Frequenty asked questions

© Copyright 2012 – Audiofriends – Fred Buist – All Right Reserved
(PS:  All items are to determine to copyright provided with an official date stamp.)
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Frequently Asked Questions

1. Why you should buy from Audiofriends.
2. Is it worth it to have my speakers repaired?
3. Does my speaker have other defects?
4. I prefer a rubber hanging surround rim.
5. Will I be able to perform the revision?
6. What do I have to pay attention to before buying surround rims?
7. What can I expect from the sound after the revision?
8. How can I test the repair?
9. How much time does a repair take?
10. How about the payment, delivery & cash on delivery?
11. Why does Audiofriends ship in boxes?
12. Does Audiofriends also refoam for others?
13. Running in your speakers
14. Should I only have one side of my speakers repaired?
15. The dust cap story.
16. Do you also have special sizes?
17. The surround rim sizes deviate.
18. Are the manuals from Audiofriends?
19. Which glue & brush?
20. Do you guarantee the repair?
21. Why do you ask for the dimensions of the speaker?
22. In which cases do I not have to measure my speakers?
23. Does Audiofriends also refoam for others?
24. Running in your speakers.

1a. Why you should buy from Audiofriends.
Audiofriends is a non-profit website, for and by hi-fi hobbyists.  We are not just any trading company that would sell underwear if we could make a profit, but an organisation with deep roots in the hi-fi world.
With this background, we always make all possible efforts to provide our customers with the right surround rims (surrounds).
We have a great variety of rubber / textile / foam surrounds for almost every type of speaker. We develop the surround rims in 3D and commission the production of our designs. With our product range, we sell to companies throughout the world.
Reasons to buy from Audiofriends?
  1. For specially sized speakers we have dozens of surrounds, especially produced with original dimensioning as well as various original surround rims. We also commission the manufacture of customised surrounds. This means that we can deliver surrounds that nobody else can supply!
  2. More than 150 different surround rims.
  3. Many manuals(free) on internet with numerous colour photos.
  4. Surround rims are indicated in 5 sizes so you can check for yourself whether or not they fit.
  5. Shipping in plastic + sturdy box, against deforming/damage (draught seal)
  6. Indication of pliability/flexibility/compliance if it differs from the standard pliability.
  7. Brush, 50 different dust caps, and excellent speaker glue available.
  8. Help desk (also by phone) of experts with more than 14 years of experience.

Therefore, we say:
Audiofriends: for The Best Quality!
See also

2. Is it worth it to have my speakers repaired?
Repairing a speaker with surround rims from Audiofriends is almost always viable. Having brands such as Tannoy, Kef, JBL, etc. revised is almost always a worthy investment. However, it is important to buy surround rims with the original fitting, which often are only available at Audiofriends.
There may be different reasons for repairing a speaker:
  • more quality for less money
  • especially for speakers of 15 years and older, but even for newer models: they will retain their value
  • if your speakers can retain their value, they are more easily interchangeable
  • if a certain model is out of production; ‘old love never dies’
  • a passion for old reliability
If you are not sure, you can ask us for an estimate. We have a lot of experience with loudspeakers. Personally, I have worked in specialist trade for years and we have almost all possible annual directories.
3. Does my speaker have other defects?
If you think your speaker has other defects as well, please contact us by
4. I prefer a rubber hanging surround rim; do you sell these as well?
We have rubber surround rims, but they are less in demand compared to foam surround rims. A hanging surround rim is an essential part of the speaker unit and it could sound completely different with a rubber surround rim instead of a foam (-rubber) surround rim. The advantage of rubber is that it does not decompose. This is partially true; however, rubber may dry out and/or harden. The foam rubber surround rims we offer are made of top-quality polyether and are extremely durable. The following text is a direct quote from the Dutch edition of the book ‘The Loudspeaker Design Cookbook‘ by Vance Dickason. This is not just any book, but a Bible among books used by designers of loudspeakers:
--- For this reason the surround is an essential part of the cone construction, and also a part that in an important way is reponsibleresponsible for the frequency- charateristicscharacteristics –-
5. Will I be able to carry out the revision?
Everybody should be able to revise a solid 8, 10 or 12 inch woofer. Some people can do a more precise job than others, but they should all pass the test with the test signals. We have exclusive manuals for virtually every problem.
The Bose 901/802 units are a bit more complicated, so we have prepared special manuals for these speakers. With a brochure, everyone should be able to do it. However, a bit of skill and patience will help make things easier.
6. What do I have to pay attention to before buying surround rims?
Audiofriends is precise with regard to dimensioning. Please note: Audiofriends will keep an eye on the things listed below. If you provide us with the dimensions or a well-known type of speaker, we will make sure you receive the correct surround rim.
The surround rims have to fit perfectly. If the cone is ‘hidden’ underneath the hanging surround rim too much, as is the case in Picture A, performance (the volume under certain circumstances) may be reduced. In a multi-way speaker system (a loudspeaker casing with, for instance, a high tone and a low tone loudspeaker), the balance between the speakers can get distorted.
Picture B indicates what could be considered correct.
Picture C is the ideal situation.
Picture D is also excellent.
Picture E is correct from a technical standpoint, but it looks clunky. Such a setup makes it difficult to work neatly and often involves a lot of messing around (see also below).
Picture F is the correct situation.

 You can purchase from elsewhere, but please take note of the dimensions.
7. What can I expect from the sound after the revision?
Please take into account that in the past 5 years, your speakers played with surround rims that were much more flexible than the original design. Additionally, the new surround rims need to be run in (see other frequently asked questions). Particularly in the beginning, your loudspeakers may sound different. After a run-in period of 3 months, the surround rims will have become more supple and produce a fuller sound. In the FAQs, you will find how you can run in your speakers.
8. How can I test the repair?
Feeling whether or not the speaker rasps is often insufficient (!):
  • When the unit is mounted in the casing, the weight of the cone pushes downwards slightly. If the tolerance is low,  the unit will still cause interference
  • In that case, simply push the cone down and it may cause interference in case of an outwards movement. See below: this speaker should pass this ‘test’.
It is also insufficient to check whether you hear a ‘rasping’ sound by means of test signals (see above).
What is the right way to do it, then?
Testsignals allow you to properly test the speakers. You can do so by means of separate units, connected to your amplifier or with the repaired speaker in the casing, once built in. With our unique repair method, you already know whether or not the speaker is properly centred. Only a local faulty glue-joint, for instance, could cause a problem. Be careful with test signals (!!). Do not turn up your volume if you do not hear anything! The test signals and this text are, of course, the property of Audiofriends. The following signals are ones that you can use (at your own risk):
Woofer (bass loudspeaker):
20-500 Hertz
20-2000 Hertz
Middle tone unit:
500-8000 Hertz
Test method:
  1. You burn the test signals to a CD. We assume it concerns a woofer in this case.
  2. For the woofer, you first use the 20 - 2000 Hertz (sweep). TE: do not turn up the volume of the amplifier too much, certainly not if you do not hear anything. If you do not hear anything, you first have to listen to the entire sweep, and only turn up the volume a bit afterwards. NOTE: do not turn up the volume of the sweep, if it decreases at a certain frequency. You may not hear the signals, but the speaker does feel them.
  3. Listen whether the sweep produces an even sound. If there is a parasitic tone at a certain frequency, it could be caused by a small problem. You hear a parasitic tone if something starts to co-vibrate at another frequency than the one you hear through the speakers. Note: I daresay that even many new speakers have parasitic sounds. If the volume is turned up, some cables or filters may start to vibrate, or the fast movement of air may cause some sounds in the bass reflex. Small parasitic tones, which cannot be heard in various types of music (even after being aware of them), are less important.
  4. Go ahead and try the 20-500 Hertz signal. Problems most often occur at this frequency. We also performed revisions for others and we always tested each refoamed speaker as part of our standard procedure. We always used the 20-20.000 Hertz signal for woofers, since small woofers in particular may significantly deviate towards the high spectrum. Obviously, the 20-20.000 Hertz signal also allows you to test the entire speaker sound range. See also 3 above.
Do you have further questions? Audiofriends has 14 years of experience, so please feel free to ask us anything you want to know.

9. How much time does a repair take?
It depends on your skills, accuracy, etc. And, for instance, whether or not the old foam on the speaker can easily be removed. An 8 inch (20cm diameter) Bose 301 will, for each speaker, take about an hour for a beginner. A Bose 901 takes approximately 30 minutes for each speaker; a big 15 inch special Tannoy loudspeaker will take 2 hours.

10a. What about payment and delivery?
If you buy via mail:
If you mail us the sizes and the brand of the speaker and the type of casing, we will send you a sales quote, which will list clearly the foam or rubber surrounds /  rim(s) we can offer you, as well as the total price. We will provide you with the details of our bank account.
If you accept a quote, you can transfer the money to our account. After we receive payment, we try to ship your order as soon as possible. Please keep in mind that an online money transfer does not mean that the amount is immediately credited to our account.
If you buy in our webshop, or on eBay, most of the time, you immediately pay your product.
We try to ship your order before mail collection as much as we can. In the fastest case, the money is credited to our account the same day you transferred it. This is possible in case you have the same bank. At Audiofriends, the processing time normally amounts to 0-3 days.
10b. Why does Audiofriends not ship the goods using cash on delivery?
The option of cash on delivery does not offer more reliability to our customers (for instance, I could put a sausage in the package). However, it makes a big difference to me. People sometimes change their mind and furthermore, cash on delivery shipments are very expensive at PostNL.

11. How does Audiofriends ship?
Audiofriends ships in a sturdy cardboard box or, if Audiofriends seems it safe, in an airmail envelope.

12. Who, what and where is Audiofriends?
Audiofriends was founded in 1998 as a website for and by hi-fi hobbyists. The founder, Fred Buist, has an M.T.S. (technical secondary school) degree and worked as a draughtsman, amongst others.
Fred developed a lot of do-it-yourself hi-fi and published manuals on Other ‘Audiofriends’ have found their way to the website and contribute nice descriptions and manuals.
Fred started to work with hi-fi and with foam surround rims before the Internet era, long before the existence of Audiofriends. It goes without saying that a background as a proven hi-fi amateur also leaves its marks on the sale of loudspeaker parts. Currently, there is a small team behind Audiofriends.
Audiofriends has developed many things and has tested many loudspeaker parts. Based on 14 years of experience in the field of repairing worn-out loudspeaker surround rims.
13. Will the new foam surrounds also wear out?
The foam rubber surround rims we offer here are of a high quality with more reliable fillings and materials, making them very durable. The original surround rims were composed differently and were less durable as a result. The lifespan depends, amongst others, on the humidity, smoke, sunlight (UV radiation), heat etc. The worst place for foam surround rims is the parcel shelf of a car.
Audiofriends examined the products of its many suppliers. The foam surround rims of Audiofriends will last till 10 to 35 years, depending on the circumstances. Old rubber surround rims may harden or lose their original shape. The surround rims we supply should at least last 40 years, depending on the circumstances.
14. Can I repair only one side of my speakers?
This is possible, of course, but it might not be a wise course of action:
  • The other speaker will soon be worn out as well.
  • If one side has a new surround rim, and the old surround rim on the other side is more or less decomposed, the sound will be uneven, which may be audible.
However, in special circumstances, it is possible that one side of the loudspeaker pair has always been exposed to the sun, while the other side was placed in a dark corner of the room.
15. You want to know more about the dustcap story.
Normally, it is not necessary to remove the dust cap. For more information click on ‘your refoam description’. In exceptional cases, for instance, in case of units from the PA that have been used heavily for an extended period of time, or units with a heavy cone and a supple centre ring, it may be necessary to centre the cone in another way. You can simply check this by keeping the unit first down with the magnet pointing downwards and then turn it upside with the magnet pointing upwards. If the cone then ‘falls’, there is a rough clearance maximum. For an 8 inch speaker, the clearance should be about 2 mm, for a 10 inch one it would be 2.5 mm and for a 12 inch one it would be 3 mm. The centre ring may not be completely flat, but still retain its sturdiness.
For such cases, please contact me and I will send you the ‘refoaming tips’. In such an exceptional situation (about 0.5% of the cases), the cap can be removed. In my opinion, it is better to use the original cap for such a revision. This is important, especially for smaller speakers which produce more middle and high tones. It is certainly not the point to cut the caps off, to centre the cone and to install another cap afterwards. There are several reasons for this:
  1. A part of the old cap remains in place, which renders the cone heavier and slower. It also reduces the performance.

  2. The cap plays an important role, especially in case of smaller units, for the production of higher frequencies. Installing a larger cap (which has to be larger in order to cover the remainders of the old cap) affects the production of these higher frequencies. The following is a direct quote from the Dutch edition of the book ‘‘The Loudspeaker Design Cookbook’ by Vance Dickason. This is not just any book, but a Bible among books used by loudspeaker designers:

    --- A dustcap has also influence on the of the high frequencies. ---

  3. The new cap is not an original one and will, in most cases, be made of a standard material, from which the whole product line of dust caps has been produced. This may also affect sound production. (see above).
You can probably imagine why, both from a visual and a sound-technical point of view, it is better to leave the dust cap in place and to use our way of refoaming. There are various types of dust caps:
  • plastic
  • paper
  • felt
  • fine meshed fabric
  • aluminium
  • air permeable fabric
For the last type, the air-permeable fabric, construction plays an important role. If left uncorrected, there may be an accumulation of compressed air behind the cap. This results in a distortion of the sound. Different manufacturers have found different solutions to this problem. For instance, by making ventilation holes in the voice coil holder, in the pole core, or simply by making the dust cap air-permeable. The installation of just any cap ‘that fits’ can cause unexpected problems. In a case like this, Audiofriends tries to deliver a dust cap that is most similar to the original one. The best quality for the same price!
16. Do you also have special sizes?
Many expensive loudspeaker brands have used deviating sizes. For JBL, Infinity, Tannoy, Dynaudio, Cerwin Verga, Acoustic Research, KEF, Dahlquist, etc., only Audiofriends has surround rims that have been specifically produced for these units.
Therefore, these surround rims are not standard surround rims for deviating sizes, but surround rims with the original fitting form or genuine:
among others:
Dynaudio 8”DYN-2 und 11”DYN-2
KEF 3”KF, 10“KF
Tannoy 10’TAN, 12”TAN und 15”TAN
8“VF, 5“RF-2, 3,5“LAB
The aforementioned surrounds not only have the original size, but also the original pliability / flexibility.
Audiofriends innovates and designs surrounds in 3D
Figure: Commission Audiofriends with the manufacture of surrounds using 3D technology.

17. The surround rim sizes deviate.
A somewhat different size doesn’t have to be a failure. If, although we’re very accurate, you got a different surround, you can of course trade them in at no costs..
18. Are the manuals from Audiofriends?
All shown manuals, drawings, pictures, test signals, refoam method, are made by Audiofriends. Some pictures, etc. are from customers, they are all placed with their clear approval.
19. You want to know more about the type of glue we use.
The glue is a part of the revision. For instance, if you use Bisontix or Bisonkit, you run the risk of the glue affecting the foam immediately or at a later stage. More importantly, not all glues have the properties this special glue has. The special glue resembles wood glue, but it is markedly different.
Both are water-based glues, but wood glue becomes a lot harder and shrinks a lot more. Both characteristics make wood glue unsuitable for this purpose. The glue needs to follow the movements of the foam. Glue that is too hard will come off. If the glue shrinks too much on the joints between, for instance, cone and foam, it will pull the foam towards it.
The glue we provide is also very strong, a lot stronger than the form itself and it is a water-based glue. This glue is especially made for hanging surround rims, dust caps, etc. and it is used by virtually all professional refoaming companies.
Audiofriends has conducted extensive tests with various types of glue on difficult surfaces.
Naturally, we also tested the glue on loudspeaker units. In this case, a unit of the most sold speaker in the world, the Bose 301.
Depending on the circumstances, it takes approximately 30 minutes for the glue to become strong enough to be handled safely.
After about 24 hours, the glue is so strong that the foam rips apart in case of heavy-handed removal. The glue will not come off. After extensive tests, glue B was chosen from a selection of four different glues.
The following has been taken into consideration (among other things):
1. Process ability
2. Force on various materials after 30 minutes of drying
3. Force on various materials after 24 hours of drying

The glue we use at Audiofriends also adheres very well to plastic. In this case too, the glue is actually stronger than the foam itself.

20. Do you guarantee the repair?
‘Do you guarantee that I will be able to perform the repair?’ Unfortunately, we cannot guarantee this. After a day of overtime until 21:00h, ‘quickly repairing the speakers’ would be unwise. Take your time, and if you encounter something you are not sure about, please do not hesitate to contact us. Read the manuals carefully. Repairs are at your own risk.

21. Why do you ask for the dimensions of the speaker?
Formerly, many series of loudspeakers were produced over a long period of time. Back then (and even to this day), so-called ‘batch variations’ often occurred. For instance, during production, suppliers were sometimes unable to follow through with their orders and therefore, parts were ordered from multiple suppliers.
These parts often differed slightly. It also often occurred that, during production, a slightly different unit was installed. This was done for purposes of improvement or because of the unavailability of previous units. It also occurred that one side of the speaker came from a different batch than the other side.
Even in the case that someone else would give me the dimensions, this not the optimal solution. You may end up paying for someone else’s mistakes.
Other configurations are usually not all that ‘difficult.’ There is a limited variety of surround rims and things have a tendency ‘to fit easily.’ Click here to learn about taking measurements properly. In order to be extra precise we advise you to cross-measure twice.

22. In which cases do I not have to measure my speakers?
We know the sizes of many common speaker types. If the original speaker is still in the loudspeaker casing, in most cases, you do not have to measure the speaker.
23. Do you also refoam for others?
I revised many loudspeakers, of all types and sizes. Therefore, I dare call myself an ‘experienced expert’. I already performed refoaming jobs long before the Internet era. However, due to our website’s success, I no longer have the time to do this and we completely committed ourselves to the supply of loudspeaker parts, including foam surround rims.
If you want to have your speakers revised, we can refer you to a specialist upon request.
24a. Running in your speakers?
New store-bought speakers need to be run in. The same is true in case the hanging surround rims have been replaces. It is best to let the loudspeakers only play quietly for a week. You will notice that, over time, the surround rims become more flexible, the low spectrum deepens and that the music has a fuller sound.
Because of this speakers will naturally be run in through use. We recommend not taxing the loudspeakers too heavily during the first 48 hours.  If, afterwards, you want to perform an accelerated run-in, you can do so here.
24b. Can I also perform an accelerated run-in of the speakers?
This is possible.  To this end, Audiofriends has a run-in signal (for bass loudspeakers). You can run in your repaired loudspeaker with sweep van 20-40 Hz:
  1. Position the speakers opposite one another.
  2. Set one speaker to normal + on + and the other - on - .
  3. Reverse the other speaker appropriately:  + on - and - on +.
  4. Download the sweep.
  5. Burn the sweep onto a CD.
  6. Arrange the same setup as below.
  7. Play the cd on ‘repeat’.
  8. NOTE: Watch the cone of the bass loudspeaker carefully when you turn up the volume.
  9. If done right, you should hardly hear it.
  10. Run in with a lower volume during the first 24 hours.
  11. NOTE: Monitor the amplifier carefully to make sure it does not overheat.
  12. Slightly raise the volume after 24 hours.
  13. Let the speakers play for approximately 3-7 days.

© Copyright 2012 – Audiofriends – Fred Buist – All Right Reserved
(PS:  All items are to determine to copyright provided with an official date stamp.)