Small Sized Enclosure Design

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Hi,


Although I have been following this forum for some thime this is my first post.

I have been working on a small enclosure project for my notebook. I am planning to edit my videos and sound therefore I need better speakers then supplied with my toshiba.

I have been doing some search and here are the alternatives that I've found :

1- Brandor 50ASW/4 (aluminium cone) Requires 4.4 lt for f3=44 hz @ 82 db.
2- Seas W12CY001 (magnesium cone) matched with T25CF002 (Hexadym magnet system) Requires 3.4 lt for f3=60 @ 82 db
3- Accuton C89-T6 (ceramic cone) matched with C23-6 (ceramic cone) Requires 5.7 lt for f3=70 hz @ 86 db

I know that seas drivers have a peak near 5 kz, accutons look more dynamic and brandors have a smooth frequency response and they need considerably less volume but I don't have any idea about their sonic characteristics.

The design will be active and every speaker will be driven with a Class A SS amplifier and I am planning to build an active cross-over if the desing becomes 2-way.

I am planning to have a dynamic sound over a wide frequency range with low distorsion. Can you please help me to make a choice ?

Thank you in advance

Onur
 
Hi Onur.

I'm guessing that you mean Bandor rather than Brandor.

I have had extensive experience of the Bandor 50mm units - check my web site. The Fs is 65Hz and efficiency is about 85dB. However, one 4 or 8 ohm driver would work happily in a cabinet between 0.75 litres and 2.0 litres internal. A class 'A' SS amp would do fine if it's good and the units can handle 35 W RMS full-range.

The distortion is low and these babies are faster than electrostatics. I have no hesitation in recommending them. You would have to telephone Doreen Bance Jordan (+44 1 494 714058) and pay £70 (UK) /unit plus shipping. If you tell Doreen that I have recommended the units to you, she will supply.

I'm afraid that I haven't had experience of the Seas or Accutron drivers so I couldn't comment.

Please come back if you want any more information.

Steve
 
I have asked the same question in Diy Speakers mailing list and some members recommended your speakers. Additional to this, I have performed some simulations with the data of Bandors published on the official web page and the results look promising.

It is a privilege to find someone who has built an enclosure with the drive unit that you are going to build a design with so I will be glad if you could possibly answer my one or two questions.

Some people say that the real T/S parameters of Bandors miss the factory specs by a mile, have you experienced a similar problem? And if you have performed your own tests, could you please share them with me ? Since I don't have comments on other drivers I need T/S parameters for a healthy comparison.

I have built TL enclosures for AER MKIs and Lowther C45s, from those experiences I know that when a full-range unit casues a problem in the balance of the sound, it becomes very hard to deal with that problem. The other thing makes me unconfortable with full-range units is this, if I prefer to build a 2-way system and if I have a problem with the balance, I just lower the gain of high frequency unit and it is solved. I have doubts about getting the sufficient low frequency response to balance high frequencies in such a small bass-reflex volume?

Looking forward to your comments and suggestions.

Onur
 
Onur said:
Some people say that the real T/S parameters of Bandors miss the factory specs by a mile, have you experienced a similar problem? And if you have performed your own tests, could you please share them with me ? Since I don't have comments on other drivers I need T/S parameters for a healthy comparison.
I have found the Bandor units to be consistent with their specs. I don't yet have measurements with my new speakers as I've had trouble with my sound card and trying to install an operating system that can run the new card that I've bought. The other measurements that I have date back to 1990 and the drivers have improved a lot since then.

I have built TL enclosures for AER MKIs and Lowther C45s, from those experiences I know that when a full-range unit casues a problem in the balance of the sound, it becomes very hard to deal with that problem. The other thing makes me unconfortable with full-range units is this, if I prefer to build a 2-way system and if I have a problem with the balance, I just lower the gain of high frequency unit and it is solved. I have doubts about getting the sufficient low frequency response to balance high frequencies in such a small bass-reflex volume?

I have used the drivers in transmission lines and sealed boxes but not in bass-reflex cabinets. There's no reason why you shouldn't use a ported design but you would have more flexibility in a sealed box as you could vary the volume between 0.75 litres and 2.0 litres and still make music. Don't worry about the balance in the range of 100Hz to 20kHz - the drivers are pretty flat. The gains that you will make in integration and coherance throughout the range are very considerable compared to adding a separate tweeter. I'm absolutely sure that this is true but, in an emergency, you could still add separate tweeters. Don't buy them in advance though because, after you've listened to the Bandors playing full-range, you won't want the tweeters.

If you're just using one unit per side, you would want a subwoofer for frequencies under 100Hz. I would put a fourth order filter on the sub but you can use a first or second order for the full-range speakers. You could even run them without a filter.

Sorry I don't have my measurements yet but I hope that this is helpful.

Steve
 
It is getting more and more confusing !

It is sad that I can not comprare the measurements, but, if you say that I am going to need a sub for the frequencies below 100 Hz with Bandors, I am afraid it is not something that I would like to carry. On the other hand I think that you are talking about building a sealed enclosure and a sub. Although I don't know the Xmax limit of Bandor I suspect that it can exceed the limits of linear excursion and the group delay may show a bad character below 80 hz. Can this be true?

The driver units I have considered before reducing my list to 3 were :

Morel WM 113
EJ Jordan Jx53
Tangband W3-871S
Fostex FE87
Technics 7F10
Foster FF-7EG
Aurasound

As I am told Tangbands can handle more power then Seas drivers and they also do have low distorsion levels, but sonically Seas drivers were better in return of a more accurate engineering. The main reason why I left Tandbands was not their sonic character which is rather subjective but their high Qts and fs values. I am trying to build the smallest enclosure possible and at this point Bandor, Seas, Accuton look like to be a better alternative. Having said this, if you say that "with a little more volume you can get a better result with Tangbands", then I have to add them to my list again :)
 
Re: It is getting more and more confusing !

Hi Onur

Yes, I'm talking about sealed enclosures + sub. You would be asking a lot of two single 2" drivers to be able to provide a 'heavy bass slam' although they can do remarkably well when placed next to a wall.

The drivers will take 35W and will not exceed their excursion limits with 35W RMS, even in a 2 litre cabinet (the largest mentioned). You will get SPLs of 100dB at one metre.

I don't quite understand your comment about 'group delay' under 80Hz. We had a single unit system in sealed boxes on demo at the Frankfurt show with Seventh Veil subwoofers and they sounded very good indeed. I don't think the Tangbands are in the same league.

However, I'm not a salesman for Bandor. I just use their units. You will go with your gut feelings. The quality of a Bandor system may be higher than you really need for a computer system and the price higher too. If you're using Bandors you will also need a very quality source which your computer system may not provide.

Good luck whichever way you go.
Steve
 
diyAudio Moderator Emeritus
Joined 2001
Onur:

I guess the question now is: how low were you planning on going? Do you have an idea how many decibels you plan to play these at?

If you are planning to power these from your notebook computer-how many watts is that?

Remember that your hearing drops off sharply under 150 Hz or so. Also remember that these small speakers will not play much under 200 Hz unless they are placed against a wall. I can assure you, it is not just a case of putting two little speakers on a desk in the middle of a room, and if their F3 is 50 Hz, they will play down to there. If they are not placed much closer to a wall than they are to your ears, you won't hear anything near 100 Hz, let alone 50 Hz.

I am not trying to put you away from your project, I am just trying to let you know the physics of the thing. Little speakers need walls nearby to reinforce the bass. Put a little speaker in the middle of a room, and you lose the bass and midbass.
 
not in the same league?

Has anyone posted a comparison between the TB 871s, Jordans, and the Bandors from actual listening experience?

The FR seem pretty similar.

Onur- The greatest benefit of using a sub is that the full ranger is freed from having to deal with these frequencies, thus producing less distortion. The "bass slam" is the bonus.

Steve- Wanna trade some drivers for testing purposes? I owe you, so I'll pay the shipping.:)
 
Re: not in the same league?

x. onasis said:
The greatest benefit of using a sub is that the full ranger is freed from having to deal with these frequencies, thus producing less distortion. The "bass slam" is the bonus.
I really believed this too. I've been using an AR EC-21 tube crossover which has an active filter for the low-pass section and a passive line-level filter for the high-pass. I thought that the passive line-level filter would be pretty non-invasive.

In practice, I use the low-pass section for the Little Awesome subwoofers but I've taken to driving my Nonsuch 4 full-rangers directly (preamp to power amp to speakers) with no filter in at all. It sounds a little clearer that way.

Can you figure it? I believe that the EC-21 is working ok.

Steve- Wanna trade some drivers for testing purposes? I owe you, so I'll pay the shipping
X-Onassis, It would be a great idea but I don't have any spare Bandors to the latest specification at this time. I buy the drivers mounted on a front plate that has four holes so they come four at a time. I very rarely buy single drivers. It's a pity. I'd like to make the comparison. I've heard the units but never in the same system in the same room. Maybe it's one for the near future.

Can you still get the little Jordan 2"? If so, do you know its current Fs and at what frequency Ted recommends you cut it off?

Steve
PS: Why do you owe me?
 
Hi kelticwizard,


You have pointed out the very point that is important to me most.

I am planning to build an active speaker with Class A SS amplifiers using Full-Range drivers. If the design becomes 2-way, I will then double the Class A SS amplifiers with an addition of an active cross-over. And I can paly with the irregularities in the FR of the driver units like Seas drivers' 5Khz peak.

I am trying to go as low as I can without using a sub! This is the prima of my design.

My source is an Echo Digital Audio Indigo (Stereo 24/96 PCMCIA) sound card.

The Accutons' fs is 33.5 Hz but when you simulate it with BassBox 5.1 it can go no lower then 74 Hz in a 5.3 lt bass-reflex enclosure tuned to 45 Hz. When you simulate Bandors they can reach to 44 Hz in a bass-reflex enclosure, but the question is, the fb is lower then their Fs (fb=46 hz). I don't know for sure but I think I am not supposed to tune the box to a lower frequency then the drivers Fs? Can you please comment on this?

As for the loudness, I want them to have high sensitivity because I want them to cope with the attacks, they are not going to be played at higher volumes anyway. 86-90 db ! Seas units, TangBands and Bandors fail to catch Accutons' performance at this level.

Placement will be at the corners because in my office my desk is close to the walls and there are no other alternative and yes I am aware of the Phon curves. I am planning to compensate it within the amplifier on the other hand, that is also why I am tring to listen them above 85 db.

Thank you for your comments so that I can be able to express the problem more easily.

Onur
 
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