than two times the Vas value for both of the drivers, the drivers operates in a near boxed IB condition where the power handling is secured by using the capacitor assisted concept:

This would only result in minor FR differences regardless if the BS3 or the B3N is the preferred driver


b

[chris661]

Hi,

I think that quite a large range of small wide-band drivers will all end up in a similar box in the end...
Smallish ported box tuned around 80Hz. Sub to take over from there. Add some stuffing, play around with port tuning a bit and you're good to go.

Anything more complex (in cabinet terms) than that, I'd consider measuring the parameters. If it's a small, nearfield listening situation, I wouldn't worry too much, just be prepared to experiment a little.

Chris

[blakkshepeaudio]

Chris is right - the T/S parameter variations are not really a huge problem in practice. There are only so many types of enclosure to put drivers like this into, and they work pretty much as well with the actual parameters as they would with the factory ones.

I like to design and model as accurately as I can, and build designs that are reasonably tolerant of driver variation, so I like to have a good handle on what parameters I am working with.

In the case of the B3N, it wouldn't matter much in a small sealed box and a vanilla reflex box is also easy to design for either set of parameters. The only 'complaint' I have is that the wildly optimistic 80Hz fs claim leads one to expect substantially more bottom end capability than is actually on offer......

Anyway, they sound great and are a bargain so go for it!

Cheers,
blakkshepeaudio

[bjorno]

FYI

b